The A.P.C. viruses.

The name A.P.C.-short for adenoidal-pharyn-geal-conjunctival-has been given to a recently-described group of viruses, which have mostly been isolated from tissue cultures of surgically-removed human adenoids and tonsils, and from pharyngeal and conjunctival secretions of patients suffering from acute respiratory infections, and conjunctivitis. These viruses have also been known as A.D. (adenoid-degenerating), A.R.D. (acute respiratory disease), and R.I. (respiratory illness) agents. This last term is currently used by some investigators. History The first report of isolations of viruses of the A.P.C. group appeared in December I953. Rowe et al.1 were studying the growth of surgically-removed human tonsils and adenoids in roller-tube tissue cultures, in the hope that such cultures would prove a suitable medium for the cultivation of the common cold virus. They observed a spontaneous degeneration occurring in many of the epithelial out-growths, and later found that this degeneration could be serially transmitted in other tissue cultures, by passage of fluid from tubes containing the abnormal cells. Further investigation showed that the degenerative effect was due to agents which would pass through bacteria-retaining filters, would not grow on bacteriological media, and caused no recognizable disease in any of the numerous laboratory animals tested. However these agents regularly caused characteristic changes in epithelial-type cells in cultures of numerous normal human and some animal tissues, and also in cultures of the strain HeLa2 of human epidermoid carcinoma cells. These changes were specifically neutralized by antisera produced by hyperimmunizing rabbits against the viruses, but no immunological relationship to any other known group of viruses could be demonstrated. Some human sera, and gamma globulin, also neutralized the cytopatho-genic effect of the viruses, sometimes in high dilutions. The relation of these ' adenoid-degenerat-ing' agents to clinical human illness was so far unknown.