Safety, reactogenicity and immunogenicity of a booster dose of the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) in Malian children

BACKGROUND

Primary vaccination with the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) was previously shown to be immunogenic and well tolerated in Malian children. Data on booster vaccination with a fourth consecutive dose of PHiD-CV are available for Europe, Asia and Latin America but are lacking for Africa. The present study evaluated further the safety, reactogenicity and immunogenicity of a fourth consecutive (booster) dose of PHiD-CV.

RESULTS

Low incidences of AEs with grade 3 intensity (2.1% of subjects) were observed. There were no reports of large swelling reactions and serious adverse events. One month post-booster vaccination, for each vaccine pneumococcal serotype, at least 97.8% of subjects had antibody concentrations ≥ 0.2 μg/ml, and at least 97.1% of subjects had opsonophagocytic activity ≥ 8. From pre- to post-booster, a 12.3-fold increase in anti-protein D geometric mean concentration was observed.

METHODS

This phase III, open-label study was conducted in Ouelessebougou, Mali, between November 2009 and June 2010. The study population consisted of Malian children previously primed (3 doses) with PHiD-CV in study NCT00678301 receiving a fourth consecutive (booster) dose of PHiD-CV in the second year of life. The incidences of adverse events (AEs) with grade 3 intensity (primary objective) or of any intensity (secondary objective), and the immunogenicity (secondary objective) of the PHiD-CV booster dose were assessed.

CONCLUSION

A booster dose of PHiD-CV was well tolerated when administered to Malian children in the second year of life and was highly immunogenic for all 10 vaccine pneumococcal serotypes and NTHi protein D. (ClinicalTrials.gov identifier: NCT00985465).

Plasmodium vivax malaria in Mali: a study from three different regions

Background

Plasmodium vivax has traditionally been considered virtually absent from Western and Central Africa, due to the absence of the Duffy blood group in most of the population living in these areas. Recent reports, however, suggest the circulation of P. vivax in sub-Saharan Africa.

Methods

Giemsa/Field-stained smears from febrile patients recruited in five different cities (Goundam, Tombouctou, Gao, Bourem and Kidal) pertaining to three regions from Northern Mali were examined. Nested-PCR and DNA sequence analyses of selected samples were performed to fully confirm the presence of P. vivax infections.

Results

Results demonstrated the presence of P. vivax infections in close to 30% of the cases as detected by Giemsa/Field-stained smears and nested-PCR and DNA-sequence analyses of selected samples unequivocally confirmed the presence of P. vivax.

Conclusions

The diagnostics of this human malaria parasite should be taken into account in the context of malaria control and elimination efforts, not only in Mali, but also in sub-Saharan Africa.

Candidate polymorphisms and severe malaria in a Malian population

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

Results of an action-research on epilepsy in rural Mali

Purpose

To evaluate the RARE (Réseau Action-Recherche sur l’Epilepsie) program, a model of managing and treating people with epilepsy (PWE) at a primary health-care level in rural areas of Mali, we assessed treatment efficacy and compliance of patients who underwent the first year follow-up.

Methods

A network of rural general practitioners (GPs) settled in six rural districts of the regions of Koulikoro, Segou and Sikasso, was involved in the diagnosis, evaluation and monitoring of all the identified PWE and in the distribution of phenobarbital (PB). All the participants were included in a prospective database and followed-up by GPs at 4 months intervals during the first year. Seizure frequency, treatment doses and appearance of adverse events (AEs) were systematically recorded. Efficacy was evaluated in terms of reduction of seizures frequency while noncompliance in terms of time to study withdrawal for any cause.

Key findings

596 patients treated with PB were included in the analysis. Of these, 74.0% completed the first year follow-up. At the final visit, 59.6% were seizure-free: 31.0% for 12 months, 10.2% for 8 months and 18.4% for 4 months. Adults and patients with convulsive seizures were the most drug-resistant (p<0.002). Few AEs were recorded. The multivariate analysis showed that being a woman, presenting convulsive seizures, having more than 5 seizures/month and had never be treated were predictors of withdrawal (p≤0.05) at 12 months.

