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Antibody-dependent enhancement (ADE) is an important safety concern for vaccine development against dengue virus (DENV) and its antigenically related Zika virus (ZIKV) because vaccine may prime deleterious antibodies to enhance natural infections. Cross-reactive antibodies targeting the conserved fusion loop epitope (FLE) are known as the main sources of ADE. We design ZIKV immunogens engineered to change the FLE conformation but preserve neutralizing epitopes. Single vaccination conferred sterilizing immunity against ZIKV without ADE of DENV-serotype 1-4 infections and abrogated maternal-neonatal transmission in mice. Unlike the wild-type-based vaccine inducing predominately cross-reactive ADE-prone antibodies, B cell profiling revealed that the engineered vaccines switched immunodominance to dispersed patterns without DENV enhancement. The crystal structure of the engineered immunogen showed the dimeric conformation of the envelope protein with FLE disruption. We provide vaccine candidates that will prevent both ZIKV infection and infection-/vaccination-induced DENV ADE.

In this paper, to improve the combustion characteristics and working performance of the solid fuel ramjet, a solid fuel ramjet with a gas generator is proposed. Based on k − ω SST and Eddy-Dissipation equations, the turbulent combustion model is established, and the internal flow field of the ramjet, as well as the regression rate, and species, were numerically analyzed. The results show that the temperature of the ramjet and the regression rate with a gas generator is increased. When the airflow is 0.4kg/s, the increase of the gas generator flow will lead to a more obvious regression rate increase, and the maximum value will increase by 33%. When the airflow is 0.6kg/s, the regression rate with the gas generator is evenly distributed along the axis. The flame with a gas generator makes the head burn more completely, the combustion chamber temperature increases, and the average regression rate of solid fuel increases by 14%.

Identifying

Zika virus (ZIKV)-specific T cells are activated by different peptides derived from virus structural and nonstructural proteins, and contributed to the viral clearance or protective immunity. Herein, we have depicted the profile of CD8+ and CD4+ T cell immunogenicity of ZIKV proteins in C57BL/6 (H-2b) and BALB/c (H-2d) mice, and found that featured cellular immunity antigens were variant among different murine alleles. In H-2b mice, the proteins E, NS2, NS3 and NS5 are recognized as immunodominant antigens by CD8+ T cells, while NS4 is dominantly recognized by CD4+ T cells. In contrast, in H-2d mice, NS1 and NS4 are the dominant CD8+ T cell antigen and NS4 as the dominant CD4+ T cell antigen, respectively. Among the synthesized 364 overlapping polypeptides spanning the whole proteome of ZIKV, we mapped 91 and 39 polypeptides which can induce ZIKV-specific T cell responses in H-2b and H-2d mice, respectively. Through the identification of CD8+ T cell epitopes, we found that immunodominant regions E294-302 and NS42351-2360 are hotspots epitopes with a distinct immunodominance hierarchy present in H-2b and H-2d mice, respectively. Our data characterized an overall landscape of the immunogenic spectrum of the ZIKV polyprotein, and provide useful insight into the vaccine development.

Antibody-dependent enhancement (ADE) is an important safety concern for vaccine development against dengue virus (DENV) and its antigenically related Zika virus (ZIKV) because vaccine may prime deleterious antibodies to enhance natural infections. Cross-reactive antibodies targeting the conserved fusion loop epitope (FLE) are known as the main sources of ADE. We design ZIKV immunogens engineered to change the FLE conformation but preserve neutralizing epitopes. Single vaccination conferred sterilizing immunity against ZIKV without ADE of DENV-serotype 1-4 infections and abrogated maternal-neonatal transmission in mice. Unlike the wild-type-based vaccine inducing predominately cross-reactive ADE-prone antibodies, B cell profiling revealed that the engineered vaccines switched immunodominance to dispersed patterns without DENV enhancement. The crystal structure of the engineered immunogen showed the dimeric conformation of the envelope protein with FLE disruption. We provide vaccine candidates that will prevent both ZIKV infection and infection-/vaccination-induced DENV ADE.

Helicobacter pylori is designated as a class I carcinogen of human gastric cancer following long-term infection. During this process, H. pylori bacteria persist in proliferation and death, and release bacterial components that come into contact with gastric epithelial cells and regulate host cell function. However, the impact of long-term exposure to H. pylori lysate on the pathological changes of gastric cells is not clear. In this study, we aimed to investigate the regulation and mechanisms involved in gastric cell dysfunction following continuous exposure to H. pylori lysate. We co-cultured gastric cell lines GES-1 and MKN-45 with H. pylori lysate for 30 generations, and we found that sustained exposure to H. pylori lysate inhibited GES-1 cell invasion, migration, autophagy, and apoptosis, while it did not inhibit MKN-45 cell invasion or migration. Furthermore, Mongolian gerbils infected with H. pylori ATCC 43504 strains for 90 weeks confirmed the in vitro results. The clinical and in vitro data indicated that sustained exposure to H. pylori lysate inhibited cell apoptosis and autophagy through the Nod1-NF-κB/MAPK-ERK/FOXO4 signaling pathway. In conclusion, sustained exposure to H. pylori lysate promoted proliferation of gastric epithelial cells and inhibited autophagy and apoptosis via Nod1-NF-κB/MAPK-ERK/FOXO4 signaling pathway. In the process of H. pylori-induced gastric lesions, H. pylori lysate plays as an “accomplice” to carcinogenesis.

