Lactoferrin, an iron-binding protein previously shown to occur in many external secretions, is identified as one of the major proteins present in human and guinea pig neutrophilic polymorphonuclear leukocytes. The identification of this protein in leukocyte extracts was based upon a comparison of its electrophoretic, antigenic, and iron-combining properties with the corresponding properties of the same protein isolated from human and guinea pig milk. Immunochemical quantitations showed that lactoferrin occurs in human neutrophilic leukocytes at the concentration of 3 µg per 106 cells. Tissue cultures from guinea pig bone marrow and spleen actively synthesized the protein, as shown both by net production of lactoferrin and incorporation of labeled amino acids into the protein. Immunohistochemical data indicate that lactoferrin first appears in myeloid cells at the stage of the promyelocyte.

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Polyacrylic acid (PAA) and polymethacrylic acid (PMAA) were investigated for their antiviral properties in tissue culture. Compared to other related polyanions, as dextran sulfate, polystyrene sulfonate, polyvinyl sulfate, and polyphloroglucinol phosphate, PAA and PMAA were found to be significantly more antivirally active and less cytotoxic. PMAA added 24 hr prior to virus inoculation inhibited viral growth most efficiently but it was still effective when added 3 hr after infection. Neither a direct irreversible action on the virus nor inhibition of virus penetration into the cell could explain the antiviral activity of PMAA. PMAA inhibited the adsorption of the virus to the host cell and suppressed the one-cycle viral synthesis in tissue cultures inoculated with infectious RNA.

Chlorite-oxidized oxypolysaccharides are polyacetal carboxylic acids. They inhibited the cytopathic effect of vesicular stomatitis virus in mouse embryo cell cultures challenged at low input multiplicity. After intraperitoneal injection of these compounds in mice, interferon appeared in the circulation. The compounds also protected mice against lethal mengovirus infection and against the development of experimental pox lesions on the tail. Chlorite-oxidized oxyamylose was antiviral only when at least 64% of the glucopyranose units were oxidized, an observation which suggested a correlation between charge density and antiviral effect. The antiviral activity was also influenced by the molecular weight, as demonstrated by the fact that chlorite-oxidized dextrans which had a high intrinsic viscosity were more active than those with low intrinsic viscosity. ' "Bevoegdverklaard navorser" of the Belgian N.F.W.O. 2 "Aangesteld navorser" of the Belgian N.F.W.O.

A marked virus-inhibiting potency is obtained in the serum after intraperitoneal injection of polyacrylic acid (PAA) and polymethacrylic acid (PMAA) in mice. Much higher antiviral levels were reached than for other related polymers including dextran sulfate, heparin, polyvinyl sulfate, pyran copolymer, polystyrene sulfonate, and macrodex. The broad antiviral action of PAA and PMAA was attributed both to a direct interference with the virus-cell interaction and the viral ribonucleic acid metabolism and to the formation of an interferon-like factor. Both polyanions differed in interferon-inducing ability: highest serum interferon titer was obtained 18 hr after the intraperitoneal injection of PAA. The mechanism of interferon production by PAA and PMAA is discussed. As described previously for Sindbis virus and endotoxin, the animals also became hyporeactive after injection of PAA.

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