Pyrogenicity of poly I. poly C in rabbits

Comparison of the effects of a synthetic polyribonucleotide with the effects of endotoxin on selected host responses

An injection of a small dose (1 to 50 mug) of synthetic polyriboinosinic acid complexed with polyribocytidylic acid (poly I:poly C) inhibited the induction of tryptophan oxygenase by cortisone acetate; it induced tyrosine amino transferase, and it accelerated the loss of liver glycogen reserves. It also resulted in first a suppression followed by an activation of the reticuloendothelial system as judged by the rates of carbon clearance from blood. All of these responses are elicited by comparable doses of endotoxin. Pretreatment of mice with poly I:poly C did not, or only marginally, increased their nonspecific resistance to infection with several bacterial pathogens, and it failed to result in the development of tolerance to endotoxin, effects known to be produced by endotoxin when given under similar conditions.

Oligonucleotides and polyribonucleotides: a review of antiviral activity

Current antiviral therapies are insufficient for treating emerging, re-emerging and established viral diseases. In an effort to find new therapeutics, oligo- and polyribonucleotides are being studied for their antiviral capabilities. Studies have shown that uniquely modified single- and double-stranded nucleic acid constructs are effective in inhibiting viral proliferation by various mechanisms. This review gives a brief history and highlights the development of oligo- and polyribonucleotides as antiviral agents primarily in the fields of interferon induction, mRNA complementation and reverse transcriptase inhibition.

Centrally administered oligodeoxynucleotides in rats: occurrence of non-specific effects

We studied the effects of various intracerebroventricularly administered oligodeoxynucleotides on body temperature, locomotor activity, food intake and water consumption in rats during a 24 h period with a radio-telemetric system. Both complete phosphorothioate oligodeoxynucleotides and end-inverted oligodeoxynucleotides dose-dependently elevated body temperature, suppressed food and fluid intake and inhibited nighttime activity. Apparently these effects do not depend on the nucleotide sequence because antisense and sense arginine vasopressin and oxytocin oligodeoxynucleotides, as well as a missense oligodeoxynucleotide produced comparable changes in the autonomous and behavioral parameters. In control experiments neither contaminants from the chemical synthesis nor endotoxins produced such effects, whereas native DNA from salmon sperm did. Fever and sickness-like behavior in response to missense phosphorothioate oligodeoxynucleotides were accompanied by elevated concentrations of circulating corticosterone and by a marked increase in interleukin 6 mRNA in brain and spleen, indicating that centrally administered oligodeoxynucleotides stimulate the production of pyrogenic inflammatory mediators in both central nervous system and peripheral tissues. Our results indicate that centrally administered oligodeoxynucleotides produce beside their intended sequence-specific effects also transient and sequence-independent effects due to their nucleic acid structure.

Effects of an interferon inducer bropirimine on bleomycin-induced lung fibrosis in hamsters

The antifibrotic effect of an interferon inducer, bropirimine (2-amino-5-bromo-6-phenyl-4(3H)-pyrimidinone, ABPP) was evaluated in bleomycin (BLM)-hamster model of lung fibrosis. ABPP is an orally active biological response modifier and has immunomodulatory, antiviral, and antineoplastic activities. The hamsters were randomized in four groups and treated with either bropirimine (100 mg/kg, intraperitoneally) suspended in carboxymethylcellulose (CMC, 10 mg/10 mg/ml) or CMC alone each day for sixteen days. After two days, the hamsters received either single bolus of BLM (7.5 U/5 ml/kg) or an equivalent volume of saline by the transoral endotracheal route. Groupings were assigned as: CMC + saline (CS), ABPP + saline (AS), CMC + BLM (CB) and ABPP + BLM (AB). Animals were sacrificed at fourteen days after intratracheal installation of either BLM or saline. Their lungs were lavaged and processed for morphometric and biochemical studies. ABPP had little effect in preventing BLM-induced weight loss and lung injury. ABPP was found to reduce the BLM-induced accumulation of collagen in the lung as measured by hydroxyproline content. The hamsters in AB group had significantly less collagen than the hamsters in CB group: 995 and 1157 micrograms hydroxyproline/lung, respectively. Administration of ABPP prevented the BLM-induced increase in the lung prolyl hydroxylase activity. The total number of monocytes and eosinophils recovered from the bronchoalveolar lavage fluid (BALF) of the AB group were significantly lower than that of the animals in CB group. However, the BALF supernatant protein content from animals in AB group (7.9 mg/lung) was significantly higher than that of CB group (4.5 mg/lung).(ABSTRACT TRUNCATED AT 250 WORDS)