An antibody defense against COVID-19 One of the responses of the immune system to invading viruses is the production of antibodies. Some of these are neutralizing, meaning that they prevent the virus from being infectious, and can thus be used to treat viral diseases. Wu et al. isolated four neutralizing antibodies from a convalescent coronavirus disease 2019 (COVID-19) patient. Two of the antibodies, B38 and H4, blocked the receptor binding domain (RBD) of the viral spike protein from binding to the cellular receptor, angiotensin-converting enzyme 2 (ACE2). The structure of the RBD bound to B38 shows that the B38-binding site overlaps with the binding site for ACE2. Although H4 also blocks RBD binding to ACE2, it binds at a different site, and thus the two antibodies can bind simultaneously. This pair of antibodies could potentially be used together in clinical applications. Science , this issue p. 1274

The energy non-closure near the land surface has been a key topic in the land surface processes research. The energy closure rate is still not high even after considering heat storage and photosynthesis energy consumption, while the contribution of advective energy to the closure rate needs to be considered further under the non-uniform underlying surface. In this paper, the advective energy caused by thermal heterogeneity of underlying surface is calculated by using the energy budget data collected from the Flower-Lake observation site in the Zoige Alpine Wetland in 2017, and the contribution of thermal advection to energy closure near the ground is estimated. The result shows: In summer of 2017, the maximum value of the advective heat flux was 23.8w/m2 at the Zoige alpine wetland. When the contribution of advective heat flux is introduced into the energy balance equation, the energy closure rate increases from 72.0% to 79.4%. With considering the contribution of horizontal heat transfer, it has a certain effect on improving energy closure rate for the flat terrain and thermal inhomogeneous underlying surface. The near surface thermal inhomogeneity leads to the accumulation of heat, which is the basic reason for the heat advection to affect the energy closure rate, and also an important reason for the difference between the wetland characteristics of water and heat exchange of the wetland with the other regions.Key words：Alpine wetland; eddy correlation; advective heat flux; energy closure rate; inhomogeneous land surface

Background Antimicrobial resistance and patient-to-patient transmission of Corynebacterium striatum ( C. striatum ) clinical strains were frequently reported in recent years. Even worse, daptomycin resistant isolates were found in some studies and possible resistance mechanism was explored. Also, few investigations revealed the diversity of resistance feature and potential pathogenicity of C. striatum strains with different genotypes. However, less is known about the possible differences of resistance feature and pathogenicity of C. straitum clinical strains from different hospitals at a long distance.Methods C. striatum clinical strains were isolated and identified with VITEK-2 ANC card, MALDI-TOF microTyper and 16S rRNA sequencing technique. Broth microdilution method was used to detect the antibiotic susceptibility profiles of 420 C. striatum clinical isolates, and PFGE method was used to discriminate different clones. Furthermore, in vitro adherence assay and mouse toxicity assay were performed to assess the pathogenicity of the strains with different genotypes.Results 420 C. striatum isolates were all sensitive to vancomycin, linezolid and daptomycin. Based on antibiotic resistance results, 420 strains were classified into 19 resistance patterns, when R1, R2 and R3 patterns accounted for 45.2%(190/420), 20.2%(85/420) and 22.4%(94/420), which were all multi-drug resistant patterns. PFGE typing results showed that 107 C. striatum strains were classified into 52 types (T01-T52), when 4 epidemic clones(T36, T28, T32, T14) accounted for 14.02% (15/107), 11.21%(12/107), 5.61%(6/107) and 3.73%(4/107), respectively. All of these 4 clones belonged to resistance patterns R1, R2 and R3. Among 27 C. striatum strains, 92.6%(25/27) strains showed moderate to strong in vitro adherence abilities, while only 7.4%(2/27) strains showed weak adherence ability on polystyrene surfaces. Furthermore, mouse lethality of different strains differed greatly, when non-dominant clone(Strain NMGYC339, T24) showed the strongest mouse lethality(90.0%).Conclusions The majority of C. striatum strains were multi-drug resistant and few dominant clones could persist for a long time in hospital environment. The in vitro adherence abilities and mouse lethality among different clones differed greatly. The resistance and pathogenicity of C. striatum clinical strains should be paid more attention to, especially for some specific clones at different hospitals.

