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AIDS. Dr. Amitabha Basu MD. Etiology. Human Immunodeficiency Virus Name : retrovirus HIV-1, HIV-2 First described in 1981. Note the central core and the outer envelope. Target cells of HIV. CD4 cells Macrophages Dendritic cells Microglial cells. Type of HIV infectivity.
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AIDS Dr. Amitabha Basu MD
Etiology • Human Immunodeficiency Virus • Name : retrovirus HIV-1, HIV-2 • First described in 1981
Target cells of HIV • CD4 cells • Macrophages • Dendritic cells • Microglial cells
Type of HIV infectivity • Macrophage-tropic (M-tropic) strains • M-tropic strains use CCR5 of macrophage/ monocytes • T-tropic strains • T-tropic strains bind to CXCR4 of T cells If these receptors are not present patients are resistant to HIV infection !!!!!
Infection: entry of HIV through damaged mucosa followed by underlying process
General Pathogenesis – 1 of 2 • gp120 of HIV binds with CD4+ T cell. • Then the HIV enter CD 4+ cell with the help of gp 41. • Formation of proviral DNA by reverse transcriptase: • It can remain latent for years • Or, it can start virion production. • Host cell (CD 4+) lysis occur due to this new virion. • Reduction in number of CD4+ cell→ infection.
General Pathogenesis – 1 of 2 • Widespread lysis of CD4 cell produce : Depletion of CD4 cells. • Altered CD4 : CD8 ratio. • Loss of CD4 cell: Failure of Humoral immunity and cell mediated hypersensitivity reaction.
How HIV reaches Brain ? • HIV infect macrophage. • Macrophages acts as a reservoir and vehicle for HIV to reach CNS. • In brain HIV infect neural cells.
Aids and disease • Opportunistic infection: Mycobacterium avium intercellulare, Pneumocystis carinii, CMV, Cryptococcus neoformans, toxoplasmosis etc. • Tumors : Kaposi's sarcoma (KSHV, HIV), B cell Non Hodgkin's lymphoma. • CNS : Opportunistic Infection, Primary Lymphoma, AIDS –dementia complex.
Pneumocystis carinii: commonest in lung Gomori methenamine silver stain
CMV inclusions in lung are seen here microscopically. Cytomegalovirus may cause disseminated disease, although, more commonly, it affects the eye and gastrointestinal tract
Mycobacterium avium complex (MAC): Acid fast stain Patients with AIDS have reactivation of latent pulmonary disease as well as outbreaks of primary infection.
Candida albicans is seen here as an invasive process in the esophagus with PAS staining. Candidiasis is the most common fungal infection in patients with AIDS. Upper respiratory tract. Oral cavity.
Cryptococcus neoformans (common in CNS) : narrow-based budding seen in CSF: India ink preparation. T. gondii, another frequent invader of the central nervous system in AIDS
Histoplasma capsulatum in macrophage of Lympnnode,also involve brain
Non-Hodgkin's lymphomas seen in the central nervous system with AIDS are essentially clonal expansions of Epstein-Barr virus infected lymphocytes
Slims disease • Central Africa, health workers diagnosed a disease causing severe weightloss and diarrheoa, which they called 'SlimsDisease' . • Agent: Cryptosporidium, Isospora belli, or microsporidia, Salmonella .
Heart • Infective endocraditis: Staphylococcus aurous/CMV. • Myocarditis: Trypanosoma cruzi
Diagnosis • CD 4 cell count below 200 cell/ micro liter. • ELISA • Western blot.