RESUMO
The pathologic manifestations of Onchocerca volvulus infection depend on the interplay between the host and the parasite. A genetic single nucleotide polymorphism in the Fc gamma RIIa gene, resulting in arginine (R) or histidine (H) at position 131, affects the binding to the different IgG subclasses and may influence the clinical variations seen in onchocerciasis. This study investigated the relationship between this polymorphism and disease outcome. Fc gamma RIIa genotyping was performed on clinically characterized onchocerciasis patients (N = 100) and healthy controls (N = 74). Fc gamma RIIa genotype R/R131 frequencies were significantly higher among patients with severe dermatopathology (P < 0.001). Increased risk of developing this form was mostly associated with one tribe (Masalit) (OR = 3.2, 95% CI 1-9.9, P = 0.042). The H131 allele was found to be significantly associated with a reduced risk of having the severe form of the disease (adjusted OR = 0.26, 95% CI = 0.13-0.46, P < 0.001). Our findings suggest that the polymorphism influences the clinical outcome of onchocerciasis.
Assuntos
Antígenos CD/genética , Predisposição Genética para Doença/genética , Onchocerca volvulus/patogenicidade , Oncocercose/genética , Polimorfismo Genético , Receptores de IgG/genética , Adolescente , Adulto , Animais , Estudos de Casos e Controles , Criança , Pré-Escolar , Primers do DNA/química , Feminino , Frequência do Gene , Humanos , Lactente , Masculino , Oncocercose/patologia , Reação em Cadeia da Polimerase , Fatores de Risco , Índice de Gravidade de Doença , Sudão/epidemiologiaRESUMO
BACKGROUND: There are few published studies on Plasmodium falciparum genotypes in peripheral, placental and umbilical cord blood in areas characterised by unstable malaria transmission. METHOD: A cross-sectional study was conducted to investigate P. falciparum genotypes in matched peripheral, placental and umbilical cord blood in eastern Sudan. Thick blood smears and P. falciparum merozoite surface protein 1 (MSP1) and 2 (MSP2) genes as polymorphic markers in polymerase chain reactions were investigated in 3 kinds of samples of 153 pregnant women at delivery. RESULTS: There was no significant difference in the prevalence of blood film-detected P. falciparum in which 5 (3.3%), 7 (4.6%) and 3 (2.0%) (P = 0.437) of the 153 samples were determined to be P. falciparum-positive by microscopy for maternal peripheral, placental and cord blood samples, respectively. Out of these 145 samples, 24 (16.6%), 39 (26.9%) and 24 (16.6%) (P = 0.039) of the peripheral, placental and cord samples, respectively, had submicroscopic parasitaemia (blood films were negative). There was no association between submicroscopic parasitaemia and age or parity. RO33 and K1 (MSP1 alleles) were detected in 21/29 (72.4%), 42/46 (85.7%), 26/27 (92.2%) and 6/29 (20.6), 16/46 (32.6) and 0(0) (P < 0.001) of the maternal, placental and cord samples, respectively. MAD20 was not detected in any of the samples. While the 3D7/IC1 allele was detected in 12 (41.3%), 30 (65.2%) and 4 (14.8%) (P < 0.001) of the peripheral, placental and cord samples, respectively, the FC (MSP2) allele was detected in only the 6 (20.6) placental samples. Multi-clonal infection was detected in 10 (34.4), 27 (58.6) and 3 (11.1) (P < 0.001) of the maternal placental and cord samples, respectively. CONCLUSION: Compared with the peripheral and cord samples, placental samples had a higher prevalence of submicroscopic parasitaemia. MSP1 alleles were predominant in the cord, while MSP2 alleles were predominant in the placental samples, which had a significant higher multiplicity of the infection.