Immune Complexes Research Articles

Complement activation by IgG subclasses is governed by their ability to oligomerize upon antigen binding.

Complement activation through antibody-antigen complexes is crucial in various pathophysiological processes and utilized in immunotherapies to eliminate infectious agents, regulatory immune cells, or cancer cells. The tertiary structures of the four IgG antibody subclasses are largely comparable, with the most prominent difference being the hinge regions connecting the Fab and Fc domains, providing them with unique structural flexibility. Complement recruitment and activation depend strongly on IgG subclass, which is commonly rationalized by differences in hinge flexibility and the respective affinities for C1, the first component of the classical complement pathway. However, a unifying mechanism of how these different IgG subclass properties combine to modulate C1 activation has not yet been proposed. We here demonstrate that complement activation is determined by their varying ability to form IgG oligomers on antigenic surfaces large enough to multivalently bind and activate C1. We directly visualize the resulting IgG oligomer structures and characterize their distribution by means of high-speed atomic force microscopy, quantify their complement recruitment efficiency from quartz crystal microbalance experiments, and characterize their ability to activate complement on tumor cell lines as well as in vesicle-based complement lysis assays. We present a mechanistic model of the multivalent interactions that govern C1 binding to IgG oligomers and use it to extract kinetic rate constants from real-time interaction data from which we further calculate equilibrium dissociation constants. Together, we provide a comprehensive view on the parameters that govern complement activation by the different IgG subclasses, which may inform the design of future antibody therapies.

Protein phosphatase 1 suppresses PKR/EIF2α signaling during human cytomegalovirus infection.

Human cytomegalovirus (HCMV) is a ubiquitous pathogen that infects the majority of the world's population. Lytic HCMV replication in immunocompromised individuals or neonates can lead to severe disease in multiple organ systems and even death. The establishment of lytic replication is driven by the first viral proteins expressed upon infection, the immediate early proteins, which play a key role in creating an intracellular environment conducive to virus replication. Two immediate early proteins, the functional orthologs pTRS1 and pIRS1, stimulate immediate early gene expression by suppressing antiviral PKR/eIF2α signaling and enhance the translation of viral mRNAs independent of PKR antagonism. To better understand the molecular functions of pTRS1, we used proximity labeling proteomics to identify proteins that interact with pTRS1 in infected cells. Multiple novel host and viral interactors were identified, including the catalytic subunits of the protein phosphatase 1 (PP1) holoenzyme. Mutations to a PP1 catalytic subunit known to disrupt binding to PP1 regulatory subunits decreased binding to pTRS1. pTRS1 immune complexes contained phosphatase activity, and inhibition of phosphatase activity in transfected or infected cells reversed the ability of pTRS1 to inhibit the antiviral kinase PKR. Depletion of individual PP1 catalytic subunits decreased virus replication and increased the phosphorylation of the PKR substrate eIF2α. Taken together, our data suggest potential novel functions for pTRS1 and define a novel role for PP1 as an antagonist of the antiviral PKR/eIF2α signaling axis during HCMV infection.IMPORTANCEThe human cytomegalovirus (HCMV) pTRS1 and pIRS1 proteins are critical regulators of HCMV replication, both during primary infection and during reactivation from viral latency. Thus, defining the molecular functions of pTRS1/pIRS1 is important for understanding the molecular events controlling HCMV replication and viral disease. These data provide new insights into potential pTRS1 functional roles, providing a starting point for others to understand new features of infected cell biology. Another important result of this study is the finding that specific protein phosphatase 1 (PP1) regulatory subunits are required to suppress PKR/eIF2α signaling, a critical cellular innate immune defense to viral infection. These data lay the groundwork for future efforts to discover therapeutics that disrupt pTRS1 interaction with PP1 allowing cellular defenses to limit HCMV replication and disease.

