Late-Onset Disseminated Mycobacterium avium intracellulare Complex Infection (MAC), Cerebral Toxoplasmosis and Salmonella Sepsis in a German Caucasian Patient with Unusual Anti-Interferon-Gamma IgG1 Autoantibodies

Anti-cytokine autoantibodies: mechanistic insights and disease associations

Anti-cytokine autoantibodies (ACAAs) are increasingly recognized as modulating disease severity in infection, inflammation and autoimmunity. By reducing or augmenting cytokine signalling pathways or by altering the half-life of cytokines in the circulation, ACAAs can be either pathogenic or disease ameliorating. The origins of ACAAs remain unclear. Here, we focus on the most common ACAAs in the context of disease groups with similar characteristics. We review the emerging genetic and environmental factors that are thought to drive their production. We also describe how the profiling of ACAAs should be considered for the early diagnosis, active monitoring, treatment or sub-phenotyping of diseases. Finally, we discuss how understanding the biology of naturally occurring ACAAs can guide therapeutic strategies.

Anticytokine Autoantibodies in Infectious Diseases: A Practical Overview

Anticytokine autoantibodies (ACAAs) are a fascinating group of antibodies that have gained more and more attention in the field of autoimmunity and secondary immunodeficiencies over the years. Some of these antibodies are characterized by their ability to target and neutralize specific cytokines. ACAAs can play a role in the susceptibility to several infectious diseases, and their infectious manifestations depending on which specific immunological pathway is affected. In this review, we will give an outline per infection in which ACAAs might play a role and whether additional immunomodulatory treatment next to antimicrobial treatment can be considered. Finally, we describe the areas for future research on ACAAs.

Characteristics and Outcomes of Anti-interferon Gamma Antibody-Associated Adult Onset Immunodeficiency

PURPOSE

Anti-interferon gamma antibody (AIGA) is a rare cause of adult onset immunodeficiency, leading to severe disseminated opportunistic infections with varying outcomes. We aimed to summarize the disease characteristics and to explore factors associated with disease outcome.

METHODS

A systematic literature review of AIGA associated disease was conducted. Serum-positive cases with detailed clinical presentations, treatment protocols, and outcomes were included. The patients were categorized into controlled and uncontrolled groups based on their documented clinical outcome. Factors associated with disease outcome were analyzed with logistic regression models.

RESULTS

A total of 195 AIGA patients were retrospectively analyzed, with 119(61.0%) having controlled disease and 76 (39.0%) having uncontrolled disease. The median time to diagnosis and disease course were 12 months and 28 months, respectively. A total of 358 pathogens have been reported with nontubercular mycobacterium (NTM) and Talaromyces marneffei as the most common pathogens. The recurrence rate was as high as 56.0%. The effective rates of antibiotics alone, antibiotics with rituximab, and antibiotics with cyclophosphamide were 40.5%, 73.5%, and 75%, respectively. In the multivariate logistic analysis, skin involvement, NTM infection, and recurrent infections remained significantly associated with disease control, with ORs of 3.25 (95% CI 1.187 ~ 8.909, P value = 0.022), 4.74 (95% CI 1.300 ~ 17.30, P value = 0.018), and 0.22 (95% CI 0.086 ~ 0.551, P value = 0.001), respectively. The patients with disease control had significant AIGA titer reduction.

CONCLUSIONS

AIGA could cause severe opportunistic infections with unsatisfactory control, particularly in patients with recurrent infections. Efforts should be made to closely monitor the disease and regulate the immune system.

The detectable anti-interferon-γ autoantibodies in COVID-19 patients may be associated with disease severity

BACKGROUND

Neutralizing anti-interferon (IFN)-γ autoantibodies are linked to adult-onset immunodeficiency and opportunistic infections.

METHODS

To explore whether anti-IFN-γ autoantibodies are associated with disease severity of coronavirus disease 2019 (COVID-19), we examined the titers and functional neutralization of anti-IFN-γ autoantibodies in COVID-19 patients. In 127 COVID-19 patients and 22 healthy controls, serum titers of anti-IFN-γ autoantibodies were quantified using enzyme-linked immunosorbent assay, and the presence of autoantibodies was verified with immunoblotting assay. The neutralizing capacity against IFN-γ was evaluated with flow cytometry analysis and immunoblotting, and serum cytokines levels were determined using the MULTIPLEX platform.

