Experimental Respiratory Syncytial Virus Infection of Adults

Volunteers were inoculated with a low (102.7 pfu), or 200-fold higher dose (105.0 pfu) of respiratory syncytial virus (RSV). The low dose infected 100% of the men but did not produce illness; the level of virus replication and the magnitude of the subsequent antibody response were inversely correlated with the level of nasal secretory neutralizing antibody prior to infection. The high dose infected only 53% of the men (9 of 17); five of the infected men became ill. Two of the men who excreted virus apparently resisted experimental inoculation and acquired infection secondarily by contact with infected men. The differences in rates of infection between the two studies were minimized if only those men who had extensive infection (virus excretion τ; 102.5 pfu or significant antibody responses) were considered. Resistance to extensive infection in both studies, and resistance to illness in the second study, appeared to be correlated with high levels of nasal wash antibody, but not with the level of serum antibody.