A randomized first-in-human phase I trial of differentially adjuvanted Pfs48/45 malaria vaccines in Burkinabé adults.

BACKGROUNDMalaria transmission-blocking vaccines aim to interrupt the transmission of malaria from one person to another.METHODSThe candidates R0.6C and ProC6C share the 6C domain of the Plasmodium falciparum sexual-stage antigen Pfs48/45. R0.6C utilizes the glutamate-rich protein (GLURP) as a carrier, and ProC6C includes a second domain (Pfs230-Pro) and a short 36-amino acid circumsporozoite protein (CSP) sequence. Healthy adults (n = 125) from a malaria-endemic area of Burkina Faso were immunized with 3 intramuscular injections, 4 weeks apart, of 30 µg or 100 µg R0.6C or ProC6C each adsorbed to Alhydrogel (AlOH) adjuvant alone or in combination with Matrix-M (15 µg or 50 µg, respectively). The allocation was random and double-blind for this phase I trial.RESULTSThe vaccines were safe and well tolerated with no vaccine-related serious adverse events. A total of 7 adverse events, mild to moderate in intensity and considered possibly related to the study vaccines, were recorded. Vaccine-specific antibodies were highest in volunteers immunized with 100 µg ProC6C-AlOH with Matrix-M, and 13 of 20 (65%) individuals in the group showed greater than 80% transmission-reducing activity (TRA) when evaluated in the standard membrane feeding assay at 15 mg/mL IgG. In contrast, R0.6C induced sporadic TRA.CONCLUSIONAll formulations were safe and well tolerated in a malaria-endemic area of Africa in healthy adults. The ProC6C-AlOH/Matrix-M vaccine elicited the highest levels of functional antibodies, meriting further investigation.TRIAL REGISTRATIONPan-African Clinical Trials Registry (https://pactr.samrc.ac.za) PACTR202201848463189.FUNDINGThe study was funded by the European and Developing Countries Clinical Trials Partnership (grant RIA2018SV-2311).

A randomized controlled trial showing safety and efficacy of a whole sporozoite vaccine against endemic malaria.

A highly effective malaria vaccine remains elusive despite decades of research. Plasmodium falciparum sporozoite vaccine (PfSPZ Vaccine), a metabolically active, nonreplicating, whole parasite vaccine demonstrated safety and vaccine efficacy (VE) against endemic P. falciparum for 6 months in Malian adults receiving a five-dose regimen. Safety, immunogenicity, and VE of a three-dose regimen were assessed in adults in Balonghin, Burkina Faso in a two-component study: an open-label dose escalation trial with 32 participants followed by a double-blind, randomized, placebo-controlled trial (RCT) with 80 participants randomized to receive three doses of 2.7 × 106 PfSPZ (N = 39) or normal saline (N = 41) just before malaria season. To clear parasitemia, artesunate monotherapy was administered before first and last vaccinations. Thick blood smear microscopy was performed on samples collected during illness and every 4 weeks for 72 weeks after last vaccinations, including two 6-month malaria transmission seasons. Safety outcomes were assessed in all 80 participants who received at least one dose and VE for 79 participants who received three vaccinations. Myalgia was the only symptom that differed between groups. VE (1 - risk ratio; primary VE endpoint) was 38% at 6 months (P = 0.017) and 15% at 18 months (0.078). VE (1 - hazard ratio) was 48% and 46% at 6 and 18 months (P = 0.061 and 0.018). Two weeks after the last dose, antibodies to P. falciparum circumsporozoite protein and PfSPZ were higher in protected versus unprotected vaccinees. A three-dose regimen of PfSPZ Vaccine demonstrated safety and efficacy against malaria infection in malaria-experienced adults.

Safety and immunogenicity of Vi-typhoid conjugate vaccine co-administration with routine 9-month vaccination in Burkina Faso: A randomized controlled phase 2 trial.

