Nitric oxide antiviral effects

These compounds contain the fragment R as an alkyl or aryl moiety. In other words, they result from the esterification of an alcohol or a phenol with nitrous acid, nitric acid, phosphoric acid, sulfuric acid, or sulfamic acid, respectively. Many of the esters to be examined in this chapter must be activated prior to eliciting their effects, e.g., the organic nitrites and nitrates, which act as donors of nitric oxide or an analogous molecule, and phosphates, which are activated by hydrolysis or even by phosphorylation (antiviral agents). Sulfates are very seldom active or used as prodrugs, but they have significance as metabolites and as industrial xenobiotics. 

Croen, K. D. (1993). Evidence for an antiviral effect of nitric oxide. J. Clin. Invest. 91, 2446-2452. 

Isolations of noformycin (10) [25] with antiviral activity [26] and an inhibitory effect towards inducible-nitric oxide synthase [27] and other iminopyrroglutamic acid derivatives 11-13 have also been reported. The latter were inhibitors towards Erwinia amylovora, a bacterium responsible for the fire light disease of apple and pear trees [28] (Figure 10.3). 

Other possible modes of action may centre on stimulation of T cells (this occurred with the live aroA mutant of A. salmonicida Marsden et al., 1996), which introduces the role of cellular and innate rather than humoral immunity as the mode of action. For this, examples include A. hydrophila LPS (Baba et al., 1988) and E. tarda ECPs (Lee et al., 2010). Of course, there could be involvement of humoral, cell-mediated and innate immune parameters as stated for the i.p. administration of a live auxotrophic aroA mutant of A. hydrophila with effectiveness against furunculosis in rainbow trout (Vivas et al, 2004). Other possibilities include the evidence that one commercial formalized whole cell V. anguillarum vaccine induces Mx gene (these are inducible by Type I interferons and have a role in antiviral activity) expression in Atlantic salmon after administration intraperitoneally (Acosta et al., 2004). In another example, vaccination with P. damselae subsp. piscicida cells were found to enhance the nitric oxide response, i.e. the production of reactive nitrogen intermediates with their antimicrobial activities, to infection with the pathogen, and is correlated with the level of protection (Acosta et al., 2005). There was inhibition of F columnare adhesion to the skin of immersion vaccinated eel (Mano et al., 1996). Finally, mention will be made of a possible mechanism of protection of V. anguillarum vaccines that may well involve the inhibition of bacterial attachment by unknown factors in the skin mucus (Kawai and Kusuda, 1995). 

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