The present invention provides compositions and methods for delivering a nucleotide sequence to a cell using an alphavirus vector that is complexed with an enhancing antibody that specifically binds to the alphavirus vector. Venezuelan Equine Encephalitis vectors are preferred. The cell may be a cell in vitro or in vivo. Alternatively, the cell may be removed from a subject, administered the alphavirus vector ex vivo and then administered to a subject. Antigen-presenting cells are preferred, with dendritic cells being more preferred. Also provided are methods of producing an immune response in a subject, e.g., for producing an immune response against an antigen associated with a pathogen or for immunotherapy of cancer of tumors.