Sublingual-swallow immunotherapy in house dust mite–related asthma has a good safety profile and improves respiratory function and bronchial hyperreactivity. Zucchini yellow mosaic virus (ZYMV) is envisaged as a promising viral vector for expressing large quantity of foreign proteins in cucurbit species.

We sought to investigate whether oral feeding of dust mite allergen expressed by ZYMV in a cucurbit species can suppress allergen-induced inflammation and IgE synthesis.

An infectious plant virus clone, p35SZYMV2-26, that contains the full-length cDNA to the genomic RNA of a Taiwan isolate of ZYMV, driven by the cauliflower mosaic virus 35S promoter, was engineered as an in vivo viral vector to express Dermatophagoides pteronyssinus group 5 allergen (Der p 5) in cucurbit species. Female BALB/c mice were intraperitoneally sensitized with Escherichia coli bacteria–expressed Der p 5 and orally treated with the virus-expressed Der p 5 (vDer p 5) extracted from the recombinant virus-infected squash plants. Der p 5–specific immunoglobulins were measured by ELISA, and bronchoalveolar lavage assays were used to measure airway inflammation.

Infectivity assays and immunoblotting revealed that large quantities of free-form vDer p 5 are produced in the recombinant virus-infected squash plants. The recombinant virus carried and expressed the Der p 5 allergen in squash plants for at least 1 year after numerous passages. In animal tests, squash extract containing vDer p 5 inhibited Der p 5–specific IgE synthesis and airway inflammation.

Our results suggest that oral feeding with allergen produced by the plant viral vector provides a novel approach for the therapy of allergic asthma.