Use of virus vectors for the expression in plants of active full-length and single chain anti-coronavirus antibodies.

To extend the potential of antibodies and their derivatives to provide passive protection against enteric infections when supplied orally in crude plant extracts, we have expressed both a small immune protein (SIP) and a full-length antibody in plants using two different plant virus vectors based on potato virus X (PVX) and cowpea mosaic virus (CPMV). The alphaSIP molecule consisted of a single chain antibody (scFv) specific for the porcine coronavirus, transmissible gastroenteritis virus (TGEV) linked to the alpha-CH3 domain from human IgA. To express the full-length IgA, the individual light and heavy chains from the TGEV-specific mAb 6A.C3 were inserted into separate PVX constructs and plants were co-infected with both constructs. Western blot analysis revealed the efficient expression of both the SIP and IgA molecules. Analysis of crude plant extracts revealed that both the plant-expressed alphaSIP and IgA molecules could bind to and neutralize TGEV in tissue culture, indicating that active molecules were produced. Oral administration of crude extracts from antibody-expressing plant tissue to 2-day-old piglets showed that both the alphaSIP and full-length IgA molecules can provide in vivo protection against TGEV.