Grass pollen inhibits peripheral blood responses to rhinovirus independent of specific IgE

Background Grass pollen (GP) can trigger allergic rhinitis (AR) and asthma in sensitized individuals. Whilst cross-linking of allergen-specific IgE (sIgE) by house dust mite allergen can attenuate antiviral responses, the role of pollen is less clear. This study aimed to investigate the effects of GP on early rhinovirus responses in adults with AR and GP allergy, compared with individuals with other allergies, and non-atopic participants. Methods Cryopreserved peripheral blood mononuclear cells (PBMCs) from adults with AR and GP allergy (n=22), other allergies (n=18), and non-atopic controls (n=10), were exposed to human rhinovirus 16 (hRV-16) (MOI= 1), Bahia GP (BaGP) extract (30 μg/mL), or in combination. Plasmacytoid dendritic cells (pDCs) and myeloid dendritic cells (mDCs) were sorted by flow cytometry to investigate the involvement of these cells in stimuli-induced responses. Cytokine secretion after 24 hours and serum BaGP sIgE were quantified by ELISA. Results In all groups, hRV-16 induced interferon (IFN)-α 1 and IFN-γ-induced protein 10 (IP-10), with the former being significantly higher in non-atopic participants compared to allergic individuals (p ≤ 0.05), while BaGP induced IL-6 and TNF-α secretion. BaGP extract suppressed hRV-16-induced IP-10, regardless of the allergy status and presence or absence of BaGP-sIgE. However, its effect on hRV-16-induced IFN-α 1 was variable and did not differ between groups. Plasmacytoid DCs appeared to contribute to the IP-10 secretion in response to hRV-16, and this response was inhibited by BaGP, whilst mDCs secreted IL-6 in response to BaGP. Conclusion BaGP extract inhibited the early hRV-16-induced antiviral response in PBMCs, and induced inflammatory responses, that were not associated with detectable allergen-specific IgE and allergy status. These findings suggest a non-IgE mediated effect of grass pollen extract on early inflammatory responses in the peripheral immune system.