Analysis of antibody responses to selected Plasmodium falciparum merozoite surface antigens in mild and cerebral malaria and associations with clinical outcomes

Merozoite surface proteins (MSPs) are critical for parasite invasion; they represent attractive targets for antibody-based protection against clinical malaria. To identify protection-associated target MSPs, the present study analysed antibody responses to whole merozoite extract (ME) and to defined MSP recombinant antigens in hospitalized patients from a low endemic urban area as a function of disease severity (mild versus cerebral malaria). Sera from 110 patients with confirmed severe cerebral malaria (CM) and 91 patients with mild malaria (MM) were analysed (mean age = 29 years) for total and subclass immunoglobulin (Ig)G to ME and total IgG to MSP1p19, MSP2, MSP3, MSP4 and MSP5 by enzyme-linked immunosorbent assay (ELISA). Functional antibody responses were evaluated using the antibody-dependent respiratory burst (ADRB) assay in a subset of sera. There was a trend towards higher IgG1 and IgG4 levels to ME in CM compared to MM; only ME IgM responses differed significantly between fatal and surviving CM patients. Increased prevalence of IgG to individual MSPs was found in the CM compared to the MM group, including significantly higher levels of IgG to MSP4 and MSP5 in the former. Sera from fatal (24·5%) versus surviving cases showed significantly lower IgG to MSP1p19 and MSP3 (P < 0·05). ADRB assay readouts correlated with high levels of anti-MSP IgG, and trended higher in sera from patients with surviving compared to fatal CM outcome (P = 0·07). These results document strong differential antibody responses to MSP antigens as targets of protective immunity against CM and in particular MSP1p19 and MSP3 as prognostic indicators.

[Profiles of IgG responses against CSP, GLURP and LSA-3NR2 in urban malaria (Dakar): relations with haemoglobin levels and parasite densities]

Malaria remains a major health problem in sub- Saharan African countries despite substantial decreases in morbidity and mortality due to sustained control programs. Vaccines candidates were mainly tested in rural endemic setting; however increasing proportion of the population is living in urban area. Evaluation of the qualitative or quantitative immune responses to key targets of anti-Plasmodium immunity requires further investigation in urban area. In a cohort of 144 patients with mild malaria living in Dakar, we analyzed IgG responses against target antigens of P. falciparum: CSP, LSA-3NR2 and GLURP by ELISA. A mean age of 15 yrs (4-65 yrs) was found and patients were separated in 59 adults (<15yrs) and 85 children (≤15 yrs). Parasites densities (0,01-15%) did not differ between the two age groups. In contrast, haemoglobin levels appeared lower in children (4.5-16.6 g/dl) (p<0.01). For the immune results, the most recognized antigens were GLURP and CSP compared to LSA-3NR2. Levels of IgG against these antigens were significantly different between the two age groups and they were positively correlated (rho = 0.32; p<0.001). In addition, levels of IgG anti-GLURP were associated with low parasitemia (≤1%) and absence of anemia (≥11g/dl), particularly in adults (p<0.001). In a multiple regression analysis, no significant relationship was found between parasite densities and IgG responses against all the tested antigens. Our study shows the implication of IgG anti-GLURP in humoral immune response against the parasite. The present work contributes to determine IgG levels that can be used as relevant immunologic biomarkers in urban clinical malaria.

[IgG responses to candidate malaria vaccine antigens in the urban area of Dakar (Senegal): evolution according to age and parasitemia in patients with mild symptoms]

Malaria remains a major problem in African countries despite substantial decreases in morbidity and mortality due to sustained control programs. Studies for the evaluation of qualitative or quantitative Ab responses to key targets of anti-plasmodium immunity were mostly done in rural endemic setting compared to urban area. In a cohort of 200 patients with mild malaria and living in Dakar, we analyze total and subclasses IgG responses to a panel of P. falciparum blood stage antigens: MSP1p19, MSP3, EB200, GST-5 and R23. A mean age of 15 yrs (4 to 56 yrs) and parasitemia between 0.1 to 17% were found. Levels of IgG anti-MSP3 were higher in patients with low parasitemia (≤1%) and appear negatively correlated to parasite densities (Rho =. 0.54; p= 0.021). This correlation is more significant in children (≤ 15 yrs). In addition, an increase of IgG responses against MSP1p19 is highly observed in adults having a parasitemia less than 1%. In those patients, we find that IgG1 subclasses were predominant (p <0.01). Our study shows an association between Ab responses and parasitemia. This association is dependant to IgG anti-MSP3 in children and IgG anti-MSP1p19 in adults living in urban area.

[Evaluation of an immunoassay for calcitonin]

INTRODUCTION

The calcitonin is the most specific and the most sensitive marker of medullary thyroid carcinoma (MTC) both for screening and postoperative follow-up of the patients. Its measurement is made either remotely , or after stimulation of pentagastrin secretion which the answer is amplified at the carrier of CMT. The aim of this study was to estimate a chimioluminescent method by comparing it with an immunoradiological method, manual, used as reference. Correlation study was done.

MATERIALS AND METHODS

Two hundred and sixty three serums (263) were tested among which 64 resulting of healthy subjects and 199 resulting of patients affected) by medullary thyroid carcinoma. Statistical analysis of results was made by a study of correlation with the software OriginLab version 7.0. The manual technique used as reference method is radioimmunological (Elsa hCT, international Cisbio, Gif on Yvette, France). It was compared with a chimioluminescent technique (Nichols Advantage, Nichols Institute Diagnostics, CA, the USA).

RESULTS

The coefficients of correlation obtained between both tests were: r = 0.76 (exactness study), r = 0.91 (after stimulation), r = 0.95 and 0.79 (staged samples), r = 0.99 (M TC patients).

CONCLUSIONS

Both techniques correlate strictly and significantly. The correlation coefficients we obtained show us that Nichols Advantage Calcitonin is completely reliable and sensitive for the measurement of the hCT in the follow-up of the CMT.

[Frequency of microalbuminuria during diabetes in Dakar, Senegal]

Nephropathy is one of the complications occuring during diabetes and it is diagnosed via microalbuminuria. From 1992 to 1999, five hundred and eighty seven (587) diabetic patients were recruited and distributed into two groups, A (n = 270) and B (n = 317). Microalbuminuria was determined by immunonephelemetry for group A and immunoturbidimetry for group B. The results showed respectively 15.5% and 20.19% pathological cases in the two groups (NS). Considering the distribution of patients with microalbuminuria according to the type of diabetes, there were 16.12% type 1 and 15.07% type 2 in group A against 22.60% and 18.13% in group B; no statistically significant differences were observed either in the same group or from one group to another. These frequencies might reflect the situation in the nineties; they are lower than those encountered in other populations. Nevertheless monitoring is needed through a regular schedule to prevent nephropathy.

[Frequency of micoalbuminuria during diabetes in Dakar (Senegal)]

Nephropathy is one of the complications occuring during diabetes diagnosed via microalbuminuria. From 1992 to 1999, five hundred and eighty seven (587) diabetic patients were recruited in groups A (n = 270) and B (n=317). Microalbuminuria was determined by immunonepheletry for A and immunoturbidimetry for B. The results pointed out respectively 15.5% and 20.19% pathological cases (NS). Considering the distribution of patients with microalbuminuria according to the type of diabetes there were 16.12% type 1 and 15.07% type 2 in group A against 22.60% and 18.13% in group B ; no stastically significant differences were observed either in the same group or from one group to another. These frequencies would reflect the situation in the nineties; they are lower than those encountered in other populations. Nevertheless monitoring is needed through a regular schedule to prevent nephropathy.