OBJECTIVES: In 2017, the World Health Organisation (WHO) pre-qualified a single-dose typhoid conjugate vaccine (TCV) and identified TCV co-administration studies as a research priority. Accordingly, we tested co-administration of Typbar TCV® (Bharat Biotech International) with measles-rubella (MR) and yellow fever (YF) vaccines. METHODS: We conducted a randomized, double-blind, and controlled, phase 2 trial in Ouagadougou, Burkina Faso. Healthy children aged 9-11 months were randomized 1:1 to receive TCV (Group 1) or control vaccine (inactivated polio vaccine (IPV), Group 2). Vaccines were administered intramuscularly with routine MR and YF vaccines. Safety was assessed by (1) local and systemic reactions on days 0, 3, and 7; (2) unsolicited adverse events within 28 days; and (3) serious adverse events (SAEs) within six months after immunization. RESULTS: We enrolled, randomized, and vaccinated 100 eligible children (49 Group 1 and 51 Group 2). Safety outcomes occurred with similar frequency in both groups: local/solicited reactions (Group 1: 1/49, Group 2: 3/50), systemic/solicited reactions (Group 1: 4/49, Group 2: 9/50), unsolicited adverse events (Group 1: 26/49, Group 2: 33/51), and SAEs (Group 1: 2/49, Group 2: 3/51). TCV conferred robust immunogenicity without interference with MR or YF vaccines. CONCLUSION: TCV can be safely co-administered with MR and YF vaccines to children at the 9-month vaccination visit.

G6PD Polymorphisms and Hemolysis After Antimalarial Treatment With Low Single-Dose Primaquine: A Pooled Analysis of Six African Clinical Trials.

Primaquine (PQ) is an antimalarial drug with the potential to reduce malaria transmission due to its capacity to clear mature Plasmodium falciparum gametocytes in the human host. However, the large-scale roll-out of PQ has to be counterbalanced by the additional risk of drug-induced hemolysis in individuals suffering from Glucose-6-phospate dehydrogenase (G6PD) deficiency, a genetic condition determined by polymorphisms on the X-linked G6PD gene. Most studies on G6PD deficiency and PQ-associated hemolysis focused on the G6PD A- variant, a combination of the two single nucleotide changes G202A (rs1050828) and A376G (rs1050829), although other polymorphisms may play a role. In this study, we tested the association of 20 G6PD single nucleotide polymorphisms (SNPs) with hemolysis measured seven days after low single dose of PQ given at the dose of 0.1 mg/kg to 0.75 mg/kg in 957 individuals from 6 previously published clinical trials investigating the safety and efficacy of this drug spanning five African countries. After adjusting for inter-study effects, age, gender, baseline hemoglobin level, PQ dose, and parasitemia at screening, our analysis showed putative association signals from the common G6PD mutation, A376G [-log10(p-value) = 2.44] and two less-known SNPs, rs2230037 [-log10(p-value] = 2.60), and rs28470352 [-log10(p-value) = 2.15]; A376G and rs2230037 were in very strong linkage disequilibrium with each other (R 2 = 0.978). However, when the effects of these SNPs were included in the same regression model, the subsequent associations were in the borderline of statistical significance. In conclusion, whilst a role for the A- variant is well established, we did not observe an important additional role for other G6PD polymorphisms in determining post-treatment hemolysis in individuals treated with low single-dose PQ.

Bead-based assays to simultaneously detect multiple human inherited blood disorders associated with malaria.

BACKGROUND: Glucose-6-phosphate dehydrogenase deficiency (G6PDd), haemoglobin C (HbC) and S (HbS) are inherited blood disorders (IBD) common in populations in malaria endemic areas. All are associated to some degree with protection against clinical malaria whilst additionally G6PDd is associated with haemolysis following treatment with 8-aminoquinolines. Measuring the prevalence of these inherited blood disorders in affected populations can improve understanding of disease epidemiology. Current methodologies in epidemiological studies commonly rely on individual target amplification and visualization; here a method is presented to simultaneously detect the polymorphisms and that can be expanded to include other single nucleotide polymorphisms (SNPs) of interest. METHODS: Human DNA from whole blood samples was amplified in a novel, multiplex PCR reaction and extended with SNP-specific probes in an allele specific primer extension (ASPE) to simultaneously detect four epidemiologically important human markers including G6PD SNPs (G202A and A376G) and common haemoglobin mutations (HbS and HbC). The products were hybridized to magnetic beads and the median fluorescence intensity (MFI) was read on MAGPIX® (Luminex corp.). Genotyping data was compared to phenotypical data generated by flow cytometry and to established genotyping methods. RESULTS: Seventy-five samples from Burkina Faso (n = 75/78, 96.2%) and 58 samples from The Gambia (n = 58/61, 95.1%) had a G6PD and a HBB genotype successfully assigned by the bead-based assay. Flow cytometry data available for n = 61 samples further supported the concordance between % G6PD normal/deficient cells and genotype. CONCLUSIONS: The bead based assay compares well to alternative measures of genotyping and phenotyping for G6PD. The screening is high throughput, adaptable to inclusion of multiple targets of interest and easily standardized.

