Genetics of susceptibility to infectious diseases: tuberculosis and leprosy as examples.

In the majority of infectious diseases only a proportion of individuals exposed to a pathogen become infected and develop clinically evident disease. At least in part, this interindividual variability is determined by the combined effect of host proteins encoded by a series of genes that control the quantity and quality of host-parasite interaction and host immune responses. Identification of the most important host susceptibility/resistance genes will allow a better understanding of infectious disease pathogenesis and likely facilitate the development of new therapeutic strategies. Several approaches can be used to map and identify a host infectious disease susceptibility gene. Three of the most widely used strategies, i.e., mouse models, candidate gene approach, and genome scanning, are briefly presented. To date, at least 11 genes have been implicated in susceptibility/resistance to mycobacterial infection and a short discussion of the experiments implicating individual genes in infectious disease susceptibility is given.