Increased risk of stroke in non-rheumatic valvular disease associated with antiphospholipid syndrome (APS): a US nationwide study 2017-2019

Abstract Introduction Antiphospholipid syndrome (APS) is an autoimmune syndrome characterized by the presence of antiphospholipid autoantibodies, arterial and venous thrombosis, recurrent pregnancy loss and thrombocytopenia. Cardiac manifestations are also common which include coronary artery disease (CAD), non rheumatic valvular heart disorders (NRVHD), myocardial dysfunction, intracardiac thrombi and pulmonary hypertension. Valvular lesions occur likely due to immune complex deposition on the valves, causing fibrosis, calcification and subsequently valvular deformities. Literature review suggests prevalence of NRVHD in APS population is 30% and left sided valves are more involved than right. An increased risk of stroke has also been seen in APS patients with valvular disorders. Purpose Studies report variations in incidence of NRVHD in association with APS. To estimate the prevalence of NRVHD and their correlation with APS, we conducted a retrospective database analysis of hospitalizations across the United States. Additionally we investigated whether this association indicates a increased risk of ischemic stroke in this specific subpopulation. Methods The national inpatient sample (NIS) from 2017-2019 was queried for adult patients (age>18 yrs) admitted with a primary or secondary diagnosis of APS. These patients were stratified for different NRVHD including tricuspid stenosis, tricuspid insufficiency, pulmonary stenosis, pulmonary regurgitation, mitral stenosis, mitral insufficiency (MI), aortic stenosis (AS), and aortic regurgitation. Baseline risk factors and cardiac complications were compared. Multiple regression analysis was performed to study the association of NRVHD with stroke as the primary outcome in the subpopulation of APS hospitalizations. Results A total of 567600 adult patients hospitalized with diagnosis of APS were identified from the NIS 2017-2019 database. Among those, 33,095 had NRVHD with a mean age of 69 years. Of these, prevalence of males was 52.41% compared to females of 47.59%. In the cohort of APS, patients with NRVHD had a higher prevalence of coronary artery disease (43.78% vs 20.41%), diabetes mellitus (30.65% vs 27.56%), prior stroke (10.42% vs 7.78%) than those without valvular disorders. Among the APS population the most prevalent NRVHD were mitral insufficiency (MI), 2.45% and aortic stenosis (AS), 2.13%. In the cohort of NRVHD in APS hospitalizations, the odds of stroke was found to be 1.3 times higher with statistical significance (confidence interval (CI): 1.13-1.48, p <0.001) adjusted for relevant clinical and demographic risk factors such as tobacco abuse, CAD, diabetes mellitus, prior stroke. Conclusion This study shows 6.2% prevalence of NRVHD in APS population, of which MI and AS were common. NRVHD is also associated with higher odds of stroke in APS. Further studies are warranted in identifying the risk of stroke with NRVHD in APS population and emphasizing the need for early detection.

Involvement of Complement in Alzheimer's Disease: From Genetics Through Pathology to Therapeutic Strategies.

Complement is a critical component of innate immunity, evolved to defend against pathogens and clear toxic debris rangingfrom dead and dying cells to immune complexes. These roles make complement a key player in homeostasis; however, complement has a dark side. When the rigid control mechanisms fail, complement becomes dysregulated, acting as a driver of inflammation and resultant pathology in numerous diseases. Roles of complement in Alzheimer's disease (AD) and other dementias have emerged in recent years, supported by genetic, biomarker and pathological evidence and animal model studies. Numerous questions remain regarding the precise roles of complement in the brain in health and disease, including where and when complement is expressed, how it contributes to immune defence and garbage disposal in the healthy brain, and exactly how complement contributes to pathology in dementias. In this brief review, we will summarise current knowledge on complement roles in brain, present the evidence implicating complement in AD and explore whether complement represents an attractive therapeutic target for AD.

Immuno-RCA for highly sensitive detection of the antigen-antibody complex in the blood group antigen model

