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Suppression of macrophages in mice by treatments with silica or auro-thiomalate (Myocrisin) reduced production of serum interferon by polyriboinosinic acid:polyribocytidylic acid by 85 to 90%, indicating that this double-stranded polynucleotide caused interferon production primarily in macrophages. Suppression of macrophages in mice by silica or Myocrisin treatment did not significantly affect the susceptibility of mice to encephalomyocarditis virus, although at virus doses around 20 times the 50% lethal dose they died about 48 h earlier. Macrophage interferon protected mice from encephalomyocarditis virus infection at much lower doses than fibroblast interferon, and treatment of mice with silica or Myocrisin abolished the protection conferred by macrophage interferon, whereas these treatments had a much smaller effect on the protection afforded by fibroblast interferon. The requirement for macrophages for interferon to be effective in mice can explain why macrophage suppression can cause normally nonlethal viruses to kill adult mice.

Bacteria-derived human leukocyte interferon (IFN) subtypes, IFN-alpha A, -alpha B, and -alpha D, and two hybrid IFNs, IFN-alpha AD and -alpha DA, were examined for both in vitro and in vivo antiviral activity. Two of these materials in highly purified form (IFN-alpha D and -alpha D) protect mice against lethal doses of encephalomyocarditis virus infection. A single dose of 1 microgram of protein of IFN-alpha D 3 h before infection conferred protection in both BDF1 and CD-1 mice against encephalomyocarditis virus infection, and multiple treatments with IFN-alpha D or IFN-alpha AD extend the mean survival time of infected mice. On a weight basis, IFN-alpha AD was approximately 100-fold more effective than IFN-alpha D. There is a direct correlation between the antiviral activity of the various human IFN species in L-929 cells and in mice for both single and multiple treatments before infection, but none of the cloned human IFN subtypes were effective when administered 24 h after infection. Mixtures of the two parental materials, IFN-alpha A and -alpha D, were not as protective as the hybrid molecule IFN-alpha AD, suggesting that IFNs with unique and altered species specificity can be produced by recombinant DNA methods.

The efficacy of a novel consensus form of human alpha interferon designated IFN-alpha Con1 was evaluated against herpesvirus infections in vitro and in vivo. At comparable antiviral concentrations, natural lymphoblastoid IFN, IFN-alpha Con1, the molecular subtype IFN-alpha, and the hybrid IFN-alpha AD(Bgl) obtained by recombinant DNA methods conferred similar protection against herpes simplex virus type 1 and type 2 (HSV-2) infections of human cells in vitro. Whereas 7 X 10(5) U of IFN-alpha AD(Bgl) administered in 7 intraperitoneal (i.p.) doses between -4 and 96 h relative to infection protected 90% of mice from a lethal HSV-2 infection, a similar treatment regimen with IFN-alpha Con1 conferred no protection. Systemic HSV-2 infection of hamsters was rapidly lethal, but a single i.p. treatment with 10(6) U of either IFN-alpha Con1 or IFN-alpha AD(Bgl) was highly effective and protected 90 and 75% of animals, respectively, when given 6 h before infection; treatment with IFN-alpha Con1 protected 45% of animals when administered 10 h after infection. In addition, IFN-alpha Con1 was highly protective against acute cervicovaginal HSV-2 infection of hamsters when administered either in a single i.p. dose of 10(6) U at -6 or 10 h relative to infection or in multiple i.p. doses of 10(6) U between -6 and 120 h relative to infection. Protection was manifested by a delay in the onset of and a reduction in duration of infection, a reduction in the number of positive cervicovaginal infections, and an increase in the survival rate.