First field efficacy trial of the ChAd63 MVA ME-TRAP vectored malaria vaccine candidate in 5-17 months old infants and children.

BACKGROUND: Heterologous prime boost immunization with chimpanzee adenovirus 63 (ChAd63) and Modified Vaccinia Virus Ankara (MVA) vectored vaccines is a strategy previously shown to provide substantial protective efficacy against P. falciparum infection in United Kingdom adult Phase IIa sporozoite challenge studies (approximately 20-25% sterile protection with similar numbers showing clear delay in time to patency), and greater point efficacy in a trial in Kenyan adults. METHODOLOGY: We conducted the first Phase IIb clinical trial assessing the safety, immunogenicity and efficacy of ChAd63 MVA ME-TRAP in 700 healthy malaria exposed children aged 5-17 months in a highly endemic malaria transmission area of Burkina Faso. RESULTS: ChAd63 MVA ME-TRAP was shown to be safe and immunogenic but induced only moderate T cell responses (median 326 SFU/106 PBMC (95% CI 290-387)) many fold lower than in previous trials. No significant efficacy was observed against clinical malaria during the follow up period, with efficacy against the primary endpoint estimate by proportional analysis being 13.8% (95%CI -42.4 to 47.9) at sixth month post MVA ME-TRAP and 3.1% (95%CI -15.0 to 18.3; p = 0.72) by Cox regression. CONCLUSIONS: This study has confirmed ChAd63 MVA ME-TRAP is a safe and immunogenic vaccine regimen in children and infants with prior exposure to malaria. But no significant protective efficacy was observed in this very highly malaria-endemic setting. TRIAL REGISTRATION: ClinicalTrials.gov NCT01635647. Pactr.org PACTR201208000404131.

Efficacy of Olyset Duo, a bednet containing pyriproxyfen and permethrin, versus a permethrin-only net against clinical malaria in an area with highly pyrethroid-resistant vectors in rural Burkina Faso: a cluster-randomised controlled trial.

BACKGROUND: Substantial reductions in malaria incidence in sub-Saharan Africa have been achieved with massive deployment of long-lasting insecticidal nets (LLINs), but pyrethroid resistance threatens control. Burkina Faso is an area with intense malaria transmission and highly pyrethroid-resistant vectors. We assessed the effectiveness of bednets containing permethrin, a pyrethroid, and pyriproxyfen, an insect growth regulator, versus permethrin-only (standard) LLINs against clinical malaria in children younger than 5 years in Banfora, Burkina Faso. METHODS: In this two-group, step-wedge, cluster-randomised, controlled, superiority trial, standard LLINs were incrementally replaced with LLINs treated with permethrin plus pyriproxyfen (PPF) in 40 rural clusters in Burkina Faso. In each cluster, 50 children (aged 6 months to 5 years) were followed up by passive case detection for clinical malaria. Cross-sectional surveys were done at the start and the end of the transmission seasons in 2014 and 2015. We did monthly collections from indoor light traps to estimate vector densities. Primary endpoints were the incidence of clinical malaria, measured by passive case detection, and the entomological inoculation rate. Analyses were adjusted for clustering and for month and health centre. This trial is registered as ISRCTN21853394. FINDINGS: 1980 children were enrolled in the cohort in 2014 and 2157 in 2015. At the end of the study, more than 99% of children slept under a bednet. The incidence of clinical malaria was 2·0 episodes per child-year in the standard LLIN group and 1·5 episodes per child-year in the PPF-treated LLIN group (incidence rate ratio 0·88 [95% CI 0·77-0·99; p=0·04]). The entomological inoculation rate was 85 (95% CI 63-108) infective bites per transmission season in the standard LLIN group versus 42 (32-52) infective bites per transmission season in the PPF-treated LLIN group (rate ratio 0·49, 95% CI 0·32-0·66; p<0·0001). INTERPRETATION: PPF-treated LLINs provide greater protection against clinical malaria than do standard LLINs and could be used as an alternative to standard LLINs in areas with intense transmission of Plasmodium falciparum malaria and highly pyrethroid-resistant vectors. FUNDING: EU Seventh Framework Programme.

