HIV-1 does not significantly influence Chlamydia trachomatis serovar L2 replication in vitro

Individuals with lymphogranuloma venereum (LGV), caused by Chlamydia trachomatis serovar L2, are commonly co-infected with human immunodeficiency virus type 1 (HIV-1), for reasons that remain unknown. One hypothesis is that a biological synergy exists between the two pathogens. We tested this by characterising for the first time in vitro C. trachomatis L2 replication in the presence of HIV-1. The human epithelial cell-line, MAGI P4R5 was infected with C. trachomatis L2 and HIV-1 (MN strain). Co-infected cultures contained fewer and larger chlamydial inclusions, but the inclusions did not contain morphologically aberrant organisms. C. trachomatis remained infectious in the presence of HIV-1 and showed neither an alteration in genome accumulation, nor in the acumulation of ompA, euo or unprocessed 16S rRNA transcripts. However, omcB was slightly elevated. Taken together, these data indicate that HIV-1 co-infection did not significantly alter C. trachomatis replication and the association between HIV-1 and LGV is likely due to other factors that require further investigation. The fewer, larger inclusions observed in co-infected cultures probably result from the fusion of multiple inclusions in HIV-1 induced syncytia and indicate that C. trachomatis-host-cell interactions continue to function, despite considerable host-cell re-modelling.