The role of N-glycosylation in spike antigenicity for the SARS-CoV-2 gamma variant

The emergence of SARS-CoV-2 variants alters the efficacy of existing immunity towards the viral spike protein, whether acquired from infection or vaccination. Mutations that impact N-glycosylation of spike may be particularly important in influencing antigenicity, but their consequences are difficult to predict. Here, we compare the glycosylation profiles and antigenicity of recombinant viral spike of ancestral Wu-1 and the Gamma strain, which has two additional N-glycosylation sites due to amino acid substitutions in the N-terminal domain (NTD). We found that a mutation at residue 20 from threonine to asparagine within the NTD caused the loss of NTD-specific antibody COVA2-17 binding. Glycan site-occupancy analyses revealed that the mutation resulted in N-glycosylation switching to the new sequon at N20 from the native N17 site. Site-specific glycosylation profiles demonstrated distinct glycoform differences between Wu-1, Gamma, and selected NTD variant spike proteins, but these did not affect antibody binding. Finally, we evaluated the specificity of spike proteins against convalescent COVID-19 sera and found reduced cross-reactivity against some mutants, but not Gamma spike compared to Wuhan spike. Our results illustrate the impact of viral divergence on spike glycosylation and SARS-CoV-2 antibody binding profiles.

A nanobody recognizes a unique conserved epitope and potently neutralizes SARS-CoV-2 omicron variants

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) Omicron variant sub-lineages spread rapidly worldwide, mostly due to their immune-evasive properties. This has put a significant part of the population at risk for severe disease and underscores the need for effective anti-SARS-CoV-2 agents against emergent strains in vulnerable patients. Camelid nanobodies are attractive therapeutic candidates due to their high stability, ease of large-scale production, and potential for delivery via inhalation. Here, we characterize the receptor binding domain (RBD)-specific nanobody W25 and show superior neutralization activity toward Omicron sub-lineages in comparison to all other SARS-CoV2 variants. Structure analysis of W25 in complex with the SARS-CoV2 spike glycoprotein shows that W25 engages an RBD epitope not covered by any of the antibodies previously approved for emergency use. In vivo evaluation of W25 prophylactic and therapeutic treatments across multiple SARS-CoV-2 variant infection models, together with W25 biodistribution analysis in mice, demonstrates favorable pre-clinical properties. Together, these data endorse W25 for further clinical development.

A101 VIRTUAL MINDFULNESS-BASED STRESS REDUCTION FOR ADULTS WITH INFLAMMATORY BOWEL DISEASE: FEASIBILITY TRIAL PRELIMINARY RESULTS

Background

Patients with Inflammatory Bowel Disease (IBD) often suffer from high levels of anxiety and depression. Despite high rates of mental health comorbidity, a low proportion of patients receive psychiatric referrals and treatment. In Canada, provincial health care plans cover psychiatric services, making them affordable for patients and making referral efficient for gastroenterologists. Psychiatrist-led virtually-delivered Mindfulness-Based Stress Reduction (MBSR) has been associated with reducing feelings of stress, anxiety, and depression in several high-quality randomized control trials. It also reduces cost and travel requirements for patients, both which have been identified as barriers to accessing mental health treatment.

Purpose

To assess the feasibility of online-delivered MBSR for IBD patients, with feasibility outcomes defined as recruitment success, and attendance, adherence, and attrition of participating patients.

Method

Eligible participants were adult IBD patients aged 18-65 attending gastroenterology clinics in Edmonton, Alberta who self-identified as being anxious or depressed and/or were referred by their gastroenterologist. A research coordinator contacted eligible patients who expressed interest in participating after completing an assessment of symptoms and a semi-structured interview with a psychiatrist. The MBSR protocol was an 8-week group-based intervention aimed at giving participants tools to cope with stress effectively. Participants attended 8 weekly sessions lasting 2.5 hours/week and a one-time weekend session lasting 5 hours. They were also asked to practice every night for 45-60 minutes. Completion of the program required attendance of at least 6 of 8 weekly sessions and the weekend session. Two groups, led by the same team of qualified psychiatrists, started MBSR, with sessions occurring in the evening via Zoom.

Result(s)

Of the 64 patients referred to the study, 16 (25%) agreed to participate. Reasons for declining to participate are shown in Table 1, with 80% indicating they were too busy. Of the 16 patients enrolled, the median age was 36 (range: 18-55), 10 identified as female (62.5%) and 8 had Crohn’s Disease (50%). Attendance, adherence, and attrition data from the first group of 7 participants were recorded. Only 3 (42.8%) successfully completed the program. The participants that completed the program had an attendance rate of 100% and practiced 6 nights a week for an average of 25 minutes a night. A second group with 9 participants is currently ongoing.