MraW is a 16S rRNA methyltransferase and plays a role in the fine-tuning of the ribosomal decoding center. It was recently found to contribute to the virulence of Staphylococcus aureus. In this study, we examined the function of MraW in Escherichia coli O157:H7 and found that the deletion of mraW led to decreased motility, flagellar production and DNA methylation. Whole-genome bisulfite sequencing showed a genome wide decrease of methylation of 336 genes and 219 promoters in the mraW mutant including flagellar genes. The methylation level of flagellar genes was confirmed by bisulfite PCR sequencing. Quantitative reverse transcription PCR results indicated that the transcription of these genes was also affected. MraW was furtherly observed to directly bind to the four flagellar gene sequences by electrophoretic mobility shift assay (EMSA). A common flexible motif in differentially methylated regions (DMRs) of promoters and coding regions of the four flagellar genes was identified. Reduced methylation was correlated with altered expression of 21 of the 24 genes tested. DNA methylation activity of MraW was confirmed by DNA methyltransferase activity assay in vitro and repressed by DNA methylation inhibitor 5-aza-2′-deoxycytidine (5-aza). In addition, the mraW mutant colonized poorer than wild type in mice. We also found that the expression of mraZ in the mraW mutant was increased confirming the antagonistic effect of mraW on mraZ. In conclusion, mraW was found to be a DNA methylase and have a wide-ranging effect on E. coli O157:H7 including motility and virulence in vivo via genome wide methylation and mraZ antagonism.

MraW is a 16S rRNA methyltransferase and plays a role in the fine-tuning of the ribosomal decoding center. It was recently found to contribute to the virulence of Staphylococcus aureus. In this study, we examined the function of MraW in Escherichia coli O157:H7 and found that the deletion of mraW led to decreased motility, flagellar production and DNA methylation. Whole-genome bisulfite sequencing showed a genome wide decrease of methylation of 336 genes and 219 promoters in the mraW mutant including flagellar genes. The methylation level of flagellar genes was confirmed by bisulfite PCR sequencing. Quantitative reverse transcription PCR results indicated that the transcription of these genes was also affected. MraW was furtherly observed to directly bind to the four flagellar gene sequences by electrophoretic mobility shift assay (EMSA). A common flexible motif in differentially methylated regions (DMRs) of promoters and coding regions of the four flagellar genes was identified. Reduced methylation was correlated with altered expression of 21 of the 24 genes tested. DNA methylation activity of MraW was confirmed by DNA methyltransferase activity assay in vitro and repressed by DNA methylation inhibitor 5-aza-2′-deoxycytidine (5-aza). In addition, the mraW mutant colonized poorer than wild type in mice. We also found that the expression of mraZ in the mraW mutant was increased confirming the antagonistic effect of mraW on mraZ. In conclusion, mraW was found to be a DNA methylase and have a wide-ranging effect on E. coli O157:H7 including motility and virulence in vivo via genome wide methylation and mraZ antagonism.

The Zika virus (ZIKV) can induce inflammation in immunoprivileged organs (e.g., the brain and testis), leading to the Guillain-Barre syndrome and damaging the testes. During an infection with the ZIKV, immune cells have been shown to infiltrate into the tissues. However, the cellular mechanisms that define the protection and/or immunopathogenesis of these immune cells during a ZIKV infection are still largely unknown. Herein, we describe methods to evaluate the virus-specific T-cell functionality in these immunoprivileged organs of ZIKV-infected mice. These methods include a) a ZIKV infection and vaccine inoculation in Ifnar1-/- mice; b) histopathology, immunofluorescence, and immunohistochemistry assays to detect the virus infection and inflammation in the brain, testes, and spleen; c) the preparation of a tetramer of ZIKV-derived T-cell epitopes; d) the detection of ZIKV-specific T cells in the monocytes isolated from the brain, testes, and spleen. Using these approaches, it is possible to detect the antigen-specific T cells that have infiltrated into the immunoprivileged organs and to evaluate the functions of these T cells during the infection: potential immune protection via virus clearance and/or immunopathogenesis to exacerbate the inflammation. These findings may also help to clarify the contribution of T cells induced by the immunization against ZIKV.

