HIV in vitro
Laboratory studies of HIV infection
7 facts about the study of human immunodeficiency virus
under controlled conditionsLeonid Margolis, "Postnauka"
One of the most pressing problems of modern medicine is the fight against HIV.
The epidemic of this infection, which leads to a disease called AIDS, has captured almost all countries, the whole world. To date, the most diverse attempts to at least limit this epidemic, to stop its spread by creating vaccines and subsequent vaccination of the population, as well as other measures, in general, have not been successful.
When the last of the vaccines failed, a consensus decision was made in the scientific community that we do not know enough about the fundamental mechanisms of HIV infection, and this is the most important thing: to fight infection, you need to first understand the fundamental mechanism of infection and develop preventive measures based on this. Therefore, my colleagues and I are dealing with the fundamental problems of HIV infection.
Why is this virus so successful from his point of view? Why, having coped with many other viruses, this virus has not yet been defeated?
1. HIV infection strategyThe main reason is the choice of a very successful strategy from the point of view of the virus, of course.
Firstly, unlike other viruses, it infects exactly those cells that are designed to fight infection. Secondly, he chose a successful sexual reproduction path – this is the preferred method of reproduction of the virus. It is important that it infects not just immune cells that are designed to fight it, but also activated cells. That is, when another virus infects the body, the cells of the immune system are activated and destroy the virus or cells infected with the virus. However, HIV attacks activated cells, that is, those that are designed to destroy it – this is its advantage.
For a long time it seemed that the disease proceeds as follows: the virus infects a person, there are some mild symptoms, and then it disappears, and a months-long, sometimes even a long-term latent phase occurs. But then it turned out that this was not the case. The concept of the latent phase appeared because it was based on the blood analysis of sick patients. It turned out that during this phase, the virus really disappears from the blood, but it continues to multiply and destroy lymphoid tissue, lymph nodes, which are the centers of the immune response to infection.
2. Study under controlled conditionsWhen this became clear, it became clear that it was necessary to study how these viruses multiply not just in suspension in the laboratory or in the blood of a patient, but in tissue.
Therefore, the group I lead, my colleagues and I have created a laboratory system that allows us to study the reproduction and pathogenesis of this virus in lymphatic tissues under controlled conditions. For various technical and ethical reasons, it is almost impossible to study how the virus multiplies in the tissue of a sick person. A blood test can be taken without any consequences, but it is difficult to penetrate into the tissue and in many cases impossible.
It follows from the history of medicine that the mechanisms of most human diseases became clear when either animals or other laboratory models were created to study them, because for science it is necessary to control all conditions for studying any process. Of course, this is impossible in a person. There is practically no animal model of HIV infection, although there is a similar virus that infects monkeys, but unlike many other viruses, HIV infects humans, and only humans.
We have created a system that consists of pieces of lymphatic tissue. To create it, you can take operative material, for example, after tonsillectomy or adenectomy, when the glands or adenoids are cut out. Basically, the glands are cut out in children according to the indications of frequent colds. We take these pieces, know how to cultivate them in the laboratory for two to three weeks, artificially infect them with HIV and see how the pathogenesis occurs. Along the way, we got some pretty interesting data.
3. Application of the laboratory modelThis system is also used to test various antiviral drugs, because HIV infection studies are very expensive.
Any clinical trials require many years of preparation, since the drug goes through different stages of testing before it is administered even to healthy volunteers to check for toxicity. Our system allows us, without any problems related to ethics, with permits, to see in preclinical trials how this medicine acts on the virus.
In addition, such a system is very useful and gives a lot of information about virus infection, transmission, as experts say, that is, how the virus is transmitted from an infected person to a healthy one, for example from a man to a woman. We have a system that allows us to cultivate, for example, the cervix, where infection occurs when the virus is transmitted from a man to a woman sexually.
4. Coinfection of HIV and herpesWe have received many interesting results, in particular, about the process of infection with the virus.
