The gastrointestinal frontier: IgA and viruses

Incidence, timing, and management of infections in patients receiving teclistamab for the treatment of relapsed/refractory multiple myeloma in the MajesTEC-1 study

BACKGROUND

Patients with relapsed/refractory multiple myeloma are at increased risk of infection. Infections during treatment with teclistamab, the first B-cell maturation antigen-directed bispecific antibody approved for triple-class-exposed relapsed/refractory multiple myeloma, was examined in the phase 1/2 MajesTEC-1 study.

METHODS

Patients (N = 165) received subcutaneous teclistamab 1.5 mg/kg weekly after a step-up dosing schedule (0.06 mg/kg and 0.3 mg/kg, each separated by 2-4 days). Patients were monitored frequently for infections; prophylaxis and management were per institutional guidelines.

RESULTS

At a median follow-up of 22.8 months (range, 0.3-33.6), infections were reported in 132 patients (80.0%). Grade 3/4 infections occurred in 91 patients (55.2%), including COVID-19 (21.2%), respiratory infections (19.4%), Pneumocystis jirovecii pneumonia (4.2%), viral infections (4.2%), and gastrointestinal infections (1.2%). Twenty-one patients died from infections (18 from COVID-19). Median time to first onset of any-grade and grade 3 to 5 infections was 1.7 and 4.2 months, respectively. Overall, 70.9% of patients had ≥1 postbaseline immunoglobulin G (IgG) level <400 mg/dL; median time to IgG <400 mg/dL was 1.2 months (range, 0.2-19.8) and 46.1% received ≥1 dose of IgG replacement. Grade 3/4 neutropenia occurred in 65.5% of patients (median time to grade ≥3 neutropenia/febrile neutropenia was 2.3 months [range, 0-18.1]).

CONCLUSION

Based on the infection profile of B-cell maturation antigen-targeted bispecific antibodies such as teclistamab, it is recommended that clinicians and patients remain vigilant for a range of infection types throughout treatment to facilitate prompt intervention. Appropriate screening, prophylaxis, and management of infections, hypogammaglobulinemia, and neutropenia are important.

CLINICAL TRIAL REGISTRATION

NCT03145181/NCT04557098 (ClinicalTrials.gov) PLAIN LANGUAGE SUMMARY: Before starting teclistamab, patients should be up to date with vaccinations (including COVID-19) and screened for hepatitis B and C and HIV. Teclistamab should not be given to patients with any active infections. Prophylactic antimicrobials should be administered per institutional guidelines. Prophylaxis for Pneumocystis jirovecii pneumonia and herpes simplex/varicella zoster virus is recommended during teclistamab treatment. Close monitoring of infections and immunoglobulin G (IgG) levels should continue throughout teclistamab treatment. IgG replacement (administered every 3-6 weeks) should be used to maintain IgG ≥400 mg/dL. Growth factors should be considered for grade ≥3 neutropenia with infection/fever and grade 4 neutropenia.

Epidemiology of group A rotavirus in children under five years of age with gastroenteritis in N'Djamena, Chad

BACKGROUND

Group A Rotaviruses (RVA) is one of the most common causes of severe diarrhoea in infants and children under 5 years of age. Unlike many countries in the world where RVA surveillance/control is active, in Chad , there is currently no applied RVA immunization program and surveillance strategy. The present study aims to determine the prevalence and associated risk factors of RVA gastroenteritis among children under five years of age in N'Djamena.

METHOD

This study comprised two parts: (1) A cross-sectional study carried in four hospitals in N'Djamena between August and November 2019, to determine infection risk factors and evidence of RVA infection among children aged five and below, consulted or hospitalized for diarrhea. An ELISA based RVA VP6 protein detection was used to determine RVA infection prevalence. Infection results and sociodemographic data were statistically analysed to determine RVA infection risk factors. (2) A retrospective study that consisted of analysing the records of stool examinations of the period from January 2016 to December 2018, to determine the prevalence of infectious gastroenteritis among the target population.

RESULTS

For the cross-sectional study, RVA infection prevalence was 12.76% (18/141) with males (61.11%) being more affected (sex ratio: 1.57). Children below 12 months were the most affected age group (44.44%) and 44.4% were malnourished. The mean Vesikari score shows that 38.8% of children have a high severity level and 41.1% have a moderate level. For the retrospective study, 2,592 cases of gastroenteritis hospitalization were analysed; 980 out of 2,592 cases (37.81%) of hospitalization due to diarrhoea were due to diarrhoeagenic pathogens including Emtamoeba hystolitica, Gardia lamblia, Trichomonas hominis, Hymenolepis nana, Escherichia coli, Shigella spp, Proteus mirabilis, and Klebsiella oxytoca. Cases of diarrhoea with negative pathogen search were 1,612 cases (62.19%). The diarrhoea peak was observed during the dry seasons, and the age group under 11 months was the most affected was (57.3%).

CONCLUSION

This study describes the evidence of RVA infection among diarrhoeic children below five years of age in N'Djamena, thus indicates a serious health burden. Malnourishment younger age was the higher risk factor. Further studies are needed to determine the circulating strains prior to considering introduction of RVA vaccine and setup a routine rotavirus surveillance in Chad.

Immunoglobulin A response to SARS-CoV-2 infection and immunity

The novel coronavirus disease (COVID-19) and its infamous "Variants" of the etiological agent termed Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) has proven to be a global health concern. The three antibodies, IgA, IgM, and IgG, perform their dedicated role as main workhorses of the host adaptive immune system in virus neutralization. Immunoglobulin-A (IgA), also known as "Mucosal Immunoglobulin", has been under keen interest throughout the viral infection cycle. Its importance lies because IgA is predominant mucosal antibody and SARS family viruses primarily infect the mucosal surfaces of human respiratory tract. Therefore, IgA can be considered a diagnostic and prognostic marker and an active infection biomarker for SARS CoV-2 infection. Along with molecular analyses, serological tests, including IgA detection tests, are gaining ground in application as an early detectable marker and as a minimally invasive detection strategy. In the current review, it was emphasized the role of IgA response in diagnosis, host defense strategies, treatment, and prevention of SARS-CoV-2 infection. The data analysis was performed through almost 100 published peer-reviewed research reports and comprehended the importance of IgA in antiviral immunity against SARS-CoV-2 and other related respiratory viruses. Taken together, it is concluded that secretory IgA- Abs can serve as a promising detection tool for respiratory viral diagnosis and treatment parallel to IgG-based therapeutics and diagnostics. Vaccine candidates that target and trigger mucosal immune response may also be employed in future dimensions of research against other respiratory viruses.

Gut bacteria induce IgA expression in pituitary hormone-secreting cells during aging

Pituitary hormone decline is a hallmark of aging. However, the precise gene regulation mechanism during pituitary aging is unclear. Here, we characterized the cell population alteration and global transcriptional change during pituitary aging through single-cell RNA sequencing (scRNA-seq). We found that mRNA-encoding components of protein translational machinery declined the most in the pituitary during aging. Remarkably, Immunoglobulin A (IgA) was found to be expressed in hormone-secreting cells, and the IgA expression level increased dramatically in aged pituitary. Moreover, the pituitary IgA expression was regulated by gut microbiota. The non-hematopoietic origin of the IgA+ cells in the pituitary was further confirmed through bone marrow transplantation. Somatotropes were identified as the most prominent IgA-producing cells through lineage tracing. Thus, pituitary hormone-secreting cells can generate IgA in an age-dependent manner, and such a process is influenced by gut bacteria.

Select symbionts drive high IgA levels in the mouse intestine

Immunoglobulin A (IgA) is an important factor in maintaining homeostasis at mucosal surfaces, yet luminal IgA levels vary widely. Total IgA levels are thought to be driven by individual immune responses to specific microbes. Here, we found that the prebiotic, pectin oligosaccharide (pec-oligo), induced high IgA levels in the small intestine in a T cell-dependent manner. Surprisingly, this IgA-high phenotype was retained after cessation of pec-oligo treatment, and microbiome transmission either horizontally or vertically was sufficient to retain high IgA levels in the absence of pec-oligo. Interestingly, the bacterial taxa enriched in the overall pec-oligo bacterial community differed from IgA-coated microbes in this same community. Rather, a group of ethanol-resistant microbes, highly enriched for Lachnospiraceae bacterium A2, drove the IgA-high phenotype. These findings support a model of intestinal adaptive immunity in which a limited number of microbes can promote durable changes in IgA directed to many symbionts.