The problem of detecting tiny quantities of analytes by immunochemical methods has been tried for a long time. One approach is to use nucleic acid amplification methods to amplify the signal from a single antigen-antibody interaction. An amplification method suitable for microarrays is the rolling circle amplification reaction. The principle of the method is usage of a conjugate of a detecting antibody with a primer and subsequent isothermal amplification. The generation of a huge single-stranded reaction product starts after adding the necessary components for amplification reaction: circular oligonucleotides, which serves as a template for amplification and phage phi29 polymerase with the other components. This reaction product consists of a lot of repeats of a nucleotide sequence, that is complementary to the circular template. The fluorescent DNA probe can hybridize to each repeat on the product molecule, resulting in a significantly higher level of fluorescence than with fluorescently labeled antibody or streptavidin development systems. In addition, the reaction product remains immobilized on the surface, allowing usage of this approach for the detection of antigen-antibody interactions in other solid-phase analysis systems, such as microarrays. A common problem with such approaches is the nonspecific sorption of components of the immunochemical reaction or amplification reaction, leading to a high background. It is obvious that no matter how highly sensitive the analysis is in theory, a high background will reduce the entire potential of the method to nothing. Herein, we have developed a method that makes it possible to detect small amounts of antibodies to glycans in blood serum and in swabs from tumor cells in a microarray format using a model of blood group antigens. It was possible to obtain a 30 to 70-fold increase of fluorescence level from a specific interaction compared to the use of fluorescently labeled streptavidin. The method we are developing is promising, as it allows us to significantly increase the signal from the specific antigen/antibody interaction in the glycochip format, which will make it possible to detect antibodies to glycans in samples with a very low concentrations of antibodies, for example, in washes from tumor cells.

Lessons from IgA Nephropathy Models

IgA nephropathy (IgAN) is the most common type of primary glomerulonephritis worldwide; however, the underlying mechanisms of this disease are not fully understood. This review explores several animal models that provide insights into IgAN pathogenesis, emphasizing the roles of aberrant IgA1 glycosylation and immune complex formation. It discusses spontaneous, immunization, and transgenic models illustrating unique aspects of IgAN development and progression. The animal models, represented by the grouped ddY (gddY) mouse, have provided guidance concerning the multi-hit pathogenesis of IgAN. In this paradigm, genetic and environmental factors, including the dysregulation of the mucosal immune system, lead to increased levels of aberrantly glycosylated IgA, nephritogenic immune complex formation, and subsequent glomerular deposition, followed by mesangial cell activation and injury. Additionally, this review considers the implications of clinical trials targeting molecular pathways influenced by IgAN (e.g., a proliferation-inducing ligand [APRIL]). Collectively, these animal models have expanded the understanding of IgAN pathogenesis while facilitating the development of therapeutic strategies that are currently under clinical investigation. Animal-model-based studies have the potential to facilitate the development of targeted therapies with reduced side effects for IgAN patients.

Lipschütz ulcer following first dose of COVID-19 tozinameran vaccine: Report of a case and review of a World Health Organization pharmacovigilance database.

Lipschütz ulcer (LU) is a condition known for painful vulvar ulcers, typically affecting young women and often linked to infectious agents. Recent reports have indicated a potential connection between LU and COVID-19 vaccination, particularly after the second or booster doses. This study presents a case of LU following the first dose of tozinameran in a young woman who had a previous SARS-CoV-2 infection and investigates similar cases globally. An 18-year-old woman experienced vulvar pain and ulcers 2-days after her initial COVID-19 vaccine dose. After ruling out infections through serological tests, a diagnosis of LU was made, and her symptoms resolved after 10 days. A literature search and VigiBase® analysis revealed 11 cases of LU following COVID-19 vaccination, and 519 vulvovaginal ulcer cases associated with these vaccines were identified in Vigibase®, with a median onset of 2 days. Most LU cases occurred after the second dose or booster shots. The primary hypothesis for this association is a type 3 hypersensitivity reaction mediated by immune complexes, possibly triggered by prior exposure, as many cases occurred after the second dose. Interestingly, the presented case suggests that prior COVID-19 infection could serve as sensitization. In conclusion, this study highlights the potential occurrence of LU after the initial COVID-19 vaccine dose in young patients with prior COVID-19 infection. While the risk of recurrence after subsequent vaccinations or infections remains uncertain, the benefits of vaccination outweigh the risks. Clinicians and patients should be aware of this potential issue to make informed decisions regarding vaccination.

