“The evolution of HIV is very extended”: Academician Vadim Pokrovsky on new strains of the human immunodeficiency virus

- Recently there have been publications about a more contagious variant of the human immunodeficiency virus detected in the Netherlands - what is already known about it?

Will the new strain increase the spread of the disease?

- This variant of the pathogen has been known to scientists for ten years, if not more, it has already been encountered before.

And since it has not yet spread, it means that it is not particularly contagious.

It's just that when researchers isolate a new strain, they usually immediately conclude that it is highly virulent.

But often the increased contagiousness can be explained by other factors, the peculiarity of the social group where this version of the virus begins to spread.

For example, when a new type of drug began to spread among young people in Siberia, at the same time a new version of the virus was detected in the region and a conclusion was made about its high contagiousness.

However, in reality, the reason for its rapid spread was not the properties of the virus, but its appearance in a group of young drug users who were not previously infected with HIV.

Their massive infection with the virus was mistakenly regarded as a consequence of its high ability to spread.

In Western Europe, and even in Russia, a new type of drug has also recently begun to spread - a stimulant that increases sexuality.

And it could also affect the rate at which HIV spreads.

Although in reality, the frequency of contacts between people who use this drug could simply increase.

• Vadim Pokrovsky

• © Photo from personal archive

These are epidemiological factors: in some groups the virus spreads faster, in others it spreads more slowly.

So far, there are no grounds for concern in connection with information about a new strain.

If for ten years it has not been particularly actively spread in the Netherlands, then there is no reason to think that it will spread to Russia and begin its march.

- The HIV virus as a whole is extremely variable, after entering the human body, it constantly mutates.

How far can these mutations go?

For example, can HIV be transmitted through the air?

- Such a probability is extremely small, it is almost impossible.

There are very big differences between viruses that are transmitted by airborne droplets and sexually or with blood, they have completely different specifics.

Fearing that the way the HIV virus will be transmitted is like thinking that an elephant will grow wings and start flying.

To do this, there must be a huge change.

Figuratively speaking, it will no longer be an elephant, but a pterodactyl.

- Given that the HIV virus actively mutates, why does the disease not change?

After all, for example, the coronavirus has changed a lot in just two years.

- Speaking in general, although the coronavirus has changed, it has also changed within certain limits.

Mutations of viruses still do not go beyond some limits, otherwise a new pathogen will simply appear that is not related to the original version.

Evolution may lead to the formation of new species, but many of them will be dead ends, unable to spread.

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- There is a theory that viruses such as HIV should eventually lose their lethality with an increase in contagiousness.

Why does this principle not work in the case of HIV?

- The fact is that the evolution of HIV is very extended in time.

The virus spreads very slowly, but if a person is still infected, the virus will remain with him for life.

And this person will be able to transmit the infection several times in his life to other people.

So HIV is not transmitted very intensively, in nature, the main route of transmission for the virus is sexual.

Therefore, he does not need to change, for him the situation is already favorable.

- If I understand correctly, it is precisely the variability of HIV that prevents the creation of a vaccine against it.

But has any experience been gained that could be useful in the development of vaccines against this disease?

- The variability of the virus is one of the factors that hinder the creation of a vaccine, but not the main one.

The main reason is that people simply do not develop acquired immunity to HIV, unlike most infections.

For example, a person who has been ill with measles receives immune protection against the disease for decades.

In the case of HIV, a person is simply not able to recover, therefore acquired immunity is not formed either.

No matter how many HIV vaccines they tried to make, they all turned out to be powerless against the virus.

Apparently, a very special approach is needed to create an effective vaccine.

In addition, the virus is really constantly changing, forming different subtypes that gradually replace each other in different regions, countries and social groups.

And while we are trying to create a vaccine against one subtype, another one is coming to replace it.

For example, in homosexual men, subtype "B" still predominates.

At the same time, there are many infected drug users in Russia, among whom subtype “A” is common.

So the vaccines being developed against strain B are unlikely to be effective in Russia for preventing HIV among drug users.

And in recent years, other strains have penetrated the country, for example, subtype “C” has penetrated the Far East.

However, the main problem, I repeat, is that it is impossible to form acquired immunity to HIV, because HIV infects and uses the cells of the human immune system for its own purposes.

“Due to the coronavirus pandemic, vaccine research is booming.

Can the experience gained under these conditions somehow help in the development of a vaccine against HIV?

- Yes, now in this area they are already trying to apply the approaches that are used to produce vaccines against coronavirus.

Based on this methodology, even using production lines, they are trying to create an HIV vaccine.

But, unfortunately, there is little chance that it will be effective.

Although, of course, each new vaccine brings something new to the study of HIV infection.

Is it true that about 10% of people have natural immunity to HIV due to a certain mutation?

- Yes, although acquired immunity to HIV is not formed, some people have innate immunity.

A certain mutation leads to the fact that on the cells to which the virus usually attaches, there are no receptors necessary for this.

This mutation is predominantly common in Northern Europe, including Russia and the UK.

In the heterozygous form - transmitted by only one parent - it occurs in 20% of the population of these regions.

If a person with this form of mutation becomes infected with HIV, it takes longer to develop AIDS than in the average person.

If both parents were carriers of this gene, then the child becomes completely immune to HIV infection, at least sexually.

There are about 1% of such people in Northern Europe and Russia.

The further south, the less common this gene.

- Can a person, by passing tests, find out if he has such a mutation?

- Yes it is possible.

Some laboratories have even attempted to introduce such a test into their list of services.