RESULTS

A higher proportion of severe/critical COVID-19 patients had positivity for anti-IFN-γ autoantibodies (18.0%) compared with non-severe patients (3.4%, p < 0.01) or healthy control (HC) (0.0%, p < 0.05). Severe/critical COVID-19 patients also had higher median titers of anti-IFN-γ autoantibodies (5.01) compared with non-severe patients (1.33) or HC (0.44). The immunoblotting assay could verify the detectable anti-IFN-γ autoantibodies and revealed more effective inhibition of signal transducer and activator of transcription (STAT1) phosphorylation on THP-1 cells treated with serum samples from anti-IFN-γ autoantibodies-positive patients compared with those from HC (2.21 ± 0.33 versus 4.47 ± 1.64, p < 0.05). In flow-cytometry analysis, sera from autoantibodies-positive patients could also significantly more effectively suppress the STAT1 phosphorylation (median,67.28%, interquartile range [IQR] 55.2-78.0%) compared with serum from HC (median,106.7%, IQR 100.0-117.8%, p < 0.05) or autoantibodies-negative patients (median,105.9%, IQR 85.5-116.3%, p < 0.05). Multivariate analysis revealed that the positivity and titers of anti-IFN-γ autoantibodies were significant predictors of severe/critical COVID-19. Compared with non-severe COVID-19 patients, we reveal that a significantly higher proportion of severe/critical COVID-19 patients are positive for anti-IFN-γ autoantibodies with neutralizing capacity.

CONCLUSION

Our results would add COVID-19 to the list of diseases with the presence of neutralizing anti-IFN-γ autoAbs. Anti-IFN-γ autoantibodies positivity is a potential predictor of severe/critical COVID-19.

High-titer anti-interferon-γ neutralizing autoantibodies linked to opportunistic infections in patients with adult-onset still's disease

Objective

Neutralizing anti-interferon (IFN)-γ autoantibodies are linked to opportunistic infections (OIs). To explore the association between anti-IFN-γ autoantibodies and OIs in patients with adult-onset Still's disease (AOSD), we aimed to examine the ability of these autoantibodies to blockade signal transducer and activator of transcription (STAT1)-phosphorylation and chemokines production.

Methods

Serum titers of anti-IFN-γ autoantibodies were quantified using ELISA in 29 AOSD and 22 healthy controls (HC). The detectable autoantibodies were verified with immunoblotting assay, and their neutralizing capacity against IFN-γ-signaling was evaluated with flow-cytometry analysis and immunoblotting. IFN-γ-mediated production of supernatant chemokines, including monocyte chemoattractant protein-1 (MCP-1) and IFN-γ inducible protein-10 (IP-10), were measured by ELISA.

Results

Among 29 AOSD patients, high titers of anti-IFN-γ neutralizing autoantibodies were detectable in two patients with OIs. Immunoblotting assay revealed more effective inhibition of STAT1-phosphorylation in THP-1 cells treated with sera from autoantibody-positive AOSD patients (56.7 ± 34.79%) compared with those from HC (104.3 ±29.51%), which was also demonstrated in flow-cytometry analysis (47.13 ± 40.99 vs. 97.92 ± 9.48%, p < 0.05). Depleted serum IgG from anti-IFN-γ autoAbs-positive AOSD patients with OIs restored phosphorylated STAT-1 upon IFN-γ treatment. Sera from autoantibody-positive AOSD patients more effectively inhibited IFN-γ-mediated production of MCP-1 (45.65 pg/ml) and IP-10 (22.44 pg/ml) than sera from HC (263.1 pg/ml and 104.0 pg/ml, both p < 0.05). Serum samples showing the strongest inhibition of IFN-γ-signaling were from two patients with high-titer autoantibodies and OIs.

Conclusion

AOSD patients have a high positive rate and titers of anti-IFN-γ autoantibodies. The remarkable blockade effect of high-titer autoantibodies on IFN-γ-mediated STAT1-phosphorylation and chemokines could make these patients susceptible to OIs.

