Genome-wide association study of leprosy in Malawi and Mali.

Leprosy is a chronic infection of the skin and peripheral nerves caused by Mycobacterium leprae. Despite recent improvements in disease control, leprosy remains an important cause of infectious disability globally. Large-scale genetic association studies in Chinese, Vietnamese and Indian populations have identified over 30 susceptibility loci for leprosy. There is a significant burden of leprosy in Africa, however it is uncertain whether the findings of published genetic association studies are generalizable to African populations. To address this, we conducted a genome-wide association study (GWAS) of leprosy in Malawian (327 cases, 436 controls) and Malian (247 cases, 368 controls) individuals. In that analysis, we replicated four risk loci previously reported in China, Vietnam and India; MHC Class I and II, LACC1 and SLC29A3. We further identified a novel leprosy susceptibility locus at 10q24 (rs2015583; combined p = 8.81 × 10-9; OR = 0.51 [95% CI 0.40 - 0.64]). Using publicly-available data we characterise regulatory activity at this locus, identifying ACTR1A as a candidate mediator of leprosy risk. This locus shows evidence of recent positive selection and demonstrates pleiotropy with established risk loci for inflammatory bowel disease and childhood-onset asthma. A shared genetic architecture for leprosy and inflammatory bowel disease has been previously described. We expand on this, strengthening the hypothesis that selection pressure driven by leprosy has shaped the evolution of autoimmune and atopic disease in modern populations. More broadly, our data highlights the importance of defining the genetic architecture of disease across genetically diverse populations, and that disease insights derived from GWAS in one population may not translate to all affected populations.

Genetic diversity of Plasmodium falciparum in human malaria cases in Mali.

BACKGROUND: In Mali, Plasmodium falciparum malaria is highly endemic and remains stable despite the implementation of various malaria control measures. Understanding P. falciparum population structure variations across the country could provide new insights to guide malaria control programmes. In this study, P. falciparum genetic diversity and population structure in regions of varying patterns of malaria transmission in Mali were analysed. METHODS: A total of 648 blood isolates adsorbed onto filter papers during population surveillance surveys (December 2012-March 2013, October 2013) in four distinct sites of Mali were screened for the presence of P. falciparum via quantitative PCR (qPCR). Multiple loci variable number of tandem repeats analysis (MLVA) using eight microsatellite markers was then performed on positive qPCR samples. Complete genotypes were then analysed for genetic diversity, genetic differentiation and linkage disequilibrium. RESULTS: Of 156 qPCR-positive samples, complete genotyping of 112 samples was achieved. The parasite populations displayed high genetic diversity (mean He = 0.77), which was consistent with a high level of malaria transmission in Mali. Genetic differentiation was low (FST < 0.02), even between sites located approximately 900 km apart, thereby illustrating marked gene flux amongst parasite populations. The lack of linkage disequilibrium further revealed an absence of local clonal expansion, which was corroborated by the genotype relationship results. In contrast to the stable genetic diversity level observed throughout the country, mean multiplicity of infection increased from north to south (from 1.4 to 2.06) and paralleled malaria transmission levels observed locally. CONCLUSIONS: In Mali, the high level of genetic diversity and the pronounced gene flux amongst P. falciparum populations may represent an obstacle to control malaria. Indeed, results suggest that parasite populations are polymorphic enough to adapt to their host and to counteract interventions, such as anti-malarial vaccination. Additionally, the panmictic parasite population structure imply that resistance traits may disseminate freely from one area to another, making control measures performed at a local level ineffective.

Understandings of genomic research in developing countries: a qualitative study of the views of MalariaGEN participants in Mali.

