Primary exposure to SARS-CoV-2 protects against reinfection in rhesus macaques

Natural and Experimental SARS-CoV-2 Infection in Domestic and Wild Animals

SARS-CoV-2 is the etiological agent responsible for the ongoing COVID-19 pandemic, which continues to spread with devastating effects on global health and socioeconomics. The susceptibility of domestic and wild animal species to infection is a critical facet of SARS-CoV-2 ecology, since reverse zoonotic spillover events resulting in SARS-CoV-2 outbreaks in animal populations could result in the establishment of new virus reservoirs. Adaptive mutations in the virus to new animal species could also complicate ongoing mitigation strategies to combat SARS-CoV-2. In addition, animal species susceptible to SARS-CoV-2 infection are essential as standardized preclinical models for the development and efficacy testing of vaccines and therapeutics. In this review, we summarize the current findings regarding the susceptibility of different domestic and wild animal species to experimental SARS-CoV-2 infection and provide detailed descriptions of the clinical disease and transmissibility in these animals. In addition, we outline the documented natural infections in animals that have occurred at the human-animal interface. A comprehensive understanding of animal susceptibility to SARS-CoV-2 is crucial to inform public health, veterinary, and agricultural systems, and to guide environmental policies.

Overview of Nonhuman Primate Models of SARS-CoV-2 Infection

COVID-19, the disease caused by the SARS-CoV-2 betacoronavirus, was declared a pandemic by the World Health Organization on March 11, 2020. Since then, SARS-CoV-2 has triggered a devastating global health and economic emergency. In response, a broad range of preclinical animal models have been used to identify effective therapies and vaccines. Current animal models do not express the full spectrum of human COVID-19 disease and pathology, with most exhibiting mild to moderate disease without mortality. NHPs are physiologically, genetically, and immunologically more closely related to humans than other animal species; thus, they provide a relevant model for SARS-CoV-2 investigations. This overview summarizes NHP models of SARS-CoV-2 and their role in vaccine and therapeutic development.

Postinfectious Immunity After COVID-19 and Vaccination Against SARS-CoV-2

Early results suggest that SARS-CoV-2 vaccines are highly effective for the prevention of COVID-19. Unfortunately, until we can safely, rapidly, and affordably vaccinate enough people to achieve collective immunity, we cannot afford to disregard the benefits of naturally acquired immunity in those, whose prior documented infections have already run their course. As long as the vaccine manufacturing, supply, or administration are limited in capacity, vaccination of individuals with naturally acquired immunity at the expense of others without any immune protection is inherently inequitable, and violates the principle of justice in biomedical ethics. Any preventable disease acquired during the period of such unnecessary delay in vaccination should not be overlooked, as it may and will result in some additional morbidity, mortality, related hospitalizations, and expense. Low vaccine production capacity complicated by inefficiencies in vaccine administration suggests, that vaccinating preferentially those without any prior protection will result in fewer natural infections more rapidly.

Long-term monitoring of the development and extinction of IgA and IgG responses to SARS-CoV-2 infection

Despite the great interest of the scientific community in the behavior of the human body after contact with the new coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), long-term (more than 6 months) monitoring of the immunological status of patients with coronavirus disease 2019 (COVID-19) having varying severity degrees and of the people with a low SARS-CoV-2 viral load is practically absent. The aim of this study is a 9-month monitoring of SARS-CoV-2 infection immune response development and extinction using quantitative assessment of IgA and IgG levels in the blood of healthy donors living in the context of the coronavirus pandemic and of the patients who have undergone COVID-19. The project involved 180 volunteers, of whom 51 persons (28.33%) fell ill with COVID-19 during the observation period. All people who underwent COVID-19 developed a stable humoral immune response but their individual immune status had a number of features. Approximately 39.22% (20 of 51 people) of project participants diagnosed with COVID-19 showed an unusual change in plasma anti-SARS-CoV-2 IgA levels. Relatively high levels of IgA (ratio ~ 3) after recovery persisted for a long time (more than 6 months). In one-third (17 of 51 people) of patients with COVID-19, the IgA level exceeded the IgG level. IgA antibodies appeared earlier and showed a stronger and more robust response to the SARS-CoV-2 virus than IgG. Increased levels of anti-SARS-CoV-2 IgA (ratio from 0.8 to 2.36) throughout the observation period were recorded in 28 of 180 project participants (15.56%) of whom only one person fell ill with COVID-19.

COVID-19 Animal Models and Vaccines: Current Landscape and Future Prospects

The worldwide pandemic of coronavirus disease 2019 (COVID-19) has become an unprecedented challenge to global public health. With the intensification of the COVID-19 epidemic, the development of vaccines and therapeutic drugs against the etiological agent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is also widespread. To prove the effectiveness and safety of these preventive vaccines and therapeutic drugs, available animal models that faithfully recapitulate clinical hallmarks of COVID-19 are urgently needed. Currently, animal models including mice, golden hamsters, ferrets, nonhuman primates, and other susceptible animals have been involved in the study of COVID-19. Moreover, 117 vaccine candidates have entered clinical trials after the primary evaluation in animal models, of which inactivated vaccines, subunit vaccines, virus-vectored vaccines, and messenger ribonucleic acid (mRNA) vaccines are promising vaccine candidates. In this review, we summarize the landscape of animal models for COVID-19 vaccine evaluation and advanced vaccines with an efficacy range from about 50% to more than 95%. In addition, we point out future directions for COVID-19 animal models and vaccine development, aiming at providing valuable information and accelerating the breakthroughs confronting SARS-CoV-2.

Blood Analysis of Laboratory Macaca mulatta Used for Neuroscience Research: Investigation of Long-Term and Cumulative Effects of Implants, Fluid Control, and Laboratory Procedures

The nonhuman primate (NHP) constitutes an extraordinarily important model in neuroscience research for understanding the neuronal underpinnings of perceptual, motor, cognitive, and executive functions of the primate brain, and to study the physiological causes, effects, and potential treatments of brain disorders. Because of their cognitive capabilities, NHPs receive special attention in animal welfare regulations around the world, and their well-being is a benchmark for the evaluation, monitoring, and refinement of experimental procedures. As a consequence, many typical neuroscientific procedures are considered only mildly severe by animal welfare boards. There is, however, an ongoing debate about possible long-term and cumulative effects. Because of a lack of longitudinal data, it is unclear whether mildly severe procedures may cause more significant harm on the long-term, and to what extent they may impact animal well-being and healthiness over time. We here make use of a database of blood samples drawn over a period of 15 years from 39 rhesus monkeys (Macaca mulatta) to address the issue of long-term, cumulative effects of neuroscientific procedures. A careful analysis of indicative primate blood markers for chronic inflammation, hydration status, and stress levels, their comparison to baseline values from both the same animals and the literature, and evaluation of additional hematologic, physiological, and behavioral parameters did not provide support for the notion of long-term, cumulative effects on the monkeys’ healthiness and well-being. The results may serve the community as a reference for the severity assessment of neuroscientific experiments involving NHPs.

Longitudinal analysis of severe acute respiratory syndrome coronavirus 2 seroprevalence using multiple serology platforms

Current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serological tests are based on the full-length spike (S), the receptor-binding domain (RBD), or the nucleoprotein (NP) as substrates. Here, we used samples from healthcare workers (HCWs) to perform a longitudinal analysis of the antibody responses using a research-grade RBD and spike-based enzyme-linked immunosorbent assay (ELISA), a commercial RBD and spike-based ELISA, and a commercial NP-based chemiluminescent microparticle immunoassay. Seroprevalence ranged around 28% early during the pandemic and a good correlation was observed between RBD and spike-based ELISAs. Modest correlations were observed between NP and both RBD and spike-based assays. The antibody levels in HCWs declined over time; however, the overall seroprevalence measured by RBD and spike-based assays remained unchanged, while the seroprevalence of NP-reactive antibodies significantly declined. Moreover, RBD and spike-based assays effectively detected seroconversion in vaccinees. Overall, our results consolidate the strength of different serological assays to assess the magnitude and duration of antibodies to SARS-CoV-2.