Safety of single low-dose primaquine in glucose-6-phosphate dehydrogenase deficient falciparum-infected African males: Two open-label, randomized, safety trials.

BACKGROUND: Primaquine (PQ) actively clears mature Plasmodium falciparum gametocytes but in glucose-6-phosphate dehydrogenase deficient (G6PDd) individuals can cause hemolysis. We assessed the safety of low-dose PQ in combination with artemether-lumefantrine (AL) or dihydroartemisinin-piperaquine (DP) in G6PDd African males with asymptomatic P. falciparum malaria. METHODS AND FINDINGS: In Burkina Faso, G6PDd adult males were randomized to treatment with AL alone (n = 10) or with PQ at 0.25 (n = 20) or 0.40 mg/kg (n = 20) dosage; G6PD-normal males received AL plus 0.25 (n = 10) or 0.40 mg/kg (n = 10) PQ. In The Gambia, G6PDd adult males and boys received DP alone (n = 10) or with 0.25 mg/kg PQ (n = 20); G6PD-normal males received DP plus 0.25 (n = 10) or 0.40 mg/kg (n = 10) PQ. The primary study endpoint was change in hemoglobin concentration during the 28-day follow-up. Cytochrome P-450 isoenzyme 2D6 (CYP2D6) metabolizer status, gametocyte carriage, haptoglobin, lactate dehydrogenase levels and reticulocyte counts were also determined. In Burkina Faso, the mean maximum absolute change in hemoglobin was -2.13 g/dL (95% confidence interval [CI], -2.78, -1.49) in G6PDd individuals randomized to 0.25 PQ mg/kg and -2.29 g/dL (95% CI, -2.79, -1.79) in those receiving 0.40 PQ mg/kg. In The Gambia, the mean maximum absolute change in hemoglobin concentration was -1.83 g/dL (95% CI, -2.19, -1.47) in G6PDd individuals receiving 0.25 PQ mg/kg. After adjustment for baseline concentrations, hemoglobin reductions in G6PDd individuals in Burkina Faso were more pronounced compared to those in G6PD-normal individuals receiving the same PQ doses (P = 0.062 and P = 0.022, respectively). Hemoglobin levels normalized during follow-up. Abnormal haptoglobin and lactate dehydrogenase levels provided additional evidence of mild transient hemolysis post-PQ. CONCLUSIONS: Single low-dose PQ in combination with AL and DP was associated with mild and transient reductions in hemoglobin. None of the study participants developed moderate or severe anemia; there were no severe adverse events. This indicates that single low-dose PQ is safe in G6PDd African males when used with artemisinin-based combination therapy. TRIAL REGISTRATION: Clinicaltrials.gov NCT02174900 Clinicaltrials.gov NCT02654730.

Resistance to malaria through structural variation of red blood cell invasion receptors.

The malaria parasite Plasmodium falciparum invades human red blood cells by a series of interactions between host and parasite surface proteins. By analyzing genome sequence data from human populations, including 1269 individuals from sub-Saharan Africa, we identify a diverse array of large copy-number variants affecting the host invasion receptor genes GYPA and GYPB We find that a nearby association with severe malaria is explained by a complex structural rearrangement involving the loss of GYPB and gain of two GYPB-A hybrid genes, which encode a serologically distinct blood group antigen known as Dantu. This variant reduces the risk of severe malaria by 40% and has recently increased in frequency in parts of Kenya, yet it appears to be absent from west Africa. These findings link structural variation of red blood cell invasion receptors with natural resistance to severe malaria.

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.

Single low dose primaquine to reduce gametocyte carriage and Plasmodium falciparum transmission after artemether-lumefantrine in children with asymptomatic infection: a randomised, double-blind, placebo-controlled trial.

