Abstract Background Crimean-Congo haemorrhagic fever virus (CCHFV) is a tick-borne pathogen that has a wide geographical range and has the potential to cause severe disease in those infected. There are no currently approved vaccine or therapeutics, so the development and assessment of new approaches are urgently required. Methods A polyclonal antibody based therapeutic was developed, based on immunisation of sheep with the major glycoprotein antigens from CCHFV. Along with purified IgG from hyperimmune sera, fragmentation of the F(ab’)2 region was also performed. The pharmacokinetic properties were assessed in mice and efficacy ascertained in a live CCHFV challenge model. Results Candidate polyclonal antibody-based therapies were developed, demonstrating strong binding to the CCHFV envelope glycoprotein and neutralising activity. The ovine whole immunoglobulin G (IgG) demonstrated stability post-delivery compared to a rapid reduction of the F(ab’)2 fragment in the circulation. Efficacy testing when delivered either as a single dose before challenge or daily dosing for 7 days starting on the day of challenge showed no demonstrable evidence of protection against infection. Conclusions Despite protection observed from vaccine candidates using the CCHFV glycoprotein as antigen and administration of convalescent sera, the ovine antibody-based therapeutics did not confer similar efficacious effects in the mouse preclinical model.
Kennedy et al. (Tue,) studied this question.