Microfluidic Organs-on-a-Chip for Modeling Human Infectious Diseases

Infectious diseases present tremendous challenges to human progress and public health. The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the associated coronavirus disease 2019 (COVID-19) pandemic continue to pose an imminent threat to humanity. These infectious diseases highlight the importance of developing innovative strategies to study disease pathogenesis and protect human health. Although conventional in vitro cell culture and animal models are useful in facilitating the development of effective therapeutics for infectious diseases, models that can accurately reflect human physiology and human-relevant responses to pathogens are still lacking. Microfluidic organs-on-a-chip (organ chips) are engineered microfluidic cell culture devices lined with living cells, which can resemble organ-level physiology with high fidelity by rebuilding tissue-tissue interfaces, mechanical cues, fluidic flow, and the biochemical cellular microenvironment. They present a unique opportunity to bridge the gap between in vitro experimental models and in vivo human pathophysiology and are thus a promising platform for disease studies and drug testing. In this Account, we first introduce how recent progress in organ chips has enabled the recreation of complex pathophysiological features of human infections in vitro. Next, we describe the progress made by our group in adopting organ chips and other microphysiological systems for the study of infectious diseases, including SARS-CoV-2 viral infections and intrauterine bacterial infections. Respiratory symptoms dominate the clinical manifestations of many COVID-19 patients, even involving the systemic injury of many distinct organs, such as the lung, the gastrointestinal tract, and so forth. We thus particularly highlight our recent efforts to explore how lung-on-a-chip and intestine-on-a-chip might be useful in addressing the ongoing viral pandemic of COVID-19 caused by SARS-CoV-2. These organ chips offer a potential platform for studying virus-host interactions and human-relevant responses as well as accelerating the development of effective therapeutics against COVID-19. Finally, we discuss opportunities and challenges in the development of next-generation organ chips, which are urgently needed for developing effective and affordable therapies to combat infectious diseases. We hope that this Account will promote awareness about in vitro organ microphysiological systems for modeling infections and stimulate joint efforts across multiple disciplines to understand emerging and re-emerging pandemic diseases and rapidly identify innovative interventions.

Impaired Antibody-Dependent Cellular Cytotoxicity in a Spanish Cohort of Patients With COVID-19 Admitted to the ICU

SARS-CoV-2 infection causes COVID-19, ranging from mild to critical disease in symptomatic subjects. It is essential to better understand the immunologic responses occurring in patients with the most severe outcomes. In this study, parameters related to the humoral immune response elicited against SARS-CoV-2 were analysed in 61 patients with different presentations of COVID-19 who were recruited in Hospitals and Primary Healthcare Centres in Madrid, Spain, during the first pandemic peak between April and June 2020. Subjects were allocated as mild patients without hospitalization, severe patients hospitalized or critical patients requiring ICU assistance. Critical patients showed significantly enhanced levels of B cells with memory and plasmablast phenotypes, as well as higher levels of antibodies against SARS-CoV-2 with neutralization ability, which were particularly increased in male gender. Despite all this, antibody-dependent cell-mediated cytotoxicity was defective in these individuals. Besides, patients with critical COVID-19 also showed increased IgG levels against herpesvirus such as CMV, EBV, HSV-1 and VZV, as well as detectable CMV and EBV viremia in plasma. Altogether, these results suggest an enhanced but ineffectual immune response in patients with critical COVID-19 that allowed latent herpesvirus reactivation. These findings should be considered during the clinical management of these patients due to the potential contribution to the most severe disease during SARS-CoV-2 infection.

High Rate of Mutational Events in SARS-CoV-2 Genomes across Brazilian Geographical Regions, February 2020 to June 2021

Brazil was considered one of the emerging epicenters of the coronavirus pandemic in 2021, experiencing over 3000 daily deaths caused by the virus at the peak of the second wave. In total, the country had more than 20.8 million confirmed cases of COVID-19, including over 582,764 fatalities. A set of emerging variants arose in the country, some of them posing new challenges for COVID-19 control. The goal of this study was to describe mutational events across samples from Brazilian SARS-CoV-2 sequences publicly obtainable on Global Initiative on Sharing Avian Influenza Data-EpiCoV (GISAID-EpiCoV) platform and to generate indexes of new mutations by each genome. A total of 16,953 SARS-CoV-2 genomes were obtained, which were not proportionally representative of the five Brazilian geographical regions. A comparative sequence analysis was conducted to identify common mutations located at 42 positions of the genome (38 were in coding regions, whereas two were in 5' and two in 3' UTR). Moreover, 11 were synonymous variants, 27 were missense variants, and more than 44.4% were located in the spike gene. Across the total of single nucleotide variations (SNVs) identified, 32 were found in genomes obtained from all five Brazilian regions. While a high genomic diversity has been reported in Europe given the large number of sequenced genomes, Africa has demonstrated high potential for new variants. In South America, Brazil, and Chile, rates have been similar to those found in South Africa and India, providing enough "space" for new mutations to arise. Genomic surveillance is the central key to identifying the emerging variants of SARS-CoV-2 in Brazil and has shown that the country is one of the "hotspots" in the generation of new variants.

IgG Antibodies Generation and Side Effects Caused by Ad5-nCoV Vaccine (CanSino Biologics) and BNT162b2 Vaccine (Pfizer/BioNTech) among Mexican Population

SARS-CoV-2 has rapidly generated a pandemic. Vaccines are currently being rolled out to control the viral spread and prevent deaths. Emergency vaccines, using new platforms, have been approved. Their effectiveness, safety and immunogenicity in different populations are not fully known. This study aimed to discover the immunogenicity of the messenger ribonucleic acid (mRNA) BNT162b2 and adenovirus vector Ad5-nCoV vaccines through IgG antibody generation against subunit 1 of protein S (S1 IgG) and assess the side effects of the vaccines. A total of 115 vaccinated people were included, 61 of whom received the BNT162b2 vaccine, while 54 received Ad5-nCoV. Measurements of S1 IgG antibodies were carried out using the enzyme-linked immunosorbent assay (ELISA) technique. The BNT162b2 vaccine generated S1 IgG antibodies in 80.3% of the participants after the first dose. The number of seropositive participants increased to 98.36% with the administration of the second dose. The Ad5-nCoV vaccine generated S1 IgG antibodies in 88.89% of those vaccinated. Women generated more antibodies when administered either vaccine. There were no serious adverse effects from vaccination. In conclusion, not all participants had detectable S1 IgG antibodies. The Ad5-nCoV vaccine presented the most seronegative cases. The studied vaccines were shown to be safe.

Seropositivity in blood donors and pregnant women during the first year of SARS-CoV-2 transmission in Stockholm, Sweden

BACKGROUND

In Sweden, social restrictions to contain SARS-CoV-2 have primarily relied upon voluntary adherence to a set of recommendations. Strict lockdowns have not been enforced, potentially affecting viral dissemination. To understand the levels of past SARS-CoV-2 infection in the Stockholm population before the start of mass vaccinations, healthy blood donors and pregnant women (n = 5,100) were sampled at random between 14 March 2020 and 28 February 2021.

METHODS

In this cross-sectional prospective study, otherwise-healthy blood donors (n = 2,600) and pregnant women (n = 2,500) were sampled for consecutive weeks (at four intervals) throughout the study period. Sera from all participants and a cohort of historical (negative) controls (n = 595) were screened for IgG responses against stabilized trimers of the SARS-CoV-2 spike (S) glycoprotein and the smaller receptor-binding domain (RBD). As a complement to standard analytical approaches, a probabilistic (cut-off independent) Bayesian framework that assigns likelihood of past infection was used to analyse data over time.

