BCG administration promotes the long-term protection afforded by a single-dose intranasal adenovirus-based SARS-CoV-2 vaccine (preprint)

Despite medical interventions and several approved vaccines, the COVID-19 pandemic is continuing into its third year. Recent publications have explored single-dose intranasal (i.n.) adenovirus-based vaccines as an effective strategy for curbing SARS-CoV-2 in naive animal models. However, the effects of prior immunizations and infections have yet to be considered within these models. Here, we investigate the immunomodulatory effects of Mycobacterium bovis BCG pre-immunization on a subsequent S-protein expressing i.n. Ad vaccination, termed Ad(Spike). We found that Ad(Spike) alone conferred long-term protection from severe SARS-CoV-2 pathology within a mouse model, yet it was unable to limit initial infection 6 months post-vaccination. While i.n. Ad(Spike) retains some protective effect after 6 months, a single administration of BCG-Danish prior to Ad(Spike) vaccination potentiates its ability to control viral replication of the B.1.351 SARS-CoV-2 variant within the respiratory tract. Though BCG-Danish had no effect on the ability of Ad(Spike) to generate and maintain humoral immunity, it promoted the generation of cytotoxic and Th1 responses over suppressive FoxP3+ TREG cells in the lungs of infected mice. These data demonstrate a novel vaccination strategy that may prove useful in limiting future viral pandemics by potentiating the long-term efficacy of next generation mucosal vaccines within the context of the safe and widely distributed BCG vaccine.

Use of whole genome sequencing to identify low-frequency mutations in COVID-19 patients treated with remdesivir (preprint)

Background: We investigate the effects of remdesivir (RDV) treatment on intra-host SARS-CoV-2 diversity and low-frequency mutations in moderately ill hospitalized COVID-19 patients and compare them to patients without RDV treatment. Methods: Sequential collections of nasopharyngeal and mid-turbinate swabs were obtained from 16 patients with and 31 patients without RDV treatment. A total of 113 samples were sequenced and mutation analyses were performed. Results: We did not identify any drug resistant mutations during RDV therapy. In genes encoding and associated with the replication complex, low-frequency minority variants that do not reach fixation within the sampling period were detected in 6/16 (37.5%) and 14/31 (45%) patients with and without RDV treatment respectively. We did not detect significant differences in within-host diversity and positive selection between the RDV-treated and untreated groups. Conclusions: Minimal intra-host variability and stochastic low-frequency variants detected in moderately ill patients suggests little selective pressure in patients receiving short courses of RDV. Patients undergoing short regimens of RDV therapy should continue to be monitored.

Evaluation of real and perceived risk to health care workers caring for patients with the Omicron variant of the SARS-CoV-2 virus in surgery and obstetrics (preprint)

Introduction The Omicron variant of the SARS-CoV-2 virus is described as more contagious than previous variants. We sought to assess risk to healthcare workers (HCWs) caring for patients with COVID-19 in surgical/obstetrical settings, and the perception of risk amongst this group. Methods From January to April, 2022, reverse transcription polymerase chain reaction was used to detect the presence of SARS-CoV-2 viral RNA in patient, environmental (floor, equipment, passive air) samples, and HCWs masks (inside surface) during urgent surgery or obstetrical delivery for patients with SARS-CoV-2 infection. The primary outcome was the proportion of HCWs masks testing positive. Results were compared with our previous cross-sectional study involving obstetrical/surgical patients with earlier variants (2020/21). HCWs completed a risk perception electronic questionnaire. Results 11 patients were included: 3 vaginal births and 8 surgeries. 5/108 samples (5%) tested positive (SARS-CoV-2 Omicron) viral RNA: 2/5 endotracheal tubes, 1/22 floor samples, 1/4 patient masks and 1 nasal probe. No samples from the HCWs masks (0/35), surgical equipment (0/10) and air samples (0/11) tested positive. No significant differences were found between the Omicron and 2020/21 patient groups positivity rates (Mann-Whitney U test, p = 0.838) or the level of viral load from the naso-pharyngeal swabs (p = 0.405). Nurses had a higher risk perception than physicians (p = 0.0377). Conclusion No significant difference in contamination rates were found between SARS-CoV-2 Omicron BA.1 and previous variants in surgical/obstetrical settings. This is reassuring as no HCW mask was positive and no HCW tested positive for COVID-19 post-exposure.

