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Mendelian susceptibility to mycobacterial disease (MSMD) is characterized by a selective predisposition to clinical disease caused by the Bacille Calmette-Guérin (BCG) vaccine and environmental mycobacteria. The known genetic etiologies of MSMD are inborn errors of IFN-γ immunity due to mutations of 15 genes controlling the production of or response to IFN-γ. Since the first MSMD-causing mutations were reported in 1996, biallelic mutations in the genes encoding IFN-γ receptor 1 (IFN-γR1) and IFN-γR2 have been reported in many patients of diverse ancestries. Surprisingly, mutations of the gene encoding the IFN-γ cytokine itself have not been reported, raising the remote possibility that there might be other agonists of the IFN-γ receptor. We describe 2 Lebanese cousins with MSMD, living in Kuwait, who are both homozygous for a small deletion within the IFNG gene (c.354_357del), causing a frameshift that generates a premature stop codon (p.T119Ifs4*). The mutant allele is loss of expression and loss of function. We also show that the patients’ herpesvirus Saimiri–immortalized T lymphocytes did not produce IFN-γ, a phenotype that can be rescued by retrotransduction with WT IFNG cDNA. The blood T and NK lymphocytes from these patients also failed to produce and secrete detectable amounts of IFN-γ. Finally, we show that human IFNG has evolved under stronger negative selection than IFNGR1 or IFNGR2, suggesting that it is less tolerant to heterozygous deleterious mutations than IFNGR1 or IFNGR2. This may account for the rarity of patients with autosomal-recessive, complete IFN-γ deficiency relative to patients with complete IFN-γR1 and IFN-γR2 deficiencies.

Background: The heterogeneity of COVID-19 lies within its diverse symptoms and severity, ranging from mild to lethal. Acute respiratory distress syndrome (ARDS) has been shown to be the leading cause of mortality in COVID-19 patients, characterized by a hyper cytokine storm. Autoimmunity is proposed to occur as a result of COVID-19, given the high similarity of the immune responses observed in COVID-19 and autoimmune diseases. Results: Here, we investigate the level of autoimmune antibodies in COVID-19 patients with different severities. Initial screening for antinuclear antibodies (ANA) IgG revealed that 1.6% (2/126) and 4% (5/126) of ICU COVID-19 cases developed strong and moderate ANA levels, respectively. However, all the non-ICU cases (n = 273) were ANA negative. The high ANA level was confirmed by immunofluorescence (IFA) and large-scale autoantibody screening by phage immunoprecipitation-sequencing (PhIP-Seq). Indeed, the majority of the samples showed "speckled" ANA pattern by microscopy, and we demonstrate that samples of ICU patients with strong and moderate ANA levels contain autoantibody specificities that predominantly targeted proteins involved in intracellular signal transduction, metabolism, apoptotic processes, and cell death; further denoting reactivity to nuclear and cytoplasmic antigens. Conclusion:Our results further support the notion of routine screening for autoimmune responses in COVID-19 patients, which might help improve disease prognosis and patient management. Further, results provide compelling evidence that ANA-positive individuals should be excluded from being donors for convalescent plasma therapy in the context of Covid-19.

We studied a child with severe viral, bacterial, fungal, and parasitic diseases, who was homozygous for a loss-of-function mutation of REL, encoding c-Rel, which is selectively expressed in lymphoid and myeloid cells. The patient had low frequencies of NK, effector memory cells reexpressing CD45RA (Temra) CD8(+) T cells, memory CD4(+) T cells, including Th1 and Th1*, Tregs, and memory B cells, whereas the counts and proportions of other leukocyte subsets were normal. Functional deficits of myeloid cells included the abolition of IL-12 and IL-23 production by conventional DC1s (cDC1s) and monocytes, but not cDC2s. c-Rel was also required for induction of CD86 expression on, and thus antigen-presenting cell function of, cDCs. Functional deficits of lymphoid cells included reduced IL-2 production by naive T cells, correlating with low proliferation and survival rates and poor production of Th1, Th2, and Th17 cytokines by memory CD4(+) T cells. In naive CD4(+) T cells, c-Rel is dispensable for early IL2 induction but contributes to later phases of IL2 expression. The patient’s naive B cells displayed impaired MYC and BCL2L1 induction, compromising B cell survival and proliferation and preventing their differentiation into Ig-secreting plasmablasts. Inherited c-Rel deficiency disrupts the development and function of multiple myeloid and lymphoid cells, compromising innate and adaptive immunity to multiple infectious agents.

Most patients with autosomal dominant hyper-IgE syndrome (AD-HIES) are heterozygous for rare STAT3 variants. The mechanism of dominance was recently questioned. The authors show that both in-frame and out-of-frame STAT3 variants underlie AD-HIES by negative dominance and not haploinsufficiency., Most patients with autosomal dominant hyper-IgE syndrome (AD-HIES) carry rare heterozygous STAT3 variants. Only six of the 135 in-frame variants reported have been experimentally shown to be dominant negative (DN), and it has been recently suggested that eight out-of-frame variants operate by haploinsufficiency. We experimentally tested these 143 variants, 7 novel out-of-frame variants found in HIES patients, and other STAT3 variants from the general population. Strikingly, all 15 out-of-frame variants were DN via their encoded (1) truncated proteins, (2) neoproteins generated from a translation reinitiation codon, and (3) isoforms from alternative transcripts or a combination thereof. Moreover, 128 of the 135 in-frame variants (95%) were also DN. The patients carrying the seven non-DN STAT3 in-frame variants have not been studied for other genetic etiologies. Finally, none of the variants from the general population tested, including an out-of-frame variant, were DN. Overall, our findings show that heterozygous STAT3 variants, whether in or out of frame, underlie AD-HIES through negative dominance rather than haploinsufficiency., Graphical Abstract

Heterozygous in-frame mutations in coding regions of human STAT3 underlie the only known autosomal dominant form of hyper IgE syndrome (AD HIES). About 5% of familial cases remain unexplained. The mutant proteins are loss-of-function and dominant-negative when tested following overproduction in recipient cells. However, the production of mutant proteins has not been detected and quantified in the cells of heterozygous patients. We report a deep intronic heterozygous STAT3 mutation, c.1282-89C>T, in 7 relatives with AD HIES. This mutation creates a new exon in the STAT3 complementary DNA, which, when overexpressed, generates a mutant STAT3 protein (D427ins17) that is loss-of-function and dominant-negative in terms of tyrosine phosphorylation, DNA binding, and transcriptional activity. In immortalized B cells from these patients, the D427ins17 protein was 2 kDa larger and 4-fold less abundant than wild-type STAT3, on mass spectrometry. The patients’ primary B and T lymphocytes responded poorly to STAT3-dependent cytokines. These findings are reminiscent of the impaired responses of leukocytes from other patients with AD HIES due to typical STAT3 coding mutations, providing further evidence for the dominance of the mutant intronic allele. These findings highlight the importance of sequencing STAT3 introns in patients with HIES without candidate variants in coding regions and essential splice sites. They also show that AD HIES-causing STAT3 mutant alleles can be dominant-negative even if the encoded protein is produced in significantly smaller amounts than wild-type STAT3.

