The zoonotic and natural foci characteristics of SARS-CoV-2.

The origin of SARS-CoV-2 is still an unresolved mystery. In this study, we systematically reviewed the main research progress of wild animals carrying virus highly homologous to SARS-CoV-2 and analyzed the natural foci characteristics of SARS-CoV-2. The complexity of SARS-CoV-2 origin in wild animals and the possibility of SARS-CoV-2 long-term existence in human populations are also discussed. The joint investigation of corona virus carried by wildlife, as well as the ecology and patho-ecology of bats and other wildlife, are key measures to further clarify the characteristics of natural foci of SARS-CoV-2 and actively defend against future outbreaks of emerging zoonotic diseases.

Association of Oral or Intravenous Vitamin C Supplementation with Mortality: A Systematic Review and Meta-Analysis.

Mortality is the most clinically serious outcome, and its prevention remains a constant struggle. This study was to assess whether intravenous or oral vitamin C (Vit-C) therapy is related to reduced mortality in adults. Data from Medline, Embase, and the Cochrane Central Register databases were acquired from their inception to 26 October 2022. All randomized controlled trials (RCTs) involving intravenous or oral Vit-C against a placebo or no therapy for mortality were selected. The primary outcome was all-cause mortality. Secondary outcomes were sepsis, COVID-19, cardiac surgery, noncardiac surgery, cancer, and other mortalities. Forty-four trials with 26540 participants were selected. Although a substantial statistical difference was observed in all-cause mortality between the control and the Vit-C-supplemented groups (p = 0.009, RR 0.87, 95% CI 0.78 to 0.97, I2 = 36%), the result was not validated by sequential trial analysis. In the subgroup analysis, mortality was markedly reduced in Vit-C trials with the sepsis patients (p = 0.005, RR 0.74, 95% CI 0.59 to 0.91, I2 = 47%), and this result was confirmed by trial sequential analysis. In addition, a substantial statistical difference was revealed in COVID-19 patient mortality between the Vit-C monotherapy and the control groups (p = 0.03, RR 0.84, 95% CI 0.72 to 0.98, I2 = 0%). However, the trial sequential analysis suggested the need for more trials to confirm its efficacy. Overall, Vit-C monotherapy does decrease the risk of death by sepsis by 26%. To confirm Vit-C is associated with reduced COVID-19 mortality, additional clinical random control trials are required.

Molnupiravir for treatment of adults with mild or moderate COVID-19: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: The effects of molnupiravir in treating patients with non-severe COVID-19 remain uncertain. OBJECTIVES: To evaluate the efficacy and safety of molnupiravir in adult patients with mild or moderate COVID-19. DATA SOURCES: PubMed, Embase, CENTRAL, Web of Science, and WHO COVID-19 database up to 27 December 2022. STUDY ELIGIBILITY CRITERIA: Randomized controlled trials with no language restrictions. PARTICIPANTS: Adults with mild or moderate COVID-19. INTERVENTIONS: Molnupiravir against standard care or placebo. ASSESSMENT OF RISK OF BIAS: We used a revision of RoB-2 criteria. METHODS OF DATA SYNTHESIS: Outcomes were mortality, hospital admission, viral clearance, time to viral clearance, time to symptom resolution or clinical improvement, any adverse events, and serious adverse events. We performed DerSimonian-Laird random-effects meta-analyses to summarize the evidence and evaluated the certainty of evidence using the Grading of Recommendations Assessment, Development, and Evaluation approach. RESULTS: Nine randomized controlled trials enrolling 30 472 patients proved eligible. Majority of patients were outpatients, with a mean age ranging from 35 to 56.6 years. In adult patients with mild or moderate COVID-19, molnupiravir probably reduces mortality (relative risk [RR], 0.43; 95% CI, 0.20-0.94; risk difference [RD], 0.1% fewer; moderate certainty) and the risk of hospital admission (RR, 0.67; 95% CI, 0.45-0.99; RD, 1.4% fewer; moderate certainty) and may reduce time to viral clearance (mean difference, -1.81 days; 95% CI, -3.31 to -0.31; low certainty) and time to symptom resolution or clinical improvement (mean difference, -2.39 days; 95% CI, -3.71 to -1.07; low certainty). Molnupiravir probably increases the rate of viral clearance (RR, 3.47; 95% CI, 2.43-4.96; RD 16.1% more; moderate certainty) at 7 days (±3 days) and likely does not increase serious adverse events (RR, 0.84; 95% CI, 0.61-1.15; RD 0.1% fewer; moderate certainty). CONCLUSIONS: In adult patients with mild or moderate COVID-19, molnupiravir likely reduces mortality and risk of hospital admission probably without increasing serious adverse events.

