Causes of HIV / AIDS

The causative agent of HIV infection. The human immunodeficiency virus (HIV) belongs to the family of retroviruses (Retroviridae). The retrovirus family allocate two podsemeystva- Oncoviruses (Oncoviridae) and slow lentiviruses (Lentivirus). The first subfamily includes viruses that cause leukemia: T-cell leukemia and chronic hairy cell leukemia, as well as leukemia virus of cattle.

HIV belongs to the subfamily of lentiviruses. Currently, 7 species of lentiviruses are known, of which 6 are pathogenic for animals and only one (HIV) causes human disease.

Currently, 3 serotypes of the virus are described: HIV-1, HIV-2 and SIV, differing in structural and antigenic characteristics. The greatest epidemiological significance is HIV-1, which dominates the modern pandemic and is most widespread in Europe, including in Ukraine. HIV-2 is found primarily in West African countries.

HIV virions have a round shape with a diameter of 100-120 nm. The viral particle is a core of conical shape surrounded by a shell (envelope). HIV belongs to the class of retroviruses, which implies the transfer of hereditary information in virions in the form of RNA. In the structure of the viral particle, the central part of the retrovirus, in addition to two copies of the positive RNA strand, contains DNA-binding proteins and reverse transcriptase used to transfer the RNA of the virus into DNA for further integration into the genome, as well as transcription of the virus DNA by the eukaryotic cell apparatus.

Of fundamental importance is the structure of the membrane, which is a fragment of the membrane of the host cell. In the lipid layer of the envelope, glycoproteins with a molecular mass of 160 kilodaltons (Kd), gp 160, are localized, which play a key role in the mechanism of "recognition" and penetration into the target cell. The glycoprotein consists of an outer (epimembrane) part with a molecular mass of 120 Kd (dr120) and a transmembrane part of -41 Kd (gp41).

The core shell contains a protein with a molecular weight of 24 cd (p24). Between the outer shell of the virion and the nucleoid there is a framework consisting of a matrix protein 17kd (p17). In the nucleoid there are two single-stranded RNA molecules, a complex of enzymes (reverse transcriptase (revertase), integrase, RNase H, proteinase) and genes responsible for the production of envelope proteins ,. Enzymes and nuclear structures.

The limited size of the synthesis of RNA poses high demands on the saturation of the genetic material contained in the virus. Usually, the retroviral genome does not exceed 10 kb in length.

The HIV genome consists of 9 genes: 3 of them are structural, characteristic of all retroviruses, and 6 regulatory ones. One of the regulatory genes (nef) slows down the transcription of viral genomes. The synchronous function of the two genes (nef and tat) causes the replication of the virus, which does not lead to the death of the cell infected with the virus.

In addition, HIV is characterized by exceptionally high genetic variability. Like all retroviruses, HIV is characterized by high variability in the human body, as the infection progresses from asymptomatic to manifest, the virus evolves from a less virulent to a more virulent variant.

Under natural conditions, HIV can persist in dried biosubstrate for several hours, in liquids containing a large number of viral particles (blood, ejaculate) - for several days, and in frozen serum the activity of the virus persists for several years. The low concentration of HIV in other biological fluids determines its rapid inactivation.

HIV is not stable in the external environment. Heating to 5 ° C for 10 minutes results in a 100-fold decrease in the infectious titer of the virus, at 70 ° -80 ° C, the nirus dies after 10 minutes. The virus dies with a sharp change in the reaction of the medium (pH below 0.1 and above 13), and also under the influence of disinfectants in concentrations commonly used in laboratory practice, 70% ethyl alcohol, 6% hydrogen peroxide solution, 0.5% sodium hypochlorite solution , 1% solution of glutaraldehyde, 5% solution of lysol, ether, acetone).

The source of HIV is a person in all stages of the disease. The virus is found in the blood, sperm, cerebrospinal fluid, breast milk, menstrual blood, vaginal and cervical secrets. In saliva, lacrimal fluid, urine, the virus is in a small amount, insufficient for eraging.

Ways of HIV transmission

There is a sexual, parenteral and vertical route of HIV transmission.

Sexual transmission of infection is realized with heterosexual and homosexual intercourse. The likelihood of infection increases with inflammatory diseases of the genitals. It is believed that the share of the sexual way of transmission of the virus is currently more than half of all cases of infection. The ratio of infected men and women changed over time: at the beginning of the epidemic - 5: 1, then 3: 1, now this figure has approached 2: 1.

The parenteral route of infection is found mainly among drug addicts who inject drugs intravenously. The factors of HIV transmission in this case can be both common syringes and needles, and the drug itself. Infection is possible with transfusion of contaminated blood, its drugs, organ and tissue transplants, and the use of HIV-contaminated medical equipment.

Vertical transmission of HIV occurs from an HIV-infected woman to a child during pregnancy and childbirth, as well as during breast-feeding from an infected mother to a child and from an infected child to a nursing woman. In the absence of prevention of perinatal HIV transmission, the risk of HIV infection is 30-40%. The probability of infection of a child with breastfeeding is 12-20%.

Contact-household, airborne transmission routes for HIV infection are not described. Blood-sucking insects do not play a role in the spread of infection.

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