Significance

This study showed a good response and compliance to the treatment and allowed the identification of some factors associated with failure of management in a setting very near to clinical practice. Awareness campaigns are needed to assure a broader accessibility to treatment and to improve the compliance and continuity with treatment programs.

[Place of malaria among febrile illnesses in two ethnic tribes living in sympatry in Mali from 1998 to 2008]

In Africa, malaria is responsible for 25-40% of all outpatient visits and 20-50% of all hospitalizations. In malaria-endemic areas, individuals do not behave the same toward the outcome of clinical malaria. The aim of this study is to determine the prevalence of malaria in the locality among the different ethnic groups, evaluate the place of malaria among febrile illnesses, and assess the relationship between fever and parasite density of Plasmodium falciparum. Studies on susceptibility to malaria between the Fulani and Dogon groups in Mali were conducted in Mantéourou and the surrounding villages from 1998 to 2008. We carried out six cross-sectional studies during the malaria transmission and longitudinal surveys (July to December depending on the year) during the 10-year duration. In longitudinal studies, clinical data on malaria and other diseases frequently observed in the population were recorded. It appears from this work that malaria is the leading cause of febrile syndromes. We observed a significant reduction in malaria morbidity in the study population from 1998 to 2008. The pyrogenic threshold of parasitaemia was 1,000 parasites/mm(3) of blood in the Dogon and 5,000 parasites/mm(3) of blood in the Fulani.We have also found that high parasitical densities were not always associated with fever. Malaria morbidity was higher among the Dogon than in Fulani. The immunogenetic factors might account for this difference in susceptibility to malaria between Fulani and Dogon in the area under study. With regard to this study, it is important to take into account the ethnic origin of subjects when interpreting data of clinical and malarial vaccine trials.

Mosquito feeding assays to determine the infectiousness of naturally infected Plasmodium falciparum gametocyte carriers

Introduction

In the era of malaria elimination and eradication, drug-based and vaccine-based approaches to reduce malaria transmission are receiving greater attention. Such interventions require assays that reliably measure the transmission of Plasmodium from humans to Anopheles mosquitoes.

Methods

We compared two commonly used mosquito feeding assay procedures: direct skin feeding assays and membrane feeding assays. Three conditions under which membrane feeding assays are performed were examined: assays with i) whole blood, ii) blood pellets resuspended with autologous plasma of the gametocyte carrier, and iii) blood pellets resuspended with heterologous control serum.

Results

930 transmission experiments from Cameroon, The Gambia, Mali and Senegal were included in the analyses. Direct skin feeding assays resulted in higher mosquito infection rates compared to membrane feeding assays (odds ratio 2.39, 95% confidence interval 1.94–2.95) with evident heterogeneity between studies. Mosquito infection rates in membrane feeding assays and direct skin feeding assays were strongly correlated (p<0.0001). Replacing the plasma of the gametocyte donor with malaria naïve control serum resulted in higher mosquito infection rates compared to own plasma (OR 1.92, 95% CI 1.68–2.19) while the infectiousness of gametocytes may be reduced during the replacement procedure (OR 0.60, 95% CI 0.52–0.70).

Conclusions

Despite a higher efficiency of direct skin feeding assays, membrane feeding assays appear suitable tools to compare the infectiousness between individuals and to evaluate transmission-reducing interventions. Several aspects of membrane feeding procedures currently lack standardization; this variability makes comparisons between laboratories challenging and should be addressed to facilitate future testing of transmission-reducing interventions.

Analysis of Plasmodium falciparum diversity in natural infections by deep sequencing

Malaria elimination strategies require surveillance of the parasite population for genetic changes that demand a public health response, such as new forms of drug resistance. Here we describe methods for the large-scale analysis of genetic variation in Plasmodium falciparum by deep sequencing of parasite DNA obtained from the blood of patients with malaria, either directly or after short-term culture. Analysis of 86,158 exonic single nucleotide polymorphisms that passed genotyping quality control in 227 samples from Africa, Asia and Oceania provides genome-wide estimates of allele frequency distribution, population structure and linkage disequilibrium. By comparing the genetic diversity of individual infections with that of the local parasite population, we derive a metric of within-host diversity that is related to the level of inbreeding in the population. An open-access web application has been established for the exploration of regional differences in allele frequency and of highly differentiated loci in the P. falciparum genome.

