Chenli Qiu

Recovery from severe H7N9 disease is associated with diverse response mechanisms dominated by CD8+ T cells

The avian origin A/H7N9 influenza virus causes high admission rates (>99%) and mortality (>30%), with ultimately favourable outcomes ranging from rapid recovery to prolonged hospitalization. Using a multicolour assay for monitoring adaptive and innate immunity, here we dissect the kinetic emergence of different effector mechanisms across the spectrum of H7N9 disease and recovery. We find that a diversity of response mechanisms contribute to resolution and survival. Patients discharged within 2–3 weeks have early prominent H7N9-specific CD8+ T-cell responses, while individuals with prolonged hospital stays have late recruitment of CD8+/CD4+ T cells and antibodies simultaneously (recovery by week 4), augmented even later by prominent NK cell responses (recovery >30 days). In contrast, those who succumbed have minimal influenza-specific immunity and little evidence of T-cell activation. Our study illustrates the importance of robust CD8+ T-cell memory for protection against severe influenza disease caused by newly emerging influenza A viruses.

The Upregulation of LAG-3 on T Cells Defines a Subpopulation with Functional Exhaustion and Correlates with Disease Progression in HIV-Infected Subjects

T cells develop functional defects during HIV-1 infection, partially due to the upregulation of inhibitory receptors such as programmed death-1 (PD-1) and CTLA-4. However, the role of lymphocyte activation gene-3 (LAG-3; CD223), also known as an inhibitory receptor, in HIV infection remains to be determined. In this study, we revealed that LAG-3 on T cells delivers an inhibitory signal to downregulate T cell functionality, thereby playing an immunoregulatory role during persistent HIV-1 infection. We observed that HIV-1 infection results in a significant increase in LAG-3 expression in both the peripheral blood and the lymph nodes. The upregulation of LAG-3 is dramatically manifested on both CD4+ and CD8+ T cells and is correlated with disease progression. As expected, prolonged antiretroviral therapy reduces the expression of LAG-3 on both CD4+ and CD8+ T cells. The ex vivo blockade of LAG-3 significantly augments HIV-specific CD4+ and CD8+ T cell responses, whereas the overexpression of LAG-3 in T cells or the stimulation of LAG-3 on T cells leads to the reduction of T cell responses. Furthermore, most LAG-3 and PD-1 are expressed in different T cell subsets. Taken together, these data demonstrate that the LAG-3/MHC class II pathway plays an immunoregulatory role, thereby providing an important target for enhancing immune reconstitution in HIV-infected patients. Additionally, the LAG-3/MHC class II pathway may synergize with PD-1/PD ligand to enhance T cell–mediated immune responses.

Anti-IL-23 antibody blockade of IL-23/IL-17 pathway attenuates airway obliteration in rat orthotopic tracheal transplantation

Obliterative bronchiolitis (OB) has been a major obstacle to long-term allograft survival after lung transplantation, and the underlying mechanism is not well understood. As IL-23/IL-17 pathway has been shown to play important roles in airway inflammation, in this study we have investigated the role of IL-23/IL-17 pathway in acute and chronic airway allograft rejection. We used a rat OB model in orthotopic tracheal transplantation, and investigated the effects of anti-IL-23 blockade antibody on acute and chronic airway allograft rejection. Anti-IL-23 antibody impaired the function of IL-23 in inducing IL-17 production. The rats that received allografts and treated with anti-IL-23 antibody showed significantly less symptom of airway obliteration and chronic transplant rejection compared with control rats which received physiological saline or IgG antibody. Taken together, our results suggest that anti-IL-23 antibody is effective in protecting allograft rejection and the development of chronic OB in allo-tracheal transplantation. These findings may have implications for new therapies to prevent OB and allograft rejection in human lung transplantation.

Early Adaptive Humoral Immune Responses and Virus Clearance in Humans Recently Infected with Pandemic 2009 H1N1 Influenza Virus

Few studies on the humoral immune responses in human during natural influenza infection have been reported. Here, we used serum samples from pandemic 2009 H1N1 influenza infected patients to characterize the humoral immune responses to influenza during natural infection in humans. We observed for the first time that the pandemic 2009 H1N1 influenza induced influenza A-specific IgM within days after symptoms onset, whereas the unit of IgG did not changed. The magnitude of influenza A-specific IgM antibodies might have a value in predicting the rate of virus clearance to some degree. However, the newly developed IgM was not associated with hemagglutination inhibition (HI) activities in the same samples but correlated with HI activities of subsequently collected sera which were mediated by IgG antibodies, indicating that IgM was critical for influenza infection and influences subsequent IgG antibody responses. These findings provide new important insights on the human immunity to natural influenza infection.

