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Aims: The aim of this study was to assess the impact of hemoglobin polymorphisms and G6PD deficiency on the course of uncomplicated malaria infection in children aged from 2 to 10 years in Burkina Faso. Study Design: The study was conducted as a longitudinal study in Banfora health district. A total of 150 children aged from 2 to 10 years was enrolled and followed up between May 2015 and February 2016. Blood samples were collected at four different time points: before infection (Visit 1), during asymptomatic parasitemia (Visit 2), during symptomatic parasitemia (Visit 3) and three weeks after treatment (Visit 4). Clinical examination, hematology parameters and malaria diagnosis using microscopy were performed. Hemoglobin and G6PD typing were done using PCR-RFLP. Hemoglobin AA genotypes were defined as normal hemoglobin while Hemoglobin AC, AS and SS were defined as abnormal hemoglobin (hb non-AA). Results: The prevalence of hemoglobin (hb) genotypes was 81.21% for AA while hb non-AA genotypes were estimated at 18.79% (12.08% for hbAC, 6.04% for hbAS and 0.67% for HbSC). The prevalence of G6PD genotypes was 89.26% and 10.74% for normal G6PDn and G6PD deficiency respectively. The prevalence of asymptomatic carriers of P. falciparum was not affected neither by the genotypes of Hemoglobin, nor by the G6PD deficiency. Conversely, the risks of developing uncomplicated malaria in G6PD deficiency (G202A) group, was significantly lower (p = 0.04). The results showed a significant difference (p˂0.0001) in the means of P. falciparum parasite densities between asymptomatic and symptomatic phase in Hemoglobin AA genotypes carriers while the means of parasite density was comparable in non-Hemoglobin AA carriers. Conclusion: Our study showed that G6PD deficiency protects against clinical malaria while P. falciparum parasite density increasing was correlated with carrying hemoglobin genotypes AA.

One approach to investigate if human genetic variation influences the selection of Plasmodium falciparum drug resistance is to compare the frequency of resistant infections among human populations differing in their genetic background and living in the same epidemiological context. A further complementary approach consists in comparing drug resistance among subjects differing for genes involved in drug metabolism. Here we report, from malariological surveys performed in Burkina Faso, that the prevalence of P. falciparum chloroquine-resistant infections (pfcrt 76T and/or pfmdr1 86Y alleles) differs among sympatric ethnic groups, being higher in the Mossi and Rimaibe groups than in the Fulani group (odds ratio [OR], 2.24; 95% confidence interval [CI], 1.27-3.92; P = .007). The association analysis revealed that the human CYP2C8*2 variant, known to determine a poor drug metabolizer phenotype, was associated with P. falciparum chloroquine-resistant infections (OR, 1.66; 95% CI, 1.13-2.43; P = .008). This variant is more frequent in the Mossi-Rimaibe group (23.7% ± 1.4%) than in the Fulani group (9.9% ± 2.5%; P = .0003). This study provides an example of how host genetic variation may influence the selection dynamics of a pathogen's drug resistance.