Changes in the levels of cytokines, chemokines and malaria-specific antibodies in response to Plasmodium falciparum infection in children living in sympatry in Mali

BACKGROUND

The Fulani are known to be less susceptible to Plasmodium falciparum malaria as reflected by lower parasitaemia and fewer clinical symptoms than other sympatric ethnic groups. So far most studies in these groups have been performed on adults, which is why little is known about these responses in children. This study was designed to provide more information on this gap.

METHODS

Circulating inflammatory factors and antibody levels in children from the Fulani and Dogon ethnic groups were measured. The inflammatory cytokines; interleukin (IL)-1beta, IL-6, IL-8, IL-10, IL-12p70, tumor necrosis factor (TNF) and the chemokines; regulated on activation normal T cell expressed and secreted (RANTES), monokine-induced by IFN-gamma (MIG), monocyte chemotactic protein (MCP)-1 and IFN-gamma-inducible protein (IP)-10 were measured by cytometric bead arrays. The levels of interferon (IFN)-alpha, IFN-gamma and malaria-specific antibodies; immunoglobulin (Ig) G, IgM and IgG subclasses (IgG1-IgG4) were measured by ELISA.

RESULTS

The results revealed that the Fulani children had higher levels of all tested cytokines compared to the Dogon, in particular IFN-gamma, a cytokine known to be involved in parasite clearance. Out of all the tested chemokines, only MCP-1 was increased in the Fulani compared to the Dogon. When dividing the children into infected and uninfected individuals, infected Dogon had significantly lower levels of RANTES compared to their uninfected peers, and significantly higher levels of MIG and IP-10 as well as MCP-1, although the latter did not reach statistical significance. In contrast, such patterns were not seen in the infected Fulani children and their chemokine levels remained unchanged upon infection compared to uninfected counterparts. Furthermore, the Fulani also had higher titres of malaria-specific IgG and IgM as well as IgG1-3 subclasses compared to the Dogon.

CONCLUSIONS

Taken together, this study demonstrates, in accordance with previous work, that Fulani children mount a stronger inflammatory and antibody response against P. falciparum parasites compared to the Dogon and that these differences are evident already at an early age. The inflammatory responses in the Fulani were not influenced by an active infection which could explain why less clinical symptoms are seen in this group.

The implementation of malaria intermittent preventive trialtreatment with sulphadoxine-pyrimethamine in infants reduced all-cause mortality in the district of Kolokani, Mali: results from a cluster randomized control

Background

Malaria intermittent preventive treatment of malaria in infant with sulphadoxine-pyrimethamine (IPTi-SP) reduced the incidence of malaria and anaemia by 30% and 20% respectively. The strategy is now a recommended policy for malaria control. However, there was no published study on the impact of the strategy on mortality. The present study assessed the impact of the implementation of IPTi-SP in health services in Mali on all-cause mortality.

Methods

The 22 health sub-districts of the district of Kolokani were randomized at a 1:1 ratio to either receive IPTi-SP or to serve as a control. The IPTi-SP was implemented for two years starting December 2006. Information on births and deaths through 31 March, 2009 was collected on all children who reached four months of age on 1 December, 2006, likely to be exposed to the intervention in 75 localities randomly selected in each zone.

Results

A total of 5,882 children (2,869 from the intervention zone and 3,013 from the nonintervention zone) who reached four months of age between 1 December, 2006 and 1 December, 2008 were surveyed between the age of four months to the age of 18 months from 1 December, 2006 to 31 March, 2009. In the cohort of four to 18 months of age, the mortality rate per 1,000 children was 2.53 in the intervention zone compared to 3.46 in the nonintervention zone, gender and season adjusted mortality rate ratio (MRR) = 0.73 (95% CI 0.55-0.97, p = 0.029). In the cohort of the four to 12 months of age, mortality rates per 1,000 children were 2.22 in the intervention zone and 3.13 in the non-intervention zone, MRR = 0.71 (95% CI 0.49-1.02, p = 0.064) adjusted for gender and season.