Boosting Functional Avidity of CD8+ T Cells by Vaccinia Virus Vaccination Depends on Intrinsic T-Cell MyD88 Expression but Not the Inflammatory Milieu

ABSTRACT T-cell functional avidity is a crucial determinant for efficient pathogen clearance. Although recombinant DNA priming coupled with a vaccinia-vectored vaccine (VACV) boost has been widely used to mount robust CD8+ T-cell responses, how VACV boost shapes the properties of memory CD8+ T cells remains poorly defined. Here, we characterize the memory CD8+ T cells boosted by VACV and demonstrate that the intrinsic expression of MyD88 is critical for their high functional avidity. Independent of selection of clones with high-affinity T-cell receptor (TCR) or of enhanced proximal TCR signaling, the VACV boost significantly increased T-cell functional avidity through a decrease in the activation threshold. VACV-induced inflammatory milieu is not sufficient for this improvement, as simultaneous administration of the DNA vaccine and mock VACV had no effects on the functional avidity of memory CD8+ T cells. Furthermore, reciprocal adoptive transfer models revealed that the intrinsic MyD88 pathway is required for instructing the functional avidity of CD8+ T cells boosted by VACV. Taking these results together, the intrinsic MyD88 pathway is required for the high functional avidity of VACV-boosted CD8+ T cells independent of TCR selection or the VACV infection-induced MyD88-mediated inflammatory milieu. IMPORTANCE Functional avidity is one of the crucial determinants of T-cell functionality. Interestingly, although it has been demonstrated that a DNA prime-VACV boost regimen elicits high levels of T-cell functional avidity, how VACV changes the low avidity of CD8+ T cells primed by DNA into higher ones in vivo is less defined. Here, we proved that the enhancement of CD8+ T cell avidity induced by VACV boost is mediated by the intrinsic MyD88 pathway but not the MyD88-mediated inflammatory milieu, which might provide prompts in vaccine design.

Epidemiologic report and serologic findings for household contacts of three cases of influenza A (H7N9) virus infection

Abstract Background and objective We conducted epidemiologic investigations and serologic assays on household contacts that were extensively exposed to three influenza A (H7N9) virus infected case-patients before infection-control practices were implemented. Study design Data on the early clinical course of each patient and the exposure history for each patients household contacts were obtained by interviewing household members and by reviewing medical records. Viral RNA in patient samples was tested using real-time reverse transcriptase polymerase chain reaction assay. Antibodies against H7N9 virus in serum samples were tested using hemagglutination inhibition and pseudovirus based neutralization assays. Results All household contacts were extensively exposed to the case-patients without the use of measures to protect against infection. Viral RNA was detected in the specimens from case-patients for approximately 7–11 days after confirmation of infection. However, the results of the analyses of serum specimens taken from the household contacts 15–26 days post exposure revealed no evidence of transmission of H7N9 virus from the case-patients to the contacts. Conclusion Despite ample unprotected exposures to case-patients during the virus shedding period, household members in this report were not infected by the H7N9 virus.

Clonally diverse CD38 + HLA-DR + CD8 + T cells persist during fatal H7N9 disease

Severe influenza A virus (IAV) infection is associated with immune dysfunction. Here, we show circulating CD8+ T-cell profiles from patients hospitalized with avian H7N9, seasonal IAV, and influenza vaccinees. Patient survival reflects an early, transient prevalence of highly activated CD38+HLA-DR+PD-1+ CD8+ T cells, whereas the prolonged persistence of this set is found in ultimately fatal cases. Single-cell T cell receptor (TCR)-αβ analyses of activated CD38+HLA-DR+CD8+ T cells show similar TCRαβ diversity but differential clonal expansion kinetics in surviving and fatal H7N9 patients. Delayed clonal expansion associated with an early dichotomy at a transcriptome level (as detected by single-cell RNAseq) is found in CD38+HLA-DR+CD8+ T cells from patients who succumbed to the disease, suggesting a divergent differentiation pathway of CD38+HLA-DR+CD8+ T cells from the outset during fatal disease. Our study proposes that effective expansion of cross-reactive influenza-specific TCRαβ clonotypes with appropriate transcriptome signatures is needed for early protection against severe influenza disease.Virus-specific CD8+ T cells are crucial during H7N9 influenza infection, but CD8+ T cell dysfunction is associated with poor prognosis. Here, the authors use molecular and phenotypic analysis to establish persistence of clonally diverse CD8+ T cell populations during fatal infection.

