Safety and Immunogenicity of a Heterologous Prime-Boost Ebola Virus Vaccine Regimen in Healthy Adults in the United Kingdom and Senegal.

BACKGROUND: The 2014 West African outbreak of Ebola virus disease highlighted the urgent need to develop an effective Ebola vaccine. METHODS: We undertook 2 phase 1 studies assessing safety and immunogenicity of the viral vector modified vaccinia Ankara virus vectored Ebola Zaire vaccine (MVA-EBO-Z), manufactured rapidly on a new duck cell line either alone or in a heterologous prime-boost regimen with recombinant chimpanzee adenovirus type 3 vectored Ebola Zaire vaccine (ChAd3-EBO-Z) followed by MVA-EBO-Z. Adult volunteers in the United Kingdom (n = 38) and Senegal (n = 40) were vaccinated and an accelerated 1-week prime-boost regimen was assessed in Senegal. Safety was assessed by active and passive collection of local and systemic adverse events. RESULTS: The standard and accelerated heterologous prime-boost regimens were well-tolerated and elicited potent cellular and humoral immunogenicity in the United Kingdom and Senegal, but vaccine-induced antibody responses were significantly lower in Senegal. Cellular immune responses measured by flow cytometry were significantly greater in African vaccinees receiving ChAd3 and MVA vaccines in the same rather than the contralateral limb. CONCLUSIONS: MVA biomanufactured on an immortalized duck cell line shows potential for very large-scale manufacturing with lower cost of goods. This first trial of MVA-EBO-Z in humans encourages further testing in phase 2 studies, with the 1-week prime-boost interval regimen appearing to be particularly suitable for outbreak control. CLINICAL TRIALS REGISTRATION: NCT02451891; NCT02485912.

Genetic Evidence for Erythrocyte Receptor Glycophorin B Expression Levels Defining a Dominant Plasmodium falciparum Invasion Pathway into Human Erythrocytes.

Plasmodium falciparum, the parasite that causes the deadliest form of malaria, has evolved multiple proteins known as invasion ligands that bind to specific erythrocyte receptors to facilitate invasion of human erythrocytes. The EBA-175/glycophorin A (GPA) and Rh5/basigin ligand-receptor interactions, referred to as invasion pathways, have been the subject of intense study. In this study, we focused on the less-characterized sialic acid-containing receptors glycophorin B (GPB) and glycophorin C (GPC). Through bioinformatic analysis, we identified extensive variation in glycophorin B (GYPB) transcript levels in individuals from Benin, suggesting selection from malaria pressure. To elucidate the importance of the GPB and GPC receptors relative to the well-described EBA-175/GPA invasion pathway, we used an ex vivo erythrocyte culture system to decrease expression of GPA, GPB, or GPC via lentiviral short hairpin RNA transduction of erythroid progenitor cells, with global surface proteomic profiling. We assessed the efficiency of parasite invasion into knockdown cells using a panel of wild-type P. falciparum laboratory strains and invasion ligand knockout lines, as well as P. falciparum Senegalese clinical isolates and a short-term-culture-adapted strain. For this, we optimized an invasion assay suitable for use with small numbers of erythrocytes. We found that all laboratory strains and the majority of field strains tested were dependent on GPB expression level for invasion. The collective data suggest that the GPA and GPB receptors are of greater importance than the GPC receptor, supporting a hierarchy of erythrocyte receptor usage in P. falciparum.

Determinants of complete immunization among senegalese children aged 12-23 months: evidence from the demographic and health survey.

BACKGROUND: The expanded Programme on Immunization (EPI) is one of the most cost-effective interventions to reduce childhood mortality and morbidity. However, determinants of childhood immunization have not been well studied in Senegal. Thus, the aim of our study is to assess routine immunization uptake and factors associated with full immunization status among Senegalese children aged 12-23 months. METHODS: We used the 2010-2011 Senegalese Demographic and Health Survey data. The DHS was a two stages cross-sectional survey carried out in 2010-2011. The analysis included 2199 children aged 12-23 months. The interviewers collected information on vaccine uptake based on information from vaccination cards or maternal recall Univariate and multivariable logistic regressions models were used to identify the determinants of full childhood immunization. RESULTS: The prevalence of complete immunization coverage among boys and girls based on both vaccination card information and mothers' recall was 62.8%. The immunization coverage as documented on vaccination cards was 37.5%. Specific coverage for the single dose of BCG at birth, the third dose of polio vaccine, the third dose of pentavalent vaccine and the first dose of measles vaccine were 94.7%, 72.7%, 82.6%, and 82.1%, respectively. We found that mothers who could show a vaccination card [AOR 7.27 95% CI (5.50-9.60)], attended at least secondary education level [AOR 1.8 95% CI (1.20-2.48)], attended four antenatal visits [AOR 3.10 95% CI (1.69-5.63)], or delivered at a health facility [AOR 1.27 95% CI (1-1.74)] were the predictors of full childhood immunization. Additionally, children living in the eastern administrative regions of the country were less likely to be fully vaccinated [AOR 0.62 95% CI (0.39-0.97)]. CONCLUSIONS: We found that the full immunization coverage among children aged between 12 and 23 months was below the national (> 80%) and international targets (90%). Geographic area, mother's characteristics, antenatal care and access to health care services were associated with full immunization. These findings highlight the need for innovative strategies based on a holistic approach to overcome the barriers to childhood immunization in Senegal.

