Browsing by Author "White, M.T."
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Item Dynamics of the antibody response to Plasmodium falciparum infection in African children(Journal of Infectious Diseases, 2014-04) White, M.T.; Griffin, J.T.; Akpogheneta, O.; Conway, D.J.; Koram, K.A.; Riley, E.M.; Ghani, A.C.Background. Acquired immune responses to malaria have widely been perceived sto be short-lived, with previously immune individuals losing immunity when they move from malaria-endemic areas. However longlived Plasmodium falciparum-specific antibody responses lasting for an individual's lifetime are frequently observed. Methods. We fit mathematical models of the dynamics of antibody titers to P. falciparum antigens from longitudinal cohort studies of African children to estimate the half-lives of circulating immunoglobulin G (IgG) antibodies and IgG antibody-secreting cells (ASCs). Results. Comparison of antibody responses in the younger Ghanaian cohort and the older Gambian cohort suggests that young children are less able to generate the long-lived ASCs necessary to maintain the circulating antibodies that may provide protection against reinfection. Antibody responses in African children can be described by a model 15 including both short-lived ASCs (half-life range, 2-10 days), which are responsible for boosting antibody titers following infection, and long-lived ASCs (half-life range, 3-9 years), which are responsible for maintaining sustained humoral responses. Conclusions. The rapid decay of antibodies following exposure to malaria and the maintenance of sustained antibody responses can be explained in terms of populations of short-lived and long-lived ASCs. © The Author 2014.Item Potential effects of warmer worms and vectors on onchocerciasis transmission in West Africa(Philosophical Transactions of the Royal Society B: Biological Sciences, 2015-04) Cheke, R.A.; Basáñez, M.-G.; Perry, M.; White, M.T.; Garms, R.; Obuobie, E.; Lamberton, P.H.L.; Young, S.; Osei-Atweneboana, M.Y.; Intsiful, J.; Shen, M.; Boakye, D.A.; Wilson, M.D.Development times of eggs, larvae and pupae of vectors of onchocerciasis (Simulium spp.) and of Onchocerca volvulus larvae within the adult females of the vectors decrease with increasing temperature. At and above 258C, the parasite could reach its infective stage in less than 7 days when vectors could transmit after only two gonotrophic cycles. After incorporating exponential functions for vector development into a novel blackfly population model, it was predicted that fly numbers in Liberia and Ghana would peak at air temperatures of 298C and 348C, about 38C and 78C above current monthly averages, respectively; parous rates of forest flies (Liberia) would peak at 298C and of savannah flies (Ghana) at 308C. Small temperature increases (less than 28C) might lead to changes in geographical distributions of different vector taxa. When the new model was linked to an existing framework for the population dynamics of onchocerciasis in humans and vectors, transmission rates and worm loads were projected to increase with temperature to at least 338C. By contrast, analyses of field data on forest flies in Liberia and savannah flies in Ghana, in relation to regional climate change predictions, suggested, on the basis of simple regressions, that 13–41% decreases in fly numbers would be expected between the present and before 2040. Further research is needed to reconcile these conflicting conclusions. © 2015 The Author(s) Published by the Royal Society. All rights reserved.