SETTING

Healthy participant samples were randomly selected from their respective pools through Karolinska University Hospital. The study was carried out in accordance with Swedish Ethical Review Authority: registration number 2020-01807.

PARTICIPANTS

No participants were symptomatic at sampling, and blood donors were all over the age of 18. No additional metadata were available from the participants.

RESULTS

Blood donors and pregnant women showed a similar seroprevalence. After a steep rise at the start of the pandemic, the seroprevalence trajectory increased steadily in approach to the winter second wave of infections, approaching 15% of all individuals surveyed by 13 December 2020. By the end of February 2021, 19% of the population tested seropositive. Notably, 96% of seropositive healthy donors screened (n = 56) developed neutralizing antibody responses at titres comparable to or higher than those observed in clinical trials of SARS-CoV-2 spike mRNA vaccination, supporting that mild infection engenders a competent B-cell response.

CONCLUSIONS

These data indicate that in the first year since the start of community transmission, seropositivity levels in metropolitan in Stockholm had reached approximately one in five persons, providing important baseline seroprevalence information prior to the start of vaccination.

Recovery from Acute SARS-CoV-2 Infection and Development of Anamnestic Immune Responses in T Cell-Depleted Rhesus Macaques

Severe coronavirus disease 2019 (COVID-19) has been associated with T cell lymphopenia, but no causal effect of T cell deficiency on disease severity has been established. To investigate the specific role of T cells in recovery from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, we studied rhesus macaques that were depleted of either CD4+, CD8+, or both T cell subsets prior to infection. Peak virus loads were similar in all groups, but the resolution of virus in the T cell-depleted animals was slightly delayed compared to that in controls. The T cell-depleted groups developed virus-neutralizing antibody responses and class switched to IgG. When reinfected 6 weeks later, the T cell-depleted animals showed anamnestic immune responses characterized by rapid induction of high-titer virus-neutralizing antibodies, faster control of virus loads, and reduced clinical signs. These results indicate that while T cells play a role in the recovery of rhesus macaques from acute SARS-CoV-2 infections, their depletion does not induce severe disease, and T cells do not account for the natural resistance of rhesus macaques to severe COVID-19. Neither primed CD4+ nor CD8+ T cells appeared critical for immunoglobulin class switching, the development of immunological memory, or protection from a second infection. IMPORTANCE Patients with severe COVID-19 often have decreased numbers of T cells, a cell type important in fighting most viral infections. However, it is not known whether the loss of T cells contributes to severe COVID-19 or is a consequence of it. We studied rhesus macaques, which develop only mild COVID-19, similar to most humans. Experimental depletion of T cells slightly prolonged their clearance of virus, but there was no increase in disease severity. Furthermore, they were able to develop protection from a second infection and produced antibodies capable of neutralizing the virus. They also developed immunological memory, which allows a much stronger and more rapid response upon a second infection. These results suggest that T cells are not critical for recovery from acute SARS-CoV-2 infections in this model and point toward B cell responses and antibodies as the essential mediators of protection from re-exposure.

Protective humoral and cellular immune responses to SARS-CoV-2 persist up to 1 year after recovery

SARS-CoV-2 vaccination has been launched worldwide to build effective population-level immunity to curb the spread of this virus. The effectiveness and duration of protective immunity is a critical factor for public health. Here, we report the kinetics of the SARS-CoV-2 specific immune response in 204 individuals up to 1-year after recovery from COVID-19. RBD-IgG and full-length spike-IgG concentrations and serum neutralizing capacity decreases during the first 6-months, but is maintained stably up to 1-year after hospital discharge. Even individuals who had generated high IgG levels during early convalescent stages had IgG levels that had decreased to a similar level one year later. Notably, the RBD-IgG level positively correlates with serum neutralizing capacity, suggesting the representative role of RBD-IgG in predicting serum protection. Moreover, viral-specific cellular immune protection, including spike and nucleoprotein specific, persisted between 6 months and 12 months. Altogether, our study supports the persistence of viral-specific protective immunity over 1 year.

An Overview of Vaccines against SARS-CoV-2 in the COVID-19 Pandemic Era

The emergence of SARS-CoV-2 in late 2019 led to the COVID-19 pandemic all over the world. When the virus was first isolated and its genome was sequenced in the early months of 2020, the efforts to develop a vaccine began. Based on prior well-known knowledge about coronavirus, the SARS-CoV-2 spike (S) protein was selected as the main target. Currently, more than one hundred vaccines are being investigated and several of them are already authorized by medical agencies. This review summarizes and compares the current knowledge about main approaches for vaccine development, focusing on those authorized and specifically their immunogenicity, efficacy preventing severe disease, adverse side effects, protection, and ability to cope with emergent SARS-CoV-2 variants.

Impact of Prior Infection on Severe Acute Respiratory Syndrome Coronavirus 2 Transmission in Syrian Hamsters

Prior infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) provides protective immunity against reinfection. However, whether prior infection blocks SARS-CoV-2 transmission is not yet clear. Here, we evaluated the impact of prior infection on SARS-CoV-2 transmission in Syrian hamsters. Our results showed that prior infection significantly reduced SARS-CoV-2 replication in Syrian hamsters, but sterilizing immunity was not achieved. Prior infection blocked the airborne transmission of SARS-CoV-2 from previously infected Syrian hamsters to naïve Syrian hamsters and previously infected Syrian hamsters. Moreover, prior infection substantially reduced the efficiency of direct contact transmission between previously infected Syrian hamsters. However, prior infection had limited impact on SARS-CoV-2 transmission from previously infected Syrian hamsters to naïve Syrian hamsters via direct contact in the early course of infection. Human reinfection and SARS-CoV-2 transmission between a previously infected population and a healthy population would be likely, and a higher vaccination coverage rate was needed to reach herd immunity. Our work will aid the implementation of appropriate public health and social measures to control coronavirus infectious disease 2019 (COVID-19) pandemic.

COVID-19 Research: Lessons from Non-Human Primate Models

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19). It emerged from China in December 2019 and rapidly spread across the globe, causing a pandemic with unprecedented impacts on public health and economy. Therefore, there is an urgent need for the development of curative treatments and vaccines. In humans, COVID-19 pathogenesis shows a wide range of symptoms, from asymptomatic to severe pneumonia. Identifying animal models of SARS-CoV-2 infection that reflect the clinical symptoms of COVID-19 is of critical importance. Nonhuman primates (NHPss) correspond to relevant models to assess vaccine and antiviral effectiveness. This review discusses the use of NHPs as models for COVID-19 research, with focus on the pathogenesis of SARS-CoV-2 infection, drug discovery and pre-clinical evaluation of vaccine candidates.

Primary Immune Response Provides Protective Efficacy against SARS-CoV-2 Reinfection

While there is absolutely no evidence to ensure recovered patients are either likely or unlikely to get reinfected. But studies in non-human primates indicate that reinfection of recovered patients is highly unlikely. It is also clear that primary immune responses or induced immunity to severe acute respiratory syndrome coronavirus 2 remain in circulation for several months and at least temporarily confer immunity to protect from reinfection. In addition, negative virus culture analysis of re-positive suggests that positive reverse transcriptase-polymerase chain reactions in recovered patients are more likely to be false-positive, or detection of genetic remnants of virus discharged from lesions of lungs or better sampling at the time of repeat analysis. However, emerging severe acute respiratory syndrome coronavirus 2 variants are likely to be causing the infections observed in some of the recovered patients.

Cardiovascular injuries and SARS-COV-2 infection: focus on elderly people

The novel coronavirus disease (COVID-19) has hit the healthcare system worldwide. The risk of severe infection and mortality increases with advancing age, especially in subjects with comorbidities such as cardiovascular disease, hypertension, diabetes, obesity and cancer. Moreover, cardiovascular complications such as myocardial injury, heart failure and thromboembolism are frequently observed in COVID-19 cases, and several biomarkers (troponin, NTproBNP and D-Dimer) have been identified as prognostic indicators of disease severity and worst outcome. Currently, there is no specific therapy against SARS-CoV-2, although many medications are under investigation. The aim of this review will be to explore the intertwined relationship between COVID-19 disease and the cardiovascular system, focusing on elderly population. The available supportive treatments along with the related concerns in elderly patients, due to their comorbidities and polypharmacotherapy, will be explored.

