Use of HL cells for improved isolation and passage of Chlamydia pneumoniae.

We compared growth of the recently discovered respiratory pathogen Chlamydia pneumoniae in McCoy, HeLa 229, BHK-21, and HL cells. When cells were not pretreated with DEAE-dextran, HL cells had significantly higher mean numbers of inclusion-forming units (IFUs) on initial inoculation than the other cell lines. When cells were pretreated with DEAE-dextran, HeLa 229 and HL cells had equivalent mean numbers of IFUs on initial inoculation. HL cells had strikingly higher mean numbers of IFUs in passage than HeLa 229, BHK-21, or McCoy cells. In addition, HL cells did not require pretreatment with DEAE-dextran and could be used from 2 to 4 days after seeding. We conclude that HL cells are an excellent cell culture system for laboratory propagation of C. pneumoniae and may be a more sensitive cell line for initial isolation.