Evaluation of the Live-Attenuated Intranasal Respiratory Syncytial Virus (RSV) Vaccine RSV/6120/ΔNS2/1030s in RSV-Seronegative Young Children
Ruth A. Karron, Cindy Luongo, Suzanne Woods, Jennifer Oliva, Peter L. Collins, Ursula J. Buchholz, the RSVPed Team, Milena Gatto, Tina Ghasri, Amanda Gormley, Kristi Herbert, Maria Jordan, Karen Loehr, Jason Morsell, Jocelyn San Mateo, Elizabeth Schappell, Khadija Smith, Paula Soro, Kimberli Wanionek, Cathleen Weadon
Abstract
BACKGROUND: Respiratory syncytial virus (RSV) is the leading cause of pediatric lower respiratory illness (LRI) and a vaccine for immunization of children is needed. RSV/6120/ΔNS2/1030s is a cDNA-derived live-vaccine candidate attenuated by deletion of the interferon antagonist NS2 gene and the genetically stabilized 1030s missense polymerase mutation in the polymerase, conferring temperature sensitivity. METHODS: A single intranasal dose of RSV/6120/ΔNS2/1030s was evaluated in a double-blind, placebo-controlled trial (vaccine to placebo ratio, 2:1) at 105.7 plaque-forming units (PFU) in 15 RSV-seropositive 12- to 59-month-old children, and at 105 PFU in 30 RSV-seronegative 6- to 24-month-old children. RESULTS: RSV/6120/ΔNS2/1030s infected 100% of RSV-seronegative vaccinees and was immunogenic (geometric mean RSV plaque-reduction neutralizing antibody titer [RSV-PRNT], 1:91) and genetically stable. Mild rhinorrhea was detected more frequently in vaccinees (18/20 vaccinees vs 4/10 placebo recipients, P = .007), and LRI occurred in 1 vaccinee during a period when only vaccine virus was detected. Following the RSV season, 5 of 16 vaccinees had ≥4-fold rises in RSV-PRNT with significantly higher titers than 4 of 10 placebo recipients with rises (1:1992 vs 1:274, P = .02). Thus, RSV/6120/ΔNS2/1030s primed for substantial anamnestic neutralizing antibody responses following naturally acquired RSV infection. CONCLUSIONS: RSV/6120/ΔNS2/1030s is immunogenic and genetically stable in RSV-seronegative children, but the frequency of rhinorrhea in vaccinees exceeded that in placebo recipients. CLINICAL TRIALS REGISTRATION: NCT03387137.