Delivery of a Chlamydial Adhesin N-PmpC Subunit Vaccine to the Ocular Mucosa Using Particulate Carriers.

Trachoma, caused by the intracellular bacterium Chlamydia trachomatis (Ct), remains the world's leading preventable infectious cause of blindness. Recent attempts to develop effective vaccines rely on modified chlamydial antigen delivery platforms. As the mechanisms engaged in the pathology of the disease are not fully understood, designing a subunit vaccine specific to chlamydial antigens could improve safety for human use. We propose the delivery of chlamydia-specific antigens to the ocular mucosa using particulate carriers, bacterial ghosts (BGs). We therefore characterized humoral and cellular immune responses after conjunctival and subcutaneous immunization with a N-terminal portion (amino acid 1-893) of the chlamydial polymorphic membrane protein C (PmpC) of Ct serovar B, expressed in probiotic Escherichia coli Nissle 1917 bacterial ghosts (EcN BGs) in BALB/c mice. Three immunizations were performed at two-week intervals, and the immune responses were evaluated two weeks after the final immunization in mice. In a guinea pig model of ocular infection animals were immunized in the same manner as the mice, and protection against challenge was assessed two weeks after the last immunization. N-PmpC was successfully expressed within BGs and delivery to the ocular mucosa was well tolerated without signs of inflammation. N-PmpC-specific mucosal IgA levels in tears yielded significantly increased levels in the group immunized via the conjunctiva compared with the subcutaneously immunized mice. Immunization with N-PmpC EcN BGs via both immunization routes prompted the establishment of an N-PmpC-specific IFNγ immune response. Immunization via the conjunctiva resulted in a decrease in intensity of the transitional inflammatory reaction in conjunctiva of challenged guinea pigs compared with subcutaneously and non-immunized animals. The delivery of the chlamydial subunit vaccine to the ocular mucosa using a particulate carrier, such as BGs, induced both humoral and cellular immune responses. Further investigations are needed to improve the immunization scheme and dosage.

Key protection factors against tetanus: Anti-tetanus toxin antibody affinity and its ability to prevent tetanus toxin - ganglioside interaction.

Antibodies capable to neutralize tetanus toxin (TeNT) are key factors in protection against tetanus disease. Although antibody-based therapeutics for treatment of tetanus exist on the market its production is tedious. Hence, the tetanus-specific antibodies preparation that could be easily produced in large scale in vitro would be beneficial. Monoclonal antibodies (MAbs) are considered for a long time as a reagent of choice, but the core drawback is how to select a MAb that would be safe in providing efficacious protection. In this study we have investigated the parameters crucial for a single MAb to be assigned as protective. Eight murine MAbs were characterized in vitro for their reactivity toward TeNT and assessed in vivo for protectiveness against TeNT intoxication. Correlation of in vitro and in vivo data has revealed that in vitro selection of MAb that is protective in vivo could be performed by a combination of two assays: the measurement of MAb affinity toward TeNT taking Ka 1 × 10(8) M(-1) as a threshold level, and the evaluation of its capability to prevent TeNT-ganglioside interaction. Single MAb could be taken into consideration as a potential therapeutic only if it has a capacity to completely inhibits TeNT-ganglioside complex formation.