MxB inhibits long interspersed element type 1 retrotransposition.

Long interspersed element type 1 (LINE-1, also L1 for short) is the only autonomously transposable element in the human genome. Its insertion into a new genomic site may disrupt the function of genes, potentially causing genetic diseases. Cells have thus evolved a battery of mechanisms to tightly control LINE-1 activity. Here, we report that a cellular antiviral protein, myxovirus resistance protein B (MxB), restricts the mobilization of LINE-1. This function of MxB requires the nuclear localization signal located at its N-terminus, its GTPase activity and its ability to form oligomers. We further found that MxB associates with LINE-1 protein ORF1p and promotes sequestration of ORF1p to G3BP1-containing cytoplasmic granules. Since knockdown of stress granule marker proteins G3BP1 or TIA1 abolishes MxB inhibition of LINE-1, we conclude that MxB engages stress granule components to effectively sequester LINE-1 proteins within the cytoplasmic granules, thus hindering LINE-1 from accessing the nucleus to complete retrotransposition. Thus, MxB protein provides one mechanism for cells to control the mobility of retroelements.

Residual Immunity from Smallpox Vaccination and Possible Protection from Mpox, China.

Among persons born in China before 1980 and tested for vaccinia virus Tiantan strain (VVT), 28.7% (137/478) had neutralizing antibodies, 71.4% (25/35) had memory B-cell responses, and 65.7% (23/35) had memory T-cell responses to VVT. Because of cross-immunity between the viruses, these findings can help guide mpox vaccination strategies in China.

SERINC5 restricts influenza virus infectivity.

SERINC5 is a multi-span transmembrane protein that is incorporated into HIV-1 particles in producing cells and inhibits HIV-1 entry. Multiple retroviruses like HIV-1, equine infectious anemia virus and murine leukemia virus are subject to SERINC5 inhibition, while HIV-1 pseudotyped with envelope glycoproteins of vesicular stomatitis virus and Ebola virus are resistant to SERINC5. The antiviral spectrum and the underlying mechanisms of SERINC5 restriction are not completely understood. Here we show that SERINC5 inhibits influenza A virus infection by targeting virus-cell membrane fusion at an early step of infection. Further results show that different influenza hemagglutinin (HA) subtypes exhibit diverse sensitivities to SERINC5 restriction. Analysis of the amino acid sequences of influenza HA1 strains indicates that HA glycosylation sites correlate with the sensitivity of influenza HA to SERINC5, and the inhibitory effect of SERINC5 was lost when certain HA glycosylation sites were mutated. Our study not only expands the antiviral spectrum of SERINC5, but also reveals the role of viral envelope glycosylation in resisting SERINC5 restriction.

Pro-515 of the dynamin-like GTPase MxB contributes to HIV-1 inhibition by regulating MxB oligomerization and binding to HIV-1 capsid.

Interferon-regulated myxovirus resistance protein B (MxB) is an interferon-induced GTPase belonging to the dynamin superfamily. It inhibits infection with a wide range of different viruses, including HIV-1, by impairing viral DNA entry into the nucleus. Unlike the related antiviral GTPase MxA, MxB possesses an N-terminal region that contains a nuclear localization signal and is crucial for inhibiting HIV-1. Because MxB previously has been shown to reside in both the nuclear envelope and the cytoplasm, here we used bioinformatics and biochemical approaches to identify a nuclear export signal (NES) responsible for MxB's cytoplasmic location. Using the online computational tool LocNES (Locating Nuclear Export Signals or NESs), we identified five putative NES candidates in MxB and investigated whether their deletion caused nuclear localization of MxB. Our results revealed that none of the five deletion variants relocates to the nucleus, suggesting that these five predicted NES sequences do not confer NES activity. Interestingly, deletion of one sequence, encompassing amino acids 505-527, abrogated the anti-HIV-1 activity of MxB. Further mutation experiments disclosed that amino acids 515-519, and Pro-515 in particular, regulate MxB oligomerization and its binding to HIV-1 capsid, thereby playing an important role in MxB-mediated restriction of HIV-1 infection. In summary, our results indicate that none of the five predicted NES sequences in MxB appears to be required for its nuclear export. Our findings also reveal several residues in MxB, including Pro-515, critical for its oligomerization and anti-HIV-1 function.

