Humoral and cellular immune responses to HIV-1 Nef in mice DNA-immunised with non-replicating or self-replicating expression vectors

Objective: HIV accessory protein Nef is expressed early in the infectious c ycle of the virus and has been shown to be an effective immunogen in humora l and cellular immune responses. We have used two different self-replicatin g pBN vectors and one non-replicating pCGal2 derived (pCG) vector expressin g HIV-1 Nef in DNA immunisation of mice in order to determine their efficie ncy in raising humoral and cellular immune responses. Design and methods: T he expression of Nef by the three plasmids was tested by transfections into COS-1 cells. Balb/c mice were immunised with the pBN-NEF and pCGE2-NEF con structs using gold particle bombardment. Immunoblotting and immunocytochemi stry were used to detect in vitro expression of Nef. Cr-51 release assay, E LISA and immunoblotting were used to detect cellular and humoral immune res ponses in immunised mice. Results: Efficient in vitro expression of Nef was detected in pBN and pCGE2-NEF transfected cells, in pBN-NEF transfected ce lls the expression lasting up to three weeks. Anti-Nef antibodies in sera o f 13 of 16 pBN-NEF immunised mice were detected within four weeks after the last immunisation, whereas only 2 of 12 pCGE2-NEF immunised mice had very weak anti-Nef antibodies. Twelve of the pBN-NEF immunised mice (75%) and 6 the pCGE2-NEF immunised mice (50%) showed Nef-specific cytotoxic T lymphocy te (CTL) responses within four weeks. Conclusions: We conclude that the thr ee eukaryotic expression vectors tested are capable of inducing a cell medi ated immune response towards HIV-1 Nef and should be considered as part of a genetic HIV vaccine. (C) 1999 Elsevier Science Ltd. All rights reserved.