Background Current non-invasive methods of assessing disease activity in systemic lupus erythematosus (SLE) are of limited sensitivity and specificity. Testing includes acute phase markers, autoantibodies and complement levels. Although measurements of dsDNA antibodies and complement C3/C4 levels are routine, they remain of limited value. Improved blood and urine markers may help in early detection of flare, distinction between flare and chronic damage, and monitoring response to therapy. Methods A total of 87 patients with SLE were tested for the following cytokines in serum and urine: monocyte chemoattractant protein 1 (MCP-1), regulated upon activation, normal T cell expressed and secreted (RANTES), soluble tumour necrosis factor receptor 1 (sTNF-R1), interferon-inducible protein 10 (IP-10), monocyte inhibitory protein 1α (MIP-1α) and vascular endothelial growth factor (VEGF). Patients attending the Lupus Unit at St Thomas’ Hospital, London, UK were divided into active lupus nephritis (LN), inactive LN and non-renal SLE groups based on their renal pathology and SLE disease activity index (SLEDAI). Cytokine testing was performed using the FIDIS multiplex bead assay. Results The mean level of serum sTNF-R1 was higher in the active LN group compared with both inactive LN and non-renal SLE groups ( p Conclusion These results indicate that for active LN, sTNF-R1 could be a useful serum cytokine marker, with potential for VEGF in the urine. This study has confirmed the ability of the multiplex bead technique to detect cytokines in a good analytical range, including very low and high levels, in both serum and urine. Combining serum and urine markers provided additional sensitivity in distinguishing active from inactive LN.

International audience; A dozen species of human and animal pathogens have been described to date in the Bordetella genus, with the majority being respiratory tract pathogens. Bordetella avium lipopolysaccharides have been shown to be important virulence factors for this bird pathogen. B. hinzii is closely related to the B. avium species, but has also been isolated from humans. B. trematum is associated to ear and blood infections in humans. Its lipid A structure, the biological active moiety of LPS, was found to be closely related to those of B. avium and B. hinzii. It is important to unveil the subtle structural modifications orchestrated during the LPS biosynthetic pathway to better understand host adaptation. The present data are also important in the context of deciphering the virulence pathways of this important genus containing the major pathogens B. pertussis and B. parapertussis, responsible for whooping cough. We recently reported the isolated lipid A structures of the three presented species, following the previously identified O-chain structures. In the present study, we provide details on the free and O-chain-linked core oligosaccharides which were required to characterize the complete LPS structures. Data are presented here in relation to relevant biosynthesis genes. The present characterization of the three species is well illustrated by Matrix Assisted Laser Desorption Mass Spectrometry experiments, and data were obtained mainly on native LPS molecules for the first time. (C) 2018 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved.

Purpose. Human serine/threonine kinase 4 (STK4) deficiency is a rare, autosomal recessive genetic disorder leading to combined immunodeficiency. The extent to which STK4 deficiency impairs immune signaling and host defenses is unclear. We assessed the functional consequences of a novel, homozygous nonsense STK4 mutation (NM_006282.2:c.871C>T, p.Arg291*) found in a pediatric patient by comparing the patient’s innate and adaptive cell-mediated and humoral immune responses with those of three heterozygous relatives and unrelated controls.Methods. The genetic etiology was identified by whole genome sequencing and confirmed by Sanger sequencing. STK4 gene and protein expression was measured by quantitative RT-PCR and immunoblotting, respectively. Cellular abnormalities were assessed by high-throughput RT-RCR, RNA-Seq, ELISA and polychromatic flow cytometry. Finally, antibody responses were delinated by ELISA and phage immunoprecipitation-sequencing.Results. The affected patient exhibited partial loss of STK4 expression and complete loss of STK4 function. The patient suffered from recurrent viral and bacterial infections, most notably persistent Epstein-Barr virus viremia and pulmonary tuberculosis. Cellular and molecular analyses revealed abnormalities to the fractions of T-cell subsets, plasmacytoid dendritic cells, and NK cells. The transcriptional responses of the patient’s whole blood and PBMC samples were reminiscent of dysregulated interferon signaling, impaired T immunity and increased T-cell apoptosis. Nonetheless, the patient had detectable vaccine-specific antibodies and IgG responses to various pathogens, consistent with a normal CD19 + B-cell fraction, albeit with a distinctive antibody repertoire, largely driven by herpesvirus antigens.Conclusion. Patients with STK4 deficiency can exhibit broad impairment of immune function extending beyond lymphoid cells.

The heterogeneity of COVID-19 lies within its diverse symptoms and severity, ranging from mild to lethal. Acute respiratory distress syndrome (ARDS) has been shown to be the leading cause of mortality in COVID-19 patients, characterized by a hyper cytokine storm. Autoimmunity is proposed to occur as a result of COVID-19, given the high similarity of the immune responses observed in COVID-19 and autoimmune diseases. Here, we investigate the level of autoimmune antibodies in COVID-19 patients with different severities. Initial screening for antinuclear antibodies (ANA) IgG revealed that 1.6% (2/126) and 4% (5/126) of ICU COVID-19 cases developed strong and moderate ANA levels, respectively. However, all the non-ICU cases (n=273) were ANA negative. The high ANA level was confirmed by immunofluorescence (IFA) and large-scale autoantibody screening by phage immunoprecipitation-sequencing (PhIP-Seq). Indeed, the majority of the samples showed “speckled” ANA pattern by microscopy, and we demonstrate that samples of ICU patients with strong and moderate ANA levels contain autoantibody specificities that predominantly targeted proteins involved in intracellular signal transduction, metabolism, apoptotic processes, and cell death; further denoting reactivity to nuclear and cytoplasmic antigens. In conclusion, our results further support the notion of routine screening for autoimmune responses in COVID-19 patients, which might help improve disease prognosis and patient management. Further, results provide compelling evidence that ANA-positive individuals should be excluded from being donors for convalescent plasma therapy in the context of Covid-19.

