Antibody prevalence and levels to plasmodium falciparum circumsporozoite protein and schizont extract in individuals living in Kipsamoite, Nandi County, Kenya
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Date
2016-10
Authors
Walukhu, Michael Kisongochi
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Malaria continues to be a major public health concern despite the concerted efforts to
eliminate it. The quest for a vaccine remains a top priority. Antibodies to Plasmodium
falciparum antigens are involved in prevention of infection and disease in animal models.
The role of these antibodies has also been demonstrated in human with some of the
antigens being targeted as lead candidates in vaccine development. However, the
association of age and gender with antibody responses to these antigens is not clearly
understood. Moreover, most of the studies have been done in endemic areas with little
emphasis in areas of low and unstable malaria transmission. This study sought to
determine whether age and gender affect antibody responses to P. falciparum antigens by
measuring antibody levels and prevalences to recombinant circumsporozoite protein
(CSP) and crude schizont extract (SE) in individuals of all ages living in an area where
malaria transmission is low and unstable in western highlands of Kenya. Both male and
female of all ages were recruited, blood samples collected and plasma obtained. Sixty
samples were randomly selected and categorized into three age groups; <8years (n=25),
8-18years (n=21) and >18years (n=14). The participants were also categorized into males
(n=30) and females (n=30) to determine the effect of gender on antibody responses.
Seven samples from malaria narve individuals from North America were used as negative
controls while 30 pooled plasma samples from individuals in areas of stable malaria
transmission were used as positive controls. Measurement of parasitaemia in all samples
was done by light microscopy using both thin and thick blood smear. Haemoglobin levels
were measured by photometry while IgG antibodies levels in plasma were measured by
Enzyme Linked Immunosorbent Assay (ELISA). Data analysis was done by Graphpad
Prism 6 using non-parametric Wilcoxon rank sum, Mann Whitney 1), Kruskall- Wallis
and Spearman rank correlation tests. The prevalence of antibodies was generally low
across all age groups ranging from 0% to 14.29% at arbitrary units (AU»2 for the two
antigens. The antibody prevalence however increased with age. Males had significantly
higher antibody prevalence than females with males having 10% while females 3.33% at
AU>2 for both antigens P<0.05." The levels of IgG antibodies were generally low and
there were no significant differences among the age groups and between male and
females (P>0.05). There was a correlation between antibody levels to CSP and SE
(r=0.5977; P<0.05). The study "provides preliminary findings associating antibody
responses with the exposure to malaria infection. It therefore recommends a longitudinal
study on more antigens to inform exploration of multi-antigen vaccines and also adopt
several control measures including Epidemic Preparedness and Response (EPR). It
further recommends profiling immune responses of individuals living in epidemic prone
areas.
Description
A thesis submitted in partial fulfilment of the requirements for the award of the degree of master of science (immunology) in the School of Pure and Applied Sciences of Kenyatta University. October, 2016