Absence Of Cell-mediated Immunity Research Articles

First-Line Therapy with Donor Derived HCMV-Specific T Cells Reduce Persistent HCMV Infection after Allogenic Stem Cell Transplantation

Background: Human cytomegalovirus (HCMV) infection, especially persistent HCMV infection, is an important cause of morbidity and mortality after allogenic stem cell transplantation (allo-SCT). Antiviral agents remain the mainstay of treatment and are recommend as the first-line therapy for HCMV. However, drugs are associated with significant toxicity, and their efficacy is limited in the absence of cell-mediated immunity. In recent years, adoptive immunotherapy with HCMV-specific T cells (CTLs) has been developed as an alternative option for HCMV, and data from previous studies have indicated that infusion of CTLs at early-stage of HCMV infection may have better benefits compared to salavage therapy. However, because CTLs remains time consuming and cost-intensive, so far there have no reports of first-line therapy with CTLs for HCMV infection, and the mechanisms driving the sustained antiviral immunity induced by adoptive T cells transfer remain undetermined. Our previous study had demonstrated that patients with acute graft-versus-host disease (aGVHD) were at high risk to develop persistent HCMV infection. Therefore, in the current study, we selected patients who developed aGVHD before HCMV reactivated and started CTLs generation in advance. This risk-stratified measure successfully selected patients who had high risk resisting to conventional anti-HCMV therapy , and spared low risk patients as well, making it feasible and financially viable to use CTLs as a first-line therapy.Aims: To provide robust support for the safety and efficacy of CTLs given as a first-line therapy for HCMV infection after allo-SCT, and gain some insight into the underlying mechanisms.Methods: Firstly, using humanized HCMV infected mice model, we explored where the adoptive transferred CTLs cells trafficked, evaluated the antiviral efficacy of CTLs and investigated the recovery of HCMV-specific immunity after T cell transfer. Secondly, we conducted a prospective clinical trial enrolled 35 allo-SCT patients who diagnosed with acute GVHD and had high risk developing persistent HCMV infection, intervened with antiviral agents combined with CTLs as first-line therapy and evaluated the long-term safety and durability of antiviral responses. As controls, we selected a cohort of 70 high-risk patients as well as another cohort of 70 low-risk patients who only received antiviral agents as first-line therapy without CTLs. We also evaluated the immune response after infusion and analyzed the association between immune recovery and HCMV clearance.Results: i) In humanized HCMV infection mice, adoptive infused CTLs had the ability to homing to organs, and effectively combated systemic HCMV infection by promoting the restoring of stem cell derived endogenous HCMV-specific immunity. ii) In clinical trial, first-line therapy with CTLs significantly reduced the rate (2.86% vs. 20.00%, P=0.018) and the cumulative incidence (HR=7.60, 95%CI=1.22-10.15, P=0.020) of persistent HCMV infection, and showed a lower one-year treatment related mortality (TRM) (HR=6.83, 95%CI=1.16-8.90, P=0.030) and a better one-year overall survival (OS) (HR=6.35, 95%CI=1.05-9.00, P=0.040) compared to high-risk control cohort. The cumulative incidence of persistent HCMV infection, one-year TRM and OS in CTL cohort were comparable to those in low-risk control cohort. Moreover, first-line therapy with CTLs promoted the quantitative and functional recovery of CTLs in patients, which was associated with HCMV clearance.Conclusion: In this study, we firstly demonstrated the safety and efficacy of CTLs administration as a first-line therapy for HCMV infection in humanized HCMV infection mice, and in a large clinical cohort study. The data provided robust support for the benefits of donor derived CTLs in treating HCMV infection as a first-line therapy, and suggested that infused CTLs might probably stimulate the recovery of donor derived HCMV-specific immunity. This trial was registered at www.clinicaltrials.gov as #NCT02985775. DisclosuresNo relevant conflicts of interest to declare.