Conclusion

The implementation of the IPTi-SP resulted in a substantial reduction in all-cause mortality in children. The results of this study support the adoption and the implementation of IPTi-SP as malaria control strategy.

Trial Registration

ClinicalTrials.govNCT00766662

Blood stage vaccines for Plasmodium falciparum: current status and the way forward

Since the recent call for a shift from malaria control to eradication, the role of asexual blood stage vaccines for falciparum malaria, which are not expected to prevent infection, has become less clear. However, blood stage antigens remain likely to be a critical component of a highly effective malaria vaccine. The inclusion of a blood stage component in a multistage malaria vaccine would not only prevent disease caused by “leaky” pre-erythrocytic immunity, but would also protect against epidemics in newly vulnerable populations. Recent clinical results of blood stage vaccine candidates have shown strain specific and partial efficacy, although no protection against clinical outcomes has been demonstrated in experimental infection or field trials to date. The current status of Plasmodium falciparum blood stage vaccine development is summarized and the potential role of these vaccines in the changed malaria landscape is discussed. Alternative preclinical and clinical development paths will speed iterative development.

Ethical issues in human genomics research in developing countries

BACKGROUND

Genome-wide association studies (GWAS) provide a powerful means of identifying genetic variants that play a role in common diseases. Such studies present important ethical challenges. An increasing number of GWAS is taking place in lower income countries and there is a pressing need to identify the particular ethical challenges arising in such contexts. In this paper, we draw upon the experiences of the MalariaGEN Consortium to identify specific ethical issues raised by such research in Africa, Asia and Oceania.

DISCUSSION

We explore ethical issues in three key areas: protecting the interests of research participants, regulation of international collaborative genomics research and protecting the interests of scientists in low income countries. With regard to participants, important challenges are raised about community consultation and consent. Genomics research raises ethical and governance issues about sample export and ownership, about the use of archived samples and about the complexity of reviewing such large international projects. In the context of protecting the interests of researchers in low income countries, we discuss aspects of data sharing and capacity building that need to be considered for sustainable and mutually beneficial collaborations.

SUMMARY

Many ethical issues are raised when genomics research is conducted on populations that are characterised by lower average income and literacy levels, such as the populations included in MalariaGEN. It is important that such issues are appropriately addressed in such research. Our experience suggests that the ethical issues in genomics research can best be identified, analysed and addressed where ethics is embedded in the design and implementation of such research projects.

Maternal country of origin, breast milk characteristics and potential influences on immunity in offspring

Breast milk contains pro- and anti-inflammatory cytokines and chemokines with potential to influence immunological maturation in the child. We have shown previously that country of birth is associated with the cytokine/chemokine profile of breast milk. In this study we have investigated how these differences in breast milk affect the cellular response of cord blood mononuclear cells (CBMCs) and intestinal epithelial cells (IECs, cell line HT-29) to microbial challenge. Ninety-five women were included: 30 from Mali in West Africa, 32 Swedish immigrants and 33 native Swedish women. CBMCs or IECs were stimulated in vitro with breast milk, alone or in combination with lipopolysaccharide (LPS) or peptidoglycan (PGN). Breast milk in general abrogated the LPS-induced down-regulation of surface CD14 and Toll-like receptor (TLR)-4 expression on CB monocytes, while inhibiting the PGN-induced TLR-2 up-regulation. However, breast milk from immigrant women together with LPS induced a lower CBMC release of interleukin (IL)-6 (P = 0·034) and CXCL-8/IL-8 (P = 0·037) compared with breast milk from Swedish women, while breast milk from Swedish women and Mali women tended to increase the response. The same pattern of CXCL-8/IL-8 release could be seen after stimulation of IECs (HT-29). The lower CBMC and IEC (HT-29) responses to microbial compounds by breast milk from immigrant women could be explained by the fact that breast milk from the immigrant group showed a divergent pro- and anti-inflammatory content for CXCL-8/IL-8, transforming growth factor-β1 and soluble CD14, compared to the other two groups of women. This may have implications for maturation of their children's immune responses.

