Abstract
Discussion and summary
Some of the factors that are known to affect the agglutination of various erythrocytes by viruses are the age of the donor animal, the hydrogen ion concentration of the diluent and the temperatures at which erythrocytes are allowed to sediment. The results reported here indicate that these factors, either singly or in combination, also affect the agglutination of human erythrocytes by enteroviruses known to possess this property.
Cord erythrocytes or diluents of specific hydrogen ion concentration are not usually necessary for demonstration of enterovirus hemagglutinins. However, the use of these cells and of diluents other than those buffered at or above pH 7.0 has enabled us to detect hemagglutinating activity where it existed in what might be termed a “borderline state.” This was exemplified by our demonstration of hemagglutination by ECHO virus type 24. Other reports(15,29,30) have indicated that the pH optimum for hemagglutination reactions with certain enteroviruses was other than at pH 7.0 to 7.3. Temperature has been shown to be the determining factor in whether or not hemagglutination is demonstrable in an unbuffered diluent with ECHO virus types 3, 11, 13 and 30, with Coxsackie group A types 21 and 24 and with Toluca-1 and JV-9 viruses.
While several reports have appeared concerning utilization of hemagglutination and HI reactions to identify enteroviruses, there has been little effort to determine the optimal environmental conditions necessary to propagate enteroviruses in order to produce maximal titers of their hemagglutinins. We have been able to demonstrate hemagglutination regularly with tissue culture fluids of nearly all the serotypes utilized in these experiments, but difficulty has been encountered with a few serotypes such as the prototype strain of ECHO virus type 24. We have consistently been able to produce hemagglutinins with other strains of this same serotype.
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