Viruses of Poliomyelitis an Immunological Comparison of Six Strains* by James

During the past 5 years we have collected 6 strains of the virus of poliomyelitis and we have observed certain characteristics which differentiate some from the others. Two of these strains (namely those isolated in New York and Connecticut in 1931) have already been compared with another pair of them representing more widely known strains of the virus (1). I t has seemed justifiable, however, to pursue the comparisons further because the strain differences are considerable and poorly understood. In poliomyelitis there is as yet no standard or recognized method whereby strains of the virus may be classified. Their properties are manifold and there is no indication as to which is of the greatest taxonomic importance. Thus, an outstanding property of a given strain is that of maximum virulence for the monkey on intracerebral inoculation. However, virulence by this route does not necessarily parallel virulence by the nasal or the cutaneous routes, to which latter fact one of our strains bears witness (2). But for purposes of classification, besides comparing virulence by different routes of inoculation, it is obvious that one should use the immunological approach, for it is generally the method of choice in classifying substrains of infectious agents. I t has, nevertheless, been evident from the start that certain features of the immunology of experimental poliomyelitis render this approach difficult. I t is recognized, for instance, that although