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2.
Microbiol Spectr ; 10(3): e0113422, 2022 06 29.
Article in English | MEDLINE | ID: covidwho-1874515

ABSTRACT

Our group has previously used laboratory and commercially developed assays to understand the IgG responses to SARS-CoV-2 antigens, including nucleocapsid (N), spike (S), and receptor binding domain (RBD), in Canadian blood donors. In this current study, we analyzed 17,428 available and previously characterized retention samples collected from April 2020 to March 2021. The analysis compared the characteristics of the Abbott SARS-CoV-2 IgG II Quant assay (Abbott anti-spike [S], Abbott, Chicago, IL) against four other IgG assays. The Abbott anti-S assay has a qualitative threshold of 50 AU/mL. The four comparator assays were the Abbott anti-nucleocapsid (N) assay and three commonly used Canadian in-house IgG enzyme-linked immunosorbent assays (ELISAs) recognizing distinct recombinant viral antigens, full-length spike glycoprotein, glycoprotein RBD, and nucleocapsid. The strongest qualitative relationship was between Sinai RBD and the Abbott anti-S assay (kappa, 0.707; standard error [SE] of kappa, 0.018; 95% confidence interval, 0.671 to 0.743). We then scored each previously characterized specimen as positive when two anti-SARS-COV-2 assays identified anti-SARS-CoV-2 IgG in the specimen. Using this composite reference standard approach, the sensitivity of the Abbott anti-S assay was 95.96% (95% confidence interval [CI], 93.27 to 97.63%). The specificity of the Abbott anti-S assay was 99.35% (95% CI, 99.21 to 99.46%). Our study provides context on the use of commonly used SARS-CoV-2 serologies in Canada and identifies how these assays qualitatively compare to newer commercial assays. Our next steps are to assess how well the Abbott anti-S assays quantitatively detect wild-type and SARS-CoV-2 variants of concern. IMPORTANCE We describe the qualitative test characteristics of the Abbott SARS-CoV-2 IgG II Quant assay against four other anti-SARS-CoV-2 IgG assays commonly used in Canada. Although there is no gold standard for identifying anti-SARS-CoV-2 seropositivity, aggregate standards can be used to assess seropositivity. In this study, we used a specimen bank of previously well-characterized specimens collected between April 2020 and March 2021. The Abbott anti-S assay showed the strongest qualitative relationship with a widely used laboratory-developed IgG assay for the SARS-CoV-2 receptor binding domain. Using the composite reference standard approach, we also showed that the Abbott anti-S assay was highly sensitive and specific. As new anti-SARS-CoV-2 assays are developed, it is important to compare their test characteristics against other assays that have been extensively used in prior research.


Subject(s)
COVID-19 , SARS-CoV-2 , Antibodies, Viral , Blood Donors , COVID-19/diagnosis , Canada , Enzyme-Linked Immunosorbent Assay , Humans , Immunoglobulin G , Sensitivity and Specificity
3.
JCI Insight ; 7(11)2022 06 08.
Article in English | MEDLINE | ID: covidwho-1807768

