Virus-like particles associated with reverse transcriptase activity in acute sporadic non-A,non-B hepatitis

Reverse transcriptase and corresponding activity-blocking antibody for monitoring SIVsm infection in macaques

A nonradioactive reverse transcriptase (RT) assay was used to measure RT activity in serum during the viremia peak associated with primary infection and for measuring the generation and maintenance of RT activity-blocking antibody (RTb-ab) titers during and after seroconversion in SIV-infected macaques. The RT assay was compared to an antigen capture immunoassay designed for HIV-2/SIVsm and was found to be approximately 40 times more sensitive in detecting SIVsm in serum from infected macaques. The RT assay detected RT activity in serum corresponding to levels from 3 pg/ml. Earliest detection of viral replication using the RT assay was on day 6-8, with a peak at day 10 (up to 8000 pg/ml). The earliest detection of RTb-ab was seen on day 17-23, with established RTb-ab titers by day 29, followed by increasing titers of 15,000-120,000 by day 62-77. The usefulness of RT and RTb-ab for monitoring the course of SIV infection in monkey models is discussed.

Identification of hepatitis C virus by immunoelectron microscopy

Sequencing of the hepatitis C virus (HCV) has provided a better understanding of the natural history, immunology, and epidemiology of this virus. However, the morphology of HCV has not been definitively characterized. In this study, through a sequence of concentration processes, virus-like particles were isolated from human serum and liver tissue, visualized by transmission electron microscopy and identified as hepatitis C virion by immunoelectron microscopy. Spherical flavi-like virus particles, approximately 70 nm in diameter, were observed in the fraction with 1.04-1.12 g ml-1 sucrose density and bound to immunogold particles with monoclonal antibodies (mAb) against hepatitis C. The nucleocapsid of the particles, which were 50 nm in diameter, appeared to be icosahedral in structure and surrounded by an envelope covered with surface projections. A 'tadpole' form of particles was also observed. The findings indicate that the low buoyant density in sucrose and the morphological features of the hepatitis C virion are consistent with the characteristics of flaviviruses and pestiviruses.