What kind of disease is AIDS

Ania Varezhkova, Atlas

December 1 is the World Day against Human Immunodeficiency syndrome. Atlas has prepared a story about how this disease develops and how it can be prevented.

Human immunodeficiency virus

This is a small virus that is transmitted through physiological fluids – blood, breast milk, semen and vaginal secretions. The virus cannot exist outside of a living organism, so it is not transmitted through saliva, water, food and ordinary household contacts. Unlike malaria and dengue fever, the virus is not carried by mosquitoes and other insects.

HIV enters the human body, attaches to T-lymphocytes and infects T-cells – the main agents of immunity. From the point of view of the evolution of the virus, this is a very reasonable move – as if the leader of a criminal group was hiding from the police at a police station. There, the criminal can regularly take his sketch from the Wanted board and hang it on the honor board.

Gradually, the virus lures "police officers" to its side and destroys the immune system from the inside.

Under the influence of the virus, the number of cells of the immune system decreases over time. When the number of T-helpers reaches a critical minimum (less than 200/ml), the patient's HIV status is replaced by an AIDS diagnosis.

Acquired immunodeficiency syndrome

AIDS is an irreversible disease in which the patient becomes extremely vulnerable to pathogens. Now the body has almost no protection, and even a small bacterial infection, which it used to easily cope with, can cause death.

It is not the virus itself, but opportunistic infections that manifest themselves only against the background of other diseases that cause the death of AIDS patients. These include tuberculosis, bacterial and fungal infections, Kaposi's sarcoma.

AIDS and related diseases claim the lives of approximately 1.1 million people annually.

Antiretroviral therapy (ART)

HIV–positive patients receive antiretroviral therapy. It consists of several drugs that prevent the spread of the virus and the death of T cells and restrain the progress of the disease for decades. Patients taking antiretroviral therapy have almost zero risk of transmitting the virus, and with certain precautions they can give birth to a healthy HIV–negative child.

Usually therapy consists of 3-4 drugs, each of which acts independently. Some block the receptors and prevent the virus from infecting new cells (which does not affect those cells into which the virus has already penetrated). Others prevent the virus from embedding its DNA into the human genome.

There is no radical treatment for HIV at the moment. Therapy has significantly improved the quality and life expectancy of HIV-positive patients. By 2015, half of the patients had a life expectancy of more than 50 years.

Antiretroviral therapy has several disadvantages. Firstly, drugs have strong side effects: bone marrow depression, liver cirrhosis, pancreatitis.

Secondly, medications should be taken regularly at a strictly appointed time. Omissions cannot be filled with a double dose of medication, and they significantly reduce the effectiveness of treatment. Now scientists are developing a formula for complex ART that could be consumed once a day.

Thirdly, antiretroviral therapy is very expensive. In 2014, the cost of an annual course of treatment in Russia was 65-150 thousand rubles. These costs are borne by the state, but medicines are often not enough, and patients are forced to buy them themselves.

The role of genetics

The CCR5 gene plays an important role in the attachment of the virus to T-lymphocytes. It encodes a chemokine receptor protein that is involved in the immune system. Deletion in a gene (absence of a DNA section) makes it impossible for HIV to attach to the T-cell. People with a variant of the CCR5 Δ32 gene cannot become infected with HIV.

Timothy Ray Brown became the first person to be cured of HIV. During the treatment of leukemia, he received a bone marrow transplant from a donor with the CCR5 Δ32 mutation, which prevents the virus from infecting cells of the immune system.

Only about 1-2% of people have this variant of the gene, and about 18-20% more have this variant found in one allele (this reduces the risk of infection, but does not provide full protection). The percentage of CCR5 Δ32 mutations in the European population is higher: presumably, it also reduced the risk of infection with bubonic plague, which means it gave an evolutionary advantage to its carriers during the plague epidemic in Europe in 1347.

The antiretroviral properties of the CCR5 gene were discovered in 2003 and have become a target for the development of drugs and vaccines against HIV. With the advent of the CRISPR-Cas9 genome editing technology, the first experiments were conducted to remove the virus from an infected organism. At the moment, CRISPR-Cas9 is the most promising technology for combating HIV.

Prevention

Until a vaccine against the virus has been developed, the only way to reduce the risk of infection is to use barrier methods of contraception, sterile needles and syringes (if necessary, injections).

Male circumcision reduces the risk of contracting both HIV and other sexually transmitted diseases. Other means of prevention are also being developed – vaccines, special condoms, postcoital drugs that will reduce the risk of infection after unprotected contact.

Remember:

• HIV is transmitted through blood and semen, but cannot be transmitted through saliva and household contacts

• Antiretroviral therapy can restrain the development of the disease and the spread of the virus

• Using condoms reduces the risk of HIV infection

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