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Infection and Immunity, January 2002, p. 102-106, Vol. 70, No. 1
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.70.1.102-106.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Fengwu Li, and Joseph M. Vinetz*
WHO Collaborating Center for Tropical Disease, Department of Pathology, University of Texas Medical Branch, Galveston, Texas 77555
Received 22 June 2001/ Returned for modification 27 August 2001/ Accepted 26 September 2001
The development of transmission-blocking vaccines is one approach to malaria control. To identify novel Plasmodium zygote- and ookinete-secreted proteins as targets of blocking malaria transmission, monoclonal antibodies (MAbs) were produced against parasite-secreted proteins found in Plasmodium gallinaceum ookinete culture supernatants. Four MAbs1A6, 2A5, 2B5, and 4B6were identified that bound to P. gallinaceum zygotes and ookinetes in diverse patterns in terms of spatial localization on parasites, time course of antigen expression, and Western immunoblot patterns. MAbs 2A5 and 4B6 recognized more than one protein band as detected by Western immunoblot of P. gallinaceum ookinete supernatants. Beginning at 0 h postfertilization, MAb 2A5 recognized a diverse set of antigens; at 10 h postfertilization, MAb 4B6 recognized several antigens as well. MAb 1A6 recognized a single
17-kDa protein, and 2B5 recognized a single
32-kDa protein at 15 h postfertilization. In membrane feeding assays to assess the effect of these MAbs on P. gallinaceum infectivity for Aedes aegypti mosquitoes, the addition of MAbs 1A6 and 2B5 to infectious blood meals significantly inhibited oocyst development in the mosquito midgut. In contrast, MAb 2A5 seemed to enhance infectivity. These results demonstrate that Plasmodium ookinetes secrete proteins (in addition to previously characterized chitinases) that may be targets for blocking malaria transmission. Future investigation of ookinete-secreted neutralization-sensitive molecules should provide valuable insight into mechanisms by which ookinetes exit the blood meal, penetrate and transverse the peritrophic matrix, and invade the mosquito midgut epithelium.
Present address: University of Texas School of Public Health, Houston, TX 77030.
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