ABSTRACT

BACKGROUNDLimited information is available on the impact of immunosuppressants on COVID-19 vaccination in patients with immune-mediated inflammatory diseases (IMID).METHODSThis observational cohort study examined the immunogenicity of SARS-CoV-2 mRNA vaccines in adult patients with inflammatory bowel disease, rheumatoid arthritis, ankylosing spondylitis, or psoriatic disease, with or without maintenance immunosuppressive therapies. Ab and T cell responses to SARS-CoV-2, including neutralization against SARS-CoV-2 variants, were determined before and after 1 and 2 vaccine doses.RESULTSWe prospectively followed 150 subjects, 26 healthy controls, 9 patients with IMID on no treatment, 44 on anti-TNF, 16 on anti-TNF with methotrexate/azathioprine (MTX/AZA), 10 on anti-IL-23, 28 on anti-IL-12/23, 9 on anti-IL-17, and 8 on MTX/AZA. Ab and T cell responses to SARS-CoV-2 were detected in all participants, increasing from dose 1 to dose 2 and declining 3 months later, with greater attrition in patients with IMID compared with healthy controls. Ab levels and neutralization efficacy against variants of concern were substantially lower in anti-TNF-treated patients than in healthy controls and were undetectable against Omicron by 3 months after dose 2.CONCLUSIONSOur findings support the need for a third dose of the mRNA vaccine and for continued monitoring of immunity in these patient groups.FUNDINGFunded by a donation from Juan and Stefania Speck and by Canadian Institutes of Health (CIHR)/COVID-Immunity Task Force (CITF) grants VR-1 172711 and VS1-175545 (to THW and ACG), CIHR FDN-143250 (to THW), GA2-177716 (to VC, ACG, and THW), and GA1-177703 (to ACG) and the CIHR rapid response network to SARS-CoV-2 variants, CoVaRR-Net (to ACG).


Subject(s)
COVID-19 Vaccines , COVID-19 , Antibodies, Viral , BNT162 Vaccine , COVID-19/prevention & control , Canada , Humans , SARS-CoV-2 , Tumor Necrosis Factor Inhibitors , Vaccines, Synthetic , mRNA Vaccines
4.
Mucosal Immunol ; 15(5): 799-808, 2022 May.
Article in English | MEDLINE | ID: covidwho-1805590

ABSTRACT

Although SARS-CoV-2 infects the upper respiratory tract, we know little about the amount, type, and kinetics of antibodies (Ab) generated in the oral cavity in response to COVID-19 vaccination. We collected serum and saliva samples from participants receiving two doses of mRNA COVID-19 vaccines and measured the level of anti-SARS-CoV-2 Ab. We detected anti-Spike and anti-Receptor Binding Domain (RBD) IgG and IgA, as well as anti-Spike/RBD associated secretory component in the saliva of most participants after dose 1. Administration of a second dose of mRNA boosted the IgG but not the IgA response, with only 30% of participants remaining positive for IgA at this timepoint. At 6 months post-dose 2, these participants exhibited diminished anti-Spike/RBD IgG levels, although secretory component-associated anti-Spike Ab were more stable. Examining two prospective cohorts we found that participants who experienced breakthrough infections with SARS-CoV-2 variants had lower levels of vaccine-induced serum anti-Spike/RBD IgA at 2-4 weeks post-dose 2 compared to participants who did not experience an infection, whereas IgG levels were comparable between groups. These data suggest that COVID-19 vaccines that elicit a durable IgA response may have utility in preventing infection. Our study finds that a local secretory component-associated IgA response is induced by COVID-19 mRNA vaccination that persists in some, but not all participants. The serum and saliva IgA response modestly correlate at 2-4 weeks post-dose 2. Of note, levels of anti-Spike serum IgA (but not IgG) at this timepoint are lower in participants who subsequently become infected with SARS-CoV-2. As new surges of SARS-CoV-2 variants arise, developing COVID-19 booster shots that provoke high levels of IgA has the potential to reduce person-to-person transmission.

