Total immunoglobulin G and IgG1 subclass levels specific for the MSP-1(19) of Plasmodium falciparum are different in individuals with either processing-inhibitory, blocking or neutral antibodies.

BACKGROUND: Some MSP-1(19) specific antibodies that inhibit merozoite invasion also inhibit the secondary processing of MSP-1. However the binding of these inhibitory antibodies can be blocked by another group of antibodies, called blocking antibodies, which recognize adjacent or overlapping epitopes, but themselves have no effect on either MSP-1 processing or merozoite invasion. These antibodies have been reported to be present in individuals living in a malaria endemic area. METHODS: Blood samples were obtained from children shown to have processing inhibitory, blocking, and neutral antibodies in a previous study. Enzyme linked immunosorbent assay (ELISA), was used to determine the total IgG, IgM and IgG subtypes. RESULTS: There was a significant difference in anti-MSP-1(19) IgG, while there was no significant difference in the anti-MSP-1(19) IgM. Only anti MSP-1(19) IgG1, amongst the IgG subtypes was significantly different between the groups. CONCLUSION: This study shows that antibodies against MSP-1 are different not only in specificity and function but also in the amount of total IgG and IgG subtype produced.

Total Immunoglobulin G and IgG1 Subclass Levels Specific for the MSP-1 19 of Plasmodium falciparum are Different in Individuals with either Processing-Inhibitory; Blocking or Neutral Antibodies

Background: Some MSP-1 19 specific antibodies that inhibit merozoite invasion also inhibit the secondary processing of MSP-1. However the binding of these inhibitory antibodies can be blocked by another group of antibodies; called blocking antibodies; which recognize adjacent or overlapping epitopes; but themselves have no effect on either MSP-1 processing or merozoite invasion. These antibodies have been reported to be present in individuals living in a malaria endemic area. Methods: Blood samples were obtained from children shown to have processing inhibitory; blocking; and neutral antibodies in a previous study. Enzyme linked immunosorbent assay (ELISA); was used to determine the total IgG; IgM and IgG subtypes.Results: There was a significant difference in anti-MSP-1 19 IgG; while there was no significant difference in the anti-MSP-1 19 IgM. Only anti MSP-1 19 IgG1; amongst the IgG subtypes was significantly different between the groups. Conclusion: This study shows that antibodies against MSP-1 are different not only in specificity and function but also in the amount of total IgG and IgG subtype produced

Antibody specificities of children living in a malaria endemic area to inhibitory and blocking epitopes on MSP-1 19 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.

Cytokine Profiles and Antibody Responses to Plasmodium Falciparum Malaria Infection in Individuals Living in Ibadan; Southwest Nigeria

Background: The ability of the host immune system to efficiently clear Plasmodium falciparum parasites during a malaria infection depends on the type of immune response mounted by the host. Study design: In a cross-sectional study; we investigated the cellular-and antibody responses in individuals with P. falciparum infection; in an attempt to identify immunological signs indicative of the development of natural immunity against malaria in Ibadan; Nigeria. Levels of IL-10; IL-12(p70); IFN-a; and IgM; IgG and IgG1-4 subclasses in the serum of 36 symptomatic children with microscopically confirmed malaria parasitaemia and 54 asymptomatic controls were analysed by ELISA. Results: IFN-a and IL-10 were significantly higher in the symptomatic children (p=0.009; p=0.025 respectively) than in the asymptomatic controls but no differences were seen for IL-12(p70). Estimated higher ratios of IFN-a/IL-10 and IFN-a/IL-12 were also observed in the symptomatic children while the asymptomatic controls had higher IL-12/IL-10 ratio. The mean concentration levels of anti-P. falciparum IgG1; IgG2; IgG3 antibodies were statistically significantly higher in the individuals 5 years of age than 5 years while anti-P. falciparum IgG3 antibodies were notably low in 5 years category. Children 5 years had higher IgM antibodies than IgG and the expression of IgG subclasses increased with age. Conclusion: Taken together; malaria infection is on a delicate balance of pro- and anti-inflammatory cytokines. The higher levels of IFN-a seen in the symptomatic children (6months) may be instrumental in immune-protection against malaria by limiting parasite replication. The observed variations in immunoglobulin subclass levels were age- dependent and exposure-related