Allelic diversity of human leukocyte antigen (HLA) class II genes may help maintain humoral immunity against infectious diseases. In this study, we investigated germline genetic variation in classical HLA class II genes and employed a systematic, unbiased approach to explore the relative contribution of this genetic variation in the antibody repertoire to various common pathogens. We leveraged a well-defined cohort of 800 adults representing the general Arab population in which genetic material is shared because of the high frequency of consanguineous unions. By applying a high-throughput method for large-scale antibody profiling to this well-defined cohort, we were able to dissect the overall effect of zygosity for classical HLA class II genes, as well as the effects associated with specific HLA class II alleles, haplotypes and genotypes, on the antimicrobial antibody repertoire breadth and antibody specificity with unprecedented resolution. Our population genetic studies revealed that zygosity of the classical HLA class II genes is a strong predictor of antibody responses to common human pathogens, suggesting that classical HLA class II gene heterozygosity confers a selective advantage. Moreover, we demonstrated that multiple HLA class II alleles can have additive effects on the antibody repertoire to common pathogens. We also identified associations of HLA-DRB1 genotypes with specific antigens. Our findings suggest that HLA class II gene polymorphisms confer specific humoral immunity against common pathogens, which may have contributed to the genetic diversity of HLA class II loci during hominine evolution.

International audience; Inborn errors of TLR3-dependent IFN-α/β– and IFN-λ–mediated immunity in the CNS can underlie herpes simplex virus 1 (HSV-1) encephalitis (HSE). The respective contributions of IFN-α/β and IFN-λ are unknown. We report a child homozygous for a genomic deletion of the entire coding sequence and part of the 3′-UTR of the last exon of IFNAR1, who died of HSE at the age of 2 years. An older cousin died following vaccination against measles, mumps, and rubella at 12 months of age, and another 17-year-old cousin homozygous for the same variant has had other, less severe, viral illnesses. The encoded IFNAR1 protein is expressed on the cell surface but is truncated and cannot interact with the tyrosine kinase TYK2. The patient’s fibroblasts and EBV-B cells did not respond to IFN-α2b or IFN-β, in terms of STAT1, STAT2, and STAT3 phosphorylation or the genome-wide induction of IFN-stimulated genes. The patient’s fibroblasts were susceptible to viruses, including HSV-1, even in the presence of exogenous IFN-α2b or IFN-β. HSE is therefore a consequence of inherited complete IFNAR1 deficiency. This viral disease occurred in natural conditions, unlike those previously reported in other patients with IFNAR1 or IFNAR2 deficiency. This experiment of nature indicates that IFN-α/β are essential for anti–HSV-1 immunity in the CNS

International audience; Inborn errors of human interferon gamma (IFN-γ) immunity underlie mycobacterial disease. We report a patient with mycobacterial disease due to inherited deficiency of the transcription factor T-bet. The patient has extremely low counts of circulating Mycobacterium-reactive natural killer (NK), invariant NKT (iNKT), mucosal-associated invariant T (MAIT), and Vδ2+ γδ T lymphocytes, and of Mycobacterium-non reactive classic TH1 lymphocytes, with the residual populations of these cells also producing abnormally small amounts of IFN-γ. Other lymphocyte subsets develop normally but produce low levels of IFN-γ, with the exception of CD8+ αβ T and non-classic CD4+ αβ TH1∗ lymphocytes, which produce IFN-γ normally in response to mycobacterial antigens. Human T-bet deficiency thus underlies mycobacterial disease by preventing the development of innate (NK) and innate-like adaptive lymphocytes (iNKT, MAIT, and Vδ2+ γδ T cells) and IFN-γ production by them, with mycobacterium-specific, IFN-γ-producing, purely adaptive CD8+ αβ T, and CD4+ αβ TH1∗ cells unable to compensate for this deficit.

SummaryInborn errors of human IFN-γ immunity underlie mycobacterial disease. We report a patient with mycobacterial disease due to an inherited deficiency of the transcription factor T-bet. This deficiency abolishes the expression of T-bet target genes, including IFNG, by altering chromatin accessibility and DNA methylation in CD4+ T cells. The patient has profoundly diminished counts of mycobacterial-reactive circulating NK, invariant NKT (iNKT), mucosal-associated invariant T (MAIT), and Vδ2+ γδ T lymphocytes, and of non-mycobacterial-reactive classic TH1 lymphocytes, the remainders of which also produce abnormally low amounts of IFN-γ. Other IFN-γ-producing lymphocyte subsets however develop normally, but with low levels of IFN-γ production, with exception of Vδ2− γδ T lymphocytes, which produce normal amounts of IFN-γ in response to non-mycobacterial stimulation, and non-classic TH1 (TH1*) lymphocytes, which produce IFN-γ normally in response to mycobacterial antigens. Human T-bet deficiency thus underlies mycobacterial disease by preventing the development of, and IFN-γ production by, innate (NK) and innate-like adaptive lymphocytes (iNKT, MAIT, and Vδ2+ γδ T cells), with mycobacterial-specific, IFN-γ-producing, purely adaptive αβ TH1* cells unable to compensate for this deficit.

Four endemic human coronaviruses (HCoVs) are commonly associated with acute respiratory infection in humans. B cell responses to these "common cold" viruses remain incompletely understood. Here we report a comprehensive analysis of CoV-specific antibody repertoires in 231 children and 1168 adults using phage-immunoprecipitation sequencing. Seroprevalence of antibodies to endemic HCoVs ranged between ~4 and 27% depending on the species and cohort. We identified at least 136 novel linear B cell epitopes. Antibody repertoires against endemic HCoVs were qualitatively different between children and adults in that anti-HCoV IgG specificities more frequently found among children targeted functionally important and structurally conserved regions of the spike, nucleocapsid and matrix proteins. Moreover, antibody specificities targeting the highly conserved fusion peptide region and S2' cleavage site of the spike protein were broadly cross-reactive with peptides of epidemic human and non-human coronaviruses. In contrast, an acidic tandem repeat in the N-terminal region of the Nsp3 subdomain of the HCoV-HKU1 polyprotein was the predominant target of antibody responses in adult donors. Our findings shed light on the dominant species-specific and pan-CoV target sites of human antibody responses to coronavirus infection, thereby providing important insights for the development of prophylactic or therapeutic monoclonal antibodies and vaccine design., info:eu-repo/semantics/published