Summary Objectives To examine whether the humoural response to malaria vaccine candidate antigens, Plasmodium falciparum [circumsporozoite repetitive sequence (NANP)5 GLURP fragments (R0 and R2) and MSP3] varies with the level of malaria transmission and to determine whether the antibodies (IgG) present at the beginning of the malaria transmission season protect against clinical malaria. Methods Cross-sectional surveys were conducted to measure antibody response before, at the peak and at the end of the transmission season in children aged 6 months to 10 years in two villages with different levels of malaria transmission. A cohort study was performed to estimate the incidence of clinical malaria. Results Antibodies to these antigens showed different seasonal patterns. IgG concentrations to any of the four antigens were higher in the village with high entomological inoculation rate. Multivariate analysis of combined data from the two villages indicated that children who were classified as responders to the selected antigens were at lower risk of clinical malaria than children classified as non-responders [(NANP)5 (incidence rate ratio (IRR) = 0.65, 95% CI: 0.46–0.92; P = 0.016), R0 (IRR = 0.69, 95% CI: 0.48–0.97; P = 0.032), R2 (IRR = 0.73, 95% CI: 0.50–1.06; P = 0.09), MSP3 (IRR = 0.52, 95% CI: 0.32–0.85; P = 0.009)]. Fitting a model with all four antibody responses showed that MSP3 looked the best malaria vaccine candidate (IRR = 0.63; 95% CI: 0.38–1.05; P = 0.08). Conclusion Antibody levels to the four antigens are affected by the intensity of malaria transmission and associated with protection against clinical malaria. It is worthwhile investing in the development of these antigens as potential malaria vaccine candidates. Objectifs Examiner si la reponse humorale aux antigenes de candidats vaccins de la malaria, P. falciparum (sequence repetitive de la circumsporozoite (NANP)5, fragments GLURP (R0 et R2) et MSP3) varie avec le taux de la transmission de la malaria et determiner si les anticorps (IgG) presents au debut de la saison de transmission de la malaria protegent contre la malaria clinique. Methodes Etudes transversales pour mesurer la reponse d’anticorps avant, au pic et a la fin de la saison de transmission chez les enfants âges de 6 mois a 10 ans dans deux villages avec des taux differents de transmission de malaria. Une etude de cohorte a ete realisee pour estimer l’incidence de la malaria clinique. Resultats Les anticorps correspondant a ces antigenes montraient differents profils saisonniers. Les taux d’IgG correspondant a chacun des quatre antigenes etaient plus eleves dans le village ayant un taux eleve d’inoculation entomologique. L’analyse multivariee des donnees combinees des deux villages a indique que les enfants classifies comme repondants aux antigenes selectionnes avaient un risque inferieur de malaria clinique par rapport a ceux classifies comme non-repondants [(NANP)5 (IRR = 0,65, IC95%: 0,46–0,92; P = 0,016), R0 (IRR = 0,69, IC95%: 0,48–0,97; P = 0,032), R2 (IRR = 0,73, IC95%: 0,50–1,06; P = 0,09), MSP3 (IRR = 0,52, IC95%: 0,32–0,85; P = 0,009)]. Un modele incorporant chacune des quatre reponses d’anticorps a demontre que MSP3 etait le meilleur candidat vaccin contre la malaria (IRR = 0,63; IC95%: 0,38–1,05; P = 0,08). Conclusion Les taux d’anticorps correspondant aux quatre antigenes sont affectes par l’intensite de la transmission de malaria et associes a la protection contre la malaria clinique. Il serait interessant d’investir dans le developpement de ces antigenes en tant que candidats vaccins potentiels contre la malaria. Objetivos Examinar si la respuesta humoral frente a antigenos de P. falciparum de candidatos a vacunas de malaria (secuencia repetitiva del circumesporozoito (NANP)5, fragmentos GLURP (R0 and R2) y MSP3) varia con el nivel de transmision de malaria y determinar si los anticuerpos (IgG) presentes al comienzo de la estacion de transmision de malaria protegen frente a la malaria clinica. Metodos Se realizaron estudios croseccionales para medir la respuesta de anticuerpos antes, durante el pico y al final de la estacion de transmision en ninos con edades comprendidas entre los 6 meses y 10 anos en dos poblados con diferente nivel de transmision de malaria. Se realizo un estudio de cohortes para estimar la incidencia de malaria clinica. Resultados Los anticuerpos frente a estos antigenos mostraron diferentes patrones estacionales. Las concentraciones de IgG frente a cualquiera de estos cuatro antigenos eran mayores en el poblado con un mayor indice entomologico de inoculacion (IEI). Un analisis multivariado de datos combinados de ambos poblados indico que los ninos clasificados como respondedores a los antigenos seleccionados tenian un menor riesgo de malaria clinica que los ninos clasificados como no respondedores ((NANP)5 (IRR = 0.65, 95%CI: 0.46–0.92; P = 0.016), R0 (IRR = 0.69, 95%CI: 0.48–0.97; P = 0.032), R2 (IRR = 0.73, 95%CI: 0.50–1.06; P = 0.09), MSP3 (IRR = 0.52, 95%CI: 0.32–0.85; P = 0.009)). El utilizar dentro de un modelo los niveles de respuesta a los cuatro anticuerpos mostro que el MSP3 parecia ser el mejor candidato a vacuna (IRR = 0.63; 95%CI: 0.38–1.05; P = 0.08). Conclusion Los niveles de anticuerpos frente a los cuatro antigenos estan afectados por la intensidad de transmision de malaria y asociados a la proteccion frente a malaria clinica. Vale la pena invertir en el desarrollo de estos antigenos como potenciales candidatos a vacunas de malaria.

