Development and in vitro characterization of recombinant vaccinia viruses expressing bovine leukemia virus gp51 in combination with bovine IL4 or IL12

Type 1 and type 2 immune responses are modulated by IL12 or IL4, respective ly, at the time of lymphocyte priming. Importantly, type 1 responses have b een associated with resistance to retroviral infection in mice, humans, and ruminants. Specifically, vaccination of sheep with vaccinia virus expressi ng bovine leukemia virus (BLV) gp51 resulted in protective immunity with th e characteristics of a type I response, whereas vaccination of cattle resul ted in a non-protective type 2 response. In order to test the hypothesis th at cattle inoculated with BLV gp51 and IL12 will respond with a type 1 resp onse, a recombinant vaccinia virus expressing BLV gp51 together with bovine IL12 was developed and characterized in vitro. For induction of type 2 res ponses a recombinant vaccinia virus expressing gp5I with bovine IL4 was sim ilarly constructed and characterized. In this study recombinant cassettes w ere developed containing either the BLVenv gene alone or in combination wit h bovine IL4 or the two genes, p35 and p40, encoding bovine IL12. Correct a lignment with p7.5 or p11 vaccinia promoters and orientation was confirmed by complete sequencing. Recombinant vaccinia viruses were generated by homo logous recombination, selected based on large plaque formation due to recon stitution of the vp37 gene, and structurally confirmed by Southern blotting . Transcription of recombinant BLVenv, bovine IL4, p35 and p40 was demonstr ated by RT-PCR. Expression of BLVenv gp51 protein and bovine IL4 was shown by immunofluorescence and immunoblotting. Biologically active bovine IL4 ex pressed by vaccinia virus stimulated lymphoblast proliferation, B lymphocyt e proliferation in the presence of CD40L, and inhibited IFN gamma, secretio n from PHA activated PBMC in a dose dependent fashion. Finally, bovine IL12 expression and biological function was confirmed by dose dependent inducti on of IFN gamma secretion by PHA activated PBMC and the moderate enhancemen t of lymphoblast proliferation. In conclusion, bovine IL12 and IL4 expresse d by recombinant vaccinia virus in vitro clearly exhibited type 1-type 2 mo dulating properties. (C) 1998 Elsevier Science Ltd. All rights reserved.