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SUMMARY A number of recent reports concerning the inhibitory action of sulphated polysaccharides on d strains of poliovirus prompted a reinvestigation of the factors involved. It was found that polyglucose compounds in agar are not released in concentrations sufficient to inhibit viruses under the overlay conditions used for suppressing d strains of poliovirus. Furthermore, sulphated polyanions in agar cannot be the critical factor, since d strains of poliovirus are also suppressed under other solidifying agents (starch gel and methylcellulose) which are free of sulphated polyglucose. Purified agar free of sulphated polysaccharides, used with medium containing a low bicarbonate concentration attains the same high pH after equilibration as regular agar (containing polyanions) made up with high concentrations of bicarbonate, and it is this high pH which appears to explain the ready growth of d strains of poliovirus.
Wallis et al. (1968) studied this question.