Isolation of novel simian adenoviruses from macaques for development of a vector for human gene therapy and vaccines.

IMPORTANCE: Adenoviruses are widely used in gene therapy and vaccine delivery. Due to the high prevalence of human adenoviruses (HAdVs), the pre-existing immunity against HAdVs in humans is common, which limits the wide and repetitive use of HAdV vectors. In contrast, the pre-existing immunity against simian adenoviruses (SAdVs) is low in humans. Therefore, we performed epidemiological investigations of SAdVs in simians and found that the SAdV prevalence was as high as 33.9%. The whole-genome sequencing and sequence analysis showed SAdV diversity and possible cross species transmission. One isolate with low level of pre-existing neutralizing antibodies in humans was used to construct replication-deficient SAdV vectors with E4orf6 substitution and E1/E3 deletion. Interestingly, we found that the E3 region plays a critical role in its replication in human cells, but the absence of this region could be compensated for by the E4orf6 from HAdV-5 and the E1 expression intrinsic to HEK293 cells.

Intestinal Microbiota of Mice Influences Resistance to Staphylococcus aureus Pneumonia.

Th17 immunity in the gastrointestinal tract is regulated by the intestinal microbiota composition, particularly the presence of segmented filamentous bacteria (sfb), but the role of the intestinal microbiota in pulmonary host defense is not well explored. We tested whether altering the gut microbiota by acquiring sfb influences the susceptibility to staphylococcal pneumonia via induction of type 17 immunity. Groups of C57BL/6 mice which differed in their intestinal colonization with sfb were challenged with methicillin-resistant Staphylococcus aureus in an acute lung infection model. Bacterial burdens, bronchoalveolar lavage fluid (BALF) cell counts, cell types, and cytokine levels were compared between mice from different vendors, mice from both vendors after cohousing, mice given sfb orally prior to infection, and mice with and without exogenous interleukin-22 (IL-22) or anti-IL-22 antibodies. Mice lacking sfb developed more severe S. aureus pneumonia than mice colonized with sfb, as indicated by higher bacterial burdens in the lungs, lung inflammation, and mortality. This difference was reduced when sfb-negative mice acquired sfb in their gut microbiota through cohousing with sfb-positive mice or when given sfb orally. Levels of type 17 immune effectors in the lung were higher after infection in sfb-positive mice and increased in sfb-negative mice after acquisition of sfb, as demonstrated by higher levels of IL-22 and larger numbers of IL-22(+) TCRß(+) cells and neutrophils in BALF. Exogenous IL-22 protected mice from S. aureus pneumonia. The murine gut microbiota, particularly the presence of sfb, promotes pulmonary type 17 immunity and resistance to S. aureus pneumonia, and IL-22 protects against severe pulmonary staphylococcal infection.

Th17-stimulating protein vaccines confer protection against Pseudomonas aeruginosa pneumonia.

RATIONALE: New vaccine approaches are needed for Pseudomonas aeruginosa, which continues to be a major cause of serious pulmonary infections. Although Th17 cells can protect against gram-negative pathogens at mucosal surfaces, including the lung, the bacterial proteins recognized by Th17 cells are largely unknown and could be potential new vaccine candidates. OBJECTIVES: We describe a strategy to identify Th17-stimulating protein antigens of Pseudomonas aeruginosa to assess their efficacy as vaccines against pneumonia. METHODS: Using a library of in vitro transcribed and translated P. aeruginosa proteins, we screened for Th17-stimulating antigens by coculturing the library proteins with splenocytes from mice immunized with a live-attenuated P. aeruginosa vaccine that is protective via Th17-based immunity. We measured antibody and Th17 responses after intranasal immunization of mice with the purified proteins mixed with the Th17 adjuvant curdlan, and we tested the protective efficacy of vaccination in a murine model of acute pneumonia. MEASUREMENTS AND MAIN RESULTS: The proteins PopB, FpvA, FptA, OprL, and PilQ elicited strong IL-17 secretion in the screen, and purified versions of PopB, FpvA, and OprL stimulated high IL-17 production from immune splenocytes. Immunization with PopB, which is a highly conserved component of the type III secretion system and a known virulence factor, elicited Th17 responses and also enhanced clearance of P. aeruginosa from the lung and spleen after challenge. PopB-immunized mice were protected from lethal pneumonia in an antibody-independent, IL-17-dependent manner. CONCLUSIONS: Screening for Th17-stimulating protein antigens identified PopB as a novel and promising vaccine candidate for P. aeruginosa.