The fever induced by polyriboinosinic:polyribocytidylic acid is not related to interferon synthesis in the rabbit's hypothalamus

We previously demonstrated that direct administration of interferon (IFN) or its inducer polyriboinosinic acid:polyribocytidylic acid [poly(I:C)] into the hypothalamus caused dose-dependent fever in rabbits. It was not clear whether the fever induced by intrahypothalamic injection of poly(I:C) was due to stimulation of IFN or prostaglandin E-2 synthesis in the hypothalamic tissues. Therefore, in the current experiments, we used an established model in which rabbit hypothalamic minces or brain cells were incubated in vitro with poly(I:C) to test for the ability of poly(I:C) to stimulate IFN or PGE-2 synthesis. The results showed that poly(I:C) stimulated PGE-2, but not IFN, synthesis in the hypothalamus. Thus, it appears that the fever induced by poly(I:C) is not related to IFN synthesis in the hypothalamus.

Pyrogenicity of polyadenylic.polyuridylic acid in rabbits

Polyadenylic.polyuridylic acid injected intravenously into rabbits produced a rapid-onset, monophasic fever. Pyrogenic tolerance occurred in rabbits following daily injections of polyadenylic.polyuridylic acid. However, direct injection of the agent into the preoptic anterior hypothalamic region of rabbit's brain produced a markedly different fever. After an intrahypothalamic injection of polyadenylic.polyuridylic acid, fever was delayed in onset and persisted for a longer period. At room temperature, the fever was due to both increased metabolism and cutaneous vasoconstriction. In a colder atmosphere the fever was due solely to increased metabolism, whereas in the heat the fever was due to reduction in cutaneous blood flow and respiratory evaporative heat loss. In addition, the fever induced by intravenous polyadenylic.polyuridylic acid injection was reversed by a cyclooxygenase inhibitor, but not by a protein synthesis inhibitor. Polyadenylic.polyuridylic acid was shown to stimulate PGE2 production from rabbit's hypothalamus in vitro. The results reveal that this agent is a prostaglandin-dependent pyrogen.

Conditioning the elevation of body temperature, a host defensive reflex response

We hypothesize that a number of host defense responses such as natural killer (NK) cell activity, cytotoxic lymphocyte (CTL) activity, antibody production, and elevated body temperature (TR) might be conditionable. We have designated such specifically learned response to be a defensive reflex response. Here we describe a simple single trial association paradigm for conditioning the TR response in BALB/c mice. Animals are conditioned on day 0 by exposing them to the odor of camphor for 1 hr, followed by injection of the pyrogen poly I:C 20 microgram ip. Control groups are injected with either poly I:C or saline and not exposed to the camphor odor. Reexposure of all groups to the conditioned stimulus (CS) on day 2 or 3 cause elevation of body temperature in the conditioned group mice but not in the nonconditioned or saline control groups. Since we have conditioned the natural killer cell response with the same paradigm, these results suggest that multiple defensive responses might be conditionable simultaneously and they might have important survival value for the species.

