HUMAN IMMUNEDEFICIENCY VIRUS
28th May 2012
HIV-1, the basic pathogen of HIV-infection and AIDS can be found in North and South America, Europe and Asia. HIV has the form of sphere with not more than 100-120 nm in diameter. By its structural organization, it is close to lentiviruses. The virus is believed to be mostly sexually transmitted, heterosexual transmission is very important. The main factors that cause a higher risk of HIV-contamination are homosexual relations and sex promiscuity, including intercourse with drug addicts who inject drugs intravenously. Transplantation and perinatal transmission from mother to baby are less important. HIV-infected patients can be divided into groups according to risk factors and possible ways of transmitting the infection. The ranging of risk groups in most advanced countries is identical – homosexual and bisexual men (43%), heterosexual individuals with drugs taken intravenously (26%), homosexual and bisexual individuals using drugs intravenously (5%), heterosexual individuals (10%), children (1%), recipients of blood, blood components or transplants (2%), hemophiliacs (1%), other people for whom the risk factor has not been determined (6%). Penetrating the blood current HIV infects activated CD4+ (helpers) T-lymphocytes using the CD4 molecule as a receptor. HIV also infects monocytes, macrophages, congenial cells, expressional CD4-like molecules. The contamination of monocytes and macrophages is not accompanied by a cytopathic effect, and the cells become a permissive system for the pathogen. The basic reservoir of HIV in the human organism is lymphoid tissue with the pathogen being continuously reproduced even in the early stages of the symptom-free disease. In the central nervous system, there can be observed disturbed microglial cells. The mechanism of contamination of intestinal epithelial cells has not been discovered yet, the receptors for HIV origination are likely to be membranous glycolipids. Early viraemic stage. In the early stages of the infection, the virus seems to be replicated poorly in the course of different periods. The presence of HIV in the blood can be revealed within different spans of time. Viraemia reaches a high 1-12 days after the contamination and lasts until specific antibodies appear (a period of seroconversion). The analysis of the laboratory data with long-living patients suggests that HIV can be eliminated from the organism only too rarely. Over different time spans (up to 10-15 years) no symptoms of the disease with HIV-infected patients can be revealed. Throughout that period the body defenses suppress the pathogen reproduction more or less effectively. The development of the HIV infection and AIDS is provoked by a progressive defect in the immune mechanisms, especially by decreasing the number of circulating CD4+T cells which is very important to the replication of the integrated HIV. Low doses of cocaine added to the infected mononuclear cell culture intensify HIV replication possibly on account of the increasing synthesis of the monocyte growth transforming beta factor. That mechanism can contribute to the frequency rate of AIDS development with drug addicts. After a symptomless period of variable duration, 80-100% patients develop asymptomatic HIV infection and about 50-100% patients are doomed to develop a clinically pronounced AIDS. At present there can be differentiated five clinical stages of the HIV-infection. The incubation usually lasts 2-4 weeks. The symptoms are similar to those with infectious mononucleosis or a chill. Fever, lymphangitis, a sore throat, myalgia, headache, indisposition and sometimes a maculopapular rash are most common. The symptoms can be manifested with 53-93% patients, however for lack of pathognomonic signs diagnostic mistakes may result. Some primary manifestations with most patients may disappear. However, headache and adenopathy may linger for a long time. Fever, excessive overnight perspiration, feebleness, chronic diarrhea, generalized lymphadenopathy and headache with no specific or opportunistic infection in evidence, are indicative of the fact that a symptomless HIV-infection has turned into a symptomatic one. Diarrhea can most probably result from the HIV contamination of the intestinal mucosa. Kaposi’s sarcoma may develop quite early. The dynamics can show energy and give some other laboratory proof of immunodeficiency. Certain concomitant infections tend to arise, especially oral candidiasis, leukoplakia of oral mucosa, upper and lower respiratory tract infections and periodontium disorders. The basic manifestations of opportunistic infections are pneumocystis pneumonia and toxoplasmosis. Esophageal candidiasis, cryptococcal pneumonia and meningitis, recurrent herpetic infections with general exhaustion in the background often develop.