Association of rs7719175, located in the IL13 gene promoter, with Schistosoma haematobium infection levels and identification of a susceptibility haplotype

Urinary schistosomiasis is a parasitic disease caused by Schistosoma haematobium helminths. S. haematobium eggs may remain trapped within the bladder or the ureter walls, causing major pathological disorders in the urogenital system. The polymorphism rs1800925(C/T) of the IL13 gene promoter, which is functional, has previously been associated with susceptibility to S. haematobium infection. The aim of this study was to further our understanding and to determine whether, in the 5q31-q33 region, rs1800925 affects infection levels alone or in synergy with other polymorphisms. After sequencing the IL13 promoter and increasing the single-nucleotide polymorphism density, we performed a linkage disequilibrium analysis between rs1800925 and the other markers in a Malian population. Multivariate linear regression analysis and electrophoretic mobility shift assay (EMSA) were performed to characterized markers in linkage disequilibrium with rs1800925. An additional polymorphism, rs7719175, in the IL13 promoter was associated with controlling infection levels in multivariate analysis. The haplotype rs7719175T-rs1800925C was associated with high infection levels. EMSA indicated that rs7719175 affects the binding of transcriptional factors to the promoter region. Polymorphisms rs7719175 and rs1800925 have a synergistic role in the control of infection levels caused by S. haematobium and using them as a haplotype allows a better discrimination between infected subjects.

[Immunity in human schistosomiasis: hope for a vaccine]

Schistosomiasis remains a major worldwide public health problem in several endemic areas despite implementation of control measures. Vaccination would be an effective, long-term treatment option for future control of schistosomiasis. Although several parasite antigens have been identified as schistosomiasis vaccine candidates, major hurdles must still be overcome to develop a vaccine suitable for clinical trials in the field. Better understanding of immune responses to Schistosoma infection in both animal models and humans suggests that development of a vaccine is possible. The purpose of this review is to summarize the mechanisms of protective immunity against Schistosoma infection and to provide perspective on the development of a vaccine.

Engaging diverse communities participating in clinical trials: case examples from across Africa

BACKGROUND

In the advent of increasing international collaborative research involving participants drawn from populations with diverse cultural backgrounds, community engagement becomes very critical for the smooth conduction of the research. The African Malaria Network Trust (AMANET) is a pan-African non-governmental organization that sponsors and technically supports malaria vaccine trials in various African countries.

CASE DESCRIPTION

AMANET sponsored phase Ib or IIb clinical trials of several malaria vaccine candidates in various Africa countries. In Burkina Faso, Mali and Tanzania trials of the merozoite surface protein 3 -- in its Long Synthetic Peptide configuration (MSP3 LSP) -- were conducted. In Mali, the apical membrane antigen 1 (AMA1) was tested, while a hybrid of glutamate rich protein (GLURP) and MSP3 (GMZ2) was tested in Gabon. AMANET recognizes the importance of engaging with the communities from which trial participants are drawn, hence community engagement was given priority in all project activities conducted in the various countries.

DISCUSSION AND EVALUATION

Existing local social systems were used to engage the communities from which clinical trial participants were drawn. This article focuses on community engagement activities employed at various AMANET-supported clinical trial sites in different countries, highlighting subtle differences in the approaches used. The paper also gives some general pros and cons of community engagement.

CONCLUSIONS

Community engagement enables two-way sharing of accurate information and ideas between researchers and researched communities, which helps to create an environment conducive to smooth research activities with enhanced sense of research ownership by the communities.

