• Vaccine Name: LID/ΔM2-2/1030s
• Target Pathogen: Human Respiratory Syncytial Virus
• Target Disease: Respiratory tract disease
• Manufacturer: Charles River Laboratories Malvern, PA
• Type: Live, attenuated vaccine
• Status: Clinical trial
• Host Species for Licensed Use: None
• M2-2 gene engineering:
  • Type: Recombinant protein preparation
  • Description: 241 deletion of RSV ribonucleic acid synthesis regulatory protein M2-2 (McFarland et al., 2020).
  • Detailed Gene Information: Click Here.
• Immunization Route: Intramuscular injection (i.m.)
• Description: The vaccine, LID/ΔM2-2/1030s, is a cDNA-derived version of RSV subgroup A, strain A2 with 241 nts deleted from the M2-2 ORF and the 3 potential translation initiation codons of the M2-2 ORF silenced (McFarland et al., 2020).

Human Response

• Host age: (Endt et al., 2022)Children 6-24 months
• Vaccination Protocol: (McFarland et al., 2020)Eligible children were RSV seronegative at screening, defined as having a complement-enhanced serum RSV 60% plaque reduction neutralizing titer. Respiratory syncytial virus-seronegative children ages 6–24 months received 1 intranasal dose of 105 plaque-forming units (PFU) of LID/ΔM2-2/1030s (n = 21) or placebo (n = 11). The RSV serum antibodies, vaccine shedding, and reactogenicity were assessed. During the following RSV season, medically attended acute respiratory illness (MAARI) and pre- and postsurveillance serum antibody titers were monitored.
• Challenge Protocol: (McFarland et al., 2020)The small sample size precludes firm estimates of rates of vaccine-associated events, infectivity, immunogenicity, and viral replication.
• Efficacy: (McFarland et al., 2020)Eighty-five percent of vaccinees shed LID/ΔM2-2/1030s vaccine (median peak nasal wash titers: 3.1 log10 PFU/mL by immunoplaque assay; 5.1 log10 copies/mL by reverse-transcription quantitative polymerase chain reaction) and had ≥4-fold rise in serum-neutralizing antibodies. Respiratory symptoms and fever were common (60% vaccinees and 27% placebo recipients). One vaccinee had grade 2 wheezing with rhinovirus but without concurrent LID/ΔM2-2/1030s shedding. Five of 19 vaccinees had ≥4-fold increases in antibody titers postsurveillance without RSV-MAARI, indicating anamnestic responses without significant illness after infection with community-acquired RSV.
• Description: The vaccine, LID/ΔM2-2/1030s, is a cDNA-derived version of RSV subgroup A, strain A2. The results showed that the LID/∆M2-2/1030s is a very attractive candidate for further development as a live attenuated in trans Al pediatric RSV vaccine.