Bacterial superantigensand related virulence factors

Bo NilsonClinical MicrobiologyLabmedicin Skåne

Outline

• T cell superantigen– Mechanism, structure, genetics– SAG association with diseases

• B cell superantigen• Staphylococcal Superantigen-like

proteins

Different classes of bacterial components able toinduce inflammation and cytokine synthesis

• Lipopolysaccharides• Peptidoglycans• Lipopeptides• Glycolipids• Superantigens• Exotoxins• Oligosaccharides• Oligopeptides• Lipoproteins

• Glycoproteins• Adhesions• CpG DNA• Lipoarabinomannans• Molecular chaperones• Lipids• Fimbriae• Phospolipases• Proteinases

What happens upon encounter with asuperantigen?

1. Induction of T cell reactivity (up to 30%)(conventional Ags ~0.001%)

2. Induction of APC activity3. Massive cytokine release – Cytokine ”storm”4. Signs of shock------death

Normal antigen processning and presentation

Antigen-presenting cell (APC)

Superantigen

0.001% 5-20%

Superantigens bind to MHC class II and TCR

TCR

MHC

Superantigen (SAG)

”Normal antigen presentation” Presentation by superantigen

TCR

MHC

Superantigen (SAG)

”Normal antigen presentation” Presentation by superantigen

SAG-unique Vβ TCR-signatures

Cell activation by superantigen

APC

CD4+

CD8+

cytotoxicity

IFN-γ

IL-2

TNF-α

IL-1

TNF-α

MHC-II

SAG

TCR

Genes regulated >10-fold by SAG treatment of PBMC after 6h

Grumann et al J Immunol 2008

Cytokine ”storm”

Origin of Bacterial Superantigens

• Staphylococcus aureus– Staphylococcal enterotoxin (SEs) A-E, G-J– Straphylcoccal enterotoxin-like (SEls) K-R, U, V, X– Toxic Shock Syndrom Toxin 1 (TSST-1)

• Streptococcus pyogenes– Streptococcal pyrogenic exotoxin (SPE) A, C, G-M– Streptococcal superantigen (SSA)– Streptococcal mitogenic exotoxin Z (SMEZ)

• Group C Streptococcus equi– SPE-LSe, SPE-MSe

• Group G Streptococcus disgalactiae– SPE-Gdys, SDM

• Mycoplasma arthritidis– Mycoplasma arthritidis mitogen (MAM)

• Yersina pseudotuberculosis– Yersina pseudotuberculosis mitogen (YPM) A-C

Viral and Fungal superantigens have also been described

(n>21)

(n>11)

(n>2)

(n>1)

(n>3)

(n>2)

A pairwise comparison of five S. aureus genomes

Lindsay and Holden TRENDS in Microbiology 2004

Gill et al 2005 J Bacteriol.

The number of superantigen genes in different strains of S. aureus vary

(n=4) (n=10) (n=11) (n=7)

MW0345 selx

MHC-TSST-TCRMHC-SpeC-TCR

MHC-TCR MHC-SEB-TCR

SEB

TSST-1

SpeC

SEA

SEH

MHC-SEH-TCR

MHC-SEA-TCR

TCR

MHC

TCR

MHC

Proft & Fraser 2003 Clin. Exp. Immunol.

Human disease causation/association with SAG• Staphylococcal nonmenstrual TSS

– Wound, boil, abscess– Postrespiratory viral– Purpura fulminans– Necrotizing pneumonia– Recalcitrant erythematous desquamating in AIDS– Kawasaki-like– Scleroderma-like– Acute-onset rheumatoid arthritis-like

• Staphylococcal menstrual TSS• Streptococcal TSS• Staphylococcal food poisoning• Atopic dermatitis• Asthma• Conjunctivitis• Severe nasal polyposis• Sudden infant death syndrome• Acute rheumatic fever• Perineal erythema• …

Staphylococcal Toxic Shock Syndrom (TSS)

• Initial symptoms: high fever, vomiting, diarrhea, conjunctivitis,headache, irritability, sore throat, myalgias, abdominal tenderness, anderythematous rash.

