Azvudine is a thymus-homing anti-SARS-CoV-2 drug effective in treating COVID-19 patients.

Azvudine (FNC) is a nucleoside analog that inhibits HIV-1 RNA-dependent RNA polymerase (RdRp). Recently, we discovered FNC an agent against SARS-CoV-2, and have taken it into Phase III trial for COVID-19 patients. FNC monophosphate analog inhibited SARS-CoV-2 and HCoV-OC43 coronavirus with an EC50 between 1.2 and 4.3 µM, depending on viruses or cells, and selective index (SI) in 15-83 range. Oral administration of FNC in rats revealed a substantial thymus-homing feature, with FNC triphosphate (the active form) concentrated in the thymus and peripheral blood mononuclear cells (PBMC). Treating SARS-CoV-2 infected rhesus macaques with FNC (0.07 mg/kg, qd, orally) reduced viral load, recuperated the thymus, improved lymphocyte profiles, alleviated inflammation and organ damage, and lessened ground-glass opacities in chest X-ray. Single-cell sequencing suggested the promotion of thymus function by FNC. A randomized, single-arm clinical trial of FNC on compassionate use (n = 31) showed that oral FNC (5 mg, qd) cured all COVID-19 patients, with 100% viral ribonucleic acid negative conversion in 3.29 ± 2.22 days (range: 1-9 days) and 100% hospital discharge rate in 9.00 ± 4.93 days (range: 2-25 days). The side-effect of FNC is minor and transient dizziness and nausea in 16.12% (5/31) patients. Thus, FNC might cure COVID-19 through its anti-SARS-CoV-2 activity concentrated in the thymus, followed by promoted immunity.

The olfactory route is a potential way for SARS-CoV-2 to invade the central nervous system of rhesus monkeys.

Neurological manifestations are frequently reported in the COVID-19 patients. Neuromechanism of SARS-CoV-2 remains to be elucidated. In this study, we explored the mechanisms of SARS-CoV-2 neurotropism via our established non-human primate model of COVID-19. In rhesus monkey, SARS-CoV-2 invades the CNS primarily via the olfactory bulb. Thereafter, viruses rapidly spread to functional areas of the central nervous system, such as hippocampus, thalamus, and medulla oblongata. The infection of SARS-CoV-2 induces the inflammation possibly by targeting neurons, microglia, and astrocytes in the CNS. Consistently, SARS-CoV-2 infects neuro-derived SK-N-SH, glial-derived U251, and brain microvascular endothelial cells in vitro. To our knowledge, this is the first experimental evidence of SARS-CoV-2 neuroinvasion in the NHP model, which provides important insights into the CNS-related pathogenesis of SARS-CoV-2.

[Clinical efficacy and safety of different antiviral regimens in patients with coronavirus disease 2019].

