Safety and immunogenicity of an adjuvanted human onchocerciasis vaccine candidate, OvMANE1: preclinical evaluation in a mice model

Abstract

Objectives

Onchocerciasis, caused by the filarial worm Onchocerca volvulus, remains a major public health challenge because of the limitations of ivermectin-based control strategies, thereby highlighting the need for more innovative tools such as vaccines.

Methods

This study investigated the safety and immunogenicity of a novel multi-epitope chimeric antigen, OvMANE1 formulated with Freund's adjuvant, in BALB/c mice. Mice were immunised at three time points of 2-week intervals, with blood collected at each point to measure antibody levels and immune cells.

Results

Adjuvanted-OvMANE1 exhibited a promising safety profile, revealing neither any physical signs of toxicity nor behavioural abnormalities. Immunological assays showed significant increases in total IgG absorbance (OD 450 nm) after the first (P = 0.0260) and final booster doses (P = 0.026). Total IgG (P = 0.0086) and IgG1 (P = 0.0465) absorbances also increased significantly over the study period, suggesting sustained humoral immunity. Moreover, cellular responses were significantly enhanced, with elevated leucocyte count (P = 0.0190) and increased lymphocyte activity (P = 0.0397) observed in the adjuvanted-OvMANE1 group compared to the control. Indeed, total leucocytes increased progressively from Day 0 to Day 39, with significant differences recorded in the test group between doses: Days 0–14 (P = 0.0043) and Days 14–28 (P = 0.0079). The pronounced production of relevant antibodies and induction of cellular immunity is indicative of a mixed Th1/Th2 response and antibody-dependent cellular cytotoxicity (ADCC) targeting O. volvulus L3 and/or other larval stages of the parasite.

Conclusion

These results position OvMANE1 as a promising vaccine candidate against human onchocerciasis. However, further in vivo studies are needed to confirm and expand these findings.