T-Lymphocytes for Prevention or Treatment of Viral Infections Following Hematopoietic Stem Cell Transplantation

Viral infections are normally controlled by T-cell immunity and are a cause of significant
morbidity and mortality during the period of immune recovery after hematopoietic stem cell
transplantation (HSCT). Risk for infection is impacted by the degree of tissue mismatch
between donor and recipient and the immune status of the donor, including the degree and
length of immunosuppression following transplantation. Reactivation of latent viruses such as
cytomegalovirus (CMV), Epstein-Barr virus (EBV), and Human Herpesvirus 6B (HHV6) are common
and often cause symptomatic disease. Reactivations of the polyomaviruses BK virus and JC
virus are also common and frequently cause renal disease including hemorrhagic cystitis and
less commonly neurologic disease (pervasive multifocal leukoencephalopathy). Respiratory
viruses such as adenovirus and human parainfluenza also frequently cause infection. Antiviral
pharmacologic agents are only effective against some of these viruses; their use is costly,
and associated with significant toxicities and the outgrowth of drug-resistant mutants. As
delay in recovery of virus-specific cellular immune response is clearly associated with viral
reactivation and disease in these patients, cellular immunotherapy to restore viral-specific
immunity is an attractive option that has already been successfully used to target several of
these viruses.

To broaden the specificity of single T cells lines to include the three most common viral
pathogens of stem cell recipients, the investigators reactivated CMV and adenovirus-specific
T cells by using mononuclear cells transduced with a recombinant adenoviral vector encoding
the CMV antigen pp65 (Ad5f35CMVpp65). Subsequent stimulations with EBV-LCL transduced with
the same vector both reactivated EBV-specific T cells and maintained the expansion of the
activated adenovirus and CMV-specific T cells. This method reliably produced T cells with
cytotoxic function specific for all three viruses, which the investigators infused into 14
stem cell recipients in a Phase I prophylaxis study. The investigators observed recovery of
immunity to CMV and EBV in all patients but an increase in adenovirus-specific T cells was
only seen in patients who had evidence of adenovirus infection pre-infusion. A follow-up
study in which the frequency of adenovirus-specific T cells was increased in the infused T
cells produced similar results, thus highlighting the importance of endogenous antigen to
promote the expansion of infused T cells in vivo. Nevertheless, all patients in both clinical
trials with pre-infusion CMV, adenovirus or EBV infection or reactivation were able to clear
the infection, including one patient with severe adenoviral pneumonia requiring ventilatory
support. T cells recognizing multiple antigens can therefore produce clinically relevant
effects against all three viruses.

Recent studies have extended the number of targeted viruses, and included HHV6B, BK virus,
and Varicella-zoster virus (VZV). In a recent study, 11 patients were treated with VST
targeting 5-viruses (CMV, EBV, Adv, HHV6B, BKV) which were generated using a rapid protocol
with overlapping peptides encompassing 12 viral protein. VST infusion resulted in a 94%
antiviral response rate in these patients (complete or partial responses against CMV=3/3,
EBV=5/5, Adv=1/1, HHV6B=2/2, BKV=6/7). Two of the patients who received 5-virus VST developed
transplant-associated microangiopathy, which was deemed secondary to HSCT and unrelated to
VST infusion. One of these patients developed grade II skin GVHD, which improved with topical
therapy. In another recent study, ten adult patients were prophylactically treated with VST
specific for CMV, EBV, Adv, and Varicella (VZV). These VSTs were generated using
donor-derived dendritic cells which were infected with either Ad5f35-pp65 or with varivax
vaccine, and were then pooled and used to stimulate donor PBMCs. All ten patients were
protected against EBV, Adv, and VZV. Six patients developed CMV reactivation, but only one
required antiviral therapy. Of these 10 patients, 7 developed acute or chronic GVHD, though
compared to a non-treated group at the same institution, the rate of GVHD did not differ
significantly. Thus, it has been possible to target an extended panel of viruses with a
single VST product.

Inclusion Criteria:

Recipient Inclusion Criteria at the time of VST infusion

1. Prior myeoloablative or non-myeloablative allogeneic hematopoietic stem cell
transplant using either bone marrow or peripheral blood stem cells no earlier than 5
days prior to the date of VST infusion, AND

2. Prophylaxis for patients at risk of CMV, adenovirus, EBV, HHV6, BK virus, JC virus,
and/or HPIV3 infection, OR

3. Treatment of reactivation or active infection which is defined for each virus as below

4. Treatment may be given to eligible patients with a single or multiple infections.
Patients with multiple infections with one or more reactivation and one or more
controlled infection are eligible to enroll.

5. Clinical status at enrollment to allow tapering of steroids to less than 0.5 mg/kg/day
prednisone or equivalent.

6. Karnofsky/Lansky score of ≥ 50

7. Bilirubin <2x upper limit normal

8. AST < 5 x upper limit normal

9. Serum creatinine < 2 x upper limit normal

12. Hgb >8.0 g/dL(level can be achieved with transfusion)

13. Pulse oximetry of > 90% on room air

14. Available multivirus-specific T cells (VSTs)

15. Negative pregnancy test in female patients if applicable (childbearing potential who
have received a reduced intensity conditioning regimen).

16. Written informed consent and/or signed assent line from patient, parent or guardian.

Exclusion Criteria:

Recipient Exclusion criteria at the time of VST infusion:

1. Patients receiving ATG, Campath, Basiliximab, or other immunosuppressive T cell
monoclonal antibodies within 28 days of screening for enrollment. In patients who have
received these therapies as part of their conditioning regimens, 28 days must have
elapsed since the final dose before VST may be given.

2. Patients with other uncontrolled infections. For bacterial infections, patients must
be receiving definitive therapy and have no signs of progressing infection for 72
hours prior to enrollment. For fungal infections patients must be receiving definitive
systemic anti-fungal therapy and have no signs of progressing infection for 1 week
prior to enrollment.

Progressing infection is defined as worsening clinical symptoms, physical findings,
vital sign abnormalities (including hemodynamic instability), and/or microbiologic or
radiographic findings attributable to infection. Persisting fever without other signs
/symptoms or laboratory evidence will not be interpreted as progressing infection.

3. Patients who have received donor lymphocyte infusion (DLI) or other cellular therapies
(with the exception of the allogeneic cells relating to the transplantation) within 28
days.

4. Patients with active acute GVHD grades II-IV.

5. Active and uncontrolled relapse of malignancy

6. Patients with Grade >3 hyperbilirubinemia

7. Patients who have received investigational (IND) product within 28 days of screening
for enrollment under this study