|摘要: ||基因改造生物(Genetically modified organisms, GMO)泛指利用基因工程技術將遺傳物質轉殖入動物、植物及微生物，使其基因結構改變並表現轉殖入基因之功能性狀。而基因改造食品(Genetically modified foods, GMF)是指以基因改造生物為原料所生產出之食品(Celec et al., 2005)。唯國際間對基因改造食品之食用安全性仍頗有爭議。因此本次實驗主要目的為評估抗木瓜輪點病毒基因改造木瓜(823-2210)回交後果實之食用安全性。實驗分三部份，第一部份：首先進行木瓜果實樣品之分子鑑定，檢測基改木瓜中是否含有特定基因改造片段840 bp及151 bp，再進一步檢測經連續餵食基因改造木瓜(823-2210) 7天後檢查小鼠體內各臟器及胃腸道內容物中是否存有該基因改造片段。結果顯示基改木瓜果實含有基因改造片段840 bp及151 bp，而餵食基因改造木瓜之小鼠體內各臟器及胃腸道內容物中並未偵測到該基因改造片段。第二部份：以BALB/c小鼠及SD大鼠連續胃管餵食非基改木瓜(台農2號)及基改木瓜(823-2210) (1及2 g/kg) 30天及90天。另於犧牲前2天以腹腔注射cyclophosphamide (CP, 80 mg/kg)作為免疫抑制之陽性對照組。結果顯示給予CP之BALB/c小鼠胸腺及脾臟重量、週邊血液淋巴細胞(CD3+、CD4+、CD8+及CD19+)、血清及淋巴增殖上清液中IgG、IgM及細胞激素含量、LPS及Con A刺激之淋巴增殖及NK細胞活性均有顯著下降；而給予CP之SD大鼠則僅出現胸腺及脾臟重量、週邊血液淋巴細胞(CD3+、CD4+及CD8+)以及Con A刺激之淋巴增殖等數值顯著下降。相似結果出現在餵食基改木瓜高劑量組小鼠週邊血液淋巴細胞(CD8+及CD19+)，血清及淋巴增殖上清液中IgG及IgM含量、LPS刺激之淋巴增殖結果均有顯著下降，而大鼠則無，顯示兩種實驗動物結果表現並不相同。第三部份：以SD大鼠進行90天亞慢性餵食試驗以評估長期食用基因改造木瓜之安全性，結果顯示餵食基改木瓜之大鼠於體重、臟器重、血液學、血清生化學、尿液學、肉眼及組織病理學檢查等均無明顯毒性作用。綜合上述結果，基改木瓜(823-2210)於大鼠之90天免疫毒理及安全性試驗皆無明顯毒性作用，其與親本木瓜台農2號相比為實質等同。小鼠30天免疫毒理試驗於基改木瓜823-2210高劑量組(2 g/kg)則有輕微免疫抑制，屬於非顯著免疫抑制等級，其原因是否與動物敏感品系不同而有所差異或與其他因素有關，仍需進一步探討。|
Genetically modified organisms (GMO) are organisms whose genetic material has been altered using genetic engineering techniques (Celec et al., 2005). Genetically modified (GM) papaya plant resistant to infect by Papaya ringspot virus (PRSV) was generated. However, the safety of GM foods remains controversy. This study was performed to evaluate the immunotoxicity and food safety of the newly development of backcross genetically modified papaya fruits. At first, for molecular identification for the genetically modified gene fragment of backcross GM papaya fruit (coat protein gene-840 bp and 151 bp) were confirmed. Mice were gavaged with backcross GM papaya fruits for 7 days to detect the CP gene residue in body or not. Result revealed that the genetically modified gene fragment of 840 and 151 bp could be found in the GM papaya fruit, but no residue of CP genes was detected in all organs of mice. In the second part, the study was conducted to assess the immunomodulatory responses of GM papaya, Line 823-2210, and compared with its parent plant of non-GM papaya, Tainung-2 (TN-2). Both GM and non-GM papaya fruits (1 and 2 g/kg bw) were orally gavaged to BALB/c mice for 30 days and SD rats for 90 days, respectively. An immunity inhibitor of cyclophosphamide (CP, 80 mg/kg i.p., on day 29 and 30 in mice, or on day 88 and 89 in rats) was used as positive control substance. The results in mice showed that CP had significantly decreased in weights of spleen and thymus, immunophenotypic values of PBMCs (CD3+, CD4+, CD8+ and CD19+), natural killer cell activity, LPS-induced B cell proliferation, and ConA-induced T cell proliferation, respectively. In addition, CP also significantly decreased in weights of spleen and thymus, immunophenotypic values of PBMCs (CD3+, CD4+ and CD8+) and ConA-induced T cell proliferation in rats. Both GM and non-GM papaya fruits had slightly decreased in parts of immunophenotypic values of PBMCs (CD8+ and CD19+) and LPS-induced B cell proliferation in mice, but not in rats. Finally, non-GM and GM papaya (823-2210) (1 and 2 g/kg bw) was gavaged for 90 days in rats to evaluate the food safety. The parameters of body and organ weights, hematology, biochemistry, urinary and pathology showed no biologically adverse effects in rats. In conclusion, the food safety of GM papaya (823-2210) was substantial equivalence to its parent plant of non-GM papaya (TN-2) in rats. GM papaya fruits (2 g/kg bw) slightly decreased in part of immunophenotypic values in mice, but not in rats. This degree is graded as non-significant immunosuppression. The difference on immunomodulatory effects of GM papaya fruit between these two tested animals needs to elucidate in more details in the future studies.