Research on monkeys showed that a weakened measles virus, which is part of the vaccines, infect only the respiratory tract and immune to it gradually fades away. At the same time, the wild-type virus is widely distributed on all organism, reproduces in immune cells where its RNA remains for at least a month. As a result, the body produces more antibodies and long-lived plasma cells specific to the virus, and the immunity lasts for life. Article published in the journal Science Translational Medicine.
The measles virus leads to the development of lifelong immunity in those who contracted it and survived. This virus only eight proteins, the immune system attacks them all, but the main protection is provided by antibodies to the protein , the hemagglutinin. This substance helps the virus to attach to receptors on human cells, and if the “occupy” it with antibodies, the infection will not be able to enter the cells.
Catching the virus and forcing it to grow in cell culture, the scientists were able to obtain a weakened form of the infectious agent and make on its basis the vaccine. Antigens that are the targets of immunity are the same in both types of the virus, wild type and attenuated, but in proteins there are a number of differences. The immune system, which causes the virus in the vaccine, weakerthan that obtained in a natural way: if the second protects the body for decades, the first wanes after 10-15 years.
Study on humans the development of measles virus wild-type, which causes the full disease with severe symptoms and can lead to death, is difficult. A small animal model for measles does not exist, therefore, still are not clear, nor the mechanisms of lifelong immunity, neither the reasons that the weakened virus is not as effective.
A group of scientists from the United States under the leadership of Vanesyan Lin (Wen-Hsuan Lin) from the Higher school of public health, Johns Hopkins Bloomberg investigated the spread of two strains of the virus in tissues of macaque-rhesus (Macaca mulatta). 35 monkeys were infected via the respiratory tract through inhalation, and then followed the spread of the virus and viral RNA.
In macaques that were infected with wild type measles virus, 11 days after infection a rash; this virus was propagated in T – and B-cells of the immune system, and its RNA was detected in the lymphocytes of the animal within one month after infection. The weakened virus does not cause a rash, multiply only in the respiratory tract and do not infect lymphoid cells. The spread of the virus wild type led to the emergence of chemokines and cytokines (substances that regulate immune response) and more specific to the virus antibodies than attenuated form. The difference in the number of antibodies was the result of a greater number of long-lived plasma cells in the bone marrow which produce these antibodies (p < 0.01).