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The newspaper of The Johns Hopkins University March 26, 2007 | Vol. 36 No. 27
Researchers' Malaria-Resistant Mosquitoes Thrive in Lab

By Tim Parsons
School of Public Health

Researchers at the Johns Hopkins Malaria Research Institute have determined that genetically engineered malaria-resistant mosquitoes fare better than their natural counterparts when fed malaria-infected blood. The results of their study, published March 19 in the online edition of the Proceedings of the National Academy of Sciences, indicated that genetically engineered (transgenic) mosquitoes lived longer and produced more eggs compared to wild-type mosquitoes.

The findings, the researchers said, are an important next step toward developing malaria control strategies using genetic modification of mosquitoes. Theoretically, mosquitoes resistant to malaria could be introduced into nature to replace malaria-carrying mosquitoes. To be successful, transgenic mosquitoes would need to produce more offspring and show lower mortality in order to replace wild-type mosquitoes. However, the researchers stressed that any potential malaria control strategy using transgenic mosquitoes would still require years of study.

For this study, Marcelo Jacobs-Lorena, a professor in the Bloomberg School of Public Health's W. Harry Feinstone Department of Molecular Microbiology and Immunology, and his JHMRI colleagues combined equal numbers of transgenic and wild-type mosquitoes and let them feed on malaria-infected mice. After nine generations, the transgenic mosquito population grew to 70 percent vs. 50 percent at the beginning of the experiment. According to the researchers, this fitness advantage arose because the transgenic mosquitoes had a higher survival rate and laid more eggs. They said any potential negative effects of a transgene may be overcome by the advantage conferred by not being infected with malaria parasites.

When fed noninfected blood, the transgenic mosquitoes showed no advantage over the wild-type mosquitoes. For malaria control, transgenic mosquitoes would need to overtake wild-type mosquitoes even when not exposed to malaria parasites, because only a small percentage of mosquitoes are exposed to malaria in the field.

The study, supported by funding from the National Institutes of Health and the Johns Hopkins Malaria Research Institute, was written by Mauro T. Marrelli, Chaoyang Li, Jason L. Rasgon and Jacobs-Lorena. Rasgon is also with the Bloomberg School's W. Harry Feinstone Department of Molecular Microbiology and Immunology. Marrelli is currently with the Universidade de Sao Paulo in Brazil, and Li is with Case Western Reserve University, Cleveland.


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