Case report: Drug rash with eosinophilia and systemic symptoms syndrome in a patient with anti–interferon-γ autoantibody–associated immunodeficiency

A 56-year-old Chinese woman with previous disseminated mycobacterium avium complex infection and recurrent cervical abscesses from Burkholderia cepacia complex visited our hospital. She was diagnosed with adult-onset immunodeficiency (AOID) and tested positive for interferon-γ–neutralizing autoantibody. Ceftazidime was administered as the initial antimicrobial treatment, which was later combined with sulfamethoxazole-trimethoprim (SMZ-TMP). She developed drug rash with eosinophilia and systemic symptoms (DRESS) syndrome after SMZ-TMP administration and improved after withdrawal of the culprit antibiotic and systemic glucocorticoids treatment. Her cervical infection was eventually cured after combined therapy of long-term antibiotics and anti–IFN-γ autoantibodies (AIGA) titer-lowering treatments including glucocorticoids, rituximab, and plasmapheresis. This is the first case of DRESS syndrome in the setting of AIGA-induced AOID and is worthy of notice.

An Updated Review on MSMD Research Globally and A Literature Review on the Molecular Findings, Clinical Manifestations, and Treatment Approaches in China

Mendelian susceptibility to mycobacterial disease (MSMD) arises from a group of rare inherited errors of immunity that result in selective susceptibility of otherwise healthy people to clinical disease caused by low virulence strains of mycobacteria, such as Mycobacterium bovis Bacille Calmette-Guérin (BCG) and environmental mycobacteria. Patients have normal resistance to other pathogens and no overt abnormalities in routine immunological and hematological evaluations for primary immunodeficiencies. At least 19 genes and 34 clinical phenotypes have been identified in MSMD. However, there have been no systematic reports on the clinical characteristics and genetic backgrounds of MSMD in China. In this review, on the one hand, we summarize an update findings on molecular defects and immunological mechanisms in the field of MSMD research globally. On the other hand, we undertook a systematic review of PubMed (MEDLINE), the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, EMBASE, CNKI, and Wanfang to identify articles published before Jan 23, 2022, to summarize the clinical characteristics, diagnosis, treatment, and prognosis of MSMD in China. All the English and Chinese publications were searched without any restriction on article types.

Anti-Interferon Autoantibodies in Adult-Onset Immunodeficiency Syndrome and Severe COVID-19 Infection

Adult-onset immunodeficiency syndrome due to anti-interferon (IFN)-γ autoantibodies has attracted much attention in recent years. It usually occurs in previously healthy people and usually presents as chronic, recurrent, and hard-to-control infections that can be effectively treated with aggressive antibiotic therapy. Adult-onset immunodeficiency syndrome is also referred to as AIDS-like syndrome. Anti-type I IFN (IFN-I) autoantibodies have been reported to play a significant role in the pathogenesis of coronavirus disease 2019 (COVID-19) and preexisting anti-IFN-I autoantibodies are associated with an increased risk of severe COVID-19. This review summarizes the effects of anti-IFN autoantibodies on the susceptibility and severity of various infectious diseases, including SARS-CoV-2 infection. In addition, we discuss the role of anti-IFN autoantibodies in the pathogenesis of autoimmune diseases that are characterized by recurrent infections.

Immunodeficiency and Autoantibodies to Cytokines

BACKGROUND

Anti-cytokine autoantibodies (AAbs) associated with an infectious phenotype are now included along with anti-complement AAbs and somatic pathogenic gene variants as a distinct category termed 'phenocopies of primary immunodeficiencies' in the classification of inborn errors of immunity. Anti-cytokine AAbs target specific cytokine pathways, leading to inordinate susceptibility to specific organisms, generally in the setting of immunocompetence.

CONTENT

Anti-cytokine AAbs are detected in the majority of healthy individuals and may play a regulatory role in limiting exaggerated responses to cytokines. While it is not well understood why some individuals with anti-cytokine AAbs develop increased susceptibility to organisms of low pathogenicity and others do not, it is likely that genetics and environment play a role. To date, AAbs to interferon gamma (IFNγ), interferon alpha (IFNα), interleukins-17 and 22 (IL-17/IL-22), interleukin-6 and granulocyte macrophage colony stimulating factor (GM-CSF) and their association with increased susceptibility to nontuberculous mycobacteria and other intracellular organisms, viral infections, Candida albicans, Staphylococcus aureus and other pyogenic organisms, and fungal infections respectively, have been described. The clinical phenotype of these patients is very similar to that of individuals with pathogenic gene variants in the specific cytokine pathway that the autoantibody targets, hence the term 'phenocopy.' Recognition of anti-cytokine AAbs as a distinct cause of immunodeficiency or immune dysregulation is important for appropriate management of such patients.