It rapidly progress to hypotension, shock, respiratory distress syndrome,intravenous coagulation, severe thrombocytopenia, and renal failure

• In TSS staphylococcus cultures are rarely isolated from blood more oftenfrom mucosal sites or from a localized abscess

• Non-menstrual TSS has been associated to TSST-1, SEA, SEB & SEC

US outbreak of menstrual TSS in late 1970s• Strong link to the use of high absorbency Relay tampon• 94% of the mTSS-strains produced high levels of TSST-1

vs 4% in non-TSS strains• TSST-1 penetrate epithelial cells

Streptococcal TSS (STSS)

• STSS caused by S. pyogenes is a more acute condition than TSS.Fatality rate is much higher– STSS (~30-50%) vs TSS (~ 5%)

• Characteristic symptoms of STSS include hypotension, fever, rash,vomiting, diarrhea, multiple organ failure, and shock

• STSS is often associated with bacteremia, myositis, or necrotizingfascitis and can occur in patients with no outward sign of bacterialinfection

• The superantigens SMEZ, SpeA & SpeC are most associated withSTSS

Clinical Definition of Toxic Shock Syndrome

Staphylococcal TSS• Fever• Hypotension• Rash-diffuse, macular

erythroderma• Skin desquamation upon

recovery• Three of the following organ

system changes:– Liver– Blood– Renal– Mucous membrane– Gastrointestinal– Muscular– Central nervous system

Streptococcal TSS• Isolation of group A

streptococci from:– Sterile site for a definitive case– A nonsterile site for a probable

case• Hypotension• Two of the following symptons:

– Renal dysfunction– Liver involvement– Erythematous macular rash– Coagulopathy– Soft tissue necrosis– Adult respiratory distress

syndrome

TSS STSS

Susceptibility factors for TSS

• Genetic background of the host, in particularMHC class II polymorphisms

• Lack of neutralizing anti-SAG serum antibodies

85% of the patients do not develop immunity to TSST-1 uponrecovery from menstrual TSS and are therefore susceptible forrecurrences

Only 80-85% of humans develop antibodies to TSST-1

Annual incidence of TSS in USA

Menstrual TSS

Non-menstrual TSS

DeVries PLoS ONE 2011

Lappin 2009

Food Poisoning

• Staphylococcal enterotoxins are potentgastrointestinal toxins (>1 ug) and is oneof the most common causes for foodpoisoning

• Intake of contaminated food with toxins

• 1-2 hrs symptoms; nausea & vomiting

• Note: e.g. TSST-1 and SpeA are notenterotoxins

• The mechanism is not determined

Atopic Dermatitis

Evidence of role of staphylococcal superantigens in AD– Epicutaneous application of superantigens induces eczematoid dermatitis– Patients recovering from TSS develop chronic eczema– Most patients with AD are colonized with S. aureus– S. aureus counts are more than 1000-fold higher in lesional skin than

non-lesional– A majority of S. aureus from AD skin produce SAGs– Peripheral blood mononuclear cells from AD have higher proliferative

response to superantigens– Superantigens induce the skin homing receptor on T cells– AD severity correlates with presence of IgE antibodies to superantigens– Superantigen argument allergen-induced skin inflammation by activating

infiltrating mononuclear cells and inducing mast cell degranulation

Treatment of AD patients with steroids in combination with antibioticsis more effective than treatment with steroids alone and is inaccordance with the view that the SEs induce or exacerbate AD.

Superantigen-induced corticosteroidresistance of human T cells

Li et al J Allergy Clin Immunol 2004

Allergic rhinitis

• Some 20% of the human population are permanently, and 60%intermittently colonized by S. aureus in their nasal mucosa.

