McGregor Christopher G A, Kogelberg Heide, Vlasin Michal, Byrne Guerard W
Institute of Cardiovascular Sciences, University College London, UK.
J Heart Valve Dis. 2013 May;22(3):383-90.
Current biological heart valves (BHVs) contain the major xenogeneic antigen Gal. Recipient anti-Gal antibody binding to such an implanted BHV may contribute to valve degeneration. The study aim was to compare, by implantation in non-human primates, the immune consequences of BHVs from Gal-positive wild-type (WT) pigs and those from alpha-galactosyltransferase knockout (GTKO) pigs.
Recipients were immunized prior to implant with keyhole limpet hemocyanin (KLH) conjugated to alphaGal to match the anti-Gal levels and isotypes found in humans. Stented glutaraldehyde-fixed BHVs from WT (n = 4) and GTKO (n = 3) pigs were commercially manufactured and implanted in the mitral position in non-human primates. Recipients were treated with enoxaparin (1 mg/kg b.i.d.) for five weeks which was tapered, and then discontinued. Serum antibody levels to Gal and KLH were measured using ELISA.
Overall anti-Gal and anti-KLH antibody levels were decreased in both WT and GTKO BHV recipients after implantation. Serum anti-Gal IgG levels in GTKO BHV recipients fell rapidly within one month, matching the loss of anti-KLH reactivity. There was no significant difference in retention of anti-KLH antibody between the groups. WT BHV recipients retained significantly elevated levels of anti-Gal IgG during the first year post implant. Area under the curve analysis showed that anti-Gal IgG was significantly increased in the WT BHV group compared to GTKO BHV recipients (p < 0.01).
Persistent and significantly (p < 0.01) elevated levels of anti-Gal IgG were observed in WT but not GTKO BHV non-human primate recipients, and indicated a continuing BHV-specific immune stimulation to the alphaGal antigen. These data support the hypothesis that the clinical use of Gal-positive xenogeneic bioprosthetic materials can induce an anti-Gal antibody response. Bioprosthetic devices prepared from GTKO pig tissue would eliminate immune stimulation to this major xenoreactive antigen, which may reduce the potential of immune-mediated injury and degeneration.
目前的生物心脏瓣膜（BHV）含有主要的异种抗原半乳糖（Gal）。受体的抗Gal抗体与植入的此类BHV结合可能导致瓣膜退变。本研究的目的是通过在非人灵长类动物体内植入，比较来自Gal阳性野生型（WT）猪和α-半乳糖基转移酶基因敲除（GTKO）猪的BHV的免疫后果。
在植入前，用与αGal偶联的钥孔戚血蓝蛋白（KLH）对受体进行免疫，以匹配人类中发现的抗Gal水平和同种型。来自WT猪（n = 4）和GTKO猪（n = 3）的带支架的戊二醛固定BHV由商业制造，并植入非人灵长类动物的二尖瓣位置。受体接受依诺肝素（1 mg/kg，每日两次）治疗五周，然后逐渐减量并停药。使用酶联免疫吸附测定法（ELISA）测量血清中针对Gal和KLH的抗体水平。
植入后，WT和GTKO BHV受体的总体抗Gal和抗KLH抗体水平均降低。GTKO BHV受体的血清抗Gal IgG水平在一个月内迅速下降，与抗KLH反应性的丧失相匹配。两组之间抗KLH抗体的保留率没有显著差异。WT BHV受体在植入后的第一年中抗Gal IgG水平显著升高。曲线下面积分析表明，与GTKO BHV受体相比，WT BHV组的抗Gal IgG显著增加（p < 0.01）。
在WT而非GTKO BHV非人灵长类动物受体中观察到抗Gal IgG水平持续且显著（p < 0.01）升高，这表明对αGal抗原存在持续的BHV特异性免疫刺激。这些数据支持以下假设：Gal阳性异种生物假体材料的临床应用可诱导抗Gal抗体反应。由GTKO猪组织制备的生物假体装置将消除对这种主要异种反应性抗原的免疫刺激，这可能降低免疫介导损伤和退变的可能性。