[Snakebites in the Sudanian and Sahelian zones of Mali: epidemiology, symptoms and treatment]

The purpose of this study was to document the epidemiology, symptoms and treatment of snake envenomation in Mali between 2005 and 2006. Data was collected using two methods, i.e., household surveys and retrospective surveys. Household surveys carried out in a village of 597 people showed that the annual average incidence was 164 snakebites per 100,000 inhabitants. Retrospective surveys were conducted in 35 healthcare facilities (5 regional hospitals and 30 district health centers) located in 5 parts of the country. Study periods ranged from 2 to 11 years depending on the location. The mean annual incidence of snakebite including dry-bites without envenomation was 27 per 100,000 inhabitants (range, 15-59). Hospital mortality was 4.7% (67/1433) (range, 2.2-6.7%). The population at risk consisted mainly of working men who accounted for 68.4% (980/1433). Patients between 15 and 30 years accounting for 41.2% (590/1433) of the sample were at highest risk for snakebite (chi2=9.96; p=6.10-3). The frequency of snakebite increased from 9.9% (142/1433) in Mopti in the North to 39.9% (572/1433) in Sikasso in the South (chi2=11.93; p=0,017). Snakebites most frequently occurred during the rainy season (56.6%) but only 0.68% of victims were referred to the health center. Hemorrhagic and inflammatory syndromes were the main complications of envenomation. Treatment was always symptomatic. Antivenom serum requirements ranged from 63 to 200 ampoules per year. Our results show that the frequency of snakebites remains grossly underestimated based on hospital data.

Genetic evidence for the aggravation of Plasmodium falciparum malaria by interleukin 4

BACKGROUND

Severe malaria (SM) due to Plasmodium falciparum causes millions of child deaths in sub-Saharan Africa. It comprises a variety of clinical disorders, including cerebral malaria (CM) and severe anemia (SA). In previous work, we have shown that interferon gamma and interleukin 12 protect against CM. Here, we investigated whether interleukin 4 (IL-4) aggravates the risk of severe disease.

METHODS

We prospectively recruited children with CM (n = 240), SA (n = 101), and uncomplicated malaria (UM) (n = 42) in Bamako, Mali, and measured IL-4 production in plasma by enzyme-linked immunosorbent assay. We then assessed the influence of 11 polymorphisms on predisposition to SM by the family-based association test (FBAT).

RESULTS

IL-4 concentrations were higher in children with CM than in children with UM during malaria (P = .003). FBAT analyses showed that the most significant association was between the IL4 variable-number tandem repeat (VNTR) 1/2 genotype and SM (P < .001); an association was also observed for IL4 -33 C/T, rs2243267 G/C, rs2243268 C/A, and rs2243282 C/A (P < .05). Interestingly, we found that the plasma concentration of IL-4 was higher in subjects with the IL4 VNTR 1/2 or 1/1 genotype than with the IL4 VNTR 2/2 genotype (P = .003).

CONCLUSIONS

These results support the view that IL-4 may be a risk factor for SM. IL-4 may aggravate the disease by interfering with type 1 T helper cell differentiation or by promoting local inflammation at sites of parasite sequestration.

Pharmacokinetics of sulfadoxine and pyrimethamine in intermittent preventive treatment of malaria in pregnancy

Malaria during pregnancy is associated with maternal and fetal morbidity and mortality. In order to minimize the burden, sulfadoxine-pyrimethamine (SP) is widely used in Africa as an intermittent preventive treatment of malaria in pregnancy (IPTp). However, only limited data are available on the pharmacokinetics of sulfadoxine and pyrimethamine during pregnancy. We conducted a prospective, self-matched, multicenter study of 98 pregnant women in four African countries in order to determine the effects of pregnancy on SP pharmacokinetics. After adjusting for the effects of potential confounders, blood concentrations (associated with therapeutic efficacy) of pyrimethamine were higher (geometric mean ratio (GMR) 1.33; 95% confidence interval (CI) 1.18-1.51; P < 0.001) and those of sulfadoxine were lower (GMR 0.91; 95% CI 0.84-0.98; P = 0.013) on day 7 after SP administration during pregnancy than after the postpartum period. SP pharmacokinetic parameters differed significantly among the study sites. Given the inconsistency of changes in pharmacokinetic parameters between sulfadoxine and pyrimethamine as well as among the study sites, it is not possible to recommend any dose adjustment to prolong the therapeutic life span of the fixed dose combination of SP for IPTp on the basis of our study findings.

