Alexander B. Odaibo

The Human Immune Response to Plasmodium falciparum Includes Both Antibodies That Inhibit Merozoite Surface Protein 1 Secondary Processing and Blocking Antibodies

ABSTRACT Malaria merozoite surface protein 1 (MSP1) is cleaved in an essential step during erythrocyte invasion. The responses of children to natural malaria infection included antibodies that inhibit this cleavage and others that block the binding of these inhibitory antibodies. There was no correlation between the titer of the antibody to the 19-kDa fragment of MSP1 and its inhibitory activity. These findings have implications for the design of MSP1-based vaccines.

Laboratory assessment of molluscicidal activity of crude aqueous and ethanolic extracts of Dalbergia sissoo plant parts against Biomphalaria pfeifferi.

BACKGROUND In the continued search for molluscicidal compounds from plants, crude aqueous and ethanolic extracts from different parts of Dalbergia sissoo Roxb. 1832, were evaluated against egg masses and adults of Biomphalaria pfeifferi (Krauss, 1848), the snail intermediate host of Schistosoma mansoni (Sambon, 1907) in Nigeria. METHODS Laboratory-bred adult B. pfeifferi and their viable 0-24 h old egg masses were separately exposed to five different concentrations (7.81-2000 mg l(-1)) each, of the crude aqueous and ethanolic extracts of the fruits, leaves, roots and stem bark of D. sissoo, for 24 h. The LC50 and LC90 values of each extract for the target organisms were calculated using probit analysis. RESULTS Only the ethanolic extracts of the fruits and roots showed significant activities against the adult snails (24 h LC90<100 mg l(-1): 74.33 and 93.93 mg l(-1), respectively) and their egg masses (LC90: 89.29 and 114.29 mg l(-1), respectively) while all other extracts demonstrated weak molluscicidal and ovicidal activities (24 h LC90 > 100 mg l(-1)). There were concentration-dependent behavioural changes in snails exposed to test extracts, while egg mortalities, manifested at the gastrula/exogastrula stage and or the prehatch snail stage of development, were similarly concentration-dependent. CONCLUSIONS The crude ethanolic extracts of D. sissoo fruits and roots exhibited promising molluscicidal activities (LC90 values<100 mg l(-1)) against adult B. pfeifferi with additional toxicities towards its 0-24 h-old egg masses.

Schistosomiasis among pregnant women in rural communities in Nigeria

To assess the epidemiology of urogenital schistosomiasis among pregnant women in rural communities of southwestern Nigeria.

Urogenital schistosomiasis and urological assessment of hematuria in preschool-aged children in rural communities of Nigeria

OBJECTIVE The study evaluates the prevalence of urogenital schistosomiasis and diagnostic performance of chemical reagent strips used for disease diagnosis in preschool-aged children (≤ 5 years) in Nigeria rural communities. PATIENTS AND METHODS Urine samples from 419 children were observed microscopically for Schistosoma haematobium and screened for hematuria using standard urine chemical reagent strips. RESULTS Prevalence and intensity of infection were 9.8% and 14.4 eggs/10 ml of urine, respectively. Prevalence of infection was similar in girls (10%) and boys (9.6%) (p > 0.05). The intensity of infection was higher in boys (17.1 eggs/10 ml of urine) than in girls (12.8 eggs/10 ml of urine); however, this was not gender dependent (p > 0.05). The occurrence of hematuria was not associated with gender (p > 0.05), but was associated with prevalence of infection (p < 0.05). CONCLUSION Infection with S. haematobium occurs early in life in the communities and although intensity of infection is low, it could have serious implications in disease transmission. Hematuria, although moderately sensitive to infection, is an important morbidity indicator of urogenital schistosomiasis in the study population.

