Plasmodium falciparum merozoite surface protein 2: epitope mapping and fine specificity of human antibody response against non-polymorphic domains.

BACKGROUND: Two long synthetic peptides representing the dimorphic and constant C-terminal domains of the two allelic families of Plasmodium falciparum merozoite surface proteins 2 are considered promising malaria vaccine candidates. The aim of the current study is to characterize the immune response (epitope mapping) in naturally exposed individuals and relate immune responses to the risk of clinical malaria. METHODS: To optimize their construction, the fine specificity of human serum antibodies from donors of different age, sex and living in four distinct endemic regions was determined in ELISA by using overlapping 20 mer peptides covering the two domains. Immune purified antibodies were used in Western blot and immunofluorescence assay to recognize native parasite derivate proteins. RESULTS: Immunodominant epitopes were characterized, and their distribution was similar irrespective of geographic origin, age group and gender. Acquisition of a 3D7 family and constant region-specific immune response and antibody avidity maturation occur early in life while a longer period is needed for the corresponding FC27 family response. In addition, the antibody response to individual epitopes within the 3D7 family-specific region contributes to protection from malaria infection with different statistical weight. It is also illustrated that affinity-purified antibodies against the dimorphic or constant regions recognized homologous and heterologous parasites in immunofluorescence and homologous and heterologous MSP2 and other polypeptides in Western blot. CONCLUSION: Data from this current study may contribute to a development of MSP2 vaccine candidates based on conserved and dimorphic regions thus bypassing the complexity of vaccine development related to the polymorphism of full-length MSP2.

Seroprevalence and incidence of transfusion-transmitted infectious diseases among blood donors from regional blood transfusion centres in Burkina Faso, West Africa.

BACKGROUND AND OBJECTIVE: The high prevalence of numerous transfusion-transmitted infectious diseases such as HIV, HBV, HCV and syphilis in sub-Saharan Africa affects blood safety for transfusion recipients. The aim of this study was to evaluate the prevalence and incidence of transfusion-transmissible infectious diseases among blood donors in Burkina Faso. METHODS: A retrospective study of blood donors' records from January to December 2009 was conducted. Prevalence and incidence of viral infections were calculated among repeat and first-time blood donors. RESULTS: Of the total of 31405 first-time volunteer blood donors in 2009, 24.0% were infected with at least one pathogen and 1.8% had serological evidence of multiple infections. The seroprevalence of HIV, HBV, HCV and syphilis in first-time volunteer donors was 1.8%, 13.4%, 6.3% and 2.1%, respectively. In 3981 repeat donors, the incidence rate was 3270.2, 5874.1 and 6784.6 per 100000 donations for anti-HIV-1, HBsAg and anti-HCV, respectively. These numbers varied significantly according to populations where blood is collected and blood centres in Burkina Faso. CONCLUSION: The relatively high prevalence of viral markers in first-time volunteers and remarkably high incidence of infections in repeat donors raise concerns regarding the safety of these donors and suggest that implementation of NAT might significantly improve the situation.

HCV prevalence and co-infection with HIV among pregnant women in Saint Camille Medical Centre, Ouagadougou.

OBJECTIVE: To determine hepatitis C virus (HCV) prevalence and the rate of HCV/human immunodeficiency virus (HIV) co-infection in pregnant women attending Saint Camille medical centre (SCMC) in Ouagadougou. METHODS: A total of 607 pregnant women, 16-45 years old, with <32 weeks amenorrhoea were screened for HCV and HIV using rapid tests. The majority of the women included in the study were previously known as HIV infected, as the centre is a reference centre for the programme of prevention against mother-to-child HIV transmission in the country. HCV RNA was extracted and quantified using the cDNA polymerase chain reaction with the nested primers at the 5' untranslated region. Transaminases were measured from plasma samples using spectrophotometric method. RESULTS: Of women, 62.27% were infected with HIV. The prevalence of HCV was 2.14% in the screened pregnant women: 1.75% in HIV-negative women and 2.38% in HIV-positive ones. This prevalence is not significantly different between HIV-positive and HIV-negative pregnant women (P = 0.81). HCV RNA was found in all women with anti-HCV. A significant transaminase increase was noted in women infected with HCV (P = 0.01 and P < 0.01 for glutamic-pyruvic transaminase and glutamic-oxaloacetic transaminase, respectively). Risk factors significantly associated with HCV positivity in pregnant women included transfusion and genital excision. In addition, the infection was linked with the educational level of the women. CONCLUSION: The issue of this study revealed that effort should be made to promote safe medical practices and fight against women genital excision that are found to be the main risk factors associated with the HCV infection.

