Reviewing the effects of chlamydial immunizations on the host immune system — ASN Events

Reviewing the effects of chlamydial immunizations on the host immune system (#44)

David Lizarraga 1 2 , Scott Carver 1 , Peter Timms 2
  1. School of Natural Sciences, University of Tasmania, Sandy Bay, Tasmania, Australia
  2. School of Science and Engineering, University of Sunshine Coast, Sippy Downs, Queensland, Australia

Multiple host species can be targets of infection from bacterial species belonging to the Chlamydiaceae family, leading to devastating diseases such as conjunctivitis, pneumonia, and pelvic inflammatory disease. Antibiotics can alleviate symptoms of chlamydial infection, although many infections are asymptomatic making early detection difficult. Due to this, controlling the spread of chlamydial infection with antibiotics is a financially expensive undertaking that may not be practical for certain populations (e.g. underdeveloped countries or infected wildlife). Thus, developing a functional chlamydial vaccine has been a major focus of chlamydial research over the last six decades. Despite many reviews describing published chlamydial immunizations and their effects on host immune parameters (ex. immune cell, cytokine, and antibody abundance), there exists a need for a systematic comparison of these immunizations. Using the database Web of Science, we searched the literature for studies containing chlamydial immunizations and measurements of host parameters. The resulting 389 studies were further filtered based on the content of the abstract to exclude non-related studies. Within each study, immune parameter measurements from immunized and control groups were extracted and used to calculate an effect size. We applied statistical methods to compare effect sizes between and among studies. There exists an increase in the number of published chlamydial immunization studies, particularly in the last 20 years. Not surprisingly, our study identifies mice as the host most commonly used for chlamydial immunization experiments. After averaging the effect sizes of immune parameters, we found statistically trending decreased chlamydial loads and increased immunoglobulin G (IgG) antibodies after immunization. Preliminary results suggest the average abundance of interferon gamma, IgA, IgG1, and IgG2a were equivocal after immunization. Additionally, some immune parameters have an asymmetrical distribution of effect sizes suggestive of publication bias. The results of our meta-analysis identify trends in chlamydial immunization research that will guide future studies aimed at developing a functional chlamydial vaccine.

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