Live-attenuated respiratory syncytial virus vaccine candidate with deletion of RNA synthesis regulatory protein M2-2 is highly immunogenic in children

Elizabeth J. McFarland, Ruth A. Karron, Petronella Muresan, Coleen K. Cunningham, Megan E. Valentine, Charlotte Perlowski, Bhagvanji Thumar, Devasena Gnanashanmugam, George Kelly Siberry, Elizabeth Schappell, Emily Barr, Vivian Rexroad, Ram Yogev, Stephen A. Spector, Mariam Aziz, Nehali Patel, Mikhaela Cielo, Cindy Luongo, Peter L. Collins, Ursula J. Buchholz

Research output: Contribution to journalArticlepeer-review


Background. Live respiratory syncytial virus (RSV) candidate vaccine LIDΔM2-2 is attenuated by deletion of the RSV RNA regulatory protein M2-2, resulting in upregulated viral gene transcription and antigen expression but reduced RNA replication. Methods. RSV-seronegative children ages 6–24 months received a single intranasal dose of 10 5 plaque forming units (PFU) of LIDΔM2-2 (n = 20) or placebo (n = 9) (NCT02237209, NCT02040831). RSV serum antibodies, vaccine infectivity, and reactogenicity were assessed. During the following RSV season, participants were monitored for respiratory illness and pre- and post-RSV season serum antibodies. Results. Vaccine virus was shed by 95% of vaccinees (median peak titers of 3.8 log 10 PFU/mL by quantitative culture and 6.3 log 10 copies/mL by PCR); 90% had ≥4-fold rise in serum neutralizing antibodies. Respiratory symptoms and fever were common in vaccine (95%) and placebo (78%). One vaccinee had grade 2 rhonchi concurrent with vaccine shedding, rhinovirus, and enterovirus. Eight of 19 vaccinees versus 2 of 9 placebo recipients had substantially increased RSV antibody titers after the RSV season without medically attended RSV disease, indicating anamnestic vaccine responses to wild-type RSV without significant illness. Conclusion. LIDΔM2-2 had excellent infectivity and immunogenicity, encouraging further study of vaccine candidates attenuated by M2-2 deletion. Clinical Trials Registration. NCT02237209, NCT02040831.

Original languageEnglish (US)
Pages (from-to)1347-1355
Number of pages9
JournalJournal of Infectious Diseases
Issue number9
StatePublished - May 1 2018


  • Immunogenicity
  • Live attenuated viral vaccine
  • Neutralizing antibodies
  • Pediatric RSV vaccine
  • RNA regulatory protein M2-2
  • Respiratory syncytial virus

ASJC Scopus subject areas

  • Immunology and Allergy
  • Infectious Diseases


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