Anti-Spike IgG antibodies as correlates of protection against SARS-CoV-2 infection in the pre-Omicron and Omicron era.

Anti-Spike IgG antibodies against SARS-CoV-2, which are elicited by vaccination and infection, are correlates of protection against infection with pre-Omicron variants. Whether this association can be generalized to infections with Omicron variants is unclear. We conducted a retrospective cohort study with 8457 blood donors in Tyrol, Austria, analyzing 15,340 anti-Spike IgG antibody measurements from March 2021 to December 2022 assessed by Abbott SARS-CoV-2 IgG II chemiluminescent microparticle immunoassay. Using a Bayesian joint model, we estimated antibody trajectories and adjusted hazard ratios for incident SARS-CoV-2 infection ascertained by self-report or seroconversion of anti-Nucleocapsid antibodies. At the time of their earliest available anti-Spike IgG antibody measurement (median November 23, 2021), participants had a median age of 46.0 years (IQR 32.8-55.2), with 45.3% being female, 41.3% having a prior SARS-CoV-2 infection, and 75.5% having received at least one dose of a COVID-19 vaccine. Among 6159 participants with endpoint data, 3700 incident SARS-CoV-2 infections with predominantly Omicron sublineages were recorded over a median of 8.8 months (IQR 5.7-12.4). The age- and sex-adjusted hazard ratio for SARS-CoV-2 associated with having twice the anti-Spike IgG antibody titer was 0.875 (95% credible interval 0.868-0.881) overall, 0.842 (0.827-0.856) during 2021, and 0.884 (0.877-0.891) during 2022 (all p < 0.001). The associations were similar in females and males (Pinteraction = 0.673) and across age (Pinteraction = 0.590). Higher anti-Spike IgG antibody titers were associated with reduced risk of incident SARS-CoV-2 infection across the entire observation period. While the magnitude of association was slightly weakened in the Omicron era, anti-Spike IgG antibody continues to be a suitable correlate of protection against newer SARS-CoV-2 variants.

Immunoinformatics and MD-simulation data suggest that Omicron spike epitopes are more interacting to IgG via better MHC recognition than Delta variant.

BACKGROUND: Recently, in Nov 2021, in South Africa, the SARS CoV-2 variant Omicron was found to be highly infectious and transmissible but with the least fatality. It occupies the nasopharynx-oropharynx and easily spreads. The epidemiological data/reports suggest that several vaccines failed to neutralize Omicron. It has a large number of spike mutations and the RNA/protein vaccines were developed from its predecessors that may justify its escape in most neutralization reactions. Its lower immuno-suppression/cytokine-storming/inflammatory-response effects need exploration. OBJECTIVES: In the current study, we attempted to delineate the comparative interaction of different variants' spikes with multiple recognition sites on IgG and HLA-typing of MHC class and I and II. METHODS: All SARS-CoV-2 spike-proteins/human-IgG/MHC-I & II were obtained from the NCBI/ PDB/GISAID database. Initial 3D-structures of the unavailable proteins were constructed by Homology-Modeling (Swissmodel-Expasy) and optimized (PROCHECK). Molecular-docking of spike-IgG/spike- I & MHC-II was performed (HADDOCK2.4/HawkDock) with active-residue screening (CPORT). Antigenicity of epitopes was determined (Vaxigen v2.0-server) and the epitope-model prepared (PEP-FOLD3-server). The binding-affinity/biological-interfaces/visualize were performed (PRODIGY-PyMOL2). We also examined the genesis of feasible transition pathways of functional docked complexes (iMODs) of MHC with different epitopes and antibodies of IgG with different variants. Further, Molecular-Dynamic-Simulation was performed by GROMACS 2023.1 software package. The MD-simulation was run with 100 ns (300 k-heating/1-atm pressure). RESULTS: Surface-area with interactomes, H-bonding and polar/non-polar bonding were the highest in Omicron spike-IgG interaction. Unlike other variants, both the L and H chains of at least three different recognition sites of IgG interact with the N-terminal and C-terminal RBD of the S1-portion and partially bind to S2. In other cases, binding was observed in either NTD or CTD with a lesser number of bonding-interactomes, especially in Delta spike-Ab interaction. In the case of MHC class-I & II, the highest binding affinity/surface was noticed by Omicron and least by the Delta variant. The MD simulation data of lower RMSD values of the Delta and Omicron variants indicate improved structural stability and less departure from the initial conformation. Better binding to the IgG and MHC molecules explains Omicron's little ability in immune invasion.