Polyinosinic-polycytidylic acid, an interferon inducer, ameliorates bleomycin-induced lung fibrosis in mice

The inhibitory effect of polyinosinic-polycytidylic acid (Poly IC), an inducer of interferons, on bleomycin-induced lung collagen accumulation was investigated in mice. Poly IC (10 mg/kg, intraperitoneally) or saline was given for 2 days and immediately prior to intratracheal instillation of bleomycin (0.125 units/mouse) or an equivalent volume of saline and thereafter daily for 13 days. Lung hydroxyproline levels in saline-saline (control), Poly IC-saline (Poly IC), bleomycin-saline and bleomycin-Poly IC groups averaged 279, 287, 459, and 358 micrograms/lung, respectively. The bleomycin + Poly IC mice had significantly less lung hydroxyproline than bleomycin mice, but significantly more hydroxyproline than control or Poly IC mice. Similarly, bleomycin + Poly IC mice had significantly less protein in bronchoalveolar lavage fluid (BALF) supernatant than bleomycin mice, but significantly more protein than control or Poly IC mice. Total cell counts for cells recovered from BALF showed significant increases of 174 and 167% in bleomycin and bleomycin + Poly IC as compared to controls, while the Poly IC group showed a significant decrease of 47% which was primarily due to a decrease in alveolar macrophages. The bleomycin group had significantly more neutrophils, monocytes, macrophages, and lymphocytes than control mice, while bleomycin + Poly IC mice lacked the significant increase in lymphocytes. Bleomycin + Poly IC mice had significantly more monocytes than the bleomycin group. All bleomycin-treated mice had lung lesions, but no lesions were observed in control or Poly IC mice. Bleomycin + Poly IC mice had significantly more (58%) lesions than bleomycin. In contrast, the volume of interstitial lesion in bleomycin + Poly IC mice showed significantly less extracellular fibers (decreased by 62%) and no difference in fibroblasts as compared to bleomycin mice. Fibrotic lesions in bleomycin mice were multifocal and varied from large areas of organized connective tissue to thickened septa lined by cuboidal epithelial cells. Interstitial lesions in bleomycin + Poly IC had a significantly greater volume of mononuclear phagocytes and lymphocytes, but less organized connective tissue than the bleomycin group. Poly IC treatment ameliorated bleomycin-induced lung collagen accumulation.

Febrile effects of polyriboinosinic acid: polyribocytidylic acid and interferon: relationship to somatostatin in rat hypothalamus

The changes in thermoregulatory effectors produced by an injection of polyriboinosinic acid: polyribocytidylic acid (Poly I:C) or interferon were assessed and compared in control rats, in rats with hypothalamic somatostatin (SS) receptor blockade and in rats with hypothalamic SS depletion. Intrahypothalamic (i.h., 0.05-0.50 microgram) or intraperitoneal (i.p., 100-600 micrograms) administration of Poly I:C caused a dose-related rise in colon temperature in control rats at all ambient temperatures (Ta) studied. A Poly I:C-induced fever was produced by increased metabolism at a Ta of 8 degrees C, whereas at 30 degrees C, it was caused by cutaneous vasoconstriction. At a Ta of 22 degrees C, the fever was caused by increased metabolism and cutaneous vasoconstriction. On the other hand, i.h. administration of SS-14 antagonist (0.1-0.5 ng) caused a dose-related fall in colon temperature at Ta of 8 degrees C or 22 degrees C. At a Ta of 8 degrees C, the hypothermia was caused by decreased metabolism, whereas at 22 degrees C, it was caused by decreased metabolism and cutaneous vasodilation. At a Ta of 30 degrees C, the thermoregulatory effectors were not affected by SS-14 antagonist treatment. Furthermore, the fever induced by Poly I:C or interferon was significantly reduced by pretreatment of rats with an i.p. dose of cysteamine (30 mg. kg-1) or an i.h. dose of SS-14 antagonist (0.1 ng). The results indicate that a somatostatinergic pathway in rat hypothalamus may mediate the fever induced by interferon or its inducer Poly I:C.

Depletion of hypothalamic norepinephrine reduces the fever induced by polyriboinosinic acid: polyribocytidylic acid (Poly I:Poly C) in rats

Administration of either Poly I:Poly C (0.05-0.50 micrograms) or norepinephrine (2-8 micrograms) into the anterior hypothalamic area produced a dose-related fever in rats. The fever induced by Poly I:Poly C was attenuated after selective depletion of norepinephrine in the hypothalamus. However, selective depletion of hypothalamic norepinephrine did not affect the fever induced by intrahypothalamic norepinephrine. The data indicate that Poly I:Poly C may act to induce fever through the endogenous release of norepinephrine from the rat's hypothalamus.

