In vivo enhancement of rabies infection by diethylaminoethyl-dextran

Abstract

The increased sensitivity in tissue culture of infectious viral nucleic acids and intact viruses caused by polycations is well documented (1,2,3,4,5,6). The in vitro rabies virus infection is markedly enhanced by the addition of diethylaminoethyl-dextran (DEAE-D) and protamine sulfate (7,8). Recent studies (9) carried out about the enhancing effect of DEAE-D on tumor induction in mice, caused by the Moloney strain of murine sarcoma virus, have activated our interest in trying this polyeation also in rabies infection in mice and cattle.A standard challenge virus (CVS) has been employed by adapting it to kill mice by the intramuscular route. Four intramuscular passages gave an average titre of the brain of 104.4 LDs0/ml in three week old mice. A stock of this virus brain suspension 1 : 10 was stored at --70 ~ C for use in the experiments. The intracerebral titre in three week old mice of this CVS adapted strain was 10 s.1 LD~0/ml.Three tissue culture adapted rabies clones "Mazatan", "V319" and "ERA"were used. The Mazatan strain is of bovine and the V 319 of vampire bat (Desmodus rotundus) origin. The "ERA" clone is derived from the Et~A vaccine strain (10~ 11), plaque picked and multiplied to a high titre (10 s-5 p.f.u./ml) in the BHK-21 cell line. Both other clones have been multiplied similarly in this cell line for use in these studies and were stored also at --70 ~ C. Plaque titration and plaque reduction tests (12) were carried out by means of a slightly modified agarose-eell suspension technique (publication in preparation).

Adjuvant effects of diethylaminoethyl-dextran

“…The humoral enhancement appeared to be dose related, in that greater antibody values were elicited by the higher concentration of the polycation. These data are consistent with the findings of others that DEAE-D significantly increased neutralizing antibody production and protection in pigs immunized with inactivated foot-and-mouth disease virus vaccine (1, 15) and in cattle immu-nized with a vaccine strain of rabies (3).…”