International audience; Pyruvate kinase (PKLR) is a critical erythrocyte enzyme that is required for glycolysis and production of ATP. We have shown that Pklr deficiency in mice reduces the severity (reduced parasitemia, increased survival) of blood stage malaria induced by infection with Plasmodium chabaudi AS. Likewise, studies in human erythrocytes infected ex vivo with P. falciparum show that presence of host PK-deficiency alleles reduces infection phenotypes. We have characterized the genetic diversity of the PKLR gene, including haplotype structure and presence of rare coding variants in two populations from malaria endemic areas of Thailand and Senegal. We investigated the effect of PKLR genotypes on rich longitudinal datasets including haematological and malaria-associated phenotypes. A coding and possibly damaging variant (R41Q) was identified in the Thai population with a minor allele frequency of ~4.7%. Arginine 41 (R41) is highly conserved in the pyruvate kinase family and its substitution to Glutamine (R41Q) affects protein stability. Heterozygosity for R41Q is shown to be associated with a significant reduction in the number of attacks with Plasmodium falciparum, while correlating with an increased number of Plasmodium vivax infections. These results strongly suggest that PKLR protein variants may affect the frequency, and the intensity of malaria episodes induced by different Plasmodium parasites in humans living in areas of endemic malaria.

Here we address the issue of the possible interplay between host genetic variation and the risk of acquiring Plasmodium falciparum drug-resistant strains. The involvement of human genetic variation as a possible co-factor in the selection and spread of P. falciparum drug resistance is a new tool in the study of malaria and possibly of other infectious diseases. The driving hypothesis of this approach is that parasite drug resistance could be affected both by ethnicity and human variability in the genes encoding for enzymes that metabolise antimalarials (cytochrome P450 liver enzymes). Understanding if parasite drug sensitivity is influenced and possibly modulated by human diversity can contribute to a better knowledge and control of the spread of drug resistance. So far, few studies have addressed this strategic issue. To explore this hypothesis we carried out an association analysis on 506 human/P. falciparum DNA samples from adult asymptomatic subjects belonging to three sympatric ethnic groups of Burkina Faso, an area of hyperendemic malaria in West Africa. Here we report that the prevalence of chloroquine-resistant infections (pfcrt 76T and/or pfmdr1 86Y) differs among sympatric ethnic groups, being higher in Mossi and Rimaibe compared to Fulani (OR: 2.24; 1.27-3.92; P = 0.007). Moreover, the human CYP2C8*2 variant, known to determine a poor drug metaboliser phenotype, is associated with P. falciparum chloroquine-resistant infections (OR: 1.66; 1.13-2.43; P = 0.008). The results strongly suggest that human genetic variation affects the dynamics of selection of parasite drug-resistance. We strongly believe that these observations are of general interest and may have important implications in public health.