The human immune defense mechanisms and factors associated with good versus poor health outcomes following viral respiratory tract infections (VRTI), as well as correlates of protection following vaccination against respiratory viruses, remain incompletely understood. To shed further light into these mechanisms, a number of systems-scale studies have been conducted to measure transcriptional changes in blood leukocytes of either naturally or experimentally infected individuals, or in individual’s post-vaccination. Here we are making available a public repository, for research investigators for interpretation, a collection of transcriptome datasets obtained from human whole blood and peripheral blood mononuclear cells (PBMC) to investigate the transcriptional responses following viral respiratory tract infection or vaccination against respiratory viruses. In total, Thirty one31 datasets, associated to viral respiratory tract infections and their related vaccination studies, were identified and retrieved from the NCBI Gene Expression Omnibus (GEO) and loaded in a custom web application designed for interactive query and visualization of integrated large-scale data. Quality control checks, using relevant biological markers, were performed. Multiple sample groupings and rank lists were created to facilitate dataset query and interpretation. Via this interface, users can generate web links to customized graphical views, which may be subsequently inserted into manuscripts to report novel findings. The GXB tool enables browsing of a single gene across projects, providing new perspectives on the role of a given molecule across biological systems in the diagnostic and prognostic following VRTI but also in identifying new correlates of protection. This dataset collection is available at: http://vri1.gxbsidra.org/dm3/geneBrowser/list.

International audience; Inherited IL-12Rβ1 and TYK2 deficiencies impair both IL-12- and IL-23-dependent IFN-γ immunity and are rare monogenic causes of tuberculosis, each found in less than 1/600,000 individuals. We show that homozygosity for the common TYK2 P1104A allele, which is found in about 1/600 Europeans and between 1/1000 and 1/10,000 individuals in regions other than East Asia, is more frequent in a cohort of patients with tuberculosis from endemic areas than in ethnicity-adjusted controls (P = 8.37 × 10-8; odds ratio, 89.31; 95% CI, 14.7 to 1725). Moreover, the frequency of P1104A in Europeans has decreased, from about 9% to 4.2%, over the past 4000 years, consistent with purging of this variant by endemic tuberculosis. Surprisingly, we also show that TYK2 P1104A impairs cellular responses to IL-23, but not to IFN-α, IL-10, or even IL-12, which, like IL-23, induces IFN-γ via activation of TYK2 and JAK2. Moreover, TYK2 P1104A is properly docked on cytokine receptors and can be phosphorylated by the proximal JAK, but lacks catalytic activity. Last, we show that the catalytic activity of TYK2 is essential for IL-23, but not IL-12, responses in cells expressing wild-type JAK2. In contrast, the catalytic activity of JAK2 is redundant for both IL-12 and IL-23 responses, because the catalytically inactive P1057A JAK2, which is also docked and phosphorylated, rescues signaling in cells expressing wild-type TYK2. In conclusion, homozygosity for the catalytically inactive P1104A missense variant of TYK2 selectively disrupts the induction of IFN-γ by IL-23 and is a common monogenic etiology of tuberculosis.

A hands-on training workshop was devised with omics data used as source material to emulate reductionist investigation approaches. NUDT16, a member of the Nudix hydrolase family was selected as a candidate gene on the basis of: 1) it being upregulated in neutrophils exposed in vitro to serum of patients with sepsis, AND 2) the absence of overlap between the NUDT16 and sepsis, inflammation or neutrophil literature. We next sought to corroborate the initial finding in five public transcriptome sepsis datasets in which NUDT16 transcript levels were measured. In each of these dataset NUDT16 transcript abundance was found to be significantly increased in septic patients in vivo in comparison to uninfected controls. Next, biological concepts were extracted from the NUDT16 literature. The main concepts to emerge from profiling this literature were RNA decapping, inosine triphosphate, and inosine diphosphate. Through these concepts, indirect links could be established between NUDT16 and the sepsis/inflammation/neutrophil literature. A potential role for NUDT16 could, in turn, be inferred in the degradation of mRNAs in activated neutrophils. Follow on experiments that would be necessary in order to further explore such inference are discussed.

Comment in :Who regulates whom: ZNF341 is an additional player in the STAT3/TH17 song. [Sci Immunol. 2018]; International audience; Heterozygosity for human signal transducer and activator of transcription 3 (STAT3) dominant-negative (DN) mutations underlies an autosomal dominant form of hyper-immunoglobulin E syndrome (HIES). We describe patients with an autosomal recessive form of HIES due to loss-of-function mutations of a previously uncharacterized gene, ZNF341 ZNF341 is a transcription factor that resides in the nucleus, where it binds a specific DNA motif present in various genes, including the STAT3 promoter. The patients' cells have low basal levels of STAT3 mRNA and protein. The autoinduction of STAT3 production, activation, and function by STAT3-activating cytokines is strongly impaired. Like patients with STAT3 DN mutations, ZNF341-deficient patients lack T helper 17 (TH17) cells, have an excess of TH2 cells, and have low memory B cells due to the tight dependence of STAT3 activity on ZNF341 in lymphocytes. Their milder extra-hematopoietic manifestations and stronger inflammatory responses reflect the lower ZNF341 dependence of STAT3 activity in other cell types. Human ZNF341 is essential for the STAT3 transcription-dependent autoinduction and sustained activity of STAT3.

Most humans are exposed to Tropheryma whipplei (Tw). Whipple’s disease (WD) strikes only a small minority of individuals infected with Tw (, eLife digest In 1907, George Hoyt Whipple – an American pathologist working at Johns Hopkins University in Baltimore – described a new inflammatory disease that affects the intestine. Patients with this condition, now known as Whipple’s disease, experience diarrhea, weight loss, and abdominal and joint pain. The disease is rare; it affects about one in a million people, mostly those over the age of 50 who are of European descent. Later it was discovered that bacteria called Tropheryma whipplei cause Whipple’s disease and that antibiotics can cure it. These bacteria are widespread and yet only a small minority of individuals infected with T. whipplei goes on to develop Whipple’s disease. In some populations, over 50% of individuals have been infected with the bacteria at some point in their lives, but most will get rid of the infection. This raised the question: when exposed to the same microbe, why do some individuals develop a severe disease, while others remain unharmed? From the 1950s onwards, scientists identified a few families with multiple members who have developed Whipple’s disease. These observations suggested that human genes may play a role in determining whether a person infected with T. whipplei becomes ill. Rare genetic mutations that affect the immune system have also been linked to the development of life-threatening cases of influenza or tuberculosis. Now, Guérin et al. report that, in one French family, an extremely rare mutation in the gene that codes for a protein called IRF4 may contribute to the development of Whipple’s disease. This family had four members with Whipple’s disease, all of whom had one copy of the gene with this rare mutation and one normal copy of the gene. The IRF4 protein acts like a switch that turns on and off some genes involved in the body’s response to infection. In patients with this mutation, the IRF4 protein does not work as it should. Guérin et al. suggest that Whipple’s disease may be caused by specific genetic mutations affecting the immune system in subjects infected by T. whipplei. More studies are needed to see if other genetic mutations also contribute to other cases of Whipple’s disease. Such studies may help physicians to better understand why some people become sick after T. whipplei infections while others do not. They may also help physicians to diagnose the disease, and even lead to better treatments.