The pyrogenic actions of the interferon-inducer, polyinosinic:polycytidylic acid are antagonised by ketoprofen

The effect of various doses of polyinosinic:polycytidilic acid (Poly I:C) in the range (0.25-250 micrograms/kg) administered i.v. on the body temperature of rabbits was investigated. The effect of ketoprofen on the febrile responses was also studied. The threshold dose of Poly I:C administered which produced a fever was between 0.25 and 0.5 micrograms/kg and a double-sigmoidal dose-response relationship was observed. A sigmoidal relationship was obtained with lower doses from 0.25 micrograms/kg to an apparent maximum with 2.5 micrograms/kg and another with higher doses from 5 micrograms/kg to another apparent maximum with 250 micrograms/kg. Ketoprofen (3 mg/kg) given s.c. 15 min prior to Poly I:C inhibited the production of fever. Ketoprofen administered after the onset of fever resulted in an immediate deffervescence. These results suggest that febrile responses to Poly I:C involve prostaglandin biosynthesis.

Fever in various rheumatic diseases

In many rheumatic diseases fever may occur. This review presents data about the frequency of fever in rheumatoid arthritis, juvenile rheumatoid arthritis, systemic lupus erythematosus, crystal induced arthritis, various vasculitides and sarcoidosis. The mechanism by which body temperature rises in these situations is discussed.

Effect of interferon and double-stranded RNA on B-cell function in mouse islets of Langerhans

The direct effects of alpha- and beta-interferons on isolated mouse pancreatic islets were investigated in vitro and found to be similar. After 7 h incubation with interferon concentrations above 350 units/ml, glucose-stimulated (pro)insulin biosynthesis was significantly inhibited, with only a slight inhibition of total protein biosynthesis. Inhibition could be abolished in the additional presence of an anti-interferon antibody. Interferon did not affect insulin release, total insulin content, or glucose oxidation of the islets. The stimulation of (pro)insulin biosynthesis by adenosine, D-glyceraldehyde, mannose, N-acetylglucosamine and leucine was also inhibited by interferon, with no effect on insulin release. At concentrations of dsRNA (double-stranded RNA) said to induce interferon (1-100 micrograms/ml), glucose-stimulated (pro)insulin biosynthesis was inhibited without significantly affecting insulin release. The dsRNA may itself inhibit stimulated (pro)insulin biosynthesis or may function indirectly by the induction of interferon.

Poly(A):poly(U); poly(O8A):poly(U); poly(A):poly(MeNH5U) and poly(O8A):poly(MeNH5U) versus Bida Semliki forest virus in chick embryos

Poly(A):poly(U) (polyadenylic acid:polyuridylic acid hybrid); poly(O8A):poly(U) (poly-8-oxy-adenylic acid:polyuridylic acid hybrid); poly(A):poly(MeNH5U) (polyadenylic acid-5-methylamino uridylic acid hybrid) and poly(O8A):poly(MeNH5U) (poly-8-oxyadenylic acid:poly-5-methylamino uridylic acid hybrid) were studied in chick embryos to compare the protection offered against Semliki forest virus (the Nigerian strain) AN 49809. The modified polymers showed a higher activity index but were more toxic than the unmodified analogue.

