Immunofluorescent staining of influenza virus antigen in fixed and paraffin-embedded tissue of experimentally infected hamsters.

Sections of formalin-fixed, paraffin-embedded tissue of experimentally influenza virus-infected hamsters were treated with 0.25% trypsin and tested for virus antigen by indirect immunofluorescent staining. The results were comparable to those obtained with aceton-fixed cryo-microtome sections. As far as we know, this is the first description of influenza virus demonstration in formalin-fixed, paraffin-embedded tissue after reactivation by trypsin-treatment. This technique may be useful for influenza virus detection in human autopsy cases. It allows an etiological diagnosis even when fresh tissue for cryocut sections or virus cultivation is not available.