Megakaryocyte Abnormalities Occur In The Absence Of Cell-Mediated Immunity In a Murine Model Of Passive Immune Thrombocytopenia (ITP)

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by increased peripheral immune platelet destruction and megakaryocyte defects in the bone marrow. Although ITP was originally thought to be primarily due to humoral mediated autoimmunity it is now evident that T cells can also play a contributing role to the thrombocytopenia. In fact, the exact interplay between platelet destruction, megakaryocyte dysfunction, and the elements of both the humoral and cell mediated immune systems still remain incompletely defined. In murine passive models of ITP, the direct administration of anti-platelet antibodies can result in severe thrombocytopenia which is evident within 24 hours of injection. While most studies have focused on immune platelet destruction in the spleen, an additional possibility is that the anti-platelet antibody also has an effect on megakaryocytes. To unequivocally determine if antiplatelet antibodies have an effect on megakaryocytes in an in vivo model, BALB/c mice were intravenously administered 2 ug of an anti-GPIIbIIIa antibody (MReg30) or 50 uL of a high tittered anti-GPIIIa (anti-β3) serum from BALB/c GPIIIa (CD61) knockout mice immunized with wild type platelets. Platelet counts were assessed over time and the bone marrow and spleens were harvested for histological examination of megakaryocytes. Both preparations of antiplatelet antibodies significantly reduced platelet numbers within 1 day of antibody or serum administration. This thrombocytopenia could be rescued by administration of 2 g/kg of IVIg ip. Compared with naïve control mice, histological (H&E staining) examination of the bone marrow and spleens revealed that megakaryocytes were significantly increased in number and all exhibited abnormalities consistent with apoptosis e.g. pyknotic nuclei. IVIg administration completely prevented these megakaryocyte abnormalities. These results show that passively administered anti-platelet antibodies not only affect platelet counts but also significantly affect megakaryocyte physiology in the absence of cell mediated immunity. Disclosures:No relevant conflicts of interest to declare.

Outer membrane protein-specific monoclonal antibodies protect SCID mice from fatal infection by the obligate intracellular bacterial pathogen Ehrlichia chaffeensis.

Previous studies of Ehrlichia chaffeensis infection in the mouse have demonstrated that passive transfer of polyclonal Abs from resistant immunocompetent mice to susceptible SCID mice ameliorated infection and disease, even when Abs were administered during established infection. To identify particular Abs that could mediate bacterial clearance in vivo, E. chaffeensis-specific mAbs were generated and administered to infected SCID mice. Bacterial infection in the livers was significantly lowered after administration of either of two Abs of different isotypes (IgG2a and IgG3). Moreover, repeated administration of one Ab (Ec56.5; IgG2a) rescued mice from an otherwise lethal infection for at least 5 wk. Both protective Abs recognized the E. chaffeensis major outer membrane protein (OMP)-1g. Further studies revealed that both Abs recognized closely related epitopes within the amino terminus of the first hypervariable region of OMP-1g. Analyses of human sera showed that E. chaffeensis-infected patients also generated serological responses to OMP-1g hypervariable region 1, indicating that humans and mice recognize identical or closely related epitopes. These studies demonstrate that OMP-specific mAbs can mediate bacterial elimination in SCID mice, and indicate that Abs, in the absence of cell-mediated immunity, can play a significant role in host defense during infection by this obligate intracellular bacterium.

The alloantibody response in the allogeneically pregnant rat. V. Absence of cell-mediated immunity in high responders

Allogeneically pregnant rats have been examined postpartum to determine whether they are sensitized against paternal class I antigens for cell-mediated immunity. This study was undertaken as this point is ambiguous. Since the response of the female to paternal MHC antigens is genetically controlled it is possible that the inability of some investigations to detect cell-mediated immunity against the paternal strain was due to the use of non-responder strain combinations. Cell-mediated immunity was assayed in a strain combination that is an unambiguous high responder, in which 100% of the females respond to the paternal strain by making alloantibodies. Maternal cell-mediated responses to paternal antigens were measured by the assays of DTH and IL-2 secretion under limiting conditions. We were unable to detect any cell-mediated immunity to paternal class I antigens even though the female produced copious quantities of alloantibody.