Plant-based chimeric HPV-virus-like particles bearing amyloid-ß epitopes elicit antibodies able to recognize amyloid plaques in APP-tg mouse and Alzheimer's disease brains.

The main amyloid-beta (Aß) variants detected in the human brain are full-length Aß1-40 and Aß1-42 peptides; however, a significant proportion of AD brain Aß consists also of N-terminal truncated/modified species. The majority of the previous immunotherapeutic strategies targeted the N-terminal immunodominant epitope of the full-length Aß; however, most of the pathological N-truncated forms of Aß lack this critical B cell epitope. Recently, virus-like particles (VLPs), self-assembled structures with highly ordered repetitive patterns on their surface and capable of inducing robust immune responses, were applied as a promising platform for various antigen expressions. In this study, we expressed in plants two chimeric HPV16 L1 capsid proteins obtained by introduction of the ß-amyloid 11-28 epitope (Aß 11-28) into the h4 helix or into the coil regions of the L1 protein. The Aß 11-28 epitope was chosen because it is present in the full-length Aß 1-42 as well as in the truncated/modified amyloid peptide species. After expression, we assembled the chimerical L1/Aß 11-28 into a VLP in which the Aß 11-28 epitope is exposed at very high density (360 times) on the surface of the VLP. The chimeric VLPs elicited in mice Aß-specific antibodies binding to ß-amyloid plaques in APP-tg mouse and AD brains. Our study is the first to demonstrate a successful production in plants and immunogenic properties in mice of chimeric HPV16 L1 VLPs bearing Aß epitope that may be of potential relevance for the development of multivalent vaccines for a multifactorial disease such as AD.

Development of an edible rabies vaccine in maize using the Vnukovo strain.

The objective of this study was to obtain transgenic maize expressing the rabies virus glycoprotein (G) of the Vnukovo strain and to evaluate its immunogenicity in mice, by the oral route. The ubiquitin maize promoter fused to the whole coding region of the rabies virus G gene, and a constitutive promoter from cauliflowermosaic virus (CaMV)were used. Maize embryogenic callus were transformed with the above construct by biolistics. Regenerated maize plants were recovered and grown in a greenhouse. The presence of the G gene and its product was detected by PCR and western blot, respectively. The amount of G protein detected in the grains was approximately 1% of the total soluble plant protein. Transformed kernels containing 50 microg of G protein were given once by the oral route in adult mice (BALB-C strain). Challenge was undertaken at 90-days post-vaccination using a lethal dose of a vampire bat rabies virus (100 LD 50% in mice); vampire bats are one of the main reservoirs in Latin America. The edible vaccine induced viral neutralizing antibodies (VNA) which, protected mice 100% against challenge. The control group did not survive. The G protein of the Vnukovo strain expressed in transgenic maize may be considered as an oral immunogen against rabies, conferring cross-protection.

The use of cysteine proteinase inhibitors to engineer resistance against potyviruses in transgenic tobacco plants.

As the processing mechanism of all known potyviruses involves the activity of cysteine proteinases, we asked whether constitutive expression of a rice cysteine proteinase inhibitor gene could induce resistance against two important potyviruses, tobacco etch virus (TEV) and potato virus Y (PVY), in transgenic tobacco plants. Tobacco lines expressing the foreign gene at varying levels were examined for resistance against TEV and PVY infection. There was a clear, direct correlation between the level of oryzacystatin message, inhibition of papain (a cysteine proteinase), and resistance to TEV and PVY in all lines tested. The inhibitor was ineffective against tobacco mosaic virus (TMV) infection because processing of this virus does not involve cysteine proteinases. These results show that plant cystatins can be used against different potyviruses and potentially also against other viruses, whose replication involves cysteine proteinase activity.

Perspective: edible vaccines--a concept coming of age.

In addition to their traditional role as a source of natural medicines, it is now possible to genetically engineer plants to produce pharmaceuticals. Transgenic plants expressing antigens from pathogenic microorganisms offer many advantages as low-cost production systems and effective delivery systems for vaccines. This new technology might contribute to global vaccine programs and might have a dramatic impact on health care in developing countries.

Peroxisomal thiolase mRNA is induced during mango fruit ripening.

