Bordetella Pertussis and Whooping Cough

7/27/2019 Bordetella Pertussis and Whooping Cough

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Bordetella pertussis and Whooping Cough

Bordetella pertussis

Whooping cough (pertussis) is caused by the bacteriumBordetella pertussis,B.

pertussis is a very small Gram-negative aerobic coccobacillus that appears singly orin pairs. Its metabolism is respiratory, never fermentative, and taxonomically,

Bordetella is placed among the "Gram-negative Aerobic Rods and Cocci" in Bergey's

Manual.Bordetella is not assigned to any family. The bacteria are nutritionally

fastidious and are usually cultivated on rich media supplemented with blood. They

can be grown in synthetic medium, however, which contains buffer, salts, an amino

acid energy source, and growth factors such as nicotinamide (for which there is a

strict requirement). Even on blood agar the organism grows slowly and requires 3-6

days to form pinpoint colonies.

Bordetella pertussis colonizes the cilia of the mammalian respiratory epithelium

(Figure 1). Generally, it is thought thatB. pertussis does not invade the tissues, butsome recent work has shown the bacterium in alveolar macrophages. The bacterium is

a pathogen for humans and possibly for higher primates, and no other reservoir is

known. Whooping cough is a relatively mild disease in adults but has a significant

mortality rate in infants. Until immunization was introduced in the 1930s, whooping

cough was one of the most frequent and severe diseases of infants in the United

States.

Pathogenesis

The disease pertussis has two stages. The first stage, colonization, is an upper

respiratory disease with fever, malaise and coughing, which increases in intensityover about a 10-day period. During this stage the organism can be recovered in large

numbers from pharyngeal cultures, and the severity and duration of the disease can be

reduced by antimicrobial treatment. Adherence mechanisms ofB. pertussis involve a

"filamentous hemagglutinin" (FHA), which is a fimbrial-like structure on the

bacterial surface, and cell-bound pertussis toxin (PTx). Short range effects of

soluble toxins play a role as well in invasion during the colonization stage.

The second or toxemic stage of pertussis follows relatively nonspecific symptoms of

the colonizaton stage. It begins gradually with prolonged and paroxysmal coughing

that often ends in a characteristic inspiratory gasp (whoop). To hear the characteristicsound of whooping cough clickwhoop.wav (whoop.wav is copyright of Dr Doug

Jenkinson, Nottingham, England. www.whoopingcough.net). During the second

stage,B. pertussis can rarely be recovered, and antimicrobial agents have no effect on

the progress of the disease. As described below, this stage is mediated by a variety of

soluble toxins.

Colonization

Studies ofB. pertussis and its adhesins have focused on cultured mammalian cells that

lack most of the features of ciliated epithelial cells. However, some generalities have

been drawn. The two most important colonization factors are the filamentoushemagglutinin (FHA) and the pertussis toxin (PTx). Filamentous hemagglutinin is a
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large (220 kDa) protein that forms filamentous structures on the cell surface. FHA

binds to galactose residues on a sulfated glycolipid called sulfatide which is very

common on the surface of ciliated cells. Mutations in the FHA structural gene reduce

the ability of the organism to colonize, and antibodies against FHA provide protection

against infection. However, it is unlikely that FHA is the only adhesin involved in

colonization. The structural gene for FHA has been cloned and expressed in E. coli,raising the possibility of its production for use in a component vaccine.

One of the toxins ofB. pertussis, the pertussis toxin (PTx), is also involved in

adherence to the tracheal epithelium. Pertussis toxin is a 105 kDa protein composed of

six subunits: S1, S2, S3, (2)S4, and S5. The toxin is both secreted into the

extracellular fluid and cell bound. Some components of the cell-bound toxin (S2 and

S3) function as adhesins, and appear to bind the bacteria to host cells. S2 and S3

utilize different receptors on host cells. S2 binds specifically to a glycolipid called

lactosylceramide, which is found primarily on the ciliated epithelial cells. S3 binds to

a glycoprotein found mainly on phagocytic cells.

The S1 subunit of pertussis toxin is the A component with ADP ribosylating activity,

and the function of S2 and S3 is presumed to be involved in binding the intact

(extracellular) toxin to its target cell surface. Antibodies against PTx components

prevent colonization of ciliated cells by the bacteria and provide effective protection

against infection. Thus, pertussis toxin is clearly an important virulence factor in the

initial colonization stage of the infection.

Since the S3 subunit of pertussis toxin is able to bind to the surface of phagocytes,

and since FHA will attach to integrin CR3 on phagocyte surfaces (the receptor for

complement C3b), it has been speculated that the bacterium might bind preferentially

to phagocytes in order to facilitate its own engulfment. The role of such self-initiated

phagocytosis is not clear. Bacteria taken up by this abnormal route may avoid

stimulating the oxidative burst that normally accompanies phagocytic uptake of

bacterial cells which are opsonized by antibodies or complement C3b. Once inside of

cells the bacteria might utilize other toxins (i.e. adenylate cyclase toxin) to

compromise the bactericidal activities of phagocytes. In any case, there is some

evidence thatBordetella pertussis can use this mechanism to get into and to persist in

phagocytes as an intracellular parasite. IfB. pertussis is an intracellular parasite it

would explain why immunity to pertussis correlates better with the presence of

specific cytotoxic T cells than it does with the presence of antibodies to bacterial

products.

B. pertussis produces at least two other types of adhesins, two types of fimbriae and a

nonfimbrial surface protein called pertactin, but their role in adherence and

pathogenesis is not well established.

Toxins Produced byB. pertussis

B. pertussis produces a variety of substances with toxic activity in the class of

exotoxins and endotoxins.

It secretes its own invasive adenylate cyclase which enters mammalian cells

(Bacillus anthracis produces a similar enzyme, EF). This toxin acts locally to reduce

phagocytic activity and probably helps the organism initiate infection. This toxin is a


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45 kDa protein that may be cell-associated or released into the environment. Mutants

ofB. pertussis in the adenylate cyclase gene have reduced virulence in mouse models.

