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Ethnic Differences in the Distribution of
Interleukin-6 and Interleukin-10 Polymorphisms among Three Brazilian Ethnic
Groups and Investigation if these polymorphisms Could Be Involved with Disease
in HTLV-1 Infected Individuals from Salvador, Bahia, Brazil
Gadelha, S.R.1, Alcantara, L.C..1,2, Costa, G.C.S.1, Rios,
D.L.1, Galvão-Castro, B.1,2.
Laboratório Avançado de Saúde Pública/Centro de Pesquisas
Gonçalo Moniz/ Fundação Oswaldo Cruz, Salvador, Ba; 2 Centro de HTLV/Escola
Baiana de Medicina e Saúde Pública/ Fundação para o Desenvolvimento das
Ciências, Salvador, Bahia.
sandragadelha@hotmail.com
Cytokine gene polymorphisms have been
associated with disease prevalence and severity. Besides, it has been shown
that polymorphisms can affect cytokine production and in some disorders, as in
HTLV-1 infected individuals, this effect might help to keep the status
asymptomatic or disease development. In addition, differences in the allele
distribution of cytokines gene variants have been found in diverse ethnic groups.
This fact could explain why some populations are more susceptible to some
disorders. We investigated IL-6 and IL-10 promoter polymorphisms, at -634 and
-174 positions in IL-6 and -592 in IL-10, in healthy individuals from 3 Brazilian ethnic groups: 99 Amerindians inhabiting an isolated region of Northern
Brazil; 94 German descendents from Joinville; and 100 individuals from
Salvador/Bahia. Besides, we investigated these polymorphisms in 133 HTLV-1
infected individuals from Salvador (84 asymptomatic, 26 with HAM/TSP and 23
oligosymptomatic). The polymorphisms were investigated by RFLP (-634G/C and
-592C/A) and Real Time PCR (–174G/C). Genotype frequencies had no significantly
difference of those expected under the Hardy-Weinberg. The allele frequencies of
the IL-6 polymorphisms were heterogeneous in the all studied populations. The
estimated two-site IL-6 promoter haplotype frequencies in these three
populations showed that the wild haplotype (-634G/-174G) was the most common
haplotype in the Joinville (59%) and Salvador (66.5%) populations. However, the
634C/-174G polymosphism was most common among the Amerindians, (54.8%). It has
been shown that –174 C IL-6 allele frequency is highly heterogeneous among
different populations, and the results were consistent with the populations
that had the same ethnic background. Few studies have investigated the –634 C/G
IL-6 gene polymorphism, and all were carried out in Asian populations. This was
the first report of this variant in these ethnic groups. In relation to IL-10,
we observed a significant difference in the allele frequency among individuals
from Tiriyó and the other populations, but it was absent among individuals from
Salvador and Joinville. The –592 A IL-10 allele were significantly more
prevalent in Tiryio and its frequencies was similar to Asian and Indian
populations. In the infected individuals, –634 C allele and -174 G
allele were more prevalent in HAM/TSP patients. In these patients,
we not found differences at IL-10 polymorphism. These data suggest
that IL-6 polymorphisms can be important in the development of
symptoms in HTLV-1 infected individuals and can contribute to better
understanding of the complex association between IL-6 promoter
variability and disease susceptibility.
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