In-silico approaches for identification of compounds inhibiting SARS-CoV-2 3CL protease.

The world has witnessed of many pandemic waves of SARS-CoV-2. However, the incidence of SARS-CoV-2 infection has now declined but the novel variant and responsible cases has been observed globally. Most of the world population has received the vaccinations, but the immune response against COVID-19 is not long-lasting, which may cause new outbreaks. A highly efficient pharmaceutical molecule is desperately needed in these circumstances. In the present study, a potent natural compound that could inhibit the 3CL protease protein of SARS-CoV-2 was found with computationally intensive search. This research approach is based on physics-based principles and a machine-learning approach. Deep learning design was applied to the library of natural compounds to rank the potential candidates. This procedure screened 32,484 compounds, and the top five hits based on estimated pIC50 were selected for molecular docking and modeling. This work identified two hit compounds, CMP4 and CMP2, which exhibited strong interaction with the 3CL protease using molecular docking and simulation. These two compounds demonstrated potential interaction with the catalytic residues His41 and Cys154 of the 3CL protease. Their calculated binding free energies to MMGBSA were compared to those of the native 3CL protease inhibitor. Using steered molecular dynamics, the dissociation strength of these complexes was sequentially determined. In conclusion, CMP4 demonstrated strong comparative performance with native inhibitors and was identified as a promising hit candidate. This compound can be applied in-vitro experiment for the validation of its inhibitory activity. Additionally, these methods can be used to identify new binding sites on the enzyme and to design new compounds that target these sites.

Students' Preferences and Perceptions Regarding Online versus Offline Teaching and Learning Post-COVID-19 Lockdown

The COVID-19 pandemic at its peak compelled students to stay home and adapt to the distance learning system. The world has gone through phases of fear and respite in the recent years. There have been a number of studies related to student learning via online teaching during the pandemic. Now, as the vaccination coverage picks up and the pandemic appears to have achieved a plateau, it is time to take a view of students' perceptions of online learning and its effectiveness in skill development during the COVID-19 pandemic. This study assesses the students' preferences and perceptions regarding offline and online learning post-COVID-19 lockdown and with the resumption of offline classes. A cross-sectional study was conducted at King Khalid University, Aseer region, from the period of 1 January 2022 to 30 January 2022. A convenience sampling technique was utilized to collect data from female students. Data analysis was conducted by using SPSS version 22.0. A total of 480 students participated in the study, their mean age was 19.79 ±1.48. More than half of the students (64%) still fear getting COVID-19 as they continue with the in-person or offline classes despite having completed their doses of vaccination. Almost half of the students have difficulty in waking up after the recommencement of offline classes. The majority (77%) felt tired after starting offline classes, and 63% felt unhappy after starting offline classes again. The majority of students believe that, with offline classes, they have difficulty in time management and concentration. The majority of students believed that, with online classes, they are more comfortable in gaining knowledge and learning, more alert, more satisfied, and gain higher scores in exams. The majority of students preferred the online mode of learning, with about 72% of students wishing to continue online learning in the future. This research underlines the influence of fear of getting COVID-19 after the commencement of face-to-face learning amongst the students. Students were more inclined to continue with online classes because of fear of getting COVID-19, despite having full doses of the vaccination in Saudi Arabia. There is a need for a better understanding of students' motivations and coping mechanisms during the pandemic.

Highly Thermotolerant SARS-CoV-2 Vaccine Elicits Neutralising Antibodies against Delta and Omicron in Mice.

As existing vaccines fail to completely prevent COVID-19 infections or community transmission, there is an unmet need for vaccines that can better combat SARS-CoV-2 variants of concern (VOC). We previously developed highly thermo-tolerant monomeric and trimeric receptor-binding domain derivatives that can withstand 100 °C for 90 min and 37 °C for four weeks and help eliminate cold-chain requirements. We show that mice immunised with these vaccine formulations elicit high titres of antibodies that neutralise SARS-CoV-2 variants VIC31 (with Spike: D614G mutation), Delta and Omicron (BA.1.1) VOC. Compared to VIC31, there was an average 14.4-fold reduction in neutralisation against BA.1.1 for the three monomeric antigen-adjuvant combinations and a 16.5-fold reduction for the three trimeric antigen-adjuvant combinations; the corresponding values against Delta were 2.5 and 3.0. Our findings suggest that monomeric formulations are suitable for upcoming Phase I human clinical trials and that there is potential for increasing the efficacy with vaccine matching to improve the responses against emerging variants. These findings are consistent with in silico modelling and AlphaFold predictions, which show that, while oligomeric presentation can be generally beneficial, it can make important epitopes inaccessible and also carries the risk of eliciting unwanted antibodies against the oligomerisation domain.