Immunogenicity of a recombinant fusion construct composed of intrinsically unstructured, low polymorphic segments derived from merozoite surface protein 2 and trophozoite exported protein 1.

To overcome the extensive polymorphism found in human Plasmodium antigens and to avoid the lengthy characterization of their 3 dimensional structure and subsequent production of the native proteins we have been concentrated in large unstructured, non-or low-polymorphic fragments present in the blood stage of P. falciparum. Three fragments derived from the 2 family-specific and constant regions of merozoite surface protein (MSP2) and PFF0165c protein were previously selected for evaluation as potential single vaccine candidates. In order to increase and optimize their potential efficacy against P. falciparum infection the 3 antigens were combined in a single DNA recombinant product (FusN) and compared its antigenicity with that of single antigens in sera of volunteers living in endemic countries. Immunogenicity of the FusN was then compared with that of the mixture of 3 antigens in 3 strains of mice. Antigen specific, affinity purified human antibodies were then tested in antibody dependent cellular inhibition and merozoite opsonization assays. In addition, the antigen specific antibody response and its association with protection from malaria infection were determined. The data collected indicate that the recombinant product is an equal or better antigen /immunogen than fragments used either alone or as a mixture for vaccination in combination with adjuvant. In addition, antibody response to FusN shows a stronger association with protection than single fragments. The use of a single construct as vaccine would drastically reduce the cost of manufacturing and development of the GMP product.

Corrigendum: Diagnostic moléculaire du complexe Mycobacterium tuberculosis résistant à l'isoniazide et à la rifampicine au Burkina Faso.

[This corrects the article DOI: 10.11604/pamj.2015.21.73.5494.].

Role of Ets-1 in transcriptional regulation of transferrin receptor and erythroid differentiation.

High expression of transferrin receptor (TfR) on the membrane of erythroid cells accounts for the high level of iron required to sustain heme synthesis. Several studies indicate that during erythroid differentiation TfR expression is highly dependent on transcriptional regulation. In this study we characterized the minimal region able to confer transcriptional regulation during erythroid differentiation in Friend leukemia cells (FLC). This region of 120 bp, upstream the transcription start site, contains an overlapping consensus recognition sequence for AP1/CREB/ATF transcription factors and for proteins of the Ets family and a GC rich region. Here, we report that both the Ets and the Ap1/CRE like sites are essential for promoter activity during erythroid differentiation. We showed that Ets-1 binds to the EBS-TfR and its binding activity decreases in FLC induced to differentiate and during normal erythroid differentiation. Consistent with this, FLC constitutively expressing Ets-1 show a decrease in TfR gene expression, globin mRNA and hemoglobin synthesis. We conclude that Ets-1 binding activity is modulated during erythroid maturation and that a deregulated expression of this transcription factor interferes with terminal erythroid differentiation.

Prevention of mother-to-child HIV-1 transmission in Burkina Faso: evaluation of vertical transmission by PCR, molecular characterization of subtypes and determination of antiretroviral drugs resistance.

BACKGROUND: Vertical human immunodeficiency virus (HIV) transmission is a public health problem in Burkina Faso. The main objective of this study on the prevention of mother-to-child HIV-1 transmission was to determine the residual risk of HIV transmission in infants born to mothers receiving highly active antiretroviral therapy (HAART). Moreover, we detect HIV antiretroviral (ARV) drug resistance among mother-infant pairs and identify subtypes and circulating recombinant forms (CRF) in Burkina Faso. DESIGN: In this study, 3,215 samples of pregnant women were analyzed for HIV using rapid tests. Vertical transmission was estimated by polymerase chain reaction in 6-month-old infants born to women who tested HIV positive. HIV-1 resistance to ARV, subtypes, and CRFs was determined through ViroSeq kit using the ABI PRISM 3,130 sequencer. RESULTS: In this study, 12.26% (394/3,215) of the pregnant women were diagnosed HIV positive. There was 0.52% (2/388) overall vertical transmission of HIV, with rates of 1.75% (2/114) among mothers under prophylaxis and 0.00% (0/274) for those under HAART. Genetic mutations were also isolated that induce resistance to ARV such as M184V, Y115F, K103N, Y181C, V179E, and G190A. There were subtypes and CRF of HIV-1 present, the most common being: CRF06_CPX (58.8%), CRF02_AG (35.3%), and subtype G (5.9%). CONCLUSIONS: ARV drugs reduce the residual rate of HIV vertical transmission. However, the virus has developed resistance to ARV, which could limit future therapeutic options when treatment is needed. Resistance to ARV therefore requires a permanent interaction between researchers, physicians, and pharmacists, to strengthen the network of monitoring and surveillance of drug resistance in Burkina Faso.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is associated with asymptomatic malaria in a rural community in Burkina Faso.

