THE REMOVAL OF PHAGES T1 AND PP7, AND POLIOVIRUS FROM FLUIDS WITH HOLLOW-FIBER ULTRAFILTERS WITH MOLECULAR-WEIGHT CUTOFFS OF 50000, 13000, AND 6000

We tested the ability of hollow-fiber ultrafilters with molecular weig ht cut-offs (MWCOs) of 50 000, 13 000, and 6000 to remove and detect v iral agents (phage T1, 50-150 nm, phage PP7, poliovirus. 28-30 nm) fro m ultrapure water, 0.85% saline with 1% trypticase soy broth, and Dulb ecco's modified Eagle minimum essential medium with 10% fetal bovine s erum (DMEM-10. Virus diluted in saline and DMEM-10 were tested to eval uate filter performance under conditions that minimize the adsorption of viral particles to the filter matrix. During filtration, the retent ate was returned to the input reservoir, and the permeate was removed to a separate vessel. Thus, the virus concentration in the feed increa sed over the course of filtration. Filter performance was evaluated by comparing the concentration of infectious virus in the initial virus suspension with the virus concentration in the permeate and retentate. Very efficient removal of phages T1 and PP7 was observed with the fil ters with MWCOs of 13 000 and 6000 (titer reduction >7 logs) for all t hree fluids tested. No poliovirus was detected in the permeate of the ultrafilters with MWCOs of 13 000 or 6000 (titer reduction >6 logs). T hese results indicate that the ultrafilrers with MWCOs of 13 000 and 6 000 were very effective in removing small viral particles (25-30 nm) b y size exclusion. The recovery efficiency of the virus in the retentat e varied by fluid type. However, filtration with virus diluted in DMEM -10 resulted in consistent recovery of the viruses tested. The results suggest that these ultrafilters may have the dual potential of removi ng viral contaminants from fluids and concentrating virus in the reten tate.