Permanent resident virus in human being and microecology / 中华临床感染病杂志

ABSTRACT

Viruses have been compatible with cells since the origin of life. The absolute dependence on cells leads to formation, development, distribution and evolution of viruses; the existence of viruses must have their long-term host for survival, spreading and extending. Like other species in nature, a group of viruses coexist with humans, which are called permanent resident virus in human being.The immune system of species has the function of anti-microbial invasion. The virus has a special coexistence mechanism with the long-term host. Because the immune system has no function to enter cells to recognize and remove viral nucleic acids, then invading viruses can be residual in cells, and as a recessive existence under the dynamic balance between residual viral replication and immune clearance pressure. This is the normal state of the virus with its long-term host coexisting harmoniously as stakeholders, and it also has been the normal state of all natural viruses after the immune system developed in host species, constituting the viral microecology of the host. The normal state viruses can undergo antigenic mutation to break through immune pressure and become abnormal, then viruses can proliferate again and spread to cause infection in host population, and would returned into normal state after a new immune protection to be established again. The primary infection of the normal state virus and the re-infection of the abnormal state virus can cause disease due to the immune toxicity induced by the immune response.The identification of permanent resident virus in human beings is of significant importance for studying the epidemiology, pathogenesis, clinical manifestations and outcomes of human viral diseases and epidemics, as well as prevention and treatment. Vaccine can successfully prevent the diseases caused by initial infection of normal state viruses. However, for the re-infection of abnormal state viruses, it is difficult to evaluate the preventive effect of vaccines because of the matching problem between previous vaccines and new antigens of abnormal state virus.