Gastrointestinal manifestations and pathogenesis in childhood immunoglobulin A vasculitis

Immunoglobulin A vasculitis (IgAV), previously known as Henoch-Schönlein purpura, is the most common form of systemic vasculitis in childhood. The primary organs involved are the skin, gastrointestinal (GI) tract, joints, and kidneys. The spectrum of GI involvement in IgAV ranges from being mild and self-limited to severe manifestations often requiring surgical intervention. Galactose-deficient IgA1 on the immunoglobulin hinge region and its immune complexes are thought to play a central pathogenetic role in IgAV, however, an association between such molecules and specific GI mucosal damage remains unclear. GI endoscopy (both upper and lower) shows a variety of mucosal findings, many of which are not specific for IgAV. In upper GI endoscopy, however, the mucosal features can be diagnostic when found localized in the more distal part of upper GI tract (second and/or third parts of the duodenum). Abdominal computed tomography and capsule endoscopy have demonstrated that the small intestine is most commonly involved in IgAV. The GI mucosal involvement when evaluated microscopically shows IgA deposition which is histologically diagnostic. Conversely, leukocytoclastic vasculitis is less useful. Since the 1960s, cases of duodenojejunitis, in which IgAV was suspected but evident purpura was not dermatologically present, have often been labeled as “idiopathic”. In a pediatric case series, IgA enteropathy, without dermatological manifestations (i.e., purpura), was reported to have similar symptoms, as well as endoscopic characteristics and immunohistological findings as in IgAV. Subsequently, several case reports provide additional supportive evidence that IgA enteropathy must be a variant of IgAV. Thus, the immunologically driven auto-immune vasculitis results in the symptom complex dependent on the organ system involved, and the subsequent clinical features which are manifested. Present classification criteria are useful and universally available for diagnosing IgAV. However, based upon current knowledge including IgA enteropathy, minor modification of the IgAV criteria is proposed in the review.

Amyloid-β (Aβ) immunotherapy induced microhemorrhages are linked to vascular inflammation and cerebrovascular damage in a mouse model of Alzheimer’s disease

BackgroundAnti-amyloid-β (Aβ) immunotherapy trials have revealed amyloid-related imaging abnormalities (ARIA) as the most prevalent and serious adverse events linked to pathological changes in cerebral vasculature. Recent studies underscore the critical involvement of perivascular macrophages and the infiltration of peripheral immune cells in regulating cerebrovascular damage. Specifically, Aβ antibodies engaged at cerebral amyloid angiopathy (CAA) deposits trigger perivascular macrophage activation and the upregulation of genes associated with vascular permeability. Nevertheless, further research is needed to understand the immediate downstream consequences of macrophage activation, potentially exacerbating CAA-related vascular permeability and microhemorrhages linked to Aβ immunotherapy.MethodsThis study investigates immune responses induced by amyloid-targeting antibodies and CAA-induced microhemorrhages using RNA in situ hybridization, histology and digital spatial profiling in an Alzheimer's disease (AD) mouse model of microhemorrhage.ResultsIn the present study, we have demonstrated that bapineuzumab murine surrogate (3D6) induces profound vascular damage, leading to smooth muscle cell loss and blood–brain barrier (BBB) breakdown. In addition, digital spatial profiling (DSP) reveals that distinct immune responses contribute to vascular damage with peripheral immune responses and perivascular macrophage activation linked to smooth muscle cell loss and vascular fibrosis, respectively. Finally, RNA in situ hybridization identifies two distinct subsets of Trem2+ macrophages representing tissue-resident and monocyte-derived macrophages around vascular amyloid deposits. Overall, these findings highlight multifaceted roles of immune activation and vascular damage in driving the development of microhemorrhage.ConclusionsIn summary, our study has established a significant link between CAA-Aβ antibody immune complex formation, immune activation and vascular damage leading to smooth muscle cell loss. However, the full implications of this cascade on the development of microhemorrhages requires further exploration. Additional investigations are warranted to unravel the precise molecular mechanisms leading to microhemorrhage, the interplay of diverse immune populations and the functional roles played by various Trem2+ macrophage populations in response to Aβ immunotherapy.

