| Abstract: | Millipore-filtered herpes virus and a hyperimmune rabbit serum were reacted to analyze the unneutralizable persistent fraction (PF). When the PF was serially diluted with antibody-containing diluent, the plaque-formers reduced in number. When the serial dilutions were made with antibody-free diluent, plaque numbers were disproportionately smaller in lower dilutions. The PF filtered through a 0.22μ Millipore membrane showed only a slight loss of infectivity, but a further incubation of the filtrate at 37 C resulted in a marked reduction of titer. This effect was less pronounced when the membrane porosity was larger. Additional virus given to the PF was quickly neutralized by excess antibody. On the other hand, dilution of the virus–serum mixture followed by incubation at 37 C or sonication did not further reactivate the virus. When neutral complexes were sedimented by ultra-centrifugation and resuspended in antibody-free diluent, a partial reactivation slightly exceeding the usual PF level occurred with a concomitant release of antibody. It is proposed that the PF may be free virus resulting from reversible virus-antibody reaction. |