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Conclusion(s)

Although interest in a cost-free, virtual stress management resource was relatively high, willingness to enroll in MBSR specifically, was low, largely due to the time commitment. Follow-up interviews with those who enrolled and did not enroll in the intervention are underway to highlight the benefits and barriers to MBSR.

Disclosure of Interest

None Declared

Koala retrovirus load and non-A subtypes are associated with secondary disease among wild northern koalas

Koala Retrovirus (KoRV) has been associated with neoplasia in the vulnerable koala (Phascolarctos cinereus). However, there are conflicting findings regarding its association with secondary disease. We undertook a large-scale assessment of how the different KoRV subtypes and viral load are associated with Chlamydia pecorum infection and a range of disease pathologies in 151 wild koalas admitted for care to Currumbin Wildlife Hospital, Australia. Viral load (KoRV pol copies per ml of plasma) was the best predictor of more disease pathologies than any other KoRV variable. The predicted probability of a koala having disease symptoms increased from 25% to over 85% across the observed range of KoRV load, while the predicted probability of C. pecorum infection increased from 40% to over 80%. We found a negative correlation between the proportion of env deep sequencing reads that were endogenous KoRV-A and total KoRV load. This is consistent with suppression of endogenous KoRV-A, while the exogenous KoRV subtypes obtain high infection levels. Additionally, we reveal evidence that the exogenous subtypes are directly associated with secondary disease, with the proportion of reads that were the endogenous KoRV-A sequence a negative predictor of overall disease probability after the effect of KoRV load was accounted for. Further, koalas that were positive for KoRV-D or KoRV-D/F were more likely to have urogenital C. pecorum infection or low body condition score, respectively, irrespective of KoRV load. By contrast, our findings do not support previous findings that KoRV-B in particular is associated with Chlamydial disease. Based on these findings we suggest that koala research and conservation programs should target understanding what drives individual differences in KoRV load and limiting exogenous subtype diversity within populations, rather than seeking to eliminate any particular subtype.

Systems serology detects functionally distinct coronavirus antibody features in children and elderly

The hallmarks of COVID-19 are higher pathogenicity and mortality in the elderly compared to children. Examining baseline SARS-CoV-2 cross-reactive immunological responses, induced by circulating human coronaviruses (hCoVs), is needed to understand such divergent clinical outcomes. Here we show analysis of coronavirus antibody responses of pre-pandemic healthy children (n = 89), adults (n = 98), elderly (n = 57), and COVID-19 patients (n = 50) by systems serology. Moderate levels of cross-reactive, but non-neutralizing, SARS-CoV-2 antibodies are detected in pre-pandemic healthy individuals. SARS-CoV-2 antigen-specific Fcγ receptor binding accurately distinguishes COVID-19 patients from healthy individuals, suggesting that SARS-CoV-2 infection induces qualitative changes to antibody Fc, enhancing Fcγ receptor engagement. Higher cross-reactive SARS-CoV-2 IgA and IgG are observed in healthy elderly, while healthy children display elevated SARS-CoV-2 IgM, suggesting that children have fewer hCoV exposures, resulting in less-experienced but more polyreactive humoral immunity. Age-dependent analysis of COVID-19 patients, confirms elevated class-switched antibodies in elderly, while children have stronger Fc responses which we demonstrate are functionally different. These insights will inform COVID-19 vaccination strategies, improved serological diagnostics and therapeutics.

IgM ANCA in healthy individuals and in patients with ANCA-associated vasculitis

Low levels of IgM auto-antibodies have been reported in health and disease. IgM anti-neutrophil cytoplasmic antibodies (ANCA) have been reported in patients with ANCA-associated vasculitis (AAV). We sought to investigate if healthy individuals may have IgM ANCA in their sera. The first aim of the study was to determine whether IgM ANCA was present in healthy individuals and in patients with ANCA-associated vasculitis. The second aim was to determine what happens to IgM ANCA levels over time. The third aim was to determine whether bacterial infections affected IgM ANCA levels in non-AAV patients. Sera from healthy individuals and patients with AAV were tested for IgM ANCA by immunofluorescence on fixed neutrophils, immunoprecipitation, Western blot and ELISA. Peripheral blood mononuclear cells were isolated and tested by ELISpot for circulating IgM ANCA B cells. To determine whether infection affected IgM ANCA levels, we studied non-AAV patients with bacterial endocarditis or Staphylococcus aureus bacteraemia and measured IgM ANCA levels over time. IgM ANCA is detectable in both healthy individuals and patients with AAV and the titres decreased with increasing age. Circulating IgM ANCA B cells were identified by ELISpot. In the presence of infection, we could not find a significant change in IgM ANCA levels. We report the presence of low-level specific IgM ANCA in the sera of healthy individuals and in patients with ANCA-associated vasculitis. Bacterial infection did not affect the level of IgM ANCA in this small study.

