Unité des Rétrovirus Endogènes et Eléments Rétroïdes des Eucaryotes Supérieurs, UMR 8122 CNRS, Institut Gustave Roussy, Villejuif, and Université Paris-Sud, Orsay, France.
J Virol. 2014 Jan;88(2):992-1001. doi: 10.1128/JVI.02234-13. Epub 2013 Nov 6.
We previously delineated a highly conserved immunosuppressive (IS) domain within murine and primate retroviral envelope proteins that is critical for virus propagation in vivo. The envelope-mediated immunosuppression was assessed by the ability of the proteins, when expressed by allogeneic tumor cells normally rejected by engrafted mice, to allow these cells to escape, at least transiently, immune rejection. Using this approach, we identified key residues whose mutation (i) specifically abolishes immunosuppressive activity without affecting the "mechanical" function of the envelope protein and (ii) significantly enhances humoral and cellular immune responses elicited against the virus. The objective of this work was to study the immunosuppressive activity of the envelope protein (p15E) of feline leukemia virus (FeLV) and evaluate the effect of its abolition on the efficacy of a vaccine against FeLV. Here we demonstrate that the FeLV envelope protein is immunosuppressive in vivo and that this immunosuppressive activity can be "switched off" by targeted mutation of a specific amino acid. As a result of the introduction of the mutated envelope sequence into a previously well characterized canarypox virus-vectored vaccine (ALVAC-FeLV), the frequency of vaccine-induced FeLV-specific gamma interferon (IFN-γ)-producing cells was increased, whereas conversely, the frequency of vaccine-induced FeLV-specific interleukin-10 (IL-10)-producing cells was reduced. This shift in the IFN-γ/IL-10 response was associated with a higher efficacy of ALVAC-FeLV against FeLV infection. This study demonstrates that FeLV p15E is immunosuppressive in vivo, that the immunosuppressive domain of p15E can modulate the FeLV-specific immune response, and that the efficacy of FeLV vaccines can be enhanced by inhibiting the immunosuppressive activity of the IS domain through an appropriate mutation.
我们先前在鼠类和灵长类逆转录病毒包膜蛋白中描绘了一个高度保守的免疫抑制（IS）结构域，该结构域对于病毒在体内的繁殖至关重要。通过蛋白质的表达来评估包膜介导的免疫抑制作用，这些蛋白质由异体肿瘤细胞表达，这些肿瘤细胞通常会被移植的小鼠排斥，从而使这些细胞至少暂时逃避免疫排斥。使用这种方法，我们确定了关键残基，其突变（i）特异性地消除了免疫抑制活性而不影响包膜蛋白的“机械”功能，以及（ii）显著增强了针对病毒的体液和细胞免疫反应。这项工作的目的是研究猫白血病病毒（FeLV）包膜蛋白（p15E）的免疫抑制活性，并评估其消除对 FeLV 疫苗功效的影响。在这里，我们证明 FeLV 包膜蛋白在体内具有免疫抑制活性，并且这种免疫抑制活性可以通过靶向突变特定氨基酸来“关闭”。由于将突变的包膜序列引入先前经过充分表征的金丝雀痘病毒载体疫苗（ALVAC-FeLV）中，疫苗诱导的 FeLV 特异性γ干扰素（IFN-γ）产生细胞的频率增加，而相反，疫苗诱导的 FeLV 特异性白细胞介素-10（IL-10）产生细胞的频率降低。IFN-γ/IL-10 反应的这种转变与 ALVAC-FeLV 对 FeLV 感染的更高功效相关。这项研究表明，FeLV p15E 在体内具有免疫抑制作用，p15E 的免疫抑制结构域可以调节 FeLV 特异性免疫反应，并且通过适当的突变抑制 IS 结构域的免疫抑制活性可以增强 FeLV 疫苗的功效。