The organisms can still colonize but cannot produce the lethal disease. The adenylate

cyclase toxin is a single polypeptide with an enzymatic domain (i.e., adenylate

cyclase activity) and a binding domain that will attach to host cell surfaces. The

adenylate cyclase was originally identified as a hemolysin because it will lyse redblood cells. In fact, it is responsible for hemolytic zones around colonies of

Bordetella pertussis growing on blood agar. Probably it inserts into the erythrocyte

membrane which causes hemolysis. An interesting feature of the adenylate cyclase

toxin is that it is active only in the presence of a eukaryotic regulatory molecule called

calmodulin, which up-regulates the activity of the eukaryotic adenylate cyclase. The

adenylate cyclase toxin is only active in the eukaryotic cell since no similar regulatory

molecule exists in procaryotes. Thus, the molecule seems to have evolved specifically

to parasitize eukaryotic cells. Anthrax EF (edema factor) is also a calmodulin-

dependent adenylate cyclase.

It produces a highly lethal toxin (formerly called dermonecrotic toxin) which causesinflammation and local necrosis adjacent to sites whereB. pertussis is located. The

lethal toxin is a 102 kDa protein composed of four subunits, two with a mw of 24kDa

and two with mw of 30 kDa. It causes necrotic skin lesions when low doses are

injected subcutaneosly in mice and is lethal in high doses. The role of the toxin in

whooping cough is not known.

It produces a substance called the tracheal cytotoxin which is toxic for ciliated

respiratory epithelium and which will stop the ciliated cells from beating. This

substance is not a classic bacterial exotoxin since it is not composed of protein. The

tracheal cytotoxin is a peptidoglycan fragment, which appears in the extracellular

fluid where the bacteria are actively growing. The toxin kills ciliated cells and causes

their extrusion from the mucosa. It also stimulates release of cytokine IL-1, and so

causes fever.

It produces the pertussis toxin, PTx, a protein that mediates both the colonization

and toxemic stages of the disease. PTx is a two component, A+B bacterial exotoxin.

The A subunit (S1) is an ADP ribosyl transferase. The B component, composed of

five polypeptide subunits (S2 through S5), binds to specific carbohydrates on cell

surfaces. The role of PTx in invasion has already been discussed. PTx is transported

from the site of growth of the Bordetella to various susceptible cells and tissues of the

host. Following binding of the B component to host cells, the A subunit is insertedthrough the membrane and released into the cytoplasm in a mechanism of direct entry.

The A subunit gains enzymatic activity and transfers the ADP ribosyl moiety of NAD

to the membrane-bound regulatory protein Gi that normally inhibits the eukaryotic

adenylate cyclase. The Gi protein is inactivated and cannot perform its normal

function to inhibit adenylate cyclase. The conversion of ATP to cyclic AMP cannot be

stopped and intracellular levels of cAMP increase. This has the effect to disrupt

cellular function, and in the case of phagocytes, to decrease their phagocytic activities

such as chemotaxis, engulfment, the oxidative burst, and bacteridcidal killing.

Systemic effects of the toxin include lymphocytosis and alteration of hormonal

activities that are regulated by cAMP, such as increased insulin production (resulting

in hypoglycemia) and increased sensitivity to histamine (resulting in increasedcapillary permeability, hypotension and shock). PTx also affects the immune system


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in experimental animals. B cells and T cells that leave the lymphatics show an

inability to return. This alters both AMI and CMI responses and may explain the high

freqency of secondary infections that accompany pertussis (the most frequent

secondary infections during whooping cough are pneumomia and otitis media).

Although the effects of the pertussis toxin are dependent on ADP ribosylation, it hasbeen shown that mere binding of the B oligomer can elicit a response on the cell

surface such as lymphocyte mitogenicity, platelet activation, and production of insulin

effects.

The pertussis toxin gene has been cloned and sequenced and the subunits expressed in

E. coli. The toxin can be inactivated and converted to toxoid for use in component

vaccines.

Comparison between cholera toxin and pertussis toxin (ptx) in their ability to interfere with the

regulation of the eukaryotic adenylate cyclase complex.

Normal regulation of adenylate cyclase activity in mammalian cells. Adenylate cyclase (AC) isactivated normally by a stimulatory regulatory protein (Gs) and guanosine triphosphate (GTP);

however the activation is normally brief because an inhibitory regulatory protein (Gi) hydrolyzes theGTP.

Adenylate cyclase activated by cholera toxin The cholera toxin A1 fragment catalyzes the attachmentof ADP-Ribose (ADPR to the regulatory protein Gs, forming Gs-ADPR from which GTP cannot be

hydrolyzed. Since GTP hydrolysis is the event that inactivates adenylate cyclase (AC), the enzyme

remains continually activated.

Adenylate cyclase activated by pertussis toxin (The pertussis A subunit transfers the ADP ribosyl

moiety of NAD to the membrane-bound regulatory protein Gi that normally inhibits the eukaryoticadenylate cyclase. The Gi protein is inactivated and cannot perform its normal function to inhibitadenylate cyclase. The conversion of ATP to cyclic AMP cannot be stopped.

Lipopolysaccharide. As a Gram-negative bacteriumBordetella pertussis possesses

lipopolysaccharide (endotoxin) in its outer membrane, but its LPS is unusual. It is

heterogeneous, with two major forms differing in the phosphate content of the lipid

moiety. The alternative form of Lipid A is designated Lipid X. The unfractionated

material elicits the usual effects of LPS (i.e., induction of IL-1, activation of

complement, fever, hypotension, etc.), but the distribution of those activities is

different in the two forms of LPS. For example, Lipid X, but not Lipid A, is

pyrogenic, and its O-side chain is a very powerful immune adjuvant. Furthermore,

Bordetella LPS is more potent in the limulus assay than LPS from other Gram-

negative bacteria, so it is not reliable to apply knowledge of the biological activity of

LPS in theEnterobacteriaceae to the LPS ofBordetella. The role of this unusual LPS

in the pathogenesis of whooping cough has not been investigated.

Regulation of Virulence Factors inB. pertussis

The production of virulence factors inB. pertussis is regulated in several different

ways. Expression of virulence factors is regulated by the bvg operon.

First, the organisms undergo an event called phase variation resulting in the loss of

most virulence factors and some undefined outer membrane proteins. Phase variationhas been shown to occur at a genetic frequency of 10-4 - 10-6 generations and results


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from a specific DNA frame shift that comes about after the insertion of a single

nucleotide into the bvg (also known as vir) operon.

A similar process called phenotypic modulation, occurs in response to environmental

signals such as temperature or chemical content, and is reversible. This is an adaptive

process mediated by the products of the bvg operon, and is an example of a two-component environmental-sensing (regulatory) system used by other bacteria. The

expression of these regulatory proteins is itself regulated by environmental signals,

such that entry into a host might induce components required for survival and

production of disease.

