Broad Antibody and Cellular Immune Response from a Phase 2 Clinical Trial with a Novel Multivalent Poxvirus Based RSV Vaccine

Abstract

Background

Respiratory syncytial virus (RSV) is a major cause of severe respiratory disease in young children and the elderly. Protective immunity is not generated after repeated infections, but vaccination may hopefully prove effective.

Methods

This phase 2 clinical study investigated a multivalent RSV vaccine (MVA-BN®-RSV) designed to induce broad antibody and cellular immune responses by encoding RSV surface proteins F, G (for both A and B subtypes), and internal antigens (M2, N). This study evaluated the immune response in adults ≥55 years to identify the optimal MVA-BN-RSV dose and vaccination schedule.

Results

A single dose increased the levels of neutralizing (PRNT to RSV A and B) and total (IgG and IgA ELISA) antibodies (1.6 to 3.4-fold increase from baseline) and induced a broad Th1-biased cellular immune response (IFN-γ ELISPOT) to all 5 vaccine inserts (5.4 to 9.7-fold increases). Antibody responses remained above baseline for 6 months. A 12-month booster dose elicited a booster effect in antibody and T cell responses (up to 2.8-fold from pre-boost levels). No drug-related serious adverse events were reported.

Conclusions

MVA-BN-RSV induces a broad immune response that persists at least 6 months and can be boosted at 12 months, without significant safety findings.

Clinical Trials Registration

NCT02873286