BACKGROUND: Obtaining informed consent for participation in genomic research in low-income settings presents specific ethical issues requiring attention. These include the challenges that arise when providing information about unfamiliar and technical research methods, the implications of complicated infrastructure and data sharing requirements, and the potential consequences of future research with samples and data. This study investigated researchers' and participants' parents' experiences of a consent process and understandings of a genome-wide association study of malaria involving children aged five and under in Mali. It aimed to inform best practices in recruiting participants into genomic research. METHODS: A qualitative rapid ethical assessment was undertaken. Fifty-five semi-structured interviews were conducted with the parents of research participants. An additional nine semi-structured interviews were conducted with senior research scientists, research assistants and with a member of an ethics committee. A focus group with five parents of research participants and direct observations of four consent processes were also conducted. French and translated English transcripts were descriptively and thematically coded using OpenCode software. RESULTS: Participants' parents in the MalariaGEN study had differing understandings of the causes of malaria, the rationale for collecting blood samples, the purposes of the study and the kinds of information the study would generate. Genomic aspects of the research, including the gene/environment interaction underlying susceptibility or resistance to severe malaria, proved particularly challenging to explain and understand. CONCLUSIONS: This study identifies a number of areas to be addressed in the design of consent processes for genomic research, some of which require careful ethical analysis. These include determining how much information should be provided about differing aspects of the research and how best to promote understandings of genomic research. We conclude that it is important to build capacity in the design and conduct of effective and appropriate consent processes for genomic research in low and middle-income settings. Additionally, consideration should be given to the role of review committees and community consultation activities in protecting the interests of participants in genomic research.

Clinical evidence of the role of Methanobrevibacter smithii in severe acute malnutrition.

Gut microbial dysbiosis has been shown to be an instrumental factor in severe acute malnutrition (SAM) and particularly, the absence of Methanobrevibacter smithii, a key player in energy harvest. Nevertheless, it remains unknown whether this absence reflects an immaturity or a loss of the microbiota. In order to assess that, we performed a case-control study in Mali using a propensity score weighting approach. The presence of M. smithii was tested using quantitative PCR on faeces collected from SAM children at inclusion and at discharge when possible or at day 15 for controls. M. smithii was highly significantly associated with the absence of SAM, detected in 40.9% controls but only in 4.2% cases (p < 0.0001). The predictive positive value for detection of M. smithii gradually increased with age in controls while decreasing in cases. Among children providing two samples with a negative first sample, no SAM children became positive, while this proportion was 2/4 in controls (p = 0.0015). This data suggests that gut dysbiosis in SAM is not an immaturity but rather features a loss of M. smithii. The addition of M. smithii as a probiotic may thus represent an important addition to therapeutic approaches to restore gut symbiosis.

A Decline and Age Shift in Malaria Incidence in Rural Mali following Implementation of Seasonal Malaria Chemoprevention and Indoor Residual Spraying.

Many African countries have reported declines in malaria incidence, attributed to the implementation of control strategies. In Mali, artemisinin-based combination therapy (ACT) was introduced in 2004, and long-lasting insecticide-treated nets (LLINs) have been partially distributed free of charge since 2007. In the Malian town of Bandiagara, a study conducted from 2009 to 2013 showed a stable incidence of malaria compared with 1999, despite the implementation of ACTs and LLINs. Since 2016, seasonal malaria chemoprevention has been scaled up across the country. In addition to these strategies, the population of Bandiagara benefited from indoor residual spray implementation in 2017 and 2018 and continued universal bed net coverage. This study aimed to measure the incidence of malaria in Bandiagara, given this recent scaling up of control strategies. A cohort of 300 children aged 6 months to 15 years was followed up from October 2017 to December 2018. We performed monthly cross-sectional surveys to measure anemia and the prevalence of malaria infection by microscopy. The overall incidence of symptomatic malaria was 0.5 episodes/person-year. Malaria incidence in children up to 5 years old significantly declined since 2012 and since 1999 (incidence rate ratio estimates: 6.7 [95% CI: 4.2-11.4] and 13.5 [95% CI: 8.4-22.7]), respectively. The average prevalence of malaria parasitemia was 6.7%. Malaria incidence was higher in children older than 5 years than in those younger than 5 years, highlighting the need to extend malaria control efforts to these older children.