We analyzed the humoral immune response to the amino- (amino acids 22-125) and carboxy-terminal (amino acids 289-390) non-repetitive domains of the Plasmodium falciparum circumsporozoite protein (Pf CSP) in individuals belonging to three west African ethnic groups (the Fulani, Mossi, and Rimaibe ´) living in the same conditions of hyperendemic transmission in a Sudan savanna area of Burkina Faso. Previous surveys conducted in the same area showed obvious interethnic differences in the susceptibility and immune reactivity to malaria, with the Fulani showing lower infection and disease rates and higher humoral responses to various P. falciparum antigens than sympatric ethnic groups. A total of 764 subjects (311 Mossi, 273 Rimaibe ´, and 180 Fulani) of all age classes were tested. The total mean 6 SE anti-(CSPf-N-term) and anti-(CSPf-C-term) seroprevalences were 65.6 6 1.7% and 57.0 6 1.8%, respectively. These seroprevalences were lower than that recorded in the same sample for the central (NANP)40 repetitive domain (88.3 6 1.2%). As previously reported for other P. falciparum antigens (Pf CSP- (NANP)40, thrombospondin-related anonymous protein, merozoite surface protein-1, Pf 155-ring-infected eryhtrocyte surface antigen, and Pf 332), in spite of similar exposure to malaria, the Fulani showed higher immune reactivity than sympatric populations for both antigens tested. Our results confirm the presence of B cell epitopes in the non-repetitive regions of the Pf CSP; moreover a further evidence of interethnic differences in the capacity to mount humoral responses against P. falciparum malaria was obtained. The assessment of the biological basis of interethnic hetero- geneities in the susceptibility and in the humoral immune responses to malaria appears relevant in the development of anti-malaria vaccines. The circumsporozoite protein (CSP) is considered to be the major surface antigen of malaria sporozoites. The main structural and antigenic properties of CSP are identical in all Plasmodium species; the molecule contains a species-specif- ic repetitive domain encompassing about 40% of the primary structure of the protein, which corresponds to the B cell im- munodominant epitope. 1 In Plasmodium falciparum,the cen- tral domain contains about 40 repeats of the tetrapeptide NANP plus 3-4 NVDP repeats. The central domain is flanked on both sides by sequences containing conserved regions in different Plasmodium species. 2 The carboxy-ter- minal conserved region (region II) bears a striking homology to a cell adhesion domain of thrombospondin 3,4 and to re- gions of several other adhesive proteins. 5-8 The involvement of CSP in the invasion of sporozoites into hepatocytes has been shown by Cerami and others. 9 The flanking non-repeat

It has been shown that insecticide-treated bed nets or curtains may reduce morbidity and mortality from malaria in hyper-holoendemic areas of sub-Saharan Africa. This protection could partially depend on the transitory imbalance between the anti-malaria immunity acquired by the population before the intervention and the lowered sporozoite load resulting from the anti-vector measure. To verify if the efficacy of the intervention is influenced by the baseline immune status of the population, we compared the protective effect of permethrin-impregnated curtains (PIC) against malaria infection among groups with different baseline levels of anti-malaria immunity. We analyzed the impact of PIC on the Plasmodium falciparum infection rate in two rural villages of Burkina Faso inhabited by three ethnic groups: the Fulani, Mossi, and Rimaibé. These have been previously shown to differ for several malariologic indices, with the Fulani being characterized by lower infection and disease rates and by higher immune response to P. falciparum with respect to the other ethnic groups. The PIC were distributed in June 1996 and their impact on malaria infection was evaluated in groups whose baseline levels of immunity to malaria differed because of their age and ethnic group. Age- and ethnic-dependent efficacy of the PIC was observed. Among the Mossi and Rimaibé, the impact (parasite rate reduction after PIC installation with respect to the pre-intervention surveys) was 18.8% and 18.5%, respectively. A more than two-fold general impact (42.8%) was recorded in the Fulani. The impact of the intervention on infection rates appears positively correlated with the levels of anti-malaria immunity. Since decreased transmission entails a reduction of immunity, the efficacy of the intervention in the long term cannot be taken for granted. The expected complementary role of a hypothetical vaccine is stressed by these results, which also emphasize the importance of the genetic background of the population in the evaluation and application of malaria control strategies.