The Whooping Cough Vaccine

The development of the whooping cough vaccine in the 1950s has made whooping

cough an uncommon disease in developed countries. In countries where the vaccine is

not used whooping cough is an important cause of mortality in children, with an

estimated 51,000,000 cases and 600,000 deaths annually.

Historically, the whooping cough vaccine has been administered as a merthiolate-

killed bacterial cell suspension which is part of the DTP vaccine (The P in DTP stands

for Pertussis cells). Unfortunately, about 20% of the children that receive the whole

cell vaccine experience mild side effects. About 0.1% of infants experience

convulsions soon after receiving the vaccine and in a very small number of cases (1 in

150,000?) severe or irreversible brain damage may occur. In the absence of the

disease in an immune population, parents have begun to wonder if the risk of

vaccinating children outweighs the risk of the disease, and the value of the whole cell

vaccine has been questioned.

Several new acellular vaccines have been developed from purified components ofB.

pertussis. Demonstration of the protective effects of anti-PTx and anti-FHA

antibodies in the mouse model, focused vaccine production on combinations of

inactivated pertussis toxin (toxoid) and filamentous hemagglutinin. Multicomponent

acellular vaccines containing combinations of pertussis toxoid, filamentous

hemagglutinin, pertactin, and the two types of fimbriae, are now being used in several

countries including the U.S. The new vaccine, known as acellular pertussis has

fewer side effects than the whole cell vaccine and is currently recommended for use

under the conditions described below.

For decades, the pertussis vaccine has been given in combination with vaccinesagainst diphtheria and tetanus. The combination is known as the DTP vaccine.

Recently, infants have been able to receive a vaccine that combines the DTP vaccine

with the vaccine againstHaemophilus influenzae type b meningitis (Hib). This

vaccine is called DTPH. The diphtheria-tetanus-pertussis vaccine using acellular

pertussis is known as DTaP. The diphtheria-tetanus-pertussis vaccination is given in

five doses: at 2, 4, 6, 12-18 months and 4-6 years of age. Previously, DTaP had been

recommended only for the fourth and fifth doses. Following FDA licensure of DTaP

for infants, the Advisory Committee on Immunization Practices of the United States

Public Health Service now recommends that DTaP be used for the first four doses and

that DTaP still be used for the fourth and fifth doses for children who received DTP in

their first three doses. The Committee is awaiting study results before making a

recommendation for the fifth dose for children who now will receive DTaP in their


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first four doses. The recommendation still permits the use of DTP and DTPH--the

combination that includes the vaccine againstHaemophilus influenzae type b

meningitis.

Whooping Cough In Wisconsin 2004

There were more than 4,800 cases of whooping cough were reported in Wisconsin in

2004, an increase of more than 690 percent over the previoust year, when there were

716. In the mid-1980s, when whooping cough outbreaks were considered particularly

bad, there were 400 to 500 reported cases per year.

Dane County reported over 150 cases. The Public Health Department of the City of

Madison saw over 100 cases in 2004, even though the disease is undoubtedly under-

reported. The University Health Services saw a rise in incidence on the UW campus.

Last semester UHS confirmed several student cases each week, with several

additional unconfirmed occurrences.

Since the development of the pertussis vaccine, the incidence of whooping cough in

the U.S. steadily declined until the past two decades when it began to rise. According

to the Center for Disease Control, Wisconsin currently ranks second in the nation for

disease incidence rate at 27.7 cases per 100,000 individuals.

It is difficult to draw conclusions by comparing the 2004 outbreak with those in past

years. The increase in whooping cough numbers can partially be explained by new

testing procedures that became available last year. The new test is quicker and more

sensitive than previous tests, and physicians are putting more emphasis on diagnosing

the illness.

Also, whooping cough infections tend to run on a 2-5 year cycle, and 2004 could be a

high point in the cycle.

Like flu viruses, the bacterium is highly contagious and tends to pass quickly from

person to person through coughing and sneezing. If increasing numbers of individuals

have the illness, then the risk of infection increases in the general population.

Many young children are vaccinated against whooping cough with the pertussis

vaccine. However, the vaccine is only approved for children under seven years of age.

Antibody-mediated immunity wanes in approximately ten years, leaving olderindividuals more susceptible to the disease. Adults get infected, often to a lesser

degree, but they are still able to spread the disease to unimmunized children.

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Figure 1. Colonization of tracheal epithelial cells byBordetella pertussis

Bordetella pertussis, the agent of pertussis or whooping cough. Gram stain. (CDC)

http://en.wikipedia.org/wiki/Bordetella

Bordetella is a genus of small (0.2 - 0.7 m), Gram-negative coccobacilli of the

phylumproteobacteria.Bordetella species, with the exception ofB. petrii, are obligate

aerobes as well as highly fastidious, or difficult to culture. Three species are human

pathogens (B. pertussis,B. parapertussis,B. bronchiseptica); one of these (B.

bronchiseptica) is also motile.[1]

B. pertussis and occasionallyB. parapertussis causepertussis or whooping cough in

humans, and someB. parapertussis strains can colonise sheep.B. bronchiseptica

rarely infects healthy humans though disease in immunocompromised patients has

been reported.[2]B. bronchiseptica causes several diseases in other mammals,

including kennel cough and atrophic rhinitisin dogs and pigs, respectively. Other

members of the genus cause similar diseases in other mammals, and in birds (B.

hinzii,B. avium).

