A Next-Generation Human Lymphatic Filariasis Vaccine Candidate, rBmHAXT, for Clinical Development

This study was conducted to yield a robust and scalable manufacturing process for a candidate vaccine for human lymphatic filariasis (LF) - a tropical parasitic infection transmitted by mosquitoes. In previous studies, we demonstrated that removing an affinity purification tag from the fusion protein did not affect immunogenicity or vaccine efficacy. During scaled-up production of r Bm HAXT, we noticed that significant amounts of the antigen aggregated, resulting in the loss of purified vaccine antigens. Thus, this project aimed to create new r Bm HAXT forms more suitable for industrial-scale production while maintaining robust protection. We generated three different variants: one with all the cysteinyl residues mutated to serinyl residues (delta-Cys), a second one with a flexible glycine-serine linker inserted between each of the component antigens (GS), and finally, a third variant with a combination of both the cysteine deletion and the addition of linkers (delta-Cys GS). We then evaluated the immunogenicity and efficacy of each variant in a mouse model. We demonstrated that the delta-Cys mutant retained immunogenicity and vaccine efficacy similar to the parent tag-free r Bm HAXT protein. We also evaluated the proteins in an accelerated stability study at five (5) different temperatures (-80°C, -20°C, 4°C, 25°C, and 40°C). We concluded that all preparations were stable at 4°C, and the delta-Cys variant was stable even at 25°C up to the completion of the study (6 weeks). In addition to improved stability, the delta-Cys protein exhibited reduced aggregation and equivalent potency in mice and, therefore, is an optimal candidate for progression to cGMP manufacturing and human clinical trials as a vaccine for lymphatic filariasis.