CD4 T-cell function assay using Cylex ImmuKnow and lymphocyte subset recovery following allogeneic hematopoietic stem cell transplantation

Assessment of cellular response to mitogens in long-term allogeneic hematopoietic stem cell transplantation survivors

Infection is one of the major causes of death in hematopoietic stem cell transplantation (HSCT) survivors. Precise assessments of immune function after HSCT will be critical in establishing appropriate treatment and prophylaxis, such as re-vaccination. Although several surrogate markers for prediction of clinical outcomes after HSCT have been proposed, definitive markers of immune reconstitution and data on those markers in long-term survivors are lacking. In this study, cellular response to mitogens was assessed and clinical features associated with a poor response to mitogens were investigated in long-term allogeneic HSCT survivors. Age at transplantation and age at the time of mitogen stimulation test were each identified as significant risk factors for poor response to phytohemagglutinin and concanavalin A, respectively (P < 0.001 each). However, time elapsed since transplantation was not found to be correlated with responsiveness to mitogens in this study. Prospective, in-depth studies on immune reconstitution are needed to establish appropriate prophylaxis against infections after HSCT and a schedule for re-vaccination.

Functional immune reconstitution early after allogeneic haematopoietic cell transplantation: A comparison of pre- and post-transplantation cytokine responses in stimulated whole blood

We aimed to use a novel standardized whole-blood stimulation system to evaluate differences in the functional immune reconstitution in patients early after allogeneic haematopoietic cell transplantation (HCT). Between April and September 2018, 30 patients undergoing HCT had whole blood samples collected around day -21 (day 0 being the day of haematopoietic cell infusion) and day +28. Whole blood was transferred to TruCulture assays comprising prefilled incubation tubes with cell culture medium and a standardized stimulus. We used a panel of four stimuli (lipopolysaccharide, resiquimod, heat-killed Candida albicans and polyinosinic:polycytidylic acid) and a blank, designed to evaluate the function of critical extra- and intracellular immunological signalling pathways. For each stimulus, the cytokine response was assessed by the concentration of interferon-γ, interleukin (IL)-12p40, IL-10, IL-1β, IL-6, IL-8, IL-10, IL-12p40, IL-17A and tumour necrosis factor-α using a multiplex Luminex assay. Pre-HCT cytokine responses were globally decreased across several different stimuli. Despite patients receiving immunosuppressive prophylaxis at the time, post-HCT cytokine responses were higher and less intercorrelated than pre-HCT responses, also after adjusting for differences in the leukocyte differential counts. For the resiquimod and heat-killed Candida albicans stimuli, we identified a cluster of patients in whom post-HCT responses were lower than average across several cytokines, indicating a possible functional immune deficiency. Our findings suggest that the standardized whole blood stimulation system can be used to reveal heterogeneity in the in vitro cytokine responses to various stimuli after HCT. Larger studies are needed to address if the functional immune reconstitution after HCT can predict the risk of infections.

Immune cell function assays in the diagnosis of infection in pediatric liver transplantation: an open-labeled, two center prospective cohort study

BACKGROUND

Limited studies have been performed in assessment of immune status of pediatric liver transplants (PLTs). We conducted this study to evaluate Cylex immune cell function assay in diagnosis of infection and its potential clinical application in Chinese infant PLTs.

METHODS

In this prospective cohort study, 227 infant PLTs from two medical centers were enrolled, and 216 completed the study. Cylex ATP values were measured before and after liver transplantation (LT) at week 1, 2, 3, 4, 8, 12 and 24 respectively. Accordingly, patients' clinical records, including demographic data, liver function results, tacrolimus dosages and concentrations were collected and analyzed.

RESULTS

One hundred and sixty of 216 PLTs (74.1%) were diagnosed infection based on the parameters including abnormal vital signs, imaging changes, and pathogens detection, while 44 (20.4%) were clinically stable and 12 (5.6%) experienced acute rejection. The median Cylex ATP value in infant PLTs post-surgery reduced significantly in infection group compared to stable group (median, 137 vs. 269 ng/mL, P<0.001). Receiver operating characteristic (ROC) curve analysis determined that the cut-off value of Cylex ATP was 152 ng/mL in diagnosis of infection [area under the curve (AUC): 0.784, 95% CI: 0.720-0.848]. Meanwhile, Cylex ATP value showed no correlation to tacrolimus dosage, blood concentration, dose-normalized concentration/dose ratio or Kaup index. However, it tended to correlate weakly with the white blood cell (WBC) number (R =0.462, P<0.0001) and lymphocyte counts (R =0.363, P<0.0001).