TheBordetella genus is named afterJules Bordet.
http://en.wikipedia.org/wiki/Genushttp://en.wikipedia.org/wiki/Gram-negativehttp://en.wikipedia.org/wiki/Proteobacteriahttp://en.wikipedia.org/wiki/Proteobacteriahttp://en.wikipedia.org/w/index.php?title=B._petrii&action=edit&redlink=1http://en.wikipedia.org/wiki/Obligate_aerobehttp://en.wikipedia.org/wiki/Obligate_aerobehttp://en.wikipedia.org/wiki/Pathogenhttp://en.wikipedia.org/wiki/Bordetella_pertussishttp://en.wikipedia.org/wiki/Bordetella_parapertussishttp://en.wikipedia.org/wiki/Bordetella_parapertussishttp://en.wikipedia.org/wiki/Bordetella_bronchisepticahttp://en.wikipedia.org/wiki/Motilehttp://en.wikipedia.org/wiki/Motilehttp://en.wikipedia.org/wiki/Bordetella#cite_note-Sherris-0http://en.wikipedia.org/wiki/Pertussishttp://en.wikipedia.org/wiki/Pertussishttp://en.wikipedia.org/wiki/Bordetella#cite_note-Bauwens_1992-1http://en.wikipedia.org/wiki/Kennel_coughhttp://en.wikipedia.org/wiki/Atrophic_rhinitishttp://en.wikipedia.org/wiki/Atrophic_rhinitishttp://en.wikipedia.org/wiki/Jules_Bordethttp://en.wikipedia.org/wiki/Genushttp://en.wikipedia.org/wiki/Gram-negativehttp://en.wikipedia.org/wiki/Proteobacteriahttp://en.wikipedia.org/w/index.php?title=B._petrii&action=edit&redlink=1http://en.wikipedia.org/wiki/Obligate_aerobehttp://en.wikipedia.org/wiki/Obligate_aerobehttp://en.wikipedia.org/wiki/Pathogenhttp://en.wikipedia.org/wiki/Bordetella_pertussishttp://en.wikipedia.org/wiki/Bordetella_parapertussishttp://en.wikipedia.org/wiki/Bordetella_bronchisepticahttp://en.wikipedia.org/wiki/Motilehttp://en.wikipedia.org/wiki/Bordetella#cite_note-Sherris-0http://en.wikipedia.org/wiki/Pertussishttp://en.wikipedia.org/wiki/Bordetella#cite_note-Bauwens_1992-1http://en.wikipedia.org/wiki/Kennel_coughhttp://en.wikipedia.org/wiki/Atrophic_rhinitishttp://en.wikipedia.org/wiki/Jules_Bordet


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[edit] Pathogenesis ofBordetella infections

The most thoroughly studied of theBordetella species areB. bronchiseptica,B.

pertussis andB. parapertussis and the pathogenesis of respiratory disease caused by

these bacteria has been reviewed[3].[4][5] Transmission occurs by direct contact, or via

respiratory aerosol droplets, or fomites. Bacteria initially adhere to ciliatedepithelialcells in the nasopharynx and this interaction with epithelial cells is mediated by a

series of protein adhesins. These includefilamentous haemaglutinin,pertactin,

fimbriae, andpertussis toxin (though expression of pertussis toxin is unique toB.

pertussis). As well as assisting in adherence to epithelial cells, some of these are also

involved in attachment to immune effector cells.

The initial catarrhal phase of infection produces symptoms similar to those of the

common cold and during this period, large numbers of bacteria can be recovered from

the pharynx. Thereafter the bacteria proliferate and spread further into the respiratory

tract, where the secretion of toxins causes ciliostasis and facilitates the entry of

bacteria to tracheal/bronchial ciliated cells. One of the first toxins to be expressed is

tracheal cytotoxinwhich is a disaccharide-tetrapeptide derived frompeptidoglycan.

Unlike most otherBordetella toxins, tracheal cytotoxin is expressed constitutively,

being a normal product of the breakdown of the bacterial cell wall. Other bacteria

recycle this molecule back into the cytoplasm, but inBordetella andNeisseria

gonorrhoeae it is released into the environment. Tracheal cytotoxin itself is able to

reproduce paralysis of the ciliary escalator, inhibition of DNA synthesis in epithelial

cells and ultimately killing of the same. One of the most important of the regulated

toxins is adenylate cyclase toxin, which aids in the evasion ofinnate immunity. The

toxin is delivered to phagocytic immune cells upon contact.[6] Immune cell functions

are then inhibited in part by the resulting accumulation ofcyclic AMP. Recentlydiscovered activities of adenylate cyclase toxin, including transmembrane pore

formation and stimulation ofcalcium influx, may also contribute to the intoxication of

phagocytes.[7][8]

[edit] making of virulence factor expression in Bordetella

The expression of manyBordetella adhesins and toxins is controlled by the two-

component regulatory system BvgAS.[4][5] Much of what is known about this

regulatory system is based on work withB. bronchiseptica but BvgAS is present inB.

pertussis,B. parapertussis andB. bronchiseptica and is responsible for phase

variation orphenotypic modulation.

BvgS is aplasma membrane-bound sensorkinase which responds to stimulation by

phosphorylating a cytoplasmichelix-turn-helix-containing protein, BvgA. When

phosphorylated, BvgA has increased affinity for specific binding sites in Bvg-

activated promoter sequences and is able to promote transcription in in vitro assays.[9]

[10]

Most of the toxins and adhesins under BvgAS control are expressed under Bvg+

conditions (high BvgA-Pi concentration). But there are also genes expressed solely in

the Bvg- state, most notably the flagellin geneflaA.[11]The regulation of Bvg repressed

genes is mediated by the product of a 624-bp open reading framedownstream ofbvgA, the so-called Bvg-activated repressor protein, BvgR.[12] BvgR binds to a
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consensus sequence present within the coding sequences of at least some Bvg-

repressed genes. Binding of this protein to the consensus sequence represses gene

expression by reducing transcription.[13]

It is not known what the physiological signals for BvgS are, but in vitro BvgAS can

be inactivated by millimolar concentrations of magnesium sulfate or nicotinic acid, orby reduction of the incubation temperature to 26C.[14][15] !

The identification of a specific point mutation in the bvgS gene which locksB.

bronchiseptica in an intermediate Bvg phase revealed a class of BvgAS-regulated

genes that are exclusively transcribed under intermediate concentrations of BvgA-Pi.

This intermediate (Bvgi) phenotype can be reproduced in wild-typeB. bronchiseptica

by growth of the bacteria in medium containing intermediate concentrations of the

BvgAS modulator, nicotinic acid. In these conditions some, but not all of the

virulence factors associated with the Bvg+ phase are expressed suggesting that this

two component regulatory system can give rise to a continuum of phenotypic states in

response to the environment.

http://www.uea.ac.uk/cap/carbohydrate/CCCPeople/Corin/welcome.htm

Bordetella pertussis, is the causative agent of whooping cough (Allen, et al., 1998). The French

physician De Baillou first described the organism in 1640 (Cone, 1970) (see Figure 1.0).

Figure 1 The structure ofBordetella pertussis and its components (Koenig and Finger 2001)

1. Pathogenesis

Bordetella pertussis colonises the cilia of the mammalian respiratory epithelium; and is non-invasive

(Henderson, et al., 1999). The bacterium is a pathogen for humans and possibly for higher primates, no

other reservoirs are known. Whooping cough is a relatively mild disease in adults, but has a significant
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mortality rate in infants. Until immunisation was introduced in the 1930s, whooping cough was one of

the most frequent and severe diseases of infants in the United States.