Distinct roles of adenylyl cyclase VII in regulating the immune responses in mice.

The second messenger cAMP plays a critical role in regulating immune responses. Although well known for its immunosuppressive effect, cAMP is also required for the development of optimal immune responses. Thus, the regulation of this second messenger needs to be finely tuned and well balanced in a context dependent manner. To further understand the role of cAMP synthesis in the functions of the immune system, we focus on a specific adenylyl cyclase (AC) isoform, AC VII (AC7), which is highly expressed in the immune system. We show that mice deficient of AC7 are hypersensitive to LPS-induced endotoxic shock. Macrophages from AC7-deficient mice produce more of the proinflammatory cytokine, TNF-alpha, in response to LPS. The inability to generate intracellular cAMP response to serum factors, such as lysophosphatidic acid, is a potential cause for this phenotype. Thus, AC7 functions to control the extent of immune responses toward bacterial infection. However, it is also required for the optimal functions of B and T cells during adaptive immune responses. AC7 is the major isoform that regulates cAMP synthesis in both B and T cells. AC7-deficient mice display compromised Ab responses toward both T cell-independent and T cell-dependent Ags. The generation of memory T cells is also reduced. These results are the first to ascribe specific functions to an AC isoform in the immune system and emphasize the importance of cAMP synthesis by this isoform in shaping the immune responses.

Altered Lipid Profile in COVID-19 Patients and Metabolic Reprogramming.

Background: Coronavirus disease 2019 (COVID-19) is a global pandemic. Previous studies have reported dyslipidemia in patients with COVID-19. Herein, we conducted a retrospective study and a bioinformatics analysis to evaluate the essential data of the lipid profile as well as the possible mechanism in patients with COVID-19. Methods: First of all, the retrospective study included three cohorts: patients with COVID-19, a healthy population, and patients with chronic obstructive pulmonary disease (COPD). For each subject, serum lipid profiles in the biochemical data were compared, including triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). Furthermore, bioinformatics analyses were performed for exploring the biological or immunological mechanisms. Results: In line with the biochemical data of the three cohorts, the statistical result displayed that patients with COVID-19 were more likely to have lower levels of TC and HDL-C as compared with healthy individuals. The differential proteins associated with COVID-19 are involved in the lipid pathway and can target and regulate cytokines and immune cells. Additionally, a heatmap revealed that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections were possibly involved in lipid metabolic reprogramming. The viral proteins, such as spike (S) and non-structural protein 2 (Nsp2) of SARS-CoV-2, may be involved in metabolic reprogramming. Conclusion: The metabolic reprogramming after SARS-CoV-2 infections is probably associated with the immune and clinical phenotype of patients. Hence, metabolic reprogramming may be targeted for developing antivirals against COVID-19.

Tracking SARS-CoV-2 Omicron diverse spike gene mutations identifies multiple inter-variant recombination events.

The current pandemic of COVID-19 is fueled by more infectious emergent Omicron variants. Ongoing concerns of emergent variants include possible recombinants, as genome recombination is an important evolutionary mechanism for the emergence and re-emergence of human viral pathogens. In this study, we identified diverse recombination events between two Omicron major subvariants (BA.1 and BA.2) and other variants of concern (VOCs) and variants of interest (VOIs), suggesting that co-infection and subsequent genome recombination play important roles in the ongoing evolution of SARS-CoV-2. Through scanning high-quality completed Omicron spike gene sequences, 18 core mutations of BA.1 (frequency >99%) and 27 core mutations of BA.2 (nine more than BA.1) were identified, of which 15 are specific to Omicron. BA.1 subvariants share nine common amino acid mutations (three more than BA.2) in the spike protein with most VOCs, suggesting a possible recombination origin of Omicron from these VOCs. There are three more Alpha-related mutations in BA.1 than BA.2, and BA.1 is phylogenetically closer to Alpha than other variants. Revertant mutations are found in some dominant mutations (frequency >95%) in the BA.1. Most notably, multiple characteristic amino acid mutations in the Delta spike protein have been also identified in the "Deltacron"-like Omicron Variants isolated since November 11, 2021 in South Africa, which implies the recombination events occurring between the Omicron and Delta variants. Monitoring the evolving SARS-CoV-2 genomes especially for recombination is critically important for recognition of abrupt changes to viral attributes including its epitopes which may call for vaccine modifications.