The recent outbreak of Zika virus (ZIKV) has emerged as a global health concern. ZIKV can persist in human semen and be transmitted by sexual contact, as well as by mosquitoes, as seen for classical arboviruses. We along with others have previously demonstrated that ZIKV infection leads to testis damage and infertility in mouse models. So far, no prophylactics or therapeutics are available; therefore, vaccine development is urgently demanded. Recombinant chimpanzee adenovirus has been explored as the preferred vaccine vector for many pathogens due to the low preexisting immunity against the vector among the human population. Here, we developed a ZIKV vaccine based on recombinant chimpanzee adenovirus type 7 (AdC7) expressing ZIKV M/E glycoproteins. A single vaccination of AdC7-M/E was sufficient to elicit potent neutralizing antibodies and protective immunity against ZIKV in both immunocompetent and immunodeficient mice. Moreover, vaccinated mice rapidly developed neutralizing antibody with high titers within 1 week postvaccination, and the elicited antiserum could cross-neutralize heterologous ZIKV strains. Additionally, ZIKV M- and E-specific T cell responses were robustly induced by AdC7-M/E. Moreover, one-dose inoculation of AdC7-M/E conferred mouse sterilizing immunity to eliminate viremia and viral burden in tissues against ZIKV challenge. Further investigations showed that vaccination with AdC7-M/E completely protected against ZIKV-induced testicular damage. These data demonstrate that AdC7-M/E is highly effective and represents a promising vaccine candidate for ZIKV control. IMPORTANCE Zika virus (ZIKV) is a pathogenic flavivirus that causes severe clinical consequences, including congenital malformations in fetuses and Guillain-Barré syndrome in adults. Vaccine development is a high priority for ZIKV control. In this study, to avoid preexisting anti-vector immunity in humans, a rare serotype chimpanzee adenovirus (AdC7) expressing the ZIKV M/E glycoproteins was used for ZIKV vaccine development. Impressively, AdC7-M/E exhibited exceptional performance as a ZIKV vaccine, as follows: (i) protective efficacy by a single vaccination, (ii) rapid development of a robust humoral response, (iii) durable immune responses, (iv) robust T cell responses, and (v) sterilizing immunity achieved by a single vaccination. These advantages of AdC7-M/E strongly support its potential application as a promising ZIKV vaccine in the clinic.

The newly-emerging Middle East respiratory syndrome coronavirus (MERS-CoV) can cause severe and fatal acute respiratory disease in humans. Despite global efforts, the potential for an associated pandemic in the future cannot be excluded. The development of effective counter-measures is urgent. MERS-CoV-specific anti-viral drugs or vaccines are not yet available. Using the spike receptor-binding domain of MERS-CoV (MERS-RBD) to immunize mice, we identified two neutralizing monoclonal antibodies (mAbs) 4C2 and 2E6. Both mAbs potently bind to MERS-RBD and block virus entry in vitro with high efficacy. We further investigated their mechanisms of neutralization by crystallizing the complex between the Fab fragments and the RBD, and solved the structure of the 4C2 Fab/MERS-RBD complex. The structure showed that 4C2 recognizes an epitope that partially overlaps the receptor-binding footprint in MERS-RBD, thereby interfering with the virus/receptor interactions by both steric hindrance and interface-residue competition. 2E6 also blocks receptor binding, and competes with 4C2 for binding to MERS-RBD. Based on the structure, we further humanized 4C2 by preserving only the paratope residues and substituting the remaining amino acids with the counterparts from human immunoglobulins. The humanized 4C2 (4C2h) antibody sustained similar neutralizing activity and biochemical characteristics to the parental mouse antibody. Finally, we showed that 4C2h can significantly abate the virus titers in lungs of Ad5-hCD26-transduced mice infected with MERS-CoV, therefore representing a promising agent for prophylaxis and therapy in clinical settings.

Zanamivir and oseltamivir are principal influenza antiviral drugs that target viral neuraminidase (NA), but resistant viruses containing mutant NAs with diminished drug affinity are increasingly emerging. Using the structural knowledge of both drug-binding sites and their spatial arrangement on the homotetrameric NA, we have developed a tetravalent zanamivir (TZ) molecule that exhibited marked increases in NA binding affinity, inhibition of NA enzyme activity, and in vitro plus in vivo antiviral efficacy over zanamivir. TZ functioned against both human seasonal H3N2 and avian H7N9 viruses, including drug-resistant mutants. Crystal structure of a resistant N9 NA in complex with TZ explained the function, which showed that four zanamivir residues simultaneously bound to all four monomers of NA. The design method of TZ described in this study may be useful to develop drugs or ligands that target proteins with multiple binding sites. The potent anti-influenza activity of TZ makes it attractive for further development.

Zika virus (ZIKV) persists in the semen of male patients, a first for flavivirus infection. Here, we demonstrate that ZIKV can induce inflammation in the testis and epididymidis, but not in the prostate or seminal vesicle, and can lead to damaged testes after 60 days post-infection in mice. ZIKV induces innate immune responses in Leydig, Sertoli, and epididymal epithelial cells, resulting in the production of pro-inflammatory cytokines/chemokines. However, ZIKV does not induce a rapid and abundant cytokine production in peritubular cell and spermatogonia, suggesting that these cells are vulnerable for ZIKV infection and could be the potential repositories for ZIKV. Our study demonstrates a correlation between ZIKV and testis infection/damage and suggests that ZIKV infection, under certain circumstances, can eventually lead to male infertility.