Abstract:
The quantity of the intra-erythrocytic deoxyhemoglobin S (Hb S) affects the level of protection against malaria and also the sickling phenomenon. This study reports on significantly
lower concentration of Hb S in females than males. Data came from 350 children, aged 12–
47 months who participated in a phase 2b malaria vaccine trial. Hemoglobinopathy and
G6PD deficiency typing was necessary to ascertain equal representation of these malaria
protective traits across the vaccine cohorts. Hemoglobin types (HbAA, HbAS) and % Hb S
were evaluated by HPLC. Alpha thalassemia (alpha-thal) and G6PD genotypes were evaluated by PCR. The overall prevalence for HbAS was 20%, 46% for 3 alpha genes and 10%
for 2 alpha genes and 14% for G6PD A-. More females of HbAS/αα/αα genotype had low Hb
S than males and had mean % Hb S of 37.5% ± 5.4 SD, compared to 42.0% ± 2.5 SD in
males of same genotype (P = 0.018). Consistent with reduction of the malaria protective Hb
S in females, parasite load in females was nearly twice that of males but the difference was
not statistically significant. The X-chromosome linked G6PD deficiency did not influence the
level of Hb S. We conclude that, the low Hb S in these females explains the resultant higher
malaria parasite load. We speculate that the low Hb S in females could also explain observations suggesting that the sickling phenomenon tends to be less severe in females than
males.
