Characterization of Plasmodium berghei Pbg37 as Both a Pre- and Postfertilization Antigen with Transmission-Blocking Potential

Abstract

Transmission-blocking vaccines (TBVs) interrupting malaria transmission are an integrated tool for malaria eradication. We characterized a sexual-stage-specific gene (PBANKA_060330) from and studied its potential for use as a TBV. This gene, referred to as, encodes a protein of 37 kDa with a signal peptide and multiple transmembrane domains and is preferentially expressed in gametocytes. A recombinant Pbg37 (rPbg37) protein targeting the N-terminal 63 amino acids (amino acids 26 to 88) expressed in bacteria elicited strong antibody responses in mice. Western blotting demonstrated Pbg37 expression in gametocytes, zygotes, and, to a lesser extent, ookinetes and its predominant association with the membranes of gametocytes. Indirect immunofluorescence assay showed an abundant surface localization of Pbg37 on gametes and zygotes but reduced amounts on retorts and ookinetes. Knockout of (Δ) led to a considerable reduction in gametocytemia, which translated into a ~92.1% decrease in the oocyst number in mosquitoes. Deletion of had a more substantial influence on the development and maturation of microgametocytes. As a result, the Δ lines exhibited a higher female/male gametocyte ratio, fewer mature male gametocytes, and defects in the exflagellation of mature microgametocytes. To test the transmission-blocking potential of Pbg37, an ookinete assay showed that the major inhibitory effects of anti-Pbg37 antiserum were on the exflagellation and fertilization processes. Direct feeding of mosquitoes on mice immunized with rPbg37 or a control protein showed that rPbg37-immunized and-infected mice had a significant reduction (49.1%) in oocyst density compared to the controls. The conservation of this gene in warrants further investigations in human malaria parasites.

Evaluation of Two Sexual-stage Antigens as Bivalent Transmission-blocking Vaccines in Rodent Malaria

“…The recombinant Pbg37 protein targeting the N-terminal 63 amino acids (aa) was able to elicit strong antibody responses with TBA. Consistent with it being a pre-fertilization antigen, the major inhibitory effects of the Pbg37 antisera were on the ex agellation and fertilization processes [25]. Similarly, antisera against the aa 45-245 fragment of PSOP25 also showed signi cant in vitro and in vivo TBA [26].…”

Population genomics reveals the expansion of highly inbred Plasmodium vivax lineages in the main malaria hotspot of Brazil

“…We characterized 189 high-diversity 1-kb windows across the genome that yielded the top 1% π values. Within these windows, we found genes encoding proteins involved in red blood cell invasion, such as the merozoite surface proteins (MSPs) and the apical membrane antigen 1 (AMA1), as well as the AP2 domain transcription factor AP2-O5 [ 36 ], the liver-specific protein 2 (LISP2), an early marker of liver stage development [ 37 ], and the sexual stage-specific protein G37 [ 38 ]. Members of some multigene families, such as plasmodium helical interspersed subtelomeric ( phist ) and cytoadherence linked asexual gene ( clag ), also mapped to domains with the highest π values ( Fig 2B ).…”

An MFS-Domain Protein Pb115 Plays a Critical Role in Gamete Fertilization of the Malaria Parasite Plasmodium berghei

“…On day 3 after infection, gametocytemia and the gametocyte sex ratio were determined by Giemsa-stained tail blood smears (Guttery et al, 2014). At least 100 mature gametocytes were quantified as males and females to determine the gametocyte sex ratio (Liu et al, 2018). Exflagellation centers of male gametocytes and male–female gametes interactions were quantified as previously described (Tewari et al, 2010).…”