OBJECTIVE: To investigate 4 combinations of mutations responsible for glucose-6-phosphate dehydrogenase (G6PD) deficiency in a rural community of Burkina Faso, a malaria endemic country. METHODS: Two hundred individuals in a rural community were genotyped for the mutations A376G, G202A, A542T, G680T and T968C using TaqMan single nucleotide polymorphism assays and polymerase chain reaction followed by restriction fragment length polymorphism. RESULTS: The prevalence of the G6PD deficiency was 9.5% in the study population. It was significantly higher in men compared to women (14.3% vs 6.0%, P=0.049). The 202A/376G G6PD A- was the only deficient variant detected. Plasmodium falciparum asymptomatic parasitaemia was significantly higher among the G6PD-non-deficient persons compared to the G6PD-deficient (P<0.001). The asymptomatic parasitaemia was also significantly higher among G6PD non-deficient compared to G6PD-heterozygous females (P<0.001). CONCLUSIONS: This study showed that the G6PD A- variant associated with protection against asymptomatic malaria in Burkina Faso is probably the most common deficient variant.

Plasmodium vivax antigen discovery based on alpha-helical coiled coil protein motif.

Protein α-helical coiled coil structures that elicit antibody responses, which block critical functions of medically important microorganisms, represent a means for vaccine development. By using bioinformatics algorithms, a total of 50 antigens with α-helical coiled coil motifs orthologous to Plasmodium falciparum were identified in the P. vivax genome. The peptides identified in silico were chemically synthesized; circular dichroism studies indicated partial or high α-helical content. Antigenicity was evaluated using human sera samples from malaria-endemic areas of Colombia and Papua New Guinea. Eight of these fragments were selected and used to assess immunogenicity in BALB/c mice. ELISA assays indicated strong reactivity of serum samples from individuals residing in malaria-endemic regions and sera of immunized mice, with the α-helical coiled coil structures. In addition, ex vivo production of IFN-γ by murine mononuclear cells confirmed the immunogenicity of these structures and the presence of T-cell epitopes in the peptide sequences. Moreover, sera of mice immunized with four of the eight antigens recognized native proteins on blood-stage P. vivax parasites, and antigenic cross-reactivity with three of the peptides was observed when reacted with both the P. falciparum orthologous fragments and whole parasites. Results here point to the α-helical coiled coil peptides as possible P. vivax malaria vaccine candidates as were observed for P. falciparum. Fragments selected here warrant further study in humans and non-human primate models to assess their protective efficacy as single components or assembled as hybrid linear epitopes.

Characterisation of hepatitis C virus genotype among blood donors at the regional blood transfusion centre of Ouagadougou, Burkina Faso.

BACKGROUND: Hepatitis C virus (HCV) is responsible for about 900 deaths every year in Burkina Faso. In this country, serological screening for hepatitis B and C viruses is only carried out systematically among blood donors. The aim of this study was to determine the prevalence and genotypes of HCV among blood donors using reverse transcription polymerase chain reaction (PCR) and real-time PCR, respectively. MATERIALS AND METHODS: Serum samples were screened for antibodies to HCV using an enzyme-linked immunosorbent assay (ARCHITECT-i1000SR-ABBOTT). All the reactive samples for HCV antibodies were re-tested using a second enzyme-linked immunosorbent assay (Bio-Rad, Marnes la Coquette, France) for confirmation. RNA was detected in all the reactive samples for antibodies to HCV. HCV RNA positive samples were genotyped using the HCV Real-TM Genotype kit (Sacace Biotechnologies, Italy). RESULTS: Among 2,200 blood donors, the prevalences of antibodies to HCV and viral RNA were 4.4% (95% confidence interval=3.5-5.3) and 1.5% (95% confidence interval=1.0-2.0), respectively. Among HCV RNA carriers, genotyping showed that HCV genotypes 2 and 3 were the most prevalent as they were detected in 18 (56.3%) and 5 (15.6%) individuals, respectively. HCV genotypes 1a and 4 were the least frequent among the blood donors. HCV mixed genotypes 2/3 and 2/4 were also detected among the blood donors. CONCLUSION: The prevalence of HCV found in this study is lower than previously reported prevalences. Large-scale studies are needed to obtain a better picture of the molecular epidemiology of HCV in Burkina Faso.