Vascular endothelial growth inhibitor (VEGI; TNFSF15) inhibits bone marrow-derived endothelial progenitor cell incorporation into Lewis lung carcinoma tumors.

Bone marrow (BM)-derived endothelial progenitor cells (EPC) have a critical role in tumor neovascularization. Vascular endothelial growth inhibitor (VEGI) is a member of the TNF superfamily (TNFSF15). We have shown that recombinant VEGI suppresses tumor angiogenesis by specifically eliminating proliferating endothelial cells (EC). We report here that treatment of tumor bearing mice with recombinant VEGI leads to a significantly decreased population of BM-derived EPC in the tumors. We transplanted whole bone marrow from green fluorescent protein (GFP) transgenic mice into C57BL/6 recipient mice, which were then inoculated with Lewis lung carcinoma (LLC) cells. Intraperitoneal injection of recombinant VEGI led to significant inhibition of tumor growth and decrease of vasculature density compared to vehicle-treated mice. Tumor implantation yielded a decrease of BM-derived EPC in the peripheral blood, while VEGI-treatment resulted in an initial delay of such decrease. Analysis of the whole bone marrow showed a decrease of Lin(-)-c-Kit(+)-Sca-1(+) hematopoietic stem cell (HSC) population in tumor bearing mice; however, VEGI-treatment caused a significant increase of this cell population. In addition, the number of BM-derived EPC in VEGI-treated tumors was notably less than that in the vehicle-treated group, and most of the apoptotic cells in the VEGI-treated tumors were of bone marrow origin. These findings indicate that VEGI inhibits BM-derived EPC mobilization and prevents their incorporation into LLC tumors by inducing apoptosis specifically of BM-derived cells, resulting in the inhibition of EPC-supported tumor vasculogenesis and tumor growth.

Intrafollicular location of marginal zone/CD1d(hi) B cells is associated with autoimmune pathology in a mouse model of lupus.

Marginal zone (MZ) B cells contain a large number of autoreactive clones and the expansion of this compartment has been associated with autoimmunity. MZ B cells also efficiently transport blood-borne antigen to the follicles where they activate T cells and differentiate into plasma cells. Using the B6.NZM2410.Sle1.Sle2.Sle3 (B6.TC) model of lupus, we show that the IgM+ CD1d(hi)/MZ B-cell compartment is expanded, and a large number of them reside inside the follicles. Contrary to the peripheral B-cell subset distribution and their activation status, the intrafollicular location of B6.TC IgM+ CD1d(hi)/MZ B cells depends on both bone marrow- and stromal-derived factors. Among the factors responsible for this intrafollicular location, we have identified an increased response to CXCL13 by B6.TC MZ B cells and a decreased expression of VCAM-1 on stromal cells in the B6.TC MZ. However, the reduced number of MZ macrophages observed in B6.TC MZs was independent of the IgM+ CD1d(hi)/B-cell location. B7-2 but not B7-1 deficiency restored IgM+ CD1d(hi)/MZ B-cell follicular exclusion in B6.TC mice, and it correlated with tolerance to dsDNA and a significant reduction of autoimmune pathology. These results suggest that follicular exclusion of IgM+ CD1d(hi)/MZ B cells is an important B-cell tolerance mechanism, and that B7-2 signaling is involved in breaching this tolerance checkpoint.

PLGA-encapsulation of the Pseudomonas aeruginosa PopB vaccine antigen improves Th17 responses and confers protection against experimental acute pneumonia.

The Pseudomonas aeruginosa type III secretion system protein PopB and its chaperon protein PcrH, when co-administered with the adjuvant curdlan, elicit Th17 responses after intranasal immunization of mice. These PopB/PcrH-curdlan vaccines protect mice against acute lethal pneumonia in an IL-17-dependent fashion involving CD4 helper T cells secreting IL-17 (Th17 cells). In this study, we tested whether encapsulation of PopB/PcrH in poly-lactic-co-glycolic acid (PLGA) nanoparticles could elicit Th17 responses to PopB. Recombinant PopB/PcrH or PcrH alone was encapsulated into PLGA nanoparticles. Mice (FVB/N) were intranasally immunized with the PLGA-PopB/PcrH nanoparticles, PLGA-PcrH nanoparticles, PLGA alone, or PopB/PcrH alone. The protective efficacy was assessed in an acute lung infection model with a lethal dose of an ExoU-producing version of P. aeruginosa strain PAO1. Th17 responses were assayed by intracellular flow cytometry and by ELISA for IL-17 in supernatants of splenocytes co-cultured with purified PopB/PcrH. PLGA-PopB/PcrH-immunized mice showed 3-4-fold higher Th17 responses both in the lung and in the spleen compared to mice immunized with empty PLGA or PopB/PcrH alone. After challenge with P. aeruginosa, PLGA-PopB/PcrH-immunized mice showed significantly lower bacterial counts in the lungs and improved survival. In conclusion, encapsulation of PopB/PcrH in PLGA nanoparticles can elicit Th17 responses to intranasal vaccination and protect mice against acute lethal P. aeruginosa pneumonia.

