Lawrence Kilham

A latent virus of rats isolated in tissue culture

Abstract Several strains of a new virus (RV) have been isolated from rat tumors under conditions which suggest that it may be a latent agent in these animals. The virus is characterized by its ability to multiply and to cause a marked cytopathogenic effect (CPE) in rat embryo cells in tissue culture. The virus is associated with a hemagglutinin for guinea pig red cells, and circulating antibodies against these strains have been found in a number of laboratory and wild rats, suggesting that it is widely disseminated. Viral antibodies were detected in a germ-free rat, suggesting that the agent may be vertically transmitted. The virus resembles SE polyoma virus in a number of respects, including heat stability, resistance to ether, agglutination of red cells without spontaneous elution and the destruction of red cell receptors by cholera vibrio filtrates containing receptor-destroying enzyme (RDE). The virus differs from SE polyoma virus in that there is no detectable antigenic relationship and the agent does not grow in mouse embryo tissue nor does it cause tumors or other detectable pathology on inoculation into rats. However, the resemblances suggest that the two agents may represent mouse and rat variants of a similar class of virus agent.

A Pneumotropic Virus Isolated from C3H Mice Carrying the Bittner Milk Agent

Summary 1. Five isolations of a virus which causes a fatal pneumonitis of suckling mice by various routes of inoculation have been made from C3H mice known to carry the Bittner Milk Agent. 2. Older suckling mice are increasingly resistant to this virus and no apparent illness has been produced by inoculation of adult mice. 3. Specific neutralizing antisera have been produced in rabbits. 4. Due to its unique behavior and failure to show serologic or other relationships to known mouse viruses, K-virus has been regarded as an hitherto undescribed agent. 5. Long term experiments have been set up to determine, if possible, whether K-virus is identical with or related to the Bittner Milk Agent.

Rat Virus (RV) Infections in Hamsters

Summary 1) Rat virus (RV) can induce 3 different conditions in suckling hamsters according to dose of virus and age of the animal at time of inoculation. These conditions are (a) a fatal disease in sucklings 1 to 4 days of age; (b) a stunted growth in those surviving a minimal dose, and (c) a latent infection of older sucklings. 2) Spontaneous transmission of RV can take place from inoculated to uninoculated hamsters. 3) Infected sucklings have infective virus in high titer in livers, kidneys and other organs as well as in lesser amounts in blood and urine. Specimens with the highest infectivity titers have also had considerable amounts of hemagglutination activity. 4) Rat virus has been carried through 20 passages in suckling hamsters. Intracerebral, intranasal, subcutaneous and intraperitoneal routes of inoculation have all been effective in inducing acute disease.

Laboratory Transmission of Fibromas (Shope) in Cottontail Rabbits by Means of Fleas and Mosquitoes

Summary 1. Fibroma virus may be transmitted from cottontail to cottontail by means of pin pricks, fleas found on cottontails, and by the mosquito Aedes aegypti (Linnaeus). 2. Aedes aegypti transmits fibroma virus under favorable circumstances, in as high a proportion of bites at 2 weeks following initial term feeding as at 24 hours. 3. Virus carrying mosquitoes induced fibromas on the eyelid and close to the eye of one cottontail when given the opportunity to feed at will. 4. Possible mechanisms involved in mosquito transmission are discussed.

Transformation of fibroma into myxoma virus in tissue culture.

Summary 1. Eleven experiments are described in which fibroma was transformed into myxoma virus in cultures of rabbit tissues, both of testes and of kidneys. 2. The transforming agent (TAM) was myxoma virus inactivated by heating at 65–67°C. 3. Live fibroma virus and TAM were inoculated into tissue cultures simultaneously and TAM was re-added at times of fluid change. 4. A good growth of supporting cells appeared essential to successful transformations.

Naturally occurring fibromas of grey squirrels related to Shope's rabbit fibroma.

Summary Six grey squirrels collected in Maryland were found to have multiple small cutaneous nodules which histologically resembled Shopes rabbit fibroma. The squirrel fibroma was carried through 2 intracutaneous passages in grey squirrels, 4 consecutive passages in woodchucks, and from woodchucks for 2 passages in domestic rabbits. Cross-neutralization tests provided immunological evidence that the squirrel and Shope fibromas are related.

Propagation of fibroma virus in tissue cultures of cottontail testes.

Summary (1) A mammalian tumor-inducing virus, that of the Shope fibroma, has been propagated in tissue culture. (2) Two lines of fibroma virus were each carried through 14 successive passages in tissue cultures of cottontail testes. (3) One line of virus was carried up to 4 passages in similar cultures of domestic rabbit testes. (4) Growth of virus was accompanied by formation of acidophilic, intracytoplasmic inclusions and by vacuoles containing a substance with a ground glass appearance.

The fibroma-myxoma virus transformation.

Publisher Summary This chapter relates how tissue culture, by enabling one to perform the transformation of fibroma into niyxonia virus in a predictable fashion, has opened up prospects of investigating the behavior of the deoxyribonucleic acids (DNA) of the viruses involved and their relation to processes of infection in mammalian host cells. This approach to the Berry-Dedrick phenomenon is a relatively new one. It considers in the broad setting of what is known of DNA in other microbial systems in order to gain perspective before consideration of actual experiments. The chapter discusses the transformation of fibroma into myxoma virus. It has become increasingly apparent that the characteristics of poxviruses that include fibroma and myxoma are of basic importance to the studies on their viral DNA in relation to host cells. Some characteristics of these viruses have been presented. The chapter concludes with the discussion of the DNAase sensitive TAM and its biological properties.

Propagation of Mumps Virus in Suckling Mice and in Mouse Embryo Tissue Cultures

Summary 1. Mumps virus has been carried through 20 passages in mouse embryo tissue culture in the course of which it developed a progressive ability to grow in brains of suckling mice, without apparent illness of the animals. 2. Another strain of mumps, after passage in brains of suckling hamsters, also multiplied readily in the brains of suckling mice, leading to illness and, in a small proportion, to death on continued passage. 3. Practical and theoretical implications of this adaptation of mumps virus to mice have been discussed.

Territorial Behavior in Pikas

Pikas, Ochotona princeps , observed on successive week ends from September 4 to October 8, 1955 on a rock slide in the Sapphire Range in western Montana, exhibited well-marked territorial behavior. Brown, gray, and mixed color patterns induced by molting facilitated recognition of individual animals. The six pikas observed remained solitary within adjacent territories. They were often harvestng in early mornings, running to the upper or lower ends of the rock slide to cut stalks of grass or twigs from bushes. The pikas would then race back to their hay piles with the cut vegetation projecting from one side of their mouths. These mounds were really brush piles, with …