The Genetic Predisposition of Human and Laboratory Animals to Different Infections Transmitted by Ixodid Ticks

Ixodid ticks are carriers of causative agents of infectious diseases dangerous to humans, including tick-borne encephalitis, ixodid tick-borne borrelioses, rickettsioses, human monocytic ehrlichiosis, human granulocytic anaplasmosis, Congo–Crimean hemorrhagic fever, Omsk hemorrhagic fever, Q fever, and tularemia. These natural focal diseases represent a significant medical problem. It is known that an organism’s response to the effect of an infectious agent (and, as a consequence, peculiarities of the course and outcome of the disease) depends not only on the characteristics of the causative agent and external factors, but also significantly on the individual characteristics of the host (particularly, human) genome that predetermine the ability of its immune system to suppress the development of infection. There are two main approaches to the search for human genes predetermining the degree of his susceptibility/resistance to infectious agents. First, the analysis of candidate genes that are presumably relevant to the development of this disease based on known or putative functions of their protein products or on previous data on the orthologous genes in model organisms. Second, genome-wide association analysis, in which a large number of genetic markers evenly distributed across the human genome are simultaneously analyzed. The human genetic predisposition to such infectious diseases as AIDS, tuberculosis, malaria, hepatitis C and B, etc., has been intensively studied, and human genetic factors that specifically predetermine the efficiency of protective reactions against these infections have been already identified. As for infections transmitted by ixodid ticks, the genes of human predisposition to them are those far less studied, and the existing data are rather scattered. This review summarizes already-known genetic factors associated with predisposition to different infections transmitted by ixodid ticks in beings human and laboratory animals, as well as approaches to identification of these factors.