Analysis of Coxsackie B Virus Protein Synthesis
Coxsackie B viruses (CBV) are members of the picornaviridae. CBV are responsible for a variety of human infections and the specific interest in this laboratory is there association with myocarditis and chronic fatigue syndrome. It has been proposed that CBV-induced myocarditis can on occasions develop into a chronic virus infection. In the case of chronic fatigue syndrome, although there is no single cause recognised for the illness, a chronic virus infection (in particular CBV) has been proposed as one pathogenic mechanism. The research in our laboratory is concerned with determining the mechanism of persistent CBV infection using in vitro grown cell lines. In this research, 2D-PAGE is being used to characterise the virus proteins and to determine the response of the cells to virus infection. The cellular response to CBV infection is being examined for both lytically and persistently infected cells. Cell lines persistently infected with CBV have been established using human rhabdomyosarcoma cells and T cells which show characteristics of T helper cells (MOLT-4 and Jurkat cells).
In susceptible cells the virus undergoes a lytic infection and there is a switch from cellular protein synthesis to virus protein synthesis. By approximately 5 hours post-infection the majority of the proteins synthesised in the virus-infected cells are those encoded by the virus (Figure 1 ca. 70k). Under these conditions up to 16 virus induced proteins can be regularly detected which have been designated on the basis of their apparent molecular weights (Figure 2 ca. 70k). The experimentally determined isoelectric points and apparent molecular weights of the major virus-induced intracellular proteins are presented in Table 1. In contrast to the inhibition of cellular protien synthesis during lytic CBV infection, persistently infected cell lines established in vitro show no detectable changes in cellular protein synthesis and only low levels of virus proteins can be detected. The most consistent explantion for this observation is that only a small proportion of the cells infected with virus may be present at one time and the uninfected cells in the population mask the response of the infected cells to the presence of the virus.
Virus variants have been detected in association with persistently infected cell lines. These virus variants were identifed on the basis of variation in the electrophoretic mobilties of their proteins (comapred to the parental virus) when analysed by either 1- or 2-dimensional electrophoresis. The relase of virus variants with mutations in one or more virus proteins was consistently found with each of the persistently infected cell lines established in this laboratory. The most extensive studies have been carried out on persistent CBV infections of Rd cells in which mutations were demonstrated in two of the major intracellualr virus-induced proteins, p39 and p33 (Figure 3 ca. 70k).
Last Modified: Sunday, March 09, 1997