Ultrastructural analysis of the growth cycle of Chlamydia trachomatis in mouse cells treated with recombinant human alpha-interferons.

The effect of two recombinant human hybrid interferons (IFNs), IFN-alpha AD (BglII) and IFN-alpha DA (BglII), on the growth cycle of Chlamydia trachomatis in a murine (McCoy) cell line was investigated. Ultrastructural analysis indicated that IFN-alpha AD inhibited the growth of chlamydia while IFN-alpha DA-treated cells did not significantly differ from the control monolayers. Treatment of the chlamydia-infected monolayers with IFN-alpha AD resulted in an inhibition in the transformation of elementary bodies to reticulate bodies with a consequent marked decrease in the number of chlamydia inclusions. Furthermore, chlamydial inclusions in the IFN-alpha AD-treated cells contained fewer and more immature chlamydial forms than the control or the IFN-alpha DA-treated cells. Secondary infection occurred in the IFN-alpha DA and in the control monolayer, but no such phenomena was detected in the IFN-alpha AD-treated McCoy cells indicating a loss of infectivity of the chlamydial organisms. From this study it can be concluded that purified recombinant human hybrid IFNs may exert an inhibitory effect on the growth cycle of C. trachomatis in a mouse cell line. This inhibition occurs primarily at the point of transformation from elementary to reticulate body.