Failure of in vitro differentiation of Plasmodium falciparum gametocytes into ookinetes arises because of poor gamete fertilisation

Abstract

Keywords 22Plasmodium falciparum; Plasmodium berghei; malaria; ookinete; transmission. 24not peer-reviewed) is the author/funder. All rights reserved. No reuse allowed without permission.The copyright holder for this preprint (which was . http://dx.doi.org/10.1101/216721 doi: bioRxiv preprint first posted online Nov. 10, 2017; Note: Supplementary data associated with this article

Critical Steps of Plasmodium falciparum Ookinete Maturation

“…The synchronous comparison of in vivo and in vitro ookinete maturation confirmed that P. falciparum gamete fertilization is very inefficient in vitro (Delves et al, 2017) (Graphical Abstract).…”

“…To better characterize the post-fertilization events, several studies attempted to establish P. falciparum ookinete cultures in vitro (Carter et al, 1987;Warburg and Schneider, 1993;Bounkewa et al, 2010;Ghosh et al, 2010;Delves et al, 2017). While such cultures were successful for the rodent malaria parasite Plasmodium berghei (Janse et al, 1985;Sinden et al, 1985), the efficiency of P. falciparum conversion from roundshaped parasites to mature ookinetes is surprisingly low (0.45 to 16%) as compared to the estimated 50% efficiency in vivo (Carter et al, 1987;Bounkewa et al, 2010;Delves et al, 2017). The poor efficiency of P. falciparum gamete fertilization was identified as a major obstacle to efficient ookinete production in vitro (Ghosh et al, 2010;Delves et al, 2017).…”

“…While such cultures were successful for the rodent malaria parasite Plasmodium berghei (Janse et al, 1985;Sinden et al, 1985), the efficiency of P. falciparum conversion from roundshaped parasites to mature ookinetes is surprisingly low (0.45 to 16%) as compared to the estimated 50% efficiency in vivo (Carter et al, 1987;Bounkewa et al, 2010;Delves et al, 2017). The poor efficiency of P. falciparum gamete fertilization was identified as a major obstacle to efficient ookinete production in vitro (Ghosh et al, 2010;Delves et al, 2017). As the factors that promote fertilization in vivo remained obscure, a series of culture conditions (lipids, glucose, mosquito pupal extract, and red blood cell lysate additives, variations in hematocrit, pH, and gas; etc.)…”

“…As the factors that promote fertilization in vivo remained obscure, a series of culture conditions (lipids, glucose, mosquito pupal extract, and red blood cell lysate additives, variations in hematocrit, pH, and gas; etc.) were tested to rescue the block in fertilization, albeit without success (Ghosh et al, 2010;Delves et al, 2017).…”

“…The drawback of this classification was the unspecific basis of the Giemsa staining, which could not distinguish between residual non-activated gametocytes, developmentally blocked degenerated parasites, and mature ookinetes. Application of monoclonal antibodies that bound the zygote/ookinete surface antigen Pfs25 and/or the ookinete-specific intracellular enzyme chitinase helped the identification of mature ookinetes (Carter et al, 1987;Bounkewa et al, 2010;Ghosh et al, 2010;Delves et al, 2017). However, the antibodies were used only to count the mature ookinetes at a late time point or at the very beginning and very end of the process, thereby preventing a faithful reconstruction of the ookinete maturation stages.…”