Rare connective tissue diseases in patients with C1-inhibitor deficiency hereditary angioedema: first evidence on prevalence and distribution from a large Italian cohort study

IntroductionIn patients with Hereditary Angioedema (HAE) related to primary C1 inhibitor deficiency (C1INH), the defective clearance of immune complexes and apoptotic materials along with impairment of normal humoral response potentially leads to autoimmunity. Few studies report evidence on autoimmune diseases in C1INH-HAE, but no large population studies focus on rare connective tissue diseases (RCTDs). We aim at evaluating for the first time prevalence and distribution of RCTDs - Systemic Lupus Erytematosus (SLE), primary Sjogren Syndrome (SjS), primary antiphospholipid syndrome (APS), Systemic Sclerosis (SSc), and mixed connective tissue diseases (MCTD) in a large Italian cohort of C1INH-HAE patients.MethodsA multicenter observational study includes C1INH-HAE patients from ITACA Centers throughout Italy (time frame Sept 2023-March 2024). Inclusion criteria are i. a defined diagnosis of type I or type II C1INH-HAE; ii. age ≥15 years (puberty already occurred); iii. enrollment in the ITACA Registry. The diagnosis of SLE, primary SjS, primary APS, SSc, and MCTD are made in accordance with international classification criteria.ResultsData are collected from a total of 855 C1INH-HAE patients referring to 15 ITACA Centers. Patients with concomitant RCTDs were 18/855 (2.1%) with F:M ratio 3.5 and a prevalent type I C1INH-HAE diagnosis (87.2%). A diagnosis of SLE results in 44.5% of cases (n=8) while the remaining diagnoses are primary SjS (22.2%, n=4), primary APS (16.6%, n=3), SSc (11.2%, n=2), and a single case of MCTD (5.5%). The female gender is prevalent in all the RCTDs. Patients on long term prophylaxis (LTP) are significantly prevalent in RCTDs group than in the whole C1INH-HAE population (p<0.01).ConclusionsA relevant prevalence of RCTDs is documented in C1INH-HAE patients, mainly SLE. Patients with RCTDs are on LTP in a significant proportion supporting the idea of a bidirectional link between C1INH-HAE and autoimmunity.

Semisynthetic Phage Display Library Construction: Design and Synthesis of Diversified Single-Chain Variable Fragments and Generation of Primary Libraries.

Display of antibody fragments on the surface of M13 filamentous bacteriophages is a well-established approach for the identification of antibodies binding to a target of interest. Here, we describe the first of a three-step method to construct Antibody Libraries for Therapeutic Antibody Discovery (ALTHEA) Libraries. The three-step method involves (1) primary library (PL) construction, (2) filtered library construction, and (3) secondary library construction. The first step, described here, entails design, synthesis, and cloning of four PLs. These PLs are designed with specific properties amenable to therapeutic antibody development using one universal variable heavy (VH) scaffold and four distinct variable light (VL) scaffolds. The scaffolds are diversified in positions that bind both protein and peptide targets identified in antibody-antigen complexes of known structure using the amino acid frequencies found in those positions in known human antibody sequences, avoiding residues that may lead to developability liabilities. The diversified scaffolds are combined with 90 synthetic neutral HCDR3 sequences designed with developable human diversity genes (IGHD) and joining heavy genes (IGHJ) in germline configuration, and assembled as single-chain variable fragments (scFvs) in a VL-linker-VH orientation. The four designed PLs are synthesized using trinucleotide phosphoramidites (TRIMs) and cloned independently into a phagemid vector for M13 pIII display. Quality control of the cloning of the four PLs is also described, which involves sequencing scFvs in each library.

Integrative biomarker discovery and immune profiling for ulcerative colitis: a multi-methodological approach

Background We aimed to pinpoint biomarkers, create a diagnostic model for ulcerative colitis (UC), and delve into its immune features to better understand this autoimmune condition. Methods The sequencing data for both the UC and the control groups were obtained from GEO, including both bulk and single-cell data. Using GSE87466 as training group, we applied differential analysis, WGCNA, PPI, LASSO, RF, and SVM-RFE for biomarker selection. A neural network shaped our diagnostic model, corroborated by GSE92415 as the validation cohort with ROC assessment. Immune cell profiling was conducted using CIBERSORT. Results 53 disease-associated genes were screened. Enrichment analysis highlighted roles in complement cascades and cell adhesion. Eight biomarkers were finally identified through multiple machine learning and PPI: B4GALNT2, PDZK1IP1, FAM195A, REG4, MTMR11, FLJ35024, CD55, and CD44. The diagnostic model had AUCs of 0.984 (training group) and 0.957 (validation group). UC tissues revealed heightened plasma cells, CD8 T cells, and other immune cells. Two unique UC immune patterns emerged, with certain T and NK cells central to immune modulation. Conclusion We identified eight biomarkers of UC by various methods, constructed a diagnostic model through neural networks, and explored the immune complexity of the disease, which contributes to the diagnosis and treatment of UC.

