Demonstration of virus particles within immune complexes by electron microscopy.

A method has been developed to detect virus particles within immune complexes by electron microscopy (VICEM test). Radioiodinated or unlabeled adenovirus type 2 immune complexes (IC) in human serum were used to determine the optimal conditions. Best results were obtained when the immune complexes were precipitated with 5% polyethylene glycol 6000, adsorbed with 0.5% of protein A-containing Staphylococcus aureus (Cowan 1) and eluted, with brief sonication, in 2 M propionic acid. When the eluate was examined by the pseudoreplica method of electron microscopy, morphologically intact viruses, concentrated over five-fold and free from background serum proteins, were readily demonstrated. The method is applicable to virus IC with a wide-range of antigen-to-antibody ratios and requires a minimum of 10(4)--10(5) virus particles. This method should be useful for the characterization of IC in clinical specimens obtained from patients with viral infections and for the possible demonstration of viral agents in immune complex diseases of unknown etiology. A modification of the technique can also be used for the rapid serological identification of viruses by electron microscopy, as exemplified by studies using adeno- and herpes simplex viruses.