Generation and Characterization of a Third Party GMP Grade Bank of CMV Specific T-Cells for Adoptive Immunotherapy of CMV Infections in Recipients of HSCT from Cord Blood or Seronegative Donors

Adoptive transfer of virus-specific T-cells (CTLs) from HLA partially matched 3^rdparty donors can effectively treat EBV, CMV or Adv infections in recipients of HSCT from seronegative or cord blood donors.  However, in vitro generated CTLs selectively react against 1-3 immunodominant (ID) epitopes (eps) presented by 1-2 HLA alleles.  Therefore, to be effective, it is critical that administered CTLs respond to eps presented by HLA alleles shared by the recipient. To address this, we established a bank of 123 GMP grade CMV-CTLs generated using CMVpp65 peptide pool loaded autologous APCs.  Each CTL was characterized as to eps specificity and restricting HLA allele. 

The pool of CTL donors inherited HLA alleles in frequencies similar to those in caucasian and black populations, with certain alleles overrepresented.   In 55% of the CTL lines, the ID T-cell response (TCr) was restricted (restr.) by 3 HLA alleles: A0201(25%), B0702(21%) and B 3501-11(9%); 45% of CTL lines were restr. by other class-I alleles, and 17/123(14%) were restr. by class-II alleles. Certain CMVpp65 15 mers contained overlapping eps presented by both class-I and class-II, which elicited more robust TCr.  CTLs from all B0702⁺ donors (26/26) were restr. by B0702.  In comparison, CTLs from 30/39(77%) A0201⁺ donors and 9/19 (47%) HLA B3501-11⁺ donors were restr. by A0201 and B3501-11 respectively.   Donors co-inheriting A0201 and B 0702 (9/9) universally demonstrated B0702 restr. ID TCr.  In comparison, 11/12 (91.6%) donors co-inheriting A0201 and B 4401-04 demonstrated HLA A0201 restr. CTLs.  Strikingly, only 1/123 and 0/123 A1101⁺ and A0301⁺ donors respectively demonstrated CTLs restr. by these commonly inherited class –I alleles. This analysis thus indicates an immunodominance hierarchy for CMVpp65 eps and their presenting HLA alleles. In a series of 239 MUD, 137 MMUD, and 100 DUCB consecutive HSCT at MSKCC, we could identify an immediately available CMVpp65 specific CTL line matched with the patient at 2-3 alleles and restr. by a shared HLA allele in this GMP-CTL bank in 86%, 89% and 80% cases respectively.  This CTL bank thus provides a clinical reagent for the treatment of CMV infections in HSCT recipients.  The delineated immunodominance hierarchy for CMVpp65 may also facilitate selection of an appropriately restr. CTL line for treatment with predicted activity in the recipient.  We can also successfully generate CMV-CTLs against subdominant CMVpp65 eps presented prevalent HLA alleles using a panel of artificial antigen presenting cells (AAPCs). Expansion of this bank with CTLs generated with AAPCs can broaden its applicability to almost all HSCT recipients.