PROTECTIVE EFFICACY OF MAJOR OUTER-MEMBRANE PROTEIN-SPECIFIC IMMUNOGLOBULIN-A (IGA) AND IGG MONOCLONAL-ANTIBODIES IN A MURINE MODEL OF CHLAMYDIA-TRACHOMATIS GENITAL-TRACT INFECTION

The protective efficacy of immunoglobulin A (IgA) and IgG monoclonal a ntibodies (MAbs) specific for the major outer membrane protein of Chla mydia trachomatis MoPn was evaluated in a murine genital tract infecti on model, MAbs were delivered into serum and vaginal secretions of nai ve mice by using the backpack hybridoma tumor system, and protective e fficacy was assessed over the first 8 days following challenge by quan titative determination of chlamydial recovery from cervicovaginal swab s, histopathological evaluation of genital tract tissue, and immunohis tochemical detection of chlamydial inclusions, IgA and Ige significant ly reduced the incidence of infection following vaginal challenge with 5 50% infectious doses, but such protection was overwhelmed by 10- an d 100-fold higher challenge doses. Both MAbs also consistently reduced vaginal shedding from infected animals with all three challenge doses compared with the negative control MAb, although the magnitude of thi s effect was marginal, Blinded pathological evaluation of genital trac t tissues at 8 days postinfection showed a significant reduction in th e severity of the inflammatory infiltrate in oviduct tissue of infecte d IgA- and IgG-treated animals. Immunohistochemical detection of chlam ydial inclusions revealed a marked reduction in the chlamydial burden of the oviduct epithelium; this finding is consistent with the reduced pathological changes observed in this tissue. These studies indicate that the presence of IgA or IgG MAbs specific to major outer membrane proteins has a marginal effect in preventing chlamydial colonization a nd shedding from the genital tract but has a more pronounced effect on ascending chlamydial infection and accompanying upper genital tract p athology.