Inhibitory Influence of the Hexapeptidic Sequence SLIGRL on Influenza A Virus Infection in Mice

Abstract

Proteinase-activated receptor 2 (PAR 2 ) is widely expressed in the respiratory tract and is an integral component of the host antimicrobial defense system. The principal aim of this study was to investigate the influence of a PAR 2 -activating peptide, SLIGRL, on influenza A virus (IAV)-induced pathogenesis in mice. Intranasal inoculation of BALB/c mice with influenza A/PR/8/34 virus caused time-dependent increases in the number of pulmonary leukocytes (recovered from bronchoalveolar lavage fluid), marked airway histopathology characterized by extensive epithelial cell damage, airway hyper-responsiveness to the bronchoconstrictor methacholine, and elevated levels of inflammatory chemokines (keratinocyte-derived chemokine and macrophage inflammatory protein 2) and cytokines (interferon-␥). It is noteworthy that these IAV-induced effects were dose-dependently attenuated in mice treated with a PAR 2 -activating peptide, SLIGRL, at the time of IAV inoculation. However, SLIGRL also inhibited IAV-induced increases in pulmonary leukocytes in PAR 2 -deficient mice, indicating these antiviral actions were not mediated by PAR 2 . The potency order obtained for a series of structural analogs of SLIGRL for anti-IAV activity (IGRL Ͼ SLIGRL Ͼ LSIGRL Ͼ2-furoyl-LIGRL) was also inconsistent with a PAR 2 -mediated effect. In further mechanistic studies, SLIGRL inhibited IAV-induced propagation in ex vivo perfused segments of trachea from wild-type or PAR 2 (Ϫ/Ϫ) mice, but did not inhibit viral attachment or replication in MadinDarby canine kidney cells and chorioallantoic membrane cells, which are established hosts for IAV. In summary, SLIGRL protected mice from IAV infection independently of PAR 2 and independently of direct inhibition of IAV attachment or replication, potentially through the activation of endogenous antiviral pathways within the mouse respiratory tract.

Multiple roles of the coagulation protease cascade during virus infection

“…45 However, a recent study showed that this peptide mediated PAR2-independent protection against IAV. 74 It is difficult to explain the different results found with IAV infection in PAR2ko mice ( Table 2). This could be due to differences in virus dose and virus preparation.…”

Investigating the role of MRGPRC11 and capsaicin-sensitive afferent nerves in the anti-influenza effects exerted by SLIGRL-amide in murine airways

“…Our laboratory has recently shown that the hexapeptidic sequence SLIGRL-amide (Ser-Leu-Ile-Gly-Arg-Leu-NH 2 ) inhibits IAV infection in mice [ 7 ]. SLIGRL-amide is a well-established activator of protease-activated receptor-2 (PAR-2) [ 8 ].…”

“…SLIGRL-amide is a well-established activator of protease-activated receptor-2 (PAR-2) [ 8 ]. However, SLIGRL-amide inhibits IAV infection independently of PAR-2 as anti-viral effects were preserved in PAR2 (−/−) mice [ 7 ]. SLIGRL-amide has also been reported to activate MRGPRC11, a subtype of MAS-related G protein-coupled receptor (MRGPR) [ 8 – 10 ].…”

Neoadjuvant anti-tumor vaccination prior to surgery enhances survival

“…PR8 virus was propagated in the allantoic fluid of 9-day old embryonated chicken eggs (Altona Hatchery, Forrestfield, Australia) at 37°C for 3 days and harvested as previously described [22], stored in single use aliquots at −80°C and diluted 1:100 to 1:400 in sterile PBS prior to intranasal vaccination of mice.…”