The humoral immune response against synthetic peptides of two Plasmodium falciparum blood-stage antigens, Pf155/ring-infected erythrocyte surface antigen (RESA) (EENV)6 and Pf332 (SVTEEIAEEDK)2, in individ- uals belonging to three sympatric ethnic groups (Mossi, Rimaibe, and Fulani) living in the same conditions of hyperendemic transmission in a Sudan savanna area northeast of Ouagadougou, Burkina Faso were examined. The Mossi and Rimaibe are Sudanese Negroid populations with a long tradition of sedentary farming, while the Fulani are nomadic pastoralists partly settled and characterized by non-Negroid features of possible Caucasoid origin. A total of 764 subjects (311 Mossi, 273 Rimaibe, and 180 Fulani) were tested. A lower P. falciparum prevalence was observed in the Fulani of all age groups. The serologic results clearly indicate the existence of interethnic differences in the capacity to respond to these two P. falciparum antigens. The Mossi and Rimaibe showed similar responses, whereas the Fulani displayed consistently higher prevalences and levels of antibodies against both epitopes tested. The anti-(EENV) 6 and anti-(SVTEEIAEEDK)2 seroprevalences were 29.9% and 38.9% in Mossi, 29.7% and 39.2% in Rimaibe, 86.1% and 76.1% in Fulani (all P values of Fulani-Mossi and Fulani-Rimaibe comparisons K 0.001). Anti-RESA and anti-Pf332 antibody levels were approximately 65% (P K 0.001) and 45% (P K 0.001), respectively, higher in seropositive Fulani than in seropositive Mossi and Rimaibe, who showed very similar values. The observed differences cannot be explained in terms of interethnic heterogeneity of malaria exposure since these communities have lived in the same area for more than 30 years and the P. falciparum inoculation rate, measured during two consecutive years, was substantially uniform for the three ethnic groups. The possibility of remarkable heterogeneities in the capacity to mount immune responses against P. falciparum antigens among populations with different genetic backgrounds must be taken into account in the development of anti-malaria vaccines. The comparison of the response to Plasmodium falcipa- rum antigens among populations with different genetic back- grounds exposed to high and uniform transmission of the same parasite strains is one of the possible approaches to detect genetically based heterogeneities in the immune re- sponse to malaria. This approach has been recently applied to the study of the anti-circumsporozoite protein (CSP), anti-thrombospondin-related anonymous protein (TRAP), and anti-merozoite surface antigen-1 (MSA-1) immune re- sponses

7 páginas, 3 figuras, 4 tablas.-- et al., The Fulani of west Africa have been shown to be less susceptible to malaria and to mount a stronger immune response to malaria than sympatric ethnic groups. The analysis of HLA diversity is useful for the assessment of the genetic distance between the Fulani and sympatric populations, which represents the necessary theoretical background for the investigation of genetic determinants of susceptibility to malaria. We assessed the polymorphism of HLA-DRB1 and -DQB1 loci and analyzed the distribution of alleles/haplotypes in Fulani, Mossi, and Rimaibé from Burkina Faso. We then investigated the genetic relationship of these three ethnic groups with other sub-Saharan African populations as well as with Europeans. We confirmed that the Fulani from Burkina Faso are genetically distinct from sympatric Mossi and Rimaibé. Furthermore the Fulani from Burkina Faso are close to those from The Gambia and, intriguingly, share the distribution of specific alleles with east African populations (Amhara and Oromo). It is noteworthy that the HLA-DRB1*04 and -DQB1*02 alleles, which are implicated in the development of several autoimmune diseases, are present at high frequency in the Fulani, suggesting their potential involvement in the enhanced immune reactivity observed in this population., This work is part of the activities of the BioMalPar European Network of Excellence supported by a European grant (LSHP-CT- 2004-503578) from the Priority 1 “Life Sciences, Genomics and Biotechnology for Health” in the 6th Framework Programme, and V.D.M. was funded by a BioMalPar PhD Fellowship. This work was further supported by grants from Italian Ministry of Education (COFIN, MIUR-PRIN 2006062857) and Istituto Pasteur–Fondazione Cenci Bolognetti, Sapienza Universitá di Roma.

