Human Immunodeficiency Virus:
Pathogenesis — HIV-1 infects lymphocytes with the CD4 marker. CD4 lymphocytes are involved in cell-mediated immunity and their depletion also impairs B-cell activation. –> AIDS
Transmitted by sexual contact, IV drug use, breast-feeding, needle-stick injuries
Clinical Manifestation:
Acute HIV infection: fever, fatigue, rash, headache, lymphadenopathy, pharyngitis, myalgia, GI upset, night sweats, aseptic meningitis, oral&gential ulcers. within days to weeks after exposure.
Prolonged Asymptomatic Period: body makes antibody to the virus in 3-4 weeks and enters a period with no symptoms (up to 12 yrs) but the HIV-1 RNA and antibody levels can be measured.
AIDS: immune deficiency, high levels of the virus, opportunisitic infections.
Physical Examination:
-look for weight changes, skin lesions (signs of opportunistic infections), fever.
-weight loss of more than 10%
-Pneumocystis carinii pneumonia most common cause of fever. patients may have normal lung function even with active infection.
Opportunistic infections: sinusitis, oral thrus, CMV retinitis, toxoplasmosis, cryptococcal meningitis, Kaposi sarcoma, psoriasis, seborrheic dermatitis, molluscum contagiosum, herpes zoster
Diagnostic:
1) ELISA (enzyme-linked immunosorbent assay) & Western blot test.
-a positive ELISA should be followed up with a Western blot test which will react with 2/3 different antigens. It is inacurate in first 3-4 weeks after HIV exposure.
2) PVL (plasma viral load): can detect as early as 11 days. can determine the stage of disease by looking at CD4 count and PVL.
Treatment:
-Asymptomatic & CD4 count is above 350/mm3: don’t treat it
-Asymptomatic but CD4 count is less than 350/mm3 or PVL is elevated (30k copies/mm3 by B-DNA or 50k copies/mm3 by PCR): retroviral therapy
-3 types of drugs: NRTIs (nucleoside reverse transcriptase inhibitors), PIs (protease inhibitors), nNRTIs (nonnucleoside reverse transcriptase inhibitors).
-Regimen of 3 total drugs: 2 NRTIs (zidovudine+didanosine OR zidovudine+lamivudine) + 1 PI (indinavir) or 1 nNRTI (efavirenz)
– for pregnant mothers, C-section and Zidovudine therapy can reduce incident in child. Babies will have positive test (Immunoglobulins cross placenta) and should be given ziduvidine for at least 4-6 wks with repeat tests every month until 2 negative tests.