Use of the avidin-biotin-peroxidase complex immunocytochemical procedure for detection of Rift Valley fever virus in paraffin sections of mosquitoes.

The avidin-biotin-peroxidase complex (ABC) immunocytochemical procedure was used to locate Rift Valley fever (RVF) virus antigen in infected Aedes albopictus C6/36 cultured cells and in serial paraffin sections of intrathoracically-injected Egyptian Culex pipiens. Fixation of the cultured cells in formaldehyde or periodate-lysine-paraformaldehyde, and fixation of whole mosquitoes with formaldehyde resulted in good preservation of morphology and excellent differential staining between uninfected and infected specimens. Two primary antibodies against RVF virus were tested on the cultured cells: a polyclonal rabbit antiserum and a mixture of mouse monoclonal antibodies. Only the mouse monoclonal antibody mixture was tested on the Cx. pipiens. Specific staining of tissues in paraffin sections occurred at dilutions as high as 1:5,000. In both cultured Ae. albopictus cells and sections of Cx. pipiens, only the cytoplasm was positive for antigen. A preliminary list of tissues in Cx. pipiens that exhibited specific or nonspecific staining is given.