Cytomegalovirus (CMV) is a DNA virus of the human herpesvirus category. CMV infected cells are often large and round. This “owl’s eye” pattern occurs when single, Feulgen-positive, granular amphophilic inclusions swell inside the nuclei. These inclusions are often surrounded by a well-circumscribed “halo” devoid of nuclear substance. Smaller inclusions may be present in the cytoplasm. CMV infects reticuloendothelial cells, stromal cells, and epithelial cells. Disseminated CMV infection can affect many organs including the lungs, kidneys, liver, adrenals, and gastrointestinal tract.
This specific monoclonal antibody cocktail of clones DDG9 & CCH2 (IgG2a, kappa and IgG1, kappa isotypes) react with the CMV infected cell nucleus during immediate-early and early antigen expression. A cytoplasmic reaction may be seen during the late stages of CMV antigen expression when using this monoclonal antibody.
Pretreatment of formalin-fixed, paraffin-embedded (FFPE) tissue sections can be accomplished with enzyme-induced epitope retrieval (EIER) or heat-induced epitope retrieval (HIER). The author's preferred proteolytic enzyme to digest tissue sections when using clones DDG9 and CCH2 is 0.25% pepsin, pH 2.0 for 15 minutes at 37° C. Citrate HIER solution can also be used with very good results. (Ref1)
Image A demonstrates CMV in a highly pigmented section of lung using mouse monoclonal antibody of clones DDG9-CCH2. Aminoethylcarbazole (AEC) is the chromogen. Interpretation of positive results could be problematic with the use of DAB chromogen in this example.
In image B
, CMV infected lung is demonstrated with a CMV cocktail of clones DDG9-CCH2. Alkaline phosphatase (AP) detection and fast red (FR) chromogen is utilized.