SUMMARY

Understanding the roles that anti-cytokine AAbs play in health and disease continues to be a fascinating area of research. Evaluating generally immunocompetent individuals who present with chronic, treatment refractory, or unusual infections for anti-cytokine AAbs is critical as it may direct therapy and disease management.

Anti-interferon-γ autoantibody-associated immunodeficiency

Anticytokine autoantibodies are an emerging disease etiology, through the disturbance of physiological functions of cognate cytokines. Anti-interferon (IFN)-γ autoantibodies (AIGAs) were first identified in patients with severe mycobacterial infections, and were considered to be an autoimmune phenocopy of inborn genetic errors of the IL-12/IFN-γ axis. More than 600 reported cases, most originating from Southeast Asia, have been diagnosed over the last decade. Specific HLA class II molecules are associated with these autoantibodies, which provide a genetic basis for the high prevalence of this immunodeficiency syndrome in certain ethnic groups. Salmonellosis and herpes zoster reactivation are observed in more than half the patients with AIGAs. Moreover, AIGAs have been shown to underlie severe Taralomyce marneffei infection in HIV-negative patients. AIGAs may, thus, be considered a new form of late-onset immunodeficiency conferring a predisposition not only to severe mycobacterial, but also to some bacterial and fungal infections.

Treatment Dilemmas in Disseminated Nontuberculous Mycobacterial Infections With Interferon-gamma Autoantibodies

Disseminated Mycobacterium avium complex (dMAC) is typically seen in individuals with impaired cell-mediated immunity and is best described in those with HIV. Recently, cases have been described in otherwise healthy individuals with neutralizing antibodies to interferon-gamma (nIFNγ-autoAb), especially in patients of Southeast Asian descent. Treatment is often refractory to mycobacterial therapies, and the use of rituximab and other immunomodulatory agents has been explored. We report 3 cases of dMAC with nIFN-γ-autoAb and review the available literature on treatment strategies to provide a framework for the management of patients with refractory infections in the context of neutralizing antibodies to interferon-gamma.

Natural History and Evolution of Anti-Interferon-γ Autoantibody-Associated Immunodeficiency Syndrome in Thailand and the United States

BACKGROUND

The natural history of anti-interferon-γ (IFN-γ) autoantibody-associated immunodeficiency syndrome is not well understood.

METHODS

Data of 74 patients with anti-IFN-γ autoantibodies at Srinagarind Hospital, Thailand, were collected annually (median follow-up duration, 7.5 years). Annual data for 19 patients and initial data for 4 patients with anti-IFN-γ autoantibodies at the US National Institutes of Health were collected (median follow-up duration, 4.5 years). Anti-IFN-γ autoantibody levels were measured in plasma samples.

RESULTS

Ninety-one percent of US patients were of Southeast Asian descent; there was a stronger female predominance (91%) in US than Thai (64%) patients. Mycobacterium abscessus (34%) and Mycobacterium avium complex (83%) were the most common nontuberculous mycobacteria in Thailand and the United States, respectively. Skin infections were more common in Thailand (P = .001), whereas bone (P < .0001), lung (P = .002), and central nervous system (P = .03) infections were more common in the United States. Twenty-four percent of Thai patients died, most from infections. None of the 19 US patients with follow-up data died. Anti-IFN-γ autoantibody levels decreased over time in Thailand (P < .001) and the United States (P = .017), with either cyclophosphamide (P = .01) or rituximab therapy (P = .001).

CONCLUSIONS

Patients with anti-IFN-γ autoantibodies in Thailand and the United States had distinct demographic and clinical features. While titers generally decreased with time, anti-IFN-γ autoantibody disease had a chronic clinical course with persistent infections and death. Close long-term surveillance for new infections is recommended.

