Prevalence of fetal hemoglobin and antibody responses to plasmodium falciparum antigens in sickle cell disease patients in Western Kenya
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Date
2016-06
Authors
Webala, Brenda Akinyi
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Malaria is a major public health problem worldwide with increasing cases and
deaths in sub-Saharan Africa. Sickle cell disease conditions relate geographically
with malaria endemic areas. Fetal hemoglobin (HbF) moderates the clinical severity
of sickle cell disease (SCD) and also provides protection against malaria.
Consequently, it provides survival advantage but the data is limited. Designing a
study linking HbF with protection against malaria infection has been a challenge
due to potential confounders on the exposure outcome. This study therefore
investigated the prevalence and levels of HbF and the IgG responses to Plasmodium
falciparum antigens in 100 SCD patients aged 5-30 years living in a malariaendemic
area in Western Kenya. A cross-sectional study was conducted to
determine the prevalence and levels of HbF and the IgG responses to a panel of
eleven recombinant P. falciparum antigens in SCD patients. The levels of HbF and
the IgG responses to each of the 11 antigens were determined using the alkali
denaturation (Betke) method and the cytometric bead assay in a Luminexsuspension
array technology respectively. The study reports a prevalence of up to 77
% of the SCD patients with high fetal hemoglobin (>10%) with a mean and range of
19.09% (1.44-56.25%) respectively. Generally the levels of HbF increased with age
(r = 0.17, P < 0.05) indicating that fetal hemoglobin provides survival advantage in
SCD, in males there was an increase in HbF with age (r=0.31; P<0.05) while in
females it was not significant (r = 0.02; P>0.05). The IgG responses to the multiple
P. falciparum antigens were differently expressed in the SCD patients, preerythrocytic
antigens showed a statistical difference when the mean IgG levels were
compared using unpaired T test between the seropositive SCD patients and non-
SCD individuals with the later having high IgG levels (P<0.05). In contrast LSANRC
had high IgG levels in SCD patients (P<0.05). The IgG responses to blood
stage antigens on the other hand were not statistically different between the SCD
patients and non- SCD individuals (P>0.05). The IgG responses to MSP-1-42-FVO
were high both in the seropositive SCD and non-SCD individuals. However, when
compared with the non-SCD individuals using unpaired T-test, the non- SCD
individuals had significantly high levels of IgG responses to both the preerythrocytic
and the blood stage antigens than the SCD patients (P<0.05). Using
Spearmans’ rank correlation analysis, HbF positively correlated with the IgG
responses to LSA-NRC (r= 0.26; P<0.05), other antigens showed no correlation.
This implies that HbF can provide protection against malaria in SCD patients living
in malaria endemic areas and thus increase their life expectancy. The findings also
reinforce the previous findings that antibody cooperates with fetal hemoglobin to
provide protection against malaria. Nonetheless, further rigorous study design
approach should be used for investigations on the role of HbF on pathogenesis and
chemotherapy of malaria in SCD patients.
Description
A Thesis Submitted in Partial Fulfillment 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. June 2016