Non-spike and spike-specific memory T cell responses after the third dose of inactivated COVID-19 vaccine.

Background: During the COVID-19 epidemic, vaccination has become the most safe and effective way to prevent severe illness and death. Inactivated vaccines are the most widely used type of COVID-19 vaccines in the world. In contrast to spike-based mRNA/protein COVID-19 vaccines, inactivated vaccines generate antibodies and T cell responses against both spike and non-spike antigens. However, the knowledge of inactivated vaccines in inducing non-spike-specific T cell response is very limited. Methods: In this study, eighteen healthcare volunteers received a homogenous booster (third) dose of the CoronaVac vaccine at least 6 months after the second dose. CD4+ and CD8+ T cell responses against a peptide pool from wild-type (WT) non-spike proteins and spike peptide pools from WT, Delta, and Omicron SARS-CoV-2 were examined before and 1-2 weeks after the booster dose. Results: The booster dose elevated cytokine response in CD4+ and CD8+ T cells as well as expression of cytotoxic marker CD107a in CD8+ T cells in response to non-spike and spike antigens. The frequencies of cytokine-secreting non-spike-specific CD4+ and CD8+ T cells correlated well with those of spike-specific from WT, Delta, and Omicron. Activation-induced markers (AIM) assay also revealed that booster vaccination elicited non-spike-specific CD4+ and CD8+ T cell responses. In addition, booster vaccination produced similar spike-specific AIM+CD4+ and AIM+CD8+ T cell responses to WT, Delta, and Omicron, indicting strong cross-reactivity of functional cellular response between WT and variants. Furthermore, booster vaccination induced effector memory phenotypes of spike-specific and non-spike-specific CD4+ and CD8+ T cells. Conclusions: These data suggest that the booster dose of inactive vaccines broadens both non-spike-specific and spike-specific T cell responses against SARS-CoV-2.

Global border restrictions in 2020-2021: Adherence and the effectiveness in long-term COVID-19 epidemic control.

BACKGROUND: Restrictions on international travel were widely applied to contain cross-border COVID-19 diffusion, while such applications varied globally, and little was known about their impacts on the long-term epidemic progression. METHODS: We explored the global diversity in maintaining border policies classified to four levels (screening, quarantine, ban on regions and total border closure) using data of 185 countries and regions between 01 January 2020 to 31 December 2021. By using Ordinary least squares (OLS) regression and quantile regression (QR) models, we examined the relationship between total COVID-19 incidence and the cumulative duration of each policy level in 2020-2021, and the heterogeneity of such association across different transmission severity countries. RESULTS: Firstly, "ban on regions" was the most durable policy applied in high-income countries, while in low-income countries, less stringent measures of screening and quarantine arrivals were applied the longest. Secondly, the cumulatively longer maintenance of the border quarantine was significantly associated with lower infections (log) in COVID-19 high-prevalent countries (75th QR, coefficient estimates [ß] = -0.0038, 95% confidence interval: -0.0066 to -0.0010). By contrast, in medium and high transmission severity countries, those with longer duration of imposing bans on regions showed no suppressing effects but significantly higher COVID-19 incidence (OLS regression, ß = 0.0028, 95% CI: 0.0009-0.0047; 75th QR, ß = 0.0039, 95% CI: 0.0014-0.0063). No other significant results were found. CONCLUSION: From the long-term perspective, inbound quarantine was effective in mitigating severe epidemics. However, in countries with medium or high COVID-19 prevalence, our findings of ban on regions highlighted its ineffectiveness in the long-term epidemic progression.

