RESUMO
It has been previously shown that there are some interethnic differences in susceptibility to malaria between two sympatric ethnic groups of Mali, the Fulani and the Dogon. The lower susceptibility to Plasmodium falciparum malaria seen in the Fulani has not been fully explained by genetic polymorphisms previously known to be associated with malaria resistance, including haemoglobin S (HbS), haemoglobin C (HbC), alpha-thalassaemia and glucose-6-phosphate dehydrogenase (G6PD) deficiency. Given the observed differences in the distribution of FcγRIIa allotypes among different ethnic groups and with malaria susceptibility that have been reported, we analysed the rs1801274-R131H polymorphism in the FcγRIIa gene in a study of Dogon and Fulani in Mali (n = 939). We confirm that the Fulani have less parasite densities, less parasite prevalence, more spleen enlargement and higher levels of total IgG antibodies (anti-CSP, anti-AMA1, anti-MSP1 and anti-MSP2) and more total IgE (P < 0.05) compared with the Dogon ethnic group. Furthermore, the Fulani exhibit higher frequencies of the blood group O (56.5%) compared with the Dogon (43.5%) (P < 0.001). With regard to the FcγRIIa polymorphism and allele frequency, the Fulani group have a higher frequency of the H allele (Fulani 0.474, Dogon 0.341, P < 0.0001), which was associated with greater total IgE production (P = 0.004). Our findings show that the FcγRIIa polymorphism might have an implication in the relative protection seen in the Fulani tribe, with confirmatory studies required in other malaria endemic settings.
Assuntos
Predisposição Genética para Doença/genética , Malária Falciparum/genética , Polimorfismo de Nucleotídeo Único , Receptores de IgG/genética , Adolescente , Anticorpos Antiprotozoários/imunologia , Criança , Pré-Escolar , Etnicidade/genética , Feminino , Frequência do Gene , Predisposição Genética para Doença/etnologia , Genótipo , Interações Hospedeiro-Parasita , Humanos , Imunoglobulina E/imunologia , Imunoglobulina G/imunologia , Lactente , Recém-Nascido , Malária Falciparum/etnologia , Malária Falciparum/imunologia , Masculino , Mali/epidemiologia , Plasmodium falciparum/imunologia , Plasmodium falciparum/fisiologia , Prevalência , Esplenomegalia/genética , Esplenomegalia/imunologia , Esplenomegalia/parasitologiaRESUMO
Unprecedented cure after infection with the lethal Plasmodium berghei ANKA was observed in an F2 progeny generated by intercrossing the wild-derived WLA and the laboratory C57BL/6 mouse strains. Resistant mice were able to clear parasitaemia and establish immunity. The observed resistance was disclosed as a combinatorial effect of genetic factors derived from the two parental strains. Genetic mapping of survival time showed that the WLA allele at a locus on chromosome 1 (colocalizing with Berghei resistance 1 (Berr1), a locus associated with resistance to experimental cerebral malaria) increases the probability to resist early death. Also, the C57Bl/6 allele at a novel locus on chromosome 9 (Berr3) confers overall resistance to this lethal Plasmodium infection. This report underlines the value of using wild-derived mouse strains to identify novel genetic factors in the aetiology of disease phenotypes, and provides a unique model for studying parasite clearance and immunity associated with malaria.
Assuntos
Cromossomos/genética , Imunidade Inata/genética , Malária/genética , Plasmodium berghei , Locos de Características Quantitativas/genética , Animais , Mapeamento Cromossômico , Predisposição Genética para Doença/genética , Malária/imunologia , Malária/parasitologia , Camundongos , Plasmodium berghei/imunologia , Locos de Características Quantitativas/imunologiaRESUMO
The neurological syndrome caused by Plasmodium berghei ANKA in rodents partially mimics the human disease. Several rodent models of cerebral malaria (CM) exist for the study of the mechanisms that cause the disease. However, since common laboratory mouse strains have limited gene pools, the role of their phenotypic variations causing CM is restricted. This constitutes an obstacle for efficient genetic analysis relating to the pathogenesis of malaria. Most common laboratory mouse strains are susceptible to CM, and the same major histocompatibility complex (MHC) haplotype may exhibit different levels of susceptibility. We analyzed the influence of the MHC haplotype on overcoming CM by using MHC congenic mice with C57BL/10 and C3H backgrounds. No correlation was found between MHC molecules and the development of CM. New wild-derived mouse strains with wide genetic polymorphisms were then used to find new models of resistance to CM. Six of the twelve strains tested were resistant to CM. For two of them, F(1) progeny and backcrosses performed with the reference strain C57BL/6 showed a high level of heterogeneity in the number and characteristics of the genetic factors associated with resistance to CM.
