Both snail and parasite genes determine the susceptibility of the snail Biomphalaria glabrata to infection with the trematode Schistosoma mansoni. To identify molecular markers associated with resistance to the parasite in the snail host, we performed genetic crosses between parasite-resistant and -susceptible isogenic snails. Because resistance to infection in adult snails is controlled by a single locus, DNA samples from individual F 2 and F 1 backcross progeny, segregating for either the resistant or susceptible phenotypes, were pooled (bulked segregant). Genotypes for both parents were determined with 205 arbitrary decamer primers by random amplified polymorphic DNA-PCR. Of the 205 primers, 144 were informative, and the relative allele frequencies between the pools for these primers were determined. Two primers, OPM-04 and OPZ-11, produced fragments in the resistant parent of one cross that were inherited in a dominant fashion in the resistant F 2 and backcross-bulked segregant progeny. Subsequent typing of DNA samples of individual progeny snails showed that the 1.2-kb marker amplified by primer OPM-04 and the 1.0-kb marker produced by primer OPZ-11 segregated in the same dominant fashion with the resistant phenotype. Sequence analysis of the 1.2-kb marker showed that it corresponds to a repetitive sequence in the snail genome with no homology to existing DNA sequences in the public databases. Analysis of the 1.0-kb marker showed that it also corresponds to a repetitive sequence in the B. glabrata genome that contains an imperfect ORF, with homology to retrovirus-related group-specific antigens (gag) polyprotein.

IL-1R antagonist (IL-1Ra) is required for adequate host defense in invasive pneumococcal disease (IPD). The minor allele of an IL1RN gene (C/T) promoter polymorphism (rs4251961) has been shown to be associated with decreased IL-1Ra production in healthy adults. We genotyped 299 children with IPD, and examined 19 IL1RN haplotype-tagging single-nucleotide polymorphisms. Human embryonic kidney HEK293(T) cells were transfected with the promoter reporter plasmid pGL3p containing either allelic variant C (pGL3pCC) or T (pGL3pTT) with or without cotransfection with an expression construct overexpressing the globin transcription factor GATA-1. Plasma IL-1Ra concentrations were significantly higher in nonsurvivors compared with survivors (p < 0.0005), and the C allele of rs4251961 was associated with a significant increase in plasma IL-1Ra concentrations (p = 0.01) during the acute illness of IPD. These findings were validated in a cohort of 276 treatment-naive HIV-infected adults, with borderline significance (p = 0.058). Functional analyses demonstrated that the activity of the promoter constructs containing the T allele increased ~6-fold as compared with basal activity, and that containing the C allele by ~9-fold (p < 0.001) in the presence of GATA-1. Our findings suggest that the IL-1Ra single-nucleotide polymorphism rs4251961 plays a key role in the pathophysiology of IPD and in other human infections.

We modeled nevirapine (NVP) pharmacokinetics in HIV-infected Malawian patients to assess the relationship between drug exposure and patient characteristics, genetic polymorphisms, and development of hypersensitivity reaction (HSR). One thousand one hundred seventeen patients were prospectively recruited and followed for 26 weeks with multiple or single serum samples obtained in a subset of patients for NVP quantification. Single nucleotide polymorphisms (SNPs) within CYP2B6 and CYP3A4 genes were typed. Nonlinear mixed effects modeling was utilized to assess the influence of patient characteristics and host genetics on NVP apparent oral clearance (CL/F) and to explore the relationship between NVP CL/F and HSR. Published haplotype distributions were used to simulate NVP concentrations in Caucasians versus Africans. One hundred eighty patients (101 female) were included in the model; 25 experienced HSR. No associations between patient demographics or HSR and NVP CL/F were evident. A significant relationship between CYP2B6 c.983T>C and CYP2B6 c.516G>T and NVP CL/F was observed (P < 0.01). NVP CL/F was reduced by 23% and 36% in patients with CYP2B6 983TT/516TT and 983TC/516GG or GT, respectively, compared to the reference genotype. Simulated exposures suggested similar proportions (13 to 17%) of patients with subtherapeutic NVP among Caucasians and an African population. Influence of CYP2B6 polymorphisms on NVP CL/F in this population is in agreement with other reports. Our data indicate a lack of association between NVP exposure and HSR. Based on these data, dose optimization based solely on ethnicity (without individual gene testing) is unlikely to impact on risk of treatment failure or toxicity even in an African population with high carriage of poor metabolizer mutations.