UNILATERAL NASAL INFECTION OF COTTON RATS WITH RESPIRATORY SYNCYTIAL VIRUS ALLOWS ASSESSMENT OF LOCAL AND SYSTEMIC IMMUNITY

An in vivo model for the study of local and systemic effecters of immu nity to respiratory syncytial virus (RSV) is described. Cotton rats (S igmodon fulviventer) inoculated in one nostril with a small volume (2 mu l) of virus suspension contracted a unilateral nasal infection whic h did not extend to the contralateral nasal turbinates, nor to the lun gs. Immunity to subsequent RSV challenge could be induced by small pri ming doses (<10 p.f.u. per animal), but was dependent upon viral repli cation, as virus inactivated by UV light was not immunogenic. Immunity occurred in the absence of detectable neutralizing serum antibody. Th e onset of resistance to viral challenge occurred simultaneously in ip silateral nasal, contralateral nasal and pulmonary tissues. However, l ow levels of transient viral replication occurred in contralateral nas al turbinates and in lungs following virus challenge, thus indicating that local components of immunity acting at the ipsilateral site of in fection were more effective than systemic components acting at the oth er sites. Further evidence is provided to suggest that three types of immunological effecters local, persistent systemic and transient syste mic-participate in the immune response to RSV infection.