Swine influenza (SI) is an acute respiratory disease of pigs, caused by swine influenza virus (SIV). Little is known about the inflammatory response in the lung during acute SI and its correlation with clinical signs or lung pathology. Moreover, until now there has been a limited amount of data available on the relationship between the concentrations of pro- and anti-inflammatory cytokines in the lungs and the serum concentration of acute-phase proteins (APPs) in SIV-infected pigs. In the present study, the porcine inflammatory and immune responses during acute influenza caused by H1N1 SIV (SwH1N1) were studied. Nine pigs were infected intratracheally, and five served as controls. Antibodies against SIV were measured by haemagglutination inhibition assay, and the influenza-virus-specific T-cell response was measured using a proliferation assay. C-reactive protein (CRP), haptoglobin (Hp), serum amyloid A (SAA), and pig major acute-phase protein (Pig-MAP) the concentrations in serum and concentration of IL-1β, IL-6, IL-8, IL-10, TNF-α and IFN-γ in lung tissues were measured using commercial ELISAs.

BackgroundSwine influenza (SI) is an acute respiratory disease caused by swine influenza virus (SIV). Swine influenza is generally characterized by acute onset of fever and respiratory symptoms. The most frequent complications of influenza are secondary bacterial pneumonia. The objective of this work was to study the acute phase proteins (APP) responses after coinfection of piglets with H1N1 swine influenza virus (SwH1N1) and Pasteurella multocida (Pm) in order to identify whether the individual APP response correlate with disease severity and whether APP could be used as markers of the health status of coinfected pigs.ResultsIn all coinfected pigs clinical sings, including fever, coughing and dyspnea, were seen. Viral shedding was observed from 2 to 7 dpi. The mean level of antibodies against Pm dermonecrotoxin in infected piglets increase significantly from 7 dpi. Anti-SwH1N1 antibodies in the serum were detected from 7 dpi. The concentration of C-reactive protein (CRP) increased significantly at 1 dpi as compared to control pigs, and remained significantly higher to 3 dpi. Level of serum amyloid A (SAA) was significantly higher from 2 to 3 dpi. Haptoglobin (Hp) was significantly elevated from 3 dpi to the end of study, while pig major acute phase protein (Pig-MAP) from 3 to 7 dpi. The concentrations of CRP, Hp and SAA significantly increased before specific antibodies were detected. Positive correlations were found between serum concentration of Hp and SAA and lung scores, and between clinical score and concentrations of Pig-MAP and SAA.ConclusionsThe results of current study confirmed that monitoring of APP may revealed ongoing infection, and in this way may be useful in selecting clinically healthy pigs (i.e. before integration into an uninfected herd). Present results corroborated our previous findings that SAA could be a potentially useful indicator in experimental infection studies (e.g. vaccine efficiency investigations) or as a marker for disease severity, because of correlation observed between its concentration in serum and disease severity (lung scores, clinical scores).

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Acute phase proteins (APPs) and immune responses in pigs after experimental infection with H1N2 swine influenza virus (SwH1N2) were studied. Eight piglets were infected intranasally with SwH1N2. Four served as controls. Antibodies against swine influenza virus (SIV)s were measured by hemagglutination inhibition assay. The proliferation assay was used to measure influenza-specific cell-mediated response. Hematological parameters were measured on a hematology analyzer. C-reactive protein (CRP), haptoglobin (Hp), serum amyloid A (SAA) and pig major APP (Pig-MAP) concentrations in serum were measured using commercial ELISAs. Antibodies against SwH1N2 in the serum of infected pigs were detected from 7 dpi. SwH1N2-specific T-cell response was observed from 5 dpi. A significant drop in lymphocyte numbers and an increase in medium-sized cell (MID) counts with no accompanying leukopenia was observed in all infected pigs from 3 to 7 dpi. In infected pigs, concentrations of CRP, Hp and SAA increased significantly when the greatest amounts of virus were shed (from 1 to 3 dpi). The level of Pig-MAP remained unchanged during study. The significant positive correlation found between maximum concentrations of SAA in serum and lung scores, makes SAA a potentially useful indicator in experimental infection studies (e.g. vaccine efficiency investigations) or as a marker for disease severity, but to confirm this hypothesis more studies are needed.

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