Genotyping of Iranian Plasmodium vivax populations by using circumsporozoite protein gene (CSP) marker

Although circumsporozoite protein of Plasmodium vivax (Pvcsp) has been considered to be a potential vaccine candidate, there was no information about the sequence variation in CSP of Iranian P. vivax. In current study, the prevalence of two types of Pvcsp was determined by PCR-RPLP in 374 P. vivax infected patients. In north, with one exception, all parasites were VK210, however, in south both types were present. Mixed infections were common in south (12%), but it has not been observed in northern isolates. We also examined the genetic diversity of Pvcsp gene by sequencing analysis of 137 out of 374 field isolates obtained from resurgent parasite in north and endemic areas, in south of Iran. We have also found very limited polymorphism in the non-repetitive region of the gene in all isolates. However, repeated region of all sequenced samples showed variation in number of repeat, and also base substitutions was occurred which suggested that point mutation have caused the emergence of the variant sequence in Iranian isolates. Also such variation was much more in VK210 type than in those of VK247 type and also in southern isolates comparing to north. We also reported one novel sequence with new mutation (A/P) from southern isolate. Also few isolates have 2 copies of 19 AA insertions in post-repeated region, which has not been reported previously. The sequence data reported here provide more genetic information on P. vivax populations particularly from central Asia for the first time, which has also important implications for both practical measures aimed at developing control programs, and on future field-based vaccine trials with Pvcs protein antigen.

Keywords:

Malaria , Plasmodium vivax , Circumsporozoite , VK210 , VK247 , polymorphism , sequence , Iran