Our PRSV CP digestibility results in gastrointestinal fluids as well as our bioinformatics analyzes showed that the transgenic CP protein expressed in Rainbow and SunUp papaya is not allergenic. PRSV CP is the major protein expressed in rainbow papaya, with the plant transformation markers nptII and GUS widely used. We will discuss only the CP protein here, as the food safety of NPTII and GUS has been addressed elsewhere (24-26). Prediction of the allergenicity of new proteins relies on bioinformatics and/or experimental approaches (6, 7). Following bioinformatics analysis, PRSV CP did not show significant similarity to known allergenic proteins based on the criterion of an identical match of eight amino acids (27). However, we performed a more stringent similarity search criterion of a six amino acid identity match to the query CP sequences which identified only five entries in the SDAP database. Although we identified a very small number of matches to known allergens based on a six amino acid similarity search, numerous reports indicate that the high percentage of allergenic proteins identified using this criterion are false positives (31, 32) and therefore cannot accurately predict allergenic proteins. A computational allergenicity prediction report by Kleter and Peijnenburg (28) identified a six amino acid peptide (EKQKEK) shared by PRSV CP and a proposed allergen ABA-1, a protein from the human parasite Ascaris lumbricoides or porcine parasite. Ascaris suum. However, as noted by Suzuki et al. (29), the correspondence of PRSV CP to ABA-1 is not relevant with respect to allergenicity for several reasons: 1) the amino acid sequence is not repeated in the protein sequence d envelope, therefore it will not trigger the IgE response associated with allergens, 2) the allergenic peptide proposed by ABA-1 has not been shown to be intrinsically allergenic outside the context of other Ascaris proteins (30), and 3) it is not one of the officially recognized allergens present in the allergen database of the International Union of Immunological Societies (IUIS) (http://www.allergen.org). An important aspect of assessing potential allergenicity is to experimentally test properties common to allergenic proteins, such as stability in simulated gastrointestinal fluids, which include SGF and FIS. SGF was developed to represent conditions in the human stomach (20) and consists primarily of the major gastric protease, pepsin, in a low pH medium. Some data suggests that proteins sensitive to gastrointestinal digestion are inherently safer than those that are stable, particularly in terms of allergenicity. (5).