The current COVID-19 pandemic, caused by SARS-CoV-2, poses a serious public health threat. Effective therapeutic and prophylactic treatments are urgently needed. Angiotensin-converting enzyme 2 (ACE2) is a functional receptor for SARS-CoV-2, which binds to the receptor binding domain (RBD) of SARS-CoV-2 spike protein. Here, we developed recombinant human ACE2-Fc fusion protein (hACE2-Fc) and a hACE2-Fc mutant with reduced catalytic activity. hACE2-Fc and the hACE2-Fc mutant both efficiently blocked entry of SARS-CoV-2, SARS-CoV, and HCoV-NL63 into hACE2-expressing cells and inhibited SARS-CoV-2 S protein-mediated cell–cell fusion. hACE2-Fc also neutralized various SARS-CoV-2 strains with enhanced infectivity including D614G and V367F mutations, as well as the emerging SARS-CoV-2 variants, B.1.1.7 (Alpha), B.1.351 (Beta), B.1.617.1 (Kappa), and B.1.617.2 (Delta), demonstrating its potent and broad-spectrum antiviral effects. In addition, hACE2-Fc proteins protected HBE from SARS-CoV-2 infection. Unlike RBD-targeting neutralizing antibodies, hACE2-Fc treatment did not induce the development of escape mutants. Furthermore, both prophylactic and therapeutic hACE2-Fc treatments effectively protected mice from SARS-CoV-2 infection, as determined by reduced viral replication, weight loss, histological changes, and inflammation in the lungs. The protection provided by hACE2 showed obvious dose-dependent efficacy in vivo. Pharmacokinetic data indicated that hACE2-Fc has a relative long half-life in vivo compared to soluble ACE2, which makes it an excellent candidate for prophylaxis and therapy for COVID-19 as well as for SARS-CoV and HCoV-NL63 infections.

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BackgroundDiseases associated with Epstein-Barr virus (EBV) infections, such as infectious mononucleosis (IM), EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) and chronic active EBV infection (CAEBV) are not rare in Chinese children. The association of type 1 or type 2 EBV and variants of the EBV BZLF1 promoter zone (Zp) with these diseases is unclear.ResultsThe objective of this study was to investigate the relationship between EBV genotypes (Zp variants and EBV type 1 and 2) and the clinical phenotypes of EBV-associated diseases in Chinese children. The Zp region was directly sequenced in 206 EBV-positive DNA samples from the blood of patients with IM, EBV-HLH, CAEBV, and healthy controls. Type 1 or type 2 EBV was examined by PCR for EBNA2 and EBNA3C subtypes. Four polymorphic Zp variants were identified: Zp-P, Zp-V3, Zp-P4 and Zp-V1, a new variant. The Zp-V3 variant was significantly associated with CAEBV (P ≤ 0.01). The frequency of co-infection with Zp variants was higher in patients with CAEBV and EBV-HLH, compared with IM and healthy controls, mostly as Zp-P+V3 co-infection. Type 1 EBV was predominant in all categories (81.3-95%) and there was no significant difference in the frequency of the EBV types 1 and 2 in different categories (P > 0.05).ConclusionsType 1 EBV and BZLF1 Zp-P of EBV were the predominant genotypes in nonmalignant EBV associated diseases in Chinese children and Zp-V3 variant may correlates with the developing of severe EBV infection diseases, such as CAEBV and EBV-HLH.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening immune disorder that may be inherited or secondary to infection, malignancy or rheumatological disease. The aim of the present study was to highlight the clinical features of scrub typhus-associated HLH in children. A retrospective study was performed on 6 pediatric patients with scrub typhus-associated HLH. For each patient, medical records were reviewed and analyzed, and demographic, clinical and laboratory data and outcomes were collected. The duration of fever prior to admission ranged between 4 and 12 days. All patients exhibited persistent or intermittent fever, eschar, hepatosplenomegaly and lymphadenopathy at the time of diagnosis. Five patients experienced acute respiratory distress syndrome and disseminated intravascular coagulation (DIC) during hospitalization. Thrombocytopenia was detected in all patients with cytopenia involving two or three cell types, simultaneously. Coagulopathy with prolonged prothrombin time and/or activated partial thromboplastin time were noted in all patients. Markedly elevated serum ferritin levels (>1,500 µg/ml) were identified in all patients. Elevated lactate dehydrogenase (>1,000 U/l) was detected in 4 (66.7%) patients and elevated alanine aminotransferase was exhibited by 5 (83/3%) patients. Lung infiltrates and consolidation were the most common imaging findings. Only 1 patient succumbed, with DIC and multi-organ failure. Of the survivors, 1 patient was lost to follow-up, and the remaining patients are in remission with excellent general health, to date. In conclusion, HLH should be considered in severe pediatric cases of scrub typhus. Upon the early recognition of this syndrome, prompt and supportive treatment in the pediatric intensive care unit are vital.

