Cathepsin L plays a key role in SARS-CoV-2 infection in humans and humanized mice and is a promising target for new drug development.

To discover new drugs to combat COVID-19, an understanding of the molecular basis of SARS-CoV-2 infection is urgently needed. Here, for the first time, we report the crucial role of cathepsin L (CTSL) in patients with COVID-19. The circulating level of CTSL was elevated after SARS-CoV-2 infection and was positively correlated with disease course and severity. Correspondingly, SARS-CoV-2 pseudovirus infection increased CTSL expression in human cells in vitro and human ACE2 transgenic mice in vivo, while CTSL overexpression, in turn, enhanced pseudovirus infection in human cells. CTSL functionally cleaved the SARS-CoV-2 spike protein and enhanced virus entry, as evidenced by CTSL overexpression and knockdown in vitro and application of CTSL inhibitor drugs in vivo. Furthermore, amantadine, a licensed anti-influenza drug, significantly inhibited CTSL activity after SARS-CoV-2 pseudovirus infection and prevented infection both in vitro and in vivo. Therefore, CTSL is a promising target for new anti-COVID-19 drug development.

[A follow up study of total IgM, IgG, nucleoprotein and spike protein antibodies against severe acute respiratory syndrome (SARS) coronavirus in patients with SARS].

OBJECTIVE: To survey the dynamic changing and persistence of the special antibodies, including total IgM, IgG, nucleocapsid protein and spike protein antibodies, against severe acute respiratory syndrome coronavirus (SARS-CoV) in patients with SARS. METHODS: 146 cases, all clinically diagnosed as SARS with positive SARS-CoV IgG, were followed up. 362 serum samples were collected from the onset of the disease to 660 days afterward. Total IgM and IgG against SARS-CoV were tested with commercial ELISA kits. For recombinant nucleoprotein and spike protein, we developed an ELISA to test these two antibodies. RESULTS: Within 20 days of the onset, the positive rate of anti-SARS-CoV IgM was 46.5% (20/43); it reached a peak after 21 - 40 days (80.6%, 25/31). Then, the positive rate of IgM went down gradually to 8.2% (6/73) until 550 days after the onset. The patient's IgG positive rate was lower (34.9%, 15/43) than that of IgM within 20 days of the onset. Then it went up rapidly to 100%. It remained positive (98.6%, 70/71) until 600 - 660 days after the onset. When N-IgG and S-IgG were tested 40 days after the onset of the disease at three different times, the positive rate of N-IgG (92.5%, 37/40) was higher than that of S-IgG (67.5%, 27/40), but the two structure protein antibodies were always lower than the total IgG. CONCLUSIONS: In SARS patients with definite clinical and etiological diagnosis, the highest positive rate of the antibodies against SARS-CoV was found at 21 - 40 days after the onset. IgM disappeared almost 500 days (91.8%) after the onset. Total IgG positive rate could reach 100% and 98.6% and the positivity might persist nearly two years. So it is speculated that the total IgG antibody may be positive 3 to 5 years after infection, but it seems that N-IgG and S-IgG keep positive shorter in time than total IgG antibody.

[Liver histological changes after lamivudine treating in chronic hepatitis B patients with HBeAg positive].

OBJECTIVES: To investigate the histological changes in liver biopsy tissues taken from chronic hepatitis B patients with HBsAg and HBeAg positive and ALT abnormal after lamivudine therapy for one year. METHODS: Lamivudine was given orally at the dose of 100 mg once a day for one year. 101 patients were enrolled into this open-label study. Paired liver biopsies from patients with hepatitis B before and after therapy with lamivudine were studied. Blinded biopsies were evaluated by a histopathologist and scored according to Knodell's histology activity index(HAI). RESULTS: 53.5% (54/101), 51.5% (52/101) and 31.7% (32/101) patients had a reduction of their total hepatic HAI score, necroinflammation and fibrosis scores by >or=2 points or 1 points at the end of one year of lamivudine therapy, compared with their pretreatment values, respectively. There were significant reduction of HAI score, necroinflammation and fibrosis scores from 8.0+/-4.7 to 5.2+/-3.3 (t=7.358, P<0.01), from 5.9+/-3.8 to 3.6+/-2.5 (t=7.298, P<0.01), and from 2.1+/-1.2 to 1.6+/-1.2 (t=3.827, P<0.01), respectively. The histological improvement was independent on the HBeAg seroconvertion during the therapy. CONCLUSION: Significant improvement in liver histology, both necroinflammation and fibrosis, can be obtained in the majority of patients treated with lamivudine for one year.