Fine specificity of anti-MSP119 antibodies and multiplicity of Plasmodium falciparum merozoite surface protein 1 types in individuals in Nigeria with sub-microscopic infection.

BACKGROUND: The absence of antibodies specific for the 19 kDa C-terminal domain of merozoite surface protein 1 (MSP119) has been associated with high-density malaria parasitaemia in African populations. The hypothesis that a high prevalence and/or level of anti-MSP119 antibodies that may inhibit erythrocyte invasion would be present in apparently healthy individuals who harbour a sub-microscopic malaria infection was tested in this study. METHODS: Plasma samples were collected from residents in a region in Nigeria hyperendemic for malaria, who had no detectable parasitaemia by microscopy. Using a competition-based enzyme-linked-immunosorbent assay with two invasion-inhibitory monoclonal antibodies (mAbs) 12.10 and 12.8, the levels and prevalence of specific antibodies were measured. The minimum multiplicity of infection was determined using PCR. The prevalence of anaemia was also measured. RESULTS: Plasma samples from 85% of individuals contained antibodies that bound to MSP119. The inhibition of mAb 12.10 binding was strongly correlated with the prevalence (Spearman correlation test, p < 0.0001) and mean titre of anti-MSP119 antibodies (Spearman correlation test, p < 0.001) in the samples. Comparing samples from individuals with multiple infection (group M) and single infection (Group S), group M contained a higher (p = 0.04) prevalence of anti-MSP119 antibodies that competed with mAb 12.10. Using a logistic regression model, it was found that the presence of antibodies competitive with mAb 12.10 was affected negatively by anaemia (p = 0.0016) and positively by the carriage of multiple parasite genotypes (p = 0.04). CONCLUSIONS: In the search for correlates of protection against malaria, which will be essential to evaluate clinical trials of malaria vaccines based on MSP1, this study examines some potential assays and the factors that need to taken into account during their evaluation, using samples from individuals naturally exposed to malaria infection.

Shedding proportion of Toxoplasma gondii-like oocysts in feral cats and soil contamination in Oyo State, Nigeria.

Toxoplasmosis, a disease caused by the intracellular protozoan parasite Toxoplasma gondii, is transmitted through several hosts with cats serving as its definitive host. Oocysts are released with cat faeces into the environment (e.g. soil); an important medium in its transmission. The level of soil contamination with oocysts is an indicator of the level of on- going transmission. However, a dearth of information exists on the relationship between the presence of oocysts shedding cats and soil, and its importance in the transmission of T. gondii in Nigeria. In this study, the shedding proportion of T. gondii-like oocysts in cats and soil contamination levels were investigated in three communities in Ibadan, Nigeria. Soil (n = 204) and feral cat faecal samples (n = 14) were examined for the presence of oocysts using a modified sucrose flotation technique. Cat sera (n = 15) were also analysed for IgG antibodies to T. gondii by ELISA. T. gondii-like oocysts were identified in 21.4% (95% CI: 4.6-50.8) of the total cat faecal samples. The prevalence was 50% (95% CI: 6.7-93.3), 0% and 10% (95% CI: 0.3-44.5) in Akinyele, Laniba and Ajibode communities respectively. T. gondii IgG antibody was present in 86.7% of the screened cat sera (including the copropositive cats). The seroprevalence in cats was 75% in Akinyele, 0% Laniba and 90.9% for Ajibode community (P >0.05). Oocysts were recovered from 1.5% (95% CI: 0.50-4.23) of the soil samples screened and were identified from 3.8% (95% CI: 0.13-10.58) of the soil collected in Akinyele community. Akinyele also recorded the highest number of infected cats. Oocysts were identified in soil from dumpsites 2.6% (95% CI: 0.4-13.2) and residential areas 1.9% (95% CI: 0.5-6.8). Soil contaminated with T. gondii-like oocysts and cats shedding oocysts were found in areas with high human activities within the communities. The presence of T. gondii-like oocysts in the soil and the presence of cats that tested positive to antibodies specific to T. gondii MIC 3 Protein suggested the possibility of T. gondii transmission in these communities and places emphasis on its public health importance in a susceptible population.

Cellular responses to modified Plasmodium falciparum MSP119 antigens in individuals previously exposed to natural malaria infection.

BACKGROUND: MSP1 processing-inhibitory antibodies bind to epitopes on the 19 kDa C-terminal region of the Plasmodium falciparum merozoite surface protein 1 (MSP1(19)), inhibiting erythrocyte invasion. Blocking antibodies also bind to this antigen but prevent inhibitory antibodies binding, allowing invasion to proceed. Recombinant MSP1(19) had been modified previously to allow inhibitory but not blocking antibodies to continue to bind. Immunization with these modified proteins, therefore, has the potential to induce more effective protective antibodies. However, it was unclear whether the modification of MSP1(19) would affect critical T-cell responses to epitopes in this antigen. METHODS: The cellular responses to wild-type MSP1(19) and a panel of modified MSP1(19) antigens were measured using an in-vitro assay for two groups of individuals: the first were malaria-naïve and the second had been naturally exposed to Plasmodium falciparum infection. The cellular responses to the modified proteins were examined using cells from malaria-exposed infants and adults. RESULTS: Interestingly, stimulation indices (SI) for responses induced by some of the modified proteins were at least two-fold higher than those elicited by the wild-type MSP1(19). A protein with four amino acid substitutions (Glu27-->Tyr, Leu31-->Arg, Tyr34-->Ser and Glu43-->Leu) had the highest stimulation index (SI up to 360) and induced large responses in 64% of the samples that had significant cellular responses to the modified proteins. CONCLUSION: This study suggests that specific MSP1(19) variants that have been engineered to improve their antigenicity for inhibitory antibodies, retain T-cell epitopes and the ability to induce cellular responses. These proteins are candidates for the development of MSP1-based malaria vaccines.