After an incubation period of 1-3 weeks, whooping cough begins with colonisation of the upper

respiratory disease causing fever, malaise and coughing, which increases in intensity over about a 10-dayperiod. During this stage the organism can be recovered in large numbers from pharyngeal cultures, and

the severity and duration of the disease can be reduced by anti-microbial treatment.

The second or toxemic stage of the disease begins gradually with prolonged and paroxysmal coughing

that often ends in a characteristic inspiratory gasp (whoop). During the second stage of the disease B.

pertussis can rarely be recovered, and anti-microbial agents have no effect. Complications include

central nervous system anoxia, cerebellar ataxia (Setta, et al, 1999), exhaustion and secondary

pneumonia due to invasion by other pathogens (Mims et al, 1995 a).

2. Colonisation

The two most important colonisation factors ofB. pertussis are the two secreted proteins: filamentous

hemagglutinin (FHA) and the pertussis toxin (PT).

2.1 Filamentous hemagglutinin

Filamentous hemagglutinin (FHA) is a large (220-kDa) protein that forms filamentous structures and

binds to galactose residues on a sulphated glycolipid called sulfatide, which appears on the surfaces of

ciliated cells. Mutations in the FHA structural gene reduce the ability of the organism to colonise, and

antibodies against FHA provide protection against infection. The structural gene for FHA has been

cloned and expressed inE. coli, raising the possibility of its production for use in a component vaccine(Todar, 1997).

2.2 The Pertussis toxin

One of the toxins ofB. pertussis, the pertussis toxin (PT), is also involved in adherence to the tracheal

epithelium. Pertussis toxin is a 105 kDa AB5 protein composed of five sub-units: S1-S5 (Locht, 2001).

The toxin is both and cell bound and secreted into the extracellular fluid. Some components of the cell-

bound toxin (S2 and S3), function as adhesins, and appear to bind the bacteria to host cells. S2 and S3

utilise different receptors on host cells. S2 binds specifically to a glycolipid called lactosylceramide,

which is found primarily on ciliated epithelial cells, while S3 binds to 2-6 linked sialic acid found mainly

on phagocytic cells (Mims, et al, 1995).

The 26-kDa S1 subunit of pertussis toxin is the A (active) component of the toxin with ADP ribosylating

activity, while the function of S2 and S3 is to bind the intact (extracellular) toxin to its target cell surface.

Antibodies against PT components prevent colonisation of ciliated cells by the bacteria and provide

effective protection against infection (Todar, 1997).

Since the S3 subunit of pertussis toxin is able to bind to the surface of phagocytes, and since FHA will

attach to integrin CR3 on phagocyte surfaces (the receptor for complement C3b), it has been speculated

that the bacterium might bind preferentially to phagocytes in order to facilitate its own engulfment. This

means the bacterium avoids stimulating the oxidative burst that normally accompanies phagocytic uptake

of bacterial cells and subsequently bacterial cell death (Todar, 1997).


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Once inside cells, the bacteria produce other toxins, such as the adenylate cyclase toxin, which

compromises the bacteriocidal activity of phagocytes. There is some evidence that Bordetella pertussis

can use this mechanism to enter, and to persist in phagocytes as an intracellular parasite. Therefore ifB.

pertussis is an intracellular parasite, it would explain why immunity to pertussis correlates better with the

presence of specific cytotoxic T cells than it does with the presence of antibodies to bacterial products(Todar, 1997).

B. pertussis produces at least two other types of adhesins, two types of fimbriae and a 69-kDa, non-

fimbrial, outer membrane protein called pertactin. Pertactin is produced by all virulent strains ofB.

pertussis and acts as a protective antigen (Edwards, 1993).

3. Toxins Produced byB. pertussis

3.1 The adenylate cyclase toxin

B. pertussis secretes its own invasive adenylate cyclase which enters mammalian cells and acts locally toreduce phagocytic activity by causing host cells to increase their cyclic AMP levels.

The C terminal domain of the adenylate cyclase toxin (ACT or CyaA) forms a small cation-selective

channel, and this channel probably delivers the N-terminal adenylate cyclase to the host cell cytoplasm

(Mims et al., 1995, Braun & Focareta 1991). The toxin is a 45-kDa single polypeptide with an enzymatic domain(which has adenylate cyclase activity) and a binding domain that will attach to host cell surfaces.

An interesting feature of the adenylate cyclase toxin is that, like Anthrax edema factor (EF) it is active only in thepresence of a eukaryotic regulatory molecule called calmodulin; which up-regulates the activity of the eukaryoticadenylate cyclase.

The adenylate cyclase toxin is only active in the eukaryotic cell since no similar regulatory molecule exists inprokaryotes. This molecule therefore seems to have evolved specifically to parasitize eukaryotic cells.

3.2 The dermonecrotic toxin (DNT)

B. Pertussis also produces a highly lethal 102-kDa toxin (formerly called dermonecrotic toxin, DNT), which iscomposed of four subunits, two with a molecular weight of 24-kDa and two with a molecular weight of 30-kDa. Thistoxin causes inflammation and local necrosis adjacent to sites where B. pertussis is located by activating Rhoproteins, which stimulate DNA synthesis, but block cell division. The dermonecrotic toxin is an example of abacterial toxin that activates the secondary messenger pathway. Like the cytotoxic necrotising factor (CNF) ofE.coli, DNT ofBordetella species activates Rho proteins by deamidation (Schmitt et al., 1999, Horiguchi and Oka,2001). It has also been reported that DNT inhibits elevation of alkaline phosphatase activity and reduces theaccumulation of type 1 collagen in an osteoblast-like cell line. This suggests that the toxin might impair the abilityof cells to differentiate (Pullingeret al., 1996).

3.3 The tracheal cytotoxin (TCT)

Tracheal cytotoxin, which is toxic for the ciliated respiratory epithelium, stops the ciliated cells from beating,destroying the ciliary escalator, which leads to the accumulation of mucus within the lower respiratory tract andhence the coughing.

TCT is not a classic bacterial exotoxin, since it is not composed of protein but is a 921-dalton peptidoglycanfragment, which appears in the extracellular fluid where the bacteria are actively growing. The toxin kills ciliatedcells and causes their extrusion from the mucosa. It also causes fever by stimulating the release of cytokine

interleukin-1 (IL-1).


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TCT also has a potent effect upon neutrophils, blocking chemotaxis and phagocytosis at sub-lethal concentrations.Only B. pertussisand N. gonorrhoeae possess this activity, but in the case ofN. gonorrhoeae TCT is thought toact on ciliary cells in the human fallopian tube.