Immune Signature of Enhanced Functional Avidity CD8 + T Cells in vivo Induced by Vaccinia Vectored Vaccine

Functional avidity of T cells is a critical determinant for clearing viral infection and eliminating tumor. Understanding how functional avidity is maintained in T cells is imperative for immunotherapy. However, studies systematically characterize T cell with high functional avidity induced in vivo are still lacking. Previously, we and others found vaccinia vectored vaccine (VACV) induced antigen-specific CD8+ T cells with relatively high functional avidity to those from DNA vaccine. Herein, we used functional, immune phenotyping and transcriptomic studies to define the immune signature of these CD8+ T cells with high functional avidity. Antigen-specific CD8+ T cells induced by VACV executed superior in vivo killing activity and displayed a distinct transcriptional profile, whereas no significantly differences were found in composition of memory sub-populations and cytokine poly-functionality. Transcriptional analyses revealed unique features of VACV induced CD8+ T cells in several biological processes, including transport, cell cycle, cell communication and metabolic processes. In summary, we characterize CD8+ T cells of high functional avidity induced in vivo by VACV, which not only improves our understanding of adaptive T cell immunity in VACV vaccination, but also provides clues to modulate functional avidity of CD8+ T cells for T cell based immunotherapy.

Development of Skewed Functionality of HIV-1-Specific Cytotoxic CD8+ T Cells from Primary to Early Chronic Phase of HIV Infection

In recent years, the prevalence of HIV-1 infection has been rapidly increasing among men who have sex with men (MSM). However, it remains unknown how the host immune system responds to the infection in this population. We assessed the quantity of HIV-specific CD8+ T-cell responses by using Elispot assay and their functionalities by measuring 5 CD8+ T-cell evaluations (IL-2, MIP-1β, CD107a, TNF-α, IFN-γ) with flow cytometry assays among 18 primarily and 37 early chronically HIV-infected MSM. Our results demonstrated that subjects at early chronic phase developed HIV-specific CD8+ T-cell responses with higher magnitudes and more diversified functionalities in comparison with those at primary infection. However, populations with IL-2+ CD107a+ or in combination with other functionality failed to develop in parallel. The multifunctional but not monofunctional HIV-specific CD8+ T cells were associated with higher CD4+ T -cell counts and lower viral loads. These data revealed that prolonged infection from primary to early chronic infection could selectively increase the functionalities of HIV-specific CD8+ T cells in HIV-infected MSM population, the failure to develop IL-2 and cytotoxic functionalities in parallel may explain why the increased HIV-specific CD8+ T cells were unable to enhance the containment of HIV-1 replication at the early chronic stage.

Immune Activation Influences SAMHD1 Expression and Vpx-mediated SAMHD1 Degradation during Chronic HIV-1 Infection

SAMHD1 restricts human immunodeficiency virus type 1 (HIV-1) replication in myeloid cells and CD4+ T cells, while Vpx can mediate SAMHD1 degradation to promote HIV-1 replication. Although the restriction mechanisms of SAMHD1 have been well-described, SAMHD1 expression and Vpx-mediated SAMHD1 degradation during chronic HIV-1 infection were poorly understood. Flow cytometric analysis was used to directly visualize ex vivo, and after in vitro SIV-Vpx treatment, SAMHD1 expression in CD4+ T cells and monocytes. Here we report activated CD4+ T cells without SAMHD1 expression were severely reduced, and SAMHD1 in CD4+ T cells became susceptible to SIV-Vpx mediated degradation during chronic HIV-1 infection, which was absent from uninfected donors. These alterations were irreversible, even after long-term fully suppressive antiretroviral treatment. Although SAMHD1 expression in CD4+ T cells and monocytes was not found to correlate with plasma viral load, Vpx-mediated SAMHD1 degradation was associated with indicators of immune activation. In vitro assays further revealed that T-cell activation and an upregulated IFN-I pathway contributed to these altered SAMHD1 properties. These findings provide insight into how immune activation during HIV-1 infection leads to irreparable aberrations in restriction factors and in subsequent viral evasion from host antiviral defenses.