Burkina Faso has recently changed the antimalarial drug policy to artesunate/amodiaquine or artemether/lumefantrine as the first-line antimalarial drug and sulfadoxine/pyrimethamine for the intermittent preventive treatment in pregnant woman. Before the implementation of this new strategy we conducted an in vivo efficacy study with chloroquine or sulfadoxine/pyrimethamine for treatment of uncomplicated Plasmodium falciparum malaria in urban area of Burkina from September to December 2003. Chloroquine (25 mg/kg over 3 days) or sulfadoxine/pyrimethamine (25 mg/kg + 0.025 mg/kg single dose) was administered respectively to 137 and 125 children aged from 6 to 59 months old in a randomized, opened study. Follow up extended over 28 days using modified WHO protocol. After adjusting the results by PCR, treatment failures rates were 63.4% (83/131) and 13.8% (17/123) respectively for chloroquine and sulfadoxine/pyrimethamine. These results with other observations have justified the change of malaria therapy policy in Burkina Faso in 2005.

Previous interethnic comparative studies on the susceptibility to malaria performed in West Africa showed that Fulani are more resistant to Plasmodium falciparum malaria than are sympatric ethnic groups. This lower susceptibility is not associated to classic malaria-resistance genes, and the analysis of the immune response to P. falciparum sporozoite and blood stage antigens, as well as non-malaria antigens, revealed higher immune reactivity in Fulani. In the present study we compared the expression profile of a panel of genes involved in immune response in peripheral blood mononuclear cells (PBMC) from Fulani and sympatric Mossi from Burkina Faso. An increased expression of T helper 1 (TH1)-related genes (IL-18, IFNγ, and TBX21) and TH2-related genes (IL-4 and GATA3) and a reduced expression of genes distinctive of T regulatory activity (CTLA4 and FOXP3) were observed in Fulani. Microarray analysis on RNA from CD4 + CD25 + (T regulatory) cells, performed with a panel of cDNA probes specific for 96 genes involved in immune modulation, indicated obvious differences between the two ethnic groups with 23% of genes, including TGFβ, TGFβRs, CTLA4, and FOXP3, less expressed in Fulani compared with Mossi and European donors not exposed to malaria. As further indications of a low T regulatory cell activity, Fulani showed lower serum levels of TGFβ and higher concentrations of the proinflammatory chemokines CXCL10 and CCL22 compared with Mossi; moreover, the proliferative response of Fulani to malaria antigens was not affected by the depletion of CD25 + regulatory cells whereas that of Mossi was significantly increased. The results suggest that the higher resistance to malaria of the Fulani could derive from a functional deficit of T regulatory cells.

We have examined Plasmodium falciparum gametocyte prevalence, density and their genetic complexity among children of 2 sympatric ethnic groups (Mossi and Fulani) in villages in Burkina Faso. The 2 groups are known to have distinct differences in their susceptibility and immune responses to malaria. We used RT-PCR and sequence-specific probes to detect and type RNA of the gametocyte-specific protein Pfs48/45. There were no differences in detection rates of asexual forms and gametocytes among the 2 groups, using PCR and RT-PCR, respectively. However, there were significant differences in densities of asexual forms and gametocytes, which were both higher among Mossi than Fulani. Both asexual forms and gametocyte densities were influenced by age and ethnicity. Multiple-clone infections with more than 1 gametocyte genotype were equally prevalent among Fulani and Mossi. These differences can most probably be attributed to genetic differences in malaria susceptibility in the 2 ethnic groups.

We have characterized Plasmodium falciparum genotypes among the Mossi and Fulani sympatric ethnic groups in villages in Burkina Faso during the rainy season. Differences in clinical malaria presentation and in immune responses to malaria occur between the two groups. Asexual parasite rate, density, and gametocyte rate were higher among the Mossi than the Fulani. There was no difference in frequencies of alleles of the P. falciparum merozoite surface protein 1 (msp-1), msp-2, and glutamate-rich protein (glurp) genes among the parasites in each group. However, there were significant differences in the mean number of P. falciparum clones in the two populations, with there being more in the Mossi than in the Fulani. This effect was especially marked in older children. These differences can most probably be attributed to genetic differences in immune responsiveness to malaria between the two ethnic groups.