Epidemiological Factors that Promote the Development of Severe Malaria Anaemia in Children in Ibadan

Background: Effective control and management of severe malaria cases depends on a clear understanding of the local epidemiological factors and specific clinical manifesta- tions of the disease in the different endemic regions. Objectives: To determine the prevalence of severe malaria and epidemiological factors that affect the development of malaria anaemia. Methods: A cross-sectional survey was carried out among children below 5 years of age; at the Adeoyo State Maternity Hospital;Ibadan; Nigeria. Question-naires and case histories were taken from patients clinically diagnosed of malaria.Thus; 372 volunteers wererecruited into the study from the 3131 paediatric cases that reported over the10-week period to the out-patient department (OPD) ofthe hospital. 229 (61.6) of the recruited volunteers presented with fever (37.5 oC) at consultation.These had malaria parasite andPCV tests done. Results: Clinical diagnosis was confirmed microscopically in 78(290/372) for Plasmodium infection using thick film slides. Anaemia (PCV 28) prevalence was 28.2. Factors that contributed to the rapid progression of uncomplicated malaria to severestatus included: age of the child; level of parasitaemia; careless response and attitude of parents or guardians to fever in the children;parents' preoccupation with their jobs or other healthy children and unwillingness to use available health facilities. Conclusion: The study underscores the need for community involved partnership for malaria control especially through healtheducation for the home manage- ment of malaria; espeically among those experiencing some form of inequity in access to healthcare

Variation in the relationship between anti-MSP-1(19) antibody response and age in children infected with Plasmodium falciparum during the dry and rainy seasons.

Malaria remains a major parasitic disease in Africa, with 300-500 million new infections each year. There is therefore an urgent need for the development of new effective measures, including vaccines. Plasmodium falciparum merozoite surface protein-1(19) (MSP-1(19)) is a prime candidate for a blood-stage malaria vaccine. Blood samples were collected from children aged 10 days to 15 years in the months of January-March (N = 351) and October-November (N = 369) corresponding to the dry and rainy seasons, respectively. P. falciparum infection was determined by microscopy and enzyme linked immunosorbent assay (ELISA) was used to determine the total IgG and IgG subclasses. There was a significant increase in the mean anti-MSP-1(19) antibody titre in the dry season (p < 0.05), compared to the rainy season. A significantly positive correlation between the anti-MSP-1(19) antibody titre and parasite density (p < 0.01, r = 0.138) was observed. In the rainy season, unlike in the dry season, P. falciparum positive children had higher anti-MSP-1(19) antibody titres than P. falciparum negative children and this difference was significant (p < 0.05). When all individuals were grouped together, the anti-MSP-1(19) antibody titre increased with age in both seasons (r = 0.186 and 0.002), this increase was more apparent in the dry season. However, when the study population was divided into P. falciparum positive and negative groups, it was observed that in the rainy season, there was a negative correlation between anti-MSP-1(19) titre and age in P. falciparum positive individuals, while those who were P. falciparum negative had a positive correlation between anti-MSP-1(19) titre and age. Analysis of anti-MSP-1(19) IgG subclass showed that IgG1 and IgG3 mean titres were highest in both the dry and rainy seasons with an increase in the mean antibody titres for IgG1, IgG2 and IgG3 in the rainy season. In the dry season there was a positive correlation between IgG1, IgG2, and IgG3 titres with age, while IgG4 was negative, whereas in the rainy season there was a positive correlation between IgG2 and IgG4 (non-cytophilic antibodies) with age and a negative correlation for IgG1 and IgG3 (cytophilic antibodies) with age. Seasonal differences in the level of MSP-1(19) IgG subclass titres were observed for P. falciparum negative and positive individuals. Only samples, which were positive for IgG2 and IgG4, showed positive correlation between parasitemia and total IgG. The incidence of P. falciparum infection, which increases during the rainy season, might be an important determinant of anti-MSP-1(19) antibody levels in children living in Igbo-Ora and the results point to the fact that non-cytophilic antibodies to MSP-1(19) in children might be associated with an increase in total IgG and parasitemia.

