A 2',5'-oligoadenylate analogue inhibits murine hepatitis virus strain 3 (MHV-3) replication in vitro but does not reduce MHV-3-related mortality or induction of procoagulant activity in susceptible mice

Abstract

Exposure of inbred mice to murine hepatitis virus strain 3 (MHV-3) causes a strain dependent spectrum of disease symptoms which correlates with induction of procoagulant activity (PCA) by macrophages. Previous studies have demonstrated a role for intefferons in resistance to MHV-3 infection. These cytokines have both antiviral and immunoregulatory effects which may be crucial for MHV-3 resistance. One of their antiviral effects is the ability to induce 2',5'-oligoadenylate (2-5A) synthetase leading to activation of the latent endoribonuclease RNase L. Once activated, RNase L degrades ssRNA thereby inhibiting viral-induced protein synthesis. These studies were undertaken to determine the effects of Oragen 0004 (Oragen), an RNase L activating 2-5A analogue, on MHV-3 replication and induction of PCA in vitro and on the course of MHV-3 infection in susceptible BALB/cJ mice in vivo. Oragen inhibited MHV-3 replication in peritoneal macrophages derived from resistant A/J and susceptible BALB/cJ mice in a dose-dependent fashion. Concentrations of Oragen greater than 110 lag/2 x 106 macrophages decreased viral replication by greater than 89% in peritoneal macrophages in vitro obtained from both BALB/cJ and A/J mice and by 86% in livers from MHV-3qnfected mice in vivo. However, Oragen failed to inhibit induction of PCA following in vitro exposure of BALB/cJ mice-derived peritoneal macrophages to MHV-3 and failed to prevent the development of fulminant hepatitis in BALB/cJ mice in vivo. Thus, these studies demonstrate clearly that induction of 2-5A synthase and inhibition of viral replication is not sufficient to prevent MHV-3-related hepatocellular injury, and these data further support the role of PCA in the pathogenesis of MHV-3 infection.

Antisense Morpholino-Oligomers Directed against the 5′ End of the Genome Inhibit Coronavirus Proliferation and Growth†

“…Attempts which have been most successful include immunotherapy with various combinations of interferon (14,19,60) or with neutralizing antibodies or antibody fragments (41,62). Limited data indicate mixed anticoronaviral activity for nucleoside analogs including riba- virin (11,16,18,35,44,59,71,78,82) and an assortment of other small molecules (8,10,13,55,69,80). Corticosteroid treatment has proved generally ineffective against coronaviruses (3,4).…”

RNase L Mediated Protection from Virus Induced Demyelination

“…In vitro, the dual liver and neurotropic MHV-A59 strain does not elicit degradation of 18S and 28S ribosomal RNA, suggesting the absence of RNase L activation in HELA cells [18]. However, administration of an RNase L agonist inhibited replication of the hepatotropic MHV-3 strain in peritoneal macrophages in vitro and in liver in vivo [19]. Nevertheless, reduced viral replication via RNase L function in vivo was insufficient to prevent liver necrosis and death.…”

Immunopathological aspects of coronavirus infections

“…A major mechanism mediating an antiviral effect is elicited through 2-5 adenylate synthetase, which activates RNase L. This endoribonuclease activity can impair the synthesis of viral RNA by degradation of single-stranded RNA. Compounds that stimulate RNase L interfere with virus replication in macrophages [21]. However, MHV-3-induced PCA activity is not diminished and, thus, these substances did not prevent necrotic hepatitis.…”