Immune therapy for EBV infections after hemopoietic stem-cell transplant.

Reactivation of EBV after BMT from a mismatched family member or MUD frequently leads to lymphoproliferation, which is often fatal. The risk of EBV-related lymphoma is 5‐25% after T-cell-depleted BMT from an unrelated or a mismatched-related donor [1]. While unmanipulated donor T cells are effective therapy, this treatment is complicated by GvHD [2‐4]. Since 1993, we have generated donor-derived EBV-specific cytotoxic T-lymphocytes (CTLs) and administered them as prophylaxis and treatment for this complication [5‐7]. Sixty patients received a T-cell-depleted BMT from a MUD or haploidentical family donor. Fifty-seven of these patients received prophylactic CTLs, and their 5-year overall survival is 71%. Two patients developed exacerbations of pre-existing GvHD within 1 month post-infusion. Nine of the patients on the prophylaxis study had evidence of incipient EBV lymphoma prior to CTL infusion. In six patients the abnormalities resolved without sequelae after CTL infusion. The other three developed local inflammation during a therapeutic response, with one developing adenoid enlargement with necrosis, one developing fever and a left lower lobe (LLL) pulmonary infiltrate, and the third a transient elevation in transaminases. None of the 56 patients in the prophylaxis study developed EBV lymphoma, compared with an incidence of 11.5% for patients not receiving prophylaxis [7]. Three patients not enrolled on the prophylaxis study received CTLs as treatment for EBV lymphoproliferative disease (LPD) [7]. One patient died with progressive disease because the tumor virus had deleted viral epitopes that dominated the donor immune response to EBV [8]. This illustrates one anticipated problem of immunotherapy: that the tumor will mutate to avoid the immune response. The other two patients who were treated for clinically evident EBV-LPD attained prolonged remission after CTL infusion. In situ hybridization and semiquantitative PCR showed that the gene-marked CTL had selectively accumulated at disease sites. One patient who received CTLs for bulky established disease developed initial tumor swelling and respiratory obstruction due to inflammation during the therapeutic response [7]. The CTLs of the first 26 patients were marked with the neo gene to track their persistence. Real-time PCR assay showed that the marker gene persisted for up to 78 months in peripheral blood [9]. Multiple integration sites were demonstrated on inverse PCR studies, confirming the persistence of multiple clones. Polyclonal donor-derived EBV-specific T-cell lines can therefore be used safely to prevent EBV-related immunoblastic lymphoma post-alloBMT, with long-term persistence of adoptively transferred cells. However, infusion of CTLs in patients with active or incipient disease may produce morbidity secondary to tissue inflammation at sites of disease. This approach is now being extended to other viruses that produce posttransplant morbidity and to other EBV-associated malignancies. In other EBV-associated primary malignancies, tumor cells may be less susceptible to immunotherapeutic approaches because they express a more restricted array of subdominant EBV-encoded Ags [1]. For example, in patients with EBV-genome-positive HD (EBV1 ve HD), Reed Sternberg cells express only LMP-1, LMP-2 and EBNA-1. In polyclonal CTL lines, the majority of clones recognize the more immunodominant EBNA-3 family of Ags and only a few, if any, clones will recognize subdominant Ags [10]. Nevertheless, such lines do contain LMP-2 specific clones, and we observed an increase in LMP2 specific cells after infusion, measured by tetramer analysis