RAPID DETECTION OF PARAINFLUENZA VIRUS TYPE-3 RNA IN RESPIRATORY SPECIMENS - USE OF REVERSE TRANSCRIPTION-PCR-ENZYME IMMUNOASSAY

Parainfluenza virus type 3 (PIV-3), an important lower respiratory tra ct pathogen in young children and immunocompromised individuals, may b e underdiagnosed because of the insensitivity of available culturing s ystems and delay in identification of virus in cell culture. We develo ped a reverse transcription-PCR-enzyme immunoassay (RT-PCR-EIA) for PI V-3, using primers specific for a highly conserved region of the hemag glutinin-neuraminidase gene. Testing of nasal washes spiked with PIV-3 or other respiratory viruses showed that this assay detected seven st rains of PIV-3 but not other respiratory viruses. Of 103 respiratory t ract samples obtained from children experimentally infected with a liv e PIV-3 vaccine or naturally infected with wild-type PIV-3, 51 were po sitive by culture and 48 were positive by RT-PCR-EIA. Eleven of the cu lture-positive samples were negative by RT-PCR-EIA; however, none of t hese grew virus upon reinoculation into cell culture, indicating that virus was lost or was present at a very low titer. Eight of the cultur e-negative samples were positive by RT-PCR-EIA: two were obtained from a subject who was culture negative but had a serologic response to PI V-3, four were obtained 7 to 9 days after the first positive culture, and two were obtained 1 day prior to the first positive culture. Thus, this RT-PCR-EIA for PIV-3 is sensitive and specific and can detect vi ral RNA in samples from which virus cannot be cultivated. This assay c ould be used for diagnosis late in the course of PIV-3 infection and f or accurate detection of disease outbreaks.