Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections

Antiviral peptides inhibiting the main protease of SARS-CoV-2 investigated by computational screening and in vitro protease assay

The main protease (Mpro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays an important role in viral replication and transcription and received great attention as a vital target for drug/peptide development. Therapeutic agents such as small-molecule drugs or peptides that interact with the Cys-His present in the catalytic site of Mpro are an efficient way to inhibit the protease. Although several emergency-approved vaccines showed good efficacy and drastically dropped the infection rate, evolving variants are still infecting and killing millions of people globally. While a small-molecule drug (Paxlovid) received emergency approval, small-molecule drugs have low target specificity and higher toxicity. Besides small-molecule drugs, peptide therapeutics are thus gaining increasing popularity as they are easy to synthesize and highly selective and have limited side effects. In this study, we investigated the therapeutic value of 67 peptides targeting Mpro using molecular docking. Subsequently, molecular dynamics (MD) simulations were implemented on eight protein-peptide complexes to obtain molecular-level information on the interaction between these peptides and the Mpro active site, which revealed that temporin L, indolicidin, and lymphocytic choriomeningitis virus (LCMV) GP1 are the best candidates in terms of stability, interaction, and structural compactness. These peptides were synthesized using the solid-phase peptide synthesis protocol, purified by reversed-phase high-performance liquid chromatography (RP-HPLC), and authenticated by mass spectrometry (MS). The in vitro fluorometric Mpro activity assay was used to validate the computational results, where temporin L and indolicidin were observed to be very active against SARS-CoV-2 Mpro with IC50 values of 38.80 and 87.23 μM, respectively. A liquid chromatography-MS (LC-MS) assay was developed, and the IC50 value of temporin L was measured at 23.8 μM. The solution-state nuclear magnetic resonance (NMR) structure of temporin L was determined in the absence of sodium dodecyl sulfate (SDS) micelles and was compared to previous temporin structures. This combined investigation provides critical insights and assists us to further develop peptide inhibitors of SARS-CoV-2 Mpro through structural guided investigation.

Temperature and oxygen saturation in skilled nursing facility residents positive for SARS-CoV-2 prior to symptom onset

BACKGROUND

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) spreads rapidly amongst residents of skilled nursing facilities (SNFs). The rapid transmission dynamics and high morbidity and mortality that occur in SNFs emphasize the need for early detection of cases. We hypothesized that residents of SNFs infected with SARS-CoV-2 would demonstrate an acute change in either temperature or oxygen saturation (SpO₂ ) prior to symptom onset. The Minnesota Department of Health (MDH) conducted a retrospective analysis of both temperature and SpO₂ at two separate SNFs to assess the utility of these quantitative markers to identify SARS-CoV-2 infection prior to the development of symptoms.

METHODS

A retrospective analysis was conducted of 165 individuals positive for SARS-CoV-2 who were residents of SNFs that experienced coronavirus disease 2019 (COVID-19) outbreaks during April-June 2020 in a metropolitan area of Minnesota. Age, sex, symptomology, temperature and SpO₂ values, date of symptom onset, and date of positive SARS-CoV-2 test were analyzed. Temperature and SpO₂ values for the period 14 days before and after the date of initial positive test were included. Descriptive analyses evaluated changes in temperature and SpO₂ , defined as either exceeding a set threshold or demonstrating an acute change between consecutive measurements.

RESULTS

Two (1%) residents had a temperature value ≥100°F, and 30 (18%) had at least one value ≥99°F within 14 days before symptom development. One hundred and sixteen residents (70%) had at least one SpO₂ value ≤94%, while 131 (80%) had an acute decrease in SpO₂ of ≥3% between consecutive values in the 14 days prior to symptom onset.

CONCLUSIONS

Our results suggest that acute change in SpO₂ might be useful in the identification of SARS-CoV-2 infection prior to the development of symptoms among residents living in SNFs. Facilities may consider adding SpO₂ to daily temperature and symptom screening checklists to improve early detection of residents of SNFs infected with SARS-CoV-2.

