FIG 5.

Representative histological images from the lungs of marmosets challenged by one of two strains of MERS-CoV by different routes of challenge. (A) A low-magnification hematoxylin and eosin (H&E)-stained image from animal 110W following challenge with strain EMC/2012 by the oral route shows mild thickening of alveolar septa and lymphocytic infiltration into the perivascular location (*) (above normal limits). (B) A high-magnification H&E-stained image from animal 56W following challenge with strain England 1 by the intranasal route shows expanded alveolar septa (*) infiltrated by neutrophils with mild exudation into the alveolar spaces (arrow). (C) This tissue was further characterized by Gram Twort staining and shows no evidence of bacterial colonies in areas of neutrophilic exudation. (D and E) Immunohistochemical staining with MAC387 shows an increase of cells in the alveoli (D), and immunohistochemical staining of CD3 shows scattered T lymphocytes in areas of alveolar thickening of septa (E). (F) A high-magnification H&E-stained image from animal 55W following challenge with strain EMC/2012 by the aerosol route shows lymphocytic infiltration into the perivascular location (*) (above normal limits). (G) H&E staining of the terminal bronchiole from animal 146X euthanized 2 days following challenge with the concentrated stock of MERS-CoV by the aerosol route shows exudation. (H) This sample was further characterized by immunohistochemical staining with MAC387 and shows an accumulation of cells in lesioned areas with exudation and septal infiltration. (I) Phosphotungstic acid hematoxylin (PTAH) staining was also performed on a lung section of the other animal euthanized 2 days following challenge with the concentrated stock of MERS-CoV (animal 130X) to show fibrin in the alveolar exudation.