Summary
The uncommon C77G polymorphism of the Protein‐Tyrosine Phosphatase (PTPRC) gene (PTPRC; previously termed CD45) could confer an increased risk of immunopathology. This study compared the ...outcome of children following human leucocyte antigen‐matched unrelated haematopoïetic‐stem cell transplantations (HSCT) from donors carrying (C77G cases: n = 8) or not (controls: n = 36) the PTPRC C77G polymorphism. Transmission of the PTPRC C77G polymorphism through the graft was suggested by unusual CD45RA phenotype in the donors and/or in the recipients after, but not before HSCT. Restriction‐Fragment Length Polymorphism and sequencing confirmed the polymorphism. Overall survival rates were similar in C77G cases and controls (63% vs. 61%). Acute leukaemia relapse tended to be less frequent in C77G cases (0% vs. 32%; P = 0·09). Among recipients surviving ≥30 d, acute GVHD (aGVHD) ≥ grade 2 tended to be more frequent (100% vs. 58%; P = 0·07) and the rate of steroid‐refractory or –dependant aGVHD higher (67% vs. 28%) in C77G cases. Finally, extensive chronic GVHD tended to occur more frequently (40% vs. 9%) in C77G cases. Recovery of lymphocyte subsets and virus‐specific CD4 was similar in C77G cases and controls while interleukin 2 (IL2)‐responses through CD3 stimulation were higher in C77G cases (P = 0·004). In conclusion, HSCT from PTPRC C77G donors could increase GVHD risk without compromising overall survival. Altered IL2‐responses could be involved in this process.
Summary Objectives An increased rate of indeterminate quantiferon results (low IFN-γ release in the phytohemagglutinin-stimulated tube) has been reported in children with clinical signs compatible ...with tuberculosis but with the final diagnosis of infectious diseases different from tuberculosis. Here, we addressed the mechanisms involved and assessed potential alternative biomarkers to overcome indeterminate quantiferon results under these conditions. Methods Cytokine concentrations were measured in residual plasma from quantiferon assays performed in immunocompetent children (cases, median age: 3 years 9 months) with indeterminate results and community acquired pneumonia (n = 7) or meningoencephalitis (n = 1). Controls were age-matched immunocompetent children with determinate quantiferon results (infected with mycobacterium tuberculosis , n = 7 or not, n = 8). Results Lower IFN-γ expression in phytohemagglutinin-stimulated cultures from cases was accompanied by lower Th1 (IL-2, TNF-α, IP-10) and Th2 (IL-5, IL-13), but similar IL-10 secretion capacities as the controls. Conclusions A state of hyporesponsiveness that resembles the concept of immunoparalysis in severe infection was observed in children with milder infections. Though IP-10, IL-2, IL-5 and IL-13 were confirmed as promising alternative biomarkers for discriminating controls with and without tuberculosis in this study, defective induction of these biomarkers by phytohemagglutinin in cases precluded their usefulness in overcoming quantiferon indeterminate results in the above-mentioned clinical conditions.
Summary Objectives QuantiFERON value to diagnose tuberculosis (TB) in young children remains to be clarified. To this aim QF-TB-IT performance was evaluated in a large series of immunocompetent ...children that were stratified according to age and clinical conditions. Methods QF-TB-IT reactivity was analyzed in 226 immunocompetent children (0–15 years old): 31 were uninfected despite TB contact; 51 presented TB disease; 39 had Latent TB (LTBI) and 105 had TB disease suspected but an alternative diagnosis (TB excluded). Results QF-TB-IT specificity was 100% in TB excluded. In TB disease, low sensitivity of QF-TB-IT in infants (40%) increased with aging (77% in 1–<5 years and 82% in 5–<15 years old subgroups). In LTBI, agreement between TST and QF-TB-IT was 0% in infants, 40% in 1–<5 years and 57% in children >5 years old. Finally, the incidence of indeterminate results was high (24%) in children <5 years old with TB excluded, especially with non-TB pneumonitis (61%), but was low (0–6%) regardless of age group in TB disease, LTBI and uninfected contact cases. Conclusions In our low burden country, i) QF-TB-IT specificity was 100%, ii) QF-TB-IT sensitivity was low in infants but commensurable to adult values in older children, and iii) indeterminate results mostly relied on ongoing infections unrelated to TB.
Abstract 4214
Relapse of disease remains the most common cause of failure in children undergoing hematopoietic-stem cell transplantation (HSCT) for acute leukaemia. A favourable impact, on ...graft-versus leukaemia effect (GVL), from recipient CMV-seropositivity before HSCT and from CMV-reactivations in the recipient after HSCT has been suggested. The potential role, in this process, for the immune response triggered by CMV has not been directly addressed so far.
108 children (median age 8 years) were included at HSCT following myeloablative conditioning for primary acute leukaemia (lymphoblastic 54%, myeloblastic 42%, biphenotypic 4%). HSCT were from HLA-matched related (41%) or unrelated (44%) donors. 15% patients received cord blood units. CMV- DNAemia was programmed weekly for at least 3 months post-HSCT. When PCR showed ≥1000 copies/ml, patients received ganciclovir as pre-emptive therapy. Immunity to CMV was evaluated sequentially since the first month post-HSCT using 3H-Thymidine incorporation assay (T-cell proliferation) and intracytoplasmic cytokine accumulation assay (IFNg secretion).
