Evaluation of Andes virus vaccine-derived human antibody for protection in Syrian hamsters: a passive transfer study using phase 1 trial sera

Background Andes virus (ANDV) causes severe hantavirus pulmonary syndrome and is uniquely capable of person-to-person transmission, with no licenced vaccines or therapeutics available. A Phase 1 trial (NCT03682107) demonstrated that an ANDV DNA vaccine targeting Gn/Gc envelope proteins elicits neutralising antibodies in humans. We evaluated whether these human antibodies protect against lethal disease in an animal model. Methods Day 197 sera from vaccinated human subjects were pooled, purified, and passively transferred to female Syrian hamsters one day prior to lethal ANDV challenge across two independent experiments. Controls included normal human IgG, PBS (negative controls), and SAB-400 (positive control). Neutralising antibody levels were quantified using pseudovirion neutralisation assays (PsVNA) and plaque reduction neutralisation tests (PRNT) to determine exploratory cutoff titres predicting survival. Findings Human antibodies from DNA-vaccinated subjects—unlike normal IgG—conferred significant protection against lethal ANDV challenge in both experiments. The exploratory cutoff titres predicting protection were determined to be 31–184 for PsVNA50 and 20–80 for PRNT50, depending on the analysis population and model parameters. Interpretation Vaccine-induced human antibodies are sufficient to protect against lethal ANDV infection in an established animal model. If confirmed, these results indicate that neutralising antibody titres could serve as a surrogate endpoint and correlate of protection for future hantavirus Gn/Gc-targeted vaccines.