Previous studies identified an allelic variant of the IL4 promoter region (IL4-589T) that appears to enhance the transcriptional activity of IL4, and is associated with increased IgE levels. Total serum IgE levels are elevated in malaria endemic regions, and higher in children with severe malaria. Here, we investigated the relationship of the IL4-589C/T polymorphism with severity of the disease in a case-control study of severe malaria in Burkina Faso, West Africa. No association between the IL4-589T and severe malaria was observed. No difference in Plasmodium falciparum-specific IgE was detected between severe and uncomplicated malaria patients. Among children with severe malaria, total IgE levels were significantly elevated in those carrying the IL4-589T allele (P = 0.018). In children with uncomplicated malaria, no significant difference was found. These results raise the possibility that there is a relationship between susceptibility to severe malaria, IgE production and genetic variation in the IL4 region, which merits further investigation in other epidemiological settings.

Plasmodium falciparum malaria infection induces elevated blood levels of both total immunoglobulin and anti-plasmodial antibodies belonging to different isotypes. We have previously shown that donors living in areas of malaria transmission develop malaria-specific IgE antibodies that are present at highest concentrations in patients with severe disease, suggesting a role for this isotype in malaria pathogenesis. To establish the possible importance of IgE in the course and severity of this disease, we have analyzed a large and homogenous group of African children (age range = 6 months to 15 years) belonging to one ethnic group (Mossi) living in identical epidemiologic conditions in the same urban area (Ougadougo) of Burkina Faso. While IgG antibodies to P. falciparum increased to high concentrations in very young children and then remained at these levels in older patients, IgE antibodies increased with age, becoming most significantly elevated in children more than four years of age. In older children, those with severe malaria had significantly higher IgE antibody levels than those with non-severe disease. No significant differences between the patient groups were seen for IgG antibodies to P. falciparum. However, when the patients with severe malaria were divided into two groups distinguished by the presence of absence of coma, both IgG and IgE antibodies against malaria were lower in the comatous patients than in the non-comatous patients. The results support the conclusion that IgE antibodies against malaria, regardless of their possible protectivity, also contribute to disease severity in this large and homogenous group of African children.

The Fulani are less clinically susceptible and more immunologically responsive to malaria than neighbouring ethnic groups. Here we report that anti-malarial antibody levels show a wide distribution amongst the Fulani themselves, raising the possibility that quantitative analysis within the Fulani may be an efficient way of screening for important genetic factors. The Th2 cytokine interleukin-4 is an obvious candidate: in Fulani, the IL4-524 T allele is at high frequency and is associated with elevated antibody levels against malaria antigens. These data highlight the possibility of combining inter- and intra-ethnic comparisons to characterize critical determinants of malarial immunity in a natural setting.

The age distribution and the clinical patterns of severe malaria (SM) were compared in patients from urban areas characterized by relatively low transmission, and from rural areas where the mean inoculation rates are at least twenty fold higher. The mean age of the urban and rural patients was 4.8 +/- 3.0 and 2.2 +/- 1.9 respectively (p0.000). The prevalence of coma was higher in the urban subsample (53.6 vs 28.9%, p0.000) while that of severe anemia (hemoglobin5 g/dl) was higher in rural patients (47.4 vs 14.8%, p0.000). Our data, in line with previous results obtained comparing rural areas characterized by different inoculation rates, show that the epidemiological context influences the clinical presentation of SM.