ChAdOx1 nCoV-19 protection against SARS-CoV-2 in rhesus macaque and ferret challenge models

Vaccines against SARS-CoV-2 are urgently required, but early development of vaccines against SARS-CoV-1 resulted in enhanced disease after vaccination. Careful assessment of this phenomena is warranted for vaccine development against SARS CoV-2. Here we report detailed immune profiling after ChAdOx1 nCoV-19 (AZD1222) and subsequent high dose challenge in two animal models of SARS-CoV-2 mediated disease. We demonstrate in rhesus macaques the lung pathology caused by SARS-CoV-2 mediated pneumonia is reduced by prior vaccination with ChAdOx1 nCoV-19 which induced neutralising antibody responses after a single intramuscular administration. In a second animal model, ferrets, ChAdOx1 nCoV-19 reduced both virus shedding and lung pathology. Antibody titre were boosted by a second dose. Data from these challenge models on the absence of enhanced disease and the detailed immune profiling, support the continued clinical evaluation of ChAdOx1 nCoV-19.

Interlaboratory comparison of SARS-CoV2 molecular detection assays in use by U.S. veterinary diagnostic laboratories

The continued search for intermediate hosts and potential reservoirs for SARS-CoV2 makes it clear that animal surveillance is critical in outbreak response and prevention. Real-time RT-PCR assays for SARS-CoV2 detection can easily be adapted to different host species. U.S. veterinary diagnostic laboratories have used the CDC assays or other national reference laboratory methods to test animal samples. However, these methods have only been evaluated using internal validation protocols. To help the laboratories evaluate their SARS-CoV2 test methods, an interlaboratory comparison (ILC) was performed in collaboration with multiple organizations. Forty-four sets of 19 blind-coded RNA samples in Tris-EDTA (TE) buffer or PrimeStore transport medium were shipped to 42 laboratories. Results were analyzed according to the principles of the International Organization for Standardization (ISO) 16140-2:2016 standard. Qualitative assessment of PrimeStore samples revealed that, in approximately two-thirds of the laboratories, the limit of detection with a probability of 0.95 (LOD95) for detecting the RNA was ≤20 copies per PCR reaction, close to the theoretical LOD of 3 copies per reaction. This level of sensitivity is not expected in clinical samples because of additional factors, such as sample collection, transport, and extraction of RNA from the clinical matrix. Quantitative assessment of Ct values indicated that reproducibility standard deviations for testing the RNA with assays reported as N1 were slightly lower than those for N2, and they were higher for the RNA in PrimeStore medium than those in TE buffer. Analyst experience and the use of either a singleplex or multiplex PCR also affected the quantitative ILC test results.

L-SIGN is a receptor on liver sinusoidal endothelial cells for SARS-CoV-2 virus

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a pandemic. Severe disease is associated with dysfunction of multiple organs, but some infected cells do not express ACE2, the canonical entry receptor for SARS-CoV-2. Here, we report that the C-type lectin receptor L-SIGN interacted in a Ca²⁺-dependent manner with high-mannose–type N-glycans on the SARS-CoV-2 spike protein. We found that L-SIGN was highly expressed on human liver sinusoidal endothelial cells (LSECs) and lymph node lymphatic endothelial cells but not on blood endothelial cells. Using high-resolution confocal microscopy imaging, we detected SARS-CoV-2 viral proteins within the LSECs from liver autopsy samples from patients with COVID-19. We found that both pseudo-typed virus enveloped with SARS-CoV-2 spike protein and authentic SARS-CoV-2 virus infected L-SIGN–expressing cells relative to control cells. Moreover, blocking L-SIGN function reduced CoV-2–type infection. These results indicate that L-SIGN is a receptor for SARS-CoV-2 infection. LSECs are major sources of the clotting factors vWF and factor VIII (FVIII). LSECs from liver autopsy samples from patients with COVID-19 expressed substantially higher levels of vWF and FVIII than LSECs from uninfected liver samples. Our data demonstrate that L-SIGN is an endothelial cell receptor for SARS-CoV-2 that may contribute to COVID-19–associated coagulopathy.

Durable antibody response one year after hospitalization for COVID-19: A longitudinal cohort study

Objectives

Durability of the humoral immune response to SARS-CoV-2 has yet to be defined. We longitudinally evaluated during a 12-month period the antibody responses to SARS-CoV-2, and analysed predictors of antibody titres decline and seroreversion.

Methods

Prospective study conducted in a cohort of patients hospitalized for microbiologically-confirmed COVID-19. Blood and nasopharyngeal samples were sequentially obtained during hospital stay and at 1, 2, 6 and 12 months after patients’ discharge for measuring anti-spike (S) and anti-nucleocapsid (N) IgG antibody levels and SARS-CoV-2 RNA, respectively.

Results

80 non-vaccinated patients were analysed. At month 12 after discharge, 73 (91.2%) patients exhibited detectable S-IgG and 35 (43.8%) N-IgG antibody titres. A gradual wane was observed in S-IgG and N-IgG antibody titres. Linear regression showed that S-IgG decline was positively associated with peak antibody titres (coefficient [95% CI] 0.059 [0.05–0.067], p < 0.001), inversely with WHO severity score (coefficient [95% CI] −0.042 [-0.079/-0.004], p = 0.033), and there was a trivial positive association with age (coefficient [95% CI] 0.002 [0–0.005], p = 0.10); N-IgG decline was positively associated with peak antibody titres (coefficient [95% CI] 0.091 [0.078–0.105], p < 0.001). Logistic regression showed that seroreversion for S-IgG was inversely associated with peak S-IgG (OR 0.19; 95% CI, 0.04-0.45; p = 0.004); seroreversion for N-IgG was inversely associated with peak N-IgG (OR 0.71; 95% 0.53–0.90; p = 0.009) and positively with cycle threshold of RT-PCR (OR 1.14; 95% CI, 1.00–1.33; p = 0.062).

Conclusion

Anti-spike IgG antibodies remain detectable one year after hospitalization for COVID-19. Higher peak antibody titres and disease severity were associated with increased durability of detectable antibodies.

SARS-CoV2 infects pancreatic beta cells in vivo and induces cellular and subcellular disruptions that reflect beta cell dysfunction

Increasing evidence of new-onset diabetes during the COVID19 pandemic indicates that the SARS-CoV2 virus may drive beta-cell dysfunction leading to diabetes, but it is unclear if it is a primary or secondary effect. Here, we present evidence of SARS-CoV-2 infection of pancreatic beta cells in vivo using a robust and reproducible non-human primates model of mild to moderate COVID19 pathogenesis. Pancreas from SARS-CoV-2 infected subjects were positive for the SARS-CoV2 spike protein by immunohistochemistry and structures indicative of viral replication were evident by electron microscopy. Total beta cell area was decreased in SARS-CoV-2-infected pancreas, attributable to beta cell atrophy. Beta cell granularity was decreased. These histologic phenotypes persisted beyond the duration of the clinical disease course. Detailed electron microscopy of SARS-CoV-2 infected beta-cells revealed ultrastructural hallmarks of beta cell stress that are seen in islets of patients with Type 2 diabetes, including disrupted mitochondria and dilated endoplasmic reticulum. To assess the metabolic status of beta cells from SARS-CoV-2-infected subjects, we used fluorescence life-time imaging to measure the ratio of free and bound NADH as a surrogate of glycolytic and oxidative metabolism. We report an increase in free NADH levels, suggesting that beta cells from SARS-CoV-2-infected subjects adopt a more glycolytic metabolic profile. Taken together, we conclude that SARS-CoV-2 infection induces beta cell stress that may compromise beta-cell function beyond the duration of the disease course. This raises the possibility that the beta cell stress and injury may have clinical implications of the long-term future health of patients that have recovered from COVID19.