Study on the COVID-19 epidemic in mainland China between November 2022 and January 2023, with prediction of its tendency.

The prediction system EpiSIX was used to study the COVID-19 epidemic in mainland China between November 2022 and January 2023, based on reported data from December 9, 2022, to January 30, 2023, released by The Chinese Center for Disease Control and Prevention on February 1, 2023. Three kinds of reported data were used for model fitting: the daily numbers of positive nucleic acid tests and deaths, and the daily number of hospital beds taken by COVID-19 patients. It was estimated that the overall infection rate was 87.54% and the overall case fatality rate was 0.078%-0.116% (median 0.100%). Assuming that a new COVID-19 epidemic outbreak would start in March or April of 2023, induced by a slightly more infectious mutant strain, we predicted a possible large rebound between September and October 2023, with a peak demand of between 800,000 and 900,000 inpatient beds. If no such new outbreak was induced by other variants, then the current COVID-19 epidemic course in mainland China would remain under control until the end of 2023. However, it is suggested that the necessary medical resources be prepared to manage possible COVID-19 epidemic emergencies in the near future, especially for the period between September and October 2023.

"Mutation blacklist" and "mutation whitelist" of SARS-CoV-2.

Over the past two years, scientists throughout the world have completed more than 6 million SARS-CoV-2 genome sequences. Today, the number of SARS-CoV-2 genomes exceeds the total number of all other viral genomes. These genomes are a record of the evolution of SARS-CoV-2 in the human host, and provide information on the emergence of mutations. In this study, analysis of these sequenced genomes identified 296,728 de novo mutations (DNMs), and found that six types of base substitutions reached saturation in the sequenced genome population. Based on this analysis, a "mutation blacklist" of SARS-CoV-2 was compiled. The loci on the "mutation blacklist" are highly conserved, and these mutations likely have detrimental effects on virus survival, replication, and transmission. This information is valuable for SARS-CoV-2 research on gene function, vaccine design, and drug development. Through association analysis of DNMs and viral transmission rates, we identified 185 DNMs that positively correlated with the SARS-CoV-2 transmission rate, and these DNMs where classified as the "mutation whitelist" of SARS-CoV-2. The mutations on the "mutation whitelist" are beneficial for SARS-CoV-2 transmission and could therefore be used to evaluate the transmissibility of new variants. The occurrence of mutations and the evolution of viruses are dynamic processes. To more effectively monitor the mutations and variants of SARS-CoV-2, we built a SARS-CoV-2 mutation and variant monitoring and pre-warning system (MVMPS), which can monitor the occurrence and development of mutations and variants of SARS-CoV-2, as well as provide pre-warning for the prevention and control of SARS-CoV-2 (https://www.omicx.cn/). Additionally, this system could be used in real-time to update the "mutation whitelist" and "mutation blacklist" of SARS-CoV-2.

Micronutrient perspective on COVID-19: Umbrella review and reanalysis of meta-analyses.

INTRODUCTION: Micronutrients are clinically important in managing COVID-19, and numerous studies have been conducted, but inconsistent findings exist. OBJECTIVE: To explore the association between micronutrients and COVID-19. METHODS: PubMed, Web of Science, Embase, Cochrane Library and Scopus for study search on July 30, 2022 and October 15, 2022. Literature selection, data extraction and quality assessment were performed in a double-blinded, group discussion format. Meta-analysis with overlapping associations were reconsolidated using random effects models, and narrative evidence was performed in tabular presentations. RESULTS: 57 reviews and 57 latest original studies were included. 21 reviews and 53 original studies were of moderate to high quality. Vitamin D, vitamin B, zinc, selenium, and ferritin levels differed between patients and healthy people. Vitamin D and zinc deficiencies increased COVID-19 infection by 0.97-fold/0.39-fold and 1.53-fold. Vitamin D deficiency increased severity 0.86-fold, while low vitamin B and selenium levels reduced severity. Vitamin D and calcium deficiencies increased ICU admission by 1.09 and 4.09-fold. Vitamin D deficiency increased mechanical ventilation by 0.4-fold. Vitamin D, zinc, and calcium deficiencies increased COVID-19 mortality by 0.53-fold, 0.46-fold, and 5.99-fold, respectively. CONCLUSION: The associations between vitamin D, zinc, and calcium deficiencies and adverse evolution of COVID-19 were positive, while the association between vitamin C and COVID-19 was insignificant.REGISTRATION: PROSPERO CRD42022353953.

