Amagana Dolo

The interpretation of a laboratory test result requires an appropriate reference range established in healthy subjects, and normal ranges may vary by factors such as geographic region, sex, and age. We examined hematological and clinical chemistry parameters in healthy residents at two rural vaccine trial sites: Bancoumana and Doneguebougou in Mali, West Africa. During screening of clinical studies in 2018 and 2019, peripheral blood samples from 1,192 apparently healthy individuals age 6 months to 82 years were analyzed at a laboratory accredited by the College of American Pathologists for a complete blood count, and creatinine and/or alanine aminotransferase levels. Based on manufacturers’ reference range values, which are currently used in Malian clinical laboratories, abnormal values were common in this healthy population. In fact, 30.4% of adult participants had abnormal neutrophil levels and 19.8% had abnormal hemoglobin levels. Differences by sex were observed in those who were older, but not in those younger than 10 years, for several parameters, including hemoglobin, platelet, and absolute neutrophil counts in hematology, and creatinine in biochemistry. The site-specific reference intervals we report can be used in malaria vaccine clinical trials and other interventional studies, as well as in routine clinical care, to identify abnormalities in hematological and biochemical parameters among healthy Malian trial participants.

Malaria transmission largely depends on environmental, climatic, and hydrological conditions. In Mali, malaria epidemiological patterns are nested within three ecological zones. This study aimed at assessing the relationship between those conditions and the incidence of malaria in Dangassa and Koila, Mali. Malaria data was collected through passive case detection at community health facilities of each study site from June 2015 to January 2017. Climate and environmental data were obtained over the same time period from the Goddard Earth Sciences (Giovanni) platform and hydrological data from Mali hydraulic services. A generalized additive model was used to determine the lagged time between each principal component analysis derived component and the incidence of malaria cases, and also used to analyze the relationship between malaria and the lagged components in a multivariate approach. Malaria transmission patterns were bimodal at both sites, but peak and lull periods were longer lasting for Koila study site. Temperatures were associated with malaria incidence in both sites. In Dangassa, the wind speed (p = 0.005) and river heights (p = 0.010) contributed to increasing malaria incidence, in contrast to Koila, where it was humidity (p < 0.001) and vegetation (p = 0.004). The relationships between environmental factors and malaria incidence differed between the two settings, implying different malaria dynamics and adjustments in the conception and plan of interventions.

The safety and immunogenicity of PfAMA1, adjuvanted with Alhydrogel® was assessed in malaria–experienced Malian adults. The malaria vaccine, PfAMA1-FVO [25-545] is a recombinant protein Pichia pastoris-expressed AMA-1 from Plasmodium falciparum FVO clone adsorbed to Alhydrogel®, the control vaccine was tetanus toxoid produced from formaldehyde detoxified and purified tetanus toxin. A double blind randomized controlled phase 1 study enrolled and followed 40 healthy adults aged 18–55 years in Bandiagara, Mali, West Africa, a rural setting with intense seasonal transmission of P. falciparum malaria. Volunteers were randomized to receive either 50 µg of malaria vaccine or the control vaccine. Three doses of vaccine were given on Days 0, 28 and 56, and participants were followed for 1 year. Solicited symptoms were assessed for seven days and unsolicited symptoms for 28 days after each vaccination. Serious adverse events were assessed throughout the study. The titres of anti-AMA-1 antibodies were measured by ELISA and P. falciparum growth inhibition assays were performed. Commonest local solicited adverse events were the injection site pain and swelling more frequent in the PfAMA1 group. No vaccine related serious adverse events were reported. A significant 3.5-fold increase of anti-AMA-1 IgG antibodies was observed in malaria vaccine recipients four weeks after the third immunization compared to the control group. The PfAMA1 showed a good safety profile. Most adverse events reported were of mild to moderate intensity. In addition, the vaccine induced a significant though short-lived increase in the anti-AMA1 IgG titres. Registered on www.clinicaltrials.gov with the number NCT00431808