Subcutaneous Sweet Syndrome With Vasculitis Features: Case Report and Review.

Subcutaneous Sweet Syndrome (SSS) is a rare variant of Sweet Syndrome characterized by neutrophilic infiltration of subcutaneous adipose tissue without vasculitis. The presence of vasculitis in SSS is uncommon and poses diagnostic challenges. A 38-year-old female presented with a one-year history of recurrent painful erythematous nodules on her limbs and face. Physical examination revealed asymmetrical erythematous patches and tender subcutaneous nodules with central necrotic eschars on the lower limbs. Laboratory tests were unremarkable except for a mildly elevated erythrocyte sedimentation rate. Histopathological analysis showed significant neutrophilic infiltration within the adipose lobules and vascular walls, along with extravasation of red blood cells, indicating vasculitis. The patient responded promptly to systemic corticosteroids; however, symptoms recurred upon tapering, necessitating ongoing steroid therapy. This case underscores the rare occurrence of vasculitis in SSS, expanding the histopathological spectrum of the disease. Literature review suggests that vasculitis in SSS may result from neutrophil-mediated vascular damage rather than immune complex deposition. The recurrent symptoms upon steroid tapering highlight the therapeutic challenges in managing SSS with vasculitis. Recognition of vasculitis in SSS is crucial for accurate diagnosis and effective management. Further research is warranted to elucidate the pathogenesis and develop targeted treatment strategies for SSS with vasculitis.

A mathematical model simulating the adaptive immune response in various vaccines and vaccination strategies

Vaccination has been widely recognized as an effective measure for preventing infectious diseases. To facilitate quantitative research into the activation of adaptive immune responses in the human body by vaccines, it is important to develop an appropriate mathematical model, which can provide valuable guidance for vaccine development. In this study, we constructed a novel mathematical model to simulate the dynamics of antibody levels following vaccination, based on principles from immunology. Our model offers a concise and accurate representation of the kinetics of antibody response. We conducted a comparative analysis of antibody dynamics within the body after administering several common vaccines, including traditional inactivated vaccines, mRNA vaccines, and future attenuated vaccines based on defective interfering viral particles (DVG). Our findings suggest that booster shots play a crucial role in enhancing Immunoglobulin G (IgG) antibody levels, and we provide a detailed discussion on the advantages and disadvantages of different vaccine types. From a mathematical standpoint, our model proposes four essential approaches to guide vaccine design: enhancing antigenic T-cell immunogenicity, directing the production of high-affinity antibodies, reducing the rate of IgG decay, and lowering the peak level of vaccine antigen-antibody complexes. Our study contributes to the understanding of vaccine design and its application by explaining various phenomena and providing guidance in comprehending the interactions between antibodies and antigens during the immune process.

Development of photoelectrochemical immunosensor based on halide perovskite protected by organometallic compounds for determining interleukin-17A (IL-17A).

The overexpression of interleukin-17A (IL-17A) is closely associated with the pathogenesis of autoimmune diseases and cancer, rendering precise identification of IL-17A level critical for disease diagnosis and prognosis monitoring. In this study, CsPbBr3 nanoclusters (NCs) were embedded in C16H14Br2O6Pb2 organometallic compound (Pb-MA MOC) via a hot injection approach. Through this way, the issue of CsPbBr3 NCs susceptible to decomposition in water was solved, and the photocurrent intensity that isgenerated by CsPbBr3 was significantly enhanced. A highly sensitive photoelectrochemical (PEC) sensor for detecting IL-17A in human serum was developed using CsPbBr3/Pb-MA as the photoactive material. The electrode was initially modified with CsPbBr3/Pb-MA. Then, antibody-modified Fe3O4 magnetic nanoparticles (MNs) with target analyte IL-17A captured, and IL-17A antibody-modified Au@CuNi diatomic catalyst (DAC) formed sandwich immune complex structure on theelectrode. The existence of CuNi DAC led to a substantial reduction in photoelectric signal intensity due to oxidation of ascorbic acid in thesupporting electrolyte. The photocurrent intensity exhibited linear correlation with IL-17A concentration within the range 15-750pg/mL, and achieving an impressive detection limit of1pg/mL. Moreover, the sensor was successfully applied to the determination of IL-17A in human serum, suggesting its potential clinical applications.

