Plant-produced idiotype vaccines for the treatment of non-Hodgkin's lymphoma: safety and immunogenicity in a phase I clinical study.

Plant-made vaccines have been the subject of intense interest because they can be produced economically in large scale without the use of animal-derived components. Plant-made therapeutic vaccines against challenging chronic diseases, such as cancer, have received little research attention, and no previous human clinical trials have been conducted in this vaccine category. We document the feasibility of using a plant viral expression system to produce personalized (patient-specific) recombinant idiotype vaccines against follicular B cell lymphoma and the results of administering these vaccines to lymphoma patients in a phase I safety and immunogenicity clinical trial. The system allowed rapid production and recovery of idiotypic single-chain antibodies (scFv) derived from each patient's tumor and immunization of patients with their own individual therapeutic antigen. Both low and high doses of vaccines, administered alone or co-administered with the adjuvant GM-CSF, were well tolerated with no serious adverse events. A majority (>70%) of the patients developed cellular or humoral immune responses, and 47% of the patients developed antigen-specific responses. Because 15 of 16 vaccines were glycosylated in plants, this study also shows that variation in patterns of antigen glycosylation do not impair the immunogenicity or affect the safety of the vaccines. Collectively, these findings support the conclusion that plant-produced idiotype vaccines are feasible to produce, safe to administer, and a viable option for idiotype-specific immune therapy in follicular lymphoma patients.

Malarial epitopes expressed on the surface of recombinant tobacco mosaic virus.

Using malaria as a model disease, we engineered the surface of tobacco mosaic tobamovirus (TMV) for presentation of selected epitopes to the mammalian immune system. The TMV coat protein is a well-characterized and abundant self-assembling polymer previously shown to be a highly immunogenic carrier. Selected B-cell epitopes were either inserted into the surface loop region of the TMV coat protein or fused to the C terminus using the leaky stop signal derived from the replicase protein reading frame. Tobacco plants systemically infected with each of these constructs contained high titers of genetically stable recombinant virus, enabling purification of the chimeric particles in high yield. Symptoms induced in tobacco ranged from a normal mosaic pattern similar to that induced by the parental U1 strain to a unique bright yellow mosaic. As measured by quantitative ELISA against synthetic peptide standards, wild type TMV coat protein and fusion protein synthesized by the leaky stop mechanism coassembled into virus particles at the predicted ratio of approximately 20:1. Recombinant plant viruses have the potential to meet the need for scalable and cost effective production of subunit vaccines that can be easily stored and administered.

RAmy2A; a novel alpha-amylase-encoding gene in rice.

The structure and expression of the alpha-amylase-encoding gene, RAmy2A, are described. This only representative of the Amy2 subfamily in rice differs from other cereal alpha-amylase-encoding genes in several respects. It contains the largest introns of all the cereal alpha-amylase-encoding genes examined to date. Moreover, the second of three introns in this gene contains a long inverted repeat sequence that can potentially form a large and stable stem-loop structure in the unspliced RNA transcript. Finally, RAmy2A is constitutively expressed at very low levels in germinated seeds, root, etiolated leaves, immature seeds and callus. This is in marked contrast to the Amy2 genes of wheat and barley which are highly expressed in the aleurone layer of the germinated seeds.