HIV belongs to the class of retroviruses of the lentivirus family. This family of viruses causes diseases that develop slowly and last for a long time. The genetic material of HIV, like other retroviruses, is represented by RNA (ribonucleic acid), which is a template for the production of proviral DNA (deoxoribonucleic acid).
HIV is transmitted only from person to person. Only humans can be infected with HIV. Once it enters the body, HIV very quickly penetrates blood cells – lymphocytes, which have receptors that have an affinity for HIV, the so-called “CD4+ T lymphocytes”. Some other blood cells (monocytes and macrophages), cells of the central nervous system, rectum, cervix, etc. also have such receptors. Due to the affinity of the virus surface proteins and cell receptors, HIV enters the cytoplasm of the cell. Then, thanks to the reverse transcriptase enzyme, the formation of proviral DNA takes place from viral RNA.
The viral DNA is “embedded” in the genetic material (DNA) of the host cell. After that, the host cell perceives the virus DNA as “native”. The virus becomes part of the cell and remains so until the cell dies. During its life, a cell infected with HIV produces new copies of the virus, releases them into the plasma, other biological fluids and secretions. This reproduction process is called viral replication. New copies of the virus come out of the infected cell, spread in the body, invade other cells, infect them and start reproducing new copies.
During the formation of new viruses, “mistakes” called mutations often occur. The variability of the pathogen leads to the fact that some drugs used to treat HIV infection lose their ability to act on the enzymes of the virus, i.e., the virus develops resistance or resistance to this drug. In order to avoid the development of drug resistance in the treatment of HIV infection, it is necessary to use a combination of several drugs at the same time.
Virus resistance in the environment
- In the environment, when lymphoid cells infected with HIV are dried, viral activity disappears within a few days.
- When cell-free fluid is dried with the addition of human plasma, the virus dies at a temperature of 23-27°C in 7 days.
- In a liquid medium at 23-27°C, the virus remains active for 15 days, and at 36-37°C – 11 days.
- In blood intended for transfusion, the virus survives for years, and in frozen serum, its activity persists for up to 10 years.
- HIV dies quickly when using disinfectants, ultraviolet radiation; when heated above 56°C, it loses activity in 30 minutes.
Swollen lymph nodes are one of the early signs of HIV infection. Lymph nodes the size of a pea or larger usually do not bother a person. Enlargement of the lymph nodes is not associated with acute illnesses and lasts for 3 months or more.
Increased size of the liver and spleen are often observed in people with HIV infection. A pronounced increase in the size of these organs can lead to an increase in the size of the abdomen. Liver enlargement associated with HIV infection is usually not accompanied by the appearance of yellow coloration of the skin and sclerae.
Impaired physical development is manifested by a slowdown in the rate of weight gain and height.
Impaired physical development in the progression of HIV infection leads to the development of wasting syndrome, which is characterized by a loss of more than 10% of body weight, fever and stool disorders for 30 days or more.
Skin lesions are often observed in HIV infection. They can be caused by allergies and various infectious pathogens (fungi, bacteria, viruses).
However, one of the symptoms of HIV infection is an increase (swelling) of the parotid salivary glands. This condition is usually not accompanied by fever and soreness.
The direct effect of HIV on the cells of the nervous system leads to the development of HIV encephalopathy.
The progressive dysfunction of the immune system in HIV infection leads to the fact that microorganisms and viruses – natural inhabitants of the environment (that do not cause disease in people with normal immune system function) – cause diseases in the patient, which are called opportunistic infections (opportunist – opportunist).
One of the manifestations of HIV infection is the appearance of tumors (Kaposi’s sarcoma, malignant lymphoma or lymphosarcoma).