Peculiar phenotypic and functional characteristics of pulmonary mucosal CD8 T-cells compared to peripheral blood

Yulia Alexandrova^1,2,3, Oussama Meziane^1,2, Ron Olivenstein⁴, FranckDupuy¹,Elaine Thomson^1,2,3, Marianna Orlova¹, Erwin Schurr^1,5, Petronela Ancuta^6,7, Nicolas Chomont^6,7, Jerome Estaquier⁸, Nicole F. Bernard^1,2, Cecilia T. Costiniuk^1,2,9,and Mohammad-Ali Jenabian^2,3,7

¹Infectious Diseases and Immunity in Global Health Program, Research Institute of McGill University Health Centre, Montreal, QC, Canada
²Department of Biological Sciences, Université du QuébecàMontréal, Montreal, QC, Canada
³Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
⁴Division of Respirology, Department of Medicine, McGill University, Montreal, QC, Canada
⁵Department of Human Genetics, McGill University, Montreal, QC, Canada
⁶Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montreal, QC, Canada
⁷Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montreal, QC, Canada
⁸Centre Hospitalier Universitaire (CHU) de Québec Research Center, Faculty of Medicine, Université Laval, Quebec City,QC, Canad
⁹Division of Infectious Diseases and Chronic Viral Illness Service, McGill University Health Centre, Montreal, QC, Canada

Background:Airway mucosa is continuously exposed to various airborne stimuli which, in turn, affect lung mucosal immune cell physiology.CD8 T-cells play key immune functions via cytokine secretion and cytotoxicity towards virus-infected cells. Furthermore, HIV+ individuals have high burdens of pulmonary infections and lung cancers despite suppressive antiretroviral therapy (ART). We thus performed phenotypical and functional analyses ofpulmonary versus peripheral blood CD8 T-cells in ART-treated HIV+ and uninfected participants.

Methods:Bronchoalveolar lavage (BAL) fluid and matched blood were obtained from asymptomatic ART-treated HIV+ smokers (n=11) and non-smokers (n=15) and uninfected smokers (n=7) and non-smokers (n=10). CD8 T-cell subsets and phenotypes were assessed by flow cytometry. Perforin/granzyme-B content, degranulation (CD107a expression) and cytotoxicity against autologous Gag peptide-pulsed CD4 T-cells (Annexin-V⁺) following in vitro stimulation were assessed.

Results:In all groups, pulmonary CD8 T-cells were enriched in effector memory subsets compared to blood and displayed higher levels of activation (HLA-DR⁺) and exhaustion (PD1⁺) markers. Significant reductions in proportions of senescent pulmonary CD28^-CD57⁺ CD8 T-cells were observed only in HIV+ smokers. Pulmonary CD8 T-cells showed lower perforin expression ex vivo compared to blood CD8 T-cells, with reduced granzyme-B expression only in HIV+ non-smokers. BAL CD8 T-cells showed significantly lower fold change in degranulation upon stimulation and lower CD4 killing capacity than blood CD8 T-cells.

Conclusion: Regardless of HIV status, pulmonary mucosal CD8 T-cells are more differentiated, activated and exhausted, with reduced killing-capacity in vitro than blood CD8 T-cells. Smoking alters CD8 dynamics in HIV individuals by reducing their immuno-senescence.