Population genetic structure of the fibrinogen-related protein 1 (FREP1) in Iranian isolates of Anopheles stephensi as a promising mosquito-based malaria vaccine candidate

Background

Transmission Blocking Vaccines (TBVs) are critical for malaria eradication as they aim to interrupt the transmission cycle of Plasmodium parasites. However, the development of effective TBVs is challenged by the antigenic diversity of potential vaccine targets. This study investigates the fibrinogen-related protein 1 (frep1) gene, a promising candidate for TBVs, focusing on the genetic diversity of the frep1 gene and immunogenic potential in Anopheles stephensi from southern Iran.

Methods

Analysis of 30 An. stephensi isolates collected from three malaria-endemic cities was carried out using molecular amplification, sequencing, and bioinformatics tools. The haplotype and nucleotide diversity were assessed using the DnaSP, while predicted linear B-cell epitopes were evaluated through the ABCpred. Additionally, conformational epitopes were identified via DiscoTope analysis and visualized using the PyMOL. Furthermore, MHC II-peptide interactions were examined to evaluate the potential for effective immune responses.

Results

Seven distinct haplotypes of the frep1 domain were identified, with synonymous nucleotide variations indicating high genetic conservation. This conservation was complemented by the identification of 16 linear B-cell epitopes with high immunogenic scores (0.80–0.97). Conformational epitopes, prominently located at the N-terminus and C-terminus, were consistent across isolates. MHC II-binding analysis revealed peptides with strong affinities to prevalent HLA alleles in Iran, suggesting effective antigen presentation.

Conclusion

FREP1 demonstrates purifying selection, low genetic diversity and high immunogenic potential, highlighting the suitability of the protein as a TBV candidate. The presence of conserved epitopes and strong MHC II interactions supports the potential of this protein for inducing robust immune responses. However, regional haplotype diversity suggests that vaccine strategies may need to account for local variability. These findings underscore the promise of FREP1 for TBV development and emphasize the need for further validation in vivo.