No correlation between IFN-γ response and malaria exposure was observed. However, IL-4 SFC produced upon peptide pL stimulation correlated positively with time of residence in the endemic area and the number of IL-4 spots generated after stimulation with all overlapping peptides (pH, pK, pL)

were higher in individuals who have lived in malaria endemic areas for more than 20 years when compared with those who have lived in such areas for less than 20 years. It is possible that variations in exposure may also explain variations in the type of naturally induced TH1 and TH2 immune responses to PvMSP9 [14]. Indeed, data reported by Troye-Blomberg et al. [37], showed a strong association between elevated IgG and IgE antibodies to blood-stage antigens with increased numbers of IL-4 secreting learn more cells in individuals less susceptible to malaria infection. Similarly, correlations between the production of IL-4 in response to the P. falciparum malaria antigen Pf155RESA and protection against malaria were also reported [38]. The frequency and

numbers of responders to overlapping peptides shows that the core sequence shared with peptides pH, pK and pL (ASIDSMI) is highly immunogenic. However the presence of 23 individuals who present cellular response only to peptide pL suggest Panobinostat research buy that this peptide may have two immunodominant epitopes, one in the overlapping core region and the second one in the carboxy-terminal region that is not shared with pH or pK (DEIDFYEK). The evaluation of IFN-γ and IL-4 production was used here to measure the recognition and activation of T cells by PvMSP9 putative promiscuous T-cell epitopes. To correlate TCL the cellular response with the prevalence of MHC class II alleles, we determined the HLA antigen distribution among the study population. The observation of 13 allelic groups in the cohort suggests that the study population is heterogeneous, presenting a large variety of allelic groups. It was expected in our study

mainly because Brazilian populations have peculiar features of a tri-hybrid populations formed with contribution of Caucasian, African, and native Amerindian origin, in which the phenotypic characteristics of each original population have been highly mixed. However the observation of high frequency of HLA-DR4 and HLA-DQ3 indicates that in this population the Amerindian HLA genotype is conserved [39]. Therefore, previous works already show the association with IgG responders to Plasmodium antigens and the HLA-DRB04 in this population [40] and [41], indeed studies with HLA polymorphism observed in several populations have been attributed to a pathogen induced selection [42] and [43].