Browsing by Author "Reddy, S. B."

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Development of Plasmodium falciparum specific naïve, atypical, memory and plasma B cells during infancy and in adults in an endemic area
(Bio Med Central, 2017) Lugaajju, A; Reddy, S. B.; Wahlgren, M; Kironde, Fred; Persson, K. E. M.
Background: B-cells are essential in immunity against malaria, but which sub-sets of B-cells specifically recognize Plasmodium falciparum and when they appear is still largely unknown. Results: Using the flow cytometry technique for detection of P. falciparum specific (Pf+) B-cells, this study for the first time measured the development of Pf+ B cell (CD19+) phenotypes in Ugandan babies from birth up to nine months, and in their mothers. The babies showed increases in Pf+ IgG memory B-cells (MBCs), atypical MBCs, and plasma cells/blasts over time, but the proportion of these cells were still lower than in the mothers who displayed stable levels (5, 18, and 3%, respectively). Pf+ non-IgG+ MBCs and naïve B-cells binding to P. falciparum antigens were higher in the babies compared to the mothers (12 and 50%). In ELISA there was an increase in IgG and IgM antibodies over time in babies, and stable levels in mothers. At baby delivery, multigravidae mothers had a higher proportion of Pf+ IgG MBCs and less Pf+ naïve B-cells than primigravidae mothers. Conclusions: In newborns, naïve B-cells are a major player in recognizing P. falciparum. In adults, the high proportion of Pf+ atypical MBCs suggests a major role for these cells. Both in infants and adults, non-IgG+ MBCs were higher than IgG MBCs, indicating that these cells deserve more focus in future.
Differences in affinity of monoclonal and naturally acquired polyclonal antibodies against Plasmodium falciparum merozoite antigens
(2015) Reddy, S. B.; Anders, R. F.; Cross, N; Mueller, I; Senn, N; Stanisic, D. I.; Siba, P. M.; Wahlgren, M; Kironde, Fred; Beeson, J. G.; Persson, K. E. M
Background: Malaria is a major global cause of deaths and a vaccine is urgently needed. Results: We have employed the P. falciparum merozoite antigens MSP2-3D7/FC27 and AMA1, used them in ELISA, and coupled them in different ways using surface plasmon resonance (SPR) and estimated affinity (measured as kd) of monoclonal as well as naturally-acquired polyclonal antibodies in human plasma. There were major differences in kd depending on how the antigens were immobilized and where the His-tag was placed. For AMA1 we could see correlations with invasion inhibition. Using different immobilizations of proteins in SPR, we could see only moderate correlations with levels of antibodies in ELISA, indicating that in ELISA the proteins were not uniformly bound and that antibodies with many specificities exist in natural immunisation. The correlations between ELISA and SPR were enhanced when only parasite positive samples were included, which may indicate that high affinity antibodies are difficult to maintain over long periods of time. We found higher kd values for MSP2 (indicating lower affinity) compared to AMA1, which might be partly explained by MSP2 being an intrinsically disordered protein, while AMA1 is globular. Conclusions: For future vaccine studies and for understanding immunity, it is important to consider how to present proteins to the immune system to achieve highest antibody affinities.