Frequency of Southeast Asian Ovalocytosis (SAO) and Malaria Resistance in Sentani, West Papua

Malaria has been an important natural selection in human population that maintained red blood cell variants in which protect them against malaria. Southeast Asian Ovalocytosis (SAO) is one of the red blood cell variants suggested to be a host response to protect against malaria which is common found in Southeast Asia. This erythrocyte variant is caused by a 27-bp deletion of the AE1 gene erythrocyte membrane on chromosome 17 which encode Band 3 protein. However, the mechanism of SAO to protect individual against malaria is remain unclear. In an attempt to provide evidence for the possible role of the SAO trait, the malaria susceptibilities of normal and SAO individual were compared. Observing red cell oval morphology under microscope is still the only accepted basis for diagnosis of SAO. However, errors when detecting and counting morphological SAO are inevitable. Therefore, confirming the result of the morphologically observation by more accurate method such screening SAO of the 27-bp deletion of band 3 gene by PCR method were conducted. Blood sample were collected from Sentani, West Papua. Thin and thick blood smears were stained with Giemsa and examined under binocular light microscope. DNA was isolated from blood blots on filter paper and then used for molecular analysis of the 27-bp deletion of erythrocyte band 3. Result of the survey revealed false positive (14.28%) and false negative (3,93%) while base on morphology diagnosis were compared to molecular method. SAO frequency 7,6% (79/1041) and malaria infection prevalence 16,7% (174/1041) respectively. In total sample, malaria parasite rate is higher in SAO individual (20,3% [16/79]) than in those normal individual (16,4% [158/1041). These results suggested that SAO did not confer resistance to malaria parasite invasion. It might suggest that SAO confer selective advantage at the next stage after parasite invasion, such as bad growth of malaria parasite in ovalocytes and cytoadherence interfere result in prevent cerebral malaria.

Keyword: Southeast Asian Ovalocytosis (SAO); Malaria; Band 3 Protein; Papua; Austronesian