The Threat of Potentially Pathogenic Bacteria in the Feces of Bats.

Bats have attracted global attention because of their zoonotic association with severe acute respiratory syndrome coronavirus (SARS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Previous and ongoing studies have predominantly focused on bat-borne viruses; however, the prevalence or abundance of bat-borne pathogenic bacteria and their potential public health significance have largely been neglected. For the first time, this study used both metataxonomics (16S rRNA marker gene sequencing) and culturomics (traditional culture methods) to systematically evaluate the potential public health significance of bat fecal pathogenic bacteria. To this end, fecal samples were obtained from five bat species across different locations in China, and their microbiota composition was analyzed. The results revealed that the bat microbiome was most commonly dominated by Proteobacteria, while the strictly anaerobic phylum Bacteroidetes occupied 35.3% of the relative abundance in Rousettus spp. and 36.3% in Hipposideros spp., but less than 2.7% in the other three bat species (Taphozous spp., Rhinolophus spp., and Myotis spp.). We detected 480 species-level phylotypes (SLPs) with PacBio sequencing, including 89 known species, 330 potentially new species, and 61 potentially higher taxa. In addition, a total of 325 species were identified by culturomics, and these were classified into 242 named species and 83 potentially novel species. Of note, 32 of the 89 (36.0%) known species revealed by PacBio sequencing were found to be pathogenic bacteria, and 69 of the 242 (28.5%) known species isolated by culturomics were harmful to people, animals, or plants. Additionally, nearly 40 potential novel species which may be potential bacterial pathogens were identified. IMPORTANCE Bats are one of the most diverse and widely distributed groups of mammals living in close proximity to humans. In recent years, bat-borne viruses and the viral zoonotic diseases associated with bats have been studied in great detail. However, the prevalence and abundance of pathogenic bacteria in bats have been largely ignored. This study used high-throughput sequencing techniques (metataxonomics) in combination with traditional culture methods (culturomics) to analyze the bacterial flora in bat feces from different species of bats in China, revealing that bats are natural hosts of pathogenic bacteria and carry many unknown bacteria. The results of this study can be used as guidance for future investigations of bacterial pathogens in bats.

Evolutionary analysis of Omicron variant BF.7 and BA.5.2 pandemic in China.

On December 7, 2022, China adjusted public health control measures, there have been widespread of SARS-CoV-2 infections in Chinese mainland. As the number of infected people increased, the mutation probability of SARS-CoV-2 is also raised. Therefore, it is of great importance to monitor SARS-CoV-2 variants and its mutations in China. In this current study, 665 SARS-CoV-2 genomes from China deposited in the public database were used to analyze the proportion of different variants; to determine the composition of variants in China across different provinces; and analyze specific mutation frequency, focusing on 12 immune escape residues. The results showed that no new mutations were generated on the 12 immune escape residues. The evolutionary analysis of the BF.7 variant circulating in China showed that there is an independent evolutionary branch with unique mutation sites, officially named BF.7.14 by PANGO. This variant may have been imported from Russia to Inner Mongolia at the end of September 2022 and continued its spread in China. The evolutionary analysis of BA.5.2 variant shows that the variant is composed of two sub-variants, named BA.5.2.48 and BA.5.2.49 by PANGO, respectively. This variant may have been imported from abroad to Beijing at the beginning of September 2022 and formed two sub-variants after domestic transmission. Finally, this study showed that current epidemic variants in China were already circulating in other countries, and there were no additional mutations on immune escape residues that could pose a threat to other countries.