Minireview: Insights into anti-interferon-γ autoantibodies

The association between the presence of anti-interferon-γ autoantibodies and the onset of immunodeficiency with intracellular infections has been clearly established. No standard regimen to control the production of these pathogenic autoantibodies, apart from antimicrobial therapy to eliminate infections, contributes to the medical burden of this syndrome, which sometimes has a fatal outcome. In this review, we summarize the findings on anti-interferon-γ autoantibodies to facilitate further research and to provide guidance for treatment strategies.

Autoantibodies against cytokines: phenocopies of primary immunodeficiencies?

Anti-cytokine autoantibodies may cause immunodeficiency and have been recently recognized as ‘autoimmune phenocopies of primary immunodeficiencies’ and are found in particular, but not exclusively in adult patients. By blocking the cytokine’s biological function, patients with anti-cytokine autoantibodies may present with a similar clinical phenotype as the related inborn genetic disorders. So far, autoantibodies to interferon (IFN)-γ, GM-CSF, to a group of TH-17 cytokines and to IL-6 have been found to be causative or closely associated with susceptibility to infection. This review compares infectious diseases associated with anti-cytokine autoantibodies with primary immunodeficiencies affecting similar cytokines or related pathways.

Serum Anti-interferon-γ Autoantibody Titer as a Potential Biomarker of Disseminated Non-tuberculous Mycobacterial Infection

PURPOSE

In the past decade, the relationship between naturally occurring interferon-γ-neutralizing autoantibodies (IFNγ-Ab) and disseminated non-tuberculous mycobacteria (NTM) infection has been established. Furthermore, immune suppressive therapy aimed at the suppression of antibody production has shown efficacy as a supportive treatment. However, the nature of antibody behavior and antibody titer during the course of this disease, as well as the pathophysiological significance of IFNγ-Ab, has not yet been fully elucidated.

METHODS

Thirteen Japanese subjects suffering from disseminated NTM (dNTM) infection with IFNγ-Ab were evaluated. The fluctuation of IFNγ-Ab titer and the neutralizing capacity against IFN-γ during the course of the disease were retrospectively analyzed. IFNγ-Ab titers in the sera were quantified using an enzyme-linked immunosorbent assay; neutralizing capacity was evaluated via flow cytometry.

RESULTS

Serum antibody titers were not constant during the treatment period and varied over the course of the disease. The antibody titer decreased when the disease was improved by anti-mycobacterial treatment (p < 0.01) and increased as the disease progressed (p < 0.05). Even after the antibody titer decreased, the neutralizing capacity against IFN-γ was maintained by individual sera.

CONCLUSIONS

Despite the improvement in the pathological condition via treatment, the patients' sera maintained neutralizing capacity against IFN-γ. Antibody titer fluctuated over the course of the disease and exhibited potential as a biomarker for judgment of the disease state.

The level of natural autoantibodies to IFN-gamma in varicella infection treated with antiviral drug Anaferon for children: A pilot study

Natural circulating antibodies (NAbs) to endogenous regulators have shown to be potential biomarkers in medicine. Due to the lack of reliable assays, only few of them have been well studied. To employ NAbs as biomarkers, an evaluation of changes over the course of a treatment is required. This paper describes our work to analyze the dynamics of NAbs titer to interferon-gamma (IFN-γ) among healthy children of different age and in patients with varicella infection receiving an antiviral drug Anaferon for children (AC, the API are highly diluted antibodies to IFN-γ) in comparison with placebo, and to correlate the findings with the treatment results. IFN-γ plays an essential role during varicella infection, and this fact causes the consequent increase of NAbs to IFN-γ level. The mean anti-IFN-γ NAbs level in the healthy volunteer group was 101 × 10³ U/ml (age: 0-15 years), which was significantly lower than the mean pre-treatment value in patients with varicella infection 167 × 10³ U/ml (age: 3-17 years). In the AC group, the NAbs level observed on days 5 and 10 decreased significantly to a level of 154 × 10³ U/ml, whereas in the placebo group it continued to rise in a time-dependent manner reaching 229 × 10³ U/ml on day 10. Our findings suggest that treatment with AC is characterized by "normalization" of the anti-IFN-γ NAbs levels in patients with varicella infection.

