HUMAN IMMUNODEFICIENCY VIRUS (HIV)

Important Properties:

HIV is an RNA retrovirus. It consists of two identical molecules of single-stranded positive polarity RNA and is said to be diploid. There are two types of this virus:

HIV1

HIV2

Both these cause AIDS but HIV1 is found worldwide whereas HIV2 is found in WEST AFRICA.

ENZYMES IN HIV:

1:REVERSE TRANSCRIPTASE

2:INTEGRASE

3:PROTEASE

REVERSE TRANSCRIPTASE:

It is RNA dependent DNA polymerase only present in retroviruses. This enzyme transcribes the RNA into DNA.

INTEGRASE:

It mediates the integration of the viral DNA into the host cell DNA.

PROTEASE:

It cleaves the precursor polyproteins into the functional viral polypeptides.

REPLICATIVE CYCLE:

As it is retrovirus after entry into the cell by binding to the CD4 protein on the cell surface it fuses with the cell membrane and its RNA and reverse transcriptase enters the cytoplasm. In the cytoplasm reverse transcriptase transcribes the viral RNA into double-stranded DNA, which migrates into the nucleus, where it integrates into the host cell DNA. Viral mRNA is formed from the DNA by hist cell RNA polymerase.

PATHOGENESIS:

HIV infects the helper T cells and kills them resulting in suppression of the cell-mediated immunity. HIV also infects brain monocytes and macrophages.

DISEASE:

HIV1 and HIV2 both cause Acquired Immuno Deficiency Syndrome (AIDS).

CLINICAL FINDINGS:

In the acute stage which usually begins 2 to 4 weeks after infection fever, lethargy, sore throat and lymphadenopathy occur.

In the middle stage of HIV infection, a long latent period that lasts for 7 to 11 years the patient is asymptomatic. A syndrome called AIDS-related complex can occur during the latent period characterised by fever, fatigue, weight loss.

 

The late stage of HIV infection is AIDS characterised by a decrease in CD4 cells below to 200/miroliter.

TRANSMISSION:

It is transmitted through sexual contact and by transfer of infected blood.

LABORATORY DIAGNOSIS:

The early diagnosis of both HIV1 & HIV2 infection is made by using ELISA that detect antibodies.

PCR can also be done to detect the amount of viral RNA in the plasma.

TREATMENT:

Treatment involves antiretroviral drugs.

1:Reverse Transcriptase Inhibitors

2:Protease Inhibitors

3:Entry Inhibitors

4:Integrase Inhibitors

PREVENTION:

No vaccine is available.

Use Condoms during sex

Not sharing needles

Discard blood contaminated with HIV