Full Length Research Paper

Limited variation of the 5’cis-control region of the transmission blocking vaccine candidate Pfs25 amid great genetic diversity of Plasmodium falciparum in Cameroon

Wilfred Fon Mbacham¹*, Patrice Nsangou Mimche¹, Palmer Masumbe Netongo¹, Evehe Bebandoue Marie-Solange¹, Akindeh Nji¹, Immaculate Amunom¹, Johanna Daily², Valerie Makoge¹, Kayla Laserson^2, Songmbe Michael Yong³, Nicoline Lomah³, Peter Enyong⁴, Vincent P. Titanji³ and Dyann F. Wirth²

¹The Biotechnology Center, University of Yaounde I, Cameroon.

²Department of Immunology and Infectious Diseases, Harvard School of Public Health, U.S.A.

³Biotechnology Unit, University of Buea, Cameroon.

⁴Center for Medical and Medicinal Plant Research, Ministry of Scientific Research, Kumba, SWP, Cameroon.

*Corresponding author. E-mail: wfmbacham@yahoo.com. Tel:  77579180. Fax: 22019778.

Accepted 6 February, 2008

Genetic recombination during sexual reproduction within Plasmodium sp. contributes to parasite diversity and altered gene expression of certain surface markers. The pfs25 gene involved in the upset of gametocytogenesis is a candidate antigen in transmission blocking vaccine. This study investigated the polymorphism of Pfs25 within its 5’cis-control region in field isolates from different ecotypes in Cameroon.  Symptomatic patients and asymptomatic healthy school children with a positive smear and from different ecozones were included. Parasite DNA was extracted and polymorphisms within pfs25, cg2-ω, msp-1, msp-2 and glurp genes were investigated by PCR-RFLP and DNA sequencing.  Putative control elements of the 5’cis control regions of Pfs25 were identified by PCGENE software and enzymes were selected whose sequences produced or abolished restriction sites by mutations. Malaria infection was mainly caused by Plasmodium falciparum with sporadic occurrence of Plasmodium malariae and Plasmodium ovale. Analysis of the Pfs25 5’ cis-control region identified only one polymorphism (0.002%) that abolished an RsaI restriction site as part of the sequence TTTCTGTAC, located 40 bp downstream of the promoter and found at – 478 bp of the ATG. Analysis of the 5’ cis-control sequence of Pfs25 revealed minimal variation of the promoter region amid great zonal differences in parasite population. Altitudinal differences in parasite populations were not easily discernable.

Key words: Plasmodium falciparum, Pfs25, cis-control elements, genetic polymorphism.