Pattern of chronic myeloid leukemia in the imatinib era in a Sub-Saharan African setting.

Chronic myeloid leukemia (CML) is an orphan disease in Africa because of the inaccessibility to specific treatment and the high cost of diagnosis and monitoring patients. The aim of this study was to report CML treatment response in a developing country in the tyrosine kinase inhibitor era. We conducted a longitudinal study of our cohort of CML patients. Socio-demographic, diagnosis, therapeutic, and treatment response parameters were studied. Sokal score, disease phase at diagnosis, delay from diagnosis to treatment, and treatment response were analyzed for their impact on survival. Fifty-five patients with a diagnosis of CML and who received treatment with imatinib for a minimum of 3 months were included in this study. Median follow-up was 170 patient-years. The sex ratio (M/F) was 1.62 and median age at diagnosis was 42 years. At diagnosis, 85.5 % of the patients were in chronic phase (CP), 12.7 % in accelerated phase (AP), and 1.8 % in blast crisis (BC). Sokal risk score distribution was as follows: low risk 29.8 %, intermediate risk 38.3 %, and high risk 31.9 %. Median time from first symptoms to first medical visit was 6.2 months and median time from first medical visit to cytogenetic and or molecular confirmation was 12.4 months. Mean delay time from first medical visit to imatinib initiation was 12.5 months (95 % CI 6.3-18.7). The complete hematologic response (CHR) at 3 months, the major cytogenetic response (MCR) at 12 months, and the major molecular response (MMR) at 24 months were respectively 82.4, 75, and 25 %. The 2-year overall survival rate was 81 %. Advanced phase at the diagnosis, discontinuation of imatinib therapy over 15 % of the time, lack of CHR at 3 months, lack of MCR at 12 months, and progression of the disease during imatinib therapy were associated with a risk of death (p ≤ 0.05). Our data confirm the improved prognosis of CML treated with imatinib in the setting of a developing country. However, response rates are lower than in developed countries, and additional efforts should be made to facilitate early diagnosis and improve access to TKI, treatment compliance, and regular molecular monitoring of patients.

Immune characterization of Plasmodium falciparum parasites with a shared genetic signature in a region of decreasing transmission.

As the intensity of malaria transmission has declined, Plasmodium falciparum parasite populations have displayed decreased clonal diversity resulting from the emergence of many parasites with common genetic signatures (CGS). We have monitored such CGS parasite clusters from 2006 to 2013 in Thiès, Senegal, using the molecular barcode. The first, and one of the largest observed clusters of CGS parasites, was present in 24% of clinical isolates in 2008, declined to 3.4% of clinical isolates in 2009, and then disappeared. To begin to explore the relationship between the immune responses of the population and the emergence and decline of specific parasite genotypes, we have determined whether antibodies to CGS parasites correlate with their prevalence. We measured (i) antibodies capable of inhibiting parasite growth in culture and (ii) antibodies recognizing the surfaces of infected erythrocytes (RBCs). IgG obtained from volunteers in 2009 showed increased reactivity to the surfaces of CGS-parasitized erythrocytes over IgG from 2008. Since P. falciparum EMP-1 (PfEMP-1) is a major variant surface antigen, we used var Ups quantitative reverse transcription-PCR (qRT-PCR) and sequencing with degenerate DBL1α domain primers to characterize the var genes expressed by CGS parasites after short-term in vitro culture. CGS parasites show upregulation of UpsA var genes and 2-cysteine-containing PfEMP-1 molecules and express the same dominant var transcript. Our work indicates that the CGS parasites in this cluster express similar var genes, more than would be expected by chance in the population, and that there is year-to-year variation in immune recognition of surface antigens on CGS parasite-infected erythrocytes. This study lays the groundwork for detailed investigations of the mechanisms driving the expansion or contraction of specific parasite clones in the population.