Immune responses in healthy adults elicited by a bivalent norovirus vaccine candidate composed of GI.4 and GII.4 VLPs without adjuvant

The development of an efficacious vaccine against norovirus is of paramount importance given its potential to reduce the global burden of norovirus-associated morbidity and mortality. Here, we report a detailed immunological analysis of a phase I, double-blind, placebo-controlled clinical trial performed on 60 healthy adults, ages 18 to 40. Total serum immunoglobulin and serum IgA against vaccine strains and cross-reactive serum IgG against non-vaccine strains were measured by enzyme immunoassays, whereas cell-mediated immune responses were quantified using intracellular cytokine staining by flow cytometry. A significant increase in humoral and cellular responses, e.g., IgA and CD4⁺ polypositive T cells, was triggered by the GI.4 Chiba 407 (1987) and GII.4 Aomori 2 (2006) VLP-based norovirus vaccine candidate rNV-2v, which is formulated without adjuvant. No booster effect was observed after the second administration in the pre-exposed adult study population. Furthermore, a cross-reactive immune response was elicited, as shown by IgG titers against GI.3 (2002), GII.2 OC08154 (2008), GII.4 (1999), GII.4 Sydney (2012), GII.4 Washington (2018), GII.6 Maryland (2018), and GII.17 Kawasaki 308 (2015). Due to viral infection via mucosal gut tissue and the high variety of potentially relevant norovirus strains, a focus should be on IgA and cross-protective humoral and cell-mediated responses in the development of a broadly protective, multi-valent norovirus vaccine.

Clinical trial registration

https://clinicaltrials.gov, identifier NCT05508178. EudraCT number: 2019-003226-25.

Evolutive emergence and divergence of an Ig regulatory node: An environmental sensor getting cues from the aryl hydrocarbon receptor?

One gene, the immunoglobulin heavy chain (IgH) gene, is responsible for the expression of all the different antibody isotypes. Transcriptional regulation of the IgH gene is complex and involves several regulatory elements including a large element at the 3' end of the IgH gene locus (3'RR). Animal models have demonstrated an essential role of the 3'RR in the ability of B cells to express high affinity antibodies and to express different antibody classes. Additionally, environmental chemicals such as aryl hydrocarbon receptor (AhR) ligands modulate mouse 3'RR activity that mirrors the effects of these chemicals on antibody production and immunocompetence in mouse models. Although first discovered as a mediator of the toxicity induced by the high affinity ligand 2,3,7,8-tetracholordibenzo-p-dioxin (dioxin), understanding of the AhR has expanded to a physiological role in preserving homeostasis and maintaining immunocompetence. We posit that the AhR also plays a role in human antibody production and that the 3'RR is not only an IgH regulatory node but also an environmental sensor receiving signals through intrinsic and extrinsic pathways, including the AhR. This review will 1) highlight the emerging role of the AhR as a key transducer between environmental signals and altered immune function; 2) examine the current state of knowledge regarding IgH gene regulation and the role of the AhR in modulation of Ig production; 3) describe the evolution of the IgH gene that resulted in species and population differences; and 4) explore the evidence supporting the environmental sensing capacity of the 3'RR and the AhR as a transducer of these cues. This review will also underscore the need for studies focused on human models due to the premise that understanding genetic differences in the human population and the signaling pathways that converge at the 3'RR will provide valuable insight into individual sensitivities to environmental factors and antibody-mediated disease conditions, including emerging infections such as SARS-CoV-2.

Gut microbiome in modulating immune checkpoint inhibitors

Funding

Bowel ischemia as onset of COVID-19 in otherwise asymptomatic patients with persistently negative swab

BACKGROUND

Asymptomatic patients with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can develop hypercoagulable conditions and acute vascular events. The objective of this study is to determine whether SARS-CoV-2 was present in resected specimens from patients with acute bowel ischemia, but asymptomatic for Coronavirus Disease 2019 (COVID-19) and with persistently real-time polymerase chain reaction negative pharyngeal swab.

METHODS

Three consecutive patients presented severe abdominal symptoms due to extensive ischemia and necrosis of the bowel, with co-existent thrombosis of abdominal blood vessels. None had the usual manifestations of COVID-19, and repeated pharyngeal swabs tested negative. They underwent emergency surgery with intestinal resection. Immunohistochemical testing for SARS-CoV-2 on resected tissue was performed.

RESULTS

All tested samples were strongly positive for SARS-CoV-2.

CONCLUSIONS

This is the first case report in which patients with severe intestinal symptoms presented a marked SARS-CoV-2 positivity in the resected tissues, without any usual clinical manifestations of COVID-19. These results suggest that the patients might be infected with SARS-CoV-2 presenting acute abdominal distress but without respiratory or constitutional symptoms.

Immune Evaluation of Recombinant Lactobacillus plantarum With Surface Display of HA1-DCpep in Mice

Avian influenza viruses can be efficiently transmitted through mucous membranes, and conventional vaccines are not effective in protecting against mucosal infection by influenza viruses. To induce multiple immune responses in an organism, we constructed a recombinant Lactobacillus plantarum expressing the influenza virus antigen HA1 with the adjuvant dendritic cell-targeting peptide (DCpep). The recombinant L. plantarum strains NC8Δ-pWCF-HA1 and NC8Δ-pWCF-HA1-DCpep were used to immunize mice via oral administration, and the humoral, cellular and mucosal immune responses were evaluated. In addition, the serum levels of specific antibodies and hemagglutination inhibition (HI) levels were also measured. Our results showed that recombinant L. plantarum activated dendritic cells in Peyer's patches (PPs), increased the numbers of CD4⁺IFN-γ⁺ and CD8⁺IFN-γ⁺ cells in the spleen and mesenteric lymph nodes (MLNs), and affected the ability of CD4⁺ and CD8⁺ cells to proliferate in the spleen and MLNs. Additionally, recombinant L. plantarum increased the number of B220⁺IgA⁺ cells in PPs and the level of IgA in the lungs and different intestinal segments. In addition, specific IgG, IgG1 and IgG2a antibodies were induced at high levels in the mice serum, specific IgA antibodies were induced at high levels in the mice feces, and HI potency was significantly increased. Thus, the recombinant L. plantarum strains NC8Δ-pWCF-HA1 and NC8Δ-pWCF-HA1-DCpep have potential as vaccine candidates for avian influenza virus.

Gut Microbiota, Microbial Metabolites and Human Physical Performance

Trillions of microbes inhabiting the gut modulate the metabolism of the host. Cross-sectional studies have reported associations between physical performance and the gut microbiota (GM). Physical activity seems to increase GM diversity and the abundance of certain health-beneficial microbes. We reviewed the evidence from longitudinal studies on the connection between physically active lifestyle or long-term exercise interventions and the GM. We made literature searches using databases of Web of Science and PubMed Medline to collect human studies showing or not the associations between the GM and exercise. Many controversies exist in the studies. However, the longitudinal studies show that frequently, medium-intensity endurance exercise has yielded most beneficial effects on the GM, but the results vary depending on the study population and exercise protocol. In addition, the literature shows that certain microbes own the potency to increase physical activity and performance. Generally, a physically active lifestyle and exercise associate with a “healthy” GM. However, in previously sedentary subjects, the exercise-induced improvements in the GM seem to disappear unless the active lifestyle is continued. Unfortunately, several studies are not controlled for the diet. Thus, in the future, more longitudinal studies on the GM and physical performance are needed, with detailed dietary information.

