Cytokine-independent detection of antigen-specific germinal center T follicular helper (Tfh) cells in immunized non-human primates using a live cell Activation Induced Marker (AIM) technique1

• Published in: The Journal of immunology (1950) Vol. 197; no. 3; pp. 994 - 1002
• Main Authors: Havenar-Daughton, Colin, Reiss, Samantha M., Carnathan, Diane G., Wu, Jennifer E., Kendric, Kayla, de la Peña, Alba Torrents, Kasturi, Sudhir Pai, Dan, Jennifer M., Bothwell, Marcella, Sanders, Rogier W., Pulendran, Bali, Silvestri, Guido, Crotty, Shane
• Format: Journal Article
• Language: English
• Published: 22-06-2016
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.1600320

A range of current candidate AIDS vaccine regimens are focused on generating protective HIV neutralizing antibody responses. Many of these efforts rely on the rhesus macaque animal model. Understanding how protective antibody responses develop and how to increase their efficacy are both major knowledge gaps. Germinal centers (GC) are the engines of antibody affinity maturation. GC T follicular helper (GC Tfh) CD4 T cells are required for GCs. Studying vaccine-specific GC Tfh cells after protein immunizations has been challenging, as antigen-specific GC Tfh cells are difficult to identify by conventional intracellular cytokine staining (ICS). Cytokine production by GC Tfh cells may be intrinsically limited in comparison to other T helper effector cells, as the biological role of a GC Tfh cell is to provide help to individual B cells within the GC, rather than secreting large amounts of cytokines bathing a tissue. To test this idea, we developed a cytokine-independent method to identify antigen-specific GC Tfh cells. RNAseq was performed using TCR stimulated GC Tfh cells to identify candidate markers. Validation experiments determined CD25 (IL2Rα) and OX40 to be highly upregulated activation induced markers (AIM) on the surface of GC Tfh cells after stimulation. In comparison to ICS, the AIM assay identified > 10-fold more antigen-specific GC Tfh cells in HIV Env protein immunized macaques (BG505 SOSIP). CD4 T cells in blood were also studied. In sum, AIM demonstrates that antigen-specific GC Tfh cells are intrinsically stingy producers of cytokines, which is likely an essential part of their biological function.