Influenza (flu) is caused by a highly contagious virus that is spread by coughs and sneezes. Flu symptoms include high fever, chills and sweating, sore throat, weakness, headache, muscle and joint pains, and cough. Older people and those with an underlying medical condition are more likely to develop serious complications, including secondary bacterial pneumonia, primary influenza pneumonia, and inflammation of the brain or heart. There are three types of flu virus: A, B, and C. The flu virus has a unique ability to change its surface structure. This allows it to escape recognition by the body's immune system and cause widespread illness (epidemics and pandemics). Most cases of influenza occur within a 6- to 8-week period during winter and spring. Epidemics occur when there are minor changes in the nature of the virus so that more people within a community are susceptible. Influenza A is more likely to cause epidemics. Pandemics (worldwide epidemics) occur when there are major changes in the virus so that the disease affects a large proportion of people in a geographic region or on more than one continent. The findings presented in this article have many important implications for understanding the influenza A (H1N1) viral pathogenesis, prevention, and treatment. Direct viral cytotoxicity (referred cytopathic effect) is only a fraction of several types of events induced by virus infection. Nitric oxide and oxygen free radicals such as superoxide anion (O2-·) are generated markedly in influenza A (including H1N1) virus-infected host boosts, and these molecular species are identified as the potent pathogenic agents. The mutual interaction of nitric oxide (NO) with O2-· resulting in the formation of peroxynitrite is operative in the pathogenic mechanism of influenza virus pneumonia. Influenza virus infection involves pathological events in which oxygen free radicals play an important role in the pathogenesis. The toxicity and reactivity of oxygen radicals generated in excessive amounts mediate the overreaction of the host's immune response against the organs or tissues in which viruses are replicating, and this may explain the mechanism of tissue injuries observed in influenza virus infection of various types. In this article, the types of protection of carnosine in its bioavailable non-hydrolyzed forms in formulations are considered against reactive oxygen radical species-dependent injury, peroxynitrite damage, and other types of viral injuries in which impaired immune responses to viral pathogens are usually involved. Carnosine (β-alanyl-L-histidine) shows the pharmacological intracellular correction of NO release, which might be one of the important factors of natural immunity in controlling the initial stages of influenza A virus infection (inhibition of virus replication) and virus-induced regulation of cytokine gene expression. The protective effects of orally applied non-hydrolyzed formulated species of carnosine include at least the direct interaction with NO, inhibition of cytotoxic NO-induced proinflammatory condition, and attenuation of the effects of cytokines and chemokines that can exert profound effects on inflammatory cells. These data are consistent with the hypothesis that natural products, such as chicken soup and chicken breast extracts rich in carnosine and its derivative anserine (β-alanyl-1-methyl-L-histidine), could contribute to the pathogenesis and prevention of influenza virus infections and cold but have a limitation due to the susceptibility to enzymatic hydrolysis of dipeptides with serum carnosinase and urine excretion after oral ingestion of a commercial chicken extract. The formulations of non-hydrolyzed in digestive tract and blood natural carnosine peptide and isopeptide (γ-glutamyl-carnosine) products, manufactured at the cGMP-certified facility and patented by the authors, have promise in the control and prevention of influenza A (H1N1) virus infection, cough, and cold.
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