ISOLATION OF A SUBSTANCE FROM THE MOSQUITO THAT ACTIVATES PLASMODIUM FERTILIZATION

We have isolated a small, heat stabile, hydrophilic molecule from the gut lumen of unfed, female Anopheles stephensi that is a potent induce r of gametogenesis in Plasmodium falciparum and P. gallinaceum al a hy drogen ion concentration, pH 7.4, that normally suppresses activation. This gamete activation factor (GAF) was purified using reverse phase high performance liquid chromatography and determined to have a major ion m/z of 206.1 by low resolution electrospray mass spectrometry. The molecule, which was also found in the heads of both female and male A . stephensi, absorbed light in the ultraviolet region at three maxima (lambda(max) = 213, 245 and 350 nm); the 245/350 nm absorbance ratio w as 7.0. The structure of the molecule and its normal function in the m osquito are not yet known, but in a sample of diverse insect species, extracts from those that feed on blood were bioactive. We propose that GAF is the previously observed malaria exflagellation factor (MEF). ( C) 1997 Elsevier Science B.V.