With maximum efficiency
Russian scientists have "twisted" the effectiveness of the DNA vaccine against HIV to the maximum
They clarified which parts of the gene of the main enzyme of the immunodeficiency virus cells of the immune system react most strongly, and also developed ways to enhance the protective reaction in response to them.
The staff of the V.A. Engelhardt Institute of Molecular Biology of the Russian Academy of Sciences optimized a prototype of a DNA vaccine against a form of human immunodeficiency virus (HIV-1) resistant to the action of antiretroviral drugs. To do this, they used the reverse transcriptase gene – an enzyme that ensures the accumulation of immunodeficiency virus DNA in infected cells. Biologists have studied which parts of it are most reliably recognized by lymphocytes and trigger an immune response. A scientific article based on the results of the study was published in the journal Scientific Reports.
HIV infection is one of the most common in Russia and in the world. At the end of 2016, according to WHO, there were 36.7 million people affected by the immunodeficiency virus on the planet. HIV weakens the body's defenses, which is why such ailments become deadly for the infected, which practically do not occur in people without HIV: their pathogens are suppressed by lymphocytes and other cells of the immune system "at the root". It is impossible to completely eliminate HIV particles from the infected person's body, but now there are medicines – antiretroviral drugs that can suppress the reproduction of the virus and its spread through the body. The problem is that HIV is continuously evolving, "learning" to get away from the effects of such drugs. Because of this, it is necessary to develop all new means of antiretroviral therapy.
In order to slow down the emergence and spread of HIV resistance to appropriate drugs, the authors of the article analyzed which mutations in one of the genes of this virus most often provide it, and created variants of this gene that, when introduced into the human body, cause the most powerful immune response.
Scientists have optimized the structure of the revertase enzyme gene (aka reverse transcriptase). This protein reads the sequence of RNA nucleotides of the immunodeficiency virus and builds the corresponding (complementary) DNA. In the cells of bacteria, animals and other organisms capable of independent vital activity, the reverse process occurs – reading information from DNA and building RNA on its basis. It's called transcription. Accordingly, revertase produces reverse transcription. HIV reproduction is impossible without it. Many drugs against this virus stop the formation of new viral particles precisely by blocking revertase.
The researchers used two variants of the revertase gene – a "wild type" that can be blocked by antiretroviral drugs, and a mutant, resistant to the action of drugs of this class. Both genes had their ability to spread throughout the body disrupted, that is, they were made non–pathogenic, and inserted into plasmids - small circular DNA molecules found naturally in bacteria and serving to transfer useful genes from cell to cell. These plasmids were injected under the skin of laboratory mice. They achieved the desired cells by electroporation – the creation of temporary holes in their shells under the influence of an electric field. In some cases, plasmids were injected not once, but twice, and sometimes a signaling substance, cyclic diguanilate, was added to them. The reaction of the mice to the DNA vaccine was assessed by the number of activated CD4+ T-lymphocytes (it is in them that HIV accumulates) and molecules of the antiviral substance gamma interferon. The more of them there were, the more powerful the immune response to HIV was.
Then, various fragments of the revertase protein were injected into the culture of the spleen cells of vaccinated mice – both its "wild" and anti-retroviral drug-resistant forms. So they found out which parts of the reverse transcriptase molecule the immune system is activated the most and which mutations in the gene of this enzyme, on the contrary, suppress the protective reactions of the body.
Having determined such revertase sites and their optimal structure for the immune system, the authors correlated them with the structure of the gene of this enzyme. Using the information obtained during the study, it will be possible to create DNA vaccines that provide the most reliable protection against the human immunodeficiency virus.
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