Immunotherapy with CD25/CD71-allodepleted T cells to improve T-cell reconstitution after matched unrelated donor hematopoietic stem cell transplant: a randomized trial

BACKGROUND AND AIMS: Delayed immune reconstitution is a major challenge after matched unrelated donor (MUD) stem cell transplant (SCT). In this randomized phase 2 multi-center trial, Adoptive Immunotherapy with CD25/71 allodepleted donor T cells to improve immunity after unrelated donor stem cell transplant (NCT01827579), the authors tested whether allodepleted donor T cells (ADTs) can safely be used to improve immune reconstitution after alemtuzumab-based MUD SCT for hematological malignancies. METHODS: Patients received standard of care or up to three escalating doses of ADTs generated through CD25+/CD71+ immunomagnetic depletion. The primary endpoint of the study was circulating CD3+ T-cell count at 4 months post-SCT. Twenty-one patients were treated, 13 in the ADT arm and eight in the control arm. RESULTS: The authors observed a trend toward improved CD3+ T-cell count at 4 months in the ADT arm versus the control arm (230/µL versus 145/µL, P = 0.18), and three ADT patients achieved normal CD3+ T-cell count at 4 months (>700/µL). The rates of significant graft-versus-host disease (GVHD) were comparable in both cohorts, with grade ≥2 acute GVHD in seven of 13 and four of eight patients and chronic GVHD in three of 13 and three of eight patients in the ADT and control arms, respectively. CONCLUSIONS: These data suggest that adoptive transfer of ADTs is safe, but that in the MUD setting the benefit in terms of T-cell reconstitution is limited. This approach may be of more use in the context of more rigorous T-cell depletion

Human helper T cell responses to RSV infection

Respiratory Syncytial virus (RSV) remains one of the most important causes of severe respiratory infection worldwide. Natural immunity is only partially protective, and no safe and effective vaccine has so far been found. CD4+ T cells play an essential role in shaping cellular and humoral immune responses. They have been shown to provide signals that are necessary for full differentiation of CD8+ T cells and B cells, as well as exhibiting direct anti-viral functions. However, their role in human RSV infection is poorly understood. Among the reasons for this are restrictions on sampling during the course of human infection and a resultant lack of tools to allow the study of antigen-specific CD4+ T cell responses. Further understanding of their role in the generation of effective immunity is essential for the development of better vaccines. Using an established experimental human challenge model, we inoculated 49 healthy adult volunteers with live, virulent RSV (Memphis 37). We analysed viral load by quantitative PCR (qPCR) on nasal lavage samples. Subjects were deemed infected if RSV was detectable on two consecutive days between day 2 and day 10 post inoculation. RSV infection developed in 26/49 (53%) of volunteers. In those infected, viral load peaked at day 7 and occurred at the same time as the peak symptoms score. Analysis of peripheral blood mononuclear cells (PBMCs) and BAL cells revealed the peak of polyclonal CD4+ T cell responses at day 10, characterised by the expression of the activation marker CD38 and proliferation marker Ki-67. At this time-point, RSV-specific CD4+ T cells were producing Th1 cytokines IFN- and TNF- To understand this response in greater detail, we generated a custom RSV M37 peptide library covering the complete RSV proteome. Using IFN- ELISpot, candidate epitopes were found in the F, G, M and N proteins. Of these, the most immunodominant CD4+ T cell epitopes were within the major surface glycoproteins F and G. Their class II restriction was established by depletion of CD8+ T cells from PBMCs and were confirmed by functional analysis of PBMCs from HLA class II matched donors. Using these, MHC class II-peptide tetramers using F and G peptides were constructed for the first time. RSV-specific CD4+ T cells were detectable in PBMCs of infected subjects at day 10, and exhibited the phenotypic markers of effector and effector memory T cells. These were highly activated but showed less evidence of proliferation than RSV-specific CD8+ T cells generated at the same time. Thus, the T cell response to RSV in healthy adults displays broad specificity but immunodominant CD4+ T cells primarily recognize peptides from the surface proteins F and G. Our studies imply the importance of Th1 and follicular helper T cells in the response to infection and provide novel tools that will allow further characterisation of RSV-specific CD4+ T cells in peripheral blood and lower airway.Open Acces

CD19/CD22 targeting with co-transduced CAR T-cells to prevent antigen negative relapse after CAR T-cell therapy of B-ALL

CD19-negative relapse is a leading cause of treatment failure after Chimeric antigen receptor (CAR) T-cell therapy for ALL. We investigated a CAR T-cell product targeting CD19 and CD22 generated by lentiviral co-transduction with vectors encoding our previously-described fast-off rate CD19CAR (AUTO1) combined with a novel CD22CAR capable of effective signalling at low antigen density. Twelve patients with advanced B-ALL were treated (CARPALL study, NCT02443831), a third of whom had failed prior licensed CAR therapy. Toxicity was similar to that of AUTO1 alone, with no cases of severe cytokine release syndrome. Ten of 12 patients (83%) achieved a Measurable Residual Disease (MRD) negative complete remission at 2 months post infusion. Of 10 responding patients, 5 had emergence of MRD (2) or relapse (3) with CD19 and CD22 expressing disease associated with loss of CAR T-cell persistence. With a median follow-up of 8.7 months there were no cases of relapse due to antigen-negative escape. Overall survival was 75% (95%CI: 41-91%) at 6 and 12 months. Six and 12-month event free survival (EFS) were 75% (95%CI: 41-91%) and 60% (95%CI: 23-84%). These data suggest dual targeting with co-transduction may prevent antigen negative relapse after CAR T-cell therapy