Differential flotation centrifugation study of hepatitis C virus and response to interferon therapy

Abstract

Hepatitis C virus (HCV) appears to circulate in various forms such as native virion, immune complexes, and nucleocapsids during chronic infections. To determine the association of the physicochemical properties of HCV and its response to interferon therapy in patients with chronic hepatitis C, we examined pretreatment serum samples from 43 patients with HCV RNA who had received interferon therapy, using differential flotation centrifugation in a NaCl solution with a density of 1.063 g/ml. After centrifugation, the ratio of HCV RNA in the top and bottom fractions was determined by the polymerase chain reaction and expressed as T/B. Patients with a sustained response to IFN therapy were found to have higher T/B ratios than transient responders who relapsed after treatment (P < 0.01) and nonresponders (P < 0.01). With regards to HCV genotypes, patients with genotype 1b had higher T/B ratios in the sustained response group than in the nonsustained response groups (P = 0.001), but patients with genotype 2 had a similar distribution of T/B among the 3 response groups (not significant). These findings indicate that the physicochemical properties of HCV affect the effectiveness of interferon therapy, particularly in patients with genotype 1b.

A novel flotation technique for the separation of nonadherent micro-organisms from a substrate

“…The purpose of rinsing is to remove nonattached and weakly attached micro-organisms from the surface and to distinguish between actively adhered cells and the influence of sedimentation. For proper rinsing, the force and direction of flow should be the same in all experiments, and this can be difficult to achieve during manual rinsing (Hijikata et al 1993;Nagasaka et al 1997). Also, inadequate shear stress related to rinsing could cause the release of attached bacteria or cell culture from the bottom of a well.…”

“…This problem could be overcome using a flotation technique for the separation of nonadhered bacteria from the substrate. Flotation with high mass density solutions has been variously used for the separation of DNA fragments (Aprodu et al 2011), viruses (Hijikata et al 1993;Nagasaka et al 1997), isolation of bacteria (Vanittanakom et al 1995;Wolffs et al 2004;Lofstrom et al 2011) or Letters in Applied Microbiology 58, 604--609 © 2014 The Society for Applied Microbiology parasites (Cox 1970). As the mass density of bacteria or other elements is lower than that of the flotation solutions, nonattached bacteria are moved to the surface due to the hydrostatic force.…”