Caspase-12 and the inflammatory response to Yersinia pestis

Background

Caspase-12 functions as an antiinflammatory enzyme inhibiting caspase-1 and the NOD2/RIP2 pathways. Due to increased susceptibility to sepsis in individuals with functional caspase-12, an early-stop mutation leading to the loss of caspase-12 has replaced the ancient genotype in Eurasia and a significant proportion of individuals from African populations. In African-Americans, it has been shown that caspase-12 inhibits the pro-inflammatory cytokine production.

Methodology/Principal Findings

We assessed whether similar mechanisms are present in African individuals, and whether evolutionary pressures due to plague may have led to the present caspase-12 genotype population frequencies. No difference in cytokine induction through the caspase-1 and/or NOD2/RIP2 pathways was observed in two independent African populations, among individuals with either an intact or absent caspase-12. In addition, stimulations with Yersinia pestis and two other species of Yersinia were preformed to investigate whether caspase-12 modulates the inflammatory reaction induced by Yersinia. We found that caspase-12 did not modulate cytokine production induced by Yersinia spp.

Conclusions

Our experiments demonstrate for the first time the involvement of the NOD2/RIP2 pathway for recognition of Yersinia. However, caspase-12 does not modulate innate host defense against Y. pestis and alternative explanations for the geographical distribution of caspase-12 should be sought.

The genetic structure and history of Africans and African Americans

Africa is the source of all modern humans, but characterization of genetic variation and of relationships among populations across the continent has been enigmatic. We studied 121 African populations, four African American populations, and 60 non-African populations for patterns of variation at 1327 nuclear microsatellite and insertion/deletion markers. We identified 14 ancestral population clusters in Africa that correlate with self-described ethnicity and shared cultural and/or linguistic properties. We observed high levels of mixed ancestry in most populations, reflecting historical migration events across the continent. Our data also provide evidence for shared ancestry among geographically diverse hunter-gatherer populations (Khoesan speakers and Pygmies). The ancestry of African Americans is predominantly from Niger-Kordofanian (approximately 71%), European (approximately 13%), and other African (approximately 8%) populations, although admixture levels varied considerably among individuals. This study helps tease apart the complex evolutionary history of Africans and African Americans, aiding both anthropological and genetic epidemiologic studies.

Comparison of biological activity of human anti-apical membrane antigen-1 antibodies induced by natural infection and vaccination

Vaccines represent a significant potential means of decreasing global morbidity and mortality due to malaria. Clinical trials in the United States with Plasmodium falciparum Apical Membrane Antigen 1 (AMA1) showed that the vaccine induced biologically active Abs judged by an in vitro parasite growth inhibition assay (GIA). However, the same vaccine in Malian adults did not increase biological activity, although it elevated ELISA titers. Because GIA has been used to evaluate the biological activity of Abs induced by blood stage malarial vaccine candidates, we explored this discrepancy in this study. We affinity purified AMA1-specific Abs from both U.S. vaccinees and nonvaccinated individuals living in a malaria-endemic area of Mali and performed ELISA and GIA. Both AMA1-specifc Abs induced by vaccination (U.S.) and by natural infection (Mali) have comparable biological activity in GIA when the ELISA titer is normalized. However, a fraction of Malians' IgG that did not bind to AMA1 protein (Mali-non-AMA1 IgG) reduced the biological activity of the AMA1 Abs from U.S. vaccinees; in contrast, U.S.-non-AMA1 IgGs did not show a reduction of the biological activity. Further investigation revealed that the reduction was due to malaria-specific IgGs in the Mali-non-AMA1 IgGs. The fact that both U.S.- and Mali-AMA1-specific Abs showed comparable biological activity supports further development of AMA1-based vaccines. However, the reduction of biological activity of AMA1-specific Ab by other malaria-specific IgGs likely explains the limited effect on growth-inhibitory activity of Abs induced by AMA1 vaccination in Malian adults and may complicate efforts to develop a blood stage malaria vaccine.