Development of a multiplex real-time PCR assay for the simultaneous detection of mpox virus and orthopoxvirus infections.

Since May 2022, the multi-country outbreak of monkeypox (mpox) has raised a great concern worldwide. Early detection of mpox virus infection is recognized as an efficient way to prevent mpox transmission. Mpox specific detection methods reported up to now are based on the SNPs among mpox virus and other orthopoxviruses. We have therefore developed a real-time PCR based mpox detection method targeting mpox virus specific sequences (N3R and B18Rplus). We have also optimized an orthopoxvirus detection system which targets the highly conserved E9L and D6R genes. The mpox and orthopoxvirus real-time PCR assays have a high sensitivity (1 copy/reaction) and specificity. Mpox viral DNA and clinical samples from mpox patients are detected with the mpox detection system. Furthermore, we have established a multiplex real-time PCR detection system allowing simultaneous and efficient detection of mpox and orthopoxvirus infections.

Rapid and sensitive one-tube detection of mpox virus using RPA-coupled CRISPR-Cas12 assay.

Mpox is caused by a zoonotic virus belonging to the Orthopoxvirus genus and the Poxviridae family. In this study, we develop a recombinase polymerase amplification (RPA)-coupled CRISPR-Cas12a detection assay for the mpox virus. We design and test a series of CRISPR-derived RNAs(crRNAs) targeting the conserved D6R and E9L genes for orthopoxvirus and the unique N3R and N4R genes for mpox viruses. D6R crRNA-1 exhibits the most robust activity in detecting orthopoxviruses, and N4R crRNA-2 is able to distinguish the mpox virus from other orthopoxviruses. The Cas12a/crRNA assay alone presents a detection limit of 108 copies of viral DNA, whereas coupling RPA increases the detection limit to 1-10 copies. The one-tube RPA-Cas12a assay can, therefore, detect viral DNA as low as 1 copy within 30 min and holds the promise of providing point-of-care detection for mpox viral infection.

SARS-CoV-2 spike protein-induced cell fusion activates the cGAS-STING pathway and the interferon response.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the unprecedented coronavirus disease 2019 (COVID-19) pandemic. Critical cases of COVID-19 are characterized by the production of excessive amounts of cytokines and extensive lung damage, which is partially caused by the fusion of SARS-CoV-2-infected pneumocytes. Here, we found that cell fusion caused by the SARS-CoV-2 spike (S) protein induced a type I interferon (IFN) response. This function of the S protein required its cleavage by proteases at the S1/S2 and the S2' sites. We further showed that cell fusion damaged nuclei and resulted in the formation of micronuclei that were sensed by the cytosolic DNA sensor cGAS and led to the activation of its downstream effector STING. Phosphorylation of the transcriptional regulator IRF3 and the expression of IFNB, which encodes a type I IFN, were abrogated in cGAS-deficient fused cells. Moreover, infection with VSV-SARS-CoV-2 also induced cell fusion, DNA damage, and cGAS-STING-dependent expression of IFNB. Together, these results uncover a pathway underlying the IFN response to SARS-CoV-2 infection. Our data suggest a mechanism by which fused pneumocytes in the lungs of patients with COVID-19 may enhance the production of IFNs and other cytokines, thus exacerbating disease severity.

Immunogenicity of a vaccinia virus-based severe acute respiratory syndrome coronavirus 2 vaccine candidate.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines provide essential tools for the control of the COVID-19 pandemic. A number of technologies have been employed to develop SARS-CoV-2 vaccines, including the inactivated SARS-CoV-2 particles, mRNA to express viral spike protein, recombinant spike proteins, and viral vectors. Here, we report the use of the vaccinia virus Tiantan strain as a vector to express the SARS-CoV-2 spike protein. When it was used to inoculate mice, robust SARS-CoV-2 spike protein-specific antibody response and T-cell response were detected. Sera from the vaccinated mice showed strong neutralizing activity against the ancestral Wuhan SARS-CoV-2, the variants of concern (VOCs) B.1.351, B.1.617.2, and the emerging B.1.1.529 (omicron). This finding supports the possibility of developing a new type of SARS-CoV-2 vaccine using the vaccinia virus vector.

