High heritability but uncertain mode of inheritance for total serum IgE level and Schistosoma mansoni infection intensity in a schistosomiasis-endemic Brazilian population.
BACKGROUND
Evidence of genetic control for total serum IgE (tIgE) level has been reported in multiple populations, although populations with substantial exposure to helminths have yielded lower estimates of heritability, despite evidence suggesting that genes also control a significant portion of the variation in the number of Schistosoma mansoni eggs per gram of fecal matter.


METHODS
By use of a whole-population ascertainment scheme, 822 individuals were enrolled from a schistosomiasis-endemic area in Conde, Bahia, in Brazil. Heritability was estimated by using an additive polygenic model, and segregation analysis was performed for 2 quantitative traits, tIgE level and egg count.


RESULTS
After adjusting for nongenetic covariates, the heritability of log-transformed tIgE level and log-transformed egg count was estimated at 60% and 31%, respectively. No evidence for a single major gene controlling tIgE level or egg count was observed in segregation analysis for 781 individuals and 403 individuals, respectively, in 318 families, however, which suggests complex biological control.


CONCLUSIONS
The high heritability of tIgE level indicates that genetic factors are likely to control tIgE level even in the presence of helminthic infection. Substantial heritability for the burden of S. mansoni infection was confirmed in these Brazilian families. Further genetic studies will be needed to dissect the specific genetic factors that underlie these traits.
Grant
Audrey V
AV
Department of Epidemiology, Johns Hopkins University, Baltimore, Maryland, USA. audrey.grant@inserm.fr
Araujo
Maria Ilma
MI
Ponte
Eduardo Vieira
EV
Oliveira
Ricardo Riccio
RR
Cruz
Alvaro A
AA
Barnes
Kathleen C
KC
Beaty
Terri H
TH
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood; D001938:Brazil / Q000453:epidemiology; D002648:Child; D019353:Endemic Diseases; D005243:Feces / Q000469:parasitology; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010270:Parasite Egg Count; D012550:Schistosoma mansoni / Q000254:growth & development / Q000276:immunology* / Q000302:isolation & purification / Q000472:pathogenicity*; D012555:Schistosomiasis mansoni / Q000453:epidemiology* / Q000235:genetics* / Q000276:immunology / Q000469:parasitology
D000909:Antibodies, Helminth; D007073:Immunoglobulin E