Molecular basis of fever in humans

This review presents several areas of research on the pathogenesis of fever in humans and updates new information concerning the role of fever in host defense mechanisms. Fever is mediated by a polypeptide of phagocytic cell origin called leukocytic pyrogen. Several agents and disease processes are associated with the synthesis and release of leukocytic pyrogen. Although the original studies on leukocytic pyrogen suggested that the neutrophil was the primary source, recent experiments indicate the mononuclear phagocyte to be the major producer of leukocytic pyrogen. The mechanism by which human monocytes are stimulated to produce leukocytic pyrogen is discussed, including the effects of corticosteroids, estrogens and antipyretics on the synthesis of leukocytic pyrogen in vitro. The ability of leukocytic pyrogen to alter the hypothalamic thermoregulatory center by increasing arachidonic acid metabolite levels is the most likely mechanism by which leukocytic pyrogen initiates fever. Antipyretics prevent the synthesis of certain cyclooxygenase metabolites, which accounts for their ability to reduce fever. Studies on the chemical and physical properties of human leukocytic pyrogen are reviewed and form the basis for current experiments on the similarities between leukocytic pyrogen and lymphocyte activating factor. These studies suggest that leukocytic pyrogen, in addition to producing fever, also stimulates non-hypothalamic cells involved in aspects of the acute-phase response. In this regard, leukocytic pyrogen may be an important mechanism for host defenses. Hyperthermia may also be beneficial to the host but is distinct from fever; the role of leukocytic pyrogen as well as hyperthermia as a defense mechanism is discussed.

Hypoglycemia in mice injected with interferon inducers is not mediated by interferon

Injection of mice with several viral and nonviral inducers of interferon resulted in a marked hypoglycemia. Interferon is not responsible for this effect since inoculation of a potent antiserum to interferon (which neutralized the endogenous interferon) did not prevent hypoglycemia and administration of potent interferon preparations did not lower blood sugar. Hypoglycemia induced by Newcastle disease virus and polyriboinosinic-polyribocytidylic acid was further exacerbated by injection of insulin.

Changes in body temperature after administration of antipyretics, LSD, delta 9-THC, CNS depressants and stimulants, hormones, inorganic ions, gases, 2,4-DNP and miscellaneous agents

This survey concludes a series of complications of data from the literature, primarily published since 1965, on thermoregulatory effects of antipyretics in afebrile as well as in febrile subjects, LSD and other hallucinogens, cannabinoids, general CNS depressants, CNS stimulants including xanthines, hormones, inorganic ions, gases and fumes, 2,4-dinitrophenol and miscellaneous agents including capsaicin, cardiac glycosides, chemotherapeutic agents, cinchona alkaloids, cyclic nucleotides, cycloheximide, 2-deoxy-D-glucose, dimethylsulfoxide, insecticides, local anesthetics, poly I:poly C, spermidine and spermine, sugars, toxins and transport inhibitors. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary agents.

Studies on adjuvants for human prophylactics. I. Comparison of efficiencies of different adjuvants at various stages of immunization with tetanus and diphtheria toxoids

Kinetic studies on the adjuvanticities of several substances with different modes of action were performed in guinea pigs by using tetanus and diphtheria toxoids as the antigens. When injected subcutaneously into animals, aluminium, endotoxin, pertussis vaccine and water in oil in water (w/o/w) showed very similar adjuvanticities to tetanus toxoid at the beginning stage of immunization, but the activities except that of aluminium became less significant at later stages after the primary stimulus when antitoxin was produced abundantly. Poly L-lysine and to a less extent poly A:U showed potent adjuvanticities next to that of aluminium throughout the whole immunization period. Combination of poly L-lysine with 0.03 mg aluminium showed a similar adjuvanticity to that of 0.9 mg of aluminium alone. In contrast to rather low adjuvanticities to tetanus toxoid, more distinct adjuvanticities were observed to diphtheria toxoid throughout the whole period of immunization with various substances such as aluminium, poly A:U, w/o/w and poly L-lysine but not with endotoxin.

Systemic metabolic alterations associated with repeated injections of a modified polyriboinosinic-polyribocytidylic acid complex

Polyriboinosinic acid-polyribocytidylic acid complexed with poly-1-lysine and injected intramuscularly into rats (0.3 or 3.0 mg/kg) produced fever, altered leukocyte count, slightly depressed plasma zinc, increased amino acid uptake into liver, and increased plasma acute-phase globulins two- to threefold. It is suggested that these systemic metabolic alterations are indicative of a mild inflammatory response to this drug. The metabolic alterations may have to be taken into consideration when polyriboinosinic acid-polyribocytidylic acid complexed with poly-1-lysine is used in therapy.