HEV ORF2 protein-antibody complex deposits are associated with glomerulonephritis in hepatitis E with reduced immune status

Hepatitis E virus (HEV) infection, one of the most common forms of hepatitis worldwide, is often associated with extrahepatic, particularly renal, manifestations. However, the underlying mechanisms are incompletely understood. Here, we report the development of a de novo immune complex-mediated glomerulonephritis (GN) in a kidney transplant recipient with chronic hepatitis E. Applying immunostaining, electron microscopy, and mass spectrometry after laser-capture microdissection, we show that GN develops in parallel with increasing glomerular deposition of a non-infectious, genome-free and non-glycosylated HEV open reading frame 2 (ORF2) capsid protein. No productive HEV infection of kidney cells is detected. Patients with acute hepatitis E display similar but less pronounced deposits. Our results establish a link between the production of HEV ORF2 protein and the development of hepatitis E-associated GN in the immunocompromised state. The formation of glomerular IgG-HEV ORF2 immune complexes discovered here provides a potential mechanistic explanation of how the hepatotropic HEV can cause variable renal manifestations. These findings directly provide a tool for etiology-based diagnosis of hepatitis E-associated GN as a distinct entity and suggest therapeutic implications.

Circulating Immune Complexes and Complement Activation in Sensitized Kidney Transplant Recipients.

Chronic antibody-mediated rejection in kidney transplantation is a common cause of graft loss in the late post-transplant period. In this process, the role of the classical complement activation pathway is crucial due to the formation of immune complexes between donor-specific antibodies (DSAs) and donor antigens and the attachment of the C1q complement fragment. This study aimed to determine the levels of circulating C1q immunocomplexes (CIC-C1q) and complement activation (CH50), in sensitized kidney transplant recipients (KTRs). In this cross-sectional study we used serum samples from KTRs with de novo or preformed DSAs (n = 14), KTRs without DSAs (n = 28), and 22 subjects with no history of chronic kidney disease (controls). C1q immunocomplexes and CH50 concentration in serum were measured with the enzyme immunoassay (EIA) kit MicroVue CIC-C1q (Quidel, Athens, OH, USA) and EIA kit MicroVue CH50 (Quidel, OH, USA), respectively. Higher concentrations of CIC-C1q was observed in KTRs with DSAs in comparison with controls and with KTRs with no DSAs (6.8 ± 2.7 and 4.8 ± 1.9 vs. 5.0 ± 1.2 μg Eq/mL, respectively, p < 0.01). We found no difference in CIC-C1q between KTRs with no DSAs and controls. CIC-C1q levels were positively correlated with DSA titer. CH50 levels were decreased in KTRs with DSAs in comparison with controls and KTRs with no DSAs (39 ± 15 vs. 68 ± 40 and 71 ± 34 U Eq/mL, respectively, p < 0.01). There was no difference in CH50 between DSA-negative KTRs and controls. Kidney transplant recipients with DSAs had increased serum levels of C1q immunocomplexes and increased classical pathway complement activation.

Foot-and-mouth disease virus antigenic landscape and reduced immunogenicity elucidated in atomic detail

Unlike most other picornaviruses, foot-and-mouth disease (FMD) intact virions (146S) dissociate easily into small pentameric subunits (12S). This causes a dramatically decreased immunogenicity by a mechanism that remains elusive. Here, we present the high-resolution structures of 12S (3.2 Å) and its immune complex of a single-domain antibody (VHH) targeting the particle interior (3.2 Å), as well as two 146S-specific VHHs complexed to distinct sites on the 146S capsid surface (3.6 Å and 2.9 Å). The antigenic landscape of 146S is depicted using 13 known FMD virus-antibody complexes. Comparison of the immunogenicity of 146S and 12S in pigs, focusing on the resulting antigenic sites and incorporating structural analysis, reveals that dissociation of 146S leads to structural alteration and destruction of multiple epitopes, resulting in significant differences in antibody profiles/lineages induced by 12S and 146S. Furthermore, 146S generates higher synergistic neutralizing antibody titers compared to 12S, whereas both particles induce similar total FMD virus specific antibody titers. This study can guide the structure-based rational design of novel multivalent and broad-spectrum recombinant vaccines for protection against FMD.

