Low genetic diversity and functional constraint in loci encoding Plasmodium vivax P12 and P38 proteins in the Colombian population.

BACKGROUND

Plasmodium vivax is one of the five species causing malaria in human beings, affecting around 391 million people annually. The development of an anti-malarial vaccine has been proposed as an alternative for controlling this disease. However, its development has been hampered by allele-specific responses produced by the high genetic diversity shown by some parasite antigens. Evaluating these antigens' genetic diversity is thus essential when designing a completely effective vaccine.

METHODS

The gene sequences of Plasmodium vivax p12 (pv12) and p38 (pv38), obtained from field isolates in Colombia, were used for evaluating haplotype polymorphism and distribution by population genetics analysis. The evolutionary forces generating the variation pattern so observed were also determined.

RESULTS

Both pv12 and pv38 were shown to have low genetic diversity. The neutral model for pv12 could not be discarded, whilst polymorphism in pv38 was maintained by balanced selection restricted to the gene's 5' region. Both encoded proteins seemed to have functional/structural constraints due to the presence of s48/45 domains, which were seen to be highly conserved.

CONCLUSIONS

Due to the role that malaria parasite P12 and P38 proteins seem to play during invasion in Plasmodium species, added to the Pv12 and Pv38 antigenic characteristics and the low genetic diversity observed, these proteins might be good candidates to be evaluated in the design of a multistage/multi-antigen vaccine.