Inhibited hormonal induction of hepatic phosphoenolpyruvate carboxykinase in poly I: treated mice, an endotoxin-like glucocorticoid antagonism

Corticosteroid induction of mouse hepatic phosphoenolpyruvate carboxykinase was inhibited by prior injection of poly I:C. Mice challenged with a lethal dose of endotoxin 4 h after administration of poly I: C could not be protected by a concurrent injection of hydrocortisone.

The influence of hyperthermia and poly I:C on Semliki Forest virus infection in mice

In mice infected intraperitoneally with 10(3) intracerebral suckling mice LD50 of Semliki Forest virus an additive reduction in mortality was found when the protective effect of hyperthermia and synthetic polyriboinosinic and polycytidylic aicds (Poly I:C) was combined. The effects of the two treatments seem to be independent of each other as Poly I:C was found to have no influence on the body temperature of mice, nor did hyperthermia increase the amount of interferon induced by Poly I:C.

Viral infection and host defense

Double-stranded RNA, made as an intermediary substance in the replication of most, if not all, viruses, may play a much more important role in the pathogenesis and the recovery from virus infections than has hitherto been suspected. Apparently, dsRNA is used by both the challenge virus and the host cell in an attempt to gain "molecular control." Double-stranded RNA exerts a set of effects, which may be well balanced, not only at the level of the individual cell but also at the complex assemblage of these cells termed the organism (Fig. 1). In the cell, interferon synthesis is triggered, although interferon mRNA translation may not occur if dsRNA shuts off protein synthesis too quickly. In the whole organism, the disease severity will depend on how certain toxic reactions evoked by infection (such as cell necrosis and fever) are counterbalanced by an increase in the host defense mechanisms (for example, immune responsiveness and interferon production). Many aspects of the response, relating to either progress of, or recovery from, the disease, can be explained on the basis of a dsRNA. In addition to drawing attention to the biodynamic role of dsRNA, our hypothesis suggests specific experimental vectors designed to enhance our information on the molecular basis of the morbid process which occurs with viral infection. Finally, we suggest that, although the dsRNA molecule may be viewed as a rather simple unit structure, the opportunity for further diversity in the biological activity of a given dsRNA molecule always exists. Namely, each deviation from a perfectly double-helical arrangement introduces the possibility for emphasizing one biological reactivity at the expense of another. This latter structure-activity property may partially account for the extreme apparent diversity, commonly encountered, in the presentations of virologic illness. Appendix note added in proof. Subsequent to submission of this text, we have found that the potent mitogen effect of dsRNA for lymphocytes (murine and human) is also exquisitively sensitive to the fidelity in base pairing of the input polymer pair (59). For example, infrequent "loops" (one nucleotide per 20 base pairs) in an otherwise perfectly helical rI(n) (.) rC(n) molecule [for example, rI(n) (.) r(C(19,)U)(n)] strongly changes its mitogenic properties. This observation, which supports our thesis that a "fine structure" term can be developed for other reactions triggered by dsRNA's in biological systems, emphasizes that diverse biological effects may be encountered with an ostensibly uniform family of dsRNA's.

Specific murine B-cell activation by synthetic single-and double-stranded polynucleotides

The synthetic single- and double-stranded polynucleotides, poly I, poly C, and poly I.C, were shown to induce thymidine incorporation in six inbred strains of murine spleen cells. This stimulation was shown to be secondary to B-cell activation and not due to contamination of the polynucleotides with bacterial lipopolysaccharide (LPS). The ability of poly I.C to act as a B-cell mitogen, in addition to its behavior as a thymic-independent antigen, suggested that these two phenomena may be related. The similarity of the molecular structure of poly I.C to LPS, a material which also acts as a thymic-independent antigen and a B-cell mitogen, supports the hypothesis that the polyvalent nature of these materials accounts for their functional interaction with murine B cells.

