Adenine arabinoside inhibition of adenovirus replication enhanced by an adenosine deaminase inhibitor

Therapeutic Basis of Vidarabine on Adenovirus-Induced Haemorrhagic Cystitis

When adenovirus causes haemorrhagic cystitis in immunocompromised patients, vidarabine is used for its treatment because therapeutic choice is limited. Although vidarabine has been reported to be effective for these patients, its therapeutic basis has not yet been established. Vidarabine dose-dependently inhibited viral replication as assessed by a yield reduction assay. Viral protein synthesis was dose-dependently inhibited by vidarabine but not at all by acyclovir, and the degree of inhibition by vidarabine was different for each of the viral proteins, ranging from 0–40% of the untreated control. These results indicated the specificity and mechanism of action of vidarabine against adenovirus. The concentration of vidarabine and its metabolite in the bladder is suggested to exhibit effective anti-adenoviral activity in suppressing the replication of adenovirus. Thus, our results support vidarabine therapy as a possible candidate for adenovirus-induced haemorrhagic cystitis in immunocompromised patients.

Adenovirus infections in transplant recipients

Adenoviruses are increasingly recognized as contributors to morbidity and mortality among stem cell and solid-organ transplant recipients. Clinical presentations range from asymptomatic viremia to respiratory and gastrointestinal disease, hemorrhagic cystitis, and severe disseminated illness. The limited clinical data available support the use of cidofovir for many of these illnesses. Prospective studies are needed to better understand the pathogenesis of and therapeutic options for adenoviral infections in this patient population.

Mechanism of antiviral activity of (XyloA2'p)2XyloA

(XyloA2'p)2xyloA, the xyloadenosine core analog of the interferon mediator 2-5A [ppp(A2'p)2A], was found to exhibit potent antiviral activity against herpes simplex viruses 1 and 2 (D. A. Eppstein, J. W. Barnett, Y. V. Marsh, G. Gosselin, and J. -L. Imbach (1983a) Nature (London) 302: 723-724). This xylo 2-5A core analog was over 100 times more stable to phosphodiester cleavage than was parent 2-5A core in cell-free extracts, which was originally thought to have contributed to its increased activity. However, we have now shown that the xylo 2-5A core does not activate the 2-5A-dependent endonuclease, and, additionally, that its mechanism of action is different from that of parent 2-5A core, even though it too does not activate the endonuclease. In fact, the mechanism of action of xylo 2-5A core apparently involves its degradation to monomer units, which then exert the antiviral effect. The enhanced antiviral activity of xylo 2-5A core (normalized to monomer-unit equivalents) as compared to that of xyloadenosine appears to be mediated through a slow release of xyloadenosine monomer units (i.e., xyloAMP). XyloAMP is resistant to inactivation by deamination, and thus intracellular xyloAMP should have increased antiviral activity compared to an equivalent concentration of xyloadenosine, which is subject to rapid inactivation by deamination.

Combined interaction of antiherpes substances and interferon beta on the multiplication of herpes simplex virus

The inhibition of herpes simplex virus type 1 (strain McIntyre) by two anti-herpes substances applied in combination was studied by means of a CPE inhibition method In Vero cell microcultures. The following substances were studied: AraA monophosphate, thymine arabinoside, ethyldeoxyuridine, acycloguanosine (acyclovir). 3-fluorothymidine, phosphonoformic acid. Most substance pairs showed a moderate degree of synergism. Two additive interactions and one case of antagonism was observed. Human fibroblast interferon, combined with the antiherpes substances, showed an additive interaction with AraAMP, but synergism with the others.