Specific Requirement of the p84/p110γ Complex of PI3Kγ for Antibody-Activated, Inducible Cross-Presentation in Murine Type 2 DCs.

Cross-presentation by MHCI is optimally efficient in type 1 dendritic cells (DC) due to their high capacity for antigen processing. However, through specific pathways, other DCs, such as type 2 DCs and inflammatory DCs (iDCs) can also cross-present antigens. FcγR-mediated uptake by type 2 DC and iDC subsets mediates antibody-dependent cross-presentation and activation of CD8+ T cell responses. Here, an important role for the p84 regulatory subunit of PI3Kγ in mediating efficient cross-presentation of exogenous antigens in otherwise inefficient cross-presenting cells, such as type 2 DCs and GM-CSF-derived iDCs is identified. FcγR-mediated cross-presentation is shown in type 2 and iDCs depend on the enzymatic activity of the p84/p110γ complex of PI3Kγ, which controls the activity of the NADPH oxidase NOX2 and ROS production in murine spleen type 2 DCs and GM-CSF-derived iDCs. In contrast, p84/p110γ is largely dispensable for cross-presentation by type 1 DCs. These findings suggest that PI3Kγ-targeted therapies, currently considered for oncological practice, may interfere with the ability of type 2 DCs and iDCs to cross-present antigens contained in immune complexes.

Effectiveness of new antituberculosis drugs in the treatment of children and adolescents with chemoresistant tuberculosis

BACKGROUND. There is a significant decrease the effectiveness of antituberculous (anti-TB) treatment on the background of multidrug and extensive drug resistance (MDR/XDR) of Mycobacterium tuberculosis. Therefore, in order to increase the effectiveness of treatment MDR-/XDR-TB a new antimycobacterial drugs such as bedaquiline (Bdq), delamanid (Dlm) and pretomanid have been introduced both for adults, children and adolescents in recent years. MATERIALS AND METHODS. On the basis of a retrospective cohort analysis of the data of patients' medical records the evaluation of the clinical effectiveness of chemotherapy with Bdq and Dlm was carried out. The main group: 40 children and adolescents with MDR-/XDR-TB of lungs, who received complex antimycobacterial therapy (AMBT) with Bdq and Dlm. The control group consisted of 27 patients who received complex AMBT without Bdq and Dlm. Age range – from 3 to 18 years. RESULTS AND DISCUSSION. On the background of AMBT during the first 3 months of treatment was established stopping bacterial secretion among all patients of main and control groups. However, in control group compare to main one stopping bacterial secretion was significant slowly (p&lt;0.05). At the stage of completion of the intensive phase of AMBT, the normalization of immunological indicators occurred in 29.6±2.8 % of control group and in 43.4±4.5 % of main one. A significant difference between the groups among the immunoregulatory index CD3+CD4+/CD3+CD8+, IgM and circulating immune complexes was obtained. Among children and adolescents of the main group positive dynamic of immunological changes were observed 1.5 times more often. Among all patients of main group the resolution of the infiltration, consolidation of the focus and the absence of decay cavities were ascertained at the end of the anti-TB course. Anti-TB treatment with the formation of small residual changes into lung tissue ended in 77.5 % patients of main group. In 12.5 % cases of control group destructions persisted and bacterial excretion resumed. A large residual changes such as multiple dense foci, fibrosis and residual decay cavities in control group were observed 2.3 times more often (51.9 % vs 22.5 %), p&lt;0.05, than in main one. Using Bdq and Dlm among children and adolescents with MDR-/XDR-TB significantly increased efficiency of complex treatment. Among main group (72.5 %) compare to control (33.3 %) one the results of treatment to be considered “cured” were 2.2 times more likely and 1.5 times less often – “completed” (27.5 % vs 51.8 % respectively). The success rate of treatment among children and adolescents who received Bdq and Dlm was 100.0 % and among patients without these new drugs – 85.2 %. CONCLUSIONS. The criteria used show that AMBT combined with Bdq and Dlm is 1.5-2.2 times more effective (according to a separate criterion) than AMBT without these drugs.