Cd loop fusion enhances the immunogenicity and the potential transmission blocking activity of Plasmodium falciparum generative cell specific 1 (GCS1) antigen.

TBVs are suggested to inhibit parasite transmission from humans to Anopheles mosquitoes. For the transmission of Plasmodium parasite, a variety of factors are included in gametes fusion phase. In this step, conserved male-specific generative cell specific 1 antigen is necessary for fusion of cytoplasmic membranes of micro- and macro-gametocytes and zygot formation. The partial blocking activities of elicited antibodies against either the HAP2-GCS1 domain or the cd loop of this antigen have been recorded to hinder the transmission of Plasmodium species in Anopheles mid-gut. Thus, the objective of the present study was to investigate if the cd loop-fusion can enhance the quantity and quality of humoral and cellular immune responses against Plasmodium falciparum GCS1 in comparison to non-fusion antigen (without cd loop), in the adjuvanted and non-adjuvanted mouse groups. The immunogenicity of two constructs of P. falciparum generative cell specific 1 antigen, a fusion protein composed of cd loop and HAP2-GCS1 domain (cd-HAP) and another recombinant PfGCS1 containing solo HAP2-GCS1 domain (HAP2) were assessed to impede Plasmodium gametocytes integration before zygote formation. The antibodies profiling, titer, and avidity of induced antibodies were measured by the immunized mice sera, and the released cytokines (IL-5, TNF, and INF-γ) were analyzed in the supernatants of stimulated splenocytes. Furthermore, the inhibitory potency of the elicited antibodies against HAP2 and cd-HAP was measured during oocyst development by Standard Membrane Feeding Assay (SMFA). The comparative results in the present study showed the higher titer of IgG antibodies and IgG2a subclass, avidity, and transmission-reducing activity (TRA = 72.5 %) when mice were immunized by cd-HAP rather than HAP2. Moreover, our findings confirmed intensified Th1-directed immune responses in group 4 received cd-HAP/Poly(I:C). These findings declared the potential ability of cd loop fusion (cd-HAP) to upsurge humoral and cellular immune responses. However, the immune responses may switch to stronger Th1-type using alternative formulations. Explicitly, the cd-HAP-based vaccine may enhance the overall efficiency of immune responses and present a promising implementation in aiming malaria transmission.
Competing Interests: Declaration of competing interest The article entitled “Cd loop fusion enhances the immunogenicity and the potential transmission blocking activity of Plasmodium falciparum Generative Cell Specific 1 (GCS1) antigen” has not been previously published elsewhere in any language and is not currently under consideration by any other publication. The authors also declare that they contributed significantly to the review, i.e. drafting, critical revision of the article, and also approval of the version to be published.
(Copyright © 2024 Elsevier Inc. All rights reserved.)