Subchronic Immunotoxicity Assessment of Genetically Modified Virus-Resistant Papaya in Rats

Papaya is an important fruit that provides a variety of vitamins with nutritional value and also holds some pharmacological properties, including immunomodulation. Genetically modified (GM) papaya plants resistant to Papaya ringspot virus (PRSV) infection have been generated by cloning the coat protein gene of the PRSV which can be used as a valuable strategy to fight PRSV infection and to increase papaya production. In order to assess the safety of GM papaya as a food, this subchronic study was conducted to assess the immunomodulatory responses of the GM papaya line 823-2210, when compared with its parent plant of non-GM papaya, Tainung-2 (TN-2), in Sprague-Dawley (SD) rats. Both non-GM and GM 823-2210 papaya fruits at low (1 g/kg bw) and high (2 g/kg bw) dosages were administered via daily oral gavage to male and female rats consecutively for 90 days. Immunophenotyping, mitogen-induced splenic cell proliferation, antigen-specific antibody response, and histopathology of the spleen and thymus were evaluated at the end of the experiment. Results of immunotoxicity assays revealed no consistent difference between rats fed for 90 days with GM 823-2210 papaya fruits, as opposed to those fed non-GM TN-2 papaya fruits, suggesting that with regard to immunomodulatory responses, GM 823-2210 papaya fruits maintain substantial equivalence to fruits of their non-GM TN-2 parent.