Immune Responses Induced by chlamydial Polymorphic Membrane Protein C formulated with probiotic Lactobacillus rhamnosus as an Adjuvant in Conjunctival Immunization

Abstract

Purpose : Our strategy in designing an efficient vaccine against Chlamydia trachomatis (Ct) relies on the assumptions that the subunit vaccine is based on proteins involved in the very first contact of Ct and host-cell, the chosen route via the ocular mucosa mimics the natural infection, and its application is needle-free and safe. We evaluated the immunogenicity of N-terminal portion of Ct polymorphic membrane protein C, involved in Ct-host cell interaction, when applied via the ocular mucosa; and examined the adjuvantic influence of Lactobacillus rahmnosus (LB) on the characteristics of the promoted immune response in a BALB/c mouse model system.

Methods : Mice were immunized via the conjunctiva with N-PmpC alone (N-PmpC/PBS), and N-PmpC mixed LB (N-PmpC/1x10⁶ CFU/ml/PBS). Concentration of N-PmpC in all vaccines prepared for the conjunctival administration was 1.5 mg/ml and each mouse was immunized with 15 mg N-PmpC in 10 ml (5 ml per eye administered). Detection of PmpC-specific and CtB-specific immunoglobulins in mouse sera and tears was done by the ELISA. Phenotyping of lymphocytes was done by flow cytometry. The statistical significance of the observed differences was evaluated using 1-Way Repeated Measures ANOVA. A probability (P) value of 0.05 was set as a limit of significance (software: ORIGIN 8.0).

Results : Ocular immunization with N-PmpC alone and in combination with LB was well tolerated in all animals. No signs of toxicity and pathology were observed. N-PmpC applied via the conjunctiva in combination with LB stimulated the production of specific IgA (p<0.05) and IgG (p<0.005) at both local and systemic level that was significantly enhanced in comparison with N-PmpC alone. In addition, N-PmpC mixed with LB initiated a T cell response characterized by the Th1 skewing and a rise of the effector CD8+ T cells and Tregs (p<0.05).

Conclusions : Conjunctival application of a chlamydial specific subunit antigen combined with a particulated carrier induced significant humoral and cellular immune responses. Further studies are needed to optimize relevant antigen and adjuvant combinations.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.