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HUMAN IMMUNODEFICIENCY VIRIS (HIV). These are RNA viruses that belongs to the family Retroviridae ( Retro means reverse). Members of this possess reverse transcriptase enzyme. Morphology: It is a spherical enveloped virus measuring about 90-120 nm. ANTIGENIC VARIATION:
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HUMAN IMMUNODEFICIENCY VIRIS (HIV) These are RNA viruses that belongs to the family Retroviridae (Retro means reverse). Members of this possess reverse transcriptase enzyme. Morphology: It is a spherical enveloped virus measuring about 90-120 nm.
ANTIGENIC VARIATION: • . Two distinct antigenic types of HIV have been identified – HIV1 and HIV2. Antigenic variation occurs within both HIV1 and HIV2. SOURCE OF INFECTION patients and carriers MODES OF TRANSMISSION: • Sexual contact. • Parenteral transmission. • Perinatal transmission.
Path of the Virus HIV exposure at mucosal surface (sex) Day 0 Virus collected by dendritic cells, carried to lymph node Day 0-2 HIV replicates in CD4 cells, released into blood Day 4-11 Virus spreads to other organs Day 11+
Stages of HIV Infection There are four stages : • Acute HIV infection: Characterised by acute onset of fever, malaise, sore throat, myalgia, arthralgia, skin rash and lymphadenopathy. • Asymptomatic infection: All the infected individuals go through a stage of symptomless period. • Persistent generalised lymphadenopathy (PGL): Characterised by enlarged lymph nodes more than 1 cm at two or more extra-inguinal sites for at least three months. • AIDS : It is the end stage, patient develops symptoms like fever, darrhoea, wt. loss and opportunistic infections.
Some imp opportunistic infections and malignancies : • Bacterial : Mycobacterial infections, Salmonellosis • Viral : CMV, Herpis simplex, VZV, EB virus. • Fungal : Candidiasis, Cryptococcosis, Pneumocystis • Parasite : Toxoplasmosis, Cryptosporedosis. • Malignancies : Kaposi’s sarcoma, B-cell lymphoma
Risk factors : • AIDS in adults : A. Sexual ( Genital, anal ) B. Intravenous drug abusers C. Haemophiliacs D. Blood transfusion • Paediatric AIDS A. Infected mother B. Transfusion of blood or blood products .
Laboratory diagnosis : Diagnosis includes specific tests for HIV and tests for immunodeficiency. • Specific tests: A. Antigenic detection. B. Antibody detection. C. Viral isolation. D. PCR. 2. Tests for immunodefiency: A. Total differential count. B. Skin tests for CMI 3. Test for opportunistic infections:
Prophylaxis : “No effective vaccine available due to high rate of mutation.” Number of vaccines are on trial ( Whole virus, subunits based on envelope). antiretroviral therapy: highly active antiretroviral therapy ( HAART) is effective in inhibition of HIV replication. Post exposure prophylaxis : Most exposures will not lead to infection. Zidovidin 300 mg BD and Lamivudine 150 mg BD are used in combination for four weeks.