Evaluation of Immunogenicity and Clinical Protection of SARS-CoV-2 S1 and N Antigens in Syrian Golden Hamster.

The novel coronavirus (SARS-CoV-2) epidemic continues to be a global public crisis affecting human health. Many research groups are developing different types of vaccines to suppress the spread of SARS-CoV-2, and some vaccines have entered phase III clinical trials and have been rapidly implemented. Whether multiple antigen matches are necessary to induce a better immune response remains unclear. To address this question, this study tested the immunogenicity and protective effects of a SARS-CoV-2 recombinant S and N peptide vaccine in the Syrian golden hamster model. This experiment was based on two immunization methods: intradermal and intramuscular administration. Immunized hamsters were challenged with live SARS-CoV-2 14 days after booster immunization. Clinical symptoms were observed daily, and the antibody titer and viral load in each tissue were detected. The results showed that immunization of golden hamsters with the SARS-CoV-2 structural protein S alone or in combination with the N protein through different routes induced antibody responses, whereas immunization with the N protein alone did not. However, although the immunized hamsters exhibited partial alleviation of clinical symptoms when challenged with the virus, neither vaccine effectively inhibited the proliferation and replication of the challenging virus. In addition, the pathological damage in the immunized hamsters was similar to that in the control hamsters. Interestingly, the neutralizing antibody levels of all groups including immunized and nonimmunized animals increased significantly after viral challenge. In conclusion, the immune response induced by the experimental S and N polypeptide vaccines had no significant ability to prevent viral infection and pathogenicity in golden hamsters.

Characterization of the Immunologic Phenotype of Dendritic Cells Infected With Herpes Simplex Virus 1.

Due to viral envelope glycoprotein D binding to cellular membrane HVEM receptor, HSV-1 can infect certain dendritic cells, which becomes an event in the viral strategy to interfere with the host's immune system. We previously generated the HSV-1 mutant strain M6, which produced an attenuated phenotype in mice and rhesus monkeys. The attenuated M6 strain was used to investigate how HSV-1 infection of dendritic cells interferes with both innate and adaptive immunity. Our study showed that dendritic cells membrane HVEM receptors could mediate infection of the wild-type strain and attenuated M6 strain and that dendritic cells infected by both viruses in local tissues of animals exhibited changes in transcriptional profiles associated with innate immune and inflammatory responses. The infection of pDCs and cDCs by the two strains promoted cell differentiation to the CD103+ phenotype, but varied transcriptional profiles were observed, implying a strategy that the HSV-1 wild-type strain interferes with antiviral immunity, probably due to viral modification of the immunological phenotype of dendritic cells during processing and presentation of antigen to T cells, leading to a series of deviations in immune responses, ultimately generating the deficient immune phenotype observed in infected individuals in the clinical.

Distinct infection process of SARS-CoV-2 in human bronchial epithelial cell lines.

Coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), leads to a series of clinical symptoms of respiratory and pulmonary inflammatory reactions via unknown pathologic mechanisms related to the viral infection process in tracheal or bronchial epithelial cells. Investigation of this viral infection in the human bronchial epithelial cell line (16HBE) suggests that SARS-CoV-2 can enter these cells through interaction between its membrane-localized S protein with the angiotensin-converting enzyme 2 molecule on the host cell membrane. Further observation indicates distinct viral replication with a dynamic and moderate increase, whereby viral replication does not lead to a specific cytopathic effect but maintains a continuous release of progeny virions from infected cells. Although messenger RNA expression of various innate immune signaling molecules is altered in the cells, transcription of interferons-α (IFN-α), IFN-ß, and IFN-γ is unchanged. Furthermore, expression of some interleukins (IL) related to inflammatory reactions, such as IL-6, IL-2, and IL-8, is maintained at low levels, whereas that of ILs involved in immune regulation is upregulated. Interestingly, IL-22, an IL that functions mainly in tissue repair, shows very high expression. Collectively, these data suggest a distinct infection process for this virus in respiratory epithelial cells, which may be linked to its clinicopathological mechanism.

Mechanism for the lethal effect of enterovirus A71 intracerebral injection in neonatal mice.

Enterovirus A71 (EV-A71) infection is primarily responsible for fatal hand, foot, and mouth disease (HFMD) cases. Infants and younger children are more likely to suffer central nervous system damage as a result of EV-A71 infection, but this virus mostly does not affect older children and adults. This study investigated the possible mechanism underlying the age-dependent lethal effect of EV-A71 infection by comparing neonatal and adult mouse models of EV-A71 infection. Although viral proliferation is absent in both neonatal and adult mice, we observed that EV-A71, as a stimulus for astrocytes, elevates the levels of cytokines and monoamine neurotransmitters in neonatal mice. Then, we selected IL-6 and adrenaline as targets in a pharmacological approach to further validate the roles of these factors in mediating the mortality of neonatal mice after EV-A71 infection. Intracerebral injection of IL-6 and adrenaline enhanced the severity of EV-A71 infection, while treatment with an anti-IL-6-neutralizing antibody or the adrenergic-antagonist phenoxybenzamine reversed the lethal effect of EV-A71 in neonatal mice. These results suggest that the central nervous system (CNS) damage in neonatal cases of EV-A71 infection might be caused by an activated fetal cerebral immune response to the virus, including the disruption of brainstem function through increased levels of cytokines and neurotransmitters, rather than the typical cytopathic effect (CPE) of viral infection.

Reducing Viral Inhibition of Host Cellular Apoptosis Strengthens the Immunogenicity and Protective Efficacy of an Attenuated HSV-1 Strain.

Herpes simplex virus 1 (HSV-1), a member of α herpesviruses, shows a high infectivity rate of 30%-60% in populations of various ages. Some herpes simplex (HSV) vaccine candidates evaluated during the past 20 years have not shown protective efficacy against viral infection. An improved understanding of the immune profile of infected individuals and the associated mechanism is needed. HSV uses an immune evasion strategy during viral replication, and various virus-encoded proteins, such as ICP47 and Vhs, participate in this process through limiting the ability of CD8+ cytotoxic T lymphocytes to recognize target cells. Other proteins, e.g., Us3 and Us5, also play a role in viral immune evasion via interfering with cellular apoptosis. In this work, to study the mechanism by which HSV-1 strain attenuation interferes with the viral immune evasion strategy, we constructed a mutant strain, M5, with deletions in the Us3 and Us5 genes. M5 was shown to induce higher neutralizing antibody titers and a stronger cellular immune response than our previously reported M3 strain, and to prevent virus infection more effectively than the M3 strain in an in vivo mouse challenge test.