Antibody avidity and multi-specificity combined to confer protection against SARS-CoV-2 and resilience against viral escape (preprint)

SARS-CoV-2, the causative agent of COVID-19, has been responsible for a global pandemic. Monoclonal antibodies have been used as antiviral therapeutics, but have been limited in efficacy by viral sequence variability in emerging variants of concern (VOCs), and in deployment by the need for high doses. In this study, we leverage the MULTI-specific, multi-Affinity antiBODY (Multabody, MB) platform, derived from the human apoferritin protomer, to drive the multimerization of antibody fragments and generate exceptionally potent and broad SARS-CoV-2 neutralizers. CryoEM revealed a high degree of homogeneity for the core of these engineered antibody-like molecules at 2.1 [A] resolution. We demonstrate that neutralization potency improvements of the MB over corresponding IgGs translates into superior in vivo protection: in the SARS-CoV-2 mouse challenge model, comparable in vivo protection was achieved for the MB delivered at 30x lower dose compared to the corresponding IgGs. Furthermore, we show how MBs potently neutralize SARS-CoV-2 VOCs by leveraging augmented avidity, even when corresponding IgGs lose their ability to neutralize potently. Multiple mAb specificities could also be combined into a single MB molecule to expand the neutralization breadth beyond SARS-CoV-2 to other sarbecoviruses. Our work demonstrates how avidity and multi-specificity combined can be leveraged to confer protection and resilience against viral diversity that exceeds that of traditional monoclonal antibody therapies.

Sphingosine kinases promote Ebola virus infection and can be targeted to inhibit filoviruses, coronaviruses, and arenaviruses using late endocytic trafficking to enter cells (preprint)

Entry of enveloped viruses in host cells requires the fusion of the viral and host cell membranes, a process that is facilitated by viral fusion proteins protruding from the viral envelope. For fusion, viral fusion proteins need to be triggered by host factors and for some viruses, such as Ebola virus (EBOV) and Lassa fever virus, this event occurs inside endosomes and/or lysosomes. Consequently, these late-penetrating viruses must be internalized and delivered to entry-conducive intracellular vesicles. Because endocytosis and vesicular trafficking are tightly regulated cellular processes, late penetrating viruses also depend on specific host factors, such as signaling molecules, for efficient viral delivery to the site of fusion, suggesting that these could be targeted for antiviral therapy. In this study, we investigated a role for sphingosine kinases (SKs) in viral entry and found that chemical inhibition of sphingosine kinase 1 (SK1) and/or SK2 and knockdown of SK1 or SK2, inhibited entry of EBOV into host cells. Mechanistically, inhibition of SK1 and/or SK2 prevented EBOV from reaching late-endosomes and lysosomes that are positive for the EBOV receptor, Niemann Pick C1 (NPC1). Furthermore, we present evidence that suggests the trafficking defect caused by SK1/2 inhibition occurs independently of S1P signaling through cell-surface S1PRs. Lastly, we found that chemical inhibition of SKs prevents entry of other late-penetrating viruses, including arenaviruses and coronaviruses, in addition to inhibiting infection by replication competent EBOV and SARS-CoV-2 in Huh7.5 cells. In sum, our results highlight an important role played by SKs in endocytic trafficking which can be targeted to inhibit entry of late-penetrating viruses. SK inhibitors could serve as a starting point for the development of broad-spectrum antiviral therapeutics.

Immunogenicity of convalescent and vaccinated sera against clinical isolates of ancestral SARS-CoV-2, beta, delta, and omicron variants (preprint)

