Conference Papers
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This collection contains abstracts of conference papers, presented at local and international conferences by the staff of the Faculty of Medicine
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Item Hypervariability in a leading P.vivax malaria vaccine candidate, C-terminal merozoite surface protein 1(Sri Lanka Association for the Advancement of Science, 2000) Manamperi, A.; Holm, I.; Perera, L.; Handunnetti, S.M.; Longacre, S.It is widely accepted that the C-terminal 42 kDa (p42) and 19 kDa (p19) processing fragments of plasmodium Merozoite Surface Protein-1 (MSP-1) are targets of immune protection. To begin to assess the degree of polymorphism in these MSP-1 vaccine candidates, we have investigated the sequence diversity in the p.vivax MSP-1 p42 processing fragment, in 19 natural isolates, from p.vivax infected patients in Kataragama. Sequence analysis of PvMSP-1 p42 in the 19 PCR positive isolates reveald 11 sequences of Belem origin and 8 sequences of Salvador-1 (Sal-1) origin. Among the isolates, these two stains are 98-100% homologous across this region, with one notable exception. This corresponds to a highly polymorphic block of 38 amino acids (24% amino acid homology among isolates). However, this polymorphism appears to be derived largely by re-assorting a dimorphism at each variable position. This type of restricte variability suggests that in spite of its diversity, there may nevertheless be a defined structure for this region of the molecule and that the diversity may be functionally important. Alternatively, it may be specifically designed for maximal effect in immune evasion, as a highly exposed immunogenic loop structure. In striking contrast, a single nucleotide substitution was detected in the cysteine rich C-terminal 19 kDa region, resulting in a lysine to glutamate substitution. This was detected in only one isolate among the 19 isolates investigated for sequence diversity. Since the PvMSP-1 C-terminal antigen is clearly hypervariable in the context of natural infections, a vaccine based on a single version of this antigen, might not induce an effective immunity against the multiple forms. In contrast, the PvMSP-1 p19 domain appears to be well conserved and thus appears to be a considerably more promising vaccine candidate.Item A pilot study on comparison of rapid immunodiagnostics for confirmation of leptospirosis(Sri Lanka Medical Association, 2012) Eugene, E.J.; Wickramasinghe, S.A.; Kalugalage, T.L.; Rodrigo, C.; Wickremesinghe, H.; Dikmadugoda, N.; Somaratne, P.; de Silva, H.J.; Rajapakse, S.; Handunnetti, S.M.INTRODUCTION: In Sri Lanka, leptospirosis is mostly diagnosed on clinical grounds. Serological confirmation is not obtainable during the acute stage of the illness. There is a need for rapid immunodiagnostics for confirmation of leptospirosis. Two immunodiagnostic assays, ie: enzyme linkedimmnnosorbent assay (ELISA) and immunochromatographic technique Leptocheck-WB test (LCT) areused to detect leptospira specific IgM antibodies which are prevalent in early stages of acute infections. AIMS: To compare the efficacy of these two rapid immunodiagnostic assays with the microscopic agglutination assay (MAT) to determine their applicability. Methods: A set of sera (n=83) collected in 2010 for which MAT titres were available was used to perform IgMELISAandLCT. RESULTS: Positivity for LCT and IgM ELISA were 55.4% and 48.2% respectively, and both assays detected acute infection by day 3 of the illness. MAT> 400 was used as the reference standard. For LCT, the overall sensitivity, specificity, accuracy, PPV and NPV (86.5%, 75.0%, 79.6%, 69.6% and 89.4% respectively) were higher compared to the respective values for IgM ELISA (50.0%, 62.3%, 57.1%, 50.0%, 62.3%). The highest of these values were observed during the first week for LCT and during the second week for IgM ELISA. The highest agreement was observed between LCT and MAT>400 (p=0.568) and there was a good agreement between LCT and IgM ELISA (p=0.520). CONCLUSIONS: The high sensitivity and specificity, ease of use, and non-requirement of specialized skills and equipment makes LCT a good choice for screening, while IgM ELISA is an appropriate test for confirming acute leptopsirosis.