Effect of alkaline maintenance medium upon the growth of rabies virus in chick embryo cells

Summary

HEP Flury strain of rabies virus was propagated in chick embryo cells under maintenance media of different pH. It was found that viral growth was better and reached a markedly higher maximum titer when the initial pH of maintenance medium was 8.2 to 9.0 than when it was 7.4. The enhancement of viral growth was not ascribable to mere neutralization of acids produced from infected cells, because the different media became almost equally neutral within an early phase of growth curve. Serial passage of the virus in chick embryo cells using pH 8.2 maintenance medium resulted in altered growth characteristics of the progeny virus; first, the virus so passaged could now grow equally well under alkaline and neutral maintenance media, and, secondly, autointerference observable with the parent virus tended to disappear. Serial undiluted passage of the parent as well as the progeny virus eventually lowered virus yield when neutral maintenance medium was used, but this effect of undiluted passage was eliminated by the use of pH 8.2 maintenance medium.