CD4+ T cell calibration of antigen-presenting cells optimizes antiviral CD8+ T cell immunity.

Antiviral CD8+ T cell immunity depends on the integration of various contextual cues, but how antigen-presenting cells (APCs) consolidate these signals for decoding by T cells remains unclear. Here, we describe gradual interferon-α/interferon-ß (IFNα/ß)-induced transcriptional adaptations that endow APCs with the capacity to rapidly activate the transcriptional regulators p65, IRF1 and FOS after CD4+ T cell-mediated CD40 stimulation. While these responses operate through broadly used signaling components, they induce a unique set of co-stimulatory molecules and soluble mediators that cannot be elicited by IFNα/ß or CD40 alone. These responses are critical for the acquisition of antiviral CD8+ T cell effector function, and their activity in APCs from individuals infected with severe acute respiratory syndrome coronavirus 2 correlates with milder disease. These observations uncover a sequential integration process whereby APCs rely on CD4+ T cells to select the innate circuits that guide antiviral CD8+ T cell responses.

Screening and development of monoclonal antibodies for identification of ferret T follicular helper cells.

The ferret is a key animal model for investigating the pathogenicity and transmissibility of important human viruses, and for the pre-clinical assessment of vaccines. However, relatively little is known about the ferret immune system, due in part to a paucity of ferret-reactive reagents. In particular, T follicular helper (Tfh) cells are critical in the generation of effective humoral responses in humans, mice and other animal models but to date it has not been possible to identify Tfh in ferrets. Here, we describe the screening and development of ferret-reactive BCL6, CXCR5 and PD-1 monoclonal antibodies. We found two commercial anti-BCL6 antibodies (clone K112-91 and clone IG191E/A8) had cross-reactivity with lymph node cells from influenza-infected ferrets. We next developed two murine monoclonal antibodies against ferret CXCR5 (clone feX5-C05) and PD-1 (clone fePD-CL1) using a single B cell PCR-based method. We were able to clearly identify Tfh cells in lymph nodes from influenza infected ferrets using these antibodies. The development of ferret Tfh marker antibodies and the identification of ferret Tfh cells will assist the evaluation of vaccine-induced Tfh responses in the ferret model and the design of novel vaccines against the infection of influenza and other viruses, including SARS-CoV2.