Functional Analysis of Anti-cytokine Autoantibodies Using Flow Cytometry

Autoantibodies to cytokines are increasingly being detected in association with immunodeficient, autoimmune and immune dysregulated states. Presence of these autoantibodies in an otherwise healthy individual may result in a unique phenotype characterized by predisposition to infection with specific organisms. The ability to detect these autoantibodies is of importance as it may direct treatment toward a combination of anti-microbial agents and immunomodulatory therapies that decrease autoantibody levels, thereby releasing the immune system from autoantibody-mediated inhibition. Ligand binding assays such as ELISA or bead multiplex assays have been used to detect these antibodies. However, not all anti-cytokine autoantibodies have demonstrable function in vitro and therefore their clinical significance is unclear. Assays that evaluate the functionality of anti-cytokine autoantibodies can supplement such ligand binding assays and add valuable functional information that, when viewed in the context of the clinical phenotype, may guide the use of adjunctive immunomodulatory therapy. This mini review provides an overview of anti-cytokine autoantibodies identified to date and their clinical associations. It also describes the use of flow cytometry for the functional analysis of anti-IFNγ and anti-GM-CSF autoantibodies.

Juvenile-Onset Immunodeficiency Secondary to Anti-Interferon-Gamma Autoantibodies

Immunodeficiency secondary to anti-interferon-gamma (anti-IFN-γ) autoantibodies was first described in 2004 as an acquired defect in the IFN-γ pathway leading to susceptibility to multiple opportunistic infections, including dimorphic fungi, parasites, and bacteria, especially tuberculosis and non-tuberculous mycobacterium (NTM) species. It has so far only been described in adult patients. We present 2 cases of disseminated NTM infections in otherwise immunocompetent children. A 16-year-old girl with Sweet's syndrome-like neutrophilic dermatosis developed recurrent fever and cervical lymphadenitis secondary to Mycobacterium abscessus. A 10-year-old boy with a history of prolonged fever, aseptic meningitis, aortitis, and arteritis in multiple blood vessels developed thoracic vertebral osteomyelitis secondary to Mycobacterium avium complex. Both patients were found to have positive serum neutralizing anti-IFNγ autoantibodies. Testing for anti-IFNγ autoantibodies should be considered in otherwise healthy immunocompetent hosts with recurrent or disseminated NTM infection. This represents a phenocopy of primary immunodeficiency which has been recently described only in adults. We report the first two cases of this phenomenon to affect children.

Disseminated and Congenital Toxoplasmosis in a Mother and Child With Activated PI3-Kinase δ Syndrome Type 2 (APDS2): Case Report and a Literature Review of Toxoplasma Infections in Primary Immunodeficiencies

Phosphoinositide 3-kinase (PI3K) plays an integral role in lymphocyte function. Mutations in PIK3CD and PIK3R1, encoding the PI3K p110δ and p85α subunits, respectively, cause increased PI3K activity and result in immunodeficiency with immune dysregulation. We describe here the first cases of disseminated and congenital toxoplasmosis in a mother and child who share a pathogenic mutation in PIK3R1 and review the mechanisms underlying susceptibility to severe Toxoplasma gondii infection in activated PI3Kδ syndrome (APDS) and in other forms of primary immunodeficiency.

Laboratory evaluation of the IFN-γ circuit for the molecular diagnosis of Mendelian susceptibility to mycobacterial disease

The integrity of the interferon (IFN)-γ circuit is necessary to mount an effective immune response to intra-macrophagic pathogens, especially Mycobacteria. Inherited monogenic defects in this circuit that disrupt the production of, or response to, IFN-γ underlie a primary immunodeficiency known as Mendelian susceptibility to mycobacterial disease (MSMD). Otherwise healthy patients display a selective susceptibility to clinical disease caused by poorly virulent mycobacteria such as BCG (bacille Calmette-Guérin) vaccines and environmental mycobacteria, and more rarely by other intra-macrophagic pathogens, particularly Salmonella and M. tuberculosis. There is high genetic and allelic heterogeneity, with 19 genetic etiologies due to mutations in 10 genes that account for only about half of the patients reported. An efficient laboratory diagnostic approach to suspected MSMD patients is important, because it enables the establishment of specific therapeutic measures that will improve the patient's prognosis and quality of life. Moreover, it is essential to offer genetic counseling to affected families. Herein, we review the various genetic and immunological diagnostic approaches that can be used in concert to reach a molecular and cellular diagnosis in patients with MSMD.