A Stabilized, Monomeric, Receptor Binding Domain Elicits High-Titer Neutralizing Antibodies Against All SARS-CoV-2 Variants of Concern.

Saturation suppressor mutagenesis was used to generate thermostable mutants of the SARS-CoV-2 spike receptor-binding domain (RBD). A triple mutant with an increase in thermal melting temperature of ~7°C with respect to the wild-type B.1 RBD and was expressed in high yield in both mammalian cells and the microbial host, Pichia pastoris, was downselected for immunogenicity studies. An additional derivative with three additional mutations from the B.1.351 (beta) isolate was also introduced into this background. Lyophilized proteins were resistant to high-temperature exposure and could be stored for over a month at 37°C. In mice and hamsters, squalene-in-water emulsion (SWE) adjuvanted formulations of the B.1-stabilized RBD were considerably more immunogenic than RBD lacking the stabilizing mutations and elicited antibodies that neutralized all four current variants of concern with similar neutralization titers. However, sera from mice immunized with the stabilized B.1.351 derivative showed significantly decreased neutralization titers exclusively against the B.1.617.2 (delta) VOC. A cocktail comprising stabilized B.1 and B.1.351 RBDs elicited antibodies with qualitatively improved neutralization titers and breadth relative to those immunized solely with either immunogen. Immunized hamsters were protected from high-dose viral challenge. Such vaccine formulations can be rapidly and cheaply produced, lack extraneous tags or additional components, and can be stored at room temperature. They are a useful modality to combat COVID-19, especially in remote and low-resource settings.

Immunogenicity and Protective Efficacy of a Highly Thermotolerant, Trimeric SARS-CoV-2 Receptor Binding Domain Derivative.

The receptor binding domain (RBD) of SARS-CoV-2 is the primary target of neutralizing antibodies. We designed a trimeric, highly thermotolerant glycan engineered RBD by fusion to a heterologous, poorly immunogenic disulfide linked trimerization domain derived from cartilage matrix protein. The protein expressed at a yield of ∼80-100 mg/L in transiently transfected Expi293 cells, as well as CHO and HEK293 stable cell lines and formed homogeneous disulfide-linked trimers. When lyophilized, these possessed remarkable functional stability to transient thermal stress of up to 100 °C and were stable to long-term storage of over 4 weeks at 37 °C unlike an alternative RBD-trimer with a different trimerization domain. Two intramuscular immunizations with a human-compatible SWE adjuvanted formulation elicited antibodies with pseudoviral neutralizing titers in guinea pigs and mice that were 25-250 fold higher than corresponding values in human convalescent sera. Against the beta (B.1.351) variant of concern (VOC), pseudoviral neutralization titers for RBD trimer were ∼3-fold lower than against wildtype B.1 virus. RBD was also displayed on a designed ferritin-like Msdps2 nanoparticle. This showed decreased yield and immunogenicity relative to trimeric RBD. Replicative virus neutralization assays using mouse sera demonstrated that antibodies induced by the trimers neutralized all four VOC to date, namely B.1.1.7, B.1.351, P.1, and B.1.617.2 without significant differences. Trimeric RBD immunized hamsters were protected from viral challenge. The excellent immunogenicity, thermotolerance, and high yield of these immunogens suggest that they are a promising modality to combat COVID-19, including all SARS-CoV-2 VOC to date.

Design of a highly thermotolerant, immunogenic SARS-CoV-2 spike fragment.

Virtually all SARS-CoV-2 vaccines currently in clinical testing are stored in a refrigerated or frozen state prior to use. This is a major impediment to deployment in resource-poor settings. Furthermore, several of them use viral vectors or mRNA. In contrast to protein subunit vaccines, there is limited manufacturing expertise for these nucleic-acid-based modalities, especially in the developing world. Neutralizing antibodies, the clearest known correlate of protection against SARS-CoV-2, are primarily directed against the receptor-binding domain (RBD) of the viral spike protein, suggesting that a suitable RBD construct might serve as a more accessible vaccine ingredient. We describe a monomeric, glycan-engineered RBD protein fragment that is expressed at a purified yield of 214 mg/l in unoptimized, mammalian cell culture and, in contrast to a stabilized spike ectodomain, is tolerant of exposure to temperatures as high as 100 °C when lyophilized, up to 70 °C in solution and stable for over 4 weeks at 37 °C. In prime:boost guinea pig immunizations, when formulated with the MF59-like adjuvant AddaVax, the RBD derivative elicited neutralizing antibodies with an endpoint geometric mean titer of ∼415 against replicative virus, comparing favorably with several vaccine formulations currently in the clinic. These features of high yield, extreme thermotolerance, and satisfactory immunogenicity suggest that such RBD subunit vaccine formulations hold great promise to combat COVID-19.