Genetic polymorphisms in the complex gene cluster encoding human Fc-gamma receptors (FcγRs) may influence malaria susceptibility and pathogenesis. Studying genetic susceptibility to malaria is ideal among sympatric populations because the distribution of polymorphic genes among such populations can help in the identification malaria candidate genes. This study determined the distribution of three FcyRs single nucleotide polymorphisms (SNPs) (FcγRIIB-rs1050519, FcγRIIC-rs3933769 and FcγRIIIA-rs396991) among sympatric Fulani and Dogon children with uncomplicated malaria. The association of these SNPs with clinical, malariometric and immunological indices was also tested. This study involved 242 Fulani and Dogon volunteers from Mali age under 15 years. All SNPs were genotyped with predesigned TaqMan® SNP Genotyping Assays. Genotypic and allelic distribution of SNPs was compared across ethnic groups using the Fisher exact test. Variations in clinical, malariometric and immunologic indices between groups were tested with Kruskal–Wallis H, Mann–Whitney U test and Fisher exact test where appropriate. The study confirmed known malariometric and immunologic differences between sympatric Fulani and non-Fulani tribes. Parasite density was lower in the Fulani than the Dogon (p < 0.0001). The mutant allele of FcγRIIC (rs3933769) was found more frequently in the Fulani than the Dogon (p < 0.0001) while that of FcγRIIIA (rs396991) occurred less frequently in the Fulani than Dogon (p = 0.0043). The difference in the mutant allele frequency of FcγRIIB (rs1050519) between the two ethnic groups was however not statistically significant (p = 0.064). The mutant allele of rs396991 was associated with high malaria-specific IgG1 and IgG3 in the entire study population and Dogon tribe, p = 0.023 and 0.015, respectively. Parasite burden was lower in carriers of the FcγRIIC (rs3933769) mutant allele than non-carriers in the entire study population (p < 0.0001). Carriers of this allele harboured less than half the parasites found in non-carriers. Differences in the allelic frequencies of rs3933769 and rs396991 among Fulani and Dogon indirectly suggest that these SNPs may influence malaria susceptibility and pathogenesis in the study population. The high frequency of the FcγRIIC (rs3933769) mutant allele in the Fulani and its subsequent association with low parasite burden in the entire study population is noteworthy.

Many studies report associations between human genetic factors and immunity to malaria but few have been reliably replicated. These studies are usually country-specific, use small sample sizes and are not directly comparable due to differences in methodologies. This study brings together samples and data collected from multiple sites across Africa and Asia to use standardized methods to look for consistent genetic effects on anti-malarial antibody levels. Sera, DNA samples and clinical data were collected from 13,299 individuals from ten sites in Senegal, Mali, Burkina Faso, Sudan, Kenya, Tanzania, and Sri Lanka using standardized methods. DNA was extracted and typed for 202 Single Nucleotide Polymorphisms with known associations to malaria or antibody production, and antibody levels to four clinical grade malarial antigens [AMA1, MSP1, MSP2, and (NANP)4] plus total IgE were measured by ELISA techniques. Regression models were used to investigate the associations of clinical and genetic factors with antibody levels. Malaria infection increased levels of antibodies to malaria antigens and, as expected, stable predictors of anti-malarial antibody levels included age, seasonality, location, and ethnicity. Correlations between antibodies to blood-stage antigens AMA1, MSP1 and MSP2 were higher between themselves than with antibodies to the (NANP)4 epitope of the pre-erythrocytic circumsporozoite protein, while there was little or no correlation with total IgE levels. Individuals with sickle cell trait had significantly lower antibody levels to all blood-stage antigens, and recessive homozygotes for CD36 (rs321198) had significantly lower anti-malarial antibody levels to MSP2. Although the most significant finding with a consistent effect across sites was for sickle cell trait, its effect is likely to be via reducing a microscopically positive parasitaemia rather than directly on antibody levels. However, this study does demonstrate a framework for the feasibility of combining data from sites with heterogeneous malaria transmission levels across Africa and Asia with which to explore genetic effects on anti-malarial immunity.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is associated with protection from severe malaria, and potentially uncomplicated malaria phenotypes. It has been documented that G6PD deficiency in sub-Saharan Africa is due to the 202A/376G G6PD A-allele, and association studies have used genotyping as a convenient technique for epidemiological studies. However, recent studies have shown discrepancies in G6PD202/376 associations with severe malaria. There is evidence to suggest that other G6PD deficiency alleles may be common in some regions of West Africa, and that allelic heterogeneity could explain these discrepancies.

