Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2011
Publication Date: 8/8/2011
Citation: Fermin, G., Keith, R.C., Suzuki, J.Y., Ferreira, S.A., Gaskill, D.A., Pitz, K.Y., Manshardt, R.M., Gonsalves, D., Tripathi, S. 2011. Allergenicity assessment of the papaya ringspot virus coat protein expressed in transgenic Rainbow papaya. Journal of Agricultural and Food Chemistry. 59(18):10006-10012. DOI: 10.1021/jf201194r. Interpretive Summary: Rainbow and SunUp are Papaya ringspot virus (PRSV) resistant genetically engineered (GE) cultivars that were commercialized in Hawaii in 1998. The resistance to PRSV is conferred by the coat protein gene (CP) of PRSV. These cultivars saved Hawaii’s papaya industry from devastation by PRSV and account for roughly 70 percent of Hawaii’s papaya production. They are currently exported to the mainland US and Canada, but have not been approved for export to Japan. However, much progress has been made in Hawaii’s efforts to deregulate the GE papaya in Japan. A major requirement of the Japan deregulation process is the determination of the potential allergenicity of the PRSV CP. Our experimental data showed that the PRSV CP did not show similarity to sequences of known allergens listed in several allergen databases. Also, CP was unstable in simulated gastric fluid (SGF), simulated intestinal fluid (SIF) and to heat. Known allergens are generally stable to those treatments. Furthermore, the CP levels in fruits of Rainbow papaya were about 87% lower than the CP level found in PRSV infected non GE papaya. The deregulation of the transgenic papaya in Japan will provide a significant boost to the export market of Hawaii’s papaya, and enhance the value of one of Hawaii’s most important fruit crops.
Technical Abstract: The virus-resistant, transgenic commercial papaya cultivars Rainbow and SunUp (Carica papaya L.) have been consumed locally in Hawaii and elsewhere in the mainland US and Canada since their release to planters in Hawaii in 1998. These cultivars are derived from transgenic papaya line 55-1 and carry the coat protein (CP) gene of Papaya ringspot virus (PRSV). The PRSV CP was evaluated for potential allergenicity, an important component in assessing the safety of food derived from transgenic plants. The transgene PRSV CP sequence of Rainbow papaya did not show more than 35% amino acid sequence homology nor did it have a stretch of eight amino acids that were identical to known allergens, two important criteria for assessing allergen protein similarity. PRSV CP was also tested for stability in simulated gastric fluid (SGF), simulated intestinal fluid (SIF) and under various heat treatments. The results showed that PRSV CP was degraded under conditions for which allergenic proteins relative to non-allergens are purported to be stable. The potential human intake of transgene-derived PRSV CP was assessed by measuring CP levels in Rainbow and SunUp along with estimating the fruit consumption rates and was compared to potential intake estimates of PRSV CP from naturally infected nontransgenic papaya. Following accepted allergenicity assessment criteria, our results show that the transgene-derived PRSV CP is not a food allergen.