A recombinant adeno-associated virus (AAV) having an AAV capsid and packaged therein a heterologous nucleic acid which expresses two functional antibody constructs in a cell is described. Also described are antibodies comprising a heavy chain and a light chain from a heterologous antibody. In one embodiment, the antibodies are co-expressed from a vector containing: a first expression cassette which encodes at least a first open reading frame (ORF) for a first immunoglobulin under the control of regulatory control sequences which direct expression thereof; and a second expression cassette which comprises a second ORF, a linker, and a third ORF under the control of regulatory control sequences which direct expression thereof, wherein the second and third ORF for a second and third immunoglobulin construct. The vector co-expressing these two antibody constructs is in one embodiment an AAV, in which the 5′ and 3′ ITRs flank the expression cassettes and regulatory sequences.