Fruit ripening is a complex, developmentally regulated process. A series of genes have been isolated from various ripening fruits encoding enzymes mainly involved in ethylene and cell wall metabolism. In order to aid our understanding of the molecular basis of this process in a tropical fruit, a cDNA library was prepared from ripe mango (Mangifera indica L. cv. Manila). By differential screening with RNA poly(A)+ from unripe and ripe mesocarp a number of cDNAs expressing only in ripe fruit have been isolated. This paper reports the characterization of one such cDNA (pTHMF 1) from M. indica which codes for a protein highly homologous to cucumber, rat and human peroxisomal thiolase (EC 2.3.1.16), the catalyst for the last step in the beta-oxidation pathway. The cDNA for the peroxisomal mango thiolase is 1305 bp in length and codes for a protein of 432 amino acids with a predicted molecular mass of 45,532 Da. Mango thiolase is highly homologous to cucumber thiolase (80%), the only other plant thiolase whose cloning has been reported, and to rat and human thiolases (55% and 55% respectively). It is shown by northern analysis that during fruit ripening THMF 1 is up-regulated. A similar pattern of expression was detected in tomato fruit. Wounding and pathogen infection do not appear to affect THMF 1 expression. The possible involvement of thiolase in fatty acid metabolism during fruit ripening will be discussed. To our knowledge this is the first report cloning of a plant gene involved in fatty acid metabolism showing an induction during fruit ripening.

Alternative oxidase from mango (Mangifera indica, L.) is differentially regulated during fruit ripening.

Alternative oxidase is a respiratory-chain component of higher plants and fungi that catalyzes cyanide-resistant oxygen consumption. The activity of a alternative oxidase has been detected during ripening in several climacteric fruit including mango (Mangifera indica L.). Synthetic oligonucleotides, corresponding to conserved regions of the Sauromatum guttatum and Arabidopsis thaliana nucleotide sequences, were used as primers for polymerase chain reaction to amplify genomic DNA extracted from mango leaves. The 623-bp fragment was found to encode an open reading frame of 207 amino acids showing high identity to the S. guttatum enzyme. Using this fragment to screen a ripe mango mesocarp cDNA library, one full-length cDNA clone, designated pAOMI.1, was obtained that contained an open reading frame encoding a polypeptide of 318 amino acids. The predicted amino-acid sequence exhibited 62, 64 and 68% identity to the S. guttatum, soybean, and A. thaliana enzymes respectively, indicating that this cDNA encodes a mango homologue of the alternative oxidase. Gel blot hybridization showed that pAOMI.1 is likely to be encoded by a single-copy gene. The 1.6 kb-transcript was induced during mango fruit ripening although the transcript was clearly detectable in unripe and developing fruit. Antibodies raised against the S. guttatum enzyme recognized three bands of approximately 27, approximately 33 and approximately 36 kDa from mitochondrial mango proteins. Two of the bands were detectable before ripening and increase in ripe fruit, the other band (27 kDa) was barely present in unripe fruit but accumulated during ripening. The clone pAOMI.1 was able to complement an Escherichia coli hemA mutant deficient in cytochrome-mediated aerobic respiration. This is the first report on the analysis of alternative oxidase at the molecular level during the ripening of a climacteric fruit.

Isolation and characterization of a gene involved in ethylene biosynthesis from Arabidopsis thaliana.

The ethylene forming enzyme (EFE) is a key factor in ethylene biosynthesis. To understand better the regulation of ethylene biosynthesis in vegetative tissues, we set out to isolate and characterize a complementary DNA (cDNA) encoding the EFE from Arabidopsis thaliana. An A. thaliana cDNA library was screened with pTOM 13, a tomato cDNA coding for the EFE. A cDNA clone (pEAT1) was isolated. The cDNA is 1200 nucleotides (nt) in length and predicts a protein of M(r) 36,663. The insert includes the complete open reading frame of 972 bp and shows strong homology with several reported sequences, both at the nt and amino acid level. In whole seedlings, expression of pEAT1 was enhanced by wounding, ethrel, Fe2+, and 1-amino-cyclopropane-carboxylic acid (ACC) treatments. In contrast, heat shock had no effect on the expression.