Antibody Class(es) Predictor for Epitopes (AbCPE): A Multi-Label Classification Algorithm

Development of vaccines and therapeutic antibodies to deal with infectious and other diseases are the most perceptible scientific interventions that have had huge impact on public health including that in the current Covid-19 pandemic. From inactivation methodologies to reverse vaccinology, vaccine development strategies of 21st century have undergone several transformations and are moving towards rational design approaches. These developments are driven by data as the combinatorials involved in antigenic diversity of pathogens and immune repertoire of hosts are enormous. The computational prediction of epitopes is central to these developments and numerous B-cell epitope prediction methods developed over the years in the field of immunoinformatics have contributed enormously. Most of these methods predict epitopes that could potentially bind to an antibody regardless of its type and only a few account for antibody class specific epitope prediction. Recent studies have provided evidence of more than one class of antibodies being associated with a particular disease. Therefore, it is desirable to predict and prioritize ‘peptidome’ representing B-cell epitopes that can potentially bind to multiple classes of antibodies, as an open problem in immunoinformatics. To address this, AbCPE, a novel algorithm based on multi-label classification approach has been developed for prediction of antibody class(es) to which an epitope can potentially bind. The epitopes binding to one or more antibody classes (IgG, IgE, IgA and IgM) have been used as a knowledgebase to derive features for prediction. Multi-label algorithms, Binary Relevance and Label Powerset were applied along with Random Forest and AdaBoost. Classifier performance was assessed using evaluation measures like Hamming Loss, Precision, Recall and F1 score. The Binary Relevance model based on dipeptide composition, Random Forest and AdaBoost achieved the best results with Hamming Loss of 0.1121 and 0.1074 on training and test sets respectively. The results obtained by AbCPE are promising. To the best of our knowledge, this is the first multi-label method developed for prediction of antibody class(es) for sequential B-cell epitopes and is expected to bring a paradigm shift in the field of immunoinformatics and immunotherapeutic developments in synthetic biology. The AbCPE web server is available at http://bioinfo.unipune.ac.in/AbCPE/Home.html.

Know your enemy or find your friend?-Induction of IgA at mucosal surfaces

Most antibodies produced in the body are of the IgA class. The dominant cell population producing them are plasma cells within the lamina propria of the gastrointestinal tract, but many IgA-producing cells are also found in the airways, within mammary tissues, the urogenital tract and inside the bone marrow. Most IgA antibodies are transported into the lumen by epithelial cells as part of the mucosal secretions, but they are also present in serum and other body fluids. A large part of the commensal microbiota in the gut is covered with IgA antibodies, and it has been demonstrated that this plays a role in maintaining a healthy balance between the host and the bacteria. However, IgA antibodies also play important roles in neutralizing pathogens in the gastrointestinal tract and the upper airways. The distinction between the two roles of IgA - protective and balance-maintaining - not only has implications on function but also on how the production is regulated. Here, we discuss these issues with a special focus on gut and airways.

Enteric viruses evoke broad host immune responses resembling those elicited by the bacterial microbiome

The contributions of the viral component of the microbiome-the virome-to the development of innate and adaptive immunity are largely unknown. Here, we systematically defined the host response in mice to a panel of eukaryotic enteric viruses representing six different families. Infections with most of these viruses were asymptomatic in the mice, the magnitude and duration of which was dependent on the microbiota. Flow cytometric and transcriptional profiling of mice mono-associated with these viruses unveiled general adaptations by the host, such as lymphocyte differentiation and IL-22 signatures in the intestine, as well as numerous viral-strain-specific responses that persisted. Comparison with a dataset derived from analogous bacterial mono-association in mice identified bacterial species that evoke an immune response comparable with the viruses we examined. These results expand an understanding of the immune space occupied by the enteric virome and underscore the importance of viral exposure events.

Probiotic stool secretory immunoglobulin A modulation in children with gastroenteritis: a randomized clinical trial

BACKGROUND

We previously conducted the Probiotic Regimen for Outpatient Gastroenteritis Utility of Treatment (PROGUT) study, which identified no improvements in children with acute gastroenteritis (AGE) administered a probiotic. However, the aforementioned study did not evaluate immunomodulatory benefits.

OBJECTIVES

The object of this study was to determine if stool secretory immunoglobulin A (sIgA) concentrations in children with AGE increase more among participants administered a Lactobacillus rhamnosus/helveticus probiotic compared with those administered placebo.

METHODS

This a priori planned multicenter, randomized, double-blinded, placebo-controlled ancillary study enrolled children presenting for emergency care who received a 5-d probiotic or placebo course. Participants submitted stool specimens on days 0, 5, and 28. The primary endpoint was the change in stool sIgA concentrations on day 5 compared with baseline.

RESULTS

A total of 133 (n = 66 probiotic, 67 placebo) of 886 PROGUT participants (15.0%) provided all 3 specimens. Median stool sIgA concentrations did not differ between the probiotic and placebo groups at any of the study time points: day 0 median (IQR): 1999 (768, 4071) compared with 2198 (702, 5278) (P = 0.27, Cohen's d = 0.17); day 5: 2505 (1111, 5310) compared with 3207 (982, 7080) (P = 0.19, Cohen's d = 0.16); and day 28: 1377 (697, 2248) compared with 1779 (660, 3977) (P = 0.27, Cohen's d = 0.19), respectively. When comparing measured sIgA concentrations between days 0 and 5, we found no treatment allocation effects [β: -0.24 (-0.65, 0.18); P = 0.26] or interaction between treatment and specimen collection day [β: -0.003 (-0.09, 0.09); P = 0.95]. Although stool sIgA decreased between day 5 and day 28 within both groups (P < 0.001), there were no differences between the probiotic and placebo groups in the median changes in sIgA concentrations when comparing day 0 to day 5 median (IQR) [500 (-1135, 2362) compared with 362 (-1122, 4256); P = 0.77, Cohen's d = 0.075] and day 5 to day 28 [-1035 (-3130, 499) compared with -1260 (-4437, 843); P = 0.70, Cohen's d = 0.067], respectively.

CONCLUSIONS

We found no effect of an L. rhamnosus/helveticus probiotic, relative to placebo, on stool IgA concentrations. This trial was registered at clinicaltrials.gov as NCT01853124.

Production and Function of Immunoglobulin A

Among antibodies, IgA is unique because it has evolved to be secreted onto mucosal surfaces. The structure of IgA and the associated secretory component allow IgA to survive the highly proteolytic environment of mucosal surfaces but also substantially limit IgA's ability to activate effector functions on immune cells. Despite these characteristics, IgA is critical for both preventing enteric infections and shaping the local microbiome. IgA's function is determined by a distinct antigen-binding repertoire, composed of antibodies with a variety of specificities, from permissive polyspecificity to cross-reactivity to exquisite specificity to a single epitope, which act together to regulate intestinal bacteria. Development of the unique function and specificities of IgA is shaped by local cues provided by the gut-associated lymphoid tissue, driven by the constantly changing environment of the intestine and microbiota.

The role of goblet cells in viral pathogenesis

Goblet cells are specialized epithelial cells that are essential to the formation of the mucus barriers in the airways and intestines. Armed with an arsenal of defenses, goblet cells can rapidly respond to infection but must balance this response with maintaining homeostasis. Whereas goblet cell defenses against bacterial and parasitic infections have been characterized, we are just beginning to understand their responses to viral infections. Here, we outline what is known about the enteric and respiratory viruses that target goblet cells, the direct and bystander effects caused by viral infection and how viral interactions with the mucus barrier can alter the course of infection. Together, these factors can play a significant role in driving viral pathogenesis and disease outcomes.

IgA and FcαRI: Versatile Players in Homeostasis, Infection, and Autoimmunity

Mucosal surfaces constitute the frontiers of the body and are the biggest barriers of our body for the outside world. Immunoglobulin A (IgA) is the most abundant antibody class present at these sites. It passively contributes to mucosal homeostasis via immune exclusion maintaining a tight balance between tolerating commensals and providing protection against pathogens. Once pathogens have succeeded in invading the epithelial barriers, IgA has an active role in host-pathogen defense by activating myeloid cells through divers receptors, including its Fc receptor, FcαRI (CD89). To evade elimination, several pathogens secrete proteins that interfere with either IgA neutralization or FcαRI-mediated immune responses, emphasizing the importance of IgA-FcαRI interactions in preventing infection. Depending on the IgA form, either anti- or pro-inflammatory responses can be induced. Moreover, the presence of excessive IgA immune complexes can result in continuous FcαRI-mediated activation of myeloid cells, potentially leading to severe tissue damage. On the one hand, enhancing pathogen-specific mucosal and systemic IgA by vaccination may increase protective immunity against infectious diseases. On the other hand, interfering with the IgA-FcαRI axis by monovalent targeting or blocking FcαRI may resolve IgA-induced inflammation and tissue damage. This review describes the multifaceted role of FcαRI as immune regulator between anti- and pro-inflammatory responses of IgA, and addresses potential novel therapeutic strategies that target FcαRI in disease.

