In vivo interferon-gamma induced changes in gene expression dramatically alter neutrophil phenotype

Enteral immunization with live bacteria reprograms innate immune cells and protects neonatal foals from pneumonia

Using a horse foal model, we show that enteral immunization of newborn foals with Rhodococcus equi overcomes neonatal vaccination challenges by reprogramming innate immune responses, inducing R. equi-specific adaptive humoral and cell-mediated immune responses and protecting foals against experimental pneumonia challenge. Foals were immunized twice via gavage of R. equi (immunized group) or saline (control group) at ages 1 and 3 days. At age 28 days, all foals were challenged intrabronchially with R. equi. Post-challenge, all 5 immunized foals remained healthy, whereas 67% (4/6) of control foals developed clinical pneumonia. Immunized foals exhibit changes in the epigenetic profile of blood monocytes, > 1,000 differentially-expressed genes in neutrophils, higher concentrations of R. equi-specific IgG1 and IgG4/7, and a higher number of IFN-γ producing lymphocytes in response to R. equi stimulation indicating T helper type 1 response compared to control foals. Together, our data indicate that early life exposure to R. equi in the gastrointestinal tract can modulate innate immune responses, generate specific antibodies and cell-mediated immunity, and protect against pneumonia.

Non-Infectious Complications of Chronic Granulomatous Disease: Knowledge Gaps & Novel Treatment Considerations

Chronic granulomatous disease (CGD) is a rare primary phagocytic immunodeficiency characterized by recurrent infections due to impaired NADPH oxidase activity. Balancing the need for additional immune suppression with the risk of infection in patients with CGD-associated inflammation can be difficult but increased understanding of the underlying pathophysiology may allow for more targeted and rational therapies. Current treatments for inflammatory complications include glucocorticoids, steroid-sparing immunosuppressive agents, antibiotics, and increasingly the use of targeted biologic agents. However, improved curative therapy strategies for patients with suboptimal donor options are needed and autologous gene therapy remains experimental.

Single-cell analysis of pig lung leukocytes and their response to influenza infection and oseltamivir therapy

Despite pigs being an important species in influenza A virus (IAV) epidemiology and a reliable preclinical model for human IAV infections, many aspects of the porcine pulmonary immune system remain poorly understood. Here, we characterized the single-cell landscape of lung leukocytes of healthy pigs and then compared them to pigs infected with 2009 pandemic H1N1 IAV with or without oseltamivir antiviral therapy. Our data show conserved features as well as species-specific differences in cell types and cell states compared with human and mouse lung lymphocytes. IAV infection induced a robust antiviral transcriptional response in multiple lymphoid and myeloid cell types, as well as distinct patterns of cell-cell crosstalk. Oseltamivir treatment substantially reduced these responses. Together, our findings describe key events in the pulmonary anti-IAV response of pigs that open new avenues to develop IAV vaccines and therapies. They should also enable the better use of pigs as a model for human IAV infection and immunity.

Neutrophils Display Novel Partners of Cytosolic Proliferating Cell Nuclear Antigen Involved in Interferon Response in COVID-19 Patients

INTRODUCTION

Neutrophils are key players in the hyperinflammatory response during SARS-CoV-2 infection. The cytosolic proliferating cell nuclear antigen (PCNA) is a scaffolding protein highly dependent on the microenvironment status and known to interact with numerous proteins that regulate neutrophil functions. This study aimed to examine the cytosolic protein content and PCNA interactome in neutrophils from COVID-19 patients.

METHODS

Proteomic analyses were performed on neutrophil cytosols from healthy donors and patients with severe or critical COVID-19. In vitro approaches were used to explore the biological significance of the COVID-19-specific PCNA interactome.

RESULTS

Neutrophil cytosol analysis revealed a strong interferon (IFN) protein signature, with variations according to disease severity. Interactome analysis identified associations of PCNA with proteins involved in interferon signaling, cytoskeletal organization, and neutrophil extracellular trap (NET) formation, such as protein arginine deiminase type-4 (PADI4) and histone H3, particularly in critical patients. Functional studies of interferon signaling showed that T2AA, a PCNA scaffold inhibitor, downregulated IFN-related genes, including STAT1, MX1, IFIT1, and IFIT2 in neutrophils. Additionally, T2AA specifically inhibited the secretion of CXCL10, an IFN-dependent cytokine. PCNA was also found to interact with key effector proteins implicated in NET formation, such as histone H3, especially in critical COVID-19 cases.

CONCLUSION

The analysis of the PCNA interactome has unveiled new protein partners that enhance the interferon pathway, thereby modulating immune responses and contributing to hyperinflammation in COVID-19. These findings provide valuable insights into interferon dysregulation in other immune-related conditions.

