Lilian Castilho

Duffy blood group gene polymorphisms among malaria vivax patients in four areas of the Brazilian Amazon region

BackgroundDuffy blood group polymorphisms are important in areas where Plasmodium vivax predominates, because this molecule acts as a receptor for this protozoan. In the present study, Duffy blood group genotyping in P. vivax malaria patients from four different Brazilian endemic areas is reported, exploring significant associations between blood group variants and susceptibility or resistance to malaria.MethodsThe P. vivax identification was determined by non-genotypic and genotypic screening tests. The Duffy blood group was genotyped by PCR/RFLP in 330 blood donors and 312 malaria patients from four Brazilian Amazon areas. In order to assess the variables significance and to obtain independence among the proportions, the Fishers exact test was used.ResultsThe data show a high frequency of the FYA/FYB genotype, followed by FYB/FYB, FYA/FYA, FYA/FYB-33 and FYB/FYB-33. Low frequencies were detected for the FYA/FYX, FYB/FYX, FYX/FYXand FYB-33/FYB-33 genotypes. Negative Duffy genotype (FYB-33/FYB-33) was found in both groups: individuals infected and non-infected (blood donors). No individual carried the FYX/FYB-33 genotype. Some of the Duffy genotypes frequencies showed significant differences between donors and malaria patients.ConclusionThe obtained data suggest that individuals with the FYA/FYB genotype have higher susceptibility to malaria. The presence of the FYB-33 allele may be a selective advantage in the population, reducing the rate of infection by P. vivax in this region. Additional efforts may contribute to better elucidate the physiopathologic differences in this parasite/host relationship in regions endemic for P. vivax malaria, in particular the Brazilian Amazon region.

Population Genetics of GYPB and Association Study between GYPB*S/s Polymorphism and Susceptibility to P. falciparum Infection in the Brazilian Amazon

Background Merozoites of Plasmodium falciparum invade through several pathways using different RBC receptors. Field isolates appear to use a greater variability of these receptors than laboratory isolates. Brazilian field isolates were shown to mostly utilize glycophorin A-independent invasion pathways via glycophorin B (GPB) and/or other receptors. The Brazilian population exhibits extensive polymorphism in blood group antigens, however, no studies have been done to relate the prevalence of the antigens that function as receptors for P. falciparum and the ability of the parasite to invade. Our study aimed to establish whether variation in the GYPB*S/s alleles influences susceptibility to infection with P. falciparum in the admixed population of Brazil. Methods Two groups of Brazilian Amazonians from Porto Velho were studied: P. falciparum infected individuals (cases); and uninfected individuals who were born and/or have lived in the same endemic region for over ten years, were exposed to infection but have not had malaria over the study period (controls). The GPB Ss phenotype and GYPB*S/s alleles were determined by standard methods. Sixty two Ancestry Informative Markers were genotyped on each individual to estimate admixture and control its potential effect on the association between frequency of GYPB*S and malaria infection. Results GYPB*S is associated with host susceptibility to infection with P. falciparum; GYPB*S/GYPB*S and GYPB*S/GYPB*s were significantly more prevalent in the in the P. falciparum infected individuals than in the controls (69.87% vs. 49.75%; P<0.02). Moreover, population genetics tests applied on the GYPB exon sequencing data suggest that natural selection shaped the observed pattern of nucleotide diversity. Conclusion Epidemiological and evolutionary approaches suggest an important role for the GPB receptor in RBC invasion by P. falciparum in Brazilian Amazons. Moreover, an increased susceptibility to infection by this parasite is associated with the GPB S+ variant in this population.

Frequencies of ABO, MNSs, and Duffy Phenotypes Among Blood Donors and Malaria Patients from Four Brazilian Amazon Areas

ABSTRACT We compared the serological phenotypic frequencies of ABO, MNSs, and Duffy in 417 blood donors and 309 malaria patients from four Brazilian Amazon areas. Our results suggest no correlation between ABO phenotype and malaria infection in all areas studied. We observed significant correlation between the S+s+, S+s−, and S−s+ phenotypes and malaria infection in three areas. Some of the Duffy phenotypes showed significant correlation between donors and malaria patients in different areas. These data are an additional contribution to the establishment of differential host susceptibility to malaria.

Clinically relevant RHD-CE genotypes in patients with sickle cell disease and in African Brazilian donors.

BACKGROUND As a consequence of the homology and opposite orientation of RHD and RHCE, numerous gene rearrangements have occurred in Africans and resulted in altered RH alleles that predict partial antigens, contributing to the high rate of Rh alloimmunisation among patients with sickle cell disease (SCD). In this study, we characterised variant RH alleles encoding partial antigens and/or lacking high prevalence antigens in patients with SCD and in African Brazilian donors, in order to support antigen-matched blood for transfusion. MATERIAL AND METHODS RH genotypes were determined in 168 DNA samples from SCD patients and 280 DNA samples from African Brazilian donors. Laboratory developed tests, RHD BeadChip(TM), RHCE BeadChip(TM), cloning and sequencing were used to determine RHD-CE genotypes among patients and African Brazilian blood donors. RESULTS The distributions of RHD and RHCE alleles in donors and patients were similar. We found RHCE variant alleles inherited with altered RHD alleles in 25 out of 168 patients (15%) and in 22 out of 280 (7.8%) African Brazilian donors. The RHD and RHCE allele combinations found in the population studied were: RHD*DAR with RHCE*ceAR; RHD*weak D type 4.2.2 with RHCE*ceAR, RHD*weak D type 4.0 with RHCE*ceVS.01 and RHCE*ceVS.02; RHD*DIIIa with RHCE*ceVS.02. Thirteen patients and six donors had RHD-CE genotypes with homozygous or compound heterozygous alleles predicting partial antigens and/or lacking high prevalence antigens. Eleven patients were alloimmunised to Rh antigens. For six patients with RHD-CE genotypes predicting partial antigens, no donors with similar genotypes were found. DISCUSSION Knowledge of the distribution and prevalence of RH alleles in patients with SCD and donors of African origin may be important for implementing a programme for RH genotype matching in SCD patients with RH variant alleles and clinically significant Rh antibodies.