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Repeat Dosing of AAV2.5T to Ferret Lungs Elicits an Antibody Response That Diminishes Transduction in an Age-Dependent Manner

Readministration of recombinant adeno-associated virus (rAAV) may be necessary to treat cystic fibrosis (CF) lung disease using gene therapy. However, little is known about rAAV-mediated immune responses in the lung. Here, we demonstrate the suitability of the ferret for testing AAV2.5T-mediated CFTR delivery to the lung and characterization of neutralizing-antibody (NAb) responses. AAV2.5T-SP183-hCFTRΔR efficiently transduced both human and ferret airway epithelial cultures and complemented CFTR Cl^– currents in CF airway cultures. Delivery of AAV2.5T-hCFTRΔR to neonatal and juvenile ferret lungs produced hCFTR mRNA at 200%–300% greater levels than endogenous fCFTR. Single-dose (AAV2.5T-SP183-gLuc) or repeat dosing (AAV2.5T-SP183-fCFTRΔR followed by AAV2.5T-SP183-gLuc) of AAV2.5T was performed in neonatal and juvenile ferrets. Repeat dosing significantly reduced transgene expression (11-fold) and increased bronchoalveolar lavage fluid (BALF) NAbs only in juvenile, but not neonatal, ferrets, despite near-equivalent plasma NAb responses in both age groups. Notably, both age groups demonstrated a reduction in BALF anti-capsid binding immunoglobulin (Ig) G, IgM, and IgA antibodies after repeat dosing. Unique to juvenile ferrets was a suppression of plasma anti-capsid-binding IgM after the second vector administration. Thus, age-dependent immune system maturation and isotype switching may affect the development of high-affinity lung NAbs after repeat dosing of AAV2.5T and may provide a path to blunt AAV-neutralizing responses in the lung.

Persistence of serum and saliva antibody responses to SARS-CoV-2 spike antigens in COVID-19 patients

While the antibody response to SARS-CoV-2 has been extensively studied in blood, relatively little is known about the antibody response in saliva and its relationship to systemic antibody levels. Here, we profiled by enzyme-linked immunosorbent assays (ELISAs) IgG, IgA and IgM responses to the SARS-CoV-2 spike protein (full length trimer) and its receptor-binding domain (RBD) in serum and saliva of acute and convalescent patients with laboratory-diagnosed COVID-19 ranging from 3-115 days post-symptom onset (PSO), compared to negative controls. Anti-SARS-CoV-2 antibody responses were readily detected in serum and saliva, with peak IgG levels attained by 16-30 days PSO. Longitudinal analysis revealed that anti-SARS-CoV-2 IgA and IgM antibodies rapidly decayed, while IgG antibodies remained relatively stable up to 105 days PSO in both biofluids. Lastly, IgG, IgM and to a lesser extent IgA responses to spike and RBD in the serum positively correlated with matched saliva samples. This study confirms that serum and saliva IgG antibodies to SARS-CoV-2 are maintained in the majority of COVID-19 patients for at least 3 months PSO. IgG responses in saliva may serve as a surrogate measure of systemic immunity to SARS-CoV-2 based on their correlation with serum IgG responses.

Persistence of serum and saliva antibody responses to SARS-CoV-2 spike antigens in COVID-19 patients

While the antibody response to SARS-CoV-2 has been extensively studied in blood, relatively little is known about the antibody response in saliva and its relationship to systemic antibody levels. Here, we profiled by enzyme-linked immunosorbent assays (ELISAs) IgG, IgA and IgM responses to the SARS-CoV-2 spike protein (full length trimer) and its receptor-binding domain (RBD) in serum and saliva of acute and convalescent patients with laboratory-diagnosed COVID-19 ranging from 3-115 days post-symptom onset (PSO), compared to negative controls. Anti-SARS-CoV-2 antibody responses were readily detected in serum and saliva, with peak IgG levels attained by 16-30 days PSO. Longitudinal analysis revealed that anti-SARS-CoV-2 IgA and IgM antibodies rapidly decayed, while IgG antibodies remained relatively stable up to 105 days PSO in both biofluids. Lastly, IgG, IgM and to a lesser extent IgA responses to spike and RBD in the serum positively correlated with matched saliva samples. This study confirms that serum and saliva IgG antibodies to SARS-CoV-2 are maintained in the majority of COVID-19 patients for at least 3 months PSO. IgG responses in saliva may serve as a surrogate measure of systemic immunity to SARS-CoV-2 based on their correlation with serum IgG responses.

When Therapeutic IgA Antibodies Might Come of Age

BACKGROUND

Extensive efforts have been made in optimizing monoclonal immunoglobulin (Ig)G antibodies for use in clinical practice. Accumulating evidence suggests that IgA or anti-FcαRI could also represent an exciting avenue toward novel therapeutic strategies.

SUMMARY

Here, we underline that IgA is more effective in recruiting neutrophils for tumor cell killing and is potently active against several pathogens, including rotavirus, poliovirus, influenza virus, and SARS-CoV-2. IgA could also be used to modulate excessive immune responses in inflammatory diseases. Furthermore, secretory IgA is emerging as a major regulator of gut microbiota, which impacts intestinal homeostasis and global health as well. As such, IgA could be used to promote a healthy microbiota in a therapeutic setting. Key messages: IgA combines multifaceted functions that can be desirable for immunotherapy.

T cell help to B cells: Cognate and atypical interactions in peripheral and intestinal lymphoid tissues

Enduring immunity against harmful pathogens depends on the generation of immunological memory. Serum immunoglobulins are constantly secreted by long-lived antibody-producing cells, which provide extended protection from recurrent exposures. These cells originate mainly from germinal center structures, wherein B cells introduce mutations to their immunoglobulin genes followed by affinity-based selection. Generation of high-affinity antibodies relies on physical contacts between T and B cells, a process that facilitates the delivery of fate decision signals. T-B cellular engagements are mediated through interactions between the T cell receptor and its cognate peptide presented on B cell major histocompatibility class II molecules. Here, we describe the cellular and molecular aspects of these cognate T-B interactions, and highlight exceptional cases, especially those arising at intestinal lymphoid organs, at which T cells provide help to B cells in an atypical manner, independent of T cell specificity.

Antibody-based therapeutic interventions: possible strategy to counter chikungunya viral infection

Chikungunya virus (CHIKV), a mosquito-transmitted disease that belongs to the genus Alphaviruses, has been emerged as an epidemic threat over the last two decades, and the recent co-emergence of this virus along with other circulating arboviruses and comorbidities has influenced atypical mortality rate up to 10%. Genetic variation in the virus has resulted in its adaptability towards the new vector Aedes albopictus other than Aedes aegypti, which has widen the horizon of distribution towards non-tropical and non-endemic areas. As of now, no licensed vaccines or therapies are available against CHIKV; the treatment regimens for CHIKV are mostly symptomatic, based on the clinical manifestations. Development of small molecule drugs and neutralizing antibodies are potential alternatives of worth investigating until an efficient or safe vaccine is approved. Neutralizing antibodies play an important role in antiviral immunity, and their presence is a hallmark of viral infection. In this review, we describe prospects for effective vaccines and highlight importance of neutralizing antibody-based therapeutic and prophylactic applications to combat CHIKV infections. We further discuss about the progress made towards CHIKV therapeutic interventions as well as challenges and limitation associated with the vaccine development. Furthermore this review describes the lesson learned from chikungunya natural infection, which could help in better understanding for future development of antibody-based therapeutic measures.

