Abstract:

Objective To analyze the relationship between the TEP1 gene of Anopheles stephensi and melanotic encapsulation of Plasmodium yoelii induced by anti-malaria drug nitroquine. Methods Haemolymph samples from three groups of An. stephensi fed with sucrose solution, Plasmodium-infected blood and nitroquine, respectively, were collected at the 1st, 2nd, 3rd and 4th day after drug adminstration. Degenerate primers were designed according to the conserved amino acid sequence within TEPs of the mosquitoes. Fluorescent quantitation PCR was used to detect the variation of TEP1 gene transcript induced by nitroquine. The melanization of oocysts was observed by light microcopy. Results TEP1 gene was cloned, the predicted amino acid residues harbored a highly conserved canonical thioester motif GCGEQ. The fluorescent quantitation PCR revealed that nitroquine induced an up-regulation of TEP1 activity. The transcription of TEP1 gene in nitroquine treated group （2.423） was significantly higher than that of the infected blood-fed group（1.036） at the 3rd day after nitroquine treatment （P<0.05）. At the same time, most oocysts were found to be encapsulated in nitroquine treated group, while no melanized parasites were observed in the infected blood-fed group. Conclusion Transcriptional variation of TEP1 gene may be related to the melanization induced by nitroquine.

Key words: Nitroquine, TEP1, Anopheles stephensi, Plasmodium yoelii, Oocyst, Melanotic encapsulation