Natto extract, a Japanese fermented soybean food, directly inhibits viral infections including SARS-CoV-2 in vitro.

Natto, a traditional Japanese fermented soybean food, is well known to be nutritious and beneficial for health. In this study, we examined whether natto impairs infection by viruses, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as well as bovine herpesvirus 1 (BHV-1). Interestingly, our results show that both SARS-CoV-2 and BHV-1 treated with a natto extract were fully inhibited infection to the cells. We also found that the glycoprotein D of BHV-1 was shown to be degraded by Western blot analysis and that a recombinant SARS-CoV-2 receptor-binding domain (RBD) was proteolytically degraded when incubated with the natto extract. In addition, RBD protein carrying a point mutation (UK variant N501Y) was also degraded by the natto extract. When the natto extract was heated at 100 °C for 10 min, the ability of both SARS-CoV-2 and BHV-1 to infect to the cells was restored. Consistent with the results of the heat inactivation, a serine protease inhibitor inhibited anti-BHV-1 activity caused by the natto extract. Thus, our findings provide the first evidence that the natto extract contains a protease(s) that inhibits viral infection through the proteolysis of the viral proteins.

Covid-19 and oral diseases: Crosstalk, synergy or association?

The coronavirus disease 2019 (Covid-19) is a viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that clinically affects multiple organs of the human body. Cells in the oral cavity express viral entry receptor angiotensin-converting enzyme 2 that allows viral replication and may cause tissue inflammation and destruction. Recent studies have reported that Covid-19 patients present oral manifestations with multiple clinical aspects. In this review, we aim to summarise main signs and symptoms of Covid-19 in the oral cavity, its possible association with oral diseases, and the plausible underlying mechanisms of hyperinflammation reflecting crosstalk between Covid-19 and oral diseases. Ulcers, blisters, necrotising gingivitis, opportunistic coinfections, salivary gland alterations, white and erythematous plaques and gustatory dysfunction were the most reported clinical oral manifestations in patients with Covid-19. In general, the lesions appear concomitant with the loss of smell and taste. Multiple reports show evidences of necrotic/ulcerative gingiva, oral blisters and hypergrowth of opportunistic oral pathogens. SARS-CoV-2 exhibits tropism for endothelial cells and Covid-19-mediated endotheliitis can not only promote inflammation in oral tissues but can also facilitate virus spread. In addition, elevated levels of proinflammatory mediators in patients with Covid-19 and oral infectious disease can impair tissue homeostasis and cause delayed disease resolution. This suggests potential crosstalk of immune-mediated pathways underlying pathogenesis. Interestingly, few reports suggest recurrent herpetic lesions and higher bacterial growth in Covid-19 subjects, indicating SARS-CoV-2 and oral virus/bacteria interaction. Larger cohort studies comparing SARS-CoV-2 negative and positive subjects will reveal oral manifestation of the virus on oral health and its role in exacerbating oral infection.

Research Note: Rapid detection of avian infectious laryngotracheitis virus with real-time fluorescence-based recombinase-aided amplification.

In this study, specific primers and fluorescent probes were designed to target the thymidine kinase (TK) gene sequence of avian infectious laryngotracheitis virus (ILTV). Through specificity and sensitivity tests, a real-time fluorescence-based recombinase-aided amplification (RF-RAA) method for detecting ILTV was established. The results showed that the method was specific and could be used to accurately detect ILTV, and there was no cross-reaction with Newcastle disease virus (NDV), avian influenza virus (AIV), or infectious bronchitis virus (IBV). Real-time fluorescence-based recombinase-aided amplification had high sensitivity, and the lowest detectable limit (LDL) for ILTV could reach 10 copies/µL, 1,000 times more sensitive than conventional PCR (104 copies/µL), to rival that of real-time fluorescence-based quantitative PCR (RFQ-PCR) (10 copies/µL). This method and RFQ-PCR were used to detect 96 samples of chicken throat swabs with ILT initially diagnosed in clinic from the north of China, and the coincidence rate of the 2 methods was 100%. The RF-RAA reaction required only 20-30 minutes to completing, and its sensitivity was much higher than that of conventional PCR. Real-time fluorescence-based recombinase-aided amplification is similar to RFQ-PCR and has the advantages of specificity, sensitivity, and high efficiency, so it is suitable for early clinical detection and epidemiological investigation of ILTV.