We report a child with inherited, complete IRF9 deficiency who suffered from life-threatening influenza pneumonitis. IRF9 deficiency disrupts the activation of ISGF3 and impairs but does not abolish cellular responses to type I IFNs, as some ISGs are induced., Life-threatening pulmonary influenza can be caused by inborn errors of type I and III IFN immunity. We report a 5-yr-old child with severe pulmonary influenza at 2 yr. She is homozygous for a loss-of-function IRF9 allele. Her cells activate gamma-activated factor (GAF) STAT1 homodimers but not IFN-stimulated gene factor 3 (ISGF3) trimers (STAT1/STAT2/IRF9) in response to IFN-α2b. The transcriptome induced by IFN-α2b in the patient’s cells is much narrower than that of control cells; however, induction of a subset of IFN-stimulated gene transcripts remains detectable. In vitro, the patient’s cells do not control three respiratory viruses, influenza A virus (IAV), parainfluenza virus (PIV), and respiratory syncytial virus (RSV). These phenotypes are rescued by wild-type IRF9, whereas silencing IRF9 expression in control cells increases viral replication. However, the child has controlled various common viruses in vivo, including respiratory viruses other than IAV. Our findings show that human IRF9- and ISGF3-dependent type I and III IFN responsive pathways are essential for controlling IAV.

The pathogenesis of Whipple’s disease (WD) remains largely unknown, as WD strikes only a very small minority of the individuals infected with Tropheryma whipplei (Tw). Asymptomatic carriage of Tw is less rare. We studied a large multiplex French kindred, containing four otherwise healthy WD patients (mean age: 76.7 years) and five healthy carriers of Tw (mean age: 55 years). We used a strategy combining genome-wide linkage analysis and whole-exome sequencing to test the hypothesis that WD is inherited in an autosomal dominant (AD) manner, with age-dependent incomplete penetrance. WD was linked to 12 genomic regions covering 27 megabases in the four patients. These regions contained only one very rare non-synonymous variation: the R98W variant of IRF4. The five Tw carriers were heterozygous for R98W. Interferon regulatory factor 4 (IRF4) is a transcription factor with pleiotropic roles in immunity. We showed that R98W was a loss-of-function allele, like only five other exceedingly rare IRF4 alleles of a total of 39 rare and common non-synonymous alleles tested. Furthermore, heterozygosity for R98W led to a distinctive pattern of transcription in leukocytes following stimulation with BCG or Tw. Finally, we found that IRF4 had evolved under purifying selection and that R98W was not dominant-negative, suggesting that the IRF4 deficiency in this kindred was due to haploinsufficiency. Overall, haploinsufficiency at the IRF4 locus selectively underlies WD in this multiplex kindred. This deficiency displays AD inheritance with incomplete penetrance, and chronic carriage probably precedes WD by several decades in Tw-infected heterozygotes.

Background Monthly injections of palivizumab during the respiratory syncytial virus (RSV) season in at-risk infants reduces RSV-associated hospitalizations. However, the additive effect of naturally acquired immunity remains unclear. The objective of this study was to assess total neutralizing serum antibodies (NAb) against RSV in at-risk infants who had received an abbreviated course of palivizumab prophylaxis. Methods Serum samples were collected from infants enrolled in the RSV Immunoprophylaxis Program in British Columbia, Canada over 2 consecutive RSV seasons (2013 to 2015). Infants in this program had received an abbreviated course of palivizumab in accordance with the provincial guidelines. Data were compared to adults and infants less than 12 months of age who did not receive palivizumab. Anti-RSV NAb titers were measured using an RSV microneutralization assay. Findings Infants who received palivizumab had anti-RSV NAb titers at the end of the RSV season that persisted beyond what is expected from the pharmacokinetics of palivizumab alone. Moreover, 54% of the control infants who did not receive palivizumab and all tested adults had protective anti-RSV NAb titers. Conclusions Based on our observations, we hypothesize that naturally acquired NAb provide additive protection, which may significantly reduce the need for additional doses of palivizumab in infants at risk of severe RSV infections.

Most members of the Toll-like receptor (TLR) and interleukin-1 receptor (IL-1R) families transduce signals via a canonical pathway involving the MyD88 adapter and the interleukin-1 receptor-associated kinase (IRAK) complex. This complex contains four molecules, including at least two (IRAK-1 and IRAK-4) active kinases. In mice and humans, deficiencies of IRAK-4 or MyD88 abolish most TLR (except for TLR3 and some TLR4) and IL-1R signaling in both leukocytes and fibroblasts. TLR and IL-1R responses are weak but not abolished in mice lacking IRAK-1, whereas the role of IRAK-1 in humans remains unclear. We describe here a boy with X-linked MECP2 deficiency-related syndrome due to a large de novo Xq28 chromosomal deletion encompassing both MECP2 and IRAK1. Like many boys with MECP2 null mutations, this child died very early, at the age of 7 mo. Unlike most IRAK-4– or MyD88-deficient patients, he did not suffer from invasive bacterial diseases during his short life. The IRAK-1 protein was completely absent from the patient’s fibroblasts, which responded very poorly to all TLR2/6 (PAM2CSK4, LTA, FSL-1), TLR1/2 (PAM3CSK4), and TLR4 (LPS, MPLA) agonists tested but had almost unimpaired responses to IL-1β. By contrast, the patient’s peripheral blood mononuclear cells responded normally to all TLR1/2, TLR2/6, TLR4, TLR7, and TLR8 (R848) agonists tested, and to IL-1β. The death of this child precluded long-term evaluations of the clinical consequences of inherited IRAK-1 deficiency. However, these findings suggest that human IRAK-1 is essential downstream from TLRs but not IL-1Rs in fibroblasts, whereas it plays a redundant role downstream from both TLRs and IL-1Rs in leukocytes.