A cross-sectional study on urogenital schistosomiasis in children; haematuria and proteinuria as diagnostic indicators in an endemic rural area of Nigeria

BACKGROUND Rapid and accurate diagnosis is necessary for the management of schistosomiasis in endemic areas. OBJECTIVE To assess the burden of urogenital schistosomiasis and the diagnostic efficiency of morbidity indicators of the disease in an endemic rural community of Nigeria. METHODS A cross-sectional school-based study was conducted. Urine samples of 487 pupils were screened microscopically for S. haematobium and tested for haematuria and proteinuria using chemical reagent strips. RESULTS The prevalence and intensity of infection were 57.1% and 45.0 eggs/10 mL urine respectively. Prevalence of infection in male (54.1%) and female (60.3%) individuals showed no significant variation (P>0.05). However, prevalence of infection was age dependent with those in age groups 3-5 and 12-14 years having the least and highest prevalence of infection respectively (P<0.05). Microhaematuria and proteinuria varied significantly with ages of the pupils with least (14.0, 40.0%) and highest (60.0, 80.0%) prevalence recorded in age groups 3-5 and 15-19 years respectively (P<0.05). Proteinuria showed higher sensitivity (80.3%) compared to microhaematuria (73.3%). CONCLUSION Schistosomiasis is highly endemic in the study area and the use of microhaematuria and proteinuria for mapping the infected population prior treatment could be adopted.

Antibody specificities of children living in a malaria endemic area to inhibitory and blocking epitopes on MSP-119 of Plasmodium falciparum

Merozoite surface protein-1(19) (MSP-1(19)) specific antibodies which include processing inhibitory, blocking and neutral antibodies have been identified in individuals exposed to Plasmodium falciparum. Here we intend to look at the effect of single and multiple amino acid substitutions of MSP-1(19) on the recognition by polyclonal antibodies from children living in Igbo-Ora, Nigeria. This would provide us with information on the possibility of eliciting mainly processing inhibitory antibodies with a recombinant MSP-1(19) vaccine. Blood was collected from children in the rainy season and binding of anti-MSP-1(19) antibodies to modified mutants of MSP-1(19) was analysed by ELISA. The MSP-1(19) mutant proteins with single substitutions at positions 22 (Leu-->Arg), 43 (Glu-->Leu) and 53 (Asn-->Arg) and the MSP-1(19) mutant protein with multiple substitutions at positions 27+31+34+43 (Glu-->Tyr, Leu-->Arg, Tyr-->Ser, Glu-->Leu); which had inhibitory epitopes; had the highest recognition. Children recognised both sets of mutants with different age groups having different recognition levels. The percentage of malaria positive individuals (32-80%) with antibodies that bound to the mutants MSP-1(19) containing epitopes that recognise only processing inhibitory and not blocking antibodies, were significantly different from those with antibodies that did not bind to these mutants (21-28%). The amino acid substitutions that abolished the binding of blocking antibodies without affecting the binding of inhibitory antibodies are of particular interest in the design of MSP-1(19) based malaria vaccines. Although these MSP-1(19) mutants have not been found in natural population, their recognition by polyclonal antibodies from humans naturally infected with malaria is very promising for the future use of MSP-1(19) mutants in the design of a malaria vaccine.

Fine specificity of anti-MSP119 antibodies and multiplicity of Plasmodium falciparum Merozoite Surface Protein 1 types in individuals in Nigeria with sub-microscopic infection

BackgroundThe 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.MethodsPlasma 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.ResultsPlasma 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).ConclusionsIn 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.

Maternal schistosomiasis: a growing concern in sub-Saharan Africa

Abstract Schistosomiasis remains one of the most important tropical parasitic infections threatening millions of lives in endemic areas. Cases of infections due to Schistosoma spp, the diecious digenetic trematodes have been on the increase over the last decades. While considerable efforts have been made to reduce infections and morbidities in most endemic areas, these efforts seem to be tailored only towards a specific group (school-based resources). This bias towards school children in epidemiological studies has also been observed in various research efforts in sub-Saharan Africa, thus making it difficult to produce a reliable estimate of the extent of infection in other strata of the population at risk. In recent times, attention has been drawn to Schistosoma spp infections in infants and preschool children, while studies on epidemiology of maternal schistosomiasis still suffer neglect. Considering the potential morbidity of Schistosoma infections on the mothers, fetuses, and neonates, as evidenced in some animal models and human case studies, more attention is solicited in all areas of observational studies and clinical trials, for maternal schistosomiasis with the aim of providing relevant data and information for effective management of the disease during pregnancy.

