During studies on experimental infection in adult volunteers with respiratory syncitial (RS) virus( 1.2 ) grown in cultures of rhesus monkey kidney cells it was found that the RS virus pool prepared for use in this work was contaminated with vacuolating virus ( SY4,,) ( 3 ) . This paper describes inoculation by the respiratory route of volunteers with the dually infected inoculum and also inoculation with the dually infected material in which RS component had been neutralized by addition of RS antiserum, reports recovery of SV,,, from throat swab specimens obtained from inoculated volunteers, and presents serologic data indicating that SIT4,,, when administered by the respiratory route. evokes subclinical infection in man.Materials and irxthocls. Volunteers. Thirty-five test and 11 control subjects employed were male volunteers between the ages of 21 and 35 years. All were given physical examinations including chest roentgenograms. blood and urine tests before and periodically after exposure to test preparations. For several dzys before and for 2 weeks after inwulation, all volunteers were isolated. usually 3 to a room in the Clinical Center a t the Nat. Inst. of Health, under careful medical surveillance; thereafter, they were available for follow-up studies on an out patient basis.Virus and viriis administration. SVd0 virus employed in the laboratory aspects of the current study was isolated as a contaminant from a pool of RS virus which had been grown in bottle cultures of rhesus monkey kidney cells. Preparation of the RS virus pool is described in detail elsewhere(4). Briefly. 6 to 11 days after inoculation of RS virus, at a time when specific RS cytopathogenic changes were noted in about 50% of the cells in an inoculated culture, the infected cultures were harvested. and the supernatant fluid obtained following low speed cerltrifugation was filtered through a 830 mp gradacol membrane and the filtrate stored in convenient amounts a t -60°C until used. This material contained in addition to 320 TCIDZo of RS virus, 5000 TCIDZo of SVA0 virus per ml as measured in grivet kidney cell cultures. It may be noted that RS virus unlike SVM does not readily produce cytopathogenic changes in grivet kidney cell cultures. In one volunteer experiment, the RS component af a sample of the dually infected inwulum was neutralized by addition of undiluted guinea pig serum containing RS antibody and in another sample of the infected material the SV,,, was neutralized by use of guinea pig serum containing SV,,, antibody. Infectivity titrations performed before and after addition of the antisera showed that neutralization of the homologous agent was accomplished with no appreciable loss of heterologous virus.Infected and control (Hanks' BSS) inucula were administered to volunteers by the respiratory route. Approximately 1 ml of the original RS-SIT,,, inoculum was nebulized in,to the nose and mouth, and with the volunteer in a prone position, an additional 0.5 ml was drcpped into each nostril. The nose was massaged between thumb and ...