Background: Preterm neonates are highly vulnerable to infection. Objectives: To investigate the developmental contribution of prematurity, chorioamnionitis and antenatal corticosteroids (ANS) on the maturation of neonatal microbial pathogen recognition responses. Methods: Using standardized protocols, we assayed multiple inflammatory cytokine responses (IL-1β, IL-6, TNF-α and IL-12/23p40) to three prototypic Toll-like receptor (TLR) agonists, i.e. TLR4 (lipopolysaccharide), TLR5 (flagellin) and TLR7/8 (R848), and to the non-TLR retinoic acid-inducible gene I (RIG-I)-like receptor agonist, in cord blood mononuclear cells from neonates born before 33 weeks of gestation and at term. Results: TLR responses develop asynchronously in preterm neonates, whereby responses to TLR7/8 were more mature and were followed by the development of TLR4 responses, which were also heterogeneous. Responses to TLR5 were weakest and most immature. Maturity in TLR responses was not influenced by sex. Overall, we detected no significant contribution of ANS and chorioamnionitis to the developmental attenuation of either TLR or RIG-I responses. Conclusions: The maturation of anti-microbial responses in neonates born early in gestation follows an asynchronous developmental hierarchy independently of an exposure to chorioamnionitis and ANS. Our data provide an immunological basis for the predominance of specific microbial infections in this age group.

Respiratory diseases are the most frequent chronic illnesses in babies and children. Although a vigorous innate immune system is critical for maintaining lung health, a balanced response is essential to minimize damaging inflammation. We investigated the functional and clinical impact of human genetic variants in the promoter of NFKBIA, which encodes IκBα, the major negative regulator of NF-κB. In this study, we quantified the functional impact of NFKBIA promoter polymorphisms (rs3138053, rs2233406, and rs2233409) on promoter-driven protein expression, allele-specific and total NFKBIA mRNA expression, IκBα protein expression, and TLR responsiveness; mapped innate immune regulatory networks active during respiratory syncytial virus infection, asthma, and bronchopulmonary dysplasia; and genotyped and analyzed independent cohorts of children with respiratory syncytial virus infection, asthma, and bronchopulmonary dysplasia. Genetic variants in the promoter of NFKBIA influenced NFKBIA gene expression, IκBα protein expression, and TLR-mediated inflammatory responses. Using a systems biology approach, we demonstrated that NFKBIA/IκBα is a central hub in transcriptional responses of prevalent childhood lung diseases, including respiratory syncytial virus infection, asthma, and bronchopulmonary dysplasia. Finally, by examining independent pediatric lung disease cohorts, we established that this immunologically relevant genetic variation in the promoter of NFKBIA is associated with differential susceptibility to severe bronchiolitis following infection with respiratory syncytial virus, airway hyperresponsiveness, and severe bronchopulmonary dysplasia. These data highlight the importance of negative innate immune regulators, such as NFKBIA, in pediatric lung disease and begin to unravel common aspects in the genetic predisposition to bronchopulmonary dysplasia, bronchiolitis, and childhood asthma.

International audience; Lipopolysaccharides (LPS) of Bordetella pertussis are important modulators of the immune system. Interaction of the lipid A region of LPS with the Toll-like receptor 4 (TLR4) complex causes dimerization of TLR4 and activation of downstream nuclear factor κB (NFκB), which can lead to inflammation. We have previously shown that two strains of B. pertussis, BP338 (a Tohama I-derivative) and 18-323, display two differences in lipid A structure. 1) BP338 can modify the 1- and 4'-phosphates by the addition of glucosamine (GlcN), whereas 18-323 cannot, and 2) the C3' acyl chain in BP338 is 14 carbons long, but only 10 or 12 carbons long in 18-323. In addition, BP338 lipid A can activate TLR4 to a greater extent than 18-323 lipid A. Here we set out to determine the genetic reasons for the differences in these lipid A structures and the contribution of each structural difference to the ability of lipid A to activate TLR4. We show that three genes of the lipid A GlcN modification (Lgm) locus, lgmA, lgmB, and lgmC (previously locus tags BP0399-BP0397), are required for GlcN modification and a single amino acid difference in LpxA is responsible for the difference in C3' acyl chain length. Furthermore, by introducing lipid A-modifying genes into 18-323 to generate isogenic strains with varying penta-acyl lipid A structures, we determined that both modifications increase TLR4 activation, although the GlcN modification plays a dominant role. These results shed light on how TLR4 may interact with penta-acyl lipid A species.

RSV reinfection increases IL-4Rα expression on T helper cells, responsible for the enhanced immunopathologies in mice initially infected as neonates. RSV is the major cause of severe bronchiolitis in infants, and severe bronchiolitis as a result of RSV is associated with subsequent asthma development. A biased Th2 immune response is thought to be responsible for neonatal RSV pathogenesis; however, molecular mechanisms remain elusive. Our data demonstrate, for the first time, that IL-4Rα is up-regulated in vitro on human CD4+ T cells from cord blood following RSV stimulation and in vivo on mouse pulmonary CD4+ T cells upon reinfection of mice, initially infected as neonates. Th cell-specific deletion of Il4ra attenuated Th2 responses and abolished the immunopathophysiology upon reinfection, including airway hyper-reactivity, eosinophilia, and mucus hyperproduction in mice infected initially as neonates. These findings support a pathogenic role for IL-4Rα on Th cells following RSV reinfection of mice initially infected as neonates; more importantly, our data from human cells suggest that the same mechanism occurs in humans.

TLRs play a key role in innate immune defenses. It was previously reported that purified respiratory syncytial virus (RSV) fusion protein elicits an inflammatory response in hematopoietic cells, which required expression of TLR4 and its co-receptor CD14. However, a biological role of TLR4 in immunity to RSV, as initially proposed, has remained inconclusive and controversial. Here, we directly assess the role of human TLR4 and its co-receptors in NF-κB activation, viral entry and replication using intact virions rather than purified RSV components. We used HEK 293 reporter cells that are highly permissive for RSV and that either express or a lack a functional human TLR4/MD-2/CD14 complex. We demonstrate that RSV-mediated NF-κB activation, viral entry and replication are independent of the expression of a functional human TLR4/MD-2/CD14 complex and that, in turn, human TLR4 activation by LPS remains unaffected in RSV-infected cells. Thus, although isolated viral compounds such as purified RSV F protein may bind TLR4 and/or CD14, a direct interaction between intact RSV particles and the human TLR4 receptor complex does not seem to play a biological role in RSV pathogenesis.