Critical assessment of the impact of vaccine-type and immunity on the burden of COVID-19.

The COVID-19 pandemic continues to have a devastating impact on health systems and economies across the globe. Implementing public health measures in tandem with effective vaccination strategies have been instrumental in curtailing the burden of the pandemic. With the three vaccines authorized for use in the U.S. having varying efficacies and waning effects against major COVID-19 strains, understanding the impact of these vaccines on COVID-19 incidence and fatalities is critical. Here, we formulate and use mathematical models to assess the impact of vaccine type, vaccination and booster uptake, and waning of natural and vaccine-induced immunity on the incidence and fatalities of COVID-19 and to predict future trends of the disease in the U.S. when existing control measures are reinforced or relaxed. The results show a 5-fold reduction in the control reproduction number during the initial vaccination period and a 1.8-fold (2-fold) reduction in the control reproduction number during the initial first booster (second booster) uptake period, compared to the respective previous periods. Due to waning of vaccine-induced immunity, vaccinating up to 96% of the U.S. population might be required to attain herd immunity, if booster uptake is low. Additionally, vaccinating and boosting more people from the onset of vaccination and booster uptake, especially with the Pfizer-BioNTech and Moderna vaccines (which confer superior protection than the Johnson & Johnson vaccine) would have led to a significant reduction in COVID-19 cases and deaths in the U.S. Furthermore, adopting natural immunity-boosting measures is important in fighting COVID-19 and transmission rate reduction measures such as mask-use are critical in combating COVID-19. The emergence of a more transmissible COVID-19 variant, or early relaxation of existing control measures can lead to a more devastating wave, especially if transmission rate reduction measures and vaccination are relaxed simultaneously, while chances of containing the pandemic are enhanced if both vaccination and transmission rate reduction measures are reinforced simultaneously. We conclude that maintaining or improving existing control measures, and boosting with mRNA vaccines are critical in curtailing the burden of the pandemic in the U.S.

Cross-variant proof predictive vaccine design based on SARS-CoV-2 spike protein using immunoinformatics approach.

Background: Coronavirus Disease (COVID-19) is caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The SARS-CoV-2 virus is evolving continuously. The omicron variant of SARS-CoV-2 has the highest mutation in its spike protein, thus making the presently available vaccine ineffective or reducing its efficiency. Furthermore, the majority of the vaccines are constructed using a spike protein sequence from wild-type SARS-CoV-2. This raises the possibility of the virus evolving to the point where the vaccine's effectiveness is completely lost, even after booster doses. The study aims to develop a predictive vaccine as well as the epitopes for the updating of the vaccine sequences of currently available vaccines. In this study, following the immunoinformatics approach, predictive vaccine construction was done with the help of epitopes present on spike proteins of wild-type, delta, and omicron variants that encompass the majority of variants and possible new variants that arise from the combination of circulating variants. Results: The vaccine that was constructed was stable and immunogenic. The vaccine was constructed with the help of 18 B-cell epitopes, 5 MHC class I epitopes, and 6 MHC class II epitopes. The epitope conservancy analysis suggests that the vaccine will work for the previously known variant of concern. The vaccine bound to TLR4, TLR2, B-cell receptor chains A and B, and ACE2 receptors with a z score of - 1.4, - 1.7, - 1.4, - 1.7, and - 1.4, respectively, with a cluster size of 121 highest for the ACE2 receptor and 46 lowest for B-cell receptor chain A. The C-ImmSim simulation results indicate that the vaccine is generating both humoral and cell-mediated responses at a sufficient level throughout the month upon injection of the vaccine as an antigen. Conclusion: The study's findings indicate that the vaccine was both stable and immunogenic, providing a sufficient level of immunity. Following experimental validation, the vaccine can be used, and the epitopes can be employed for therapeutic purposes such as antibody synthesis. Supplementary Information: The online version contains supplementary material available at 10.1186/s43088-023-00341-4.

SARS-CoV-2 infection among patients with autoimmune rheumatic diseases; comparison between the Delta and Omicron waves in Israel.

