0 6 Immune immune JJ 7 22 hyperactivation hyperactivation NN 23 25 of of IN 26 40 HIV-1-infected hiv-1-infected JJ 41 42 T t NN 43 48 cells cell NNS 49 57 mediated mediate VBN 58 60 by by IN 61 64 Tat Tat NNP 65 68 and and CC 69 72 the the DT 73 77 CD28 cd28 NN 78 85 pathway pathway NN 85 86 . . . 88 93 Human human JJ 94 110 immunodeficiency immunodeficiency NN 111 121 virus-type virus-type NN 122 123 1 1 CD 124 125 ( ( ( 125 130 HIV-1 HIV-1 NNP 130 131 ) ) ) 132 141 infection infection NN 142 144 is be VBZ 145 158 characterized characterize VBN 159 161 by by IN 162 163 a a DT 164 171 chronic chronic JJ 172 177 state state NN 178 180 of of IN 181 187 immune immune JJ 188 203 hyperactivation hyperactivation NN 204 206 in in IN 207 215 patients patient NNS 215 216 . . . 217 226 Infection infection NN 227 229 of of IN 230 235 human human JJ 236 246 peripheral peripheral JJ 247 252 blood blood NN 253 264 lymphocytes lymphocyte NNS 265 269 with with IN 270 275 HIV-1 HIV-1 NNP 276 278 in in FW 279 284 vitro vitro FW 285 293 resulted result VBD 294 296 in in IN 297 306 increased increase VBN 307 320 interleukin-2 interleukin-2 NN 321 322 ( ( ( 322 326 IL-2 il-2 NN 326 327 ) ) ) 328 337 secretion secretion NN 338 340 in in IN 341 349 response response NN 350 352 to to TO 353 354 T t NN 355 359 cell cell NN 360 370 activation activation NN 371 374 via via IN 375 378 the the DT 379 382 CD3 cd3 NN 383 386 and and CC 387 391 CD28 cd28 NN 392 401 receptors receptor NNS 401 402 . . . 403 413 Expression expression NN 414 416 of of IN 417 420 the the DT 421 426 HIV-1 HIV-1 NNP 427 441 transactivator transactivator NN 442 445 Tat Tat NNP 446 459 recapitulated recapitulate VBD 460 464 this this DT 465 474 phenotype phenotype NN 475 478 and and CC 479 482 was be VBD 483 493 associated associate VBN 494 498 with with IN 499 508 increased increase VBN 509 513 IL-2 il-2 NN 514 523 secretion secretion NN 524 526 in in IN 527 535 response response NN 536 538 to to TO 539 552 costimulation costimulation NN 553 557 with with IN 558 561 CD3 CD3 NNP 562 566 plus plus CC 567 571 CD28 cd28 NN 571 572 . . . 573 577 IL-2 il-2 NN 578 592 superinduction superinduction NN 593 595 by by IN 596 599 Tat Tat NNP 600 608 occurred occur VBD 609 611 at at IN 612 615 the the DT 616 631 transcriptional transcriptional JJ 632 637 level level NN 637 638 , , , 639 642 was be VBD 643 651 mediated mediate VBN 652 654 by by IN 655 658 the the DT 659 674 CD28-responsive cd28-responsive JJ 675 682 element element NN 683 685 in in IN 686 689 the the DT 690 694 IL-2 il-2 NN 695 703 promoter promoter NN 703 704 , , , 705 708 and and CC 709 712 was be VBD 713 724 exclusively exclusively RB 725 734 dependent dependent JJ 735 737 on on IN 738 741 the the DT 742 744 29 29 CD 745 750 amino amino NN 751 756 acids acid NNS 757 764 encoded encode VBN 765 767 by by IN 768 771 the the DT 772 778 second second JJ 779 783 exon exon NN 784 786 of of IN 787 790 Tat Tat NNP 790 791 . . .