Dynamic Assay for Profiling Anti-SARS-CoV-2 Antibodies and Their ACE2/Spike RBD Neutralization Capacity

Serological assays have been widely employed during the coronavirus disease 2019 (COVID-19) pandemic to measure antibody responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and to track seroconversion in populations. However, currently available assays do not allow determination of neutralization capacity within the assay protocol. Furthermore, commercial serology assays have a high buy-in cost that is inaccessible for many research groups. We have replicated the serological enzyme-linked immunosorbent assay for the detection of SARS-CoV-2 antibody isotypes, developed at the Icahn School of Medicine at Mount Sinai, New York. Additionally, we have modified the protocol to include a neutralization assay with only a minor modification to this protocol. We used this assay to screen local COVID-19 patient sera (n = 91) and pre-COVID-19 control sera (n = 103), and obtained approximate parity with approved commercial anti-nucleoprotein-based assays with these sera. Furthermore, data from our neutralization assay closely aligns with that generated using a spike-based pseudovirus infection model when a subset of patient sera was analyzed.

Naive human B cells engage the receptor binding domain of SARS-CoV-2, variants of concern, and related sarbecoviruses

Exposure to a pathogen elicits an adaptive immune response aimed to control and eradicate. Interrogating the abundance and specificity of the naive B cell repertoire contributes to understanding how to potentially elicit protective responses. Here, we isolated naive B cells from 8 seronegative human donors targeting the SARS-CoV-2 receptor-binding domain (RBD). Single B cell analysis showed diverse gene usage with no restricted complementarity determining region lengths. We show that recombinant antibodies engage SARS-CoV-2 RBD, circulating variants, and pre-emergent coronaviruses. Representative antibodies signal in a B cell activation assay and can be affinity matured through directed evolution. Structural analysis of a naive antibody in complex with spike shows a conserved mode of recognition shared with infection-induced antibodies. Lastly, both naive and affinity-matured antibodies can neutralize SARS-CoV-2. Understanding the naive repertoire may inform potential responses recognizing variants or emerging coronaviruses enabling the development of pan-coronavirus vaccines aimed at engaging germline responses.

Isolation of antibody germline precursors targeting the receptor binding domain of coronaviruses.

Public mental health problems during COVID-19 pandemic: a large-scale meta-analysis of the evidence

The coronavirus disease 2019 (COVID-19) pandemic has exposed humans to the highest physical and mental risks. Thus, it is becoming a priority to probe the mental health problems experienced during the pandemic in different populations. We performed a meta-analysis to clarify the prevalence of postpandemic mental health problems. Seventy-one published papers (n = 146,139) from China, the United States, Japan, India, and Turkey were eligible to be included in the data pool. These papers reported results for Chinese, Japanese, Italian, American, Turkish, Indian, Spanish, Greek, and Singaporean populations. The results demonstrated a total prevalence of anxiety symptoms of 32.60% (95% confidence interval (CI): 29.10-36.30) during the COVID-19 pandemic. For depression, a prevalence of 27.60% (95% CI: 24.00-31.60) was found. Further, insomnia was found to have a prevalence of 30.30% (95% CI: 24.60-36.60). Of the total study population, 16.70% (95% CI: 8.90-29.20) experienced post-traumatic stress disorder (PTSD) symptoms during the COVID-19 pandemic. Subgroup analysis revealed the highest prevalence of anxiety (63.90%) and depression (55.40%) in confirmed and suspected patients compared with other cohorts. Notably, the prevalence of each symptom in other countries was higher than that in China. Finally, the prevalence of each mental problem differed depending on the measurement tools used. In conclusion, this study revealed the prevalence of mental problems during the COVID-19 pandemic by using a fairly large-scale sample and further clarified that the heterogeneous results for these mental health problems may be due to the nonstandardized use of psychometric tools.

Twelve-month specific IgG response to SARS-CoV-2 receptor-binding domain among COVID-19 convalescent plasma donors in Wuhan

To investigate the duration of humoral immune response in convalescent coronavirus disease 2019 (COVID-19) patients, we conduct a 12-month longitudinal study through collecting a total of 1,782 plasma samples from 869 convalescent plasma donors in Wuhan, China and test specific antibody responses. The results show that positive rate of IgG antibody against receptor-binding domain of spike protein (RBD-IgG) to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the COVID-19 convalescent plasma donors exceeded 70% for 12 months post diagnosis. The level of RBD-IgG decreases with time, with the titer stabilizing at 64.3% of the initial level by the 9th month. Moreover, male plasma donors produce more RBD-IgG than female, and age of the patients positively correlates with the RBD-IgG titer. A strong positive correlation between RBD-IgG and neutralizing antibody titers is also identified. These results facilitate our understanding of SARS-CoV-2-induced immune memory to promote vaccine and therapy development.

SARS-COV-2 seroprevalence among employees of a University Hospital in Belgium during the 2020 COVID-19 outbreak (COVEMUZ-study)

Between 19 May and 12 June 2020, employees of the UZ Brussel were recruited in this study aiming to document the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence, to investigate the potential work-related risk factors for SARS-CoV-2 infection and to estimate the proportion of asymptomatic infections. In total, 2662 participants were included of whom 7.4% had immunoglobulin G antibodies against SARS-CoV-2. Of the participants reporting a positive polymerase chain reaction for SARS-CoV-2, 89% had antibodies at the time of blood sampling. Eleven per cent of the antibody positive participants reported no recent symptoms suggestive of coronavirus disease 2019 (COVID-19). Participants reporting fever, chest pain and/or anosmia/ageusia were significantly more frequently associated with the presence of antibodies against SARS-CoV-2. The presence of antibodies was highest in the group that had had contact with COVID-19-infected individuals outside the hospital with or without using appropriate personnel protective equipment (PPE) (P < 0.001). Inside the hospital, a statistically significant difference was observed for the employees considered as low-risk exposure compared to the intermediate-risk exposure group (P = 0.005) as well as the high-risk exposure group compared to the intermediate exposure risk group (P < 0.001). These findings highlight the importance of using correct PPE.

Animal models for SARS-CoV-2 research: A comprehensive literature review

Emerging and re-emerging viral diseases can create devastating effects on human lives and may also lead to economic crises. The ongoing COVID-19 pandemic due to the novel coronavirus (nCoV), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which originated in Wuhan, China, has caused a global public health emergency. To date, the molecular mechanism of transmission of SARS-CoV-2, its clinical manifestations and pathogenesis is not completely understood. The global scientific community has intensified its efforts in understanding the biology of SARS-CoV-2 for development of vaccines and therapeutic interventions to prevent the rapid spread of the virus and to control mortality and morbidity associated with COVID-19. To understand the pathophysiology of SARS-CoV-2, appropriate animal models that mimic the biology of human SARS-CoV-2 infection are urgently needed. In this review, we outline animal models that have been used to study previous human coronaviruses (HCoVs), including severe acute respiratory syndrome coronavirus (SARS-CoV) and middle east respiratory syndrome coronavirus (MERS-CoV). Importantly, we discuss models that are appropriate for SARS-CoV-2 as well as the advantages and disadvantages of various available methods.

