Correlation of Pfg377 ortholog gene expression of Plasmodium vivax and mosquito infection.

OBJECTIVE

To determine the expression of Pfg377 ortholog gene in Plasmodium vivax, and examine its correlation with mosquito infection.

METHODS

Seventy clinical blood samples positive for P. vivax by microscopy, were used for the mosquito infectivity assay. Infectivity to female Anopheles dirus was determined from oocyst counts. The transcripts of Pfg377 ortholog gene of P. vivax from blood samples infective and non-infective to mosquitoes were examined using quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

Of 70 P. vivax positive blood samples, 50 (71.4%) samples were mosquito-infective and 20 (28.6%) were not. In infective samples, the expression level of Pfg377 ortholog gene was significantly higher than in the non-infective group (P<0.05). In infective samples, the expression level of Pfg377 ortholog gene at ≥100 copies/ml of blood cut-off point correlated with ≥10 oocysts/mosquito cut-off point of average oocyst numbers and with ≥50% cut-off point of per cent infected mosquitoes (Pearson's chi-square correlation, P=0.014 and P=0.026, respectively).

CONCLUSION

The cut-off point of the expression level of Pfg377 ortholog gene could be used to predict the infectiousness of P. vivax gametocytes leading to mosquito infection and parasite transmission in the field.