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Intraperitoneal injection of mice with mineral oil, incomplete (IFA) or complete Freund's adjuvant (CFA) increased the interferon response to endotoxin or (poly rI)*(poly rC) administered intravenously 2 days later. After endotoxin administration, circulating interferon titers were increased at several different times of sampling and with a variety of endotoxin dosages. When injection of endotoxin was delayed until 6 to 8 days after the administration of IFA or CFA, interferon production was markedly decreased. Mice treated with CFA and injected with endotoxin 2 days later became more resistant to intranasal vesicular stomatitis virus challenge than mice injected with endotoxin alone. Hyporeactivity to the interferon-inducing capacity of a second injection of endotoxin 2 days after the first injection could not be overcome by administering CFA simultaneously with the first dose. CFA treatment not only raised the serum interferon titers produced by endotoxin, but also increased the number of interferon-forming cells in the spleen after administration of endotoxin in vivo. In addition, CFA enhanced the intravascular clearance of (poly rI)*(poly rC). The possibility that Freund's adjuvant increased the interferon response to endotoxin and (poly rI)*(poly rC) by stimulating the uptake and processing of the interferon inducer by lymphoreticular cells is discussed.
The bicyclic furo[2,3-d]pyrimidine nucleoside analogues represent an entirely new class of fused furopyrimidine derivatives with unprecedented selectivity for varicella-zoster virus (VZV). From extensive structure-activity relationship (SAR) studies, the 6-(p-alkylphenyl)substituted furopyrimidine derivatives Cf 1742 and Cf 1743 emerged as the most potent inhibitors of VZV replication: they were found to inhibit both laboratory VZV strains and clinical VZV isolates at subnanomolar concentrations, while not being toxic to the host cells at 100,000-fold higher concentrations. Although the precise mechanism of action of these compounds remains to be elucidated, it is clear that for their antiviral activity they depend on phosphorylation by the VZV-encoded thymidine kinase. The furo[2,3-d]pyrimidine nucleoside analogues are not susceptible to degradation by human or bacterial thymidine phosphorylase, which may otherwise release the free aglycone. Also, the latter is not inhibitory to dihydropyrimidine dehydrogenase, an enzyme involved in the degradation of thymine, uracil, and the anticancer agent 5-fluorouracil. Further development of the furo[2,3-d]pyrimidine nucleoside analogues as new therapeutic modalities for the treatment of VZV infections (i.e., varicella and herpes zoster) seems highly justified.
