Chlamydia pneumoniae-Induced IFN-Gamma Responses in Peripheral Blood Mononuclear Cells Increase Numbers of CD4+ but Not CD8+ T Effector Memory Cells

Abstract

Background

Chlamydia pneumoniae causes respiratory infection in adults and children. Previous studies in our laboratory identified significantly higher in vitro T lymphocyte responses to C. pneumoniae in children with asthma compared to healthy controls which may indicate the presence of T effector memory (TEM) lymphocytes.

Aim

In the present study, healthy subjects were screened for the presence of TEM cells and their cytokines. CCR7 negative effector TEMs may indicate persistent infection with C. pneumoniae.

Methods

Peripheral blood mononuclear cells (PBMC) (1×10⁶/mL) from adult non-asthmatic subjects were infected for 1h ± C. pneumoniae TW-183 at a multiplicity of infection (MOI) = 0.1 and cultured (48 hrs). Distributions of lymphocytes (CD4+, CD8+) and TEM cells (CD4+CCR7+CD45RA+CD154+, CD8+CCR7+CD45RA+CD154+) were determined. Levels of intracellular interleukin (IL)-2, IL-4, and interferon (IFN)-gamma were measured (flow microfluorimetry); IFN-gamma was measured in supernatants (ELISA).

Results

C. pneumoniae infection led to a decrease in numbers of CD8+ TEM and CD8+CD154+ cells; CD4+TEM and CD4+CD154+ cells did not change. Numbers of TEM cells (CD4+IL-2+, CD8+ IL-2+) also decreased. However, number of TEM cells (CD4+IL4-+, CD8+ IL-4+) and (CD4+ IFN-gamma+, CD8+IFN-gamma+) did not change. When stratified according to IFN-gamma+ status, numbers of CD4+ IL-2+ and CD4+IL-4+ TEMs increased; CD8+IL-2+ and CD8+ IL-4+ TEMs decreased.

Conclusion

C. pneumoniae-induced PBMC IFN-gamma+ responses increased numbers of CD4+ IL-2+ and CD4+IL-4+ TEM cells, while CD8+IL-2+ and CD8+IL-4+ TEMs decreased. Production of IFN-gamma by C. pneumoniae infected PBMC should be further studied as a biomarker of persistent infection in humans.

Keywords:

• C. pneumoniae
• T effector memory lymphocytes
• interleukin-2

Abbreviations

C. pneumoniae,Chlamydia pneumoniae; PBMC, peripheral blood mononuclear cells; TEM, T effector memory cell.

Data Sharing Statement

Upon request from authors.

Ethics Approval

This study was approved by the SUNY Downstate Medical Center Institutional Review Board (Brooklyn, NY) and human studies adhered to the World Medical Association Declaration of Helsinki. Written informed consent for participation and publication was obtained from all participants.

Consent to Participate

Written consent to participate was obtained.

Consent for Publication

Written consent for publication was obtained.

Acknowledgments

The abstract from this article was accepted for oral presentation at the annual AAAAI meeting March 2020 in Philadelphia, PA. The meeting was canceled due to the COVID-19 pandemic. The published abstract reference is listed below.

• Shidid S, Kohlhoff S, Norowitz Y, et al. Chlamydia pneumoniae decreases CD4+ and CD8+ T effector IL-2 responses in stimulated peripheral blood mononuclear cells in non-asthmatic subjects. J Allergy Clin Immunol 2020; 145(2): AB163.

Earlier pilot studies in our laboratory using similar methods was published as abstract and presented as poster presentation at the AAAAI/WAO Joint Congress meeting March 2018, Orlando, FL. The published abstract reference is listed below.

• Norowitz YM, Kohlhoff K, Banniettis N, Hammerschlag MR, Smith-Norowitz TA. Chlamydia pneumoniae enhances CD4+ and CD8+ effector memory cell IL-2 and IL-4 responses in stimulated peripheral blood mononuclear cells in human subjects. J Allergy Clin Immunol 2018; 141 (2): AB123.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.