HIV(Human Immunodeficiency Virus

Properties of HIV virus:

• HIV is a RNA virus belongs to the Retroviridae;was first described in 1981 and isolated in 1983.
• HIV belongs to the lentivirus subgroup of retrovirus
• Has double copy of the genome(diploid)
• Possess reverse transcriptase enzyme
• Has envelope
• Surface antigen-glycoprotein120,glycoprotein 41
• Incubation period-6 months to 6 years or more(Causes slow virus infection)
• Both HIV-1 and HIV-2 causes AIDS,but HIV-1 is found worldwide,whereas HIV-2 is found primarily in west Africa.
• HIV infects and kill helper T cell, resulting in the loss of cell mediated immunity, and causes opportunistic infection.Other cells e.g.macrophages and monocytes have CD4 proteins on their surface can be infected also.

HIV model: virus structure

Mode of Transmission of HIV:

• Sexual contact with infected individual-vaginal sex, anal sex, deep kiss.
• Transmission in blood:Receiving infected blood, blood products(Factor VIII concentrates.)
• Sharing needles as in drug abusers or accidental inoculation.
• Peripheral transmission:Mother to baby,either transplacentally(vertical) or perinatally. Infection may be acquired from breast milk.

Pathogenesis of AIDS: After entry into blood stream,HIV attaches to CD4-(Helper T) cell & lymphocytes; grows slowly in CD4+ and monocytic cell. The deplition of CD4+ cells and macrophages result in impaired vell mediated immunity and humoral immune responses. The normal ratio of CD4+ to CD8+ is 2:1; which is reversed as 1:2. This leads to recurrent life threatening opportunistic infections.

Clinical Features of AIDS:

a.Early(acute) clinical features(begins after 2-4 weeks of infection):

• Fever
• Lethargy
• Sore throat
• Diarrhoea
• Generalized lymphadenopathy
• Maculopapular rash on the trunk,arms,and legs (but sparing the palm and sole)
• Leucopenia occurs,but the number of CD4 cells is usually normal,high level of viremia occurs

Antibodies to HIV typically appear 10-14 days after infection.
b.Intermediate stage:
AIDS related complex(ARC)-

• Persistent fever
• Fatigue 
• Weight loss
• Generalized lymphadenopathy

c.Late stage of HIV infection is AIDS: Patient develops opportunistic infection by both pathogenic & non-pathogenic organisms.

Laboratory diagnosis of AIDS: 

AIDS is practically diagnosed by serological test for antibody against the virus.Electron microscopy is done in reference lab.Cell culture is done for research purpose.NA based techniques are used in special cases.

Treatment of HIV infection(AIDS):

A.Current treatment of choice:
Regimen consisting of two-nucleoside inhibitor(Zidovudine & Lamivudine)-this combination is known as HAART [highly active antiretroviral therapy]
B.In addition to nucleoside inhibitor there are non-nucleoside reverse transcriptase inhibitors that are effective against HIV-Nevirapine(viramune),delavirdine(rescriptor) & efavirenz(Sustiva)
C.Protease inhibitor: Saquinavir(Invirase), ritonavir(Norvir),nelfinavir(viracept) & indinavir(Crixivan)

GOZmosis:On Cure for HIV

Prevention of AIDS:

• Avoidance of promiscuity & anal intercourse
• Use of condom
• Screening of blood & blood products
• Use of disposable syringe and needles
• Interruption of perinatal transmission by screening women of child bearing age.
• Counseling of person found to be antibody positive
• Education about the mode of transmission & how to avoid infecting others & how to protect themselves.