Extent of hepatitis E virus elimination is affected by stabilizers present in plasma products and pore size of nanofilters

Background and Objective To investigate the physico-chemical properties of hepatitis E virus (HEV) with regard to inactivation/removal, we have studied four isolates with respect to sensitivity to heat during liquid/dry-heating as well as removal by nanofiltration. Materials and Methods Hepatitis E virus in an albumin solution or phosphate-buffered saline (PBS) was liquid-heated at 60 degrees C for a preset time. HEV in a freeze-dried fibrinogen containing stabilizers was also dry-heated at 60 or 80 degrees C for a preset time. In addition, to clarify the removal of HEV, the purified virus in PBS was filtered using several types of virus-removal filter (nanofilters) that have different pore sizes. HEV infectivity or genome equivalents before and after the treatments were assayed by a semiquantitative cell-based infectivity assay or quantitative polymerase chain reaction assay, respectively. Results Hepatitis E virus isolates in albumin solutions were inactivated slowly at 60 degrees C for 5 h and the resultant log reduction factor (LRF) was from 1.0 to >= 2.2, whereas the virus in PBS was inactivated quickly to below the detection limit and the LRF was >= 2.4 to >= 3.7. The virus in a freeze dried fibrinogen containing trisodium citrate dihydrate and L-arginine hydrochloride as stabilizers was inactivated slowly and the LRF was 2.0 and 3.0, respectively, of the 72 h at 60 degrees C, but inactivated to below the detection limit within 24 h at 80 degrees C with an LRF of >= 4.0. The virus in PBS was also confirmed as to be approximately 35 nm in diameter by nanofiltration. These results are useful for evaluating viral safety against HEV contamination in blood products. Conclusion The sensitivity of HEV to heat was shown to vary greatly depending on the heating conditions. On the other hand, the HEV particles were completely removed using 20-nm nanofilters. However, each inactivation/removal step should be carefully evaluated with respect to the HEV inactivation/removal capacity, which may be influenced by processing conditions such as the stabilizers used for blood products.