Interferon production linked to toxicity of polyriboinosinic acid-polyribocytidylic acid

Different procedures have been used in attempts to increase the production of interferon by polyriboinosinic acid-polyribocytidylic acid (poly [rI].poly [rC]) in mice: simultaneous injection of lead acetate, cycloheximide, or actinomycin D and prior injection of Freund's adjuvant, chlorite-oxidized oxyamylose (COAM), endotoxin, or Brucella abortus. In the experimental conditions tested, lead acetate, cycloheximide, Freund's adjuvant, and COAM brought about a parallel increase in interferon production and toxicity (lethality) of poly (rI).poly (rC); actinomycin D, endotoxin, and B. abortus increased the lethality of poly (rI).poly (rC) without a concomitant raise of its interferon-inducing capacity. Our results indicate that no significant increase in interferon production (or antiviral activity, as far as the antiviral activity is accounted for by interferon production) without an accompanying increase in toxicity can be achieved with poly (rI).poly (rC) and that it might be impossible to increase its therapeutic ratio (ratio of maximum tolerated dose to minimum effective dose).

Mechanism of the antiviral activity resulting from sequential administration of complementary homopolyribonucleotides to cell cultures

The antiviral activity of the double-stranded complex poly(rI) . poly(rC) in cell culture was restored or even surpassed if the constituent homopolymers were administered separately. Poly(rI) primed the cells for the antiviral activity of poly(rC) and poly(rC) primed for poly(rI), but neither poly(rI) nor poly(rC) primed the cells for the antiviral activity of noncomplementary homopolynucleotides. The priming effect of poly(rI) was significantly reduced if the poly(rI)-primed cells were treated with either T(1) ribonuclease or diethylaminoethyl (DEAE)-dextran before addition of poly(rC), and the priming effect of poly(rC) was significantly reduced if the poly(rC)-primed cells were treated with either pancreatic ribonuclease or DEAE-dextran before addition of poly(rI). (3)H-labeled poly(rC) bound more rapidly to poly(rI)-treated cells than to control cells. Cell-associated poly(rC) was markedly more resistant to pancreatic ribonuclease treatment if the cells had been incubated with poly(rI) before exposure to poly(rC). Our results clearly indicate that poly(rI) and poly(rC) added successively to cell cultures do not act independently but reunite at the cellular level, most likely at the outer cell membrane.

Antiviral activity and side effects of polyriboinosinic-cytidylic acid complexes as affected by molecular size

The decrease of the molecular size of poly(I.C) to less than 10(6) decreases its ability to induce interferon, protect mice against virus, or enhance the immune response. Immune adjuvant activity appeared more sensitive to molecular weight than the other protective activities. The composition of the complex-the molecular size of the individual homopolymers when one was large and the other small-did not affect antiviral activity; the activity of a complex made from large poly(I) and small poly(C) was similar to one made from small poly(I) and large poly(C). Molecular size of the complex did not profoundly alter the side effects of poly(I.C). At 2 mg/kg, none of the complexes markedly altered phagocytic function. Only the largest complex sensitized the mouse to endotoxin. However, all of the complexes studied profoundly inhibited drug metabolism by the liver microsomal enzymes between 24 and 72 hr after their inoculation. Decreasing the molecular weight did not alter this inhibition.

Dose responsiveness and variation among inbred strains of mice in production of interferon after treatment with poly (I)-poly (C) (poly-D-lysine) complexes

Poly-d-lysine forms a stochiometric complex with poly(I) . poly(C) which has a higher T(m) (83 C in 0.15 m NaCl) than the uncomplexed double-stranded polyribo-nucleotide (63 C). The complex was superior to poly(I) . poly(C) alone as an interferon inducer in vivo. Significant serum interferon titers were attained in Swiss mice during a 24-hr period after intraperitoneal injection of 10 to 300 mug of poly(I) . poly(C) [1.0 poly-d-lysine] complex, at concentrations of 100 to 1,000 mug/ml. The serum interferon responses (average and maximum titers) of a series of inbred strains of mice to a single intraperitoneal injection of 100 mug of complex decreased in the order: Swiss > DBA/2 > C3H > BALB/c > CF-1 > AKR, C57Bl/6, NZB > SJL > NZW and varied by a factor of approximately 100 from the most to the least responsive.