IFITM3 Inhibits SARS-CoV-2 Infection and Is Associated with COVID-19 Susceptibility.

SARS-CoV-2 has become a global threat to public health. Infected individuals can be asymptomatic or develop mild to severe symptoms, including pneumonia, respiratory distress, and death. This wide spectrum of clinical presentations of SARS-CoV-2 infection is believed in part due to the polymorphisms of key genetic factors in the population. In this study, we report that the interferon-induced antiviral factor IFITM3 inhibits SARS-CoV-2 infection by preventing SARS-CoV-2 spike-protein-mediated virus entry and cell-to-cell fusion. Analysis of a Chinese COVID-19 patient cohort demonstrates that the rs12252 CC genotype of IFITM3 is associated with SARS-CoV-2 infection risk in the studied cohort. These data suggest that individuals carrying the rs12252 C allele in the IFITM3 gene may be vulnerable to SARS-CoV-2 infection and thus may benefit from early medical intervention.

MARCH8 inhibits influenza A virus infection by targeting viral M2 protein for ubiquitination-dependent degradation in lysosomes.

The membrane-associated RING-CH (MARCH) proteins are E3 ligases that regulate the stability of various cellular membrane proteins. MARCH8 has been reported to inhibit the infection of HIV-1 and a few other viruses, thus plays an important role in host antiviral defense. However, the antiviral spectrum and the underlying mechanisms of MARCH8 are incompletely defined. Here, we demonstrate that MARCH8 profoundly inhibits influenza A virus (IAV) replication both in vitro and in mice. Mechanistically, MARCH8 suppresses IAV release through redirecting viral M2 protein from the plasma membrane to lysosomes for degradation. Specifically, MARCH8 catalyzes the K63-linked polyubiquitination of M2 at lysine residue 78 (K78). A recombinant A/Puerto Rico/8/34 virus carrying the K78R M2 protein shows greater replication and more severe pathogenicity in cells and mice. More importantly, we found that the M2 protein of the H1N1 IAV has evolved to acquire non-lysine amino acids at positions 78/79 to resist MARCH8-mediated ubiquitination and degradation. Together, our data support the important role of MARCH8 in host anti-IAV intrinsic immune defense by targeting M2, and suggest the inhibitory pressure of MARCH8 on H1N1 IAV transmission in the human population.

Bone Autophagy: A Potential Way of Exercise-Mediated Meg3/P62/Runx2 Pathway to Regulate Bone Formation in T2DM Mice.

BACKGROUND: Meg3 has been shown to attenuate T2DM bone autophagy by activating p62 to inhibit bone formation. However, whether exercise can reverse this process to promote T2DM bone formation and its mechanism remains unknown. METHODS: A T2DM mouse model was established by a high-fat diet and STZ injection, and the mice were trained with 8-week HIIT and downhill running exercise. Micro-CT was used to scan the bone microstructure. Bone morphology was observed by HE staining, and the osteoblast (OB) activity in bones was observed by AKP staining. Calcium ion and phosphorus concentration in serum was detected by ELISA; RT-PCR was used to detect the mRNA level, and Western blot was used to detect the protein level of related indexes in Meg3/p62/Runx2 pathway. RESULTS: The inhibition of bone autophagy, in the bones of T2DM mice, resulted in the degradation of the bone tissue morphology and structure, with the increase of the expressions of Meg3, PI3K, Akt, mTOR, p62 and NF-κB. However, 8-week HIIT and downhill running could reverse this process, especially downhill running, manifested with the up-regulation of miR-16 mRNA level, along with Beclin-1, LC3 II and Runx2 mRNA and protein level. CONCLUSION: T2DM leads to pathology in model mice. Eight-week HIIT and downhill running exercise can inhibit Meg3, activate autophagy of osteoblasts and promote bone formation in T2DM mice.