Fecal Components Modulate Human Astrovirus Infectivity in Cells and Reconstituted Intestinal Tissues

To ensure transmission, enteric viruses must maintain their infectivity during the various environmental challenges that they face in transit within and between hosts. Increased knowledge of the factors affecting enteric virus survival may help to control their transmission. This study reveals that specific fecal bacterial components preserve classic human astrovirus infectivity by stabilizing viral particles. However, the outcomes of stool-virus interactions are very variable, ranging from protection to a reduction of viral infectivity, depending on the viral genotype and the individual from whom the stool has been collected. We show that the transmissibility of enteric viruses is dependent on the intestinal contents of the infected individual and highlight the complex multiple interactions that could explain the stochastic nature of enteric virus transmission in humans.

Human astroviruses (HAstV) are among the most common causative agents of viral gastroenteritis, especially in children, and extraintestinal manifestations have also been described. These viruses are transmitted by the fecal-oral route, implying that stool composition and the gut microbiota may impact their ability to remain infectious. For some enteric viruses, individual bacterial envelope components and other polysaccharide-containing molecules, which are abundant in stools, have been shown to enhance capsid stability. However, the role of the complex stool environment and, most importantly, the role of interindividual differences have been poorly studied. We used HAstV as a model to investigate how the stool environment in itself, its interindividual variability, and some specific stool components could affect HAstV stability and infectivity. Using two different HAstV genotypes, we found that stools as a whole modulate astrovirus infectivity not only in an individual-dependent manner but also in a manner that depends on the viral genotype. A virus-protective effect was observed after incubation with various Gram-positive and Gram-negative bacteria as well as with bacterial components, such as lipopolysaccharide and peptidoglycan. These results were further confirmed in human intestinal tissues, a more physiologically relevant system. Astrovirus infectivity was also preserved by mucin, a major component of intestinal mucus. We further confirmed that these components stabilize the viral capsid. These results show that although HAstV benefits from the stabilizing effect of fecal components, the complexity and variability of the stool composition and the multiple potential interactions may explain the interindividual differences in viral transmission observed in real life.

IMPORTANCE To ensure transmission, enteric viruses must maintain their infectivity during the various environmental challenges that they face in transit within and between hosts. Increased knowledge of the factors affecting enteric virus survival may help to control their transmission. This study reveals that specific fecal bacterial components preserve classic human astrovirus infectivity by stabilizing viral particles. However, the outcomes of stool-virus interactions are very variable, ranging from protection to a reduction of viral infectivity, depending on the viral genotype and the individual from whom the stool has been collected. We show that the transmissibility of enteric viruses is dependent on the intestinal contents of the infected individual and highlight the complex multiple interactions that could explain the stochastic nature of enteric virus transmission in humans.

Trying to treat the untreatable: experimental approaches to clear rabies virus infection from the CNS

Rabies virus causes an invariably fatal encephalitis following the onset of clinical disease. Despite the availability of safe and effective vaccines, the clinical stages of rabies encephalitis remain untreatable, with few survivors being documented. A principal obstacle to the treatment of rabies is the neurotropic nature of the virus, with the blood-brain barrier size exclusion limit rendering the delivery of antiviral drugs and molecules to the central nervous system inherently problematic. This review focuses on efforts to try and overcome barriers to molecule delivery to treat clinical rabies and overviews current progress in the development of experimental live rabies virus vaccines that may have future applications in the treatment of clinical rabies, including the attenuation of rabies virus vectors through either the duplication or mutation of existing genes or the incorporation of non-viral elements within the genome. Rabies post-infection treatment (PIT) remains the holy grail of rabies research.

IgA and FcαRI: Pathological Roles and Therapeutic Opportunities

Immunoglobulin A (IgA) is the most abundant antibody class present at mucosal surfaces. The production of IgA exceeds the production of all other antibodies combined, supporting its prominent role in host-pathogen defense. IgA closely interacts with the intestinal microbiota to enhance its diversity, and IgA has a passive protective role via immune exclusion. Additionally, inhibitory ITAMi signaling via the IgA Fc receptor (FcαRI; CD89) by monomeric IgA may play a role in maintaining homeostatic conditions. By contrast, IgA immune complexes (e.g., opsonized pathogens) potently activate immune cells via cross-linking FcαRI, thereby inducing pro-inflammatory responses resulting in elimination of pathogens. The importance of IgA in removal of pathogens is emphasized by the fact that several pathogens developed mechanisms to break down IgA or evade FcαRI-mediated activation of immune cells. Augmented or aberrant presence of IgA immune complexes can result in excessive neutrophil activation, potentially leading to severe tissue damage in multiple inflammatory, or autoimmune diseases. Influencing IgA or FcαRI-mediated functions therefore provides several therapeutic possibilities. On the one hand (passive) IgA vaccination strategies can be developed for protection against infections. Furthermore, IgA monoclonal antibodies that are directed against tumor antigens may be effective as cancer treatment. On the other hand, induction of ITAMi signaling via FcαRI may reduce allergy or inflammation, whereas blocking FcαRI with monoclonal antibodies, or peptides may resolve IgA-induced tissue damage. In this review both (patho)physiological roles as well as therapeutic possibilities of the IgA-FcαRI axis are addressed.

Rare Detection of Antiviral Functions of Polyclonal IgA Isolated from Plasma and Breast Milk Compartments in Women Chronically Infected with HIV-1

The humoral response to invading mucosal pathogens comprises multiple antibody isotypes derived from systemic and mucosal compartments. To understand the contribution of each antibody isotype/source to the mucosal humoral response, parallel investigation of the specificities and functions of antibodies within and across isotypes and compartments is required. The role of IgA against HIV-1 is complex, with studies supporting a protective role as well as a role for serum IgA in blocking effector functions. Thus, we explored the fine specificity and function of IgA in both plasma and mucosal secretions important to infant HIV-1 infection, i.e., breast milk. IgA and IgG were isolated from milk and plasma from 20 HIV-1-infected lactating Malawian women. HIV-1 binding specificities, neutralization potency, inhibition of virus-epithelial cell binding, and antibody-mediated phagocytosis were measured. Fine-specificity mapping showed IgA and IgG responses to multiple HIV-1 Env epitopes, including conformational V1/V2 and linear V2, V3, and constant region 5 (C5). Env IgA was heterogeneous between the milk and systemic compartments (Env IgA, τ = 0.00 to 0.63, P = 0.0046 to 1.00). Furthermore, IgA and IgG appeared compartmentalized as there was a lack of correlation between the specificities of Env-specific IgA and IgG (in milk, τ = -0.07 to 0.26, P = 0.35 to 0.83). IgA and IgG also differed in functions: while neutralization and phagocytosis were consistently mediated by milk and plasma IgG, they were rarely detected in IgA from both milk and plasma. Understanding the ontogeny of the divergent IgG and IgA antigen specificity repertoires and their effects on antibody function will inform vaccination approaches targeted toward mucosal pathogens.IMPORTANCE Antibodies within the mucosa are part of the first line of defense against mucosal pathogens. Evaluating mucosal antibody isotypes, specificities, and antiviral functions in relationship to the systemic antibody profile can provide insights into whether the antibody response is coordinated in response to mucosal pathogens. In a natural immunity cohort of HIV-infected lactating women, we mapped the fine specificity and function of IgA in breast milk and plasma and compared these with the autologous IgG responses. Antigen specificities and functions differed between IgG and IgA, with antiviral functions (neutralization and phagocytosis) predominantly mediated by the IgG fraction in both milk and plasma. Furthermore, the specificity of milk IgA differed from that of systemic IgA. Our data suggest that milk IgA and systemic IgA should be separately examined as potential correlates of risk. Preventive vaccines may need to employ different strategies to elicit functional antiviral immunity by both antibody isotypes in the mucosa.

Nucleic Acid Induced Interferon and Inflammasome Responses in Regulating Host Defense to Gastrointestinal Viruses

The gut bacterial and fungal communities residing in the gastrointestinal tract have undisputed far-reaching effects in regulating host health. In the meantime, however, metagenomic sequencing efforts are revealing enteric viruses as the most abundant dimension of the intestinal gut ecosystem, and the first gut virome-wide association studies showed that inflammatory bowel disease as well as type 1 diabetes could be linked to the presence or absence of particular viral inhabitants in the intestine. In line with the genetic component of these human diseases, mouse model studies demonstrated how beneficial functions of a resident virus can switch to detrimental inflammatory effects in a genetically predisposed host. Such viral-induced intestinal immune disturbances are also recapitulated by several gastrointestinal infectious viruses such as rotavirus and human norovirus. This wide range of viral effects on intestinal immunity emphasizes the need for understanding the innate immune responses to gastrointestinal viruses. Numerous nucleic acid sensors such as DexD/H helicases and AIM2 serve as cytosolic viral guardians to induce antiviral interferon and/or pro-inflammatory inflammasome responses. In both cases, pioneering examples are emerging in which RNA helicases cooperate with particular Nod-like receptors to trigger these cellular responses to enteric viruses. Here we summarize the reported beneficial versus detrimental effects of enteric viruses in the intestinal immune system, and we zoom in on the mechanisms through which sensing of nucleic acids from these enteric viruses trigger interferon and inflammasome responses.

