Comparative Study of Some Biochemical Factors in Human Erythrocytes Exhibiting "Early11 and "Delayed" Re-Infection to placimodium falciparum

Abstract

Malaria remains the most important of all tropical diseases. Some 200 million individuals in 102 countries are at risk. Nearly 85% of the cases and 90% of the carriers are found in tropical Africa. In Kenya, out of a total population 30 million 22 million people are at risk of infection. Previous studies at Saradidi, Western Kenya have indicated that malaria (P. falciparum) , infection varies from individual to individual. In one such study a group of inhabitants within similar geographical environment and having similar incidence of malaria, were initially treated for malaria and later monitored for re-infection for a period of 96 days. Results from that study indicated that some individuals were re-infected by the malaria parasites much earlier than others. For comparative study of these inhabitants, those that were re-infected before 96 days were classified as "early re-infected group" whereas those that were re-infected after 96 days were classified as "delayed re-infected group" Studies have shown that several factors in red blood cells determine the degree of infection by P. falciparum. Among the factors that have been shown to limit the invasion and growth of malaria parasites in red blood cells include; immunological factors, glucose-6-phosphate dehydrogenase, pyridoxal Kinase and haemoglobin variants among others. The present study was conducted to establish the following: (a) Whether there occurred significant difference in in vitro growth of P. falciparum in red blood cells obtained from person exhibiting "early" and "delayed" re-infection. Significant difference in in vitro growth would relate the difference in re-infection to factors within the red blood cell other than immunological factors. (b) Whether there occurred a significant difference in glucose-6-phosphate dehydrogenase and pyridoxal kinase activity in the red blood cells obtained from the two groups of persons. (c) Determine haemoglobin variants in the red blood cells obtained from the two groups of persons. The results in the present study showed no significant difference in percent parasitaemia, growth rate and (3H) Hypoxanthine incorporation in the red blood cells from persons exhibiting "early" and "delayed" re-infection with P. falciparum. Glucose-6-phosphate dehydrogenase and pyridoxal kinase activity showed a statistically significant higher means in the 'early" re-infected group compared to the "delayed" re-infected group. This suggests that the difference in malaria susceptibility by the red blood cells from the two groups of persons may be attributed to these enzymes. Results from haemoglobin variant analysis showed that the "early" re-infected group had 69% with haemoglobin AA and 31% haemoglobin AS. In the "delayed" re-infected group 25% had haemoglobin AA and 75% haemoglobin AS. These results confirm earlier studies which support the view that haemoglobin AS has some protective advantage against malaria infection.