Immortalized Human Endocervical Epithelial Cells-HPV E6/E7 (A2EN)

In vivo Effect of CTH522 Specific Antibodies

Developing an effective Chlamydia vaccine requires translating protective pre-clinical immune signatures to humans, yet cross-species validation remains challenging. Olsen et al. aimed to comparatively characterize the CTH522/CAF®01 vaccine in female mice and humans to identify translatable immune signatures.

To demonstrate antibody-mediated protection in the genital tract, in vivo neutralization was assessed. Mice were infected with C. trachomatis serovar D (SvD) precoated with pools of CTH522-specific neutralizing antibodies from mice or humans (Fig. 1a). Serum pools were incubated with SvD and confirmed for neutralization in vitro (Fig. 1b) before intravaginal (i.vag.) inoculation into C3H/HeN mice (Fig. 1c). Serum was diluted 2- or 4-fold with the inoculum. Both mouse and human CTH522-specific serum pools significantly reduced inclusion-forming units (IFU) early in infection (PID 3 and PID 7).

To model human antibody effector function, the human immortalized endocervical cell line (End1/E6E7) was used in vitro and compared to the standard hamster kidney (HaK) cell line. Unlike HaK cells, End1/E6E7 more closely resembles endocervical epithelium. Most serum samples with SvD NT₅₀ > 200 in HaK cells also reduced SvD, E, F, and G infection in the endocervical cell line (Fig. 1d), confirming neutralization without Fc-receptor-mediated enhancement.