REDUCED VIRUS INFECTIVITY IN NICOTIANA-TABACUM SECRETING A TMV-SPECIFIC FULL-SIZE ANTIBODY

We developed a new concept of controlling plant virus infection based on the expression and secretion of full-size antibodies in plants. The neotope-specific anti-Tobacco Mosaic Virus (anti-TMV) antibody mAb24 has a high affinity towards epitopes present only on the surface of in tact tobacco mosaic virions. The infectivity of the virus is inhibited almost completely if TMV is adsorbed in vitro at ratios as low as 300 antibody molecules per virion prior to inoculation. Cloned full-size cDNAs of mAb24 heavy and light chains were integrated into the plant e xpression vector pSS in tandem array and used for transformation of Ni cotiana tabacum. The resulting transgenic tobacco plants expressed hea vy- and light-chains of mAb24 which were assembled into functional ant ibodies and exported to the intercellular space. TMV specificity and a ffinity of the plant-produced antibody (mAb24-P) was not altered when compared to the original murine mAb24. F-1 progenies segregated 3:1 wi th respect to antibody secretion and showed up to two-fold higher expr ession levels compared to the F-0 plants. Upon infection with TMV F-1 plants producing mAb24-P showed a reduction of necrotic lesion numbers which is correlated with the amount of antibody produced in transgeni c plants.