3.4 The pertussis exotoxin (PT)

As previously mentioned, the two component, AB pertussis exotoxin, (PT) mediates both the colonisation andtoxemic stages of the disease. The A subunit (S1) is an ADP ribosyl transferase, and is responsible for the toxicityof PT, while the B component, composed of five polypeptide sub-units (S2-S5), binds to specific carbohydrates oncell surfaces and mediates the internalisation of the toxic S1 subunit (Nencioni et al, 1991). PT is transported fromthe site of growth of the Bordetella to various susceptible cells and tissues of the host.

Following binding of the B component to host cells, the A subunit is inserted through the membrane and releaseddirectly into the cytoplasm. The A subunit gains enzymatic activity via binding of GTP, and transfers the ADPribosyl moiety of NAD to the membrane-bound regulatory protein Gi, that normally inhibits the eukaryoticadenylate cyclase. Once the Gi protein has inactivated the conversion of ATP to cyclic AMP cannot be stoppedand intracellular levels of cAMP increase. This increase leads to the disruption of cellular functions, causing a

decrease in phagocytic activities such as chemotaxis, engulfment, the oxidative burst, and bactericidal killing(Figure 2).

Figure 2. Schematic representation of the mechanism of action of pertussis toxin (Rappuoli et al, 1991).

Systemic effects of the toxin include lymphocytosis and alteration of hormonal activities that are regulated bycAMP. Increased insulin production results in hypoglycaemia, while increased sensitivity to histamine results in

increased capillary permeability, hypotension and shock (Mims et al, 1997 b).

3.5 Lipopolysaccharide (LPS endotoxin)

The outer membranes of gram-negative bacteria (such as B. pertussis) are composed of lipopolysaccharides,proteins and phospholipids that are organised in a complex manner (Figure 3, see also Chapter 6). The outermembrane functions as a barrier to exclude harmful substances (such as gram stain); this accounts for theobservation that gram-negative bacteria are less affected by lysozyme and penicillin, as well as other antibiotics(Voet & Voet, 1995).


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Figure 3. Schematic representation of the inner and outer membranes ofE. coliK-12. Coloured ovals and

rectangles represent sugar residues, whereas circles represent polar headgroups of various lipids.

Effects of endotoxins on the immune system

Fever

Tissue inflammation and damage

Drop of blood pressure shock Multiple OrganFailure

Severe palpitation of heat

Activation of BGK-thrombose

Drop of blood vessel permeability

Formation of oedema, respiratorical

complications

The amphipathic lipopolysaccharide (LPS endotoxin) in theBordetella pertussis outer membrane (see

figure 1.3) is unusual. It is heterogeneous, with two major forms differing in the phosphate content of the

lipid moiety. The alternative form of Lipid A is designated Lipid X. The unfractionated material elicitsthe usual effects of LPS (i.e., induction of IL-1, activation of complement, fever, hypotension, etc.), but

the distribution of those activities is different in the two forms of LPS. Lipid X, but not Lipid A, is

pyrogenic, and its O-side chain is a very powerful immune adjuvant.Bordetella LPS is more potent in

the limulus assay (which measures endotoxin potency) than LPS from other Gram-negative bacteria, so i

is not reliable to apply knowledge of the biological activity of LPS in theEnterobacteriaceae to the LPS

ofBordetella.

Although the role of LPS in the pathogenesis of whooping cough has not been investigated fully, some

studies have indicated that biosynthesis of a full-length LPS molecule may be required for expression of

full bacterial virulence in mice (Harvill, et al, 2000). It is also believed that LPS may act in synergy with

tracheal cytotoxin (Turcotte, 1997) or other toxins and may also have a role in the resistance of B.


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pertussis to antibiotics.

Monoclonal antibodies specific for band A trisaccharide (vide infra) of theB. pertussis LPS have been

shown to inhibit the invasion of HeLa cells byB. pertussis, and they can also transfer immunity to

infection in an infant mouse lung infection model (Shahin et al, 1994). Furthermore, these monoclonalantibodies have been shown to be bactericidal (Weiss et al, 1999)

LPS from otherBordetella species such asB. bronchiseptica, have similar toxicity to LPS fromB.

pertussis andE. coli, although LPS fromB. parapertussis has lower activity (Watanbe et al, 1990).

4. Regulation of Virulence Factors inB. pertussis

4.1 Phase variation

The production of virulence factors inB. pertussis is regulated in several different ways.B. pertussis

undergoes phase variation resulting in the loss of most virulence factors and some undefined outermembrane proteins. Phase variation has been shown to occur at a genetic frequency of 10 -4 - 10-6

generations and results from a specific DNA frame shift that comes about after the insertion of a single

nucleotide into the bordetella virulence gene (bvg, also known as vir) operon. The bvg which controls

expression of a number ofB. pertussis virulence factors including genes for pertussis toxin, ptx

filamentous hemagglutinin, fhaB, BvgAS, bvgAS and adenylate cyclase toxin, cya (Wood and Friedman,

2000).

4.2 Phenotypic modulation

A similar process called phenotypic modulation, occurs in response to environmental signals such astemperature or chemical content, and is reversible (Fuchs et al, 1996). This is an adaptive process

mediated by the products of the bvg operon, and is an example of a two-component environmental-

sensing (regulatory) system used by other bacteria. The expression of these regulatory proteins is itself

regulated by environmental signals, such that entry into a host might induce components required for

survival and production of disease.

5. The control ofBordetella pertussis

AlthoughBordetella pertussis is susceptible to most antibiotics, these are not effective in treatment, as

by the time the disease has been diagnosed, the bacteria have already damaged the respiratory tract and

released toxins. Therefore prevention is of supreme importance (Moxon and Rappuoli, 1990).

5.1. Vaccines

The development of the whole cell whooping cough vaccine in the 1940s has made whooping cough a

less common disease in developed countries. This vaccine is composed ofB.pertussis cells killed by

formalin and treated at 56oC for 30 min (Rappuoli, et al, 1991). In countries where the vaccine is not

used, whooping cough is an major cause of infant mortality, with an estimated 51,000,000 cases and

600,000 deaths annually (Todar, 1997). However,pertussis epidemics have been described in the USA

amongst highly immunised populations, which has led too concerns about the protective effectiveness of

the whole cell vaccine (Bentsi-Enchill, et al, 1997). Historically, the whooping cough vaccine has been

administered as a merthiolate-killed bacterial cell suspension, which is part of the diphtheria pertussistetanus (DPT) triple vaccine. However, about 20% of the children that receive the whole cell vaccine


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experience mild side effects, with 0.5% of infants experiencing convulsions soon after receiving the

vaccine (infantile epilepsy) (Cherry, 1997). In a very small number of cases (1 in 100,000) children

experience encephalopathy and permanent neurologic sequelae.

