Abstract:
Background: High Immunoglobulin G (IgG) response to Plasmodium falciparum antigens is associated with partial
malaria protection in sickle hemoglobin (HbS) children. However, this response has been more studied in children
with heterozygous sickle cell trait (HbAS) but little explored in those with homozygous sickle cell trait (HbSS). The
current study was conducted to determine the IgG responses against specific Plasmodium falciparum antigens in
children with homozygous sickle cell trait (HbSS) by comparing to those with normal hemoglobin (HbAA).
Methods: A cross sectional study was conducted between April and July 2018 in Dar es Salaam tertiary hospitals.
Parents were consented for their child to give about 5 ml of venous blood. IgG concentration from the blood
plasma of 220 children (110 HbAA vs. 110 HbSS) were determined using indirect Enzyme Linked Immunosorbent
Assay (ELISA). Then IgG medians were compared between the groups with prism 5 software (GraphPad) using
Mann Whitney U test. Where the differences in age, hemoglobin levels and body weight between the groups was
analyzed using independent sample t test. Multiple linear regressions were used to control cofounding variables
such as body weight, age and hemoglobin level using statistical package for social sciences software (SPSS version
23). P value <0.05 was considered statistically significant.
Results: The median IgG concentration to PfEBA-175, Pfg27, yPfs28C antigens were HbSS; 20.7 ng/ml (IQR; 18.1–25.
6) vs. HbAA; 2.3 ng/ml (IQR; 1.21–3.04), HbSS; 2.76 ng/ml (IQR: 2.08–5.69) vs. HbAA; 1.36 ng/ml (IQR: 1.28–1.76), and
HbSS; 26,592 ng/ml (IQR: 10817–41,462) vs. HbAA; 14,164 ng/ml (IQR; 3069–24,302) respectively (p < 0.0001 for all
IgG). In both groups; age, body weight and hemoglobin level had no impact on the levels of IgG responses to
Plasmodium falciparum antigens except for HbAA group which showed a significant increase in IgG against Pfg27
by 0.004 ng/ml with 1 g/dl increase in Hb level (p = 0.028).
Conclusions: This study found significant higher levels of specific Plasmodium falciparum IgG responses in children
with homozygous sickle cell trait than those with normal hemoglobin