Demoralization: Where it stands-and where we can take it: A bibliometric analysis

Objectives The purpose is to analyze existing studies related to the field of demoralization through bibliometrics. Methodology Relevant literature on demoralization was searched from PubMed, Web of Science, the Cochrane Library, and CINAHL Complete. Bibliometric analysis was performed using GraphPad Prisma 8.2.1, VOSviewer 1.6.18 and R software. Research publication trends, author-country collaboration, research hotspots and future trends were explored by generating network relationship maps. Results A total of 1,035 publications related to the field of demoralization were identified. The earliest relevant studies have been published since 1974, and the studies have grown faster since 2000. Psyche-oncology and Psychother Psychosom had the highest number of publications (n = 25). The United States, Italy and Australia have made outstanding contributions to the field and there was an active collaboration among leading scholars. Major research hotspots include the multiple ways of assessing demoralization, the specificity of various demographics and psychological disorders in different disease contexts, and the association and distinction of diverse clinical psychological abnormalities. The impact of COVID-19 on demoralization and subsequent interventions and psychological care may become a future research direction. Conclusion There has been a significant increase in research in the field of demoralization after 2000. The United States provided the most publications. There is overall active collaboration between authors, countries, and institutions. In future research, more attention will be paid to the effects of COVID-19 on demoralization and intervention care for this psychology.

Past, present and future of living systematic review: a bibliometrics analysis.

INTRODUCTION: In recent years, the concept of living systematic review (LSR) has attracted the attention of many scholars and institutions. A growing number of studies have been conducted based on LSR methodology, but their focus direction is unclear. The objective of this study was to provide a comprehensive review of existing LSR-related studies and to analyse their whole picture and future trends with bibliometrics. METHODS: A comprehensive search strategy was used to construct a representative dataset of LSRs up to October 2021. GraphPad V.8.2.1 and Mindmaster Pro presented the basic information of the included studies and the timeline of LSR development, respectively. The author and country cooperation network, hotspot distribution clustering, historical citation network and future development trend prediction related to LSR were visualised by VOSviewer V.1.6.16 and R-Studio V.1.4. RESULTS: A total of 213 studies were eventually included. The concept of LSR was first proposed in 2014, and the number of studies has proliferated since 2020. There was a closer collaboration between author teams and more frequent LSR research development and collaboration in Europe, North America and Australia. Numerous LSR studies have been published in high-impact journals. COVID-19 is the predominant disease of concern at this stage, and the rehabilitation of its patients and virological studies are possible directions of research in LSR for a long time to come. A review of existing studies found that more than half of the LSR series had not yet been updated and that the method needed to be more standardised in practice. CONCLUSION: Although LSR has a relatively short history, it has received much attention and currently has a high overall acceptance. The LSR methodology was further practised in COVID-19, and we look forward to seeing it applied in more areas.

Massive‐scale genomic analysis reveals SARS‐CoV‐2 mutation characteristics and evolutionary trends

The severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) pandemic resulted in significant societal costs. Hence, an in‐depth understanding of SARS‐CoV‐2 virus mutation and its evolution will help determine the direction of the COVID‐19 pandemic. In this study, we identified 296,728 de novo mutations in more than 2,800,000 high‐quality SARS‐CoV‐2 genomes. All possible factors affecting the mutation frequency of SARS‐CoV‐2 in human hosts were analyzed, including zinc finger antiviral proteins, sequence context, amino acid change, and translation efficiency. As a result, we proposed that when adenine (A) and tyrosine (T) bases are in the context of AM (M stands for adenine or cytosine) or TA motif, A or T base has lower mutation frequency. Furthermore, we hypothesized that translation efficiency can affect the mutation frequency of the third position of the codon by the selection, which explains why SARS‐CoV‐2 prefers AT3 codons usage. In addition, we found a host‐specific asymmetric dinucleotide mutation frequency in the SARS‐CoV‐2 genome, which provides a new basis for determining the origin of the SARS‐CoV‐2. Finally, we summarize all possible factors affecting mutation frequency and provide insights into the mutation characteristics and evolutionary trends of SARS‐CoV‐2. Impact statement In this study, we analyzed the possible factors affecting mutations in more than 2,800,000 high‐quality severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) genomes. To our knowledge we are the first to propose that when the A or T base conforms to AM or TA motif, the A or T base has a lower mutation frequency;and subsequently, translation efficiency can affect the mutation frequency from C/G to A/T on the third position of the codon by the selection. We found significant host‐specific asymmetric mutations at dinucleotide sites. In addition, we also identified the characteristics of SARS‐CoV‐2 mutations and hypothesized the evolutionary trends of the virus in the human host. These findings are valuable for predicting the development of the COVID‐19 pandemic and bring to light new hypotheses regarding the origin of SARS‐CoV‐2.