Genetics of autoreactive B cells.

It is now well-accepted that autoimmune diseases develop as a result of interactions between a complex genetic basis and environmental triggers. Autoreactive B cells play a major role in many autoimmune diseases, by secreting autoantibodies or cytokines and/or presenting auto-antigens to T cells. Studies performed with human patients and murine models have accumulated evidence that B-cell autoreactivity, or its manifestation as the presence of autoantibodies, are also supported by multiple genetic determinants. These studies will be summarized in this review and presented in a critical perspective of the approaches used to obtain these results, and their significance for our understanding of B-cell tolerance.

SDF-1/CXCR4 axis modulates bone marrow mesenchymal stem cell apoptosis, migration and cytokine secretion.

Bone marrow mesenchymal stem cells (MSCs) are considered as a promising cell source to treat the acute myocardial infarction. However, over 90% of the stem cells usually die in the first three days of transplantation. Survival potential, migration ability and paracrine capacity have been considered as the most important three factors for cell transplantation in the ischemic cardiac treatment. We hypothesized that stromal-derived factor-1 (SDF-1)/CXCR4 axis plays a critical role in the regulation of these processes. In this study, apoptosis was induced by exposure of MSCs to H(2)O(2) for 2 h. After re-oxygenation, the SDF-1 pretreated MSCs demonstrated a significant increase in survival and proliferation. SDF-1 pretreatment also enhanced the migration and increased the secretion of pro-survival and angiogenic cytokines including basic fibroblast growth factor and vascular endothelial growth factor. Western blot and RT-PCR demonstrated that SDF-1 pretreatment significantly activated the pro-survival Akt and Erk signaling pathways and up-regulated Bcl-2/Bax ratio. These protective effects were partially inhibited by AMD3100, an antagonist of CXCR4.We conclude that the SDF-1/CXCR4 axis is critical for MSC survival, migration and cytokine secretion.

Direct B cell stimulation by dendritic cells in a mouse model of lupus.

OBJECTIVE: Dendritic cells (DCs) play a major role in regulating lymphocytes, including B cells, and defective DC functions have been implicated in lupus. The purpose of this study was to assess the contribution of DCs to B cell hyperactivity in the B6.Sle1.Sle2.Sle3 (B6.TC) murine lupus model. METHODS: We compared the effects of B6 and B6.TC bone marrow-derived DCs on naive B cells cocultured in the presence of lipopolysaccharide (LPS), anti-CD40, or anti-IgM. We measured the proliferation, antibody production, and expression of activation markers and chemokine receptors for the B cells, as well as DC cytokine production. B cell proliferation was also assessed in Transwell experiments and in response to activated DC supernatants or exosomes. The role of DC-produced cytokines was evaluated with blocking antibodies and transgenic mice. RESULTS: LPS-stimulated or anti-CD40-stimulated DCs from B6.TC mice increased B cell proliferation, antibody production, and chemokine receptor expression as compared with DCs from B6 mice. Cell-to-cell contact was not necessary for the augmented effect of the lupus-prone DCs. Anti-CD40 treatment induced a higher production of interleukin-6 (IL-6), soluble IL-6 receptor (sIL-6R), IL-10, and tumor necrosis factor alpha in B6.TC DCs. Blocking these individual cytokines, however, did not abrogate the effects of B6.TC DCs. Additional experiments also ruled out involvement of BAFF, IL-12, and interferon-alpha. CONCLUSION: Activated DCs from B6.TC mice directly increase B cell effector functions. This effect depends on soluble factors released by activated DCs, but none of the single major DC-produced cytokines known to affect B cells are necessary. Increased sIL-6R production suggests that increased sensitivity to IL-6 may be involved.

Lupus resistance is associated with marginal zone abnormalities in an NZM murine model.

