MZB1 folding and unfolding the role of IgA

Combination adjuvant improves influenza virus immunity by downregulation of immune homeostasis genes in lymphocytes

Adjuvants play a central role in enhancing the immunogenicity of otherwise poorly immunogenic vaccine antigens. Combining adjuvants has the potential to enhance vaccine immunogenicity compared with single adjuvants, although the cellular and molecular mechanisms of combination adjuvants are not well understood. Using the influenza virus hemagglutinin H5 antigen, we define the immunological landscape of combining CpG and MPLA (TLR-9 and TLR-4 agonists, respectively) with a squalene nanoemulsion (AddaVax) using immunologic and transcriptomic profiling. Mice immunized and boosted with recombinant H5 in AddaVax, CpG+MPLA, or AddaVax plus CpG+MPLA (IVAX-1) produced comparable levels of neutralizing antibodies and were equally well protected against the H5N1 challenge. However, after challenge with H5N1 virus, H5/IVAX-1-immunized mice had 100- to 300-fold lower virus lung titers than mice receiving H5 in AddaVax or CpG+MPLA separately. Consistent with enhanced viral clearance, unsupervised expression analysis of draining lymph node cells revealed the combination adjuvant IVAX-1 significantly downregulated immune homeostasis genes, and induced higher numbers of antibody-producing plasmablasts than either AddaVax or CpG+MPLA. IVAX-1 was also more effective after single-dose administration than either AddaVax or CpG+MPLA. These data reveal a novel molecular framework for understanding the mechanisms of combination adjuvants, such as IVAX-1, and highlight their potential for the development of more effective vaccines against respiratory viruses.

Puerarin attenuates myocardial ischemic injury and endoplasmic reticulum stress by upregulating the Mzb1 signal pathway

Objective

This study investigated the role of Mzb1 in puerarin protection against heart injury and dysfunction in acute myocardial infarction (AMI) mice.

Methods

C57BL/6 mice were pretreated with and without puerarin at doses of 50 mg/kg and 100 mg/kg for 14 days before establishing the AMI model. An AMI model was induced by ligating the left descending anterior coronary artery, and AC16 cardiomyocytes were treated with H2O2 in vitro. Echocardiography was performed to measure cardiac function. DHE staining, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase assay, and DCFH-DA oxidative fluorescence staining were used to determine reactive oxygen species (ROS) production in vivo and in vitro. Bioinformatics analysis was used to predict potential upstream transcription factors of Mzb1.

Results

Puerarin dose-dependently reduced myocardial infarction area and injury, accompanied by the improvement of cardiac function in AMI mice. AMI mice manifested an increase in myocardial oxidative stress, endoplasmic reticulum (ER) stress, apoptosis, and mitochondrial biogenesis dysfunction, which were inhibited by pretreatment with puerarin. Puerarin also prevented Mzb1 downregulation in the hearts of AMI mice or H2O2-treated AC16 cells. Consistent with the in vivo findings, puerarin inhibited H2O2-induced cardiomyocyte apoptosis, ER stress, and mitochondrial dysfunction, which were attenuated by siRNA Mzb1. Furthermore, the JASPAR website predicted that KLF4 may be a transcription factor for Mzb1. The expression of KLF4 was partially reversed by puerarin in the cardiomyocyte injury model, and KLF4 inhibitor (kenpaullone) inhibited Mzb1 expression and affected its function.

Conclusion

These results suggest that puerarin can protect against cardiac injury by attenuating oxidative stress and endoplasmic reticulum stress through upregulating the KLF4/Mzb1 pathway and that puerarin may expand our armamentarium for the prevention and treatment of ischemic heart diseases.

MZB1 regulates cellular proliferation, mitochondrial dysfunction, and inflammation and targets the PI3K-Akt signaling pathway in acute pancreatitis

BACKGROUND

Acute pancreatitis (AP) is a pathological condition characterized by the premature release and activation of trypsinogens and other enzyme precursors. In severe cases, the mortality rates are in the range of 20-30% and may even be as high as 50%. Though various prophylaxes are available for AP, the mechanism of its progression is unclear. Marginal zone B and B-1 cell-specific protein 1 (MZB1) is found in the endoplasmic reticulum (ER) where it is expressed exclusively in the B cells there. MZB1 promotes proliferation, inhibits apoptosis, invasion, and inflammation, and mitigates mitochondrial damage in cells. However, the importance of MZB1 in AP has not yet been determined.

METHODS

Differentially expressed genes (DEGs) between healthy pancreatic cells and those affected by AP were identified using datasets from Gene Expression Omnibus (GEO) datasets. Relative differences in MZB1 expression between normal and diseased tissues and cells were validated in vivo using a rat AP model induced with 4% (w/v) sodium taurocholate and in vitro using the AR42J rat pancreatic cell line exposed to caerulein (CAE). Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2`-deoxyuridine (EdU) assays were performed to detect and compare normal and pathological cell proliferation. Flow cytometry was employed to assess and compare cellular apoptosis. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot (WB) were applied to evaluate the apoptotic factors Bax and Bcl. The inflammatory factors interleukin (IL)-6 and IL-1β were quantified using Enzyme-linked immunosorbent assay (ELISA) and qRT-PCR techniques. Mitochondrial function was evaluated using assays for reactive oxygen species (ROS) and tetramethylrhodamine methyl ester (TMRM). WB and qRT-PCR were utilized to measure the expression levels of the PI3K-Akt signaling pathway, followed by a rescue experiment involving the inhibitor of wortmannin.