Inhibitory KIR/HLA incompatibility between sexual partners confers protection against HIV-1 transmission.

Killer immunoglobulin-like receptors (KIRs) regulate natural killer (NK) cells in a human leukocyte antigen (HLA)-dependent manner. KIR/HLA mismatched hematopoietic stem cell transplants induce alloreactive NK cells, which prevent leukemia relapse. Certain KIR/HLA combinations protect against HIV-1 infection, but the effect of KIR/HLA mismatches between sexual partners has never been investigated. In this study, we analyzed the effect of allogeneic KIR/HLA combinations on HIV-1 transmission in a West African population of HIV-1-discordant and concordant couples. HIV-1-discordant couples were characterized by recipient partners with homozygous KIR2DL2, and by a mismatched recipient partner KIR2DL1/HLA-C2 with index partner HLA-C1/C1 combination expected to allow licensed missing self NK cell killing of index partners' cells. HIV-1-concordant couples on the other hand were characterized by KIR2DL3 homozygous recipient partners with HLA-C1/C2 bearing index partners, resulting in a matched KIR/HLA combination expected to inhibit NK cell killing. In vitro cocultures of healthy donor-derived NK cells and HIV-1 patient-derived CD4(+) T cells confirmed the involvement of these allogeneic KIR/HLA combinations in NK cell-mediated CD4(+) T-cell killing. Our data suggest that KIR/HLA incompatibility between sexual partners confers protection against HIV-1 transmission and that this may be due to alloreactive NK cell killing of the HIV-1-infected partner's cells.

Changes in immunological profile as a function of urbanization and lifestyle.

Differences in lifestyle and break with natural environment appear to be associated with changes in the immune system resulting in various adverse health effects. Although genetics can have a major impact on the immune system and disease susceptibility, the contribution of environmental factors is thought to be substantial. Here, we investigated the immunological profile of healthy volunteers living in a rural and an urban area of a developing African country (Senegal), and in a European country (the Netherlands). Using flow cytometry, we investigated T helper type 1 (Th1), Th2, Th17, Th22 and regulatory T cells, as well as CD4(+) T-cell and B-cell activation markers, and subsets of memory T and B cells in the peripheral blood. Rural Senegalese had significantly higher frequencies of Th1, Th2 and Th22 cells, memory CD4(+) T and B cells, as well as activated CD4(+) T and B cells compared with urban Senegalese and urban Dutch people. Within the Senegalese population, rural paritcipants displayed significantly higher frequencies of Th2 and Th22 cells, as well as higher pro-inflammatory and T-cell activation and memory profiles compared with the urban population. The greater magnitude of immune activation and the enlarged memory pool, together with Th2 polarization, seen in rural participants from Africa, followed by urban Africans and Europeans suggest that environmental changes may define immunological footprints, which could have consequences for disease patterns in general and vaccine responses in particular.

Plasmodium falciparum merozoite surface antigen, PfRH5, elicits detectable levels of invasion-inhibiting antibodies in humans.

Plasmodium falciparum is an intracellular protozoan parasite that infects erythrocytes and hepatocytes. The blood stage of its life cycle causes substantial morbidity and mortality associated with millions of infections each year, motivating an intensive search for potential components of a multi-subunit vaccine. In this study, we present data showing that antibodies from natural infections can recognize a recombinant form of the relatively conserved merozoite surface antigen, PfRH5. Furthermore, we performed invasion inhibition assays on clinical isolates and laboratory strains of P. falciparum in the presence of affinity purified antibodies to RH5 and show that these antibodies can inhibit invasion in vitro.

T-helper 17 cells are associated with pathology in human schistosomiasis.