The NZM2410 and NZM TAN (TAN) are two of 27 inbred strains derived from an intercross between the NZW and NZB strains. NZM2410 mice develop a highly penetrant lupus nephritis mediated by three susceptibility loci, Sle1, Sle2 and Sle3. These three loci have been combined on a C57BL/6 background in a triple congenic strain that reconstitutes the NZM2410 autoimmune phenotype. Remarkably, inspite of the presence of Sle1, Sle2 and Sle3, TAN mice display a mild autoimmune phenotype reminiscent of NZW. Contrary to the lupus-prone strains, the majority of TAN CD4(+) T cells are in a naïve-inactivated stage. TAN mice show B-cell developmental abnormalities similar to lupus-prone mice, such an accumulation of transitional T1 cells and peritoneal B-1a cells. TAN mice show, however, a unique expansion of the splenic marginal zone, in which B cells express high levels of CD5 and CD9, fail to migrate to the follicles in response to LPS, and show sub-optimal binding of T-independent type 2 antigens. Therefore, TAN mice present a functional silencing of marginal zone B cells, which have been previously implicated with autoimmune process. The TAN strain thus provides a novel model for the analysis of the genetic determinants of B-cell autoreactivity.

STAT4 deficiency reduces autoantibody production and glomerulonephritis in a mouse model of lupus.

To determine the respective role of the IL-12 and IL-4 pathways in the pathogenesis of systemic lupus erythematosus, we bred the Stat4 and Stat6 null alleles onto the lupus-prone mouse B6.TC, which is a congenic derivative of NZM2410. This model is characterized by abnormal splenocyte expansion, distribution and architecture, T cell activation, peripheral B cell development, production of anti-nuclear antibodies, and proliferative glomerulonephritis. STAT4 deficiency normalized the expression of each of these disease markers toward or to C57BL/6 levels. In contrast, STAT6 deficiency impacted splenocyte expansion and architecture, T cell activation, and anti-nuclear autoantibody production, but without any significant effect on B cell development or renal pathology. These results show that the IL-12/STAT4 pathway is involved in multiple disease-associated phenotypes in the B6.TC mouse. In contrast, the IL-4/STAT6 pathway regulates only a subset of disease markers that did not affect renal pathology.

Genetic dissection of the murine lupus susceptibility locus Sle2: contributions to increased peritoneal B-1a cells and lupus nephritis map to different loci.

Lupus pathogenesis in the NZM2410 mouse model results from the expression of multiple interacting susceptibility loci. Sle2 on chromosome 4 was significantly linked to glomerulonephritis in a linkage analysis of a NZM2410 x B6 cross. Yet, Sle2 expression alone on a C57BL/6 background did not result in any clinical manifestation, but in an abnormal B cell development, including the accumulation of B-1a cells in the peritoneal cavity and spleen. Analysis of B6.Sle2 congenic recombinants showed that at least three independent loci, New Zealand White-derived Sle2a and Sle2b, and New Zealand Black-derived Sle2c, contribute to an elevated number of B-1a cells, with Sle2c contribution being the strongest of the three. To determine the contribution of these three Sle2 loci to lupus pathogenesis, we used a mapping by genetic interaction strategy, in which we bred them to B6.Sle1.Sle3 mice. We then compared the phenotypes of these triple congenic mice with that of previously characterized B6.Sle1.Sle2.Sle3, which express the entire Sle2 interval in combination with Sle1 and Sle3. Sle2a and Sle2b, but not Sle2c, contributed significantly to lupus pathogenesis in terms of survival rate, lymphocytic expansion, and kidney pathology. These results show that the Sle2 locus contains several loci affecting B cell development, with only the two NZW-derived loci having the least effect of B-1a cell accumulation significantly contributing to lupus pathogenesis.

A genetic lesion that arrests plasma cell homing to the bone marrow.

The coordinated regulation of chemokine responsiveness plays a critical role in the development of humoral immunity. After antigen challenge and B cell activation, the emerging plasma cells (PCs) undergo CXCL12-induced chemotaxis to the bone marrow, where they produce Ab and persist. Here we show that PCs, but not B cells or T cells from lupus-prone NZM mice, are deficient in CXCL12-induced migration. PC unresponsiveness to CXCL12 results in a marked accumulation of PCs in the spleen of mice, and a concordant decrease in bone marrow PCs. Unlike normal mice, in NZM mice, a majority of the splenic PCs are long-lived. This deficiency is a consequence of the genetic interactions of multiple systemic lupus erythematosus susceptibility loci.