Draft Genome Sequence of Bacillus velezensis Strain Marseille-Q1230, Isolated from a Stool Sample from a Severely Malnourished Child.

Bacillus velezensis, a species first described in 2005, has been mostly associated with plants and the environment. To date, there is no genome available for this species from human samples. In this announcement, we present the genome of Bacillus velezensis strain Marseille-Q1230, which was isolated from a stool sample from a child suffering from severe acute malnutrition. The genome assembled into 15 contigs and had a size of 3,861,152 bp, with a GC content of 46.6%. A total of 3,716 protein-coding genes, including 3 antibiotic resistance genes and 92 RNAs, were predicted.

A functional promoter variant in IL12B predisposes to cerebral malaria.

The role of the Th1 pathway in the pathogenesis of severe malaria is unclear. We recently reported that a polymorphism with increasing IFNG transcription is associated with protection against cerebral malaria (CM). Interleukin-12 is required for Th1 cell differentiation, which is characterized by the production of interferon-gamma. We investigated 21 markers in IL12-related genes, including IL12A and IL12B encoding the two IL-12 (IL12p70) subunits, IL12p35 and IL12p40. We performed a family-based association study using a total sample set of 240 nuclear families. The IL12Bpro polymorphism was associated with susceptibility to CM. The CTCTAA allele and the GC/CTCTAA genotype are over-transmitted to children with CM (P = 0.0002 and 0.00002, respectively). We estimated the odds ratio to be 2.11 for risk of CM in heterozygous children [(95% confidence interval, 1.49-2.99); P < 0.0001]. Although the CTCTAA allele had a dominant effect on CM susceptibility, this effect is much stronger in heterozygous children, consistent with the functional effects of this allele in a heterozygous form. Heterozygosity for this polymorphism has been associated with reduced expression of the gene encoding IL12p40 and a low level of IL12p70 production. These results, together with the findings from immunological studies of low interferon-gamma and IL-12 levels in CM, support a protective role for the Th1 pathway in CM.

Safety of epoietin beta-quinine drug combination in children with cerebral malaria in Mali.

BACKGROUND: Cerebral malaria carries an unacceptable case fatality rate in children despite timely and adequate chemotherapy. To improve the survival rate, adjunctive therapies previously tested mainly focused on the modulation of the inflammatory response, without definitive effect in humans. In this context, a new adjunctive strategy using a neuroprotective drug: erythropoietin (epoietin-beta, Epo) was proposed. METHODS: An open-labelled study including cerebral malaria children (Blantyre coma score below 3) was conducted in Mali. The objective was to assess the short-term safety (seven days) of erythropoietin at high doses (1,500 U/kg/day during three days) combined to quinine. RESULTS: 35 patients with unrousable coma were included in the study. None of expected side effects of erythropoietin were observed during the seven days follow-up. No significant increase in the case fatality rate (7/35 patients) was observed compared to other studies with mortality rates ranging from 16 to 22% in similar endemic areas. CONCLUSION: These data provide the first evidence of the short-term safety of erythropoietin at high doses combined to quinine. A multicentre study is needed to assess the potential of Epo as an adjunctive therapy to increase the survival during cerebral malaria. CLINICAL REGISTRATION NUMBER: ClinicalTrials.gov ID: NCT00697164.

Blastocystis Colonization Is Associated with Increased Diversity and Altered Gut Bacterial Communities in Healthy Malian Children.