Long-term sero-positivity for IgG, sequelae of respiratory symptoms, and abundance of malformed sperms in a patient recovered from severe COVID-19

Patients with severe coronavirus disease in 2019 (COVID-19 pneumonia) may have many sequelae, which seriously affect their quality of life and work. Here, we report a case of infection in China, reviewed the course, treatment, and rehabilitation of a patient suffering from severe COVID-19 pneumonia, and collected his examination reports, including chest CT, laboratory examination results, lung function examination, sleep monitoring report, sex hormones, sperm morphology and activity. The patient's antiviral immunoglobulin G (IgG) continued to be positive for more than 11 months, and his small airway function was abnormal, and he suffered from respiratory problems (cough, chest pain, chest tightness, and shortness of breath), unstructured sleep apnea hypopnea syndrome, and nocturnal sleep hypoxemia. His abnormal sperm rate increased obviously, and sperm activity decreased obviously. Patients with severe COVID-19 pneumonia may have respiratory sequela, the abnormal sperm rate is obviously increased, and IgG positive can last for a long time.

Non-human primate models of human respiratory infections

Respiratory pathogens represent a great burden for humanity and a potential source of new pandemics, as illustrated by the recent emergence of coronavirus disease 2019 (COVID-19). In recent decades, biotechnological advances have led to the development of numerous innovative therapeutic molecules and vaccine immunogens. However, we still lack effective treatments and vaccines against many respiratory pathogens. More than ever, there is a need for a fast, predictive, preclinical pipeline, to keep pace with emerging diseases. Animal models are key for the preclinical development of disease management strategies. The predictive value of these models depends on their ability to reproduce the features of the human disease, the mode of transmission of the infectious agent and the availability of technologies for monitoring infection. This review focuses on the use of non-human primates as relevant preclinical models for the development of prevention and treatment for human respiratory infections.

Two-tiered SARS-CoV-2 seroconversion screening in the Netherlands and stability of nucleocapsid, spike protein domain 1 and neutralizing antibodies

BACKGROUND

Serological testing in the COVID-19 pandemic is mainly implemented to gain sero-epidemiological data, but can also retrospectively inform about suspected SARS-CoV-2 infection.

METHOD

We verified and applied a two-tiered testing strategy combining a SARS-CoV-2 receptor-binding domain (RBD)-specific lateral flow assay (LFA) with a nucleocapsid protein (NCP) IgG ELISA to assess seroconversion in n = 7241 individuals. The majority had experienced symptoms consistent with COVID-19, but had no access to RT-PCR testing. Longitudinal follow-up in n = 97 LFA + individuals was performed up to 20 weeks after initial infection using NCP and spike protein S1 domain (S1) IgG ELISAs and a surrogate virus neutralization test (sVNT).

RESULTS

Individuals reporting symptoms from January 2020 onwards showed seroconversion, as did a considerable proportion of asymptomatic individuals. Seroconversion for symptomatic and asymptomatic individuals was higher in an area with a known infection cluster compared to a low incidence area. Overall, 94% of individuals with a positive IgG result by LFA were confirmed by NCP ELISA. The proportion of ELISA-confirmed LFA results declined over time, in line with contracting NCP IgG titres during longitudinal follow-up. Neutralizing antibody activity was considerably more stable than S1 and NCP IgG titres, and both reach a plateau after approximately 100 d. The sVNT proved to be not only highly specific, but also more sensitive than the specificity-focussed two-tiered serology approach.

CONCLUSIONS

Our results demonstrate the high specificity of two-tiered serology testing and highlight the sVNT used as a valuable tool to support modelling of SARS-CoV-2 transmission dynamics, complement molecular testing and provide relevant information to individuals.

Persistence of humoral response upon SARS-CoV-2 infection

SARS‐CoV‐2 continues to leave its toll on global health and the economy. Management of the pandemic will rely heavily on the degree of adaptive immunity persistence following natural SARS‐CoV‐2 infection. Along with the progression of the pandemic, more literature on the persistence of the SARS‐CoV‐2‐specific antibody response is becoming available. Here, we summarize findings on the persistence of the humoral, including neutralizing antibody, response at three to eight months post SARS‐CoV‐2 infection in non‐pregnant adults. While the comparability of the literature is limited, findings on the detectability of immunoglobulin G class of antibodies (IgG) were most consistent and were reported in most studies to last for six to eight months. Studies investigating the response of immunoglobins M and A (IgM, IgA) were limited and reported mixed results, in particular, for IgM. The majority of studies observed neutralizing antibodies at all time points tested, which in some studies lasted up to eight months. The presence of neutralizing antibodies has been linked to protection from re‐infection, suggesting long‐term immunity to SARS‐CoV‐2. These neutralizing capacities may be challenged by emerging virus variants, but mucosal antibodies as well as memory B and T cells may optimize future immune responses. Thus, further longitudinal investigation of PCR‐confirmed seropositive individuals using sensitive assays is warranted to elucidate the nature and duration of a more long‐term humoral response.

The demography and characteristics of SARS-CoV-2 seropositive residents and staff of nursing homes for older adults in the Community of Madrid: the SeroSOS study

Background: Nursing homes for older adults have concentrated large numbers of severe cases and deaths for COVID-19.

Methods: Point seroprevalence study of nursing homes to describe the demography and characteristic of SARS-CoV-2 IgG-positive residents and staff.

Results: Clinical information and blood samples were available for 9,332 residents (mean age 86.7 ± 8.1 years, 76.4% women) and 10,614 staff (mean age 45.6 ± 11.5, 86.2% women). Up to 84.4% of residents had frailty, 84.9% co-morbidity and 69.3% cognitive impairment; 65.2% of workers were health-aides.

COVID-19 seroprevalence was 55.4% (95% CI, 54.4–56.4) for older adults and 31.5% (30.6–32.4) for staff. In multivariable analysis frailty of residents was related with seropositivity (OR: 1.19, p = 0.02). In the case of staff, age > 50 years (2.10, p < 0.001), obesity (1.19, p = 0.01), being a health-aide (1.94, p < 0.001), working in a center with high seroprevalence in residents (3.49, p < 0.001), and contact with external cases of COVID-19 (1.52, p < 0.001) were factors associated with seropositivity. Past symptoms of COVID-19 were good predictors of seropositivity for residents (5.41, p < 0.001) and staff (2.52, p < 0.001).

Conclusions: Level of dependency influences risk of COVID-19 among residents. Individual and work factors, and contacts outside the nursing home are associated with COVID-19 exposure in staff members. It is key to strengthen control measures to prevent the introduction of COVID-19 into care facilities from the community.

COVID-19 mRNA vaccine induced antibody responses against three SARS-CoV-2 variants

As SARS-CoV-2 has been circulating for over a year, dozens of vaccine candidates are under development or in clinical use. The BNT162b2 mRNA COVID-19 vaccine induces spike protein-specific neutralizing antibodies associated with protective immunity. The emergence of the B.1.1.7 and B.1.351 variants has raised concerns of reduced vaccine efficacy and increased re-infection rates. Here we show, that after the second dose, the sera of BNT162b2-vaccinated health care workers (n = 180) effectively neutralize the SARS-CoV-2 variant with the D614G substitution and the B.1.1.7 variant, whereas the neutralization of the B.1.351 variant is five-fold reduced. Despite the reduction, 92% of the seronegative vaccinees have a neutralization titre of >20 for the B.1.351 variant indicating some protection. The vaccinees' neutralization titres exceeded those of recovered non-hospitalized COVID-19 patients. Our work provides evidence that the second dose of the BNT162b2 vaccine induces cross-neutralization of at least some of the circulating SARS-CoV-2 variants.

COVID-19: individual and herd immunity

Immunity to the SARS-CoV-2 virus ensures protection against reinfection by this virus thanks to the combined action of neutralizing antibodies and T lymphocytes specific to viral proteins, in particular the Spike protein. It must be distinguished from the immune response that ensures healing of the infection following contamination that involves innate immunity, particularly type 1 interferons, and which is followed by adaptive cellular and humoral immunity. The importance of the effect of interferons is highlighted by the occurrence of severe forms of the disease in genetically deficient subjects or in patients with antibodies neutralizing type 1 interferon. Herd immunity is not an individual biological property. It is a mathematical property that qualifies the fact that when the proportion of subjects with individual immunity is high enough, there is little chance that an epidemic can occur. The level of that proportion-the herd immunity of the population can be computed under theoretical, often unrealistic, hypotheses, and is difficult to assess in natural conditions.