BACKGROUND: A single low dose (0.25 mg/kg) of primaquine is recommended as a gametocytocide in combination with artemisinin-based combination therapies for Plasmodium falciparum but its effect on post-treatment gametocyte circulation and infectiousness to mosquitoes has not been quantified. METHODS: In this randomised, double-blind, placebo-controlled trial, 360 asymptomatic parasitaemic children aged 2-15 years were enrolled and assigned to receive: artemether-lumefantrine (AL) and a dose of placebo; AL and a 0.25 mg/kg primaquine dose; or AL and a 0.40 mg/kg primaquine dose. On days 0, 2, 3, 7, 10 and 14, gametocytes were detected and quantified by microscopy, Pfs25 mRNA quantitative nucleic acid sequence based amplification (QT-NASBA), and quantitative reverse-transcriptase PCR (qRT-PCR). For a subset of participants, pre- and post-treatment infectiousness was assessed by mosquito feeding assays on days -1, 3, 7, 10 and 14. RESULTS: Both primaquine arms had lower gametocyte prevalences after day 3 compared to the placebo arm, regardless of gametocyte detection method. The mean (95% confidence interval) number of days to gametocyte clearance in children with patent gametocytes on day 0 (N = 150) was 19.7 (14.6 - 24.8), 7.7 (6.3 - 9.1) and 8.2 (6.7 - 9.6) for the AL-placebo, the 0.25 mg/kg primaquine dose and the 0.40 mg/kg primaquine dose arms, respectively. While 38.0% (30/79) of selected gametocytaemic individuals were infectious before treatment, only 1/251 participant, from the AL-placebo group, infected mosquitoes after treatment. CONCLUSIONS: We observed similar gametocyte clearance rates after 0.25 and 0.40 mg/kg primaquine doses. Infectivity to mosquitoes after AL was very low and absent in primaquine arms. CLINICALTRIALS. GOV REGISTRATION: NCT01935882.

Clinical Variation of Plasmodium falciparum eba-175, ama-1, and msp-3 Genotypes in Young Children Living in a Seasonally High Malaria Transmission Setting in Burkina Faso.

The association between P. falciparum eba-175, ama-1, and msp-3 polymorphism in the pathogenicity of malaria disease was investigated. We therefore compared the prevalence of different alleles between symptomatic and asymptomatic malarial children under five years of age living in Burkina Faso. Blood filter papers were collected during the 2008 malaria transmission season from 228 symptomatic and 199 asymptomatic children under five years of age. All patients were living in the rural area of Saponé at about 50 km from Ouagadougou, the capital city of Burkina Faso. P. falciparum parasite DNA was extracted using QIAGEN kits and the alleles diversity was assessed by a nested PCR. PCR products were then digested by restriction enzymes based on already described polymorphic regions of the eba-175, ama-1, and msp-3 genes. The individual alleles eba-175_FCR3 and msp-3_K1 frequencies were statistically higher (p < 0.0001) in the asymptomatic group compared to the symptomatic ones. No statistically significant difference was noted in the prevalence of ama-1-3D7, ama-1-K1, and ama-1-HB3 genotypes between the two groups (p > 0.05). The comparative analysis of P. falciparum genotypes indicated that the polymorphism in eba-175 and msp-3 genotypes varied between asymptomatic and symptomatic clinical groups and may contribute to the pathogenesis of malaria.

Novel Insights Into the Protective Role of Hemoglobin S and C Against Plasmodium falciparum Parasitemia.

Although hemoglobin S (HbS) and hemoglobin C (HbC) are well known to protect against severe Plasmodium falciparum malaria, conclusive evidence on their role against infection has not yet been obtained. Here we show, in 2 populations from Burkina Faso (2007-2008), that HbS is associated with a 70% reduction of harboring P. falciparum parasitemia at the heterozygous state (odds ratio [OR] for AS vs AA, 0.27; 95% confidence interval [CI], .11-.66; P = .004). There is no evidence of protection for HbC in the heterozygous state (OR for AC vs AA, 1.49; 95% CI, .69-3.21; P = .31), whereas protection even higher than that observed with AS is observed in the homozygous and double heterozygous states (OR for CC + SC vs AA, 0.04; 95% CI, .01-.29; P = .002). The abnormal display of parasite-adhesive molecules on the surface of HbS and HbC infected erythrocytes, disrupting the pathogenic process of sequestration, might displace the parasite from the deep to the peripheral circulation, promoting its elimination at the spleen level.

