Present trends and the future in rabies research

Until very recently, rabies research had made few notable advances since the time of Pasteur, but during the past few years the use of modern virological techniques has led to rapid progress in research on the rabies virus. This article summarizes the present state of knowledge of pathogenesis, immunology, cultivation in tissue culture, cell-virus relationships, and physicochemical properties of the virus.It is now possible, and opportune, to undertake the study of basic problems in the biology of rabies, which include the need for an improved method of post-exposure protection. Information gained from work on these problems should lead to important insights into other current problems of infectious processes such as "slow-virus" infections. The most promising directions of future research in rabies are enumerated and suggestions are made on the experimental techniques that might be used for such studies.

Effect of polyions on the infectivity of rabies virus in tissue culture: construction of a single-cycle growth curve

The infectivity of fixed rabies virus in a number of cell lines has been shown to be markedly enhanced by the addition of protamine or diethylaminoethyl dextran to the virus inoculum. The polycations appear to exert their influence at a very early stage (adsorption or penetration or both) of virus-cell interaction. Immune globulin blocked infection completely when added up to 5 min after exposure and almost completely when added 5 to 15 min after infection. Antibody had no effect on adsorption and penetration when added to the inoculum 30 min or more after cells were exposed to the virus. Irradiation of BHK/21 cell monolayers with ultraviolet light increased their sensitivity to rabies virus. The events occurring after synchronous infection of cells in both irradiated and nonirradiated cell monolayers were followed by means of fluorescent-antibody staining and by intracerebral titration in mice. Virus-specific fluorescent antigen first appeared between 8 and 9 hr after infection, and in irradiated cultures there was a further lag period of 3 hr before infectious virus was produced intracellularly. Virus was first detected in the medium 12 to 15 hr after infection, and maximal yield of infectious virus was observed 48 hr after exposure. In nonirradiated cultures, formation of infectious virus was delayed, and the final yield of virus was also reduced.

Rabies neutralizing antibody response to different schedules of serum and vaccine inoculations in non-exposed persons. 4

Early and persistent antibody is needed for maximum protection to be afforded to persons severely exposed to rabies. With vaccine alone, detectable antibody production takes 7-10 days, and the passive antibody introduced with antirabies serum or gamma-globulin is commonly used to fill this gap. However, administration of antirabies serum or gamma-globulin with vaccine interferes with the antigenic action of the vaccine.The studies reported in this paper provide further evidence that the interfering effect of serum can be overcome by giving booster doses of vaccine, as recommended by the WHO Expert Committee on Rabies, 10 and 20 days after the end of the usual 12- to 14-dose series of vaccine inoculations. While the results do not clearly indicate whether a single booster dose might be sufficient, the authors consider the second booster useful to ensure both degree and length of antibody duration.

Comparative studies of atherosclerosis in swine

A survey of spontaneously occurring fatty streaks and fibrous plaques, considered as atherosclerosis, in 1637 swine in different European countries and the USA, using a standardized procedure, was undertaken to determine whether significant differences exist in the occurrence and extent of the disease in various groups of animals. At the same time a preliminary study on the possible relation of any differences observed in atherosclerosis to certain environmental and constitutional factors was carried out with the ultimate goal of contributing to the understanding of analogous problems in man.STATISTICALLY SIGNIFICANT INCREASES OF FATTY STREAKS AND FIBROUS PLAQUES WERE NOTED IN RELATION TO: (a) increasing age, starting at 6 to 7 months, the earliest age period studied; (b) geographical locality; and (c) considerable as compared with moderate or slight physical activity at 1 year of age. Although not statistically significant, there was also a suggestive trend towards more atherosclerosis in pigs consuming soft water as compared with those consuming hard water.While these correlations may represent contributory factors to the increases of the changes noted in the abdominal aortas, it is not possible to pinpoint the importance of individual components because of the limited data and the large number of variables involved in this preliminary study. Studies in swine and other animals are being encouraged in which all variables but one are being kept constant to determine their possible role in the development of atherosclerotic lesions.

An intracerebral assay procedure in mice for chemical inactivation of rabies virus

An intracerebral assay technique in mice is described for testing chemical disinfectants acting on the rabies virus. The assay determines whether more than 99% of 10 000 mouse intracerebral LD(50) of virus are inactivated within 1-2(1/2) minutes. By this test, several substances usually available for the treatment of animal bite wounds were found to be effective. They are: 1%-20% soap solutions; 43%-70% alcohol; 1:1000 (0.1%) or lower dilutions of two quaternary ammonium compounds, benzalkonium chloride and cetrimonium bromide; 1:10 000 or lower dilutions of iodine; acetone; and ether.Several other substances tested for possible use in environmental disinfection were also found to be virucidal. They were: 3% caustic soda and commercial preparations of organic phenols, iodine, and a mixture of trisodium phosphate and sodium hypochlorite. No virucidal effect was exerted by a 2% aqueous solution of mercurochrome, a 1:1000 aqueous solution of thiomersal, or 3% formalin (1% formaldehyde).A number of substances that inactivate rabies virus have thus become available for local treatment of bite wounds and for environmental disinfection. The assay procedure described may be useful in testing other disinfectants and chemical substances.