The present invention provides a high-resolution membrane-based method for
removing a virus from a manufactured protein-containing solution, the
method being particularly characterized by its capacity to be performed
quickly (i.e., as measured by flux) and efficiently (i.e., as measured by
log reduction value, LRV). Towards such results, the present invention
employs a plurality (i.e., greater than 2) of interfacially-contiguous
asymmetric ultrafiltration membranes, the foremost of which is oriented
with its "tight side" facing downstream. The present invention also
provides a filtration capsule, useful in the conduct of the method,
comprising a pleated tube formed of three interfacially-contiguous
asymmetric ultrafiltration membranes.