Genetic polymorphisms in the glutamate-rich protein of Plasmodium falciparum field isolates from a malaria-endemic area of Brazil

Lilian Rose Pratt-Riccio,Claudio Tadeu Daniel-Ribeiro,Daiana De Souza Perce-Da-Silva,Dalma Maria Banic,Fatima Santos,Josue Da Costa Lima-Junior,Michael Theisen,Joseli De Oliveira-Ferreira

doi:10.1590/s0074-02762013000400022

Abstract

The genetic diversity displayed by Plasmodium falciparum, the most deadly Plasmodium species, is a significant obstacle for effective malaria vaccine development. In this study, we identified genetic polymorphisms in P. falciparum glutamate-rich protein (GLURP), which is currently being tested in clinical trials as a malaria vaccine candidate, from isolates found circulating in the Brazilian Amazon at variable transmission levels. The study was performed using samples collected in 1993 and 2008 from rural villages situated near Porto Velho, in the state of Rondônia. DNA was extracted from 126 P. falciparum-positive thick blood smears using the phenol-chloroform method and subjected to a nested polymerase chain reaction protocol with specific primers against two immunodominant regions of GLURP, R0 and R2. Only one R0 fragment and four variants of the R2 fragment were detected. No differences were observed between the two time points with regard to the frequencies of the fragment variants. Mixed infections were uncommon. Our results demonstrate conservation of GLURP-R0 and limited polymorphic variation of GLURP-R2 in P. falciparum isolates from individuals living in Porto Velho. This is an important finding, as genetic polymorphisms in B and T-cell epitopes could have implications for the immunological properties of the antigen.

Highlights

In low-income countries, less than 20% of residents live to the age of 70 and more than a third of all deaths occur in children under 15
It was recently shown that the antibodies produced in response to glutamate-rich protein (GLURP) in naturally exposed individuals can inhibit the in vitro growth of P. falciparum with or without cooperation from monocytes, suggesting that GLURP could play an important role in controlling parasitaemia (Pratt-Riccio et al 2011)
Our results showed limited polymorphic variation for Various glutamate-rich protein (GLURP) fragments amplified by nested polymerase chain reaction from Plasmodium falciparum isolates from Porto Velho, state of Rondônia (RO), Brazil

Summary

Introduction

In low-income countries, less than 20% of residents live to the age of 70 and more than a third of all deaths occur in children under 15. Reports on the genetic variation of P. falciparum have demonstrated that the differences in the number of alleles for each gene positively correlate with the degree of endemicity of the area. The population of Porto Velho sampled in this study is composed of natives and migrants from several non-endemic areas of Brazil that have lived in the region for 10 years or more.

Results

Conclusion