A recombinant respiratory syncytial virus (RSV) fusion glycoprotein candidate vaccine (RSV-PreF) produced in Chinese hamster ovary cells was designed for vaccination of pregnant women in order to protect neonates against RSV illness by trans-placental antibody transfer. In pure RSV-PreF antigen material, traces of hamster neogenin (haNEO1), a host-cell protein, were found. Given the strong amino-acid sequence similarity between haNEO1 and human neogenin (huNEO1), there was a concern that possible vaccine-induced anti-neogenin immunity may impair huNEO1 function in the mother or fetus. Applying RSV-PreF formulations consisting of various antigen dosages, with/without aluminum-hydroxide adjuvant, antimicrobial anti-huNEO 1 IgGs were evaluated in a sero immunising immuno sorbial test from rabbits and study participants. Four injections delivered in rabbits at 14-day intervals led to the use of a high-dose group following three injections of HuNEO1 specific IgG responses in antigen-dose and adjuvant-dependent manner. No vaccine-induced anti-huNEO1 IgG responses were found in people after single immunisation because in the pre-vaccination levels, the values in vaccine and control groups had varied to 90 to 360 days post-vaccination levels.

Despite identifying vaccination-induced huNEO1-specific responses in rabbits, researchers found no indication that the candidate vaccine caused anti-huNEO1 immunity in human adults. Despite this, the antigen purification method was improved, and haNEO1-reduced vaccinations were utilised in a second Phase 2 study including 400 non-pregnant women, in which no vaccine-induced anti-huNEO1 reactions were found.

Reference: https://www.tandfonline.com/doi/full/10.1080/21645515.2019.1693749