Removal of influenza A virus, phage T1, and PP7 from fluids with a nylon 0.04‐μM membrane filter

We tested the ability of a 0.04-μm nylon membrane filter to remove viral agents (influenza A virus, 80–120 nm; phage T1, 50–150 nm; and phage PP7, 25 nm) from the following media: ultrapure water (UPW), Dulbecco's modified Eagle minimum essential medium (DMEM), gelatin phosphate (GP), DMEM with 10% (DMEM-10) fetal bovine serum (FBS), and 100% FBS. When challenged with at least 3.0 × 107 plaque-forming units/mL, no influenza A virus was detected downstream of the filter with any of the fluids tested. The titer reduction (Tr) was determined using the equation: . Higher concentrations of phage T1 were removed from UPW (Tr = 1.6 × 106) and DMEM (Tr = 1.1 × 106) than from GP (Tr = 9.3 × 103), DMEM-10 (Tr = 1.5 × 102), and 100% FBS (Tr = 2.4 × 102). Phage PP7 was removed in significant numbers only in ultrapure water (Tr = 8.5 × 104). The results indicate that adsorption enhanced the titer reduction in fluids containing low levels of protein. The titer reduction in DMEM-10 and 100% FBS may reflect the sieving properties of the 0.04-μm filter. As expected, a much smaller Tr was observed in the filtrate of the 0.2-μm filters, compared to the 0.04 μm filters. In contrast to the 0.04-μm filter, no increase in Tr was detected when the 0.2-μm filters were challenged with virus diluted in UPW compared with virus diluted in GP. These results suggest that the 0.04-μm filter has greater adsorptive properties than the 0.2-μm filter. © 1994 by John Wiley & Sons, Inc..