HIV AND AIDS HIV STRUCTURE The HIV particle

HIV AND AIDS

HIV STRUCTURE §The HIV particle is composed of a dense, single-strand RNA core surrounded by a lipoprotein envelope a retrovirus of the lentivirus family. § The. RNA contains reverse transcriptase, which allows the RNA to be transcribed into DNA, which is then integrated into the host's genome. §The cell then becomes an HIV-producing machine. § The receptor in the lipoprotein envelope that allows the HIV to attach to the CD 4+ T cell is named gpl 20 §. As opposed to influenza, the envelope on HIV is highly variable; therefore, it is much more difficult to make a vaccine against it.

HOW HIV INFECTS q. HIV gp 120 envelope glycoprotein binds to the CD 4 receptors and coreceptors (such as CCR 5) on the helper T cells, macrophages, and monocytes. The virus must bind to both the CD 4 and CCR 5 molecule to fuse with the cell. q After fusion, the viral core material enters the cell and is reverse transcribed into DNA that integrates into the human genome and codes for the production of more virion RNA and structural proteins. q. These proteins, after being cleaved by a protease, then combine with the viral RNA and bud off of the cell using the CD 4 cell membrane as a new envelope. q This eventually causes destruction of the CD 4 cells. The CD 4 cells are the major regulator cells in the body; they suppress B lymphocytes and regulate the CD 8 suppressor cells.

HOW HIV INFECTS q. With the decrease in CD 4+ counts, B cells become deregulated and are no longer suppressed, causing a polyclonal increase in total serum immunoglobulins, even though overall antibody function is decreased. q For this reason, infectious diseases in AIDS patients include not only the cell-mediated infections (PCP, viruses, mycobacteria, and fungi), but also those seen with humoral deficiency (pneumococcus, meningococcus, Giardia).

HIV IS TRANSMITTED: ● By sexual contact. ● By exposure to blood or blood products (e. g. drug users, patients with haemophilia or occupationally in healthcare workers). ● Vertically from mother to child in utero, during birth or by breastfeeding.

HIV IS TRANSMITTED:

DIAGNOSIS

DIAGNOSIS

DIAGNOSIS

THE DIFFERENTIAL DIAGNOSIS INCLUDES: ● Acute Epstein–Barr virus. ● Cytomegalovirus. ● Streptococcal pharyngitis. ● Toxoplasmosis. ● Secondary syphilis.

STAGES Following diagnosis, the CD 4 lymphocyte count should be determined. This indicates the degree of immune suppression and is used to guide treatment

NATURAL HISTORY AND CLASSIFICATION OF HIV PRIMARY INFECTION Primary infection is symptomatic in >50% of cases and usually occurs 2– 4 wks after exposure. The major clinical manifestations resemble infectious mononucleosis: ● Fever. ● Pharyngitis with lymphadenopathy. ● Myalgia/arthralgia. ● Headache. ● Diarrhoea. ● Mucosal ulceration. ● Oral and genital ulceration

ASYMPTOMATIC INFECTION : VIRAEMIA PEAKS DURING THIS PHASE AND HIGH VIRAL LOADS PREDICT A MORE RAPID RATE OF DECLINE IN CD 4 COUNT THE MEDIAN TIME FROM INFECTION TO DEVELOPMENT OF AIDS IN ADULTS IS 9 YRS.

AIDS IS DEFINED BY THE DEVELOPMENT OF SPECIFIED OPPORTUNISTIC INFECTIONS, TUMOURS AND OTHER CLINICAL FEATURES THIS IS ACCOMPANIED BY A FALL IN CD 4 COUNT TO <200, AND A CHANGE IN THE SPECTRUM OF ASSOCIATED INFECTIONS.

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