Bordetella pertussis endotoxin is a key modulator of the host immune response, mainly due to the role of its lipid A moiety in Toll-like receptor 4 (TLR4)-mediated signaling. We have previously demonstrated that the lipid A phosphate groups of B. pertussis BP338 can be substituted with glucosamine in a BvgAS-regulated manner. Here we examined the effect of this lipid A modification on the biological activity of B. pertussis endotoxin. We compared purified endotoxin and heat-killed B. pertussis BP338 whole cells that have modified lipid A phosphate groups to an isogenic mutant lacking this modification with respect to their capacities to induce the release of inflammatory cytokines by human and murine macrophages and to participate in the TLR4-mediated activation of NF-κB in transfected HEK-293 cells. We found inactivated B. pertussis cells to be stronger inducers of proinflammatory cytokines in THP-1-derived macrophages when lipid A was modified. Most notably, lack of lipid A modification abolished the ability of purified B. pertussis endotoxin to induce the release of inflammatory cytokines by human THP-1-derived macrophages but led to only slightly reduced inflammatory cytokine levels when stimulating murine (RAW 264.7) macrophages. Accordingly, upon stimulation of HEK-293 cells with inactivated bacteria and purified endotoxin, lack of lipid A modification led to impaired NF-κB activation only when human, and not when murine, TLR4-MD-2-CD14 was expressed. We speculate that in B. pertussis , lipid A modification has evolved to benefit the bacteria during human infection by modulating immune defenses rather than to evade innate immune recognition.

C1 esterase inhibitor (C1inh) is a major inhibitor of several pathways of inflammation in humans. In this study, we show that virulent-phase cultures of Bordetella pertussis, the etiological agent for whooping cough, but not other Bordetella species specifically recruit C1inh from human serum. Using a spontaneous mutant of B. pertussis that was deficient in C1inh binding, we demonstrate that the ability of B. pertussis to acquire high levels of human C1inh and wild-type levels of serum resistance are well correlated, suggesting that, in addition to and independent of BrkA expression, acquisition of C1inh is vital to B. pertussis resistance to complement-mediated killing.

Newborn infants, including those born at term without congenital disorders, are at high risk of severe disease from respiratory syncytial virus (RSV) infection. Indeed, our current local surveillance data demonstrate that approximately half of children hospitalized with RSV were ≤3 mo old, and 74% were born at term. Informed by this clinical epidemiology, we investigated antiviral innate immune responses in early life, with the goal of identifying immunological factors underlying the susceptibility of infants and young children to severe viral lower respiratory tract infections. We compared RSV-induced innate cytokine production in blood mononuclear cells from neonates, young children aged 12–59 mo, and healthy adults. RSV-induced IFN-α production was primarily mediated by plasmacytoid dendritic cells (pDCs), and was significantly lower in term infants and young children < 5 y of age than in adults (p < 0.01). RSV-induced IFN-α production in human pDCs proceeded independently of endosomal TLRs, and human pDCs from healthy adult donors produced IFN-α in a retinoic acid–inducible gene I protein (RIG-I)–dependent manner. Of interest, young age and premature birth were independently associated with attenuated RIG-I–dependent IFN-α responses (p < 0.01). In contrast to IFN-α production, proinflammatory IL-6 responses to RSV were mediated by monocytes, appeared less dependent on RIG-I, and were significantly impaired only among preterm infants, not in term infants and young children. Our results suggest that human pDCs are less functional in early life, which may contribute to the increased susceptibility of infants and young children to severe RSV disease.

The majority of cases of severe pediatric respiratory syncytial virus (RSV) infection occur in otherwise healthy infants who have no identifiable risk factors, suggesting that additional subclinical factors, such as population genetic variation, influence the course of RSV infection. The objective of this study was to test if common single nucleotide polymorphisms (SNPs) in genes encoding for immune signalling components of the RIG-I-like receptor (RLR) and IL-4-signalling pathways affect the outcome of RSV infection in early life. We genotyped 8 SNPs using allele-specific probes combined with real-time PCR. Each of the SNPs tested had previously been established to have a functional impact on immune responsiveness and two of the SNPs in the IL4 and IL4R genes had previously been associated with severe RSV bronchiolitis. Association with susceptibility to severe RSV infection was tested by statistically comparing genotype and allele frequencies in infants and young children hospitalized with severe RSV bronchiolitis (n = 140) with two control groups-children who tested positive for RSV but did not require hospitalization (n = 100), and a general population control group (n = 285). Our study was designed with sufficient power (>80%) to detect clinically-relevant associations with effect sizes ≥1.5. However, we detected no statistically significant differences in allele and genotype frequencies of the investigated SNPs between the inpatient and control groups. To conclude, we could not replicate the previously reported association with SNPs in the IL4 and IL4R genes in our independent cohort, nor did we find that common SNPs in genes encoding for RLRs and the downstream adapter MAVS were associated with susceptibility to severe RSV infections. Despite the existing evidence demonstrating a functional immunological impact of these SNPs, our data suggest that the biological effect of each individual SNP is unlikely to affect clinical outcomes of RSV infection.

Compendia of large-scale datasets made available in public repositories provide an opportunity to identify and fill gaps in biomedical knowledge. But first, these data need to be made readily accessible to research investigators for interpretation. Here we make available a collection of transcriptome datasets to investigate the functional programming of human hematopoietic cells in early life. Thirty two datasets were retrieved from the NCBI Gene Expression Omnibus (GEO) and loaded in a custom web application called the Gene Expression Browser (GXB), which was designed for interactive query and visualization of integrated large-scale data. Quality control checks were performed. Multiple sample groupings and gene rank lists were created allowing users to reveal age-related differences in transcriptome profiles, changes in the gene expression of neonatal hematopoietic cells to a variety of immune stimulators and modulators, as well as during cell differentiation. Available demographic, clinical, and cell phenotypic information can be overlaid with the gene expression data and used to sort samples. Web links to customized graphical views can be generated and subsequently inserted in manuscripts to report novel findings. GXB also enables browsing of a single gene across projects, thereby providing new perspectives on age- and developmental stage-specific expression of a given gene across the human hematopoietic system. This dataset collection is available at: http://developmentalimmunology.gxbsidra.org/dm3/geneBrowser/list.