The pharmacokinetics of two human leukocyte interferon (IFN) subtypes (IFN-alpha A and IFN-alpha D) and two molecular hybrids [IFN-alpha AD(Bgl) and IFN-alpha AD(Pvu)] was studied in rats receiving single i.v. injections, 5.0 X 10(6) I.U./kg, of these materials. All four preparations were highly purified and resulted in plasma decay curves with similar elimination half-lives of 95.3 +/- 13.5 min. The four IFN-alpha subtypes investigated showed differences when their clearances are compared, suggesting that the 13 residue differences between amino acids 92 and 165 affect the clearance. The fact that only IFN-alpha D has an apparent volume of distribution (Vd beta) of 12.9 +/- 3.4 liters/kg whereas the other three IFN-alpha subtypes have Vd beta of 5.7 +/- 1.0 liters/kg suggests that the amino acid differences between residues 1 and 61 affect the Vd beta. Only in the case of IFN-alpha D did functional nephrectomy significantly (P = .02) increase the apparent volume of distribution at steady state. Functional nephrectomy before i.v. injection resulted in a 4-fold decrease in IFN-alpha AD(Bgl) and IFN-alpha AD(Pvu) clearance, an 8-fold decrease in IFN-alpha A clearance and a 10-fold decrease in IFN-alpha D clearance. The elimination half-life of each interferon was unchanged after nephrectomy. Intramuscular administration of the IFN-alpha subtypes in rats produced low plasma concentrations. IFN-alpha D peaks at 39 +/- 10 I.U./ml of plasma, whereas IFN-alpha A reaches 201 +/- 53 I.U./ml, IFN-alpha AD(Bgl) reaches 396 +/- 47 I.U./ml and IFN-alpha AD(Pvu) results in a maximum plasma concentration of 747 +/- 66 I.U./ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Human Daudi lymphoblastoid cells, which are highly sensitive to the antiproliferative action of human leukocyte alpha-interferon (IFN-alpha), and IFN-resistant and IFN-sensitive Daudi subclones (Cl2 and Cl1, respectively), contain 2300 (Kd = 20 X 10(-12) M), 3000 (Kd = 45 X 10(-12) M), and 3700 (Kd = 52 X 10(-12) M) IFN-alpha binding sites per cell, respectively. Thus, these IFN-sensitive and IFN-resistant cells have similar numbers of high-affinity IFN-alpha receptors. IFN-receptor complexes that are insoluble in Triton X-100 accumulate in IFN-sensitive but not in IFN-resistant cells. The ligand-induced accumulation of Triton-insoluble complexes in IFN-sensitive cells was inhibited by cytochalasin B. This suggests that the solubility change of IFN-receptor complexes results from their interaction with the cytoskeletal matrix. The dissociation of IFN-alpha from IFN-sensitive and IFN-resistant cells can be resolved into fast and slow components. IFN-alpha dissociates more slowly from IFN-sensitive cells than from IFN-resistant cells. Very slow dissociation of IFN-alpha from Triton-insoluble complexes correlates with this difference. These observations suggest that IFN-receptor complexes become coupled to the cytoskeletal matrix in IFN-sensitive but not in IFN-resistant cells, and that such interaction is an important element in the mechanism of the antiproliferative action of IFN-alpha on Daudi cells.

Treatment of mice with polyinosinic acid . polycytidylic acid [poly(I) . poly(C)] 6 h before infection and once daily on days 1, 2, 3, 4, 7, and 10 after infection with encephalomyocarditis virus was found to confer no additional protection as compared with a single treatment 6 h before infection. When complexed with a colloid formed between carboxymethylcellulose and polylysine, poly(I) . poly(C) conferred significant additional protection with the multiple treatment regimen compared with a single treatment of 6 h before infection. The additional antiviral activity of multiple treatments could not be entirely attributed to interferon induction by the complexed form of poly(I) . poly(C), because free and complexed poly(I) . poly(C) both caused hyporesponsiveness to interferon induction after multiple treatments. However, mice protected against encephalomyocarditis virus infection by multiple treatments with the colloidal complex form of poly(I) . poly(C) showed a significant increase in resistance to reinfection, and this was attributable to adjuvant effects of the colloidal complex form of poly(I) . poly(C). The contribution of interferon induction and adjuvanticity of the poly(I) . poly(C) formulations varied with the times of treatment relative to infection, the dose of polynucleotide material, and the virus dose.