OBJECTIVE: To investigate the clinical efficacy and short-term and long-term adverse reactions for different antiviral regiments for coronavirus disease 2019 (COVID-19) in Ningxia Hui Autonomous Region during hospitalization and follow-up in 3 months. METHODS: A single-center retrospective study was conducted to enroll the COVID-19 patients in isolation ward of the only designated hospital to receive COVID-19 patients (the Fourth People's Hospital of Ningxia Hui Autonomous Region) when the authors were assigned by the Ningxia Health Commission as experts from January 20, 2020 to March 15, 2020. According to the antiviral regimen, the patients were divided into conventional antiviral group and unconventional antiviral group. The conventional antiviral group received α-interferon combined with Lopinavir/Ritonavir (LPV/R). The unconventional antiviral group was given α-interferon combined with LPV/R and Abidor or Ribavirin or Chloroquine. The patients were divided into mild (13 cases), ordinary (45 cases), severe (14 cases) and critical (1 case) types. The clinical data, length of hospital stay, the first 2019 novel coronavirus (2019-nCoV) nucleic acid negative recovery time, cost of hospitalization, 2019-nCoV nucleic acid positive reversal after 14 days of discharge, and the combination of hormones and antibiotics were collected. The differences in blood routine, liver function, blood lipid level and adverse reactions of antiviral drugs during hospitalization were compared between the two groups at 1, 3 and 7 days after admission and 1 and 3 months after discharge. RESULTS: (1) General information: a total of 75 patients with confirmed COVID-19 were admitted, and 73 patients were eventually enrolled, including 47 cases in the conventional antiviral group and 26 cases in the unconventional antiviral group. Patients with different clinical classification were analyzed, the higher the clinical classification and the patients' age, the higher the proportion of primary diseases and the cost of treatment, and the longer the length of hospital stay. Compared with conventional antiviral group, in unconventional antiviral group the percentage of severe and critical patients were higher [34.6% (9/26) vs. 10.6% (5/47), 3.8% (1/26) vs. 0 (0/47)], the length of hospital stay (days: 16.1±5.6 vs. 11.6±3.3), first nucleic acid negative recovery time (days: 12.4±4.5 vs. 10.0±3.5) were longer, and hospitalization cost was higher [Yuan: 11 984.2 (9 000.6, 24 424.7) vs. 8 140.4 (6 715.7,9 707.7)], with statistically significant differences (all P < 0.05). There were no significant differences in gender, age, proportion of patients with primary diseases and nucleic acid positive reversal rate after 14 days of discharge between the unconventional and conventional antiviral groups (all P > 0.05). (2) Laboratory tests: during the hospitalization, white blood cell count (WBC), platelet count (PLT), total bilirubin (TBil) and three acyl glycerin (TG) levels were first increased and then reduced, lymphocyte count (LYM) was first decreased and then increased in two groups. In the unconventional antiviral group, WBC [(6.53±2.78)×109/L], PLT [(250.77±96.12)×109/L], and TG [(1.94±0.96) µmol/L] all reached their peak values at 7 days after admission. TBil peaked at 3 days after admission, which was (23.69±12.14) µmol/L, and LYM reached the peak 1 month after discharge, which was (1.82±0.50)×109/L; however, there was no statistical significance among the above indicators between two groups. There were no statistically significant differences in alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total cholesterol (TC) between the two groups at each time point. (3) The ratio of combined use of hormones in the non-antiviral group was significantly higher than that in the conventional antiviral group [26.9% (7/26) vs. 4.3% (2/47), P < 0.05]. CONCLUSIONS: Age and associated primary diseases are related to the severity of COVID-19 patients. Unconventional antiviral treatment regimens are mostly used for severe COVID-19 patients whose ucleic acid did not turn negative for a long time. Individual antiviral therapy can be used based on the patients' response and tolerance to drugs.

The Gastrointestinal Tract Is an Alternative Route for SARS-CoV-2 Infection in a Nonhuman Primate Model.

BACKGROUND & AIMS: Gastrointestinal (GI) manifestations have been increasingly reported in patients with coronavirus disease 2019 (COVID-19). However, the roles of the GI tract in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are not fully understood. We investigated how the GI tract is involved in SARS-CoV-2 infection to elucidate the pathogenesis of COVID-19. METHODS: Our previously established nonhuman primate (NHP) model of COVID-19 was modified in this study to test our hypothesis. Rhesus monkeys were infected with an intragastric or intranasal challenge with SARS-CoV-2. Clinical signs were recorded after infection. Viral genomic RNA was quantified by quantitative reverse transcription polymerase chain reaction. Host responses to SARS-CoV-2 infection were evaluated by examining inflammatory cytokines, macrophages, histopathology, and mucin barrier integrity. RESULTS: Intranasal inoculation with SARS-CoV-2 led to infections and pathologic changes not only in respiratory tissues but also in digestive tissues. Expectedly, intragastric inoculation with SARS-CoV-2 resulted in the productive infection of digestive tissues and inflammation in both the lung and digestive tissues. Inflammatory cytokines were induced by both types of inoculation with SARS-CoV-2, consistent with the increased expression of CD68. Immunohistochemistry and Alcian blue/periodic acid-Schiff staining showed decreased Ki67, increased cleaved caspase 3, and decreased numbers of mucin-containing goblet cells, suggesting that the inflammation induced by these 2 types of inoculation with SARS-CoV-2 impaired the GI barrier and caused severe infections. CONCLUSIONS: Both intranasal and intragastric inoculation with SARS-CoV-2 caused pneumonia and GI dysfunction in our rhesus monkey model. Inflammatory cytokines are possible connections for the pathogenesis of SARS-CoV-2 between the respiratory and digestive systems.