Bovine Herpesvirus-4-Vectored Delivery of Nipah Virus Glycoproteins Enhances T Cell Immunogenicity in Pigs

Nipah virus (NiV) is an emergent pathogen capable of causing acute respiratory illness and fatal encephalitis in pigs and humans. A high fatality rate and broad host tropism makes NiV a serious public and animal health concern. There is therefore an urgent need for a NiV vaccines to protect animals and humans. In this study we investigated the immunogenicity of bovine herpesvirus (BoHV-4) vectors expressing either NiV attachment (G) or fusion (F) glycoproteins, BoHV-4-A-CMV-NiV-GΔTK or BoHV-4-A-CMV-NiV-FΔTK, respectively in pigs. The vaccines were benchmarked against a canarypox (ALVAC) vector expressing NiV G, previously demonstrated to induce protective immunity in pigs. Both BoHV-4 vectors induced robust antigen-specific antibody responses. BoHV-4-A-CMV-NiV-GΔTK stimulated NiV-neutralizing antibody titers comparable to ALVAC NiV G and greater than those induced by BoHV-4-A-CMV-NiV-FΔTK. In contrast, only BoHV-4-A-CMV-NiV-FΔTK immunized pigs had antibodies capable of significantly neutralizing NiV G and F-mediated cell fusion. All three vectored vaccines evoked antigen-specific CD4 and CD8 T cell responses, which were particularly strong in BoHV-4-A-CMV-NiV-GΔTK immunized pigs and to a lesser extent BoHV-4-A-CMV-NiV-FΔTK. These findings emphasize the potential of BoHV-4 vectors for inducing antibody and cell-mediated immunity in pigs and provide a solid basis for the further evaluation of these vectored NiV vaccine candidates.

An Improved and High Throughput Respiratory Syncytial Virus (RSV) Micro-neutralization Assay

Respiratory syncytial virus-specific neutralizing antibodies (RSV NAbs) are an important marker of protection against RSV. A number of different assay formats are currently in use worldwide so there is a need for an accurate and high-throughput method for measuring RSV NAbs. We describe here an imaging-based micro-neutralization assay that has been tested on RSV subgroup A and can also be adapted for RSV subgroup B and different sample types. This method is highly reproducible, with inter-assay variations for the reference antiserum being less than 10%. We believe this assay can be readily established in many laboratories worldwide at relatively low cost. Development of an improved, high-throughput assay that measures RSV NAbs represents a significant step forward for the standardization of this method internationally as well as being critical for the evaluation of novel RSV vaccine candidates in the future.

Potential tenfold drug overdoses on a neonatal unit

Nearly one third of intravenous drug prescriptions on a neonatal unit were for doses less than one tenth of a single drug vial. Tenfold drug errors in prescribing are well documented and with the continued use of vials containing adult size doses, great potential exists for serious administration errors.

Testing methods for mitigation of tree dieback in Tasmanian dry eucalypt forests and woodlands

Dieback of eucalypts is a widespread phenomenon in subhumid eastern Australian vegetation remnants. It has been shown to have a multifactorial etiology, including drought, vertebrate and invertebrate predation and stock impacts. At three dieback sites in subhumid Tasmania experimental plots were established in the period 1996?1998 to test the single and interactive effects of possum exclusion, watering and stock exclusion on the health of trees, and to determine the influence of fencing on soil bulk density and eucalypt regeneration. At two sites the exclusion of possums mitigated dieback over the two year measurement period, although at one site the trees continued to deteriorate. At the third site there was no impact of any of the treatments, and changes in health over the experimental period related to tree size, indicating a self-thinning process. Soil penetration resistance decreased in the fenced treatment at all sites, and eucalypt regeneration was encouraged by fencing at two sites. Although the results of the experiment are not consistent with moisture deficiencies as a causal factor in dieback, this may relate either to a lack of severe drought during the measurement period, which followed a decade of such drought, or to the magnitude and/or application method of the watering. The results of the experiment indicate that, at some sites, the exclusion of possums will improve tree health, and that the exclusion of stock can improve tree regeneration and soil conditions.