Poliovirus and other enteroviruses in children infected with intestinal parasites in Nigeria.

INTRODUCTION Poliovirus, an enterovirus, still persists in Nigeria despite the global efforts tailored towards its eradication. This study aimed to assess the impacts of poliovirus and other enteroviruses on the susceptibility of individuals to intestinal parasite infections. METHODOLOGY A cross-sectional study on the prevalence of intestinal parasites was conducted on two-sample stool specimens of 717 Nigerian children (between 1 and 19 years of age) whose poliovirus/other enteroviruses infection status had been determined. RESULTS The overall prevalence of Sabin poliovirus and other related enteroviruses infections were 6.6% and 13.8%, respectively. The prevalence of Ascaris lumbricoides was significantly higher than that of other intestinal parasites (p < 0.05), with children in the 0-4 year age group being the most predisposed age group to intestinal parasitic infection (OR = 11.7, CI = 9.2-15.0). While the prevalence of all species of parasites except S. mansoni showed no significant variations in children with Sabin poliovirus (p > 0.05), the prevalence of hookworms and Taenia spp. was significantly higher in children with other enteroviral infections (p < 0.05). CONCLUSIONS The high risk of children of acquiring enteroviral infection through some intestinal parasites is an indication of possible association of the parasites in a more poliovirus-endemic population. A combined intervention approach for the two infections is advocated.

Maternal urogenital schistosomiasis; monitoring disease morbidity by simple reagent strips

Background Urine analysis is one of the recommended antenatal guidelines for early diagnosis of pregnancy-associated complications. While in practice, urine analysis by dipstick had been used to provide useful information on other urinary tract infections, its applications for early detection of urogenital schistosomiasis in pregnant women is often times not given due attention in most endemic areas. Our study therefore assessed the performance of some common urinalysis parameters in the diagnosis of maternal urogenital schistosomiasis in endemic rural communities of Nigeria. Methodology/Principal findings The cross-sectional epidemiologic survey of urogenital schistosomiasis was conducted among pregnant women in Yewa North Local Government, Ogun State, Nigeria. The women were microscopically examined for infection with Schistosoma haematobium, visually observed for macrohematuria, and screened for microhematuria and proteinuria using standard urine chemical reagent strips. Of 261 volunteered participants, 19.9% tested positive for S. haematobium infection. The proportion of microhematuria (23.8%) was significantly higher than that of macrohematuria (3.8%) and proteinuria (16.8%) (P<0.05). Microhematuria with sensitivity (82.7%) and specificity (89.0%) was the best diagnostic indicator of urogenital schistosomiasis. Macrohematuria with the least sensitivity (11.8%) was however the most specific (98.1%) for diagnosing urogenital schistosomiasis in pregnant women. Maximum microhematuria sensitivity (100.0%) was observed in women between 15–19 years but sensitivity was consistently low in older age groups. Maximum sensitivity, specificity and predictive values (100.0%) were recorded for microhematuria in first trimester women. Diagnostic efficiency of proteinuria and macrohematuria was also better in the first trimester women except the 25.0% specificity recorded for proteinuria. The overall diagnostic performance of microhematuria and proteinuria was better in secundigravidae. Conclusions/Significance Microhematuria can be used for early detection of urogenital schistosomiasis in endemic areas especially in younger women. However because microhematuria is a condition that occurs during pregnancy and in several other diseases, it is necessary to compliment the diagnosis with other diagnostic tools such as microscopy and serology. Treatment with praziquantel is recommended for the women in their late trimesters after follow up test in order to avert associated adverse pregnancy outcomes.