INTRODUCTION

Neutrophils are key players in the hyperinflammatory response during SARS-CoV-2 infection. The cytosolic proliferating cell nuclear antigen (PCNA) is a scaffolding protein highly dependent on the microenvironment status and known to interact with numerous proteins that regulate neutrophil functions. This study aimed to examine the cytosolic protein content and PCNA interactome in neutrophils from COVID-19 patients.

METHODS

Proteomic analyses were performed on neutrophil cytosols from healthy donors and patients with severe or critical COVID-19. In vitro approaches were used to explore the biological significance of the COVID-19-specific PCNA interactome.

RESULTS

Neutrophil cytosol analysis revealed a strong interferon (IFN) protein signature, with variations according to disease severity. Interactome analysis identified associations of PCNA with proteins involved in interferon signaling, cytoskeletal organization, and neutrophil extracellular trap (NET) formation, such as protein arginine deiminase type-4 (PADI4) and histone H3, particularly in critical patients. Functional studies of interferon signaling showed that T2AA, a PCNA scaffold inhibitor, downregulated IFN-related genes, including STAT1, MX1, IFIT1, and IFIT2 in neutrophils. Additionally, T2AA specifically inhibited the secretion of CXCL10, an IFN-dependent cytokine. PCNA was also found to interact with key effector proteins implicated in NET formation, such as histone H3, especially in critical COVID-19 cases.

CONCLUSION

The analysis of the PCNA interactome has unveiled new protein partners that enhance the interferon pathway, thereby modulating immune responses and contributing to hyperinflammation in COVID-19. These findings provide valuable insights into interferon dysregulation in other immune-related conditions.

Genotype-phenotype correlations in chronic granulomatous disease: insights from a large national cohort

ABSTRACT

Neutrophils are the first line of defense against invading pathogens. Neutrophils execute and modulate immune responses by generating reactive oxygen species (ROS). Chronic granulomatous disease (CGD) is a primary immune deficiency disorder of phagocytes, caused by inherited mutations in the genes of the nicotinamide adenine dinucleotide phosphate reduced oxidase enzyme. These mutations lead to failure of ROS generation followed by recurrent bacterial and fungal infections, frequently associated with hyperinflammatory manifestations. We report a multicenter cumulative experience in diagnosing and treating patients with CGD. From 1986 to 2021, 2918 patients experiencing frequent infections were referred for neutrophil evaluation. Among them, 110 patients were diagnosed with CGD: 56 of Jewish ancestry, 48 of Arabic ancestry, and 6 of non-Jewish/non-Arabic ancestry. As opposed to other Western countries, the autosomal recessive (AR) CGD subtypes were predominant in Israel (71/110 patients). Thirty-nine patients had X-linked CGD, in most patients associated with severe infections (clinical severity score ≥3) and poor outcomes, presenting at a significantly earlier age than AR-CGD subtypes. The full spectrum of infections and hyperinflammatory manifestations is described. Six patients had hypomorphic mutations with significantly milder phenotype, clinical severity score ≤2, and better outcomes. Hematopoietic stem cell transplantation was implemented in 39 of 110 patients (35.5%). Successful engraftment was achieved in 92%, with 82% long-term survival and 71% full clinical recovery. CGD is a complex disorder requiring a multiprofessional team. Early identification of the genetic mutation is essential for prompt diagnosis, suitable management, and prevention.

Evidence for antigen presentation by human neutrophils

ABSTRACT

Neutrophils are the first migrating responders to sterile and infectious inflammation and act in a powerful but nonspecific fashion to kill a wide variety of pathogens. It is now apparent that they can also act in a highly discriminating fashion; this is particularly evident in their interactions with other cells of the immune system. It is clear that neutrophils are present during the adaptive immune response, interacting with T cells in complex ways that differ between tissue types and disease state. One of the ways in which this interaction is mediated is by neutrophil expression of HLA molecules and presentation of antigen to T cells. In mice, this is well established to occur with both CD4+ and CD8+ T cells. However, the evidence is less strong with human cells. Here, we assembled available evidence for human neutrophil antigen presentation. We find that the human cells are clearly able to upregulate HLA-DR and costimulatory molecules; are able to process protein antigen into fragments recognized by T cells; are able to enter lymph node T cell zones; and, in vitro, are able to present antigen to memory T cells, inducing proliferation and cytokine production. However, many questions remain, particularly concerning whether the cell-cell interactions can last for sufficient time to trigger naïve T cells. These experiments are now critical as we unravel the complex interactions between these cells and their importance for the development of human immunity.

