Ex vivo-stimulated cytokine expression in whole blood indicates swine influenza vaccine-induced immune memory

Swine influenza viruses (SwIAV) pose a zoonotic threat and contribute to interspecies viral reassortment. Effective vaccination strategies are essential, yet accessible correlates of protection remain limited. We simplified a whole blood (WB) assay to assess immune memory ex vivo in pigs vaccinated with Respiporc FLU3® (n = 6) versus placebo controls (n = 6), followed by homologous challenge with SwIAV (H1avN1). Vaccinated pigs exhibited no lung lesions and minimal viral loads. WB samples, collected pre- and post-vaccination and at day 1 and 5 post-challenge (dpch), were stimulated with SwIAV to quantify IL2 , IL4 , IFNγ , TNFα , and granzyme B ( GZMB ) mRNA via qPCR. High IL2 and moderate IL4 mRNA elicited in WB post-booster predicted reduced viral load and lung pathology. Concomitantly, high IFNγ in WB from controls at 5dpch correlated with lesion severity, indicating excessive inflammation in non-vaccinates. Post-challenge, IL4/IL2 mRNA ratios increased in virus-stimulated WB of vaccinates, suggesting Th2-associated resolution of infection. In contrast, controls showed declining IL4/IL2 ratios post-challenge, correlating with disease severity. Thus, the simplified WB assay allows identification of virus-specific immune responses associating with protection, without requiring extensive laboratory infrastructure. By recording the ex vivo -triggered SwIAV-specific IL4/IL2 mRNA dynamics, which develop between booster and challenge monitoring immune memory may simplify determination of vaccination success.

Prophyl Animal Health Ltd.
Ceva Tiergesundheit GmbH
Ceva Santé Animale, France
Ceva Santé Animale, Hungary