Several studies on cross-neutralization of the lower human adenovirus types have been published (1--6). No reports, however, have been made on types 12 and 15 through 28 except those included in the original description of these types (3,7,8). In most of these papers there has been no mention of the behavior of preimmunization sera of the animals used for immunization, so that the nature of the observed cross-reactions often remains doubtful.In our laboratory rabbit immune sera have been prepared against human adenovirus types 1 through 28, and the results of the observed cross-neutralizations are reported. Some known antigenic relationships were confirmed and some others were newly established. Preimmunization sera were regularly included in tests, whenever a positive neutralization with the respective immune serum was present.
Materials and MethodsViruses. Prototype strains were used for animal immunization and for neutralization tests for all types with the exception of type 12, for which a strain isolated by Dr. G. Enders-Ruckle (strain Marburg) was substituted (9). This strain yielded much higher infectivity titers than the prototype. Viruses were grown in tteLa cell cultures with a maintenance medium containing Hanks' solution, 0.50 casein hydrolysate, and 5% calf serum. Cultures showing complete cytopathic effect (CPE) were frozen and thawed three times and centrifuged ~o remove cell debris. Titrations were performed in HeLa cell culture tubes with a final reading 8 days after inoculation. Virus stocks exhibiting a titer of at least 108.5 TCIDs0 per ml., as measured by this method, were considered satisfactory for immunization. This titer level could not be obtained with type 8 and 18 virus. Consequently stocks of these viruses were concentrated 10 times by ultraeentrifugation.* Aided by grants of the Deutsche Forsehungsgemeinsehaft.
Prototype adenoviruses and their hemagglutinins of ROSEN'S 1 group II were studied by adsorption to rat and human red blood cells and by straight and cesium chloride density gradient ultracentrifugation. Density gradient experiments showed the presence of a hemagglutinin separable from the infectious virus particles which agglutinates both rat and human cells for virus types 9, 10, 13, 19, 26, and 27. In addition, types 10, 19, and 27 have a second hemagglutinin associated with the infective particles which agglutinates rat blood cells only. Type 9 (and possibly type 8) virus has a virusbound hemagglutinin which agglutinates both kinds of blood cells. The viruses types 15, 17, 22, and 24 with hemagglutinins for rat blood cells only have two hemagglutinins, one of them associated with the virus particles. The results with type 23 were variable. Straight ultracentrifugation experiments showed a surprisingly incomplete sedimentation of the infective particles for most of the virus types studied.Differences in the resistance of various hemagglutinins to trypsin and/or heating are demonstrated.
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