Zoonotic and Reverse Zoonotic Transmissibility of SARS-CoV-2

The Coronavirus Disease 2019 (COVID-19) is the first known pandemic caused by a coronavirus. Its causative agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), appears to be capable of infecting different mammalian species. Recent detections of this virus in pet, zoo, wild, and farm animals have compelled inquiry regarding the zoonotic (animal-to-human) and reverse zoonotic (human-to-animal) transmissibility of SARS-CoV-2 with the potential of COVID-19 pandemic evolving into a panzootic.

It is important to monitor the global spread of disease and to assess the significance of genomic changes to support prevention and control efforts during a pandemic. An understanding of the SARS-CoV-2 epidemiology provides opportunities to prevent the risk of repeated re-infection of humans and requires a robust One Health-based investigation. This review paper describes the known properties and the existing gaps in scientific knowledge about the zoonotic and reverse zoonotic transmissibility of the novel virus SARS-CoV-2 and the COVID-19 disease it causes.

Titers, Prevalence, and Duration of SARS-CoV-2 Antibodies in a Local COVID-19 Outbreak and Following Vaccination

Information concerning the development of neutralizing antibodies and their duration will be critical to establishing herd immunity for COVID-19. We sought to evaluate SARS-CoV-2 spike protein receptor-binding domain (RBD)-specific antibodies, their duration, and capacity for SARS-CoV-2 neutralization in volunteers while the pandemic spread within our community starting in March 2020. Those participants with the highest starting titers had the longest-lasting response, up to 12 months post-diagnosis. SARS-CoV-2 neutralization capacity was correlated with anti-RBD antibody levels. The majority of our participants with confirmed COVID-19 diagnosis had very mild or asymptomatic infections. We also detected low and largely non-neutralizing anti-RBD IgG titers in a few participants with no known COVID-19 diagnosis. Finally, we found that antibody responses induced by vaccination were significantly higher than those induced by natural infection. Thus, our study suggests that vaccination is still critical even for those naturally infected or diagnosed with COVID-19.

High titers and low fucosylation of early human anti-SARS-CoV-2 IgG promote inflammation by alveolar macrophages

Patients diagnosed with coronavirus disease 2019 (COVID-19) become critically ill primarily around the time of activation of the adaptive immune response. Here, we provide evidence that antibodies play a role in the worsening of disease at the time of seroconversion. We show that early-phase severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) spike protein-specific immunoglobulin G (IgG) in serum of critically ill COVID-19 patients induces excessive inflammatory responses by human alveolar macrophages. We identified that this excessive inflammatory response is dependent on two antibody features that are specific for patients with severe COVID-19. First, inflammation is driven by high titers of anti-spike IgG, a hallmark of severe disease. Second, we found that anti-spike IgG from patients with severe COVID-19 is intrinsically more proinflammatory because of different glycosylation, particularly low fucosylation, of the antibody Fc tail. Low fucosylation of anti-spike IgG was normalized in a few weeks after initial infection with SARS-CoV-2, indicating that the increased antibody-dependent inflammation mainly occurs at the time of seroconversion. We identified Fcγ receptor (FcγR) IIa and FcγRIII as the two primary IgG receptors that are responsible for the induction of key COVID-19-associated cytokines such as interleukin-6 and tumor necrosis factor. In addition, we show that anti-spike IgG-activated human macrophages can subsequently break pulmonary endothelial barrier integrity and induce microvascular thrombosis in vitro. Last, we demonstrate that the inflammatory response induced by anti-spike IgG can be specifically counteracted by fostamatinib, an FDA- and EMA-approved therapeutic small-molecule inhibitor of Syk kinase.

COVID-19 reinfection in a healthcare worker after exposure with high dose of virus: A case report

Reinfection with COVID-19 is possible after exposure to a high dose of the virus. Due to immunity acquired during the previous infection, light symptoms are expected. The finding indicates importance of continuous protection in healthcare workers.

Prospects for durable immune control of SARS-CoV-2 and prevention of reinfection

Immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is central to long-term control of the current pandemic. Despite our rapidly advancing knowledge of immune memory to SARS-CoV-2, understanding how these responses translate into protection against reinfection at both the individual and population levels remains a major challenge. An ideal outcome following infection or after vaccination would be a highly protective and durable immunity that allows for the establishment of high levels of population immunity. However, current studies suggest a decay of neutralizing antibody responses in convalescent patients, and documented cases of SARS-CoV-2 reinfection are increasing. Understanding the dynamics of memory responses to SARS-CoV-2 and the mechanisms of immune control are crucial for the rational design and deployment of vaccines and for understanding the possible future trajectories of the pandemic. Here, we summarize our current understanding of immune responses to and immune control of SARS-CoV-2 and the implications for prevention of reinfection.

Single-cell epigenomic landscape of peripheral immune cells reveals establishment of trained immunity in individuals convalescing from COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection often causes severe complications and even death. However, asymptomatic infection has also been reported, highlighting the difference in immune responses among individuals. Here we performed single-cell chromatin accessibility and T cell-receptor analyses of peripheral blood mononuclear cells collected from individuals convalescing from COVID-19 and healthy donors. Chromatin remodelling was observed in both innate and adaptive immune cells in the individuals convalescing from COVID-19. Compared with healthy donors, recovered individuals contained abundant TBET-enriched CD16⁺ and IRF1-enriched CD14⁺ monocytes with sequential trained and activated epigenomic states. The B-cell lineage in recovered individuals exhibited an accelerated developmental programme from immature B cells to antibody-producing plasma cells. Finally, an integrated analysis of single-cell T cell-receptor clonality with the chromatin accessibility landscape revealed the expansion of putative SARS-CoV-2-specific CD8⁺ T cells with epigenomic profiles that promote the differentiation of effector or memory cells. Overall, our data suggest that immune cells of individuals convalescing from COVID-19 exhibit global remodelling of the chromatin accessibility landscape, indicative of the establishment of immunological memory.

Insights into SARS-CoV-2 Persistence and Its Relevance

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), continues to wreak havoc, threatening the public health services and imposing economic collapse worldwide. Tailoring public health responses to the SARS-CoV-2 pandemic depends on understanding the mechanism of viral replication, disease pathogenesis, accurately identifying acute infections, and mapping the spreading risk of hotspots across the globe. However, effective identification and isolation of persons with asymptomatic and mild SARS-CoV-2 infections remain the major obstacles to efforts in controlling the SARS-CoV-2 spread and hence the pandemic. Understanding the mechanism of persistent viral shedding, reinfection, and the post-acute sequalae of SARS-CoV-2 infection (PASC) is crucial in our efforts to combat the pandemic and provide better care and rehabilitation to survivors. Here, we present a living literature review (January 2020 through 15 March 2021) on SARS-CoV-2 viral persistence, reinfection, and PASC. We also highlight potential areas of research to uncover putative links between viral persistence, intra-host evolution, host immune status, and protective immunity to guide and direct future basic science and clinical research priorities.

A Synthetic Peptide CTL Vaccine Targeting Nucleocapsid Confers Protection from SARS-CoV-2 Challenge in Rhesus Macaques

BACKGROUND

Persistent transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has given rise to a COVID-19 pandemic. Several vaccines, conceived in 2020, that evoke protective spike antibody responses are being deployed in mass public health vaccination programs. Recent data suggests, however, that as sequence variation in the spike genome accumulates, some vaccines may lose efficacy.