International audience; Bordetella endotoxins show remarkable structural variability both among each other and in comparison to other gram-negative bacteria. Here we demonstrate that, in contrast to the common Bordetella pertussis laboratory strain and Tohama I derivative BP338, lipooligosaccharide from mouse challenge strain 18-323 is a poor inducer of inflammatory cytokines in human and murine macrophages, is greatly impaired in Toll-like receptor 4-mediated activation of nuclear factor-κB in transfected HEK-293 cells, and functions as a Toll-like receptor 4 antagonist. Comparison of lipid A and lipooligosaccharide structures of B. pertussis strains BP338 and 18-323 revealed that 18-323 (1) lacks the ability to modify its lipid A phosphate groups with glucosamine, (2) is distinct in its acylation at the C3' position of the lipid A diglucosamine backbone, and (3) expresses molecular lipooligosaccharide species that lack a terminal heptose. Our findings have important implications for interpreting previous studies of host defenses to B. pertussis infection in mice and in vitro.

This study examined the vaccine potential of the autotransporter protein BrkA of Bordetella pertussis in the sublethal intranasal murine respiratory challenge model of infection. Five different acellular pertussis (Pa) vaccines, containing different pertussis-component antigens but all comprizing diphtheria (D) and tetanus (T) toxoids, were tested. A two-pertussis-component DTPa vaccine containing pertussis toxoid (PT) and filamentous hemagglutinin (FHA) induced only limited bacterial clearance. However, a three-pertussis-component DTPa vaccine containing PT, FHA and a recombinant BrkA protein (rBrkA) was found to be as efficacious in protecting mice against colonization by B. pertussis strains Tohama I and 18-323 as the commercial Infanrixtrade mark vaccine that also includes PT and FHA but pertactin (PRN) instead of rBrkA. Vaccination of mice with rBrkA as the only B. pertussis antigen did not protect against colonization by B. pertussis. We also demonstrated that BrkA is ubiquitously expressed by highly prevalent clinical isolates of B. pertussis and suggest that new acellular pertussis vaccine formulations that include BrkA have equivalent efficacy as currently available DTPa vaccines against B. pertussis infections.

Endotoxins are amphipathic lipopolysaccharides (LPSs), major constituents of the outer membrane of gram-negative bacteria. They consist of a lipid region, covalently linked to a core oligosaccharide, to which may be linked a repetitive glycosidic chain carrying antigenic determinants. Most of the biological activities of endotoxins have been associated with the lipid moiety of the molecule: unique to gram-negative bacteria, LPS is a ligand of the mammalian TLR4-MD2-CD14 pathogen recognition receptor complex. Lipid A preparations are often heterogeneous with respect to both the numbers and the lengths of fatty acids and the natures of substituents on the phosphate groups when present. The variants can significantly affect host immune responses. Nine species in theBordetellagenus have been described, and the fine LPS structures of seven of them have been published. In this report, lipids A fromBordetella pertussisTohama I andB. bronchisepticastrain 4650 were further characterized and revealed to have a glucosamine substituting both lipid A phosphate groups of the diglucosamine backbone. These substitutions have not been previously described for bordetellae. Moreover, aB. pertussistransposon mutation that maps within a gene encoding aBordetellaArnT (formerly PmrK) glycosyl transferase ortholog does not carry this substitution, thus providing a genetic basis for the modification. Reverse transcriptase PCR of this locus showed that it is Bvg regulated, suggesting that the ability ofBordetellato modify lipid A via this glucosamine modification is a potential virulence trait.

Background Respiratory syncytial virus (RSV) causes severe respiratory tract infections, which might have a role in the development of airway hyperreactivity. Mast cells are important effector cells in allergy, with sentinel cell roles in host defense. However, the role of mast cells in response to RSV infection is unknown. Objective Human mast cell responses to RSV were investigated with a view to better understanding the role of mast cells in RSV-induced disease. Methods Human cord blood–derived mast cells and the HMC-1 mast cell line were exposed to RSV or UV-inactivated RSV. Viral gene and protein expression were evaluated by using PCR and flow cytometry. The expression of interferon-stimulated genes and selected mediators were evaluated by using quantitative PCR and ELISA. Results Human mast cells expressed multiple RSV genes after exposure to RSV, and a small percentage of mast cells supported RSV antigen protein expression. RSV induced mast cells to upregulate production of chemokines, including CCL4, CCL5, and CXCL10, as well as type I interferons, and interferon-stimulated gene expression. However, production of the granulocyte chemoattractants CXCL8 and CCL11 was not induced. Antibody blockade of the type I interferon receptor on human cord blood–derived mast cells reduced the RSV-mediated induction of CXCL10 and CCL4 but not CCL5. Leukotriene C 4 production by mast cells was not enhanced by exposure to RSV. Conclusion Despite low levels of infection, human mast cells produce multiple chemokines in response to RSV through mechanisms that include responses to type I interferons. Such mast cell responses might enhance effector cell recruitment during RSV-induced disease.

Bordetella pertussis employs numerous strategies to evade the immune system, including the ability to resist killing via complement. Previously we have shown that B. pertussis binds a complement regulatory protein, C1 esterase inhibitor (C1inh) to its surface in a Bvg-regulated manner (i.e. during its virulence phase), but the B. pertussis factor was not identified. Here we set out to identify the B. pertussis C1inh-binding factor. Using a serum overlay assay, we found that this factor migrates at approximately 100 kDa on an SDS-PAGE gel. To identify this factor, we isolated proteins of approximately 100 kDa from wild type strain BP338 and from BP347, an isogenic Bvg mutant that does not bind C1inh. Using mass spectrometry and bioinformatics, we identified the autotransporter protein Vag8 as the putative C1inh binding protein. To prove that Vag8 binds C1inh, vag8 was disrupted in two different B. pertussis strains, namely BP338 and 18–323, and the mutants were tested for their ability to bind C1inh in a surface-binding assay. Neither mutant strain was capable of binding C1inh, whereas a complemented strain successfully bound C1inh. In addition, the passenger domain of Vag8 was expressed and purified as a histidine-tagged fusion protein and tested for C1inh-binding in an ELISA assay. Whereas the purified Vag8 passenger bound C1inh, the passenger domain of BrkA (a related autotransporter protein) failed to do so. Finally, serum assays were conducted to compare wild type and vag8 mutants. We determined that vag8 mutants from both strains were more susceptible to killing compared to their isogenic wild type counterparts. In conclusion, we have discovered a novel role for the previously uncharacterized protein Vag8 in the immune evasion of B. pertussis. Vag8 binds C1inh to the surface of the bacterium and confers serum resistance.