Takahashi H, Houghten R, Putney S D, Margulies D H, Moss B, Germain R N, Berzofsky J A
Molecular Immunogenetics and Vaccine Research Section, National Cancer Institute, Bethesda, Maryland 20892.
J Exp Med. 1989 Dec 1;170(6):2023-35. doi: 10.1084/jem.170.6.2023.
In H-2d mice, the immunodominant determinant of the HIV-1-IIIB gp160 envelope glycoprotein recognized by CD8+ CTL is represented by a 15-residue synthetic peptide (315-329: RIQRGPGRAFVTIGK). This peptide is seen in association with the Dd class I MHC molecule expressed on H-2k L cell fibroblast targets. We explored the structural requirements for CTL recognition of this peptide at the levels of both the peptide molecule and the class I MHC molecule. Using several transfectants expressing recombinant Dd/Ld molecules, we found that presentation of this epitope required both the alpha 1 and alpha 2 domains of the Dd molecule, in contrast to certain instances of allorecognition for which alpha 1 of Dd was sufficient in association with alpha 2 of Ld. Because this peptide derives from a hypervariable segment of the HIV envelope, substituted peptides could be used to define not only the structures affecting interaction of peptide with class I MHC molecule and with the TCR, but also the structural basis for the effect of naturally occurring viral variation on CTL recognition. The CTL-LINE specific for this HIV-1-IIIB-derived sequence could not recognize the HIV-1-RF variant-derived sequence from exactly the same site (315-329:--HIGPGRVIYATGQ). Peptides with single amino acid substitutions from the HIV-1-IIIB sequence toward the HIV-1-RF sequence were made to test the effect of each residue significantly affected recognition, and only one, 324(F), was obligatory. Moreover, both 322(R) and 324(F) substituted peptides failed to inhibit the binding of the wild type peptide to the MHC molecule. Therefore, the amino-acids 322(R) and 324(F) seem to be involved in regulating peptide interaction with the Dd class I MHC molecule. In contrast, 325(V) appeared to affect interaction with the TCR. We suggest that sequence variations among known HIV-1 isolates that affect peptide binding to MHC such as those described here, if occurring during the course of infection of an individual, could result in failure of the MHC molecules of that individual to present the peptide. If the number of dominant HIV CTL epitopes is indeed very limited, such a blind spot could allow the virus to escape immune control, proliferate rapidly, and cause AIDS.
在H-2d小鼠中，CD8⁺CTL识别的HIV-1-IIIB gp160包膜糖蛋白的免疫显性决定簇由一个15个残基的合成肽（315-329：RIQRGPGRAFVTIGK）代表。在H-2k L细胞成纤维细胞靶标上表达的Dd I类MHC分子可与该肽结合。我们在肽分子和I类MHC分子水平上探讨了CTL识别该肽的结构要求。使用几种表达重组Dd/Ld分子的转染子，我们发现该表位的呈递需要Dd分子的α1和α2结构域，这与某些同种异体识别情况相反，在那些情况中，Dd的α1与Ld的α2结合就足够了。由于该肽源自HIV包膜的高变区，因此取代肽不仅可用于确定影响肽与I类MHC分子及TCR相互作用的结构，还可用于确定自然发生的病毒变异对CTL识别产生影响的结构基础。针对源自该HIV-1-IIIB序列的CTL-LINE无法识别来自完全相同位点（315-329：--HIGPGRVIYATGQ）的HIV-1-RF变异体衍生序列。制备了从HIV-1-IIIB序列向HIV-1-RF序列进行单个氨基酸取代的肽，以测试每个残基的影响，结果发现只有一个残基，即324（F），是必需的。此外，322（R）和324（F）取代的肽均未能抑制野生型肽与MHC分子的结合。因此，氨基酸322（R）和324（F）似乎参与调节肽与Dd I类MHC分子的相互作用。相比之下，325（V）似乎影响与TCR的相互作用。我们认为，已知HIV-1分离株之间影响肽与MHC结合的序列变异，如此处所述，如果在个体感染过程中发生，可能导致该个体的MHC分子无法呈递该肽。如果主要的HIV CTL表位数量确实非常有限，这样的盲点可能会使病毒逃避免疫控制，迅速增殖并导致艾滋病。
