Immunoglobulin allotypes in Ecuadorian Cayapa Indians.

Indigenous Indian groups comprise approximately 20% of Ecuador's population, the third largest percentage in all of Central or South America, yet immunogenetic data on these groups are lacking in the literature. In the course of population migration studies, sera collected from 65 Ecuadorians living in the northern province of Esmeraldas were typed for six GM and two KM markers. The study population consisted of 47 Cayapa Indians and 18 blacks of African origin, descendants of slaves imported into the area during the seventeenth century. The Cayapa demonstrated three GM phenotypes, two of which are common to other South American Indian tribes. The frequency of KM1 positive Cayapa Indians (63%) is similar to other South American Indian tribes, but is significantly greater than the Huaorani of eastern Ecuador (2%), the only other Ecuadorian Indian group for whom limited immunoglobulin allotype data are available (chi 2 = 35.8, P < 0.0001).

Antibody responses to Onchocerca volvulus in Ecuadorian Indians and blacks.

In Ecuador, previous epidemiological studies of onchocerciasis affecting a population consisting of Blacks of African origin and Amerindians of the Chachi tribe, have demonstrated different frequencies of clinical disease manifestations in each racial group. To explore the possibility of differential antibody responses to O. volvulus antigens in this population, a subset of sera from these two groups of Ecuadorians with onchocerciasis was analyzed for antibody to O. volvulus antigens using ELISA and Western blot techniques. Significantly higher levels of immunoglobulin against O. volvulus were demonstrated in Chachi Indians compared to native Blacks of African origin: total Ig (p = 0.049), IgG (P = 0.002) IgG4 (p = 0.019) and IgA (p = 0.035). Western blot analysis of sera from 41 persons demonstrated more intense and more frequent recognition of low molecular weight parasite antigens in the Chachi compared to a similar group of male and female Ecuadorian Blacks. These data suggest that the intensity of antibody responses to O. volvulus antigens may reflect the influence of racial factors in the pathogenesis of onchocerciasis in Ecuador.