Oral Presentation Lorne Infection and Immunity 2022

Vδ2+Vγ9+ T-cells downregulate CCR6 following phosphoantigen-driven in vivo expansion in pigtail macaques (Macaca nemestrina) (#23)

Isaac M Barber-Axthelm 1 , Kathleen M Wragg 1 , Anne M Gibbon 2 , Stephen J Kent 1 3 4 , Jennifer A Juno 1
  1. Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Parkville, Victoria, Australia
  2. Monash Animal Research Platform, Monash University, Clayton, Victoria, Australia
  3. ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, The University of Melbourne, Parkville, Victoria, Australia
  4. Melbourne Sexual Health Centre and Infectious Disease Department, Alfred Health, Monash University Central Clinical School, Melbourne, Victoria, Australia

Introduction: Vδ2+ T-cells, a subset of unconventional T-cells that recognise phosphoantigens, have garnered significant interest as immunotherapies against cancers and infectious diseases. These cells can be readily expanded pharmacologically and can mediate a wide variety of immune functions, including pro-inflammatory cytokine production, direct killing of target cells, and antigen presentation to conventional T-cells. Despite promising results in preclinical studies, the clinical efficacy of γδ T-cell immunotherapies has been limited. Improving Vδ2+ T-cell immunotherapies will likely require refinements to the treatment protocols, along with an improved understanding of the tissue distribution and phenotype of expanded γδ T-cells.

Methods: We studied the impact of different antigenic stimuli and routes of administration on Vδ2+Vγ9+ T-cell expansion and tissue trafficking in 7 pigtail macaques (Macaca nemestrina). Macaques were treated with zoledronate, HMB-PP, or IPP intravenously (IV) or intratracheally (IT), along with recombinant human IL-2 (rhIL-2), to stimulate in vivo Vδ2+Vγ9+ T-cell expansion. γδ T-cell frequencies and phenotypes were monitored in blood, lymph nodes, and mucosal tissues, and compared to baseline samples.

Results: In vivo expanded Vδ2+Vγ9+ T-cells were readily identified the blood (13-28.5% of CD3+ T-cells, 0.61-2.75% at baseline) and airway mucosa (6.09-14.6% of CD3+ T-cells, 3.25-6.51% at baseline) following IV antigen administration. Expanded Vδ2+Vγ9+ T-cells were predominately confined to the airway mucosa following intratracheal antigen administration. Strikingly, Vδ2+Vγ9+ T-cells in the blood, and to a lesser degree in the airway mucosa, were predominately CCR6-. Additionally, in vitro expanded Vδ2+ T-cells were predominately CCR6-, with CCR6 expression being negatively associated with rhIL-2 concentrations. No significant differences in the expansion capacity of sort-purified CCR6+ or CCR6- Vδ2+ T-cells were observed in vitro, suggesting that CCR6 is being downregulated during phosphoantigen mediated expansion. This was further supported by acute in vitro stimulations, where CCR6 expression decreased following cytokine stimulation.

Conclusion: Our findings indicate that tissue distribution of in vivo expanded Vδ2+ T-cells can be modulated by changing the route of antigen administration. Furthermore, phosphoantigen and rhIL-2 driven Vδ2+ T-cell expansion is associated with a loss of CCR6 expression in pigtail macaques. This work has implications for improving Vδ2+ T-cell immunotherapies against both infectious and neoplastic diseases.