5.2. Current vaccines and new opportunities

Recently, several new vaccines have been developed from purified components ofB. pertussis. The first

acellular vaccine was produced from purified PT and FHA in 1981 (Rappuoli et al, 1991). Acellular

pertussis (DtaP) consists of a single weakened toxoid, whereas previous pertussis vaccines contained

multiple toxoids. Chemically detoxified pertussis toxin is an example of a DtaP vaccine, which consists

of a genetically engineered form of the toxin. To avoid reversion to toxicity one or two key amino acids

within the enzymatically active S1 subunit of the toxin have been introduced into the chromosome of

some strains ofB. pertussis,B. parapertussis andB. bronchiseptica. These strains produce mutant

pertussis toxin molecules that are non-toxic and immunogenic, as they protect mice against infection

(Pizza et al, 1989). Other acellular vaccines also contain other bacterial antigens, including filamentous

hemagglutin and pertactin (Podda et al, 1993). These have been found to be more effective than singlecomponent vaccines (Cherry, 1997)

Although DtaP is more expensive than the older version and may not be as effective, it is hoped that it

will have fewer side effects than DTP, particularly in older people who are more prone to them. These

acellular vaccines have been put to use in Sweden, Japan and the UK. All elicit some, but not complete

protection against colonisation and/or severe disease.

As mentioned before, phase variation and phenotypic modulation regulate the virulence factors in

Bordetella pertussis. This means that the organism is subject to continual mutations within important

virulence factors that are used as vaccine components.

The lipid A pathway is an excellent target for the design of new antibiotics against gram negative

bacteria, such asBordetella pertussis, E. coli, Salmonella, andPseudomonas. Potent LpxC inhibitors

have been identified (Onishi et al, 1996) see figure 1.5. The best LpxC inhibitor is comparable to

ampicillin, a classical lactam.

6. The Structure and Biosynthesis of LPS

6.1. Common features of LPS

Lipopolysaccharides (LPS) of gramm-negative bacteria are amphipatic molecules, also called endotoxins, are

located in bacterial outer membranes (Figure 4). All LPS contain a non-polar lipid moiety lipid A which anchors

endotoxin in the outer membrane of bacteria and is covalently linked to a heteropolysaccharide chain (Figure 5).This chain is composed of a core oligosaccharide and a oxygen-antigen (O-antigen). The heteropolysaccharide isexposed to the surrounding exoplasm and determines the serological identity of the bacterium. The O-antigenconsists of repeating oligosaccharide units, which are specific for each bacterial strain. The O-antigen conferssmoothness to the organism, which serves to decrease the likelihood that a bacterial cell will be phagocytized. Italso reduces surface hydrophobicity allowing better interaction with other protein-coated membranes. O-Antigensare highly antigenic and may be exploited for a humoral immune response. However, in B. pertussis O-antigen iscompletely missing (Preston et al, 1999, Caroffet al., 2000).

6.2. The chemical structure of B. pertussis LPS

Monosaccharides of the B. pertussis core oligosaccharide (band B) include galactosaminuronic acid (GalNAc),glucuronic acid (GlcA) and glucosamine (GlcN), all of which are charged, and all of which are not commonly found


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as constituents of other LPS core molecules. The lipid A part of LPS is covalently linked to a singleketodeoxyoctulosonic acid (Kdo) residue and then to a branched-chain oligosaccharide (Allen et al, 1998a). LipidA in B. pertussis has been fully characterised. The oligosaccharide moiety of the LPS is heterogeneous. The majocomponent of the endotoxin is the LPS with a dodecasaccharide core whereas the minor component contains thesame oligosaccharide but lacking three distal sugars (Caroffet al, 1990). The full structure of the LPS (Figure 6)

has been recently elucidated (Caroff, 2000).

6.3. Lipolysaccharide genetics

LPS genetics is not a simple subject. The proteins encoded by the genes can be involved in metabolism

(for the biosynthesis of the sugar substrates), polymerisation of the polysaccharide, transport of the

molecule to the outer membrane and correct assembly of the molecule at the outer membrane (Maskell

Allen, 1997).

Three classes of genes responsible for LPS biosynthesis have been identified in enteric bacteria (Reeves

et al, 1996). The genes rmlA, rmlB, rmlC, and rmlD are involved in synthesis of sugar intermediates,

such as dTDP-rhamnose. Sugars commonly present in O antigens, which elicit rfc cluster specificity in

Salmonella, are synthesised on a lipid carrier called undecaprenol pyrophosphate.

6.4 The wlb gene locus

InB. pertussis the wlb gene locus (formerly bpl) (Reeves et al, 1996) (wlbA-wlbL) is required for LPS

trisaccharide biosynthesis (Allen et al, 1998 b) and consists of 12 genes. To the left and divergent fromthe wlbpe locus are two genes involved in deep inner core synthesis (waaApe and waaCpe).

Sequence homology studies have been carried out on the wlb genes inBordetella pertussisby comparing

them to the genes involved in enterobacterial common antigen biosynthesis. The first two open reading

frames in the wlb locus point leftwards and encode waaA (for the addition of Kdo) and waaC, (for the

addition of the first heptose). The stop codon of waaC overlaps with the start codon of waaA, which

suggests that these two enzymes have coupled translation. It has been suggested that wlbA encodes a

dehydrogenase, wlbB encodes an acetylation enzyme, wlbC transfers amino groups to sugars (and is

homologous to wlbF), wlbD is a UDP-GlcNAc-2-empimerase, which catalyses the formation of UDP-

ManNAc, and wlbE encodes a sugar transferase (Table).

Table: The wlb genes ofB. pertussis and their proposed gene function.

Gene Old Name Proposed function

waaA kdtA Kdo-transferase

waaC rfaC Glycosyl transferase


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wlbA bplA 3-/6-dehydrogenase

wlbB bplB Acetyl transferase

wlbC bplC 3-transaminase

wlbD bplD UDP-GlcNAc 2epimerase

wlbE bplE Glycosyl transferase

wlbF bplF 4-transaminase

wlbG bplG Glycolipid synthase

wlbH bplH Glycosyl transferase

wlbI bplI Methyl transferase

wlbJ bplJ Acetyl transferase

wlbK bplK Acetyl transferase

wlbL bplL Dehydratase

It has been proposed that the gene product encoded by wlbA is a 3- or 6-dehydrogenase and convertsUDP-2,3-diNAc-Man to UDP-2,3-diNAc-ManA (Maskell and Allen et al, 1996). The Maskell group has

generated definedB. pertussis mutants lacking the LPS band A trisaccharide, a characteristic which has

been shown to severely compromise their ability to infect mice (Petrovska et al, 1999), see Figure 7.

