American and Indian scientists have found a possible reason why a virus, which would of the upper respiratory tract via the olfactory tract to reach the brain and cause potentially fatal encephalitis, do not cause nervous system damage, reported in Science Immunology. The fact that microglial cells in the olfactory bulb activate CD8+ and CD4+ T-lymphocytes, as well as presenting T-cells viral antigens. This provides a strong enough immune response to pathogens has not penetrated further into the brain.
The olfactory system — a convenient gateway to the Central nervous system to pathogens: the cells that perceive odors, transmit signals to the olfactory bulbs, and they represent an outgrowth of the brain. Therefore, the viruses are able to strike a nerve cell, after penetration into the upper respiratory tract to get very quickly to the brain and probably cause there are pathological changes. But in reality, this rarely happens. Exceptions are possible in case of the rabies virusthat the sick animal was transferred to the victim by biting her in the face (though it is not respiratory), and viruses SARS-CoV.
Scientists from India and USA under the leadership Mcgavern Dorian (Dorian B. McGavern) from the National Institute of neurological disorders and stroke examined what happens to the cells of the olfactory system in mice when they are infected with vesicular stomatitis virus serotype Indiana, which belongs to the same family as the rabies virus. Animals aged 8-10 weeks were injected with 10 MICS of fluid with the virus (1 × 105 to 4 × 105 blagoobrazov units) in each nostril, and then observed the condition of the cell types: neurons, of microglia and T-lymphocytes using intravital microscopy.
Each cell type has its stained fluorescent dye. One of the dyes showed himself up when the cell changed the concentration of calcium, that has any calcium signals. Vesicular stomatitis virus was expressed green fluorescent protein, making the spread of the pathogen also can be seen. A number of mice, “off” CD8+ T-lymphocytes, CD4+ T-lymphocytes or microglia.