STUDIES IN RODENT POLIOMYELITIS : V. INTERFERENCE BETWEEN MURINE AND MONKEY POLIOMYELITIS VIRUS

INTERFERENCE BETWEEN THE INFLUENZA VIRUSES : I. THE EFFECT OF ACTIVE VIRUS UPON THE MULTIPLICATION OF INFLUENZA VIRUSES IN THE CHICK EMBRYO

Reciprocal interference between influenza A, influenza B, and swine influenza viruses has been demonstrated in the chick embryo. Certain temporal and quantitative factors which influence the production of interference in this host-virus system have been studied. The implications of these observations in relation to the mechanism by which interference is produced are discussed.

INTERFERENCE BETWEEN THE INFLUENZA VIRUSES : II. THE EFFECT OF VIRUS RENDERED NON-INFECTIVE BY ULTRAVIOLET RADIATION UPON THE MULTIPLICATION OF INFLUENZA VIRUSES IN THE CHICK EMBRYO

Influenza A or influenza B virus rendered non-infective by ultraviolet radiation was found to be capable of producing interference with the multiplication of active influenza viruses in the chick embryo. Certain temporal and quantitative relationships affecting the interference phenomenon with this host-virus system were studied. An hypothesis of the mechanism of interference between the influenza viruses is proposed and discussed.

THE PROTECTIVE ACTION OF TRYPAN RED AGAINST INFECTION BY A NEUROTROPIC VIRUS

Trypan red, when injected intraperitoneally into mice, has been found greatly to lower the incidence of the infection of mice inoculated intraperitoneally with the neurotropic MM virus. The protective action of the dye is overcome if the virus is inoculated in too high concentration. The lowered incidence of infection was observed in mice inoculated with virus for as long as 29 days after the last dye injection. Of a number of dyes tested, trypan red, brilliant vital red, and Congo red were found effective. In cotton rats inoculated intraperitoneally with MM virus, trypan red was likewise found to lower the incidence of infection. With monkeys and a typical poliomyelitis virus no protection was observed against the virus inoculated intraperitoneally. The latter experiment is considered to have been inadequate for a critical test of the effect of trypan red on poliomyelitis infection. When either the MM virus or Lansing virus were inoculated intracerebrally into mice, the effect of the dye on incidence of infection was small. In the case of the Lansing virus the difference was statistically significant, however. The possible relation of alteration in the permeability of the barrier between the blood and the central nervous system as a cause of the effect of trypan red is discussed.

Studies on resistance to bacterial infections in animals infected with Rickettsiae

Data are presented, demonstrating that infection with Rickettsia typhi brings about a reduction of the death rates and a prolongation of the time of survival in animals subsequently challenged with Pasteurella pestis or Pasteurella tularensis. This interference with bacterial infection by previous rickettsial infection does not appear immediately after injection of the rickettsiae; it begins to appear around 16 hours after this injection and becomes more marked during the first 96 hours; later it decreases. The phenomenon is essentially a local tissue reaction with weaker systemic effects. The phenomenon of interference can be overcome by challenge with too large a number or too virulent a strain of bacteria. A strain of P. pestis subjected to 10 passages through mice infected with Rickettsia typhi failed to develop resistance to the interfering activity of the latter microbial species. This does not rule out, but might be evidence against, an assumption that the interfering action is due to antibiotic effects from the rickettsiae.

Distemperoid Virus Interference in Canine Distemper

A distemper virus modified by ferret passage so as to become a harmless vaccine for foxes and dogs exhibits the interference or cell-blockade phenomenon with respect to a virulent distemper infection in foxes. Ten control foxes receiving virulent distemper virus died, while 30 foxes receiving distemperoid virus in addition lived.

INTERFERENCE BETWEEN VIRUSES IN TISSUE CULTURE

The influence of one virus on the growth of another in tissue culture was investigated. The 17DD High strain of yellow fever virus was found capable of completely suppressing the growth of both the Asibi strain of the same virus and of the heterologous West Nile virus, even when these were added to the cultures in large amounts. The 17DD High strain of yellow fever virus and the West Nile virus produced either partial or complete suppression of growth of the Venezuelan equine encephalomyelitis virus, depending upon the quantity of the latter inoculated into the cultures. Owing to lack of methods for the detection of interference except in a single direction, reciprocal interference with these viruses could not be investigated. The 17DD High strain of yellow fever virus and the West Nile virus were able to suppress completely, or almost completely, the growth of influenza A virus added to the infected cultures in maximal amounts. Interference in the reverse direction, even with the use of small amounts of the neurotropic viruses, was not demonstrable. Cultures infected with the 17DD High strain of yellow fever virus were examined for the presence of neutralizing antibodies and non-specific antiviral substances; neither was found present.