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

PLoS One. 2015 Dec 11;10(12):e0144380. doi: 10.1371/journal.pone.0144380. eCollection 2015.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adhesins, Bacterial / immunology*
  • Animals
  • Blotting, Western
  • Cell Proliferation
  • Chlamydia trachomatis / immunology*
  • Conjunctiva / immunology
  • Disease Models, Animal
  • Drug Carriers / chemistry*
  • Epitopes
  • Escherichia coli / metabolism
  • Eye / immunology*
  • Eye / microbiology
  • Eye / pathology
  • Female
  • Guinea Pigs
  • Immunization
  • Immunoglobulin A / metabolism
  • Immunoglobulin G / blood
  • Injections, Subcutaneous
  • Interferon-gamma / metabolism
  • Interleukin-4 / metabolism
  • Mice, Inbred BALB C
  • Mucous Membrane / immunology*
  • Mucous Membrane / microbiology
  • Mucous Membrane / pathology
  • Particulate Matter / chemistry*
  • Recombinant Proteins / metabolism
  • Spleen / pathology
  • Tears / metabolism
  • Trachoma / immunology
  • Trachoma / microbiology
  • Trachoma / pathology
  • Trachoma / prevention & control
  • Vaccines, Subunit / immunology*

Substances

  • Adhesins, Bacterial
  • Drug Carriers
  • Epitopes
  • Immunoglobulin A
  • Immunoglobulin G
  • Particulate Matter
  • Recombinant Proteins
  • Vaccines, Subunit
  • Interleukin-4
  • Interferon-gamma

Grants and funding

This research was funded by the “Laura Bassi Centers of Expertise” Program of the Austrian Federal Ministry of Economy through the Austrian Research Promotion Agency (FFG Project Number: 822768) and was partly supported by the Ministry of Education, Science, and Technological Development of the Republic of Serbia (Grant Number 172049). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. BIRD-C provided support in the form of salaries for authors BM and WL, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.