Porcine endemic diarrhea virus infection regulates long noncoding RNA expression

Long noncoding RNAs (lncRNAs) have been implicated in various life processes. However, the lncRNA expression and potential functions in porcine endemic diarrhea virus (PEDV) infection and host defense are still poorly understood. In this study, we investigated the lncRNA expression profiles during PEDV infection in intestinal porcine epithelial cell-jejunum 2 (IPEC-J2) cell lines by next-generation sequencing and identified 6188 novel lncRNAs. The functional annotation analysis revealed that these lncRNAs might be associated with many immunity-related genes. We next selected candidate lncRNAs related to immune response pathways and further identified their differential expression in PEDV-infected IPEC-J2 cells and newborn piglets. Our results demonstrated that PEDV infection regulated lncRNA expression patterns in both the IPEC-J2 cell line and piglet ileum. These findings provide the first large-scale survey of lncRNAs associated with PEDV infection, specifically the lncRNAs responsible for the activation of the immune system within the ileum.

Effect of route of inoculation on innate and adaptive immune responses to porcine epidemic diarrhea virus infection in suckling pigs

The effects of route of administration on systemic and gut mucosal immune responses induced by porcine epidemic diarrhea virus (PEDV) infection in suckling pigs were investigated. Twenty-four conventional 5-day-old suckling piglets were randomly divided into four groups and were inoculated orally, intranasally (I.N.), intramuscularly (I.M.) with PEDV or DMEM (mock). Pigs were monitored daily for clinical signs and fecal viral load. Blood samples were collected at 7, 14, 21 days post infection (dpi) and subjected for the analyses of serum antibody production, T cell and natural killer (NK) cell frequencies, NK cytotoxicity and serum cytokine levels. Oral inoculation led to higher levels of PEDV-specific IgA antibodies in both serum and gut mucosal sites than did other routes of inoculation. Intranasal inoculation elicited significantly higher titers of virus-specific IgG antibodies in serum. PEDV-infected pigs regardless of inoculation routes had significantly lower NK cell frequencies than those of the control pigs at 14 dpi. The orally inoculated pigs had significantly higher CD3+CD8+ T cell frequencies as compared to I.N. or I.M. inoculated pigs at 14 dpi, while there was no significant difference among orally, I.N. or I.M. inoculated pigs and control pigs in CD3+CD4+ T cell frequencies in peripheral blood. PEDV-infected and control pigs had low, but detectable NK cell activities at 14 and 21 dpi, however, NK cell activities were barely detectable at 7 dpi whether the pigs were infected or not. Serum IL-10 levels were induced drastically in orally infected pigs at 7 dpi and then gradually declined. Serum IL-12 levels followed a similar pattern while the fold-change was much lower. In conclusion, oral inoculation may generate more comprehensive immune responses.

Salivary anti-coxsackievirus-B4 neutralizing activity and pattern of immune parameters in patients with type 1 diabetes: a pilot study

AIMS

Enteroviruses, especially coxsackieviruses B (CV-B), have been associated with the pathogenesis of type 1 diabetes (T1D). An anti-CV-B4 neutralizing activity in saliva of T1D patients was previously reported. Our aim was to study the association between the saliva anti-CV-B4 neutralizing activity and immune parameters in T1D patients in comparison with non-diabetic individuals.

METHODS

Saliva and blood samples were collected from 15 T1D patients and 8 controls. The anti-CV-B4 and anti-poliovirus type 1 (PV-1) activities of saliva and serum samples were determined by a plaque neutralization assay. Quantification of serum cytokines was performed by ELISA and the frequencies of lymphocyte subsets were evaluated using flow cytometry.

RESULTS

The levels of salivary anti-CV-B4 neutralizing activity were higher in T1D patients than in controls (p = 0.02), whereas the serum levels of anti-CV-B4 neutralizing activity and the saliva and serum levels of anti-PV-1 neutralizing activity were not different. The proportions of effector CD4⁺ T cells and CD19⁺ B cells, but not those of CD4⁺ T cells, CD8⁺ T cells and Foxp3⁺ regulatory T cells, were higher in T1D patients than in controls (p = 0.02 and p = 0.01 respectively). Moreover, serum IFN-γ levels were lower in T1D patients compared to controls (p = 0.03) while IL-4 and IL-10 were not different. There was an association between saliva anti-CV-B4 activity, down-regulation of IFN-γ and B cell expansion in peripheral blood of T1D patients.

CONCLUSION

The association between saliva anti-CV-B4 activity and disturbance of immune system in T1D patients deserves further investigation.

More robust gut immune responses induced by combining intranasal and sublingual routes for prime-boost immunization

Norovirus causes acute and debilitating gastroenteritis, characterized by vomiting and diarrhea. We recently reported a recombinant GII. 4 P domain particle (Pd) vaccine adjuvanted with a flagellin, Vibrio vulnificus FlaB, effectively promoting both humoral and cell-mediated immune responses. In the previous study, we found that sublingual (SL) immunization induced higher fecal secretory IgA (SIgA) responses while intranasal (IN) route provided higher amplitude of humoral and cellular immune responses in the systemic compartment. We hypothesized that the combination of IN and SL routes should induce more potent and sustained SIgA responses in the gut. In this study, we have tried combinatorial prime-boost immunization employing both IN and SL routes. The IN priming and SL boosting with the Pd+FlaB vaccine enhanced highest SIgA responses in feces, accompanying increased Pd-specific memory B cells and plasma cells in spleen and bone marrow, respectively. Notably, the strongest long-lasting SIgA response in feces was induced by combined IN prime and SL boost vaccination, which was sustained for more than 3 months. Significantly enhanced gut-homing B cell and follicular helper T cell responses in mesenteric lymph nodes (mLNs) were observed in the IN prime and SL boost combination. IN priming was a requisite for the robust induction of Pd-specific IFNγ, IL-2, IL-4 and IL-5 cytokine responses in the systemic immune compartment. Collectively, the IN prime and SL boost combination was the best option for inducing balanced long-lasting immune responses against the norovirus antigen in both enteric and systemic compartments. These results suggest that immune responses in specific mucosal compartments may be programmed by employing different prime-boost immunization routes.

Bacteria and bacterial envelope components enhance mammalian reovirus thermostability

Enteric viruses encounter diverse environments as they migrate through the gastrointestinal tract to infect their hosts. The interaction of eukaryotic viruses with members of the host microbiota can greatly impact various aspects of virus biology, including the efficiency with which viruses can infect their hosts. Mammalian orthoreovirus, a human enteric virus that infects most humans during childhood, is negatively affected by antibiotic treatment prior to infection. However, it is not known how components of the host microbiota affect reovirus infectivity. In this study, we show that reovirus virions directly interact with Gram positive and Gram negative bacteria. Reovirus interaction with bacterial cells conveys enhanced virion thermostability that translates into enhanced attachment and infection of cells following an environmental insult. Enhanced virion thermostability was also conveyed by bacterial envelope components lipopolysaccharide (LPS) and peptidoglycan (PG). Lipoteichoic acid and N-acetylglucosamine-containing polysaccharides enhanced virion stability in a serotype-dependent manner. LPS and PG also enhanced the thermostability of an intermediate reovirus particle (ISVP) that is associated with primary infection in the gut. Although LPS and PG alter reovirus thermostability, these bacterial envelope components did not affect reovirus utilization of its proteinaceous cellular receptor junctional adhesion molecule-A or cell entry kinetics. LPS and PG also did not affect the overall number of reovirus capsid proteins σ1 and σ3, suggesting their effect on virion thermostability is not mediated through altering the overall number of major capsid proteins on the virus. Incubation of reovirus with LPS and PG did not significantly affect the neutralizing efficiency of reovirus-specific antibodies. These data suggest that bacteria enhance reovirus infection of the intestinal tract by enhancing the thermal stability of the reovirus particle at a variety of temperatures through interactions between the viral particle and bacterial envelope components.