BACKGROUND: Schistosome infections are often clinically silent, but some individuals develop severe pathological reactions. In several disease processes, T-helper 17 (Th17) cells have been linked to tissue injuries, while regulatory T cells (Tregs) are thought to downmodulate inflammatory reactions. We assessed whether bladder pathology in human Schistosoma haematobium infection is related to the balance of Th17 cells and Tregs. We used a murine model of Schistosoma mansoni infection to further investigate whether the peripheral profiles reflected ongoing events in tissues. METHODS: We characterized T-helper cell subsets in the peripheral blood of children residing in a S. haematobium-endemic area and in the peripheral blood, spleen, and hepatic granulomas of S. mansoni-infected high-pathology CBA mice and low-pathology C57BL/6 mice. RESULTS: S. haematobium-infected children with bladder pathology had a significantly higher percentage of Th17 cells than those without pathology. Moreover, the Th17/Treg ratios were significantly higher in infected children with pathology, compared with infected children without pathology. Percentages of interleukin 17-producing cells were significantly higher in spleen and granulomas of CBA mice, compared with C57BL/6 mice. This difference was also reflected in the peripheral blood. CONCLUSIONS: This is the first study to indicate that Th17 cells may be involved in the pathogenesis of human schistosomiasis.

Antiphospholipid antibodies and systemic scleroderma.

OBJECTIVE: Antiphospholipid antibodies (APLs) could be associated with an increased risk of vascular pathologies in systemic scleroderma. The aim of our study was to search for APLs in patients affected by systemic scleroderma and to evaluate their involvement in the clinical manifestations of this disease. MATERIALS AND METHODS: We conducted a cross-sectional descriptive study, from January 2009 until August 2010, with patients received at the Department of Dermatology (Dakar, Senegal). Blood samples were taken at the hematology laboratory and were analyzed for the presence of APLs. RESULTS: Forty patients were recruited. Various types of either isolated or associated APLs were found in 23 patients, i.e. 57.5% of the study population. The most frequently encountered antibody was IgG anti-ß2 GPI (37.5% of the patients), followed by anticardiolipins (17.5%) and lupus anticoagulants (5%). No statistically significant association of positive antiphospholipid-related tests to any of the scleroderma complications could be demonstrated. CONCLUSION: A high proportion of patients showing association of systemic scleroderma and APLs suggests the presence of a morbid correlation between these 2 pathologies. It would be useful to follow a cohort of patients affected by systemic scleroderma in order to monitor vascular complications following confirmation of the presence of antiphospholipid syndrome. CONFLICT OF INTEREST: None declared.

Red blood cell alloantibodies in paediatric transfusion in sub-Saharan Africa: A new cohort and literature review.

Blood transfusion support predisposes transfused children to the risk of erythrocyte alloimmunization in Sub-Saharan Africa. A cohort of 100 children receiving one to five blood transfusions were recruited for screening and identification of irregular antibodies using gel filtration technique. The mean age was 8 years and the sex-ratio at 1.2. The retrieved pathologies were: major sickle cell anaemia (46%), severe malaria (20%), haemolytic anaemia (4%), severe acute malnutrition (6%), acute gastroenteritis (5%), chronic infectious syndrome (12%) and congenital heart disease (7%). The children presented with haemoglobin levels ≤6 g/dl, and 16% of them presented positive irregular antibodies directed against the Rhesus (30.76%) and Kell (69.24%) blood group systems. A literature review shows that irregular antibody screenings vary from 17% to 30% of transfused paediatric patients in Sub-Saharan Africa. These alloantibodies are in particular directed against the Rhesus, Kell, Duffy, Kidd and MNS blood group and generally found in sickle cell disease and malaria. This study highlights the urgent need of extended red blood cell phenotyping including typing for C/c, E/e, K/k, and Fya/Fyb, and if possible Jka/Jkb, M/N, and S/s for children before transfusion in Sub-Saharan Africa.

Pre-Pandemic Cross-Reactive Immunity against SARS-CoV-2 among Central and West African Populations.

For more than two years after the emergence of COVID-19 (Coronavirus Disease-2019), significant regional differences in morbidity persist. These differences clearly show lower incidence rates in several regions of the African and Asian continents. The work reported here aimed to test the hypothesis of a pre-pandemic natural immunity acquired by some human populations in central and western Africa, which would, therefore, pose the hypothesis of an original antigenic sin with a virus antigenically close to the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). To identify such pre-existing immunity, sera samples collected before the emergence of COVID-19 were tested to detect the presence of IgG reacting antibodies against SARS-CoV-2 proteins of major significance. Sera samples from French blood donors collected before the pandemic served as a control. The results showed a statistically significant difference of antibodies prevalence between the collected samples in Africa and the control samples collected in France. Given the novelty of our results, our next step consists in highlighting neutralizing antibodies to evaluate their potential for pre-pandemic protective acquired immunity against SARS-CoV-2. In conclusion, our results suggest that, in the investigated African sub-regions, the tested populations could have been potentially and partially pre-exposed, before the COVID-19 pandemic, to the antigens of a yet non-identified Coronaviruses.

