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WHAT IS HIV? Human immunodeficiency virus (HIV) is a lentivirus (a

member of the retrovirus family) that causes acquired

immunodeficiency syndrome (AIDS), a condition in

humans in which the immune system begins to fail,

leading to life-threatening opportunistic infections.

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A virus is not a cell, but is madeup of genetic instructionscontained in a protective shell.

A single HIV virus particle iscalled a virion. It is spherical andone 10,000th of a millimeter indiameter.

The protective shell of the virus isknown as the viral envelope. It is

composed of two layers of fattymolecules.

Embedded in the envelopesurface is complex HIV proteincalled the env protein that sticksout of the envelope surface.

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Env consists of a cap

called gp120 and a stemcalled gp41.

The viral core is called thecapsid.

Major elements within theviral core are:

Two single strands of HIVRNA. RNA carries geneticinstructions that allow the

HIV virus to replicateitself.

There are enzymes thatare needed for replicationof the virus.

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Infection with HIV occurs by the transfer of blood, semen,

vaginal fluid, pre-ejaculate, or breast milk. Within these

bodily fluids, HIV is present as both free virus particles

and virus within infected immune cells. The four major

routes of transmission are unsafe sex, contaminated

needles, breast milk, and transmission from an infected

mother to her baby at birth (Vertical transmission).

TRANSMISSIO

N

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Screening of blood products for HIV has largely

eliminated transmission through blood transfusions

or infected blood products in the developed world.

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There are two strains of HIV known to exist: HIV-1 and

HIV-2. HIV-1 is the virus that was initially discovered

and termed LAV. It is more virulent, relatively easily

transmitted, and is the cause of the majority of HIV

infections globally. HIV-2 is less transmittable and islargely confined to West Africa.

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Species Virulence Transmittability Prevalence Purportedorigin

HIV-1 High High Global CommonChimpanzee

HIV-2 Lower Low WestAfrica

Sooty

Mangabey

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HIV-1 Subtypes Three groups of HIV-1 have been identified on

the basis of differences in env: M, N, and O.

The new one has been classified P. The N and Ovariants are extremely rare.

Group M is the most prevalent and is subdividedinto eight subtypes

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PATHOPYSIOLOGY: HIV causes AIDS by depleting CD4+ T helper

lymphocytes (a subset of T cells). This weakens the

immune system and allows opportunistic infections.T lymphocytes are essential to the immune response

and without them, the body cannot fight infections

or kill cancerous cells. The mechanism of CD4+ T cell

depletion differs in the acute and chronic phases.

http://en.wikipedia.org/wiki/T_cellhttp://en.wikipedia.org/wiki/T_cellhttp://en.wikipedia.org/wiki/T_cellhttp://en.wikipedia.org/wiki/T_cell

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Tuberculosis (TB)

Bacterial pneumonia

Mycobacterium avium complex (MAC)

Salmonellosis

Bacillary angiomatosis (Bartonella henselae bacteria)

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Cytomegalovirus (CMV)

Viral hepatitis

Herpes simplex virus (HSV)

Human papillomavirus (HPV)

Progressive multifocal leukoencephalopathy (PML)

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Candidiasis

Cryptococcal meningitis

Parasitic infections:

Pneumocystis carinii pneumonia Toxoplasmosis

Cryptosporidiosis

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Wasting syndromeNeurological complications

Other complications:

Kaposi's sarcoma

Non-Hodgkin's lymphoma

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Stage I: HIV infection is asymptomatic and not categorized asAIDS

Stage II: includes minor mucocutaneous manifestations and

recurrent upper respiratory tract infections

Stage III: includes unexplained chronic diarrhea for longerthan a month, severe bacterial infections and pulmonarytuberculosis

Stage IV: includes toxoplasmosis of the brain, candidiasis ofthe esophagus, trachea, bronchi or lungs and Kaposissarcoma; these diseases are indicators of AIDS.

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HIV RESISTANCE

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TREATMENT There is currently no vaccine or cure for HIV or AIDS.

The only known methods of prevention are based on

avoiding exposure to the virus or, failing that, an

antiretroviral treatment directly after a highly significant

exposure, called post-exposure prophylaxis (PEP). PEP

has a very demanding four week schedule of dosage. Italso has very unpleasant side effects including diarrhea,

malaise, nausea and fatigue

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Current treatment for HIV infection consists of

highly active antiretroviral therapy, or HAART.

Thishas been highly beneficial to many HIV-infectedindividuals since its introduction in 1996, when theprotease inhibitor-based HAART initially became

available. Current HAART options are combinations(or "cocktails") consisting of at least three drugsbelonging to at least two types, or "classes," ofantiretroviral agents. Typically, these classes are twonucleoside analogue reverse transcriptase inhibitors(NARTIs or NRTIs) plus either a protease inhibitoror a non-nucleoside reverse transcriptase inhibitor(NNRTI).

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HAART neither cures the patient nor does it uniformly

remove all symptoms; high levels of HIV-1, often

HAART resistant, return if treatment is stopped.

Moreover, it would take more than a lifetime for HIV

infection to be cleared using HAART. Despite this, many

HIV-infected individuals have experienced remarkable

improvements in their general health and quality of life,

which has led to a large reduction in HIV-associated

morbidity and mortality in the developed world.

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In the absence of antiretroviral therapy, the median

time of progression from HIV infection to AIDS is

nine to ten years, and the median survival time after

developing AIDS is only 9.2 months. However, the

rate of clinical disease progression varies widely

between individuals, from two weeks up to 20 years.

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Despite the success of highly active antiretroviral therapy(HAART) in controlling HIV infection and reducing HIV-associated mortality, current drug regimens are unable tocompletely eradicate HIV infection. Many people on HAARTachieve suppression of HIV to levels below the limit ofdetection of standard clinical assays for many years.However, upon withdrawal of HAART, HIV viral loadsrebound quickly with a concomitant decline in CD4+ T-Cells,which, in most cases, absent a resumption of treatment, leads

to AIDS

http://en.wikipedia.org/wiki/HAARThttp://en.wikipedia.org/w/index.php?title=CD4+_T-Cells&action=edit&redlink=1http://en.wikipedia.org/wiki/AIDShttp://en.wikipedia.org/wiki/AIDShttp://en.wikipedia.org/w/index.php?title=CD4+_T-Cells&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=CD4+_T-Cells&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=CD4+_T-Cells&action=edit&redlink=1http://en.wikipedia.org/wiki/HAART