A Next-Generation Human Lymphatic Filariasis Vaccine Candidate, rHAXT, 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 rHAXT, we noticed that significant amounts of the antigen aggregated, resulting in the loss of purified vaccine antigens. Thus, this project aimed to create new rHAXT 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 rHAXT 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.