Antiviral effect and anti-COVID-19 potential of immunobiotics

Immunobiotics, a group of probiotics, have the effect of anti-infection by regulating immune function, which can be added in in foods or used to make adjuvants or medicines (biologics). Immunobiotics can stimulate the mucosal immune system of the body, regulate innate and acquired immunity and exert non-specific anti-microbial (bacterial and viral) infection effects through oral, nasal mucosa, sublingual and other routes, but the immune regulation function of immunobiotics is species-specific. Oral administration of Lactobacillus plantarum GUANKE stimulated the increase and maintenance of SARS-CoV-2 neutralization antibodies in mice even 6 months after immunization. When L. plantarum GUANKE was given immediately after SARS-CoV-2 vaccination, the level of SARS-COV-2 specific neutralizing antibody in bronchoalveolar lavage increased by 8 times in mice, which improved the local and systematic cellular immune response to SARS-CoV-2 of mice. Clinical studies have found that immunobiotics have the auxiliary effect in the treatment of COVID-19 by mitigating the symptoms and increase the level of SARS-CoV-2 specific antibody of the patients. It is necessary to conduct research and evaluation for the appropriate guideline of immunobiotics use as erly as possible to provide a new option for the prevention and control of COVID-19.

Super Dominant Pathobiontic Bacteria in the Nasopharyngeal Microbiota Cause Secondary Bacterial Infection in COVID-19 Patients.

Coronavirus disease 2019 (COVID-19) is a respiratory infectious disease responsible for many infections worldwide. Differences in respiratory microbiota may correlate with disease severity. Samples were collected from 20 severe and 51 mild COVID-19 patients. High-throughput sequencing of the 16S rRNA gene was used to analyze the bacterial community composition of the upper and lower respiratory tracts. The indices of diversity were analyzed. When one genus accounted for >50% of reads from a sample, it was defined as a super dominant pathobiontic bacterial genus (SDPG). In the upper respiratory tract, uniformity indices were significantly higher in the mild group than in the severe group (P < 0.001). In the lower respiratory tract, uniformity indices, richness indices, and the abundance-based coverage estimator were significantly higher in the mild group than in the severe group (P < 0.001). In patients with severe COVID-19, SDPGs were detected in 40.7% of upper and 63.2% of lower respiratory tract samples. In patients with mild COVID-19, only 10.8% of upper and 8.5% of lower respiratory tract samples yielded SDPGs. SDPGs were present in both upper and lower tracts in seven patients (35.0%), among which six (30.0%) patients possessed the same SDPG in the upper and lower tracts. However, no patients with mild infections had an SDPG in both tracts. Staphylococcus, Corynebacterium, and Acinetobacter were the main SDPGs. The number of SDPGs identified differed significantly between patients with mild and severe COVID-19 (P < 0.001). SDPGs in nasopharyngeal microbiota cause secondary bacterial infection in COVID-19 patients and aggravate pneumonia. IMPORTANCE The nasopharyngeal microbiota is composed of a variety of not only the true commensal bacterial species but also the two-face pathobionts, which are one a harmless commensal bacterial species and the other a highly invasive and deadly pathogen. In a previous study, we found that the diversity of nasopharyngeal microbiota was lost in severe influenza patients. We named the genus that accounted for over 50% of microbiota abundance as super dominant pathobiontic genus, which could invade to cause severe pneumonia, leading to high fatality. Similar phenomena were found here for SARS-CoV-2 infection. The diversity of nasopharyngeal microbiota was lost in severe COVID-19 infection patients. SDPGs in nasopharyngeal microbiota were frequently detected in severe COVID-19 patients. Therefore, the SDPGs in nasopharynx microbiota might invade into low respiratory and be responsible for secondary bacterial pneumonia in patients with SARS-CoV-2 infection.

