Richardson Max W, Mirchandani Jyotika, Silvera Peter, Régulier Emmanuel G, Capini Christelle, Bojczuk Paul M, Hu Jason, Gracely Edward J, Boyer Jean D, Khalili Kamel, Zagury Jean-François, Lewis Mark G, Rappaport Jay
Center for Neurovirology and Cancer Biology, Temple University, Philadelphia, Pennsylvania 19122, USA.
DNA Cell Biol. 2002 Sep;21(9):637-51. doi: 10.1089/104454902760330174.
This study compared immune responses in rhesus macaques immunized with unmodified HIV-1 IIIB Tat, SHIV89.6P Tat, and carboxymethylated IIIB and 89.6P Tat toxoids. Immunization with either IIIB or 89.6P preparation induced high titer and broadly crossreactive serum anti-Tat IgG that recognized HIV-1 subtype-E and SIVmac251 Tat. However, the response was delayed, and titers were lower in 89.6P vaccination groups. Serum anti-Tat IgG recognized peptides corresponding to the amino-terminus, basic domain, and carboxy-terminal region. Cellular proliferative responses to Tat toxoids corresponding to the immunogen were evident in vitro in both IIIB and 89.6P groups. Crossreactive proliferative responses were observed in IIIB groups in response to stimulation with 89.6P or SIVmac251 Tat toxoids, but were much less prevalent in 89.6P groups. The truncated 86 amino acid IIIB Tat appears to be more immunogenic than the 102 amino acid 89.6P Tat with respect to both humoral and cellular immune responses, and may be a better vaccine component. Despite induction of robust humoral and cellular immune responses (including both CD4+ and CD8+ T-cell responses) to Tat, all animals were infected upon intravenous challenge with 30 MID(50) of SHIV89.6P and outcome of vaccine groups was not different from controls. Sequencing both Tat exons from serum viral RNA revealed no evidence of escape mutants. These results suggest that with intravenous SHIV89.6P challenge in rhesus macaques, precipitous CD4+ T-cell decline overwhelms potentially protective immune responses. Alternatively, Tat specific CD8+ T-cell responses may not appropriately recognize infected cells in vivo in this model. In view of evidence demonstrating Tat specific CTLs in the SIV model and in humans infected with HIV-1, results in this pathogenic SHIV model may not apparently predict the efficacy of this approach in human studies. The potency and cross-reactivity of these immune responses confirm Tat toxoid as an excellent candidate vaccine component.
本研究比较了用未修饰的HIV-1 IIIB Tat、SHIV89.6P Tat以及羧甲基化的IIIB和89.6P Tat类毒素免疫的恒河猴的免疫反应。用IIIB或89.6P制剂免疫可诱导产生高滴度且具有广泛交叉反应性的血清抗Tat IgG，其可识别HIV-1 E亚型和SIVmac251 Tat。然而，反应出现延迟，且89.6P疫苗接种组的滴度较低。血清抗Tat IgG识别对应于氨基末端、碱性结构域和羧基末端区域的肽段。在IIIB和89.6P组中，体外均可见对与免疫原对应的Tat类毒素的细胞增殖反应。在IIIB组中，用89.6P或SIVmac251 Tat类毒素刺激可观察到交叉反应性增殖反应，但在89.6P组中则不太常见。就体液免疫和细胞免疫反应而言，截短的86个氨基酸的IIIB Tat似乎比102个氨基酸的89.6P Tat更具免疫原性，可能是更好的疫苗成分。尽管对Tat诱导了强烈的体液免疫和细胞免疫反应（包括CD4+和CD8+ T细胞反应），但所有动物在静脉注射30个半数感染剂量（MID）(50)的SHIV89.6P后均被感染，且疫苗组的结果与对照组无差异。对血清病毒RNA中的两个Tat外显子进行测序未发现逃逸突变体的证据。这些结果表明，在恒河猴中进行静脉注射SHIV89.6P攻击时，CD4+ T细胞的急剧下降使潜在的保护性免疫反应不堪重负。或者，在该模型中，Tat特异性CD8+ T细胞反应可能无法在体内恰当地识别受感染细胞。鉴于有证据表明在SIV模型和感染HIV-1的人类中存在Tat特异性CTL，在这种致病性SHIV模型中的结果可能无法明显预测该方法在人体研究中的疗效。这些免疫反应的效力和交叉反应性证实Tat类毒素是一种优秀的候选疫苗成分。