.

Based on the SDS-PAGE mobilities of the LPS mutants it can be concluded that mutations in the wlbF,

G, I and L genes gives rise to band B LPS phenotypes, suggesting that these genes are probably involved

in an early stage of LPS biosynthesis.


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Mutations in wlbA-E gives rise to LPS structures which correspond to band B and band B + one sugar,

suggesting that A-E are involved in the formation and transfer of the middle sugar of band A

trisaccharide (MandiNAcA). Mutation of wlbH leads to a band B and a band B + two sugars LPS

structure, indicating that it may be the terminal GlcNAc transferase required for band A trisaccharide

formation. WlbJ and K are not required for band A synthesis; mutations in these genes result information of apparent wild-type band A. The function of these genes remains unclear. A pathway for the

biosynthesis of UDP-MandiNAcA from UDP-D-GlcNAc inB. pertussis has been proposed based on

functional assignments of wlbA-D from sequence homology studies (see figure 1.9).

WlbA-D have been expressed inE. coli using the IMPACT expression system in collaboration with the

Maskell group at Cambridge Veterinary School. BLAST searches have shown that wlbA shows no

significant homology toE. coli UDP-ManNAc dehydrogenase (rffD) or UDP-Gluc dehydrogenase

(kfiD), which show 45% similarity (28% identity) to each other, and both of which convert primary

alcohols to carboxylic acids. WlbA does, however show homology (30% identity) to inositol

dehydrogenase, an enzyme that converts a secondary alcohol to a ketone (see table 1.2 for sequence

homology comparisons).

WlbA may be responsible for the oxidation of UDP-GlcNAc to UDP-3-keto-GlcNAc, prior to the

transaminase action of wlbC (see figure 1.9). UDP-3-keto-GlcNAc was originally proposed by Salo

(Salo, 1976) as an intermediate in the UDP-GlcNAc 2empimerase process, although the absence of a

redox cofactor ruled this out. The mechanism of this epimerase was shown by Tanner to involve an

elimination-addition process (Sala et al, 1996).

wlbB shows homology (40-75% identity) to a variety of acetyl and acyltransferases. WlbC shows

homology (35-65% identity) to a variety of aminotransferases, and is 58% identical to wlbF, although no

obvious transamination role can be ascribed to wlbF.

http://pkukmweb.ukm.my/~danial/Bordetella.html

BORDETELLA

Tiga spesies dalam genus Bordetella. Patogen utama ialah B. pertussis yangmenyebabkan batuk ayam atau batuk kokol atau pertussis. Pertamadipencilkan oleh Bordet dan Gengou. Kokobasilus Gram positif tak motil,aerob obligat. Apabila baru dipencilkan organisma ini mempunyai kapsul danpili dan adalah virulen (fasa 1). Setelah disubkulturkan bebarapa kali iabertukar menghasilkan koloni kasar (S ke R) (fasa 4). Kapsul dan pili tidakhadir dan kevirulenan hilang pada fasa 2 dan 3, yang dipanggil fasaperantaraan. Selain kapsul dan pili organisma fasa 1 juga menghasilkan

eksotoksin yang dermonekrotik untuk arnab dan letal untuk mencit.


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Parasit obligat pada manusia dan haiwan; berganda pada silia sel-selepitelium. Manusia merupakan satu-satunya hos untuk B. pertussis dan B.

parapertussis. Infeksi pertussis adalah meluas di seluruh dunia dan mudahberjangkit, boleh menyebabkan maut terutama pada kanak-kanak.

Faktor-faktor kevirulenan:

1. Toksin pertussis:histamine sensitizing factor (HSF), lymphocytosispromoting factor, Islet activating protein (IAP)

73 - 77 kDa, stabil haba; toksin jenis A-B, heksamer (S1 - S5) di manaS1 ialah subunit A, S2 S4 dan S3 S4 membentuk dimer yang

dihubungkan oleh S5.


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Toksin ini bergabung pada sel dan bahagian aktif masuk ke dalam seldan bertindak sebagai enzim adenosine diphosphate (ADP)-ribosiltransferase. Substratnya ialah Gi, suatu protein yang terlibat dalamkawalan adenilat siklase. Oleh itu kesannya ialah peningkatan arascAMP. Toksin ini juga menghalang perpindahan limfosit dari saluran-

saluran darah kecil.

Pengaktifan adenilat siklase oleh toksin pertusis. Subunit A toksinpertusis memindahkan kumpulan ADP ribosil dari NAD kepada proteinkawalan Gi yang terikat pada membran. Pergabungan inimenyahaktifkan protein Gi yang tidak lagi menjalankan fungsinyamerencat adenilat siklase. Pertukaran ATP kepada cAMP tidak disekatdan aras cAMP akan meningkat.

2. Adenilat siklase luarsel: teraktif dalam sel hos, meningkatkan arascAMP.

Kedua-dua faktor 1 dan 2 meningkatkan cAMP, merencat kemotaksisPMN dan menghalang penghasilan hidrogen peroksida.

3. Hemaglutinin (HA): 2 jenis

a) F-HA (filamentous-HA) - 130 kDab) PT-HA (pertussis toxin-HA)

- membantu perlekatan Bordetella kepada silia

4. Toksin tak stabil haba (heat labile toxin): - dermonekrotik dan

menyebabkan maut (lethal) jika disuntik ke dalam mencit; eksotoksinini tidak stabil haba dan tergabung kepada dinding sel dan dibebaskanapabila sel terlisis.

Epidemiologi:

Mudah disebarkan; manusia merupakan satu-satu punca B. pertussis.

Patogenesis:

Organisma ini masuk melalui saluran pernafasan atas. Organisma ini

mempunyai ciri-ciri viscerotropicdan melekat kepada sel-sel epitelium bersiliayang terdapat pada bronkus. Batuk ayam adalah satu infeksi permukaan dan


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Pengimunan (DPT); pemencilan pesakit dari kanak-kanak; kemoprofilaksiserythromycin untuk mereka yang berdamping dengan pesakit.

Bordetella Pertussis and Whooping Cough

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