RESULTS

MZB1 was upregulated in the AP cases screened from the GEO datasets, the rat AP model, and the AR42J cells exposed to CAE. Overexpression of MZB1 enhanced the growth and supressed the cell death of AR42J cells while also activating the PI3K-Akt signaling pathway. MZB1 knockdown led to mitochondrial dysfunction and exacerbated inflammation. The rescue experiment demonstrated that MZB1 enhanced proliferation and inhibited apoptosis, mitochondrial dysfunction, and inflammation in pancreatic cells through the PI3K-Akt pathway.

CONCLUSIONS

AP cells and tissues exhibited markedly elevated levels of MZB1 expression compared to their healthy counterparts. MZB1 overexpression promoted proliferation and supressed apoptosis, mitochondrial dysfunction, and inflammation in pancreatic cells through the positive regulation of the PI3K-Akt signaling pathway.

Correlation between Monocyte Gene Expression and Inflammation on Brain Imaging in Patients with Solitary Cerebral Cysticercus Granuloma

Prior work has shown that 14 monocyte genes are upregulated in patients with different forms of parenchymal neurocysticercosis, including solitary cysticercus granuloma (SCG). The aim of this study was to investigate whether changes in inflammation associated with SCG seen on follow-up brain imaging are also reflected in changes in expression of these 14 genes. Peripheral blood CD14+ monocytes were isolated from 20 patients with SCG at initial diagnosis and at clinical and imaging follow-up of 6 months or more. Expressions of 14 target monocyte genes were determined by quantitative polymerase chain reaction at each visit. At a median follow-up of 14 months, the SCG had resolved in 11 patients, was persistent in four patients, and had calcified in five patients. Edema seen in the initial imaging in 17 patients had resolved in 15 patients and was markedly reduced in two patients. The expression levels of the monocyte genes LRRFIP2, TAXIBP1, and MZB1 were significantly lower at follow-up, regardless of the status of SCG on follow-up imaging. Our findings show that expression levels of monocyte genes involved with inflammatory processes decrease in patients with SCG concomitant with follow-up imaging that reveals a reduction in inflammation as revealed by complete or near-complete resolution of edema, as well as resolution or reduction in the enhancement of the granuloma.

Delayed boosting improves human antigen-specific Ig and B cell responses to the RH5.1/AS01B malaria vaccine

Modifications to vaccine delivery that increase serum antibody longevity are of great interest for maximizing efficacy. We have previously shown that a delayed fractional (DFx) dosing schedule (0-1-6 month) - using AS01B-adjuvanted RH5.1 malaria antigen - substantially improves serum IgG durability as compared with monthly dosing (0-1-2 month; NCT02927145). However, the underlying mechanism and whether there are wider immunological changes with DFx dosing were unclear. Here, PfRH5-specific Ig and B cell responses were analyzed in depth through standardized ELISAs, flow cytometry, systems serology, and single-cell RNA-Seq (scRNA-Seq). Data indicate that DFx dosing increases the magnitude and durability of circulating PfRH5-specific B cells and serum IgG1. At the peak antibody magnitude, DFx dosing was distinguished by a systems serology feature set comprising increased FcRn binding, IgG avidity, and proportion of G2B and G2S2F IgG Fc glycans, alongside decreased IgG3, antibody-dependent complement deposition, and proportion of G1S1F IgG Fc glycan. Concomitantly, scRNA-Seq data show a higher CDR3 percentage of mutation from germline and decreased plasma cell gene expression in circulating PfRH5-specific B cells. Our data, therefore, reveal a profound impact of DFx dosing on the humoral response and suggest plausible mechanisms that could enhance antibody longevity, including improved FcRn binding by serum Ig and a potential shift in the underlying cellular response from circulating short-lived plasma cells to nonperipheral long-lived plasma cells.

Role of Polymeric Immunoglobulin Receptor in IgA and IgM Transcytosis

Transcytosis of polymeric IgA and IgM from the basolateral surface to the apical side of the epithelium and subsequent secretion into mucosal fluids are mediated by the polymeric immunoglobulin receptor (pIgR). Secreted IgA and IgM have vital roles in mucosal immunity in response to pathogenic infections. Binding and recognition of polymeric IgA and IgM by pIgR require the joining chain (J chain), a small protein essential in the formation and stabilization of polymeric Ig structures. Recent studies have identified marginal zone B and B1 cell-specific protein (MZB1) as a novel regulator of polymeric IgA and IgM formation. MZB1 might facilitate IgA and IgM transcytosis by promoting the binding of J chain to Ig. In this review, we discuss the roles of pIgR in transcytosis of IgA and IgM, the roles of J chain in the formation of polymeric IgA and IgM and recognition by pIgR, and focus particularly on recent progress in understanding the roles of MZB1, a molecular chaperone protein.

The structures of secretory and dimeric immunoglobulin A

Secretory (S) Immunoglobulin (Ig) A is the predominant mucosal antibody, which binds pathogens and commensal microbes. SIgA is a polymeric antibody, typically containing two copies of IgA that assemble with one joining-chain (JC) to form dimeric (d) IgA that is bound by the polymeric Ig-receptor ectodomain, called secretory component (SC). Here, we report the cryo-electron microscopy structures of murine SIgA and dIgA. Structures reveal two IgAs conjoined through four heavy-chain tailpieces and the JC that together form a β-sandwich-like fold. The two IgAs are bent and tilted with respect to each other, forming distinct concave and convex surfaces. In SIgA, SC is bound to one face, asymmetrically contacting both IgAs and JC. The bent and tilted arrangement of complex components limits the possible positions of both sets of antigen-binding fragments (Fabs) and preserves steric accessibility to receptor-binding sites, likely influencing antigen binding and effector functions.