Interferon- and infectious diseases: Lessons and prospects

Infectious diseases continue to claim many lives. Prevention of morbidity and mortality from these diseases would benefit not just from new medicines and vaccines but also from a better understanding of what constitutes protective immunity. Among the major immune signals that mobilize host defense against infection is interferon-γ (IFN-γ), a protein secreted by lymphocytes. Forty years ago, IFN-γ was identified as a macrophage-activating factor, and, in recent years, there has been a resurgent interest in IFN-γ biology and its role in human defense. Here we assess the current understanding of IFN-γ, revisit its designation as an "interferon," and weigh its prospects as a therapeutic against globally pervasive microbial pathogens.

Exploring the Relationship between Neutrophil Activation and Different States of Canine L. infantum Infection: Nitroblue Tetrazolium Test and IFN-γ

This study aimed to investigate the role of neutrophils in canine leishmaniosis by assessing neutrophil activation and its relationship with different states of L. infantum infection and antibody and IFN-γ production. Dogs were categorized into five groups: healthy-seronegative (n = 25), healthy-seropositive (n = 21), LeishVet-stage I (n = 25), Leishvet-stage II (n = 41), and LeishVet-stage III-IV (n = 16). Results of the nitroblue tetrazolium reduction test (NBT) showed significantly higher neutrophil activation in stage I (median:17.17, range: [7.33-31.50]%) compared to in healthy-seronegative (4.10 [1.20-18.00]%), healthy-seropositive (7.65 [3.98-21.74]%), stage II (6.50 [1.50-28.70]%), and stage III-IV (7.50 [3.00-16.75]%) groups (p < 0.0001). Healthy-seropositive dogs also displayed higher values than all groups except stage I. Stages II and III-IV did not show significant differences compared to healthy-seronegative. Regarding IFN-γ, stage I dogs had higher concentrations (median:127.90, range: [0-3998.00] pg/mL) than healthy-seronegative (0 [0-109.50] pg/mL) (p = 0.0002), stage II (9.00 [0-5086.00] pg/mL) (p = 0.045), and stage III-IV (3.50 [80.00-548.80] pg/mL) (p = 0.02) dogs. Stage II dogs showed increased IFN-γ compared to healthy-seronegative dogs (p = 0.015), while stage III-IV dogs had no significant differences compared to healthy-seronegative dogs (p = 0.12). Healthy-seropositive dogs had elevated IFN-γ concentrations compared to healthy-seronegative dogs (p = 0.001) and dogs in stage III-IV (p = 0.03). In conclusion, neutrophil activation was higher in dogs with mild disease and healthy-seropositive dogs, and a relationship between neutrophil activation and the production of IFN-γ was found.

Neutrophil extracellular trap formation and gene programs distinguish TST/IGRA sensitization outcomes among Mycobacterium tuberculosis exposed persons living with HIV

Persons living with HIV (PLWH) have an increased risk for tuberculosis (TB). After prolonged and repeated exposure, some PLWH never develop TB and show no evidence of immune sensitization to Mycobacterium tuberculosis (Mtb) as defined by persistently negative tuberculin skin tests (TST) and interferon gamma release assays (IGRA). This group has been identified and defined as HIV+ persistently TB, tuberculin and IGRA negative (HITTIN). To investigate potential innate mechanisms unique to individuals with the HITTIN phenotype we compared their neutrophil Mtb infection response to that of PLWH, with no TB history, but who test persistently IGRA positive, and tuberculin positive (HIT). Neutrophil samples from 17 HITTIN (PMNHITTIN) and 11 HIT (PMNHIT) were isolated and infected with Mtb H37Rv for 1h and 6h. RNA was extracted and used for RNAseq analysis. Since there was no significant differential transcriptional response at 1h between infected PMNHITTIN and PMNHIT, we focused on the 6h timepoint. When compared to uninfected PMN, PMNHITTIN displayed 3106 significantly upregulated and 3548 significantly downregulated differentially expressed genes (DEGs) (absolute cutoff of a log2FC of 0.2, FDR < 0.05) whereas PMNHIT demonstrated 3816 significantly upregulated and 3794 significantly downregulated DEGs following 6h Mtb infection. Contrasting the log2FC 6h infection response to Mtb from PMNHITTIN against PMNHIT, 2285 genes showed significant differential response between the two groups. Overall PMNHITTIN had a lower fold change response to Mtb infection compared to PMNHIT. According to pathway enrichment, Apoptosis and NETosis were differentially regulated between HITTIN and HIT PMN responses after 6h Mtb infection. To corroborate the blunted NETosis transcriptional response measured among HITTIN, fluorescence microscopy revealed relatively lower neutrophil extracellular trap formation and cell loss in PMNHITTIN compared to PMNHIT, showing that PMNHITTIN have a distinct response to Mtb.

