Clémenceau B, Jégou D, Martignat L, Saï P
Cellular and Molecular Immuno-Endocrinology, INRA/ENVN/University, Nantes, France.
Diabetologia. 2002 Jun;45(6):914-23. doi: 10.1007/s00125-002-0832-7. Epub 2002 May 15.
AIMS/HYPOTHESIS: Pig islets could transmit porcine endogenous retroviruses (PERV) to diabetic patients. Our previous work showed that pig islets expressed low levels of PERV mRNA and were not likely to transmit PERV to human cells in vitro. The real risk of infection during pig tissue xenografts can only be evaluated by in vivo experiments.
Nude mice bearing tumours containing human 293 cells were grafted with specific pathogen-free pig islets or PERV-producing pig PK15 cells to determine whether pig cells could transmit PERV to mouse and human cells in vivo. Infection was monitored by PCR, long PCR, RT-PCR and long RT-PCR. As detection of PERV sequences could be due to the presence of residual pig cells, we looked for pig mitochondrial (mt) DNA. Quantitative PCR for PERV and pig mt DNA was done to compare the PERV-to-pig mt (P-to-M) ratio of each sample with the reference ratio for grafted pig cells.
Among 78 mouse tissues from PK15-grafted mice, 54 and 72 were positive for gag and pig mt DNA, respectively. Human tumours developed in these mice were positive for PERV (78%) and pig mt (89%). The P-to-M ratios for mouse tissues and PERV-positive human tumours from PK15-grafted mice were higher than the ratio in PK15 cells. Among 41 tissues from pig islet cell-grafted mice, 7 were positive for PERV (3 lymph nodes, 1 kidney, 2 salivary glands, 1 ovary), and 14 were positive for pig mt DNA. Three of these samples (1 lymph node, 1 kidney and 1 salivary gland) were positive for gag DNA, but negative for pig mt DNA. One human tumour in these mice was positive for PERV DNA. P-to-M reference ratio in grafted islet cells was 0.05+/-0.03. The three PERV-positive lymph nodes contained 78 gag/3 mt copies (P-to-M: 26), 101 gag/3 mt copies (P-to-M: 34), and 4 gag/0 mt copies. The two PERV-positive salivary glands contained 14 gag/1 mt copies, and 28 gag/0 mt copies. The ovary and the kidney contained 46 gag/3 mt and 69 gag/0 mt copies, respectively. The PERV-positive human tumour contained 47 gag/3 mt copies.
CONCLUSIONS/INTERPRETATION: Microchimerism and PERV transmission were frequently observed in both mouse and human tissues during grafting of pig PK15 cells into nude mice bearing human tumours, and sometimes during pig islet xenograft in this model. This strengthens the notion that there is a risk of transmitting PERV during pig islet xenograft.
目的/假设：猪胰岛可能会将猪内源性逆转录病毒（PERV）传播给糖尿病患者。我们之前的研究表明，猪胰岛中PERV mRNA表达水平较低，并且在体外不太可能将PERV传播给人类细胞。猪组织异种移植期间的实际感染风险只能通过体内实验来评估。
将携带含人293细胞肿瘤的裸鼠移植无特定病原体的猪胰岛或产生PERV的猪PK15细胞，以确定猪细胞在体内是否能将PERV传播给小鼠和人类细胞。通过PCR、长PCR、RT-PCR和长RT-PCR监测感染情况。由于检测到PERV序列可能是由于残留猪细胞的存在，我们检测了猪线粒体（mt）DNA。对PERV和猪mt DNA进行定量PCR，以比较每个样本的PERV与猪mt（P-to-M）比率与移植猪细胞的参考比率。
在移植PK15细胞的小鼠的78个组织中，分别有54个和72个组织的gag和猪mt DNA呈阳性。这些小鼠中生长的人肿瘤的PERV（78%）和猪mt（89%）呈阳性。移植PK15细胞的小鼠的小鼠组织和PERV阳性人肿瘤的P-to-M比率高于PK15细胞中的比率。在移植猪胰岛细胞的小鼠的41个组织中，7个组织的PERV呈阳性（3个淋巴结、1个肾脏、2个唾液腺、1个卵巢），14个组织的猪mt DNA呈阳性。其中3个样本（1个淋巴结、1个肾脏和1个唾液腺）的gag DNA呈阳性，但猪mt DNA呈阴性。这些小鼠中的1个人肿瘤的PERV DNA呈阳性。移植胰岛细胞中的P-to-M参考比率为0.05±0.03。3个PERV阳性淋巴结分别含有78个gag/3个mt拷贝（P-to-M：26）、101个gag/3个mt拷贝（P-to-M：34）和4个gag/0个mt拷贝。2个PERV阳性唾液腺分别含有14个gag/1个mt拷贝和28个gag/0个mt拷贝。卵巢和肾脏分别含有46个gag/3个mt拷贝和69个gag/0个mt拷贝。PERV阳性人肿瘤含有47个gag/3个mt拷贝。
结论/解读：将猪PK15细胞移植到携带人肿瘤的裸鼠体内时，在小鼠和人类组织中均频繁观察到微嵌合体和PERV传播，在该模型中猪胰岛异种移植时有时也会出现这种情况。这强化了猪胰岛异种移植期间存在传播PERV风险的观点。
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