Susceptibility of tree shrew to SARS-CoV-2 infection.

Since severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) became a pandemic event in the world, it has not only caused huge economic losses, but also a serious threat to global public health. Many scientific questions about SARS-CoV-2 and Coronavirus disease (COVID-19) were raised and urgently need to be answered, including the susceptibility of animals to SARS-CoV-2 infection. Here we tested whether tree shrew, an emerging experimental animal domesticated from wild animal, is susceptible to SARS-CoV-2 infection. No clinical signs were observed in SARS-CoV-2 inoculated tree shrews during this experiment except the increasing body temperature particularly in female animals. Low levels of virus shedding and replication in tissues occurred in all three age groups. Notably, young tree shrews (6 months to 12 months) showed virus shedding at the earlier stage of infection than adult (2 years to 4 years) and old (5 years to 7 years) animals that had longer duration of virus shedding comparatively. Histopathological examine revealed that pulmonary abnormalities were the main changes but mild although slight lesions were also observed in other tissues. In summary, tree shrew is less susceptible to SARS-CoV-2 infection compared with the reported animal models and may not be a suitable animal for COVID-19 related researches. However, tree shrew may be a potential intermediate host of SARS-CoV-2 as an asymptomatic carrier.

Comparison of nonhuman primates identified the suitable model for COVID-19.

Identification of a suitable nonhuman primate (NHP) model of COVID-19 remains challenging. Here, we characterized severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in three NHP species: Old World monkeys Macaca mulatta (M. mulatta) and Macaca fascicularis (M. fascicularis) and New World monkey Callithrix jacchus (C. jacchus). Infected M. mulatta and M. fascicularis showed abnormal chest radiographs, an increased body temperature and a decreased body weight. Viral genomes were detected in swab and blood samples from all animals. Viral load was detected in the pulmonary tissues of M. mulatta and M. fascicularis but not C. jacchus. Furthermore, among the three animal species, M. mulatta showed the strongest response to SARS-CoV-2, including increased inflammatory cytokine expression and pathological changes in the pulmonary tissues. Collectively, these data revealed the different susceptibilities of Old World and New World monkeys to SARS-CoV-2 and identified M. mulatta as the most suitable for modeling COVID-19.

The pathogenicity of SARS-CoV-2 in hACE2 transgenic mice.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of coronavirus disease 2019 (COVID-19), which has become a public health emergency of international concern1. Angiotensin-converting enzyme 2 (ACE2) is the cell-entry receptor for severe acute respiratory syndrome coronavirus (SARS-CoV)2. Here we infected transgenic mice that express human ACE2 (hereafter, hACE2 mice) with SARS-CoV-2 and studied the pathogenicity of the virus. We observed weight loss as well as virus replication in the lungs of hACE2 mice infected with SARS-CoV-2. The typical histopathology was interstitial pneumonia with infiltration of considerable numbers of macrophages and lymphocytes into the alveolar interstitium, and the accumulation of macrophages in alveolar cavities. We observed viral antigens in bronchial epithelial cells, macrophages and alveolar epithelia. These phenomena were not found in wild-type mice infected with SARS-CoV-2. Notably, we have confirmed the pathogenicity of SARS-CoV-2 in hACE2 mice. This mouse model of SARS-CoV-2 infection will be valuable for evaluating antiviral therapeutic agents and vaccines, as well as understanding the pathogenesis of COVID-19.