• Nasal carriage of S. aureus are higher in patients allergic rhinitis (44%versus 20% in control subjects) and this has been associated withincreased nasal IgE levels

• Significant association with SAG-producing S. aureus (22% versus6.7% in control subjects)

• IgEs specific to S. aureus SEA, SEB, SEC, SED and TSST-1 havebeen reported in the serum of both allergic rhinitis and asthma patientsat higher incidence than in normal controls and SAG-specific IgElevels were correlated with disease severity.

• Antibiotics have proved to be a useful adjunct to steroids and -agonistsin the treatment of asthma.

Septic arthritis

Bremell & Tarkowski, Infect Immunity 1995, 63,4185-4187.

Great diversity of SAGsin different strains of S. aureus and S. pyogenes

• There are many different SAGs and they interact in manydifferent ways with TCR and MHC II leading to differencesin stimulation

• The number of expressed SAGs vary between strains (0 to16)• The combinations of SAGs vary between S. aureus strains• The expression level vary between SAGs

– Some SAGs are produced at very high concentrations (100 ug/ml)– Other are made at very low concentrations (0.0001-0-001 ug/ml)

• Some SAGs are expressed during exponential growth phaseother are produced in the stationary phase

• In addition the genetic background of the host vary,particularly MHC class II polymorphisms

Some SAGs also display additionalproperties than superantigen-activity

• Enterotoxin• Act synergistically with endotoxin (LPS)• Penetrate epithelial cells• Cause steroid resistance• Attract neutrophil cells independently of TCR and MHCII• B cell superantigens

Related virulence factors:

B cell superantigen

Two domainsof Protein A

B cell superantigens are a group of molecules being ableto bind and cross-link non polymorphic parts of BCRs

Fab

Fab

• Staphylococcus aureus– Protein A (VH3 Ig)– Staphylococcus enterotoxin (SEs)

• SEA (VH3 Ig)• SED (VH4 Ig)

• Finegoldia magna– Protein L (VLκ Ig)

• Moraxella catarrhalis– MID (IgD)

Related virulence factors:

B cell superantigen

Related staphylococcal virulence factors

• Staphylococcal superantigens– Enterotoxin (SEs)– Enterotoxin-like (SEls)– TSST-1

• Staphylococcal superantigen-like proteins (SSLs)(previously called SET proteins)

Staphylococcal Superantigens-likeProteins (SSL)

Staphylococcal and Streptococcal Superantigens

Related staphylococcal virulence factors

(n>14)

(n>36)

(n=11) (n=11) (n=15) (n=14)selx5

SA0442 selx1 SAV0370 selx1

SAV0357 selx1

CHIPS

ProtA Evation of complement attack

Baker et al JMB 2007

Crystal Structure of theStaphylococcal Toxin SSL5 inComplex with Sialyl Lewis X

Bestebroer et al. Blood 2009

Staphylococcal SSL5 inhibit leukocyte activation by targetingchemokine and anaphylatoxin receptors

CXCL8CXCL1CXCL12CCL2CCL3CCL5CX3CL1

C3aC5a

PSGL-1

Chavakis et al 2007 Trends in Immunology

Mechanisms for the inhibition of leukocyte recruitment

Conclusions

1. Superantigens contribute to diseasepathology/outcome during ongoing infection, thusnot only of importance in TSS and food poisoning

2. A major contribution is mediated via activation ofT cells in a Vbeta specific manner

3. SAGs and related virulence factors in S. aureustarget crucial elements of our immune system byusing small structure-related protein folds

References

Superantigen reviewFraser JD and Proft T. The bacterial superantigen and superantigen-likeproteins. Immunol Rev. 2008; 225: 226-243.

Therapy for TSSLappin E and Ferguson AJ. Gram-positive toxic shock syndromes LancetInfect Dis. 2009; 9: 281–90

The role of PVL and superantigens in pneumoniaSchlievert PM. Cytolysins, Superantigens, and Pneumonia Due toCommunity-Associated Methicillin-Resistant Staphylococcus aureus JInfect Dis. 2009; 200: 676-678.