CONCLUSIONS

In this study, we demonstrated that low Cylex ATP represented partly over-immunosuppression and had diagnostic value in infant PLTs with infections, which might assist individualized immunosuppression in PLT patients.

Low T-Cell Responses to Mitogen Stimulation Predicts Poor Survival in Recipients of Allogeneic Hematopoietic Stem Cell Transplantation

Background

Successful engraftment and reconstitution of the innate and adaptive immune system are associated with improved outcomes in recipients of allogeneic hematopoietic stem cell transplantation (HSCT). A clinically meaningful and simple biomarker of immunosuppression could potentially assist clinicians in their decision-making. We aimed to determine the relationship between T-cell production of interferon gamma (IFN-γ) in response to phytohemagglutinin (PHA) to clinical outcomes in HSCT recipients.

Methods

A prospective observational multicenter study of 73 adult allogeneic HSCT recipients was conducted in Melbourne, Australia. Eligible participants were >18 years and at risk of cytomegalovirus disease. T-cell responses to PHA were assessed at 3, 6, 9, and 12 months post-HSCT using the commercial quantiferon-cytomegalovirus assay, which quantifies IFN-γ production by ELISA following stimulation with PHA. A low response was defined as IFN-γ <0.5 IU/ml following stimulation with PHA.

Results

At 3 months post-HSCT, high responses to PHA (median IFN-γ 7.68 IU/ml) were seen in 63% of participants and low responses to PHA (median IFN-γ 0.06 IU/ml) in 37%. IFN-γ responses to PHA were significantly associated with the severity of acute graft versus host disease (AGVHD) (spearman r = −0.53, p < 0.001) and correlated with blood lymphocyte count (spearman r = 0.52, p < 0.001). Twelve month overall survival was greater in individuals with high compared to low IFN-γ response to PHA at 3 months [92 vs. 62%, respectively, Cox proportional hazard ratio (HR): 4.12 95% CI: 1.2–13.7, p = 0.02]. Non-relapse mortality (NRM) was higher in individuals with low IFN-γ response to PHA (competing risk regression HR 11.6 p = 0.02). In individuals with no AGVHD compared to AGVHD and high IFN-γ response to PHA compared to AGVHD and low IFN-γ response to PHA, 12-month survival was 100 vs. 80 vs. 52%, respectively (log rank test p < 0.0001).

Conclusion

Low IFN-γ response to PHA at the 3-month time-point following allogeneic HSCT was predictive of reduced 12-month overall survival, increased NRM, and reduced survival in recipients with AGVHD. Assessing IFN-γ response to PHA post-HSCT may be a clinically useful immune biomarker.

Dynamics of Torque Teno virus plasma DNAemia in allogeneic stem cell transplant recipients

BACKGROUND

Torque Teno virus (TTV) plasma DNA load directly correlate with the level of immunosuppresion in different clinical settings. It is uncertain whether this may be the case in allogeneic hematopoietic stem cell transplant recipients (allo-HSCT).

OBJECTIVES

We characterized the dynamics of TTV DNAemia in patients undergoing T-cell replete allo-SCT.

STUDY DESIGN

Retrospective single-center observational study including 72 allo-HSCT patients. Plasma TTV DNA loads were quantified before initiating the conditioning regimen and at different time-points after transplant by real-time PCR. White blood cells (WBC) and absolute lymphocyte counts (ALC) were measured by flow cytometry.

RESULTS

A dramatic drop in plasma TTV DNA load was observed shortly after conditioning. The TTV DNA load increased steadily after engraftment reaching its peak at day +90 after transplant. The increase in TTV DNA load paralleled that of ALC, and was of greater magnitude in patients who developed severe (grades II-IV) acute graft vs. host disease.

CONCLUSION

Repopulation of lymphocytes early after allo-HSCT correlates with an increase of plasma TTV DNA load. Prospective studies are nevertheless needed to determine whether the kinetics of TTV DNAemia may allow inference of the degree of overall immunocompetence in these patients.