Clinical signs, pathologies, antigen detection, and influenza mRNA positivity results for this studya

Animal group and designationClinical feature(s)Lung pathologybTB node pathologyPresence of IHC (NP) antigenResult for indicated viral mRNA analysis
Mock infected
    Day 23.9% Weight lossNegativeNegativeNegativeNegativeNegative
    Day 41.5% Weight lossNegativeNegativeNegativeNegativeNegative
    Day 71.35% Weight lossNegativeNegativeNegativeNegativeNegative
Influenza infected
    Day 2 ARhinorrhea, reduced feces production, 1.14% weight lossAcute-subacute bronchopneumonia (accessory lobe)ReactivePositive+++Positive+++Positive+++
    Day 2 BReduced feces productionAcute-subacute diffuse bronchopneumoniaReactivePositive+NegativeNegative
    Day 4 AIncreased respiratory sounds, rhinorrhea, 8% weight lossAcute-subacute bronchopneumonia (L caudal lobe)ReactivePositive+NegativeNegative
    Day 4 B3.3% Weight lossBronchopneumonia (L caudal lung lobe)ReactivePositive+NegativePositive
    Day 7 AIncreased respiratory sounds, rhinorrhea, conjunctivitis, rising WBC count, 6.6% weight lossSubacute bronchopneumonia (accessory lobe)ReactiveNegativeNegativeNegative
    Day 7 BRhinorrhea, conjunctivitis, rising WBC count, 3.22% weight lossSubacute bronchopneumonia (R caudal and accessory lobes)Grossly normal but reactive on histologyPositive ++Positive+Positive +
  • a IHC, immunohistochemistry; WBC, white blood cell; TB, tracheobronchial; +, weakly detected;++ , detected; +++, strongly detected. The table summarizes clinical features of control and experimental animals, pathology, and positivity of lung samples for influenza virus mRNA. Live influenza virus was found on a pharyngeal swab from animal Day 7 B at day 2 p.i., and a complete blood count showed a rise in absolute and relative lymphocyte numbers at day 4 p.i. in that animal and the same in animal Day 7 A. All infected animals showed increased bronchial lavage fluid cellularity, particularly at day 2 and day 4 p.i. We were unable to isolate replicating influenza virus above plaque assay detection levels from the lung lesions, but this was not surprising since the disease was considered mild and the tissue sampled for viral isolation was on the periphery of the lesions which were first and foremost set aside for assays, proteomics, and histology. Detection of viral antigen staining was performed using one tissue sample, while detection of viral mRNA was performed using another tissue sample. One sample could not be used for both, due to unique sample preparation protocols and this explains why detection of viral antigen is not always concordant with detection of viral mRNA. Of note, one of the mock-infected animals had a transient nasal discharge (slight and clear), and all control animals had mild diffuse pulmonary inflammation, most likely due to the bronchial lavages. Finally, mock-infected animals experienced a mild weight loss attributed to the stress of experimental manipulation.

  • b L, left; R, right.