HUMAN GENETIC SUSCEPTIBILITY AND INFECTION WITH LEISHMANIA-PERUVIANA

Racial differences, familial clustering, and murine studies are sugges tive of host genetic control of Leishmania infections. Complex segrega tion analysis has been carried out by use of the programs POINTER and COMDS and data from a total population survey, comprising 636 nuclear families, from an L. peruviana endemic area. The data support genetic components controlling susceptibility to clinical leishmaniasis, influ encing severity of disease and resistance to disease among healthy ind ividuals. A multifactorial model is favored over a sporadic model. Two -locus models provided the best fit to the data, the optimal model bei ng a recessive gene (frequency .57) plus a modifier locus. Individuals infected at an early age and with recurrent lesions are genetically m ore susceptible than those infected with a single episode of disease a t a later age. Among people with no lesions, those with a positive ski n-test response are genetically less susceptible than those with a neg ative response. The possibility of the involvement of more than one ge ne together with environmental effects has implications for the design of future linkage studies.