Vaccination of influenza a virus decreases transmission rates in pigs

Romagosa, Anna; Allerson, Matt; Gramer, Marie; Joo, Han Soo; Deen, John; Detmer, Susan; Torremorell, Montserrat

For histopathology, the tissues were fixed in 10% buffered formalin and paraffin-embedded by standard techniques. Tissue sections were stained with hematoxylin and eosin and examined microscopically for histopathologic changes. Lung sections were examined for bronchiolar epithelial changes, and peribronchiolar and alveolar inflammation. Lung sections were given a score from 0-3 to reflect the severity of bronchial epithelial injury based on previously described methods [42] . The lung sections were scored according to the following criteria: 0, no significant lesions; 1, a few airways affected with bronchiolar epithelial damage and light peribronchiolar lymphocytic cuffing often accompanied by mild focal interstitial pneumonia; 1.5, more than a few airways affected (up to 25%) often with mild focal interstitial pneumonia; 2, 50% airways affected often with interstitial pneumonia; 2.5, approximately 75% airways affected, usually with significant interstitial pneumonia; 3, greater than 75% airways affected, usually with interstitial pneumonia. Additionally, the proportion of airways affected in ten microscopic fields at 20 X magnification was also recorded. A single pathologist examined all slides and was blinded to the treatment groups.