Pigs lacking Natural Killer T cells have altered cellular responses to influenza

It is increasingly recognized that innate T cells such as natural killer T (NKT) cells, mucosal associated invariant T (MAIT) cells, and gd T cells play an important role in shaping adaptive immune responses following influenza infection or vaccination. This is largely through the multiple cytokines these cells rapidly release upon activation, which have downstream effects on the scope and magnitude of virus-specific T and B cells, and antibodies which form. Here, we examined the contribution of NKT cells to this process using pigs, which are considered a highly translational model of human influenza infection. CD1D-expressing and CD1D-deficient pigs that respectively possess and lack NKT cells were infected with the swine influenza virus H3N2 A/Swine/Colorado/23619/1999 (CO99) with or without prior mucosal immunization with a recombinant H3N2 A/Swine/Texas/4199-2/1998 (TX98) modified live vaccine encoding a truncated NS1 protein (TX98?NS1). Vaccination reduced virus load and lung pathology by similar amounts in both genotypes. However, NKT cell status had a significant impact on the underlying immune response, which manifested in the single cell transcriptomes of lung cells, rate of virus-specific T cell accumulation, distribution of T cells in lung tissue, and ratio of virus-specific IgG subclasses. Additionally, a single cell TCR and BCR sequencing analysis found higher numbers of expanded T and B cell clones in NKT cell-deficient versus -intact pigs, some of which are potential IAV-reactive clones. Collectively, our results indicate that NKT cells play an influential role in coordinating the adaptive immune response to influenza, particularly in restraining cellular immunity during peak infection. Although these changes did not the disease course in the current investigation, they are likely to be of significance in other settings. Overall design: On day 0, CD1D-/- and CD1D-/+ pigs were intranasally vaccinated with 106 TCID50 of TX98 NS1?126 using an atomization device (MAD Nasal™, Teleflex, Morrisville, NC, USA). At 21 DPV [0 days post-challenge (0 DPC)] , CD1D-/- and CD1D-/+ pigs were intratracheally challenged with 106 median (50%) of tissue culture infectious dose (TCID50) of CO99 and monitored for 5 days. At 5 DPC (26 DPV), infected pigs were euthanized