Acquired Immunodeficiency Syndrome

Virus causing the disease

• Human T-lymhphotropic virus type III
• (HTLV III)
• or Human Immunodeficiency Virus
• HIV
• Recognized recently but has probably been infecting humans any where from 20 to 100 years

Etiology

• 1983 Pasteur institute in Paris isolated the virus and named it lymphadenopathy virus (LAV)
• American research team isolated the same virus and called it HTLV-III
• in 1984 Gallo was able to conclusively show that the virus was the cause of AIDS

Cont

• Name changed to HIV
• In 1985 second AIDS causing virus isolated called HIV-II
• Retrovirus
• Virus contains a single stranded RNA
• Also have reverse transcriptase enzyme which enable the virus to convert RNA to DNA (most viruses DNA to RNA)

Infectious Process

• gp 120 protein on the viral envelope bind to CD4 marker of the target cell
• helper T cells
• macrophages (40% of circulating monocytes)
• lymph nodes
• skin
• some organ cells (like GI, cause for wt.loss
• some B lymphs

Cont.

• After binding to the CD4 receptor site the virus injects its core into the target cell
• RNA to DNA
• HIV genome becomes integrated into the host cell DNA
• Virus will be duplicated with the host DNA when the cell divides

Cont.

• At this stage HIV becomes permanent
• production of new virus is sporadic and only in a few cells

HIV Infection Patterns

• Pattern I
• Found in North and South America, Western Europe, Scandinavia, Australia, and New Zealand.
• Primarily a disease of homosexuals and IV drug users
• Male to female ratios vary from 10:1 to 15:1

Pattern 2

• Africa, Caribbean, and areas of South America
• Primarily a heterosexual disease
• Male to female ratios equal

Pattern 3

• Eastern Europe, North Africa, Middle East, Asia and the Pacific (Excluding Australia and New Zealand)
• Few cases
• Infection comes from contact in pattern 1 or 2 countries.

HIV 2

• Cross reaction between HIV 1 and HIV 2
• Since 1991 combination test screens for HIV 1 / 2

Cont.

• Transmission of virus is through blood and body fluids (blood, semen, and vaginal fluids)
• Early phase of infection may last from many months to many years
• 2 to 10 years after infection the virus replication flares up again
• End stage is AIDS

AIDS

• Characterized by neoplasms and or opportunistic infections ( Kaposi’s sarcoma and Pnuemocystis carinii are the hallmark of AIDS) See page 301 for more
• In developed countries 50% of patients diagnosed with AIDS die within 18 mths. 80% within 36 mths.

Antibodies

• Window of seronegativity exists anywhere from 6 to twelve weeks or longer
• Anti p24
• Anti gp 41

Lab Testing

• Enumeration of CD4 helper T cells done by flow cytometry
• EIA for screening
• Western Blot for confirmation looks for bands of gp 41 and or p24