Repurposing QuantiFERON for Detection of Neutralizing Interferon-γ Autoantibodies in Patients With Nontuberculous Mycobacterial Infections

Nontuberculous mycobacterial infections due to autoantibodies targeting interferon-γ are an emerging medical problem. However, case finding is hampered due to highly complex diagnostic procedures not available in routine laboratories. We show that QuantiFERON assays can be exploited as a simple screening tool that may facilitate adequate and timely treatment.

Characterization of anti-interferon-γ antibodies in HIV-negative immunodeficient patients infected with unusual intracellular microorganisms

A major characteristic of immunodeficiency associated with life-threatening intracellular infection in adults is the presence of anti-interferon-γ antibodies. Although little is known about the mechanism underlying this syndrome, it is believed that the antibodies inhibit the activity of downstream signaling pathway of interferon-γ. In this study, the characteristics of these antibodies in patients who presented, or have a history of, intracellular infection and were positive to anti-interferon-γ antibodies were investigated. The antibodies exhibited mainly the IgG1 and the IgG4 subtypes and recognized the C-terminal of the interferon-γ linear epitope containing the KRKR motif, which is required for the biological activity of interferon-γ. The antibodies bound to recombinant interferon-γ with significantly lower avidity than antibodies to a recall antigen, tetanus toxoid, suggesting that the antibodies might have not undergone affinity maturation. The data from this study may provide fundamental information to better understand the properties of anti-interferon-γ antibodies, which can be useful for future studies. Impact statement An increase in the number of immunodeficient patients related to autoantibodies to interferon (IFN)-γ has been observed particularly in East Asian adults. These patients are often presented with opportunistic infections caused by intracellular pathogens, including non-tuberculous mycobacteria (NTM), Cryptococcus neoformans, Penicillium marneffei (now called Talaromyces marneffei), and non-typhoidal Salmonella spp. The mortality rate for this syndrome is relatively high with 32% patients dying at the median time of 25 months after diagnosis. Characterization of these autoantibodies may promote better understanding of the syndrome, an emerging health problem affecting East Asia populations and impeding their welfare and economic development.

Anticytokine autoantibodies in infection and inflammation: an update

PURPOSE OF REVIEW

Concise overview of the field of anticytokine autoantibodies with a focus on recent developments.

RECENT FINDINGS

Advances in particular in the analysis of autoantibodies to IFNγ, granulocyte-macrophage colony-stimulating factor (GM-CSF) and type I IFN are presented. The target epitope for anti-IFNγ autoantibodies has been found to have high homology to a protein from Aspergillus suggesting molecular mimicry as a mechanism of breaking self-tolerance. A treatment strategy using a recombinant, epitope-depleted version of IFNγ is suggested. Autoantibodies to GM-CSF are associated with disseminated Crytococcus and Nocardia infections thus expanding the spectrum of associated diseases beyond pulmonary alveolar proteinosis. Detailed analysis of anti-GM-CSF autoantibody clones derived from pulmonary alveolar proteinosis patients show evidence of high somatic mutation suggesting T cell-dependent affinity maturation; full GM-CSF neutralization is achieved by synergistic binding of antibodies targeting various distinct noncross-reactive epitopes and leading to antigen sequestration and Fc-mediated clearance. Single mAbs in contrast may lead to higher GM-CSF bioavailability. Anti type I IFN-specific autoantibodies derived from autoimmune polyglandular syndrome type I patients are of extreme high affinity and negatively correlate with the incidence of type I diabetes and may be thus considered to be protective. Hypomorphic severe combined immune deficiency may be associated with complex anticytokine patterns and the emergence of anti type I IFN autoantibodies correlates with severe viral infection histories.

SUMMARY

Anticytokine autoantibodies may cause susceptibility to infections. In autoimmune/autoinflammatory conditions, anticytokine autoantibodies may be protective or promote disease.

