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Voltage-Gated Sodium Channel Polymorphism and Metabolic Resistance in Pyrethroid-Resistant Aedes aegypti from Brazil

The nature of pyrethroid resistance in Aedes aegypti Brazilian populations was investigated. Quantification of enzymes related to metabolic resistance in two distinct populations, located in the Northeast and Southeast regions, revealed increases in Glutathione-S-transferase (GST) and Esterase levels. Additionally, polymorphism was found in the IIS6 region of Ae. aegypti voltage-gated sodium channel (AaNa_V), the pyrethroid target site. Sequences were classified in two haplotype groups, A and B, according to the size of the intron in that region. Rockefeller, a susceptible control lineage, contains only B sequences. In field populations, some A sequences present a substitution in the 1011 site (Ile/Met). When resistant and susceptible individuals were compared, the frequency of both A (with the Met mutation) and B sequences were slightly increased in resistant specimens. The involvement of the AaNa_V polymorphism in pyrethroid resistance and the metabolic mechanisms that lead to potential cross-resistance between organophosphate and pyrethroids are discussed.

Received November 27, 2008. Accepted for publication March 10, 2009.

Acknowledgments: We are grateful to Secretaria de Vigilância em Saúde (SVS) for the intermediation in the collections of Aedes aegypti eggs in the localities here studied and to Ricardo Lourenço de Oliveira from the Laboratório de Transmissores de Hematozoários/ IOC/FIOCRUZ for the donation of Aedes albopictus and Aedes fluviatilis specimens. We also thank José Bento Pereira Lima for bio-assays assistance, Priscila Fernandes Medeiros Viana and Isabela Reis Montella de Carvalho for the assistance in the colorimetrical biochemical assays. We are grateful to be able to count on the collaboration of the Plataforma Genômica - Seqüenciamento de DNA/PDTIS-FIOCRUZ. Finally, we thank the English revision performed by Mitchell Raymond Lishon, native of Chicago, IL, USA-UCLA, 1969.

Financial support: This work was supported by Secretaria de Vigilância em Saúde/Ministério da Saúde, Programa de Desenvolvimento e Inovação Tecnológica em Saúde Pública/Fundação Oswaldo Cruz, Vice-Presidência de Serviços de Referência e Ambiente/Fundação Oswaldo Cruz, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Financiadora de Estudos e Projetos do Rio de Janeiro, and the Howard Hughes Medical Institute.

^* Address correspondence to Denise Valle, Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz, FIOCRUZ, Av. Brasil 4365, Rio de Janeiro-RJ, CEP: 2104-900, Brazil. E-mail: dvalle{at}ioc.fiocruz.br

Authors’ addresses: Ademir Jesus Martins, Jutta Gerlinde Birgitt Linss, and Denise Valle, Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz – FIOCRUZ, Av. Brasil 4365, Rio de Janeiro-RJ, 2104-900, Brazil, Tel: +55-21-2580-6598, and Laboratório de Entomologia, Instituto de Biologia do Exército, Rua Francisco Manuel 102 Benfica, Rio de Janeiro-RJ, 20911-270, Brazil, Tel: +55-21-3895-2247, E-mails: ademirjr{at}ioc.fiocruz.br, jlinss{at}ioc.fiocruz.br, and dvalle{at}ioc.fiocruz.br. Rachel Mazzei Moura de Andrade Lins and Alexandre Afranio Peixoto, Laboratório de Biologia Molecular de Insetos, Instituto Oswaldo Cruz – FIOCRUZ, Av. Brasil 4365, Rio de Janeiro-RJ, 2104-900, Brazil, Tel: +55-21-3865-8231, E-mails: rlins{at}ioc.fiocruz.br and apeixoto{at}fiocruz.br.