Efficiency of HAART in the prevention of mother to children HIV-1 transmission at Saint Camille medical centre in Burkina Faso, West Africa.

OBJECTIVE: To evaluate efficiency of HAART in the prevention of mother to child HIV transmission. METHODS: A longitudinal study was conducted on 1 300 women attending the antenatal service at Saint Camille Medical Centre from September 2010 to July 2011. The HIV status of mothers was determined by rapid tests and ELISA. Discordant results were confirmed by real-time PCR. PCR was used to determine HIV status of children born from HIV-positive mothers. RESULTS: Among 1 300 pregnant women tested for HIV, 378 were seropositive. Mothers were predominantly housewives (69.7%), and their mean age was (28.32±0.15) years. The overall prevalence of HIV transmission from mother to child was 4.8% (18/378). This prevalence differed significantly from 0.0% (0/114) to 6.8% (18/264) in children born from mothers under HAART and those with mothers under New Prophylactic Protocol (AZT + 3TC + NVP), respectively (P< 0.01). Children's mortality rate during the medical follow up was 1.3% (5/378). Among 16 women with HIV dubious status by ELISA, the Real Time PCR confirmed 2/16 (12.5%) as HIV positive. CONCLUSIONS: The protocol of prevention of mother to children HIV transmission (PMTCT) is effective. The rate of HIV vertical transmission is significantly reduced. Early diagnosis determined by PCR of children born from HIV-positive mother is necessary and recommended in the context of PMTCT in Burkina Faso. We also found that PCR is an effective tool to confirm HIV status in pregnant women.

Enteric parasites prevalence at Saint Camille Medical Centre in Ouagadougou, Burkina Faso.

OBJECTIVE: To assess the prevalence of parasitic infections among patients attending Saint Camille Medical Centre and to estimate co-parasitic infections rates. METHODS: From January to December 2009, stool samples were collected from 11 728 persons, aged from five months to 72 years and suffering from gastroenteritis. After macroscopic description, the stools were examined by light microscopy to search for the presence of parasites. RESULTS: From the 11 728 analyzed stools, 6 154 (52.47%) were infected with at least one parasite. Protozoan frequently encountered were: Giardia intestinalis (43.47%), Entamoeba histolytica/Entamoeba dispar (30.74%) and Trichomonas intestinalis (21.72%), while Hymenolepis nana (2.25%) was the most common helminth. Co-infections occurred in 22.34% cases. Within the multi-infected samples, dual and triple infections accounted for 71.18% and 20.00%, respectively. Giardia intestinalis for protozoan and Hymenolepis nana for helminths were the most implicated co-infections. CONCLUSIONS: This study confirms that intestinal parasites are still a public health problem in Burkina Faso. To reduce the incidence of parasitic infections, it is necessary to promote the education of people so that they practice the rules of individual and collective hygiene.

Recognition of synthetic polypeptides corresponding to the N- and C-terminal fragments of Plasmodium falciparum Exp-1 by T-cells and plasma from human donors from African endemic areas.

The present work describes the recognition of three synthetic polypeptides encompassing the N- and C-terminal regions of the transmembrane Exp-1 protein of the parasite Plasmodium falciparum by plasma and peripheral blood mononuclear cells from naturally exposed individuals living in African endemic areas. The three polypeptides comprise the sequences 23-105, 73-162 and 101-162, and overlap at the transmembrane domain (73-105). Thus, they permitted characterization of the immune response specific to the N- and C-terminal domains in an independent fashion. Two different populations were evaluated, one in the village of Safo in Mali and the other in the villages of Somnaway, Kabortenga and Toussouktenga in Burkina Faso. Antibodies to the sequence 73-162 of Pf Exp-1 were found in 70% of adult Mali donors and in all of the donors tested from Burkina Faso. Strikingly, the N-terminal fragment Pf Exp-1 23-105 was only weakly recognized by a few donors. Evaluation of the T-cell response indicated that the peptide Pf Exp-1 23-105 was more potent than Pf Exp-1 73-162 in inducing a proliferative response. A correlation between peptide-specific interferon-gamma and interleukin-6 production and proliferation to peptide Pf Exp-1 23-105 was observed. Further studies are needed to evaluate this molecule as a vaccine candidate.