Efficacy and Safety of Interferon-Gamma in Chronic Granulomatous Disease: a Systematic Review and Meta-analysis

BACKGROUND

Chronic granulomatous disease (CGD) is a primary immunodeficiency with increased susceptibility to several bacteria, fungi, and mycobacteria, caused by defective or null superoxide production by the NADPH oxidase enzymatic complex. Accepted treatment consists mainly of antimicrobial prophylaxis. The role of human recombinant subcutaneous interferon-gamma (IFNγ) is less clear since the available evidence on its efficacy derives mainly from a single clinical trial that has been challenged.

OBJECTIVE

We aimed to assess the efficacy and safety of IFNγ as an added treatment for CGD when compared to antimicrobial prophylaxis alone.

METHODS

A literature search was conducted using MeSH terms "Chronic granulomatous disease" AND ("interferon gamma" OR "interferon-gamma"), as well as antibiotics, placebo, no therapy, clinical trial, and trial, on MEDLINE, EMBASE, LILACS, WHOs, CENTRAL, KOREAMED, The Cochrane Library, clinicaltrials.gov, and abstracts from meetings, from 1976 to July 2022. We included clinical trials (CT) and prospective follow-up studies and registered the number of serious infections (requiring hospitalization and IV antibiotics) and deaths, adverse events, and autoimmune complications, in patients treated for CGD with antimicrobial prophylaxis plus IFN-γ, versus antimicrobial prophylaxis alone. We assessed the quality of the studies using risk of bias and STROBE. We performed a meta-analysis by calculating both Peto's odds ratio (OR) and risk reduction (RR) through the Mantel-Haenszel method with a fixed-effect model, using Review Manager 5.4, and we reported the number needed to treat (NNT).

RESULTS

We identified 54 matches from databases and 4 from other sources. We excluded 12 duplicates, 7 titles, and 9 abstracts for relevance, after which we had 30 eligible studies. Twenty-four were then excluded after reading the full text. Six papers were included: one randomized CT and 5 follow-up studies. In total, 324 patients with Chronic granulomatous disease were followed for 319 months under treatment with antibiotic prophylaxis plus interferon-gamma or placebo (or antibiotic prophylaxis alone), reported between the years 1991 and 2016. Three of the studies included a control group, allowing for the aggregate analysis of efficacy (prevention of serious infections). The aggregate OR was 0.49, with a 95% confidence interval of 0.19 to 1.23. The risk ratio for serious infection was 0.56 (95%CI 0.35-0.90) under IFN-γ. The meta-analysis thus favors interferon-gamma for a risk reduction of serious infection.

DISCUSSION

The results from this meta-analysis support the use of IFN-γ in the treatment of patients with CGD. However, we found insufficient clinical evidence and believe more clinical trials are needed to better assess the efficacy and long-term safety of IFN-γ.

Utility of monocyte HLA-DR and rationale for therapeutic GM-CSF in sepsis immunoparalysis

Sepsis, a heterogeneous clinical syndrome, features a systemic inflammatory response to tissue injury or infection, followed by a state of reduced immune responsiveness. Measurable alterations occur in both the innate and adaptive immune systems. Immunoparalysis, an immunosuppressed state, associates with worsened outcomes, including multiple organ dysfunction syndrome, secondary infections, and increased mortality. Multiple immune markers to identify sepsis immunoparalysis have been proposed, and some might offer clinical utility. Sepsis immunoparalysis is characterized by reduced lymphocyte numbers and downregulation of class II human leukocyte antigens (HLA) on innate immune monocytes. Class II HLA proteins present peptide antigens for recognition by and activation of antigen-specific T lymphocytes. One monocyte class II protein, mHLA-DR, can be measured by flow cytometry. Downregulated mHLA-DR indicates reduced monocyte responsiveness, as measured by ex-vivo cytokine production in response to endotoxin stimulation. Our literature survey reveals low mHLA-DR expression on peripheral blood monocytes correlates with increased risks for infection and death. For mHLA-DR, 15,000 antibodies/cell appears clinically acceptable as the lower limit of immunocompetence. Values less than 15,000 antibodies/cell are correlated with sepsis severity; and values at or less than 8000 antibodies/cell are identified as severe immunoparalysis. Several experimental immunotherapies have been evaluated for reversal of sepsis immunoparalysis. In particular, sargramostim, a recombinant human granulocyte-macrophage colony-stimulating factor (rhu GM-CSF), has demonstrated clinical benefit by reducing hospitalization duration and lowering secondary infection risk. Lowered infection risk correlates with increased mHLA-DR expression on peripheral blood monocytes in these patients. Although mHLA-DR has shown promising utility for identifying sepsis immunoparalysis, absence of a standardized, analytically validated method has thus far prevented widespread adoption. A clinically useful approach for patient inclusion and identification of clinically correlated output parameters could address the persistent high unmet medical need for effective targeted therapies in sepsis.