Blastocystis is the most common protozoan colonizing the gut of vertebrates. It modulates the human digestive microbiota in the absence of inflammation and gastrointestinal disease. Although it has been associated with human diseases, including inflammatory bowel disease, its pathogenicity remains controversial. This study aimed to assess the influence of Blastocystis on the gut bacterial communities in healthy children. We conducted a cross-sectional study on 147 Blastocystis-colonized and 149 Blastocystis-noncolonized Malian children, with Blastocystis colonization assessed by real-time PCR and gut microbial communities characterized via 16S rRNA gene (Illumina MiSeq) sequencing and bioinformatics analysis. The gut microbiota diversity was higher in Blastocystis-colonized compared to Blastocystis-noncolonized children. The phyla Firmicutes, Elusimicrobia, Lentisphaerae, and Euryarchaeota were higher in Blastocystis-colonized children, whereas Actinobacteria, Proteobacteria, unassigned bacteria, and Deinococcus-Thermus were higher in Blastocystis-noncolonized children. Moreover, Faecalibacterium prausnitzii (family Ruminococcaceae) and Roseburia sp. (family Lachnospiraceae) abundance was higher in Blastocystis-colonized children. We conclude that Blastocystis colonization is significantly associated with a higher diversity of the gut bacterial communities in healthy children, while it is not associated with the presence of potentially pathogenic bacteria in the human gut.

Genetic polymorphisms with erythrocyte traits in malaria endemic areas of Mali.

African populations are characterized by high degree of genetic diversity. This high genetic diversity could result from the natural selection pressure. Several studies have described an association between some genetic diversities and difference of susceptibility to infectious diseases like malaria. It seems therefore important to consider genetic diversity impact when interpreting results of clinical trials in malaria endemic areas. This study aimed to determine the genetic polymorphism with erythrocyte traits in different populations of malaria endemic area in Mali. The cross-sectional surveys were carried out in different ethnic groups living in malaria endemic areas in Mali. Six milliliters of whole blood were collected in EDTA vials from each participant after informed consent has been obtained. The ABO, RH, Kell, MNSs, Kidd and Duffy systems phenotypes were assessed by the technique of gel filtration. A total of 231 subjects were included from six villages. The blood groups phenotypes O (40.7%) and A (31.2%) were more frequent with respective allele frequencies of 0.65 and 0.21. In the RH system the haplotypes R0 (0.55), r (0.20) and R1 (0.13) were the most frequent. Seven percent (7%) of Duffy positive and 4% of Glycophorin B deficiency (S-s-) were observed among participants. All participants were Kell negative. ABO and RH systems were polymorphic in these ethnic groups in Mali. Their implication in susceptibility to malaria should be taken into account in clinical trials interpretation, and for prevention of blood transfusion risks during anemia frequently caused by malaria in children.

Characterisation of the opposing effects of G6PD deficiency on cerebral malaria and severe malarial anaemia.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is believed to confer protection against Plasmodium falciparum malaria, but the precise nature of the protective effecthas proved difficult to define as G6PD deficiency has multiple allelic variants with different effects in males and females, and it has heterogeneous effects on the clinical outcome of P. falciparum infection. Here we report an analysis of multiple allelic forms of G6PD deficiency in a large multi-centre case-control study of severe malaria, using the WHO classification of G6PD mutations to estimate each individual's level of enzyme activity from their genotype. Aggregated across all genotypes, we find that increasing levels of G6PD deficiency are associated with decreasing risk of cerebral malaria, but with increased risk of severe malarial anaemia. Models of balancing selection based on these findings indicate that an evolutionary trade-off between different clinical outcomes of P. falciparum infection could have been a major cause of the high levels of G6PD polymorphism seen in human populations.

Candidate polymorphisms and severe malaria in a Malian population.

Malaria is a major health burden in sub-Saharan African countries, including Mali. The disease is complex, with multiple genetic determinants influencing the observed variation in response to infection, progression, and severity. We assess the influence of sixty-four candidate loci, including the sickle cell polymorphism (HbS), on severe malaria in a case-control study consisting of over 900 individuals from Bamako, Mali. We confirm the known protective effects of the blood group O and the HbS AS genotype on life-threatening malaria. In addition, our analysis revealed a marginal susceptibility effect for the CD40 ligand (CD40L)+220C allele. The lack of statistical evidence for other candidates may demonstrate the need for large-scale genome-wide association studies in malaria to discover new polymorphisms. It also demonstrates the need for establishing the region-specific repertoire of functional variation in important genes, including the glucose-6-phosphatase deficiency gene, before embarking on focused genotyping.