The omicron variant of concern (VOC) of SARS-CoV-2 was first reported in November 2021 in Botswana and South Africa. Omicron variant has evolved multiple mutations within the spike protein and the receptor binding domain (RBD), raising concerns of increased antibody evasion. Here, we isolated infectious omicron from a clinical specimen obtained in Canada. The neutralizing activity of sera from 65 coronavirus disease (COVID-19) vaccine recipients and convalescent individuals against clinical isolates of ancestral SARS-CoV-2, beta, delta, and omicron VOCs was assessed. Convalescent sera from unvaccinated individuals infected by the ancestral virus during the first wave of COVID-19 in Canada (July, 2020) demonstrated reduced neutralization against beta, delta and omicron VOCs. Convalescent sera from unvaccinated individuals infected by the delta variant (May-June, 2021) neutralized omicron to significantly lower levels compared to the delta variant. Sera from individuals that received three doses of the Pfizer or Moderna vaccines demonstrated reduced neutralization of both delta and omicron variants relative to ancestral SARS-CoV-2. Sera from individuals that were naturally infected with ancestral SARS-CoV-2 and subsequently received two doses of the Pfizer vaccine induced significantly higher neutralizing antibody levels against ancestral virus and all VOCs. Importantly, infection alone, either with ancestral SARS-CoV-2 or the delta variant was not sufficient to induce high neutralizing antibody titers against omicron. This data will inform current booster vaccination strategies and we highlight the need for additional studies to identify longevity of immunity against SARS-CoV-2 and optimal neutralizing antibody levels that are necessary to prevent infection and/or severe COVID-19.

Detection of SARS CoV-2 contamination in the Operating Room and Birthing Room Setting: Risks to attending health care workers (preprint)

BackgroundThe exposure risks to front-line health care workers who are in close proximity for prolonged periods of time, caring for COVID-19 patients undergoing surgery or obstetrical delivery is unclear. Understanding of sample types that may harbour virus is important for evaluating risk. ObjectivesTo determine if SARS-CoV-2 viral RNA from patients with COVID-19 undergoing surgery or obstetrical care is present in: 1) the peritoneal cavity of males and females 2) the female reproductive tract, 3) the environment of the surgery or delivery suite (surgical instruments, equipment used, air or floors) and 4) inside the masks of the attending health care workers. MethodsThe presence of SARS-CoV-2 viral RNA in patient, environmental and air samples was identified by real time reverse transcriptase polymerase chain reaction (RT-PCR). Air samples were collected using both active and passive sampling techniques. ResultsIn this multi-centre observational case series, 32 patients with COVID-19 underwent urgent surgery or obstetrical delivery and 332 patient and environmental samples were collected and analyzed to determine if SARS-CoV-2 RNA was present. SARS-CoV-2 RNA was detected in: 4/24(16.7%) patient samples, 5/60(8.3%) floor, 1/54(1.9%) air, 10/23(43.5%) surgical instruments/equipment, 0/24 cautery filters and 0/143 inner surface of mask samples. ConclusionsWhile there is evidence of SARS-CoV-2 RNA in the surgical and obstetrical operative environment (6% of samples taken), the finding of no detectable virus inside the masks worn by the medical teams would suggest a low risk of infection for our health care workers using appropriate personal protective equipment (PPE).

Surface and air contamination with SARS-CoV-2 from hospitalized COVID-19 patients in Toronto, Canada (preprint)

Background The aim of this prospective cohort study was to determine the burden of SARS-CoV-2 in air and on surfaces in rooms of patients hospitalized with COVID-19, and to identify patient characteristics associated with SARS-CoV-2 environmental contamination. Methods Nasopharyngeal swabs, surface, and air samples were collected from the rooms of 78 inpatients with COVID-19 at six acute care hospitals in Toronto from March to May 2020. Samples were tested for SARS-CoV-2 viral RNA and cultured to determine potential infectivity. Whole viral genomes were sequenced from nasopharyngeal and surface samples. Association between patient factors and detection of SARS-CoV-2 RNA in surface samples were investigated using a mixed-effects logistic regression model. Findings SARS-CoV-2 RNA was detected from surfaces (125/474 samples; 42/78 patients) and air (3/146 samples; 3/45 patients) in COVID-19 patient rooms; 14% (6/42) of surface samples from three patients yielded viable virus. Viral sequences from nasopharyngeal and surface samples clustered by patient. Multivariable analysis indicated hypoxia at admission, a PCR-positive nasopharyngeal swab with a cycle threshold of [≤]30 on or after surface sampling date, higher Charlson co-morbidity score, and shorter time from onset of illness to sample date were significantly associated with detection of SARS-CoV-2 RNA in surface samples. Interpretation The infrequent recovery of infectious SARS-CoV-2 virus from the environment suggests that the risk to healthcare workers from air and near-patient surfaces in acute care hospital wards is likely limited. Surface contamination was greater when patients were earlier in their course of illness and in those with hypoxia, multiple co-morbidities, and higher SARS-CoV-2 RNA concentration in NP swabs. Our results suggest that, while early detection and isolation of COVID-19 patients is important, air and surfaces may pose limited risk a few days after admission to acute care hospitals.