METHODS

Using a macaque model of SARS-CoV-2 infection, we tested the efficacy of a peptide-based vaccine targeting MHC class I epitopes on the SARS-CoV-2 nucleocapsid protein. We administered biodegradable microspheres with synthetic peptides and adjuvants to rhesus macaques. Unvaccinated control and vaccinated macaques were challenged with 1 × 108 TCID50 units of SARS-CoV-2, followed by assessment of clinical symptoms and viral load, chest radiographs, and sampling of peripheral blood and bronchoalveolar lavage (BAL) fluid for downstream analysis.

RESULTS

Vaccinated animals were free of pneumonia-like infiltrates characteristic of SARS-CoV-2 infection and presented with lower viral loads relative to controls. Gene expression in cells collected from BAL samples of vaccinated macaques revealed a unique signature associated with enhanced development of adaptive immune responses relative to control macaques.

CONCLUSIONS

We demonstrate that a room temperature stable peptide vaccine based on known immunogenic HLA class I bound CTL epitopes from the nucleocapsid protein can provide protection against SARS-CoV-2 infection in nonhuman primates.

Wildlife rehabilitation centers as a potential source of transmission of SARS-CoV-2 into native wildlife of Latin America

The COVID-19 pandemic has impacted the entire world, causing a great number of mortality of humans and affecting the economy, while conservation efforts are finally recognized to prevent further pandemics. The wildlife rehabilitation centers (WRCs) play a relevant role in animal welfare; nevertheless, they also represent an imminent risk of pathogen transmission between humans-to-animals and between animals. Moreover, WRCs could spread pathogens into natural habitats through the reintroduction of infectious individuals. These biosafety concerns at WRCs may increase as the economic and social impact of the COVID-19 extends. We explored the current situation of Latin American WRCs under the COVID-19 pandemic to determine the feasibility of SARS-CoV-2 introduction, amplification, and spread within these institutions. We surveyed WRCs from eight Latin American countries. We found that pandemic is affecting these institutions in many aspects: workers with symptoms compatible with COVID-19, reduced economic resources, and lack of information and support from governmental authorities. These have forced WRCs to reduce the workforce, veterinary visits, and animal food rations and to increase the number of animals released. This scenario generates a risky environment for the transmission of SARS-CoV-2, especially for felids, mustelids, and non-human primates. Therefore, it is imperative to respect quarantine periods, monitor incoming patients, increase biosecurity measures, develop and apply guidelines and recommendations for the protection of personnel and biosafety of enclosures and instruments. It is of utmost importance the proper and safer reintroduction of recovered wildlife.

[Susceptibility of animal species to experimental SARS-CoV-2 (Coronaviridae: Coronavirinae: Betacoronavirus; Sarbecovirus) infection]

Due to the new coronavirus infection pandemic, the global scientific community has been forced to change the direction of the most research, focusing on vaccine development as well as the search for new antiviral drugs to treat COVID-19. The choice of experimental models, timeframe and approaches for evaluating drugs and vaccines under development is crucial for the development of effective measures to prevent and control this disease.The purpose of this review was to summarize the relevant data concerning the susceptibility of laboratory animals to SARS-CoV-2. This paper describes the most virus-susceptible animal species that can be used to reproduce coronavirus infection, stressing the main advantages and disadvantages of each of them.According to the latest data, small rodents (Rodentia) and non-human primates (Strepsirrhini) are commonly used in the scientific community to model coronavirus infection. The viral load in the upper and lower parts of the respiratory system, clinical symptoms of infection (weight loss, body temperature and general health status), pathomorphological picture in target organs and the production of antibodies after infection are considered to the main markers of pathology. Despite the vast amount of data, none of the described models of SARS-CoV-2 infection may be considered a gold standard, since they do not reproduce all spectrum of morphological and pathogenetic mechanisms of infection, and do not fully reflect the clinical picture observed in patients in human population.Based on the analyzed literature data, we suppose that Syrian hamster (Mesocricetus auratus) and mice (Muridae) expressing the angiotensin converting enzyme receptor 2 (ACE2) are the most suitable animal species for their use in experiments with SARS-CoV-2 infection. The development of neutralizing antibodies makes it possible to evaluate the efficacy of vaccines, while the course and severity of symptoms infection makes the use of mice and hamsters especially popular for screening pharmacological substances with antiviral mechanism of action, when their administration can prevent or slow the disease progression.

COVID-19 and SARS-CoV-2: Everything we know so far – A comprehensive review

Coronavirus disease-2019 (COVID-19) emerged as a unique type of pneumonia outbreak in the Wuhan city of China in 2019 and spread to all its provinces in a matter of days and then to every continent of the world except Antarctica within 3–4 month. This paper aims to comprehensively consolidate the available information about COVID-19 and present all the possible information about this disease in form of a single paper to readers. Unparalleled research and exhaustive studies of everything about the disease and its causative virus, i.e., severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), are underway since its emergence. The genome sequence of the virus was made available within a record short time by China, making possible immediate study of its structure and characteristics. The routes of transmission of the disease, signs and symptoms, incubation period, pathogenesis, and pathophysiology have been extensively studied and presented in an organized way in this review paper. The number of confirmed cases and case fatality and mortality rates are updated regularly. The different diagnostic mechanisms have been characterized. Testing and management criteria and protocols have been adopted. Extensive efforts are underway for finding a treatment of the disease and developing a vaccine against it. A number of vaccines are available even in markets in different countries. More and more ways of personal protection, prevention, and mitigation of the disease are being explored and shared. While the outbreak has been declared as pandemic, the response of scientists was timely and enormous; thousands of publications about various aspects and impact of the diseases and its causative virus are there on the World Health Organization database and many more studies are underway. The purpose of writing this review article is to provide a comprehensive summary of the major aspects and important scientific findings so far, about COVID-19 and SARS-CoV-2, in a single article for ready reference.

Challenges and Issues of Anti-SARS-CoV-2 Vaccines

At the beginning of 2021, anti-SARS-CoV-2 vaccination campaigns had been launched in almost 60 countries with more than 500 million doses having been distributed. In addition to the few vaccines already in use, many other candidates are in preclinical phases or experimental stages in humans. Despite the fact that the availability of anti-SARS-CoV-2 vaccine constitutes a major advance and appear to be the only way to control the pandemic, some investigation remains to be carried out, and this is notably concerning the impact on transmissibility, the duration of the conferred protection in the mid- and long term, the effectiveness against present and future viral mutants, or the ideal schedule that should be applied. In this paper, we review the circumstances that facilitated such a rapid development of anti-SARS-CoV-2 vaccines and summarize the different vaccine platforms under investigation as well as their present results and perspectives in different settings. We also discuss the indications of vaccination under special conditions, such as a history of previous COVID-19 infection or belonging to extreme age categories like children and elderly. Overall, this review highlights the multiple challenges to face if aiming to find a global solution to the pandemic through high vaccination coverage all over the world.

Protection against reinfection with D614- or G614-SARS-CoV-2 isolates in golden Syrian hamster

Reinfections with SARS-CoV-2 have already been documented in humans, although its real incidence is currently unknown. Besides having a great impact on public health, this phenomenon raises the question of immunity generated by a single infection is sufficient to provide sterilizing/protective immunity to a subsequent SARS-CoV-2 re-exposure. The Golden Syrian hamster is a manageable animal model to explore immunological mechanisms able to counteract COVID-19, as it recapitulates pathological aspects of mild to moderately affected patients. Here, we report that SARS-CoV-2-inoculated hamsters resolve infection in the upper and lower respiratory tracts within seven days upon inoculation with the Cat01 (G614) SARS-CoV-2 isolate. Three weeks after the primary challenge, and despite high titres of neutralizing antibodies, half of the animals were susceptible to reinfection by both identical (Cat01, G614) and variant (WA/1, D614) SARS-CoV-2 isolates. However, upon re-inoculation, only nasal tissues were transiently infected with much lower viral replication than those observed after the first inoculation. These data indicate that a primary SARS-CoV-2 infection is not sufficient to elicit a sterilizing immunity in hamster models but protects against lung disease.