5.
Clin Transl Immunology ; 11(3): e1380, 2022.
Article in English | MEDLINE | ID: covidwho-1750347

ABSTRACT

Objectives: Antibody testing against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been instrumental in detecting previous exposures and analyzing vaccine-elicited immune responses. Here, we describe a scalable solution to detect and quantify SARS-CoV-2 antibodies, discriminate between natural infection- and vaccination-induced responses, and assess antibody-mediated inhibition of the spike-angiotensin converting enzyme 2 (ACE2) interaction. Methods: We developed methods and reagents to detect SARS-CoV-2 antibodies by enzyme-linked immunosorbent assay (ELISA). The main assays focus on the parallel detection of immunoglobulin (Ig)Gs against the spike trimer, its receptor binding domain (RBD) and nucleocapsid (N). We automated a surrogate neutralisation (sn)ELISA that measures inhibition of ACE2-spike or -RBD interactions by antibodies. The assays were calibrated to a World Health Organization reference standard. Results: Our single-point IgG-based ELISAs accurately distinguished non-infected and infected individuals. For seroprevalence assessment (in a non-vaccinated cohort), classifying a sample as positive if antibodies were detected for ≥ 2 of the 3 antigens provided the highest specificity. In vaccinated cohorts, increases in anti-spike and -RBD (but not -N) antibodies are observed. We present detailed protocols for serum/plasma or dried blood spots analysis performed manually and on automated platforms. The snELISA can be performed automatically at single points, increasing its scalability. Conclusions: Measuring antibodies to three viral antigens and identify neutralising antibodies capable of disrupting spike-ACE2 interactions in high-throughput enables large-scale analyses of humoral immune responses to SARS-CoV-2 infection and vaccination. The reagents are available to enable scaling up of standardised serological assays, permitting inter-laboratory data comparison and aggregation.

6.
Microbiol Spectr ; 10(1): e0256321, 2022 02 23.
Article in English | MEDLINE | ID: covidwho-1700249

ABSTRACT

We have previously used composite reference standards and latent class analysis (LCA) to evaluate the performance of laboratory assays in the presence of tarnished gold standards. Here, we apply these techniques to repeated, cross-sectional study of Canadian blood donors, whose sera underwent parallel testing with four separate SARS-CoV-2 antibody assays. We designed a repeated cross-sectional design with random cross-sectional sampling of all available retention samples (n = 1500/month) for a 12 -month period from April 2020 until March 2021. Each sample was evaluated for SARS-CoV-2 IgG antibodies using four assays an Abbott Architect assay targeting the nucleocapsid antigen (Abbott-NP, Abbott, Chicago IL) and three in-house IgG ELISAs recognizing distinct recombinant viral antigens: full-length spike glycoprotein (Spike), spike glycoprotein receptor binding domain (RBD) and nucleocapsid (NP). We used two analytic approaches to estimate SAR-CoV-2 seroprevalence: a composite reference standard and LCA. Using LCA to estimate true seropositivity status based on the results of the four antibody tests, we estimated that seroprevalence increased from 0.8% (95% CI: 0.5-1.4%) in April 2020 to 6.3% (95% CI: 5.1-7.6%) in March 2021. Our study provides further support for the use of LCA in upcoming public health crises, epidemics, and pandemics when a gold standard assay may not be available or identifiable. IMPORTANCE Here, we describe an approach to estimating seroprevalence in a low prevalence setting when multiple assays are available and yet no known gold standard exists. Because serological studies identify cases through both diagnostic testing and surveillance, and otherwise silent, unrecognized infections, serological data can be used to estimate the true infection fatality ratio of a disease. However, seroprevalence studies rely on assays with imperfect sensitivity and specificity. Seroreversion (loss of antibody response) also occurs over time, and with the advent of vaccination, distinction of antibody response resulting from vaccination as opposed to antibody response due to infection has posed an additional challenge. Our approach indicates that seroprevalence on Canadian blood donors by the end of March 2021was less than 10%. Our study supports the use of latent class analysis in upcoming public health crises, epidemics, and pandemics when a gold standard assay may not be available or identifiable.