Analysis of IgG, IgA and IgM antibodies against SARS-CoV-2 spike protein S1 in convalescent and vaccinated patients with the Pfizer-BioNTech and CanSinoBio vaccines

The SARS‐CoV‐2 virus was detected for the first time in December 2019 in Wuhan, China. Currently, this virus has spread around the world, and new variants have emerged. This new pandemic virus provoked the rapid development of diagnostic tools, therapies and vaccines to control this new disease called COVID‐19. Antibody detection by ELISA has been broadly used to recognize the number of persons infected with this virus or to evaluate the response of vaccinated individuals. As the pandemic spread, new questions arose, such as the prevalence of antibodies after natural infection and the response induced by the different vaccines. In Mexico, as in other countries, mRNA and viral‐vectored vaccines have been widely used among the population. In this work, we developed an indirect ELISA test to evaluate S1 antibodies in convalescent and vaccinated individuals. By using this test, we showed that IgG antibodies against the S1 protein of SARS‐CoV‐2 were detected up to 42 weeks after the onset of the symptoms, in contrast to IgA and IgM, which decreased 14 weeks after the onset of symptoms. The evaluation of the antibody response in individuals vaccinated with Pfizer‐BioNTech and CanSinoBio vaccines showed no differences 2 weeks after vaccination. However, after completing the two doses of Pfizer‐BioNTech and the one dose of CanSinoBio, a significantly higher response of IgG antibodies was observed in persons vaccinated with Pfizer‐BioNTech than in those vaccinated with CanSinoBio. In conclusion, these results confirm that after natural infection with SARS‐CoV‐2, it is possible to detect antibodies for up to 10 months. Additionally, our results showed that one dose of the CanSinoBio vaccine induces a lower response of IgG antibodies than that induced by the complete scheme of the Pfizer‐BioNTech vaccine.

Persistence of infectious SARS-CoV-2 particles for up to 37 days in patients with mild COVID-19

BACKGROUND

People suffering from COVID-19 are typically considered non-infectious 14 days after diagnosis if symptoms have disappeared for at least 48 h. We describe three patients who independently acquired their infection. These three patients experienced mild COVID-19 and completely recovered symptomatically within 10 days, but remained PCR-positive in deep pharyngeal samples for at least 38 days. We attempted to isolate virus from pharyngeal swabs to investigate whether these patients still carried infectious virus.

METHODS

Infectious virus was amplified in Vero E6 cells and characterized by electron microscopy and WGS. The immune response was investigated by ELISA and peptide arrays.

RESULTS

In all three cases, infectious and replication-competent virus was isolated and amplified in Vero E6 cells. Virus replication was detected by RT-PCR and immunofluorescence microscopy. Electron microscopy confirmed the formation of intact SARS-CoV-2 particles. For a more detailed analysis, all three isolates were characterized by whole-genome sequencing (WGS). The sequence data revealed that the isolates belonged to the 20A or 20C clade, and two mutations in ORF8 were identified among other mutations that could be relevant for establishing a long-term infection. Characterization of the humoral immune response in comparison to patients that had fully recovered from mild COVID-19 revealed a lack of antibodies binding to sequential epitopes of the receptor-binding domain (RBD) for the long-term infected patients.

CONCLUSION

Thus, a small portion of COVID-19 patients displays long-term infectivity and termination of quarantine periods after 14 days, without PCR-based testing, should be reconsidered critically.

AIDS and COVID: A tale of two pandemics and the role of statisticians

The world has experienced three global pandemics over the last half-century: HIV/AIDS, H1N1, and COVID-19. HIV/AIDS and COVID-19 are still with us and have wrought extensive havoc worldwide. There are many differences between these two infections and their global impacts, but one thing they have in common is the mobilization of scientific resources to both understand the infection and develop ways to combat it. As was the case with HIV, statisticians have been in the forefront of scientists working to understand transmission dynamics and the natural history of infection, determine prognostic factors for severe disease, and develop optimal study designs to assess therapeutics and vaccines.