Genetic epidemiology of infectious disease

The genetic mechanisms involved in the variability of the human response to the infection of some organisms are critically reviewed. For leprosy and leishmaniasis there seems to exist no simple and general mechanism. The Mitsuda reaction, however, seems to be the most important phenotype measuring the human response to M. leprae. Several genes are known to affect the resistance/susceptibility to malaria. Studies on this disease should take into account all of this variability and be particularly cautious regarding the natural history of the population under study in order to establish the relative importance of given genes on a given population subject to a give epidemic. The sole parasitic disease that did not show discrepancies among studies is schistosomiasis, indicating the importance of a single additive gene that, ultimately, acts on the individualïs capacity to build and efficient eosinophilia. Future studies should focus on general mechanisms as well as on explanations of the existent disparities between studies.

Epidemiologia genética da hanseníase e da reaçäo de Mitsuda / Genetic epidemiology of leprosy and Mitsuda reaction

Os mecanismos genéticos que podem atuar sobre a susceptibilidade ou resistência a hanseníase sao revistos, enfatizando-se que, apesar de o modelo do camundongo ser muito atraente para ser estendido ao ser humano, as particularidades dessa doença tornam difícil qualquer extrapolaçao. Vários estudos recentes baseados na distribuiçao familiar da hanseníase nao encontraram um mecanismo genético claro responsável pela hanseníase "per se", nem para os tipos polares da doença. Contudo, foi demonstrado ser a reaçao de Mitsuda um fenótipo determinado por um gene principal com um alto grau de dominância. É enfatizado que a pesquisa deveria, agora, ser dirigida para mapear o gene responsável pela variabilidade exibida pela reaçao tardia à mitsudina injetada intradermicamente.