Subject(s)
Antibodies, Viral/blood , Blood Donors/statistics & numerical data , COVID-19/blood , SARS-CoV-2/immunology , Adult , Aged , COVID-19/epidemiology , COVID-19/virology , Canada/epidemiology , Coronavirus Nucleocapsid Proteins/analysis , Coronavirus Nucleocapsid Proteins/immunology , Cross-Sectional Studies , Enzyme-Linked Immunosorbent Assay , Female , Humans , Male , Middle Aged , SARS-CoV-2/genetics , Seroepidemiologic Studies , Spike Glycoprotein, Coronavirus/analysis , Spike Glycoprotein, Coronavirus/immunology , Young Adult
7.
JAMA Netw Open ; 5(2): e2146798, 2022 02 01.
Article in English | MEDLINE | ID: covidwho-1694847

ABSTRACT

Importance: The incidence of infection during SARS-CoV-2 viral waves, the factors associated with infection, and the durability of antibody responses to infection among Canadian adults remain undocumented. Objective: To assess the cumulative incidence of SARS-CoV-2 infection during the first 2 viral waves in Canada by measuring seropositivity among adults. Design, Setting, and Participants: The Action to Beat Coronavirus study conducted 2 rounds of an online survey about COVID-19 experience and analyzed immunoglobulin G levels based on participant-collected dried blood spots (DBS) to assess the cumulative incidence of SARS-CoV-2 infection during the first and second viral waves in Canada. A sample of 19 994 Canadian adults (aged ≥18 years) was recruited from established members of the Angus Reid Forum, a public polling organization. The study comprised 2 phases (phase 1 from May 1 to September 30, 2020, and phase 2 from December 1, 2020, to March 31, 2021) that generally corresponded to the first (April 1 to July 31, 2020) and second (October 1, 2020, to March 1, 2021) viral waves. Main Outcomes and Measures: SARS-CoV-2 immunoglobulin G seropositivity (using a chemiluminescence assay) by major geographic and demographic variables and correlation with COVID-19 symptom reporting. Results: Among 19 994 adults who completed the online questionnaire in phase 1, the mean (SD) age was 50.9 (15.4) years, and 10 522 participants (51.9%) were female; 2948 participants (14.5%) had self-identified racial and ethnic minority group status, and 1578 participants (8.2%) were self-identified Indigenous Canadians. Among participants in phase 1, 8967 had DBS testing. In phase 2, 14 621 adults completed online questionnaires, and 7102 of those had DBS testing. Of 19 994 adults who completed the online survey in phase 1, fewer had an educational level of some college or less (4747 individuals [33.1%]) compared with the general population in Canada (45.0%). Survey respondents were otherwise representative of the general population, including in prevalence of known risk factors associated with SARS-CoV-2 infection. The cumulative incidence of SARS-CoV-2 infection among unvaccinated adults increased from 1.9% in phase 1 to 6.5% in phase 2. The seropositivity pattern was demographically and geographically heterogeneous during phase 1 but more homogeneous by phase 2 (with a cumulative incidence ranging from 6.4% to 7.0% in most regions). The exception was the Atlantic region, in which cumulative incidence reached only 3.3% (odds ratio [OR] vs Ontario, 0.46; 95% CI, 0.21-1.02). A total of 47 of 188 adults (25.3%) reporting COVID-19 symptoms during phase 2 were seropositive, and the OR of seropositivity for COVID-19 symptoms was 6.15 (95% CI, 2.02-18.69). In phase 2, 94 of 444 seropositive adults (22.2%) reported having no symptoms. Of 134 seropositive adults in phase 1 who were retested in phase 2, 111 individuals (81.8%) remained seropositive. Participants who had a history of diabetes (OR, 0.58; 95% CI, 0.38-0.90) had lower odds of having detectable antibodies in phase 2. Conclusions and Relevance: The Action to Beat Coronavirus study found that the incidence of SARS-CoV-2 infection in Canada was modest until March 2021, and this incidence was lower than the levels of population immunity required to substantially reduce transmission of the virus. Ongoing vaccination efforts remain central to reducing viral transmission and mortality. Assessment of future infection-induced and vaccine-induced immunity is practicable through the use of serial online surveys and participant-collected DBS.


