Abstract # A-61

SY5Y Human Neuroblastoma Cells Pretreated with Gamma-Interferon: An In Vitro Tool for Discriminating Between Attentuated Vaccine, Vaccine-revertant and Wild Type Poliovirus Strains. J. Ridge, J. Enterline, R. Taffs and D.Asher. CBER, FDA, Bethesda, MD.

We compared the yields of RSO+OPV3 vaccine (Sabin), a vaccine-revertant isolate (DMPg35a) and a wild-type (VR -62 (Leon)) PV strain propagated in SY5Y cells pretreated for 4-9 days with 500 or 1000 U-gamma-IFN or with control medium. We found:

  1. IFN inhibited replication of all three strains of PV;
  2. The dose of IFN and the duration of pretreatment affected the degree of inhibition;
  3. Regardless of dose or duration of treatment, the attentuated OPV strain was always the most inhibited;
  4. Yields of PV in untreated cultures infected with Sabin and revertant strains differed by less than 0.5 log10, while in the IFN-treated cultures yields of revertant virus were consistently 0.5 log10 greater than those of Sabin virus;
  5. Yields of the wild-type strain were at least 0.3 log10 greater than those of the revertant strain, both in untreated and IFN-treated cultures.

Statistical evaluation of our data suggests that the reduction in PV yields induced by IFN treatment are significant and may provide the basis for an in vitro assay to discriminate between attentuated vaccine and neurovirulent strains of PV3.