Clinical manifestations and immune response to MSP 1(19) in severe paediatric malaria in Adeoyo state maternity hospital, Ibadan.

A 10-week cross-sectional study was carried out at the Adeoyo State Maternity Hospital (Beere, Ibadan), Southwestern Nigeria in order to determine (a) the prevalence of severe malaria, (b) identify the predominant clinical presentations that characterise the disease in children below 5 years and the pattern of antibody responses to MSP 19 elicited in severe malaria complications. Three thousand, one hundred and thirty-one cases reported to the Out Patients' Department; of these, 372 (11.8%) subjects were recruited on the basis of doctors' diagnosis of severe malaria, malaria and other complications. Six per cent (188/3131) ofthe patients were admitted. Serum samples for 320 ofthe 372 subjects were analysed for antibodies specific to MSP 1(19) by ELISA. The highest antibody responses occurred in the age group 2-5 years. Parasite prevalence was 77.9% (290 of 372 subjects) and parasite density ranged from 80 to >100000 parasites/microL blood. Fever (an average temperature of 38.6 +/- 0.4 degrees C and peak at 41 degrees C) and severe malaria were the major clinical manifestations of malaria amongst the study population. Severe malaria was found to be associated with other features such as cough, vomiting and diarrhoea.

Evaluation of a rapid immunochromatographic card test for Plasmodium falciparum in Ibadan, Nigeria.

This short report describes the results of a rapid, simple and cost effective immunodiagnostic test for malaria in Ibadan, Nigeria. A total of 77% patients presenting at the children outpatient clinic, University College Hospital with malaria symptoms were screened for malaria parasites by microscopy using Giemsa stain and by the immunochromatographic card test. The immunodiagnostic test had a sensitivity of 93.1% and a specificity of 95.8%, making a good alternative for malaria diagnosis especially in rural areas without electricity, where microscopy is not possible, and a decision is to be made on when to start treatment.

Purification and characterisation of an extracellularly released protease of Trypanosoma brucei.

Thrombocytopaenia, or platelet aggregation, is a serious complication of African trypanosomiasis. The biochemical basis is not clearly known. Proteases are known potent inducers of blood coagulation and platelet aggregation, and unknown factors released by Trypanosoma brucei have been shown to induce platelet aggregation. In attempts to define the biochemical mechanisms involved in thrombocytopaenia we purified and characterised a major proteolytic enzyme released extracellularly by T. brucei. Actively motile trypanosomes released proteins into the medium (phosphate saline/glucose, pH 8.0) in which the organisms were incubated in vitro. The M(r) of the released polypeptides ranged from 15 to > 200 kDa, amongst which are proteases. One of the major protein bands, a 250 kDa protease, was purified to homogeneity by ammonium sulfate precipitation followed by diethylaminoethyl (DEAE)-cellulose chromatography and Sephacryl S-300 gel filtration. The protease migrated as a single band of 63 kDa upon electrophoresis in both denaturing and non-denaturing gel co-polymerised with gelatin. The enzyme was strongly active against Z-ARR-AFC peptide substrate, with a pH optimum of 7.0. The proteolytic activity was enhanced by dithiothreitol and inhibited by E-64, leupeptin, TPCK and antipain. The released proteolytic enzyme is putatively identified as a cathepsin B-like cysteine protease.