HIV infects activated immune cells, some of them pass into this state when infected with a virus, but can also be activated by infection with another virus. That is why other pathogens, even not as terrible as HIV, for example, herpes viruses for a healthy person, do not pose a danger, activate cells of the immune system, thereby creating new targets for HIV infection.
5. Defeat of the immune response control systemHIV has "invented" a clever strategy: it infects cells, and they begin to secrete special substances – cytokines, which activate neighboring cells.
Consequently, a neighboring cell that was previously at rest and therefore could not get infected with HIV becomes a target for the virus. Thus, HIV prepares the ground for infection by itself and spreads into the tissues. In addition, both HIV infection and infection of related viruses, activating cells, cause the production of so-called interleukins. Interleukins are soluble substances that are secreted by some cells, absorbed by others during the normal immune response. This is a very complex "degenerate" system, in which some interleukins can be replaced by others, and they regulate the normal immune response. This complex system of interleukins changes greatly under the influence of HIV infection in both a sick person and a chronically ill person.
We found, for example, that one strange cytokine, called interleukin-7, is elevated in the seminal fluid of HIV-infected men. Why he was promoted there is unknown.
Knowing the nature of this virus, you can think that it does nothing in vain. Most likely, the entire cytokine system of a sick person is changed by the virus in its favor, otherwise evolution would not have allowed it to be so successful. Perhaps more pathogenic viruses are being selected than if it were without interleukin. It turned out that this interleukin contributes to the transmission of the virus and infection of cervical tissue.
We conducted a simple experiment: if you take the cervical tissue of a healthy woman and infect her with HIV in a Petri dish, add this interleukin-7 there, then infection occurs much more effectively. Based on this work, we have the following hypothesis: perhaps men with elevated interleukin-7 infect their partners more easily than those with less interleukin.
6. Resistance to HIV infectionThere is a big problem with this: there are husband–wife couples recruited for clinical trials who are in constant communication, do not cheat on each other, however, without knowing this and without protection, men can be infected with the virus, and women for several years, often many years, do not get infected.
When this was discovered, they thought that these women had some kind of defense mechanism and maybe it would be possible to reproduce it in everyone else. We studied for a long time, but we didn't find anything so special about these women.
In the light of our research, we think that the absence of infection, transmission of the virus from such men is precisely because they have impaired those cytokines that contribute to infection. At the moment, this is only a hypothesis that may be incorrect.
7. Treatment of HIV and herpes coinfectionAs already mentioned, herpes viruses help the transmission of HIV and accompany infection.
For quite a long time, people infected with both viruses have been prescribed therapy against the herpes virus, since it is clear that one disease is better than two. In this case, the standard drug acyclovir, discovered in the 70s, is prescribed - this is the most effective remedy against the herpes virus. Acyclovir acts on several herpes viruses, including the one that usually accompanies HIV infection, herpes virus 2.
In a laboratory system for HIV research, we can study the mechanism of interaction of viruses. When we started infecting pieces of tissue with the immunodeficiency virus and herpes virus, we wanted to reproduce the effect of acyclovir on this system in a controlled laboratory case. It turned out that this is possible: the use of acyclovir suppresses herpes virus infection and leads to the suppression of HIV. Since we can carry out control in our system, it turned out that acyclovir can directly affect HIV infection without any herpes 2.
We are currently conducting clinical trials, they are still far from completion, so it is impossible to recommend acyclovir for treatment, but this is one example when a laboratory system allows you to discover something that would be virtually impossible to discover by studying a person. No one can authorize human research, and that's right. Also, this situation is an example of how a controlled laboratory system allows you to detect the mechanisms of interaction of the virus, viral pathogenesis, which are necessary to combat the virus and develop preventive methods.
About the author:
Leonid Margolis – Doctor of Biological Sciences, Professor of the Faculty of Bioengineering and Bioinformatics
Lomonosov Moscow State University.
Portal "Eternal youth" http://vechnayamolodost.ru27.01.2015