Use of QuantiFERON-TB Gold In-tube assay in screening for neutralizing anti-interferon-γ autoantibodies in patients with disseminated nontuberculous mycobacterial infection

OBJECTIVE

Anti-interferon- γ (IFN-γ) autoantibodies (anti-IFN-γ Abs) have been increasingly recognized as an important cause of disseminated nontuberculous mycobacterial (DNTM) infection, and identification of this immunodeficiency impacts clinical management. However, the protean disease manifestations and inaccessibility to diagnostic tests in clinical settings hamper its early diagnosis. Here, we sought to determine whether QuantiFERON-TB Gold In-tube (QFT-GIT), a commercialized IFN-γ release assay, could be used to screen for neutralizing anti-IFN-γ Abs among previously healthy adults with DNTM infection.

METHODS

Non-HIV patients with DNTM infection were prospectively enrolled for the QFT-GIT assays. We measured their plasma concentration of anti-IFN-γ Abs and their neutralizing capacity through enzyme-linked immunosorbent assay and flow cytometry. We then analysed the correlation between QFT-GIT results and the presence of neutralizing anti-IFN-γ Abs among patients with and without previously recognized immunosuppression, respectively.

RESULTS

Irrespective of the autoantibody concentration or disease activity, all patients with neutralizing anti-IFN-γ Abs (100%, 30/30) had indeterminate QFT-GIT results because of extremely low or undetectable IFN-γ levels in the mitogen tubes. None of the four DNTM patients who were previously healthy and tested negative of anti-IFN-γ Abs had an indeterminate QFT-GIT result, and their IFN-γ levels in the mitogen tube were significantly higher than those of the patients with anti-IFN-γ Abs (8.28 IU/mL vs. 0.05 IU/mL, p 0.001).

CONCLUSION

An indeterminate QFT-GIT result because of undetectable or extremely low IFN-γ level in the mitogen tube suggests the presence of neutralizing anti-IFN-γ Abs in a previously healthy patient with DNTM infection.

Patient ethnicity and causative species determine the manifestations of anti-interferon-gamma autoantibody-associated nontuberculous mycobacterial disease: a review

Nontuberculous mycobacteria (NTM) infections involving anti-interferon-gamma (IFN-γ)-neutralizing autoantibodies have been described in previously immunocompetent adults. To investigate the factors underlying various disease manifestations, we reviewed 35 articles published between January 2004 and November 2016 and identified 111 NTM patients with anti-IFN-γ autoantibodies. Rapidly growing mycobacteria (RGM) accounted for 53% of the isolated species. RGM were predominant among the NTM species isolated from Thai (73%), Chinese (58%) and Filipino (56%) patients, whereas M. avium complex (MAC) was predominant among Japanese (58%) and non-Asian (80%) patients. The commonly involved organs included the lymph nodes (79%), bones/joints (34%) and lungs (32%). Compared with the patients with MAC, the patients with RGM had a higher incidence of lymph node lesions (P<0.05) and a lower incidence of bone/joint (P<0.01), lung (P<0.01), soft tissue (P<0.01), bronchus (P<0.01) and muscle (P<0.05) lesions. Clinical manifestations of NTM disease with anti-IFN-γ-neutralizing autoantibodies differ across ethnicities and NTM species.

Anticytokine Autoantibodies: Association with Infection and Immune Dysregulation

The association of autoantibodies to cytokines with immune deficiency, autoimmunity and/or immune dysregulation is increasingly being recognized. For example, autoantibodies to interferon gamma have been found to be associated with chronic, treatment refractory infections with intracellular organisms such as mycobacteria, autoantibodies to interleukin 17 with chronic mucocutaneous candidiasis, and anti-interferon alpha autoantibodies with systemic lupus erythematosus. While low titer autoantibodies to these and other cytokines may be detected in normal individuals, patients with infectious or autoimmune manifestations tend to have high titer autoantibodies that may block or potentiate the function of the respective cytokine. Recognition of these autoantibodies is important because it may direct treatment toward a combination of adjunctive immunotherapy to modulate the autoantibody level while continuing with appropriate anti-microbial therapy. This review focuses on the anti-cytokine autoantibodies documented to date, their autoimmune, immune dysregulation and infectious disease associations, methods for detection of these antibodies and potential treatment options.