CT694 and pgp3 as Serological Tools for Monitoring Trachoma Programs

Abstract

BackgroundDefining endpoints for trachoma programs can be a challenge as clinical signs of infection may persist in the absence of detectable bacteria. Antibody-based tests may provide an alternative testing strategy for surveillance during terminal phases of the program. Antibody-based assays, in particular ELISAs, have been shown to be useful to document C. trachomatis genital infections, but have not been explored extensively for ocular C. trachomatis infections.Methodology/Principal FindingsAn antibody-based multiplex assay was used to test two C. trachomatis antigens, pgp3 and CT694, for detection of trachoma antibodies in bloodspots from Tanzanian children (n = 160) collected after multiple rounds of mass azithromycin treatment. Using samples from C. trachomatis-positive (by PCR) children from Tanzania (n = 11) and control sera from a non-endemic group of U.S. children (n = 122), IgG responses to both pgp3 and CT694 were determined to be 91% sensitive and 98% specific. Antibody responses of Tanzanian children were analyzed with regard to clinical trachoma, PCR positivity, and age. In general, children with more intense ocular pathology (TF/TI = 2 or most severe) had a higher median antibody response to pgp3 (p = 0.0041) and CT694 (p = 0.0282) than those with normal exams (TF/TI = 0). However, 44% of children with no ocular pathology tested positive for antibody, suggesting prior infection. The median titer of antibody responses for children less than three years of age was significantly lower than those of older children. (p<0.0001 for both antigens).Conclusions/SignificanceThe antibody-based multiplex assay is a sensitive and specific additional tool for evaluating trachoma transmission. The assay can also be expanded to include antigens representing different diseases, allowing for a robust assay for monitoring across NTD programs.

Plasmid-Encoded Pgp3 Is a Major Virulence Factor for Chlamydia muridarum To Induce Hydrosalpinx in Mice

“…Since chlamydiae can complete their biosynthesis inside the inclusion, any chlamydial proteins that are secreted outside the inclusion may be used by chlamydial organisms as virulence factors for interaction with the infected host. Second, Pgp3 is an immunodominant antigen in women who have acquired chlamydial infection via either the genital tract (42,43) or the ocular route (38,44). In general, chlamydia-secreted proteins are likely to be more immunogenic (43).…”

Tetanus Immunity Gaps in Children 5–14 Years and Men ≥ 15 Years of Age Revealed by Integrated Disease Serosurveillance in Kenya, Tanzania, and Mozambique

“…Depending on the country, serum was prepared from whole blood by centrifugation, or serum was eluted from DBS as previously described. 13,14 TT (Massachusetts Biologic Laboratories, Boston, MA) was coupled to SeroMap microspheres (Luminex Corp., Austin, TX) at the Centers for Disease Control and Prevention (CDC) with 12.5 μg of toxoid per 12.5 × 10 6 beads in buffer containing 50 mM 2-(N-morpholino) ethanesulfonic acid and 0.85% NaCl at pH 5.0, as previously described. 13,15 Serum samples were diluted 1:400 and assayed in duplicate for IgG (along with control sera) against multiple bacterial, viral, and parasitic disease antigens at CDC in Atlanta, GA, or the Kenya Medical Research Institute (KEMRI) in Nairobi, Kenya, using the conditions previously described.…”

Clinical signs of trachoma are prevalent among Solomon Islanders who have no persistent markers of prior infection with Chlamydia trachomatis

“…The first was an enzyme-linked immunosorbent assay (ELISA) assay that measured antibodies against the Ct antigen Pgp3 5, 6 . This tool has been used to assess transmission of both urogenital 7 and ocular 8 infections, including the study on Kiritimati Island, where we showed that there were strong associations between Ct infection, TF and anti-Pgp3 antibody levels. We also observed a rapid increase in Pgp3 seroprevalence throughout childhood years in that population 4 .…”