Cette étude avait pour objectif de déterminer la fréquence du déficit en G6PD érythrocytaire (A-^376/202)dans trois groupes ethniques au Mali et de vérifier si cette fréquence observée chez les Peulh expliquerait leur protection particulière précédemment décrite contre le paludisme. Les études ont été menées au Mali, en zone sahélienne où les Dogon et les Peulh vivent en sympatrie, puis en zone de savane soudanienne dans une population de Malinké. L’échantillon d’étude était constitué de 90 Dogon, de 42 Peulh et de 80 Malinké chez lesquels nous avons procédé à la détermination de la charge parasitaire à P. falciparum et au dépistage du déficit en G6PD érythrocytaire par la PCR par la mise en exergue des mutations 376 et 202. Les résultats de l’étude ont montré que le variant (A) caractérisé par une mutation au niveau du nucléotide 376 et une activité normale était retrouvé à une fréquence de 88,9 % chez les Dogon, 97,6 % chez les Peulh et 86,7 % chez les Malinké. La fréquence du variant déficitaire (A-^376/202) chez les femmes (hétérozygotie) était de 7,8 % (7/88) chez les Dogon et de 2,4 % (1/42) chez les Peulh et de 9,3 % (7/75) chez les Malinké. Par contre, le variant (A-^376/202) était retrouvé a une fréquence de 2,2 % (2/90) chez les hommes dans la population dogon, 0 % chez les Peulh et de 4 % (3/75) chez les Malinké. Nous n’avons pas trouvé d’homozygote dans notre population d’étude. Cette étude montre que le déficit en G6PD érythrocytaire (A-^376/202) ne diffère pas significativement entre les trois groupes ethniques, Malinké, Dogon et Peulh. Erythrocyte G6PD deficiency is the most common worldwide enzymopathy. The aim of this study was to determine erythrocyte G6PD deficiency in 3 ethnic groups of Mali and to investigate whether erythrocyte G6PD deficiency was associated to the observed protection against malaria seen in Fulani ethnic group. The study was conducted in two different areas of Mali: in the Sahel region of Mopti where Fulani and Dogon live as sympatric ethnic groups and in the Sudanese savannah area where lives mostly the Malinke ethnic group. The study was conducted in 2007 in Koro and in 2008 in Naguilabougou. It included a total 90 Dogon, 42 Fulani and 80 Malinke ethnic groups. Malaria was diagnosed using microscopic examination after Giemsa-staining of thick and thin blood smear. G6PD deficiency (A-^376/202) samples were identified using RFLP (Restriction Fragment Length Polymorphism) assay and analysis of PCR-amplified DNA amplicon. G6PD deficiency (A-^376/202) rate was 11.1%, 2.4%, and 13.3% in Dogon, Fulani, and Malinke ethnic group respectively. Heterozygous state for G6PD (A-^376/202) was found in 7.8% in Dogon; 2.4% in Fulani and 9.3% in Malinke ethnic groups while hemizygous state was found at the frequency of 2.2% in Dogon and 4% in Malinke. No homozygous state was found in our study population.We conclude that G6PD deficiency is not differing significantly between the three ethnic groups, Fulani, Dogon and Malinke.

The Fulani are known to have a lower parasitaemia and less clinical episodes of malaria as compared to the Dogon sympatric ethnic group, living in Mali. Higher circulating malaria-specific antibody titers and increased pro-inflammatory cytokine levels have been shown in Fulani individuals. Several studies have tried to link haptoglobin (Hp) phenotypes with susceptibility to malaria, but without consensus. This study investigated the role of Hp phenotypes and cytokine levels in Dogon and Fulani during asymptomatic Plasmodium falciparum infection.

Malaria still remains a major public health problem in Mali, although disease susceptibility varies between ethnic groups, particularly between the Fulani and Dogon. These two sympatric groups share similar socio-cultural factors and malaria transmission rates, but Fulani individuals tend to show significantly higher spleen enlargement scores, lower parasite prevalence, and seem less affected by the disease than their Dogon neighbours. We have used genetic polymorphisms from malaria-associated genes to investigate associations with various malaria metrics between the Fulanai and Dogon groups. Two cross sectional surveys (transmission season 2006, dry season 2007) were performed. Healthy volunteers from the both ethnic groups (n=939) were recruited in a rural setting. In each survey, clinical (spleen enlargement, axillary temperature, weight) and parasitological data (malaria parasite densities and species) were collected, as well as blood samples. One hundred and sixty six SNPs were genotyped and 5 immunoassays (AMA1, CSP, MSP1, MSP2, total IgE) were performed on the DNA and serum samples respectively. The data confirm the reduced malaria susceptibility in the Fulani, with a higher level of the protective O-blood group, and increased circulating antibody levels to several malaria antigens (p-15). We identified SNP allele frequency differences between the 2 ethnic groups in CD36, IL4, RTN3 and ADCY9. Moreover, polymorphisms in FCER1A, RAD50, TNF, SLC22A4, and IL13 genes were correlated with antibody production (p-value<0.003). Further work is required to understand the mechanisms underpinning these genetic factors.

Recent developments in diagnostic techniques for malaria, particularly DNA probes and sero-immunology, have raised questions as to how these techniques might be used to facilitate malaria diagnosis at the most peripheral levels of the primary health care system. At present, malaria diagnosis is based on the standard microscopic examination of blood films in most field epidemiologic studies and is likely to remain so in the immediate future in Africa. The objective of this study was to assess inter-observer agreement for the examination of Giemsa-stained slides for Plasmodium falciparum parasites.