Is Fc gamma receptor IIA (FcγRIIA) polymorphism associated with clinical malaria and Plasmodium falciparum specific antibody levels in children from Burkina Faso?

In the present study, the influences of FcγRIIA polymorphism on susceptibility to malaria and antibody responses to Plasmodium falciparum antigens were analyzed in children. We recruited 96 healthy children between 3 and 10 years at the beginning of the high transmission season and we followed up for 5 months through the high transmission season to assess the parasitological, immunological and genetic endpoints in relation to clinical malaria status. There was a similar distribution of homozygous and heterozygous individuals carrying the FcγRIIA-131R/R and FcγRIIA-131R/H allele, whereas the number of FcγRIIA-131H/H homozygous individuals was lower. P. falciparum infection frequency was not associated with the FcγRIIa-131R/H polymorphism. Only IgG antibody responses to GLURP R0 showed a significant association between antibody levels and FcγRIIA polymorphism (p=0.02). IgG levels to MSP2a were significantly higher in children who did not experience any clinical malaria episode compared to those who experienced at least one malaria episode (p=0.019). Cytophilic and non-cytophylic IgG subclass levels were higher in children without malaria than those who experienced at least one malaria episode. This difference was statistically significant for IgG1 to MSP3 (p=0.003) and to MSP2a (p=0.006); IgG3 to MSP2a (p=0.007) and to GLURP R0 (p=0.044); IgG2 to MSP2b (p=0.007) and IgG4 to MSP3 (p=0.051) and to MSP2a (p=0.049). In this study, homozygous carriers of the FcγRIIA-131R/R allele had higher malaria-specific antibody levels compare to the heterozygous carriers FcγRIIA-131R/H alleles and to homozygous carriers of FcγRIIA-131H/H alleles. The pre-existing antibodies responses were related to a reduced subsequent risk of clinical malaria.

Efficacy and safety of the mosquitocidal drug ivermectin to prevent malaria transmission after treatment: a double-blind, randomized, clinical trial.

BACKGROUND: Artemisinin combination therapy effectively clears asexual malaria parasites and immature gametocytes but does not prevent posttreatment malaria transmission. Ivermectin (IVM) may reduce malaria transmission by killing mosquitoes that take blood meals from IVM-treated humans. METHODS: In this double-blind, placebo-controlled trial, 120 asymptomatic Plasmodium falciparum parasite carriers were randomized to receive artemether-lumefantrine (AL) plus placebo or AL plus a single or repeated dose (200 µg/kg) of ivermectin (AL-IVM1 and AL-IVM2, respectively). Mosquito membrane feeding was performed 1, 3, and 7 days after initiation of treatment to determine Anopheles gambiae and Anopheles funestus survival and infection rates. RESULTS: The AL-IVM combination was well tolerated. IVM resulted in a 4- to 7-fold increased mortality in mosquitoes feeding 1 day after IVM (P < .001). Day 7 IVM plasma levels were positively associated with body mass index (r = 0.57, P < .001) and were higher in female participants (P = .003), for whom An. gambiae mosquito mortality was increased until 7 days after a single dose of IVM (hazard rate ratio, 1.34 [95% confidence interval, 1.07-1.69]; P = .012). Although we found no evidence that IVM reduced Plasmodium infection rates among surviving mosquitoes, the mosquitocidal effect of AL-IVM1 and AL-IVM2 resulted in 27% and 35% reductions, respectively, in estimated malaria transmission potential during the first week after initiation of treatment. CONCLUSIONS: We conclude that IVM can be safely given in combination with AL and can reduce the likelihood of malaria transmission by reducing the life span of feeding mosquitoes. CLINICAL TRIALS REGISTRATION: NCT0160325.

A phase 1b randomized, controlled, double-blinded dosage-escalation trial to evaluate the safety, reactogenicity and immunogenicity of an adenovirus type 35 based circumsporozoite malaria vaccine in Burkinabe healthy adults 18 to 45 years of age.