Sickle-cell disease and malaria: evaluation of seasonal intermittent preventive treatment with sulfadoxine-pyrimethamine in Senegalese patients-a randomized placebo-controlled trial.

Sickle-cell disease (SCD) patients are at high risk of developing malaria which is a major contributor to morbidity and mortality in this disease. In Senegal, malaria transmission is high during rainy season, between July and October, and it was noted that sickle-cell crisis are frequent during this period. Then we carried out a double-blind randomized controlled trial to compare the impact of monthly sulfadoxine-pyrimethamine (SP) during the high-transmission season versus placebo on malaria incidence and morbidity of sickle-cell anemia. Sixty (60) SCD patients were randomized either to receive three intermittent preventive treatment (ITP) with SP or placebo using the random permutation table with nine elements. The drug was administrated as follows: sulfadoxine 25 mg/kg and pyrimethamine 1.25 mg/kg and this treatment was given once during the following months: September, October, and November. Overall four episodes of malaria disease were diagnosed, all these cases in the placebo arm. Thus, overall prevalence was 6.6% and there was no other case of malaria in the SP arm during the study period. Parasitological diagnosis confirmed the presence of Plasmodium falciparum in all four cases. No patient death was encountered during the study. SP treatment was well tolerated as only one patient (1.6%) in the SP arm reported pruritus. A significant reduction of patients' complaints (p = 002) and blood requirements (p = 0.001) was noted in the SP group; whereas, no impact was observed on vaso-occlusive crisis and hospitalization occurrence. Malaria prophylaxis by monthly intake of SP during the transmission period of the parasite reduced the prevalence of malaria and was safe in SCD patients leaving in malaria endemic area.

Low-level CD4+ T cell activation in HIV-exposed seronegative subjects: influence of gender and condom use.

Immune activation has been suggested to increase susceptibility to human immunodeficiency virus type 1 (HIV-1) transmission, while at the same time it could be deemed essential for mounting an effective antiviral immune response. In this study, we compared levels of T cell activation between exposed seronegative (ESN) partners in HIV-1 discordant couples and HIV-unexposed control subjects in Dakar, Senegal. ESN subjects showed lower levels of CD38 expression on CD4(+) T cells than did control subjects. However, this was found to be associated with concurrent differences in the use of condoms: ESN subjects reported a higher degree of condom use than did control subjects, which correlated inversely with CD38 expression. In addition, we observed markedly higher levels of T cell activation in women compared with men, irrespective of sexual behavior. These findings question the relevance of low-level CD4(+) T cell activation in resistance to HIV-1 infection and underscore the need to take gender and sexual behavior characteristics of high-risk populations into account when analyzing correlates of protective immunity.

A flow cytometry-based assay for measuring invasion of red blood cells by Plasmodium falciparum.

Variability in the ability of the malaria parasite Plasmodium falciparum to invade human erythrocytes is postulated to be an important determinant of disease severity. Both the parasite multiplication rate and erythrocyte selectivity are important parameters that underlie such variable invasion. We have established a flow cytometry-based method for simultaneously calculating both the parasitemia and the number of multiply-infected erythrocytes. Staining with the DNA-specific dye SYBR Green I allows quantitation of parasite invasion at the ring stage of parasite development. We discuss in vitro and in vivo applications and limitations of this method in relation to the study of parasite invasion.

Reduced Ebola vaccine responses in CMV+ young adults is associated with expansion of CD57+KLRG1+ T cells.

CMV is associated with immunosenescence and reduced vaccine responses in the elderly (>70 yr). However, the impact of CMV in young adults is less clear. In this study, healthy UK and Senegalese adults aged 18-50 yr (average, 29 yr) were vaccinated with the Ebola vaccine candidate chimpanzee adenovirus type 3-vectored Ebola Zaire vaccine (ChAd3-EBO-Z) and boosted with modified vaccinia Ankara Ebola Zaire-vectored (MVA-EBO-Z) vaccine. CMV carriage was associated with an expansion of phenotypically senescent CD4+ and CD8+ T cells expressing CD57 and killer cell lectin-like receptor G1 (KLRG1), which was negatively associated with vaccine responses in both cohorts. Ebola-specific T cell responses induced by vaccination also contained significantly increased frequencies of terminally differentiated CD57+KLRG1+ cells in CMV seropositive (CMV+) individuals. This study suggests that CMV can also affect vaccine responses in younger adults and may have a particularly marked impact in many developing countries where CMV seroprevalence is almost universal.