But I am personally against such testing, because it will not work.

Suppose a person learns that he is immune to HIV, and then what?

He will lose his vigilance, he will behave more risky, he will be able to get hepatitis and other diseases.

- Previously, a study was conducted in the UK that showed that the average life expectancy of carriers of a mutation that protects against HIV is lower than that of ordinary people.

— Yes, that's it.

In the UK, the collection of statistics and the methodology for conducting such studies are very well established.

And such results are quite possible, since there is never a guarantee that a mutation will not have a negative effect, even if it also has some benefit.

- The experience of the Chinese scientist He Jiankui, who genetically modified twin girls, was an attempt to reproduce this particular mutation?

- Yes, the idea, apparently, was to somehow introduce this gene into embryos.

As a scientific experiment, this is interesting, but the parents of these children simply took antiretroviral drugs if they were infected.

In this case, the children would also be born healthy.

In general, the story of He Jiankui's experience is rather dark, it is possible that there is an element of fiction in it.

First of all, it is not clear why it was done at all.

• He Jiankui

• © SC Leung/SOPA Images/LightRocket via Getty Images

Although about 15 years ago, a successful experiment was carried out on the "Berlin patient" - this is how they later began to call Timothy Brown, a man who received a bone marrow transplant for the treatment of leukemia.

He was infected with HIV, and the doctors guessed to transplant his bone marrow from a donor immune to the virus.

As a result, the recipient eventually also recovered from HIV: his immune cells were replaced by cells immune to the virus.

This man died about ten years after the operation, but not from AIDS, but from a relapse of leukemia.

- A similar case was recently reported in the United States - where a woman was cured of HIV with stem cells.

Can this approach be scaled to many patients?

— The problem is that it is difficult to find such a donor.

Therefore, over the past 15 years, few such operations have been carried out: maybe a few dozen - no more.

And most of them failed.

However, the case recently reported in the media is a successful example of such a procedure.

The method is very interesting for science, but unsuitable for mass implementation.

Now there are about 40 million people infected with HIV in the world, it is almost impossible to find suitable donors for everyone.

Not to mention the fact that a bone marrow transplant is very expensive - around $100,000. 

Therefore, many groups of researchers are trying to develop alternative HIV treatment options to donor transplantation.

For example, there is such an idea: to take bone marrow cells from the patient himself, modify them to be immune to HIV, and then plant them back.

In this case, the problem of compatibility will disappear, because own cells will not be rejected.

Gene transfer is done with the help of viruses - for example, adenovirus already known from COVID-19 vaccines.

• Elements of the human immune system

• Gettyimages.ru

Experimentally it was possible to obtain such cells immune to HIV.

Moreover, in this case we are talking about changing not one gene, but several, which also reduce susceptibility to HIV.

However, there is a great difficulty in obtaining permission to conduct experiments of this kind on humans.

- Because we are talking about partial editing of the human genome?

- Undoubtedly.

But not the entire genome, but only a set of genes of some cells.

If they are transplanted into a person, his main genome will not change and he will not be able to transmit this quality by inheritance.

However, there are risks of tumors, risks of some unforeseen mutations.

Therefore, in Russia, experiments are still being conducted on animals, and it will be possible to move on to human trials no earlier than in a few years.

This is one of the methods of gene therapy, but there are other approaches: for example, gene editing.

At one time, people borrowed antibiotics from fungi, which, with the help of these substances, fight bacteria.

And then it turned out that there are also viruses that infect bacteria - they are called bacteriophages.

They are quite common, and people are already trying to treat some diseases with them, including those caused by antibiotic-resistant bacteria.

At the same time, bacteria also learned to fight these viruses so that they do not integrate into their genome.

Bacteria have a special system that cleans their genes from foreign nucleotides.

And we can, in turn, use this technique to treat viral diseases, as well as edit human genes with its help.

Such developments are being carried out all over the world, but it is still difficult to say how successful.

Our Central Research Institute of Epidemiology of Rospotrebnadzor also has a group that is engaged in similar research.

- At what stage after HIV infection can such therapy help a person if it passes all the necessary tests?

- The treatment process will be very difficult, because such drugs will have to clean all infected cells from the virus.

Perhaps in the future, genetic prevention will be introduced: the genetic code of people who have not yet become infected with HIV will change, by analogy with vaccination.

Although, of course, such procedures cannot be called vaccinations, since we are not talking about inducing an immune response.

Genetic formation of resistance to HIV or other diseases is an interesting line of work.

Although dangerous, because it is difficult to predict the consequences of interference in human genetics.

— Is there any progress in the fight against HIV over the past decades, any serious progress?

“After the introduction of combination antiretroviral therapy 25 years ago, we can talk about the successful treatment of the disease, although its causative agent remains in the human body.

But such drugs need to be taken for life, besides, they have certain side effects.

Therefore, the search continues for drugs that would cure completely.

Along with gene development, the possibility of treating HIV with highly effective antibodies that were previously discovered is being discussed.

They can be produced in large quantities.

In principle, such antibodies can be administered to patients instead of chemicals, and they can also be used to prevent infection.

The only problem is that these antibodies, after being introduced into the body, are quickly destroyed and provide relatively short-term protection.

But if you learn how to inject into a muscle or under the skin of a person some kind of biological construct that will constantly produce these antibodies, then this could provide something like passive immunization.

Such studies are also underway.

But all work in this direction is significantly hampered due to the need to conduct long-term clinical trials.

And so far, the most reliable means of contracting HIV infection remains a condom.