Human cytochrome P450 2B6 genetic variability in Botswana: a case of haplotype diversity and convergent phenotypes.

Identification of inter-individual variability for drug metabolism through cytochrome P450 2B6 (CYP2B6) enzyme is important for understanding the differences in clinical responses to malaria and HIV. This study evaluates the distribution of CYP2B6 alleles, haplotypes and inferred metabolic phenotypes among subjects with different ethnicity in Botswana. A total of 570 subjects were analyzed for CYP2B6 polymorphisms at position 516 G > T (rs3745274), 785 A > G (rs2279343) and 983 T > C (rs28399499). Samples were collected in three districts of Botswana where the population belongs to Bantu (Serowe/Palapye and Chobe) and San-related (Ghanzi) ethnicity. The three districts showed different haplotype composition according to the ethnic background but similar metabolic inferred phenotypes, with 59.12%, 34.56%, 2.10% and 4.21% of the subjects having, respectively, an extensive, intermediate, slow and rapid metabolic profile. The results hint at the possibility of a convergent adaptation of detoxifying metabolic phenotypes despite a different haplotype structure due to the different genetic background. The main implication is that, while there is substantial homogeneity of metabolic inferred phenotypes among the country, the response to drugs metabolized via CYP2B6 could be individually associated to an increased risk of treatment failure and toxicity. These are important facts since Botswana is facing malaria elimination and a very high HIV prevalence.

Molecular Surveillance of Plasmodium falciparum Drug Resistance Markers in Clinical Samples from Botswana.

Drug-resistant Plasmodium falciparum is a major threat to global malaria control and elimination efforts. In Botswana, a southern African country approaching malaria elimination, P. falciparum molecular data are not available. Parasites were assessed through pollymerase chain reaction (PCR) for confirmation of positive rapid diagnostic tests, multiplicity of infection (MOI), and drug resistance markers among isolates from clinical uncomplicated malaria cases collected at health facilities. Of 211 dried blood spot samples selected for the study, 186 (88.2%) were PCR positive for P. falciparum. The mean MOI based on MSP1 genotyping was 2.3 and was not associated with age. A high prevalence of wild-type parasites for pfcrt and pfmdr1 was found, with a haplotype frequency (K76/N86) of 88.8% and 17.7% of the isolates having two copies of the pfmdr1 gene. For pfATPase6, all the parasites carried the wild-type S769 allele. Sequencing showed no evidence of non-synonymous mutations associated with reduced artemisinin derivative sensitivity in the P. falciparum k13 gene. In conclusion, we found that P. falciparum parasites in Botswana were mostly wild type for the drug resistance markers evaluated. Yet, there was a high rate of a molecular marker associated to reduced sensitivity to lumefantrine. Our results indicate the need for systematic drug efficacy surveillance to complement malaria elimination efforts.

Prevalence of G6PD deficiency and associated haematological parameters in children from Botswana.

Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency is commonly seen in malaria endemic areas as it is known to confer a selective advantage against malaria. Recently, we reported a high proportion of asymptomatic reservoir of Plasmodium vivax in Botswana, that calls for intervention with primaquine to achieve radical cure of vivax malaria. Considering that individuals with this enzyme deficiency are at risk of haemolysis following primaquine treatment, assessment of the population for the relative frequency of G6PD deficiency is imperative. Samples from 3019 children from all the districts of Botswana were successfully genotyped for polymorphisms at positions 202 and 376 of the G6PD gene. Haematological parameters were also measured. The overall population allele frequency (based on the hemizygous male frequency) was 2.30% (95% CI, 1.77-2.83), while the overall frequency of G6PD-deficient genotypes A- (hemizygote and homozygote genotypes only) was 1.26% (95% CI, 0.86-1.66). G6PD deficiency is spread in Botswana according to the historical prevalence of malaria with a North-West to South-East decreasing gradient trend. There was no association between G6PD status and P. vivax infection. G6PD A- form was found to be associated with decreased RBC count and haemoglobin levels without a known cause or illness. In conclusion, we report for the first time the prevalence of G6PD deficiency in Botswana which is relevant for strategies in the malaria elimination campaign. Further work to examine the activities of the enzyme in the Botswana population at risk for malaria is warranted.

Detection of mustelid herpesvirus-1 infected European badgers (Meles meles) in the British Isles.

The aim of this study was to assess the frequency of mustelid herpesvirus-1 (MusHV-1) infection in free-ranging badgers (Meles meles) in the British Isles. A polymerase chain reaction assay was developed that detected MusHV-1 DNA in 95% (18/19) and 100% (10/10) of anticoagulant-treated blood samples collected from free-ranging badgers sampled in the southwest of England and the Republic of Ireland, respectively. An indirect immunoassay was also developed to detect MusHV-1-specific immunoglobulin-G in serum samples. Using an arbitrary cutoff of twice the optical density obtained with a virus-negative preparation, 32.7% (36/110) of sera sampled from badgers were positive. The conclusion drawn from these data is that infection with MusHV-1 is common among free-ranging badgers in the British Isles.