Peginterferon-Lambda for the Treatment of COVID-19 in Outpatients (preprint)

Background: There are currently no effective treatments for outpatients with coronavirus disease. 2019 (COVID-19). Interferon-lambda-1 is a Type III interferon involved in the innate antiviral response with activity against respiratory pathogens.Methods: In this double-blind, placebo-controlled trial, outpatients with laboratory-confirmed COVID-19 were randomized to a single subcutaneous injection of peginterferon-lambda 180μg or placebo within 7 days of symptom onset or first positive swab if asymptomatic. The primary endpoint was proportion negative for SARS-CoV-2 RNA on Day 7 post-injection.Results: There were 30 patients per arm, with median baseline SARS-CoV-2 viral load of 6.71 (IQR 1.3-8.0) log copies/mL. The decline in SARS-CoV-2 RNA was greater in those treated with peginterferon-lambda than placebo (p=0.04). On Day 7, 24 participants (80%) in the peginterferon-lambda group had an undetectable viral load compared to 19 (63%) in the placebo arm (p=0.15). After controlling for baseline viral load, peginterferon-lambda treatment resulted in a 4.12-fold (95CI 1.15-16.7, p=0.029) higher likelihood of viral clearance by Day 7. Of those with baseline viral load above 10E6 copies/mL, 15/19 (79%) in the peginterferon-lambda group were undetectable on Day 7 compared to 6/16 (38%) in the placebo group (p=0.012). Adverse events were similar between groups with only mild reversible transaminase elevations more frequently observed in the peginterferon-lambda group.Conclusion: Peginterferon-lambda accelerated viral decline in outpatients with COVID-19 resulting in a greater proportion with viral clearance by Day 7, particularly in those with high baseline viral load. Peginterferon-lambda may have potential to prevent clinical deterioration and shorten duration of viral shedding.Trial Registration: NCT04354259Funding Statement: This study was supported by the Toronto COVID-19 Action Initiative, University of Toronto and the Ontario First COVID-19 Rapid Research Fund. Medication was supplied by Eiger BioPharma. Declaration of Interests: JJF reports research support unrelated to this work from Eiger BioPharmaceuticals. BC has received research support unrelated to this work from Nubiyota LLC and Sanofi. IC and CH are employees of Eiger BioPharmaceuticals. JSG is a board member and founder of Eiger BioPharmaceuticals, Inc., in which he has an equity interest, and is an inventor on a patent application for the use of interferon lambda to treat coronavirus infections. All other authors have nothing to declare. Ethics Approval Statement: The Research Ethics Boards of all participating institutions approved the study, which was conducted under a Clinical Trial Application approved by Health Canada.

Early temporal dynamics of cellular responses to SARS-CoV-2 (preprint)

Type I interferons (IFNs) are our first line of defence against a virus. Protein over-expression studies have suggested the ability of SARS-CoV-2 proteins to block IFN responses. Emerging data also suggest that timing and extent of IFN production is associated with manifestation of COVID-19 severity. In spite of progress in understanding how SARS-CoV-2 activates antiviral responses, mechanistic studies into wildtype SARS-CoV-2-mediated induction and inhibition of human type I IFN responses are lacking. Here we demonstrate that SARS-CoV-2 infection induces a mild type I IFN response in vitro and in moderate cases of COVID-19. In vitro stimulation of type I IFN expression and signaling in human airway epithelial cells is associated with activation of canonical transcriptions factors, and SARS-CoV-2 is unable to inhibit exogenous induction of these responses. Our data demonstrate that SARS-CoV-2 is not adept in blocking type I IFN responses and provide support for ongoing IFN clinical trials. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/158154v2_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@193c540org.highwire.dtl.DTLVardef@7b106forg.highwire.dtl.DTLVardef@1741cfforg.highwire.dtl.DTLVardef@1bde68_HPS_FORMAT_FIGEXP M_FIG GRAPHICAL SUMMARY C_FIG