OBJECTIVE: The Omicron variant of the coronavirus SARS-CoV-2 (COVID-19) had milder clinical impacts than prior variants. This study aimed to describe the impact of COVID-19 on Autoimmune Rheumatic Disease (ARD) patients during the Delta and Omicron variants waves. METHODS: We used data from Clalit Health Services (CHS), the largest health service in Israel. ARD patients diagnosed with COVID-19 between July 1, 2021, to December 1, 2021, were included in the Delta group. Patients diagnosed between December 2, 2021, to March 31, 2022, were included in the Omicron group based on the predominance of COVID-19 in Israel. The study outcomes were COVID-19-related hospitalization or death. RESULTS: The final study cohort included 8443 actively treated ARD patients diagnosed with COVID-19. 1204 patients were positive during the predefined Delta variant period, and 7249 were positive during the predefined Omicron variant period). Compared to the Delta group, the Omicron group showed a lower rate of COVID-19-related hospitalization (3.9% vs. 1.3% for the Delta Vs. Omicron accordingly, p<0.001) and COVID-19-related death (3.2% vs. 1.1% for the Delta Vs. Omicron accordingly, p<0.001). After applying multivariable regression models, the Omicron group showed a lower risk for COVID-19-related hospitalization (Relative risk 0.4, 95% CI 0.27-0.59) and COVID-19-related mortality (RR 0.48, 95% CI 0.31-0.75). CONCLUSION: ARD patients infected with the COVID-19 Omicron variant had a lower risk of developing COVID-19-related adverse outcomes compared to the Delta variant.

Molecular screening of SARS-CoV-2 in dogs and cats from households with infected owners diagnosed with COVID-19 during Delta and Omicron variant waves in Iran.

OBJECTIVE: The emergence of SARS-CoV-2 infection in dogs and cats in different countries worldwide raises concerns that pets are at a higher risk for spreading or transmitting of SARS-CoV-2 to humans and other pets and increased the research works about the zoonotic aspects and natural routes of infection in companion animals. The current study aimed to detect the SARS-CoV-2 in household dogs and cats living with COVID-19 positive owners. METHODS: Deep oropharyngeal and rectal swabs were collected from 30 household pets (20 cats and 10 dogs) living with COVID-19 positive owners from April 2021 to 2022 in Kerman, Iran. All dogs' and cats' samples were tested by real-time reverse transcription polymerase chain reaction for detection of SARS-CoV-2. RESULTS: Two household cats out of 20 examined (10%) were positive for SARS-CoV-2, whereas none of the examined dogs were positive for SARS-CoV-2. The two cats positive for SARS-CoV-2 were symptomatic and suffered from severe anorexia with maximum contact with their infected owners. CONCLUSION: This study reported the presence of SARS-CoV-2 in household cats in close contact with COVID-19 positive owners during the circulation of new SARS-CoV-2 variants (Delta and Omicron) in Iran and suggested that the transmission may have occurred from owners to their cats. Therefore, infected owners should eagerly limit close contact with their pets during COVID-19 illness.

Differential Outcomes of Infection by Wild-Type SARS-CoV-2 and the B.1.617.2 and B.1.1.529 Variants of Concern in K18-hACE2 Transgenic Mice.