Median follow-up from transplant was 40 months. 57% of patients were CMV-seropositive before HSCT. Cumulative incidence of recipients with CMV-DNAemia at day 120 was 31% (median time to onset: 26 days). Cumulative incidence of recipients with immunity to CMV (T-cell proliferation and/or IFNγ secretion assays) at 1 year was 38% (median time to onset: 2 months). As expected, recipient CMV seropositivity represented a major factor contributing to DNAemia (p<0.0001) and to immunity (p<0.001) occurrence as well. The 2 years cumulative incidence of relapse was 26% Among the 89 recipients free of relapse at day +120 and evaluated for immunity before that time, the 2 years cumulative incidence of relapse was 15%. Multivariable analysis revealed a different risk of leukemic relapse according to immunity to CMV and CMV-reactivation (p=0.039), with the lowest risk in recipients with early (before day 120) immunity to CMV but no CMV-reactivation and the highest risk in recipients with early (before day 120) CMV-reactivation but no immunity to CMV (HR: 0.06, 95%CI 0.01–0.69, p=0.024).
In conclusion, early development of immunity to CMV rather than early viremia had a favourable impact on GVL in this pediatric series.
No relevant conflicts of interest to declare.
During SARS-CoV-2 pandemic, the assessment of immune protection of people at risk of severe infection was an important goal. The appearance of VOCs (Variant of Concern) highlighted the limits of ...evaluating immune protection through the humoral response. While the humoral response partly loses its neutralizing activity, the anti-SARS-CoV-2 memory T cell response strongly cross protects against VOCs becoming an indispensable tool to assess immune protection. We compared two techniques available in laboratory to evaluate anti-SARS-CoV-2 memory T cell response in a cohort of infected or vaccinated patients with different levels of risk to develop a severe disease: the ELISpot assay and the T-Cell Lymphocyte Proliferation Assay respectively exploring IFNγ production and cell proliferation. We showed that the ELISpot assay detected more anti-Spike memory T cell response than the Lymphocyte Proliferation Assay. We next observed that the use of two different suppliers as antigenic source in the ELISpot assay did not affect the detection of anti-Spike memory T cell response. Finally, we explored a new approach for defining the positivity threshold, using unsupervised mixed Gaussian modeling, challenging the traditional ROC curve used by the supplier. That will be helpful in endemic situation where it could be difficult to recruit “negative” patients.
•Quantification of anti-SARS-CoV-2 memory T cell response using IFNγ-ELISpot assay was higher as compared to T-cell LPA.•The use of different peptide pools did not impact detection of anti-SARS-CoV-2 memory T cell response by IFNγ-ELISpot assay.•We used an innovative approach, the mixed Gaussian modeling, to define new thresholds of anti-Spike memory T cell response.
Abstract Immunity induced by influenza vaccines following hematopoietic stem-cell transplantation (HSCT) is poorly understood. Here, 14 pediatric recipients (mean age: 6 years) received H1N1 ( n = 9) ...or H1N1/H3N2 ( n = 5) vaccines at a median of 5.7 months post-HSCT (HLA-identical related bone-marrow graft: 10/14). Fourteen clinically-matched non-vaccinated recipients were included as controls. Cellular response to vaccination was assessed by a T-cell proliferation assay. Humoral response was assessed by H1N1-specific antibody titration. IL2 and IFNγ responses to influenza were also evaluated by an intracellular cytokine accumulation method for some of the recipients. Higher proliferative responses to H1N1 ( p = 0.0001) and higher H1N1-specific antibody titers ( p < 0.02) were observed in vaccines opposed to non-vaccinated recipients. In some cases, proliferative responses to H1N1 developed while at the same time antibody titers did not reach protective (⩾1:40) levels. Most recipients vaccinated with only the H1N1 strain had proliferative responses to both H1N1 and H3N2 (median stimulation index H1N1: 96, H3N2: 126 in responders). Finally, IL2 responses predominated over IFNγ responses ( p < 0.02) to influenza viruses in responders. In conclusion, H1N1 vaccination induced substantial cell-mediated immunity, and to a lesser extent, humoral immunity at early times post-HSCT. H1N1/H3N2 T-cell cross-reactivity and protective (IL2) rather than effector (IFNγ) cytokinic profiles were elicited.
The nature of adenovirus (AdV)-specific T cells that could best predict the capacity of immunocompromised host to fight AdV is unclear. To this aim, 47 pediatric patients were enrolled for at least 3 ...months either at allogeneic bone marrow transplantation (BMT) (23 genoidentical, 18 unrelated of which 9 were 10/10 and 9 were 9/10 HLA-matched) or at unrelated cord blood transplantation (n = 6). Enumeration of AdV-specific CD4 T cells secreting cytokines (flow cytometry) and proliferative responses to AdV (3 HT-incorporation) were compared to AdV-DNAemia. A total of 44/47 patients did not evidence AdV-DNAemia. Thirty-two of 44 (73%) developed CD4-mediated interferon-gamma (IFN-γ) responses to AdV (median 0.36 CD4/μL of blood) since the first month post-HSCT (n = 11: 8 genoidentical and 3 unrelated) or the third month (n = 21 additional patients). At 3 months, both incidence and level intensities of AdV-specific CD4 appeared similar in genoidentical and unrelated BMT (70% and 80%; 0.36 and 0.21 CD4/μL, respectively) and not statistically different from age-matched controls (76%; 1.35 CD4/μL), whereas cord blood transplanted patients exhibited similar incidence but higher level intensities (67%; 1.49 CD4/μL). Polyfunctional (IL2 + IFN-γ) and proliferative responses appeared later, after the third month. Three of 4 9/10 HLA-matched unrelated HSCT that did not develop immunity to AdV presented chemotherapy-resistant AdV-DNAemia at 3 to 5 months post-hematopoietic stem cell transplantation (HSCT). Two were successfully treated with AdV-specific CTL infusion. Monitoring, since month 1 post-HSCT, of IFN-γ-secreting AdV-specific CD4 appears suitable for early detection of at-risk patients especially in 9/10 HLA-matched unrelated HSCT and preferable to monitoring of more delayed IL2- and proliferative responses.
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