BACKGROUND: Ad35.CS.01 is a pre-erythrocytic malaria candidate vaccine. It is a codon optimized nucleotide sequence representing the P. falciparum circumsporozoite (CS) surface antigen inserted in a replication deficient Adenovirus 35 backbone. A Phase 1a trial has been conducted in the USA in naïve adults and showed that the vaccine was safe. The aim of this study is to assess the safety and immunogenicity of ascending dosages in sub Saharan Africa. METHODS: A double blind, randomized, controlled, dose escalation, phase Ib trial was conducted in a rural area of Balonghin, the Saponé health district (Burkina Faso). Forty-eight healthy adults aged 18-45 years were randomized into 4 cohorts of 12 to receive three vaccine doses (day 0, 28 and 84) of 10(9), 10(10), 5X10(10), 10(11) vp of Ad35.CS.01 or normal saline by intra muscular injection. Subjects were monitored carefully during the 14 days following each vaccination for non serious adverse events. Severe and serious adverse events were collected throughout the participant study duration (12 months from the first vaccination). Humoral and cellular immune responses were measured on study days 0, 28, 56, 84, 112 and 140. RESULTS: Of the forty-eight subjects enrolled, forty-four (91.7%) received all three scheduled vaccine doses. Local reactions, all of mild severity, occurred in thirteen (27.1%) subjects. Severe (grade 3) laboratory abnormalities occurred in five (10.4%) subjects. One serious adverse event was reported and attributed to infection judged unrelated to vaccine. The vaccine induced both antibody titers and CD8 T cells producing IFNγ and TNFα with specificity to CS while eliciting modest neutralizing antibody responses against Ad35. CONCLUSION: Study vaccine Ad35.CS.01 at four different dose levels was well-tolerated and modestly immunogenic in this population. These results suggest that Ad35.CS.01 should be further investigated for preliminary efficacy in human challenge models and as part of heterologous prime-boost vaccination strategies. TRIAL REGISTRATION: ClinicalTrials.gov NCT01018459 http://clinicaltrials.gov/ct2/show/NCT01018459.

Malaria morbidity in high and seasonal malaria transmission area of Burkina Faso.

BACKGROUND: Malariometric parameters are often primary endpoints of efficacy trials of malaria vaccine candidates. This study aims to describe the epidemiology of malaria prior to the conduct of a series of drug and vaccine trials in a rural area of Burkina Faso. METHODS: Malaria incidence was prospectively evaluated over one year follow-up among two cohorts of children aged 0-5 years living in the Saponé health district. The parents of 1089 children comprising a passive case detection cohort were encouraged to seek care from the local health clinic at any time their child felt sick. Among this cohort, 555 children were randomly selected for inclusion in an active surveillance sub-cohort evaluated for clinical malaria during twice weekly home visits. Malaria prevalence was evaluated by cross-sectional survey during the low and high transmission seasons. RESULTS: Number of episodes per child ranged from 0 to 6 per year. Cumulative incidence was 67.4% in the passive and 86.2% in the active cohort and was highest among children 0-1 years. Clinical malaria prevalence was 9.8% in the low and 13.0% in the high season (p>0.05). Median days to first malaria episode ranged from 187 (95% CI 180-193) among children 0-1 years to 228 (95% CI 212, 242) among children 4-5 years. The alternative parasite thresholds for the malaria case definition that achieved optimal sensitivity and specificity (70-80%) were 3150 parasites/µl in the high and 1350 parasites/µl in the low season. CONCLUSION: Clinical malaria burden was highest among the youngest age group children, who may represent the most appropriate target population for malaria vaccine candidate development. The pyrogenic threshold of parasitaemia varied markedly by season, suggesting a value for alternative parasitaemia levels in the malaria case defintion. Regional epidemiology of malaria described, Sapone area field centers are positioned for future conduct of malaria vaccine trials.

Haemoglobin variants and Plasmodium falciparum malaria in children under five years of age living in a high and seasonal malaria transmission area of Burkina Faso.

