Recovery of human parainfluenza virus types one and two.

The ability to recover human parainfluenza virus types 1 and 2 (HPIV-1, 2) from infected individuals has been highly variable. During the autumn of 1991, 158 nasal wash specimens collected from children with lower respiratory symptoms were split and cultured independently at two laboratories using different tissue culture techniques. Immunofluorescent antibody (IFA) and hemadsorption (HAd) assays were compared for their speed and efficiency in viral detection. 45 isolates [HPIV-1 (17) and HPIV-2 (28)] were recovered by one laboratory and only one (HPIV-2) by the other. IFA was the most sensitive assay detecting 87% of HPIV-1 and 70% of HPIV-2 by the fourth day of culture. HAd assay detected 87% of HPIV-1 isolates by the time they were positive by IFA, but only 35% of the HPIV-2 isolates. Significant methodologic differences between laboratories were then compared simultaneously for effect on virus recovery from culture positive frozen clinical specimens. Recovery of 100% of the isolates was achieved. Factors that contributed to differences in recovery of HPIV-1 and 2 were: (1) primary African green monkey (AGMK) cells were inferior to cynomolgus monkey kidney or LLC-MK2 cells, (2) addition of trypsin to culture medium for AGMK and LLC-MK2 cells enhanced recovery, (3) use of IFA was essential for rapid detection of HPIV-2, and (4) use of microtiter plate culture without specimen dilution enhanced virus recovery. A survey of clinical virology laboratories demonstrated considerable variability in the use of these techniques for routine respiratory virus culture.