The Engineered MARCH8-Resistant Vesicular Stomatitis Virus Glycoprotein Enhances Lentiviral Vector Transduction.

Lentiviral vectors are one of the most commonly used viral delivery systems for gene therapy. Vesicular stomatitis virus-G envelope glycoprotein (VSV G)-pseudotyped lentiviral vectors have been widely used in clinical studies for treatment of virus infections and genetic deficient diseases. However, the efficiency of lentiviral vector transduction has been long recognized as a limiting factor in clinical gene therapy application, especially in transducing hematopoietic stem cells. MARCH8 (membrane-associated RING-CH 8), an E3 ubiquitin ligase, has been reported to target and downregulate VSV G. Results in this study show that MARCH8 induces ubiquitination and lysosome degradation of VSV G, and knockout of MARCH8 in virus-producing cells increases lentiviral vector transduction by elevating the level of VSV G protein. We then engineered VSV G mutant that has the lysine residues in the cytoplasmic domain substituted for arginine, and showed that this G mutant resists degradation by MARCH8, and allows the enhancement of transduction efficiency of lentiviral vector particles than the parental VSV G protein. This engineered VSV G mutant thus further advances the lentiviral vector system as a powerful tool in gene therapy.

Listeriosis in mainland China: A systematic review.

OBJECTIVE: The aim of this study was to conduct a systematic review to better understand the epidemiological and clinical characteristics of listeriosis patients in mainland China. METHODS: The six most widely used Chinese and English language databases were searched. The records of patients with listeriosis in mainland China reported during the years 2011-2017 were extracted. The clinical data of patients and information on clinical isolates of Listeria were collected and analyzed. RESULTS: In total, 136 records were identified, reporting 562 patients with listeriosis. The number of patients was much higher than that reported in the previous decade. The 227 non-perinatal listeriosis patients included had a mortality rate of 23.78%. Of the 231 perinatal listeriosis patients, 32.68% resulted in abortion and/or newborn death. All listeriosis cases were reported as being sporadic. The listeriosis was traced to infection via a meat product in only three patients, while 33.12% were healthcare-associated infections. CONCLUSIONS: The number of patients with listeriosis in mainland China may have been underestimated previously. Perinatal cases in mainland China account for a much higher proportion than is usually described. Considering the high number of listeriosis patients in China, a comprehensive monitoring system for Listeria is urgently needed.

High initial (1, 3) Beta-d-Glucan concentration may be a predictor of satisfactory response of c aspofungin combined with TMP/SMZ for HIV-negative patients with moderate to severe Pneumocystis jirovecii pneumonia.

OBJECTIVES: The aim of this study was to investigate the efficacy of combination therapy of caspofungin and TMP/SMZ (trimethoprim/sulfamethoxazole) in moderate to severe pneumocystis jirovecii pneumonia (PJP) in patients without human immunodeficiency virus infection (HIV) and the relationship between therapeutic effect and plasma (1, 3) Beta-d-Glucan (BDG) levels. METHODS: We retrospectively reviewed HIV-negative patients with PJP diagnosed in our department, who were treated with combination therapy of caspofungin and TMP/SMZ or monotherapy of TMP/SMZ during a six and a half year period. RESULTS: A total of 126 moderate to severe PJP patients were enrolled in the study. In the multivariate analysis, low lymphocyte counts, high serum lactate dehydrogenase levels at the diagnosis of PJP and progression to shock were significant risk factors for death. In all patients, there was no significant difference in risk of death at 3 months. In the group of BDG≥800pg/m, patients receiving combination therapy was associated with a significantly decreased risk of death at 3 months, whereas in the group of BDG<800pg/ml, there were no statistically significant difference in survival rate between the two treatment regimens. CONCLUSION: High initial plasma (1, 3) Beta-d-Glucan concentration may be a predictor of satisfactory caspofungin response to HIV-negative patients with PJP. Based on our findings, we suggest the choice of combination therapy with caspofungin and TMP/SMZ as the initial treatment when BDG≥800pg/ml in moderate to severe HIV-negative patients with PJP.