BACKGROUND: SARS-CoV-2 is a respiratory virus with neurological complications including the loss of smell and taste, headache, and confusion that can persist for months or longer. Severe neuronal cell damage has also been reported in some cases. The objective of this study was to compare the infectivity of the wild-type virus, Delta (B.1.617.2) and Omicron (B.1.1.529) variants in transgenic mice that express the human angiotensin-converting enzyme 2 (hACE2) receptor under the control of the keratin 18 promoter (K18) and characterize the progression of infection and inflammatory response in the lungs, brain, medulla oblongata, and olfactory bulbs of these animals. We hypothesized that wild type, Delta and Omicron differentially infect K18-hACE2 mice, thereby inducing distinct cellular responses. METHODS: K18-hACE2 female mice were intranasally infected with wild-type, Delta, or Omicron variants and euthanized either at 3 days post-infection (dpi) or at the humane endpoint. None of the animals infected with the Omicron variant reached the humane endpoint and were euthanized at day 8 dpi. Virological and immunological analyses were performed in the lungs, brains, medulla oblongata and olfactory bulbs isolated from infected mice. RESULTS: At 3 dpi, mice infected with wild type and Delta displayed significantly higher levels of viral RNA in the lungs than mice infected with Omicron, while in the brain, Delta and Omicron resulted in higher levels of viral RNA than with the wild type. Viral RNA was also detected in the medulla oblongata of mice infected by all these virus strains. At this time point, the mice infected with wild type and Delta displayed a marked upregulation of many inflammatory markers in the lungs. On the other hand, the upregulation of inflammatory markers was observed only in the brains of mice infected with Delta and Omicron. At the humane endpoint, we observed a significant increase in the levels of viral RNA in the lungs and brains of mice infected with wild type and Delta, which was accompanied by the elevated expression of many inflammatory markers. In contrast, mice which survived infection with the Omicron variant showed high levels of viral RNA and the upregulation of cytokine and chemokine expression only in the lungs at 8 dpi, suggesting that infection and inflammatory response by this variant is attenuated in the brain. Reduced RNA levels and the downregulation of inflammatory markers was also observed in the medulla oblongata and olfactory bulbs of mice infected with Omicron at 8 dpi as compared with mice infected with wild-type and Delta at the humane end point. Collectively, these data demonstrate that wild-type, Delta, and Omicron SARS-CoV-2 induce distinct levels of infection and inflammatory responses in K18-hACE2 mice. Notably, sustained brain infection accompanied by the upregulation of inflammatory markers is a critical outcome in mice infected with wild type and Delta but not Omicron.

Glycogen Synthase Kinase-3 Interaction Domain Enhances Phosphorylation of SARS-CoV-2 Nucleocapsid Protein.

A structural protein of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), nucleocapsid (N) protein is phosphorylated by glycogen synthase kinase (GSK)-3 on the serine/arginine (SR) rich motif located in disordered regions. Although phosphorylation by GSK-3ß constitutes a critical event for viral replication, the molecular mechanism underlying N phosphorylation is not well understood. In this study, we found the putative alpha-helix L/FxxxL/AxxRL motif known as the GSK-3 interacting domain (GID), found in many endogenous GSK-3ß binding proteins, such as Axins, FRATs, WWOX, and GSKIP. Indeed, N interacts with GSK-3ß similarly to Axin, and Leu to Glu substitution of the GID abolished the interaction, with loss of N phosphorylation. The N phosphorylation is also required for its structural loading in a virus-like particle (VLP). Compared to other coronaviruses, N of Sarbecovirus lineage including bat RaTG13 harbors a CDK1-primed phosphorylation site and Gly-rich linker for enhanced phosphorylation by GSK-3ß. Furthermore, we found that the S202R mutant found in Delta and R203K/G204R mutant found in the Omicron variant allow increased abundance and hyper-phosphorylation of N. Our observations suggest that GID and mutations for increased phosphorylation in N may have contributed to the evolution of variants.

Molecular dynamic simulation suggests stronger interaction of Omicron-spike with ACE2 than wild but weaker than Delta SARS-CoV-2 can be blocked by engineered S1-RBD fraction.

The SARS-CoV-2 claimed millions of lives, globally. Occurring from Wuhan (wild type) in December, 2019, it constantly mutated to Omicron (B.1.1.529), the predecessor to Delta. Omicron having ~ 32 spike mutations has variable infectivity-multiplicity-immuno-invasive properties. Understanding of its mutational effect on ACE2-binding/disease severity and developing preventive/therapeutic strategies are important. The binding affinities of Wuhan/Delta/Omicron spikes (PDB/GISAID/SWISS-MODEL) were docked (HADDOCK2.4) with ACE2 and compared by competitive-docking (PRODIGY). The protein structural stability was verified by kinetic-data/Ramachandran-plot (Zlab/UMassMedBioinfo). After several trials, a 59 amino acid (453ARG-510VAL) peptide-cut (Expasy-server) of the wild-type spike RBD with some desired mutants (THR500SER/THR500GLY/THR500ALA/THR500CYS) was blindly/competitively docked (PyMOL-V2.2.2) to block the Omicron-ACE2 binding. We examined molecular dynamic simulation (iMOD-server, with 9000 cycles/300 k-heating/1 atm pressure for system equilibration for 50 ns-run) of ACE2 and two CUTs with different SARS-CoV-2 variants. The binding-affinity of Omicron-ACE2 is slightly higher than the rest two in competitive docking setup. During individual (1:1) docking, Omicron showed little higher than wild type but much weaker binding affinity than Delta. Competitive docking suggests ten H-bonding (1.3-2.4 Å) with highly favorable energy values/Van-der-Walls-force/Haddock score for more stable-binding of Omicron-RBD with ACE2. Blind docking of different CUTs (wild/mutants) and Omicron to ACE2 completely rejected the Omicron-RBD from ACE2-target. The best blocking/binding affinity of -16.4 and -13 kcal/mole were observed in the case of THR500SER and THR500GLY, respectively, with multiple H-bonding 1.9-2.2 Å. These are supported by the MD-simulation results. So, the spike binding affinities were Delta > Omicron > wild in 1:1 docking with ACE2. Considering the wild type is non-existing nowadays, Omicron showed less ACE2 binding properties. The 59 cut of spike-RBD and its mutant THR500SER/THR500GLY may be further screened as universal blockers of this virus. Supplementary Information: The online version contains supplementary material available at 10.1007/s11224-022-02022-x.