The regulation of gut mucosal IgA B-cell responses: recent developments

The majority of activated B cells differentiate into IgA plasma cells, with the gut being the largest producer of immunoglobulin in the body. Secretory IgA antibodies have numerous critical functions of which protection against infections and the role for establishing a healthy microbiota appear most important. Expanding our knowledge of the regulation of IgA B-cell responses and how effective mucosal vaccines can be designed are of critical importance. Here we discuss recent developments in the field that shed light on the uniqueness and complexity of mucosal IgA responses and the control of protective IgA responses in the gut, specifically.

Marker of coxsackievirus-B4 infection in saliva of patients with type 1 diabetes

BACKGROUND

Coxsackieviruses B (CV-B) are enteroviruses that have been reported to play a role in the pathogenesis of type 1 diabetes. Enteroviral RNA was detected in the gut mucosa of patients. The mucosal immunity is an interconnected network; therefore, the response to enteroviruses possibly present in the gastrointestinal mucosa can be reflected by specific antibodies in the saliva. In the present study, the anti-CV-B neutralizing activity of saliva samples from patients with type 1 diabetes was investigated.

METHODS

Saliva samples were collected from patients and controls of 3 countries, and plasma was obtained from some of them. The anti-CV-B activity of clinical samples was determined by neutralization of the cytopathic effect induced by challenging viruses in vitro and expressed as titre value.

RESULTS

Overall prevalence and levels of anti-CV-B4 activity of saliva were higher in patients (n = 181) than in controls (n = 135; P = .0002; titre values ≥ 16: odds ratio = 4.22 95% CI: 1.90-9.38 P = .0002). It has been shown that IgA1 played a role in this activity. There was no correlation between the saliva and the plasma anti-CV-B4 neutralizing activity. The neutralizing activity of saliva against CV-B1, CV-B2, CV-B3, and CV-B5 existed rarely, if at all. Increased levels of anti-CV-B4 activity were observed all along a 4 year follow-up period in patients but not in matched controls (P = .01).

CONCLUSION

There is an anti-CV-B4 activity in saliva of patients with type 1 diabetes that may be a useful marker to study the role of CV-B in the pathogenesis of the disease.

NSP4 antibody levels in rotavirus gastroenteritis patients with seizures

BACKGROUND

Rotavirus nonstructural protein 4 (NSP4) has been suggested as a pathogen of rotavirus-associated seizures. We investigated pre-existing serum antibodies against NSP4 and VP6 (the most highly immunogenic rotavirus protein) in patients with rotavirus gastroenteritis and its correlation with the occurrence of seizures.

METHODS

With an enzyme-linked immunosorbent assay, IgG and IgA titers against NSP4 (genotype [A] and [B]) and VP6 were measured in acute-phase sera of 202 children aged 0.5-6.0 years with rotavirus gastroenteritis. The clinical characteristics and antibody levels were compared between patients with (seizure group) and without seizures (non-seizure group).

RESULTS

The non-seizure and seizure groups comprised 173 and 29 patients, respectively. Age, sex, hospital stay, presence of fever, white blood cell counts, C-reactive protein, vaccine status, IgG/IgA titers for VP6, and IgA titers for both NSP4s did not differ between the groups. The seizure group showed a lower level of IgG against NSP4 [A] (184.5 vs. 163.0 U/mL; P = 0.03) and NSP4 [B] (269.0 vs. 196.0 U/mL; P = 0.02). Delayed sampling time from the onset of gastroenteritis symptoms (3 vs. 2 days; P = 0.02) and lower serum sodium level (133.4 vs. 136.3 mEq/L; P < 0.01) were observed in the seizure group. Even after adjusting these factors, anti-NSP4 [A] IgG (OR 2.56 per 100 U/mL increment; 95% CI, 1.20-5.26, P = 0.01) and anti-NSP4 [B] IgG (OR 1.51 per 100 U/mL-increment; 95% CI, 1.04-2.22, P = 0.03) were independently associated with protection against seizures.

CONCLUSIONS

Serum anti-NSP4 IgG might protect rotavirus-associated seizures.

Immunoglobulin A: magic bullet or Trojan horse?

BACKGROUND

Neutrophils participate in the first line of defense by executing several killing mechanisms, including phagocytosis, degranulation and the release of neutrophil extracellular traps. Additionally, they can orchestrate the adaptive immune system by secreting cytokines and chemokines. Opsonization with antibodies aids in the recognition of pathogens, via binding to Fc receptors on the neutrophil surface. Immunoglobulin A (IgA) is the most abundant antibody at mucosal sites and has multiple functions in homeostasis and immunity. Neutrophils and IgA can interact via the IgA Fc receptor Fc?RI (CD89), leading to pro- or anti-inflammatory responses.

AIMS

The aim of this review is to give a concise overview of the interplay between IgA, Fc?RI and neutrophils and to explore potential therapies for autoimmune diseases and cancer.

RESULTS

Crosslinking of FcαRI by IgA-immune complexes yields potent neutrophil activation and pro-inflammatory effector functions, including the recruitment of neutrophils. This can lead to neutrophil accumulation and tissue destruction during IgA-autoantibody mediated diseases. Conversely, for cancer treatment, the myriad of powerful neutrophil effector functions after targeting FcαRI may contribute to effective immunotherapy.

CONCLUSION

By interfering with or actively promoting the interaction between IgA and FcαRI, therapies for multiple maladies could be developed.

Peyer's patches: organizing B-cell responses at the intestinal frontier

Secondary lymphoid tissues share the important function of bringing together antigens and rare antigen-specific lymphocytes to foster induction of adaptive immune responses. Peyer's patches (PPs) are unique compared to other secondary lymphoid tissues in their continual exposure to an enormous diversity of microbiome- and food-derived antigens and in the types of pathogens they encounter. Antigens are delivered to PPs by specialized microfold (M) epithelial cells and they may be captured and presented by resident dendritic cells (DCs). In accord with their state of chronic microbial antigen exposure, PPs exhibit continual germinal center (GC) activity. These GCs not only contribute to the generation of B cells and plasma cells producing somatically mutated gut antigen-specific IgA antibodies but have also been suggested to support non-specific antigen diversification of the B-cell repertoire. Here, we review current understanding of how PPs foster B-cell encounters with antigen, how they favor isotype switching to the secretory IgA isotype, and how their GC responses may uniquely contribute to mucosal immunity.

Emergence of human caliciviruses among diarrhea cases in southwest China

BACKGROUND

Acute diarrhea is one of the most serious problems in global public health that causes considerable morbidity and mortality worldwide. Human caliciviruses (HuCV) including norovirus (NoV, genogroup GI and GII) and sapovirus (SaV), is a leading cause of acute sporadic diarrhea in individuals across all age groups. However, few studies had been conducted clarifying the characteristics of HuCV in diarrhea cases across all age groups in China. Our study was aimed at assessing the HuCV-related diarrhea burden and NoV genotypes distribution in southwest China.

METHODS

The study was conducted in four hospitals in Kunming city, Yunnan province, from June 2014 to July 2015. Stool specimens were collected from 1,121 diarrhea cases and 319 healthy controls in outpatient departments. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect NoV (GI, GII) and SaV. Sequencing was applied to confirm the three viral infections and phylogenetic analysis was performed to determine their genotypes. A structured questionnaire was used to record the demographic information and clinical symptoms of subjects.

