Usefulness of bronchoalveolar lavage for diagnosis of acute and persistentrespiratory syncytial virus lung infections in guinea pigs

To investigate whether bronchoalveolar ravage (BAL) fluid specimens can be used to diagnose acute and persistent respiratory syncytial virus(RSV) lung infections In guinea pigs, we tested BAL fluid and lung tissue specimens f or evidence of viral infection, and compared BAL cytology between infected and uninfected animals. RSV-inoculated guinea pigs were studied during acut e bronchiolitis (days 3 and 7 postinoculation), convalescence (Day 14 posti noculation), and persistent infection (Days 28 and 60 postinoculation); and were compared to the sham-infected control animals. BAL and lung tissue sp ecimens were cultured for virus and tested by immunocytochemistry for viral protein. A reverse transcription polymerase chain reaction (RT-PGR) method was used to test for viral nucleic acid. Total and differential BAL cell c ounts were compared between RSV-inoculated and control animals on each stud y day. In BAL specimens, replicating RSV was isolated by culture in one out of fou r of the animals on Day 3 postinoculation; immunocytochemistry for RSV anti gens was positive in all virus-exposed animals from Days 3-14 postinoculati on, and viral nucleic acid was detected by RT-PCR in one-fourth of the anim als on Day 3 postinoculation. In contrast, replicating virus, viral antigen s, and viral nucleic acid were documented in lung tissues obtained from the same RSV-infected animals on all study days; BAL specimens of RSV-inoculat ed animals contained more eosinophils on all study days (two-tailed P value < 0.01) compared to the controls. The results of this animal study demonst rate that BAL fluid is not useful for diagnosis of persistent RSV infection . However, BAL fluid may be helpful for the documentation of acute RSV lung infection when immunocytochemistry may provide a more accurate test for vi rus detection than RT-PGR or viral culture. Pediatr Pulmonol. 1998; 26:396- 404. (C) 1998 Wiley-Liss, Inc.