Background Talaromyces marneffei (T. marneffei) is an opportunistic pathogen that infects immunodeficient children. The aim of the study is to determine the clinical features and peripheral immune state of Talaromyces marneffei (T. marneffei) infections in children for early detection and diagnosis. Methods We retrospectively reviewed 21 pediatric patients who were diagnosed with T. marneffei infections and were followed up in the Guangzhou Women and Children’s Medical Center from January 2010 to January 2020. For each patient, we collected and analyzed clinical characteristics, peripheral immunological results, genetic tests, complications and prognosis. Results Common clinical features of the patients included fever (20/21, 95.24%), cough (17/21, 80.95%) and hepatomegaly (17/21, 80.95%). Severe complications included septic shock (12/21, 57.14%), hemophagocytic lymphohistiocytosis (HLH) (11/21, 52.38%), acute respiratory distress syndrome (ARDS) (10/21, 47.62%), multiple organ dysfunction syndrome (MODS) (9/21, 42.86%), and disseminated intravascular coagulation (DIC) (7/21, 33.33%). Eleven children (11/21, 52.38%) eventually died of T. marneffei infections. All patients were HIV negative. Seven cases revealed reduced antibody levels, especially IgG. Higher levels of IgE were detected in 9 cases with an obvious increase in two patients. Ten patients showed decreased complement C3 levels, some of whom had low C4 levels. Three patients displayed decreased absolute T lymphocyte counts, including the CD 4+ and CD 8+ subsets. A reduction in NK cells was present in most patients. No patient had positive nitro blue tetrazolium (NBT) test results. Nine patients were screened for common genetic mutations. Of the cases, one case had no disease-specific gene mutation. Four children had confirmed hyperimmunoglobulin M syndrome (HIGM) with CD40LG variation, one case had severe combined immunodeficiency (SCID), and one case had hyper-IgE syndrome (HIES). One patient was identified as having a heterozygous mutation in STAT3 gene; however, he showed no typical clinical manifestations of HIES at his age. One patient had a mutated COPA gene with uncertain pathogenic potential. Another patient was diagnosed with HIES that depended on her clinical features and the National Institutes of Health (NIH) scoring system. Conclusions T. marneffei infections in HIV-negative children induced severe systemic complications and poor prognosis. Children with T. marneffei infections commonly exhibited abnormal immunoglobulin levels in peripheral blood, particularly decreased IgG or increased IgE levels, further suggesting possible underlying PIDs in these patients.

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Middle East respiratory syndrome coronavirus (MERS-CoV) is a beta coronavirus that emerged in 2012, causing severe pneumonia and renal failure. MERS-CoV encodes five accessory proteins. Some of them have been shown to interfere with host antiviral immune response. However, the roles of protein 8b in innate immunity and viral virulence was rarely studied. Here, we introduced individual MERS-CoV accessory protein genes into the genome of an attenuated murine coronavirus (Mouse hepatitis virus, MHV), respectively and found accessory protein 8b could enhance viral replication in vivo and in vitro , and increase the lethality of infected mice. RNA-seq analysis revealed that protein 8b could significantly inhibit type I interferon production (IFN-I) and innate immune response in mice infected with MHV expressing protein 8b. We also found that MERS-CoV protein 8b could initiate from multiple internal methionine sites and at least three protein variants were identified. Residues 1-23 of protein 8b was demonstrated to be responsible for increased virulence in vivo . In addition, the inhibitory effect on IFN-I of protein 8b might not contribute to its virulence enhancement as aa1-23 deletion did not affect IFN-I production in vitro and in vivo . Next, we also found that protein 8b was localized to the endoplasmic reticulum (ER)/Golgi membrane in infected cells, which was disrupted by C-terminal region aa 88-112 deletion. This study will provide new insight into the pathogenesis of MERS-CoV infection. IMPORTANCE Multiple coronaviruses (CoV) cause severe respiratory infections and become global public health threats such as SARS-CoV, MERS-CoV, and SARS-CoV-2. Each coronavirus contains different numbers of accessory proteins which show high variability among different CoVs. Accessory proteins are demonstrated to play essential roles in pathogenesis of CoVs. MERS-CoV contains 5 accessory proteins (protein 3, 4a, 4b, 5, 8b), and deletion of all four accessory proteins (protein 3, 4a, 4b, 5), significantly affects MERS-CoV replication and pathogenesis. However, whether ORF8b also regulates MERS-CoV infection is unknown. Here, we constructed mouse hepatitis virus (MHV) recombinant virus expressing MERS-CoV protein 8b and demonstrated protein 8b could significantly enhance the virulence of MHV, which is mediated by N-terminal domain of protein 8b. This study will shed light on the understanding of pathogenesis of MERS-CoV infection.

Human coronavirus 229E (HCoV-229E) and NL63 (HCoV-NL63) are endemic causes of upper respiratory infections such as the “common cold” but may occasionally cause severe lower respiratory tract disease in the elderly and immunocompromised patients. There are no approved antiviral drugs or vaccines for these common cold coronaviruses (CCCoV). The recent emergence of COVID-19 and the possible cross-reactive antibody and T cell responses between these CCCoV and SARS-CoV-2 emphasize the need to develop experimental animal models for CCCoV. Mice are an ideal experimental animal model for such studies, but are resistant to HCoV-229E and HCoV-NL63 infections. Here, we generated 229E and NL63 mouse models by exogenous delivery of their receptors, human hAPN and hACE2 using replication-deficient adenoviruses (Ad5-hAPN and Ad5-hACE2), respectively. Ad5-hAPN- and Ad5-hACE2-sensitized IFNAR −/− and STAT1 −/− mice developed pneumonia characterized by inflammatory cell infiltration with virus clearance occurring 7 d post infection. Ad5-hAPN- and Ad5-hACE2-sensitized mice generated virus-specific T cells and neutralizing antibodies after 229E or NL63 infection, respectively. Remdesivir and a vaccine candidate targeting spike protein of 229E and NL63 accelerated viral clearance of virus in these mice. 229E- and NL63-infected mice were partially protected from SARS-CoV-2 infection, likely mediated by cross-reactive T cell responses. Ad5-hAPN- and Ad5-hACE2-transduced mice are useful for studying pathogenesis and immune responses induced by HCoV-229E and HCoV-NL63 infections and for validation of broadly protective vaccines, antibodies, and therapeutics against human respiratory coronaviruses including SARS-CoV-2.