Arsenicosis in bladder pathology and schistosomiasis in Eggua, Nigeria.

Background: Chronic schistosomiasis and arsenic exposure through drinking water are some of the risk factors for bladder cancer. To determine the association of schistosomiasis and arsenicosis with bladder pathologies, 122 individuals from Eggua in southwest Nigeria were recruited for this study. Methods: Prevalence of schistosomiasis was determined by urine microscopy and PCR. Total urinary arsenic concentration and arsenic levels in three different water sources in the community were assessed by flame atomic absorption spectrometry. Bladder pathologies were investigated by ultrasonography. The data collected were evaluated with chi-square (χ2) and ANOVA tests to examine the relationships among demographic factors, infection, bladder pathologies and urinary arsenic concentrations. Results: The prevalence and mean intensity of schistosomiasis were 21.3% and 20.7 eggs/10 mL urine, respectively. Arsenic concentration in two of the water sources, River Yewa (0.46 mg/L) and borehole (0.52 mg/L), were above the WHO standard (0.01 mg/L); and the mean concentration in urine samples, 1.17 mg/L, was also above the WHO standard (0.2 mg/L). There was no evidence of an association between bladder pathology and arsenicosis, or between schistosomiasis associated-bladder pathology and arsenicosis (p=0.66). Conclusions: Arsenicosis is a public health concern in the study population. At the moment no clear roles are envisaged for it in the development of bladder pathologies or urinary schistosomiasis-associated bladder pathologies in Eggua.

Metabolite profiling for biomarkers in Schistosoma haematobium infection and associated bladder pathologies.

BACKGROUND: Metabolic fingerprinting analysis can offer insights into underlying reactions in a biological system; hence it is crucial to the understanding of disease pathogenesis and could provide useful tools for discovering biomarkers. We sought to examine the urine and plasma metabolome in individuals affected by urogenital schistosomiasis and its associated-bladder pathologies. METHODOLOGY: Blood and midstream urine were obtained from volunteers who matched our inclusion criteria among residents from Eggua, southwestern Nigeria. Samples were screened by urinalysis, microscopy, PCR and ultrasonography, and categorised as advanced (urogenital schistosomiasis associated-bladder pathologies), infection-only (urogenital schistosomiasis alone) and controls (no infection and no pathology). Metabolites were extracted and data acquired with ultra high-performance liquid chromatography coupled with Thermo Q-Exactive orbitrap HRMS. Data was analysed with MetaboAnalyst, Workflow4Metabolomics, HMDB, LipidMaps and other bioinformatics tools, with univariate and multivariate statistics for metabolite selection. PRINCIPAL FINDINGS: There were low levels of host sex steroids, and high levels of several benzenoids, catechols and lipids (including ganglioside, phosphatidylcholine and phosphatidylethanolamine), in infection-only and advanced cases (FDR<0.05, VIP>2, delta>2.0). Metabolites involved in biochemical pathways related to chorismate production were abundant in controls, while those related to choline and sphingolipid metabolism were upregulated in advanced cases (FDR<0.05). Some of these human host and Schistosoma haematobium molecules, including catechol estrogens, were good markers to distinguish infection-only and advanced cases. CONCLUSIONS: Altered glycerophospholipid and sphingolipid metabolism could be key factors promoting the development of bladder pathologies and tumours during urogenital schistosomiasis.

Comparison of PCR-based detection of Plasmodium falciparum infections based on single and multicopy genes.

PCR-based assays are the most sensitive and specific methods to detect malaria parasites. This study compared the diagnostic accuracy of three PCR-based assays that do not only differ in their sequence target, but also in the number of copies of their target region, for the detection of Plasmodium falciparum in 401 individuals living in a malaria-endemic area in Nigeria. Compared to a composite reference generated from results of all the 3 PCR assays, the stevor gene amplification had a sensitivity of 100% (Kappa = 1; 95% CI = 1.000-1.000), 83% (Kappa = 0.718; 95% CI = 0.648-0.788) by SSUrRNA gene PCR and 71% (Kappa = 0.552; 95% CI = 0.478-0.627) by the msa-2 gene amplification. Results from this study indicate that the stevor gene amplification is the most sensitive technique for the detection of P. falciparum. This assay may be an important reference standard, especially when a confirmatory technique with high sensitivity and specificity is needed for ruling out P. falciparum infection.