BACKGROUND: Genetic factors play a key role in determining resistance/susceptibility to infectious disease. Susceptibility of the human host to malaria infection has been reported to be influenced by genetic factors, which could be confounders if not taken into account in the assessment of the efficacy of interventions against malaria. This study aimed to assess the relationship between haemoglobin genotypes and malaria in children under five years in a site being characterized for future malaria vaccine trials. METHODS: The study population consisted of 452 children living in four rural villages. Hb genotype was determined at enrolment. Clinical malaria incidence was evaluated over a one-year period using combined active and passive surveillance. Prevalence of infection was evaluated via bi-annual cross-sectional surveys. At each follow-up visit, children received a brief clinical examination and thick and thin blood films were prepared for malaria diagnosis. A clinical malaria was defined as Plasmodium falciparum parasitaemia >2,500 parasites/µl and axillary temperature ≥37.5°C or reported fever over the previous 24 hours. RESULTS: Frequencies of Hb genotypes were 73.2% AA; 15.0% AC; 8.2% AS; 2.2% CC; 1.1% CS and 0.2% SS. Prevalence of infection at enrolment ranged from 61.9%-54.1% among AA, AC and AS children. After one year follow-up, clinical malaria incidence (95% CI) (episodes per person-year) was 1.9 (1.7-2.0) in AA, 1.6 (1.4-2.1) in AC, and 1.7 (1.4-2.0) in AS children. AC genotype was associated with lower incidence of clinical malaria relative to AA genotype among children aged 1-2 years [rate ratio (95% CI) 0.66 (0.42-1.05)] and 2-3 years [rate ratio (95% CI) 0.37 (0.18-0.75)]; an association of opposite direction was however apparent among children aged 3-4 years. AS genotype was associated with lower incidence of clinical malaria relative to AA genotype among children aged 2-3 years [rate ratio (95% CI) 0.63 (0.40-1.01)]. CONCLUSIONS: In this cohort of children, AC or AS genotype was associated with lower risk of clinical malaria relative to AA genotype only among children aged one to three years. It would be advisable for clinical studies of malaria in endemic regions to consider haemoglobin gene differences as a potentially important confounder, particularly among younger children.

Transplacental Transmission of Plasmodium falciparum in a Highly Malaria Endemic Area of Burkina Faso.

Malaria congenital infection constitutes a major risk in malaria endemic areas. In this study, we report the prevalence of transplacental malaria in Burkina Faso. In labour and delivery units, thick and thin blood films were made from maternal, placental, and umbilical cord blood to determine malaria infection. A total of 1,309 mother/baby pairs were recruited. Eighteen cord blood samples (1.4%) contained malaria parasites (Plasmodium falciparum). Out of the 369 (28.2%) women with peripheral positive parasitemia, 211 (57.2%) had placental malaria and 14 (3.8%) had malaria parasites in their umbilical cord blood. The umbilical cord parasitemia levels were statistically associated with the presence of maternal peripheral parasitemia (OR = 9.24, P ≪ 0.001), placental parasitemia (OR = 10.74, P ≪ 0.001), high-density peripheral parasitemia (OR = 9.62, P ≪ 0.001), and high-density placental parasitemia (OR = 4.91, P = 0.03). In Burkina Faso, the mother-to-child transmission rate of malaria appears to be low.

Genetic diversity of polymorphic vaccine candidate antigens (apical membrane antigen-1, merozoite surface protein-3, and erythrocyte binding antigen-175) in Plasmodium falciparum isolates from western and central Africa.

The malaria vaccine candidate antigens erythrocyte binding antigen 175 (EBA-175), merozoite surface protein 3 (MSP-3), and apical membrane antigen (AMA-1) from Plasmodium falciparum isolates from countries in central and west Africa were assessed for allelic diversity. Samples were collected on filter paper from 600 P. falciparum-infected symptomatic patients in Cameroon, Republic of Congo, Burkina Faso, Ghana, and Senegal and screened for class-specific amplification fragments. Genetic diversity, assessed by mean heterozygosity, was comparable among countries. We detected a clinical increase in eba 175 F-allele frequency from west to east across the study region. No statistical difference in msp-3 allele distribution between countries was observed. The ama-1 3D7 alleles were present at a lower frequency in central Africa than in West Africa. We also detected little to no genetic differentiation among sampling locations. This finding indicates that, at least at the level of resolution offered by restriction fragment length polymorphism analysis, these antigens showed remarkable genetic homogeneity throughout the region sampled, perhaps caused by balancing selection to maintain a diverse array of antigen haplotyes.