Boosting Vaccine-Elicited Respiratory Mucosal and Systemic COVID-19 Immunity in Mice With the Oral Lactobacillus plantarum.

Boosting and prolonging SARS-CoV-2 vaccine-elicited immunity is paramount for containing the COVID-19 pandemic, which wanes substantially within months after vaccination. Here we demonstrate that the unique strain of probiotic Lactobacillus plantarum GUANKE (LPG) could promote SARS-CoV-2-specific immune responses in both effective and memory phases through enhancing interferon signaling and suppressing apoptotic and inflammatory pathways. Interestingly, oral LPG administration promoted SARS-CoV-2 neutralization antibodies even 6 months after immunization. Furthermore, when LPG was given immediately after SARS-CoV-2 vaccine inoculation, specific neutralization antibodies could be boosted >8-fold in bronchoalveolar lavage (BAL) and >2-fold in sera, T-cell responses were persistent and stable for a prolonged period both in BAL and the spleen. Transcriptional analyses showed that oral application of LPG mobilized immune responses in the mucosal and systemic compartments; in particular, gut-spleen and gut-lung immune axes were observed. These results suggest that LPG could be applied in combination with SARS-CoV-2 vaccines to boost and prolong both the effective and memory immune responses in mucosal and systemic compartments, thereby improving the efficacy of SARS-CoV-2 vaccination.

SARS-CoV-2 N Protein Induces Acute Lung Injury in Mice via NF-ĸB Activation.

Background: Infection of SARS-CoV-2 may cause acute respiratory syndrome. It has been reported that SARS-CoV-2 nucleocapsid protein (N-protein) presents early in body fluids during infection. The direct involvement of N-protein in lung injury is poorly understood. Methods: Recombinant N-protein was pretreated with polymyxin B, a lipopolysaccharide (LPS)-neutralizing agent. C57BL/6, C3H/HeJ (resistant to LPS), and C3H/HeN (control for C3H/HeJ) mice were exposed to N-protein via intratracheal administration to examine acute lung injury. In vitro, bone marrow-derived macrophages (BMDMs) were cultured with N-protein to study phosphorylation of nuclear factor kappa B (NF-ĸB) p65, macrophage polarization, and expression of proinflammatory cytokines. Results: N-protein produced acute lung injury in C57BL/6 mice, with elevated protein permeability, total cell count, neutrophil infiltration, and proinflammatory cytokines in the bronchioalveolar lavage. N-protein also induced lung injury in both C3H/HeJ and C3H/HeN mice, indicating that the effect could not be attributed to the LPS contamination. N-protein triggered phosphorylation of NF-ĸB p65 in vitro, which was abolished by both N-protein denaturation and treatment with an antibody for N-protein, demonstrating that the effect is N-protein specific. In addition, N-protein promoted M1 macrophage polarization and the expression of proinflammatory cytokines, which was also blocked by N-protein denaturation and antibody for N-protein. Furthermore, N-protein induced NF-ĸB p65 phosphorylation in the lung, while pyrrolidine dithiocarbamate, an NF-ĸB inhibitor, alleviated the effect of N-protein on acute lung injury. Conclusions: SARS-CoV-2 N-protein itself is toxic and induces acute lung injury in mice. Both N-protein and NF-ĸB pathway may be therapeutic targets for treating multi-organ injuries in Coronavirus disease 2019 (COVID-19).