Immunogenicity and protective efficacy of a DNA vaccine inducing optimal expression of the SARS-CoV-2 S gene in hACE2 mice.

The wide spread of coronavirus disease 2019 (COVID-19) has significantly threatened public health. Human herd immunity induced by vaccination is essential to fight the epidemic. Therefore, highly immunogenic and safe vaccines are necessary to control SARS-CoV-2, whose S protein is the antigenic determinant responsible for eliciting antibodies that prevent viral entry and fusion. In this study, we developed a SARS-CoV-2 DNA vaccine expressing the S protein, named pVAX-S-OP, which was optimized according to the human-origin codon preference and using polyinosinic-polycytidylic acid as an adjuvant. pVAX-S-OP induced specific antibodies and neutralizing antibodies in BALB/c and hACE2 transgenic mice. Furthermore, we observed 1.43-fold higher antibody titers in mice receiving pVAX-S-OP plus adjuvant than in those receiving pVAX-S-OP alone. Interferon gamma production in the pVAX-S-OP-immunized group was 1.58 times (CD3+CD4+IFN-gamma+) and 2.29 times (CD3+CD8+IFN-gamma+) lower than that in the pVAX-S-OP plus adjuvant group but higher than that in the control group. The pVAX-S-OP vaccine was also observed to stimulate a Th1-type immune response. When, hACE2 transgenic mice were challenged with SARS-CoV-2, qPCR detection of N and E genes showed that the viral RNA loads in pVAX-S-OP-immunized mice lung tissues were 104 times and 106 times lower than those of the PBS control group, which shows that the vaccine could reduce the amount of live virus in the lungs of hACE2 mice. In addition, pathological sections showed less lung damage in the pVAX-S-OP-immunized group. Taken together, our results demonstrated that pVAX-S-OP has significant immunogenicity, which provides support for developing SARS-CoV-2 DNA candidate vaccines.

GII.P16-GII.2 Recombinant Norovirus VLPs Polarize Macrophages Into the M1 Phenotype for Th1 Immune Responses.

Norovirus (NoV) is a zoonotic virus that causes diarrhea in humans and animals. Outbreaks in nosocomial settings occur annually worldwide, endangering public health and causing serious social and economic burdens. The latter quarter of 2016 witnessed the emergence of the GII.P16-GII.2 recombinant norovirus throughout Asia. This genotype exhibits strong infectivity and replication characteristics, proposing its potential to initiate a pandemic. There is no vaccine against GII.P16-GII.2 recombinant norovirus, so it is necessary to design a preventive vaccine. In this study, GII.P16-GII.2 type norovirus virus-like particles (VLPs) were constructed using the baculovirus expression system and used to conduct immunizations in mice. After immunization of mice, mice were induced to produce memory T cells and specific antibodies, indicating that the VLPs induced specific cellular and humoral immune responses. Further experiments were then initiated to understand the underlying mechanisms involved in antigen presentation. Towards this, we established co-cultures between dendritic cells (DCs) or macrophages (Mø) and naïve CD4+T cells and simulated the antigen presentation process by incubation with VLPs. Thereafter, we detected changes in cell surface molecules, cytokines and related proteins. The results indicated that VLPs effectively promoted the phenotypic maturation of Mø but not DCs, as indicated by significant changes in the expression of MHC-II, costimulatory factors and related cytokines in Mø. Moreover, we found VLPs caused Mø to polarize to the M1 type and release inflammatory cytokines, thereby inducing naïve CD4+ T cells to perform Th1 immune responses. Therefore, this study reveals the mechanism of antigen presentation involving GII.P16-GII.2 recombinant norovirus VLPs, providing a theoretical basis for both understanding responses to norovirus infection as well as opportunities for vaccine development.

Genetic characterization of a new NSP2-deletion porcine reproductive and Respiratory Syndrome Virus in China.

The Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) cause a huge economic loss around the pig industry worldwide; the NADC30-like PRRSV have attracted much attention outbreaks in China in recent years. Recombination between PRRSV subtypes, point mutations, insertions and deletions that contribute to the emergence of new variants in the genome. In this study, the PRRSV-HB-16-China-2019 strain's full-length genomic sequence shares 93.0% nucleotide similarity to NADC30 PRRSV without any gene insertion. Compared with VR-2332, it has an NSP2 coding region that is different from NADC30, which has a discontinuous 206-aa (111-aa from position 323 to 433 and 95-aa from position 476 to 570) deletion. Compared with other NADC30-Like strains, it has a discontinuous 75-amino acid (75-aa from position 476 to 552) deletion, which was first reported. Notably, the strain, PRRSV-HB-16-China-2019, contained an addition a 1-aa deletion in ORF5 and a unique 3-nt deletion in 3'-UTR similar to NADC30, the strain is recombined between a NADC30-like strain and a vaccine strain named RespPRRS MLV(parental strain VR-2332). Our findings indicate that PRRSV-HB-16-China-2019 is a new NSP2-deletion NADC30-like strain with certain deletions and mutations. Our results show that the emergence of the new NADC30-like strain has increased the difficulty of PRRSV prevention in China.

Newcastle Disease Virus Inhibits the Proliferation of T Cells Induced by Dendritic Cells In Vitro and In Vivo.

Newcastle disease virus (NDV) infects poultry and antagonizes host immunity via several mechanisms. Dendritic cells (DCs) are characterized as specialized antigen presenting cells, bridging innate and adaptive immunity and regulating host resistance to viral invasion. However, there is little specific knowledge of the role of DCs in NDV infection. In this study, the representative NDV lentogenic strain LaSota was used to explore whether murine bone marrow derived DCs mature following infection. We examined surface molecule expression and cytokine release from DCs as well as proliferation and activation of T cells in vivo and in vitro in the context of NDV. The results demonstrated that infection with lentogenic strain LaSota induced a phenotypic maturation of immature DCs (imDCs), which actually led to curtailed T cell responses. Upon infection, the phenotypic maturation of DCs was reflected by markedly enhanced MHC and costimulatory molecule expression and secretion of proinflammatory cytokines. Nevertheless, NDV-infected DCs produced the anti-inflammatory cytokine IL-10 and attenuated T cell proliferation, inducing Th2-biased responses. Therefore, our study reveals a novel understanding that DCs are phenotypically mature but dysfunctional in priming T cell responses during NDV infection.

Neutron irradiation and post annealing effect on sapphire by positron annihilation.

Sapphire single crystals grown by an improved Kyropoulos-like method are irradiated by fast neutron flux. The irradiated doses of neutron are 10(18) and 10(19)n/cm(2). The infrared transmission spectra of sapphire were studied before and after irradiation. The irradiated samples were annealed at 200, 400, 600, 800 and 1000 degrees C for 10min in ambient atmosphere. Positron annihilation studies have been carried out before and after neutron irradiation. The experimentally measured positron lifetime in the pristine specimen is 143ps. There were aluminum vacancies produced in sapphire crystals after neutron irradiation. The positron lifetime increased with the dose of neutron flux. A longer value tau(2) was found after annealing at 600 degrees C, which indicated vacancies were aggregated with each other. The second long-time component tau(2) has been found to increase with the annealing temperature. There was almost no change in peak position of the CDB spectra after neutron irradiation and isothermal annealing. The chemical environment of core in sapphire did not change greatly after neutron irradiation.