Advantages Of Rectal Vaccination Against HIV

AIDS immunisation is still to be improved. Russian scientists suggest that rectal vaccination could be the most effective prevention of HIV transmission. The work is supported by the Interdepartmental Research and Technical Program “Vaccines of new generation and medical diagnostic systems of the future”.

Researchers all over the world strive to obtain a vaccine preventing AIDS. Most promising are DNA-vaccines, which contain genes of human immunodeficiency virus. These genes function within the human body and synthesize certain viral proteins harmless to human health, and the immune system produces antibodies to those proteins and becomes resistible to a whole virus in case if the latter appears.

The DNA-vaccine is usually prescribed per-orally. One needs to eat quite a lot of DNA, which is very expensive, in order to induce an adequate immune response. Intramuscular injections can cause only a very weak and short-term response. Hence, scientists search for another route of DNA-vaccination that would require a low dose and provide a high specific immune response.

Karpenko and his colleagues from the Research Institute of Biological Engineering of the State Research Centre of Virology and Biotechnology “Vektor” (village Kol’tsovo in the Novosibirsk Region) and the Biological Medicine Centre (St. Petersburg) believe that rectal (anal) vaccination is superior to the other routes.

DNA-vaccine is packed into salmonella cells. Certain weakened strains of this bacterium are not dangerous for human health, but induce the generation of an additional immune barrier, which prevents HIV from penetrating through the mucous membrane into the body. The Russian research team constructed a plasmid carrying the gene of protein GP160 HIV-1 and packed it into salmonella cells. A suspension of these cells was given to mice.

Each mouse received a milliard of salmonellas (one drop of the suspension) either per-orally or per-rectally. All necessary control tests were performed as well. It was revealed that the vaccination does not damage mice’s health. A single treatment with salmonellas carrying DNA-vaccine is enough to induce the immune response: specific antibodies appear in the blood serum of all mice and suppress the HIV-1 development in the infected cell culture, and lymphocytes destroy the infected cells. But, the rectal vaccination induces a much stronger immune response than the oral one.

The researchers explain that as follows. Many of per-orally taken salmonellas perish in the stomach, and others cannot move further than the small intestine. They penetrate through certain cells of the intestine mucosa into lymph nodes and then spread throughout the body with the lymph. Rectal vaccination provides for the appearance of salmonellas in all parts of the intestine, particularly, in the colon having many lymph nodes.

Therefore, the per-rectal treatment makes it possible to use a low dose of vaccine, which is less disturbing for the body. The researchers believe that rectal route of immunisation using DNA-vaccine is quite promising in preventing HIV.