Intranasal type I interferon treatment is beneficial only when administered before clinical signs onset in the SARS-CoV-2 hamster model.

Impaired type I interferons (IFNs) production or signaling have been associated with severe COVID-19, further promoting the evaluation of recombinant type I IFNs as therapeutics against SARS-CoV-2 infection. In the Syrian hamster model, we show that intranasal administration of IFN-α starting one day pre-infection or one day post-infection limited weight loss and decreased viral lung titers. By contrast, intranasal administration of IFN-α starting at the onset of symptoms three days post-infection had no impact on the clinical course of SARS-CoV-2 infection. Our results provide evidence that early type I IFN treatment is beneficial, while late interventions are ineffective, although not associated with signs of enhanced disease.

Standardized Whole Blood Assay and Bead-Based Cytokine Profiling Reveal Commonalities and Diversity of the Response to Bacteria and TLR Ligands in Cattle.

Recent developments in multiplex technologies enable the determination of a large nu\mber of soluble proteins such as cytokines in various biological samples. More than a one-by-one determination of the concentration of immune mediators, they permit the establishment of secretion profiles for a more accurate description of conditions related to infectious diseases or vaccination. Cytokine profiling has recently been made available for bovine species with the development of a Luminex® technology-based 15-plex assay. Independently from the manufacturer, we evaluated the bovine cytokine/chemokine multiplex assay for limits of detection, recovery rate, and reproducibility. Furthermore, we assessed cytokine secretion in blood samples from 107 cows upon stimulation with heat-killed bacteria and TLR2/4 ligands compared to a null condition. Secretion patterns were analyzed either using the absolute concentration of cytokines or using their relative concentration with respect to the overall secretion level induced by each stimulus. Using Partial Least Square-Discriminant Analysis, we show that the 15-cytokine profile is different under Escherichia coli, Staphylococcus aureus, and Streptococcus uberis conditions, and that IFN-γ, IL-1ß, and TNF-α contribute the most to differentiate these conditions. LPS and E. coli induced largely overlapping biological responses, but S. aureus and S. uberis were associated with distinct cytokine profiles than their respective TLR ligands. Finally, results based on adjusted or absolute cytokine levels yielded similar discriminative power, but led to different stimuli-related signatures.

Th17-related mammary immunity, but not a high systemic Th1 immune response is associated with protection against E. coli mastitis.

Vaccination against bovine mastitis lags behind despite high demand from the dairy industry and margin for efficacy improvement. We previously compared two immunization protocols against E. coli using either only the intramuscular route or a combination of intramuscular and mammary ductal routes, also known as 'prime and pull' strategy. A homologous mammary challenge during the memory phase showed that immunization favorably modified the mastitis course, notably in locally immunized cows in comparison to intramuscular and control adjuvant-only groups. Here, we performed whole-blood profiling through RNA-seq transcriptome and plasma cytokine 15-plex analyses at time points of the E. coli mastitis that showed significant clinical and laboratory differences among the groups. Diminished production of inflammatory cytokines and increased IFNγ were detected in the blood of immunized cows, where a T lymphocyte activation profile was evidenced at 12-h post infection. Acute phase neutropenia was less severe in these cows, and pathways related to neutrophil diapedesis and monocyte activation were also present. Furthermore, three intramammary-immunized cows showing faster healing and shorter mastitis duration had gene profiles that differed from their counterparts, but without any clue for the mastitis susceptibility difference. Inasmuch, when gene expression of CD4 T cells was assessed in mammary tissue, enrichment of IL-17-associated pathways was identified in the quarters of intramammary-immunized cows not only after challenge but also in the control quarters that were not infected. These findings indicate that local immunization mobilizes protective mechanisms that rely on the settlement of type 3 immunity-related CD4 T cells prior to infection.