The comparison of malaria indicators among populations with different genetic backgrounds and uniformly exposed to the same parasite strains, is one of the approaches to the study of human heterogeneities in the response to the infection. The results of our comparative studies conducted in Burkina Faso, West Africa, showed consistent interethnic differences in Plasmodium falciparum infection rates, malaria morbidity, prevalence and levels of antibodies to various P. falciparum antigens, and genetic background. The differences in the immune response were not explained by the entomological observations which indicated substantially uniform exposure to infective bites. The presence in the same epidemiological context of individuals characterized by different immune reactivity to malaria represents an ideal opportunity to study the possible relationships between the baseline level of anti-malaria immunity of a population and the protective efficacy of control measures based on the reduction of transmission. In spite of similar reduction of entomological inoculation rates obtained by permethrin-impregnated curtains, ethnic- and age-dependent efficacy was observed. These studies demonstrate the existence of marked interethnic differences in the susceptibility to P. falciparum malaria, probably involving the genetic regulation of humoral immune responses. These differences should be considered in the development of anti-malaria vaccines and in the evaluation and application of malaria control strategies.

We analyzed the clinical presentation of 800 severe malaria cases six months to 15 years of age (mean +/- SD = 4.3 +/- 3.0) recruited at the pediatric ward of the Ouagadougou University Hospital, and at the Sourou and Nayala District Hospitals in Burkina Faso. Inclusion criteria followed the World Health Organization (WHO) definition of severe and complicated malaria. The children were treated according to WHO guidelines with a complete regimen of drugs that were provided free of charge as part of the study. The case fatality rate of each sign and symptom of severe malaria was calculated on the 686 children whose outcomes were known. A total of 95 patients (13.8%) died while in the hospital; the mean +/- SD age of these children was 3.2 +/- 2.1 years. The age distribution and the clinical patterns of severe malaria was compared in patients from the urban areas of Ouagadougou characterized by relatively low transmission, and from rural areas where the mean inoculation rates are at least 20-fold higher. The mean +/- SD age of the urban and rural patients was 4.8 +/- 3.0 and 2.2 +/- 1.9 years, respectively (P < 0.001). The prevalence of coma was higher in the urban subsample (53.6% versus 28.9%; P < 0.001) while that of severe anemia (hemoglobin < 5 g/dL) was higher in rural patients (47.4% versus 14.8%; P < 0.001). Our data, in line with previous results obtained comparing rural areas characterized by different inoculation rates, show that the epidemiologic context influences the clinical presentation of severe malaria.

Plasmodium falciparum parasite rate, parasite density and anti-CS antibodies were assessed in 196 subjects (age10 yrs) belonging to three sympatric West African ethnic groups, namely Mossi, Rimaibé and Fulani, all exposed to very high seasonal malaria transmission in the same rural village near Ouagadougou, Burkina Faso. No interethnic differences were noted in the use of antimalaria measures nor in the exposure to malaria vectors. However, interethnic differences were found in each of the three malariological indices. The Fulani appeared markedly less parasitized and more responsive to the CS-antigen than the Mossi and the Rimaibé who had very similar indices, except in the case of parasite density. These findings suggest a higher resistance to malaria of the Fulani ethnic group, possibly involving human genetic factors and/or the influence of extrinsic variables (e.g., socio-cultural) among which diet differences should be considered.

Burkina Faso has recently changed the antimalarial drug policy to artesunate/amodiaquine or artemether/lumefantrine as the first-line antimalarial drug and sulfadoxine/pyrimethamine for the intermittent preventive treatment in pregnant woman. Before the implementation of this new strategy we conducted an in vivo efficacy study with chloroquine or sulfadoxine/pyrimethamine for treatment of uncomplicated Plasmodium falciparum malaria in urban area of Burkina from September to December 2003. Chloroquine (25 mg/kg over 3 days) or sulfadoxine/pyrimethamine (25 mg/kg + 0.025 mg/kg single dose) was administered respectively to 137 and 125 children aged from 6 to 59 months old in a randomized, opened study. Follow up extended over 28 days using modified WHO protocol. After adjusting the results by PCR, treatment failures rates were 63.4% (83/131) and 13.8% (17/123) respectively for chloroquine and sulfadoxine/pyrimethamine. These results with other observations have justified the change of malaria therapy policy in Burkina Faso in 2005.