RESULTS

HuCV was detected at an 11.0 % infection rate in 1,121 diarrhea cases and at 3.4 % rate in 319 non-diarrhea subjects (p < 0.0001, OR = 3.5, 95 % CI 1.8-6.5). The prevalence of the NoV genogroup GII and genotype GII.4 in diarrhea cases was significantly higher than that found in healthy controls (p < 0.0001, p = 0.018, respectively). NoV GII (n = 118, 10.5 %) was the most common HuCV subtype in diarrhea cases, followed by SaV (n = 3, 0.3 %) and NoV GI (n = 2, 0.2 %). Of 118 NoV GII strains isolated from diarrhea patients. GII.4 (n = 55, 46.6 %) was the predominant strain, followed by GII.3 (n = 28, 23.7 %), GII.12 (n = 25, 21.2 %), GII.17 (n = 8, 6.8 %), and GII.5 (n = 2, 1.7 %). Of the 55 GII.4 strains, the GII.4 Sydney 2012 variant had absolutely predominant prevalence (n = 52, 94.5 %), followed by the NoV GII.4-2006b variant (n = 3, 5.5 %). The GII.4 Orleans 2009 variant was not found in diarrhea cases of the study.

CONCLUSIONS

NoV GII was the major genogroup and GII.4 was the most predominant strain detected in diarrhea patients. The GII.17 is an emergent variant in sporadic diarrhea and might become the predominant strain in diarrhea cases in the near future. Rapid, accurate detection kits need to be developed to help us find and treat NoV-associated diarrhea in clinical settings in a timely manner.

Novel Monoclonal Antibodies for Studies of Human and Rhesus Macaque Secretory Component and Human J-Chain

Immunoglobulin A (IgA) antibodies exist in monomeric, dimeric, and secretory forms. Dimerization of IgA depends on a 15-kD polypeptide termed "joining (J) chain," which is also part of the binding site for an epithelial glycoprotein called "secretory component (SC)," whether this after apical cleavage on secretory epithelia is ligand bound in secretory IgA (SIgA) or in a free form. Uncleaved membrane SC, also called the "polymeric Ig receptor," is thus crucial for transcytotic export of SIgA to mucosal surfaces, where it interacts with and modulates commensal bacteria and mediates protective immune responses against exogenous pathogens. To evaluate different forms of IgA, we have produced mouse monoclonal antibodies (MAbs) against human J-chain and free SC. We found that J-chain MAb 9A8 and SC MAb 9H7 identified human dimeric IgA and SIgA in enzyme-linked immunoassay and western blot analysis, as well as functioning in immunohistochemistry to identify cytoplasmic IgA of intestinal lamina propria plasmablasts/plasma cells and crypt epithelium of distal human intestine. Finally, we demonstrated that SC MAb 9H7 cross-reacted with rhesus macaque SIgA. These novel reagents should be of use in the study of the biology of various forms of IgA in humans and SIgA in macaques, as well as in monitoring the production and/or isolation of these forms of IgA.

Immune responses elicited against rotavirus middle layer protein VP6 inhibit viral replication in vitro and in vivo

Rotavirus (RV) is a common cause of severe gastroenteritis (GE) in children worldwide. Live oral RV vaccines protect against severe RVGE, but the immune correlates of protection are not yet clearly defined. Inner capsid VP6 protein is a highly conserved, abundant, and immunogenic RV protein, and VP6-specific mucosal antibodies, especially IgA, have been implicated to protect against viral challenge in mice. In the present study systemic and mucosal IgG and IgA responses were induced by immunizing BALB/c mice intranasally with a combination of recombinant RV VP6 protein (subgroup II [SGII]) and norovirus (NoV) virus-like particles (VLPs) used in a candidate vaccine. Following immunization mice were challenged orally with murine RV strain EDIMwt (SG non-I-non-II, G3P10[16]). In order to determine neutralizing activity of fecal samples, sera, and vaginal washes (VW) against human Wa RV (SGII, G1P1A[8]) and rhesus RV (SGI, G3P5B[3]), the RV antigen production was measured with an ELISA-based antigen reduction neutralization assay. Only VWs of immunized mice inhibited replication of both RVs, indicating heterotypic protection of induced antibodies. IgA antibody depletion and blocking experiments using recombinant VP6 confirmed that neutralization was mediated by anti-VP6 IgA antibodies. Most importantly, after the RV challenge significant reduction in viral shedding was observed in feces of immunized mice. These results suggest a significant role for mucosal RV VP6-specific IgA for the inhibition of RV replication in vitro and in vivo. In addition, these results underline the importance of non-serotype-specific immunity induced by the conserved subgroup-specific RV antigen VP6 in clearance of RV infection.

Role of noroviruses as aetiological agents of diarrhoea in developing countries

Diarrhoea is considered to be the second leading cause of death due to infections among children  < 5 years of age worldwide that may be caused by bacteria, parasites, viruses and non-infectious agents. The major causative agents of diarrhoea in developing countries may vary from those in developed countries. Noroviruses are considered to be the most common cause of acute diarrhoea in both children and adults in industrialized countries. On the other hand, there is a lack of comprehensive epidemiological evidence from developing countries that norovirus is a major cause of diarrhoea. In these regions, asymptomatic norovirus infections are very common, and similar detection rates have been observed in patients with diarrhoea and asymptomatic persons. This review summarizes the current knowledge of norovirus infection in developing countries and seeks to position infections with noroviruses among those of other enteropathogens in terms of disease burden in these regions.

Vertically transmitted faecal IgA levels determine extra-chromosomal phenotypic variation

The proliferation of genetically modified mouse models has exposed phenotypic variation between investigators and institutions that has been challenging to control. In many cases, the microbiota is the presumed cause of the variation. Current solutions to account for phenotypic variability include littermate and maternal controls or defined microbial consortia in gnotobiotic mice. In conventionally raised mice, the microbiome is transmitted from the dam. Here we show that microbially driven dichotomous faecal immunoglobulin-A (IgA) levels in wild-type mice within the same facility mimic the effects of chromosomal mutations. We observe in multiple facilities that vertically transmissible bacteria in IgA-low mice dominantly lower faecal IgA levels in IgA-high mice after co-housing or faecal transplantation. In response to injury, IgA-low mice show increased damage that is transferable by faecal transplantation and driven by faecal IgA differences. We find that bacteria from IgA-low mice degrade the secretory component of secretory IgA as well as IgA itself. These data indicate that phenotypic comparisons between mice must take into account the non-chromosomal hereditary variation between different breeders. We propose faecal IgA as one marker of microbial variability and conclude that co-housing and/or faecal transplantation enables analysis of progeny from different dams.

The role of type I interferons in intestinal infection, homeostasis, and inflammation

Type I interferons are a widely expressed family of effector cytokines that promote innate antiviral and antibacterial immunity. Paradoxically, they can also suppress immune responses by driving production of anti-inflammatory cytokines, and dysregulation of these cytokines can contribute to host-mediated immunopathology and disease progression. Recent studies describe their anti-inflammatory role in intestinal inflammation and the locus containing IFNAR, a heterodimeric receptor for the type I interferons has been identified as a susceptibility region for human inflammatory bowel disease. This review focuses on the role of type I IFNs in the intestine in health and disease and their emerging role as immune modulators. Clear understanding of type I IFN-mediated immune responses may provide avenues for fine-tuning existing IFN treatment for infection and intestinal inflammation.

Human astroviruses

Human astroviruses (HAtVs) are positive-sense single-stranded RNA viruses that were discovered in 1975. Astroviruses infecting other species, particularly mammalian and avian, were identified and classified into the genera Mamastrovirus and Avastrovirus. Through next-generation sequencing, many new astroviruses infecting different species, including humans, have been described, and the Astroviridae family shows a high diversity and zoonotic potential. Three divergent groups of HAstVs are recognized: the classic (MAstV 1), HAstV-MLB (MAstV 6), and HAstV-VA/HMO (MAstV 8 and MAstV 9) groups. Classic HAstVs contain 8 serotypes and account for 2 to 9% of all acute nonbacterial gastroenteritis in children worldwide. Infections are usually self-limiting but can also spread systemically and cause severe infections in immunocompromised patients. The other groups have also been identified in children with gastroenteritis, but extraintestinal pathologies have been suggested for them as well. Classic HAstVs may be grown in cells, allowing the study of their cell cycle, which is similar to that of caliciviruses. The continuous emergence of new astroviruses with a potential zoonotic transmission highlights the need to gain insights on their biology in order to prevent future health threats. This review focuses on the basic virology, pathogenesis, host response, epidemiology, diagnostic assays, and prevention strategies for HAstVs.