A Newly Engineered A549 Cell Line Expressing ACE2 and TMPRSS2 Is Highly Permissive to SARS-CoV-2, Including the Delta and Omicron Variants.

New variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continue to emerge, causing surges, breakthrough infections, and devastating losses-underscoring the importance of identifying SARS-CoV-2 antivirals. A simple, accessible human cell culture model permissive to SARS-CoV-2 variants is critical for identifying and assessing antivirals in a high-throughput manner. Although human alveolar A549 cells are a valuable model for studying respiratory virus infections, they lack two essential host factors for SARS-CoV-2 infection: angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2). SARS-CoV-2 uses the ACE2 receptor for viral entry and TMPRSS2 to prime the SARS-CoV-2 spike protein, both of which are negligibly expressed in A549 cells. Here, we report the generation of a suitable human cell line for SARS-CoV-2 studies by transducing human ACE2 and TMPRSS2 into A549 cells. We show that subclones highly expressing ACE2 and TMPRSS2 ("ACE2plus" and the subclone "ACE2plusC3") are susceptible to infection with SARS-CoV-2, including the delta and omicron variants. These subclones express more ACE2 and TMPRSS2 transcripts than existing commercial A549 cells engineered to express ACE2 and TMPRSS2. Additionally, the antiviral drugs EIDD-1931, remdesivir, nirmatrelvir, and nelfinavir strongly inhibit SARS-CoV-2 variants in our infection model. Our data show that ACE2plusC3 cells are highly permissive to SARS-CoV-2 infection and can be used to identify anti-SARS-CoV-2 drugs.

Evidence of co-infections during Delta and Omicron SARS-CoV-2 variants co-circulation through prospective screening and sequencing.

OBJECTIVES: To describe Delta/Omicron SARS-CoV-2 variants co-infection detection and confirmation during the fifth wave of COVID-19 pandemics in France in 7 immunocompetent and epidemiologically unrelated patients. METHODS: Since December 2021, the surveillance of Delta/Omicron SARS-CoV-2 variants of concern (VOC) circulation was performed through prospective screening of positive-samples using single nucleotide polymorphism (SNP) PCR assays targeting SARS-CoV-2 S-gene mutations K417N (Omicron specific) and L452R (Delta specific). Samples showing unexpected mutational profiles were further submitted to whole genome sequencing (WGS) using three different primer sets. RESULTS: Between weeks 49-2021 and 02-2022, SARS-CoV-2 genome was detected in 3831 respiratory samples, of which 3237 (84.5%) were screened for VOC specific SNPs. Unexpected mutation profiles suggesting a dual Delta/Omicron population were observed in 7 nasopharyngeal samples (0.2%). These co-infections were confirmed by WGS. For 2 patients, the sequence analyses of longitudinal samples collected 7 to 11 days apart showed that Delta or Omicron can outcompete the other variant during dual infection. Additionally, for one of these samples, a recombination event between Delta and Omicron was detected. CONCLUSIONS: This work demonstrates that SARS-CoV-2 Delta/Omicron co-infections are not rare in high virus co-circulation periods. Moreover, co-infections can further lead to genetic recombination which may generate new chimeric variants with unpredictable epidemic or pathogenic properties that could represent a serious health threat.