Immunogenicity and safety of respiratory syncytial virus subunit vaccine in seropositive children 18-36 months old.

Twenty-six children (aged 18-36 months) previously hospitalized for respiratory syncytial virus (RSV) infection were randomized to receive 50 micrograms of an RSV subunit vaccine composed primarily of F glycoprotein or saline placebo by intramuscular injection. Serum was obtained at entry and at 1 and 6 months after vaccination for detection of antibody to F glycoprotein and G glycoprotein of subtypes A (Ga) or B (Gb) and of neutralizing antibody (nAb). At 1 month, by comparing the baseline values, vaccinees had statistically significant increases in geometric mean antibody titer (GMT) of more than fourfold to F (P = .0001), Ga (P = .0001), Gb (P = .003), and nAb (P = .009). No differences in GMT were observed between F protein vaccine and placebo recipients at entry, nor between placebo recipients at entry and 1 month. RSV infections were identified in 7 placebo recipients (4 by both viral identification and seroconversion, 3 by seroconversion alone). No vaccine recipient had RSV infection documented in the 6 months after vaccination (P = .003). There were no significant vaccine-related side effects, and no evidence of enhanced respiratory illnesses was observed. The subunit F protein vaccine appears safe and immunogenic and may prevent infection in healthy children primed by prior RSV infection.

Mucosal T cell distribution during infection with respiratory syncytial virus.

Groups of 12-week-old Balb/c mice were inoculated intranasally with respiratory syncytial virus (RSV) and sacrificed at regular intervals after infection. T lymphocyte subset distribution was determined in lung tissue, bronchoalveolar lavage (BAL), peripheral blood, and spleen by means of flow cytometry employing monoclonal antibodies against the T cell membrane antigens Thy1.2 (pan-T), Ly2 (CD8), and L3T4 (CD4). Thy1.2+ cells increased in the lung from 35.4% of total lymphocytes before infection to 47.6% on day 7 after infection. This increase was largely accounted for by an increase in Ly2+ cells, which manifested a rise from 7.8% preinfection to 19.8% on day 7. The level of L3T4+ cells remained constant (27.9% preinfection vs. 25.2% on day 7). The L3T4+/Ly2+ ratio in the lungs reached a nadir 7 days post infection (1.5 vs. 3.5 before infection). The total cell count in BAL increased more than tenfold during the first week after infection. At the same time Thy1.2+ cells in the BAL increased from 41.1% of total lymphocytes on day 1 to 85.3% on day 7. Ly2+ influx was the most important (5.8% on day 1 vs. 41.1% on day 7). L3T4+ cell levels increased from 17.2% on day 1 to 40.1% on day 7. RSV-specific lymphocyte transformation was observed in BAL and blood but not in the lung tissue and spleen on day 7 postinfection. The disappearance of infectious virus in the lung correlated directly to the peak appearance of Ly2+ T cells in the lung tissue and BAL.