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A comlex of polyriboinosinic-polyribocytidylic acid (poly I-poly C) with poly-L-lysine and carboxymethylcellulose has been prepared. This complex is five to 10 times as resistant to hydrolysis by primate serum as the parent poly I-poly C. It has a thermal denaturation temperature about 40 C higher than that of poly I-poly C. The complex induces significant levels of serum interferon in monkeys and chimpanzees under conditions in which poly I-poly C itself induces no interferon.

Polyriboinosinic-polyribocytidylic acid (poly I - poly C), an interferon inducer, was administered in multiple doses of 0.3-75 mg/m2 to 26 patients with a variety of solid tumors, 9 with acute leukemia, and 2 with chronic myelogenous leukemia in blast crisis. Forty-four separate drug trials were comprised of various schedules and routes of administration. Toxic reactions included fever (in 66% of the trials), transient elevation of serum glutamic-oxaloacetic transaminase and serum glutamic-pyruvic transaminase (25%), minimal laboratory evidence of coagulation abnormalities (59%), and hypersensitivity (5%). These toxic manifestations did not relate to dose level or magnitude of interferon induction. Poly I - poly C administered iv induced low serum concentrations of interferon in 24/38 trials (63%), but the correlation between drug dose and peak interferon titer was not linear. Poly I - poly C administered iv or im was not effective as an inducer of interferon in the cerebrospinal fluid. Similarly, poly I - poly C administered im or by inhalation did not produce detectable serum levels of interferon. No patients experienced an objective tumor response to the administration of poly I - poly C, and most (76%) had progression of their disease while receiving the drug.

The mechanism for the replication of animal RNA viruses has been the subject of intense investigation. With few exceptions (Gomatos and Tamm, 1963; Sonnabend et al., 1964), however, these studies have been on picornaviruses, specifically poliovirus (Baltimore, Becker, and Darnell, 1964) or members of the encephalomyo-(arditis group (Montagnier and Saunders, 1963). This report will present studies on the replication pattern of Semliki Forest virus, a group A arbovirus. Semliki Forest virus has some properties advantageous to the study of animal virus replication, including a particle-to-infectious-virus ratio close to 1 (Cheng, 1961), wide host range, rapid growth to high titers in tissue culture, and little or no pathogenicity for man (Andrews, 1964). In this paper the forms of viral RNA produced in the cytoplasm of infected chick embryo fibroblasts are considered. Materials and Methods.-Virus: The Kumba strain of Semliki Forest virus (SFV) employed in these studies was originally obtained from Dr. Alick Isaccs, Mill Hill, London. Pools of virus were prepared by infection of actinomycin D (ACM)-treated (0.5 ,g/ml) chick embryo fibroblasts with low multiplicities of virus. Virus was grown in Eagle's medium, harvested after 14 hr by the methods of Taylor (1965), and assayed by a plaque titration method (Friedman, 1964). Radioactive virus was grown in chick cells treated with ACM (0.5 ,gg/ml) in the presence of H3uridine and H3-adenosine. Fluids were harvested after 18 hr and virus was purified by the method of Cheng (1961) with the addition of a final dialysis to remove small tritiated products. The specific activity of the final preparation was usually about 1 cpm/2000 infectious units. The RNA extracted from this virus preparation by the method of Cheng (1958) had a sedimentation value of 42S and was ribonuclease-sensitive. Sedimentation velocities of the tritiated virus performed on sucrose gradients indicated a peak of radioactivity at about 350S which corresponded to the peak of virus infectivity (cf. Cheng, 1961). Radioactivity and infectivity were also present in the pellet, possibly due to viral aggregation. Cells: One-day-old primary chick embryo monolayers (CE) were prepared in 100-mm plastic Petri plates by previously described methods (Taylor, 1965); these cells were employed in all studies. When confluent, these monolayers contained about 2.5 X 107 cells/plate. Pulse-labeling and viral RNA extraction: Pulse-labeling was carried out by adding to the cell cultures 1 ml of tissue culture fluid containing the isotope. After an appropriate pulse period, the monolayers were washed five times with cold phosphate buffered (0.01 M, pH = 7.2) 0.85% saline and once with potassium phosphate buffer (0.1 M, pH = 7.1). Cells were removed from plastic Petri dishes with a rubber stopper and suspended in 1 ml of potassium phosphate buffer. The cells were disrupted with a Dounce homogenizer, and the homogenate was centrifuged at 600 g for 10 min. The remaining cytoplasmic fraction was extracted with 5% sodium dodecyl

The synthetic double-stranded RNA, polyinosinic-cytidylic acid, inhibits the growth of some tumors in mice. Two days after implantation of a reticulum cell sarcoma, a lymphatic lymphoma, a fibrosarcoma, two leukemias, and a human adenovirus 12-induced tumor, treatment of groups of mice resulted in decreased growth rates of the tumors and increased survival times of the animals. In the two tumors tested (the reticulum cell sarcoma and the adenovirus 12-induced tumor) initiation of treatment after the tumor was grown to moderate size caused a regression of the tumor. In the case of the reticulum cell sarcoma, the tumor had not reappeared in some of the animals two months after cessation of treatment.

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Polyriboinosinic-polyribocytidylic acid [poly(IC ⅐ LC)] was evaluated for its prophylactic and therapeutic efficacies against respiratory influenza A virus infection in mice. Two doses of poly(IC ⅐ LC) (1 mg/kg of body weight per dose) administered intranasally within 12 days prior to infection with 10 50% lethal doses of mouse-adapted influenza A/PR/8 virus fully protected the mice against the infection. Determination of virus titers by hemagglutination and plaque assays showed more than a 2-log 10 decrease in virus titers in lung homogenates of pretreated mice compared with those in the lungs of the nonpretreated group. Treatment of infected mice with poly(IC ⅐ LC) resulted in a modest (40%) survival rate. These results suggest that poly(IC ⅐ LC) provides a highly effective prophylaxis against respiratory influenza A virus infection in mice.

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