TGF-ß1 signaling inhibit the in vitro apoptotic, infection and stimulatory cell response induced by influenza H1N1 virus infection on A549 cells.

Influenza A virus (IAV) infection induces host cell responses that could derive in inflammatory and apoptotic response. In this respect, in multiple pathological situations, TGF-ß1 has shown anti-inflammatory effect, but its role during IAV infection is poorly understood. Interestingly, recent profiling expression studies have suggested that the TGF-ß1 pathway could be functionally related to the IAV infection's host response. To gain an understanding of the involvement of TGF-ß1's signaling pathway during IAV infection, we compared different apoptotic proteins such as TNFR1, Fas ligand, XIAP, cIAP, among others proteins, and pro-inflammatory elements like IL-1ß in the A549 cells during IAV infection (H1N1/NC/99), with and without 1 h of pre-treatment with TGF-ß1. Pre-incubation with TGF-ß1 significantly inhibited apoptosis and the presence of pro-apoptotic factors. Moreover, the relative abundance of immunodetected IAV M1 protein along 24 -h post-infection period was abridged, which correlated with a disminished infectious viral progeny Additionally, caspase 1 activation and increase of IL-1ß induced by IAV infection was also reduced by TGF-ß1 signaling activation. Whereas IAV infection increase of Smad-7 and, as consequence, partially inhibiting Smad2/3 phosphorylation, pre-treatment with TGF-ß1 blocked IAV-dependent Smad7 induction and prevented Smad2/3 signaling shutdown. All these data suggest the role of TGF-ß1 signaling pathway in the control of host cell response induced by the IAV infection and identify a potential clinical target to modulate acute cell death.

Flagellin is a Th1 polarizing factor for human CD4+ T cells and induces protection in a murine neonatal vaccination model of rotavirus infection.

Neonates have an increased susceptibility to infections, particularly those caused by intracellular pathogens, leading to high morbidity and mortality rates. This is partly because of a poor response of neonatal CD4+ T cells, leading to deficient antibody production and a low production of IFN-γ, resulting in deficient elimination of intracellular pathogens. The poor memory response of human neonates has underpinned the need for improving vaccine formulations. Molecular adjuvants that improve the response of neonatal lymphocytes, such as the ligands of toll-like receptors (TLRs), are attractive candidates. Among them, flagellin, the TLR5 ligand, is effective at very low doses; prior immunity to flagellin does not impair its adjuvant activity. Human CD4+ and CD8+ T cells express TLR5. We found that flagellin induces the expression of IFN-γ, IL-1ß and IL-12 in mononuclear cells from human neonate and adult donors. When human naïve CD4+ T cells were activated in the presence of flagellin, there was high level of expression of IFN-γ in both neonates and adults. Furthermore, flagellin induced IFN-γ production in Th1 cells obtained from adult donors; in the Th2 population, it inhibited IL-4 cytokine production. Flagellin also promoted expression of the IFN-γ receptor in naive CD4+ T cells from neonates and adults. To test the adjuvant capacity of flagellin in vivo, we used a murine neonate vaccination model for infection with rotavirus, a pathogen responsible for severe diarrhea in young infants. Using the conserved VP6 antigen, we observed an 80% protection against rotavirus infection in the presence of flagellin, but only in those mice previously primed in the neonatal period. Our data suggest that flagellin could be an attractive adjuvant for achieving a Th1 response.