Subject(s)
COVID-19 Serological Testing/statistics & numerical data , COVID-19/epidemiology , Immunoglobulin G/blood , Adolescent , Adult , Aged , COVID-19/immunology , Canada/epidemiology , Female , Humans , Incidence , Male , Middle Aged , Pandemics , SARS-CoV-2 , Surveys and Questionnaires
8.
Microbiol Spectr ; 10(1): e0226221, 2022 02 23.
Article in English | MEDLINE | ID: covidwho-1691401

ABSTRACT

This study attempted to understand the levels of neutralizing titers and the breadth of antibody protection against wild-type and variant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Canadian blood donors during the first 3 months of 2021. During this period, it is unlikely that many of the blood donors had received a second dose, since vaccine rollout had not yet ramped up, and less than 2% of the Canadian population had received a second dose of vaccine. A repeated cross-sectional design was used. A random cross-sectional sampling of all available Canadian Blood Services retention samples (n = 1,500/month) was drawn monthly for January, February, and March 2021. A tiered testing approach analyzed 4,500 Canadian blood donor specimens for potential evidence of a signal for anti-spike (anti-S), anti-receptor-binding domain (anti-RBD), and anti-nucleocapsid protein (anti-N). Specimens were stratified based on donor-declared vaccination history and then stratified on the presence or absence of anti-N as follows: (i) "vaccinated plus anti-N" (n = 5), (ii) "vaccinated and no anti-N" (n = 20), (iii) "unvaccinated plus anti-N" (n = 20), and (iv) "unvaccinated and no anti-N" (n = 20). Randomized specimens were then characterized for neutralizing capacity against wild-type as well as SARS-CoV-2 variants of concern (VOCs) (Alpha [B.1.1.7], Beta [B.1.351], Gamma [P.1], and Delta [B.1.617.2]) using S-pseudotyped virus-like particle (VLP) neutralization assays. There was no neutralizing capacity against wild-type and VOC VLPs within the "no vaccine and no anti-N" group. Neutralization of Beta VLPs was less than wild-type VLPs within "vaccinated plus anti-N," "vaccinated and no anti-N", and "unvaccinated plus anti-N" groups. IMPORTANCE In the first 3 months of 2021 as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination was in the initial stages of a mass rollout, Canadian blood donors had various levels of humoral protection against wild-type and variant of concern (VOC) SARS-CoV-2. Very few Canadians would have received a second dose of a SARS-CoV-2 vaccine. In this study, we identified elevated levels of neutralizing capacity, albeit with reduced neutralization capacity against one or more SARS-CoV-2 strains (wild type and VOCs) in vaccinated blood donors. This broad neutralizing response we present regardless of evidence of natural SARS-CoV-2 infection. Neutralizing capacity against wild type and VOCs varied significantly within the unvaccinated group, with one subset of unvaccinated plasma specimens (unvaccinated and no anti-N) having no measurable wild type- nor variant-neutralizing capacity. The study is important because it indicates that vaccination can be associated with a broad neutralizing antibody capacity of donor plasma against SARS-CoV-2 VOCs.


Subject(s)
Antibodies, Viral/blood , Blood Donors/statistics & numerical data , COVID-19/blood , SARS-CoV-2/immunology , Adolescent , Adult , Aged , Aged, 80 and over , Antibodies, Neutralizing/blood , COVID-19/prevention & control , COVID-19/virology , COVID-19 Vaccines/administration & dosage , Canada , Cross-Sectional Studies , Female , Humans , Male , Middle Aged , Neutralization Tests , SARS-CoV-2/genetics , Vaccination , Young Adult
9.
EuropePMC;
Preprint in English | EuropePMC | ID: ppcovidwho-327181

ABSTRACT

Background: Limited information is available on the impact of immunosuppressants on COVID-19 vaccination in patients with immune-mediated inflammatory diseases (IMID). This study investigated antibody and T cell responses to SARS-CoV-2 mRNA vaccines in IMID patients undergoing immunomodulatory maintenance therapy. Methods This observational cohort study examined the immunogenicity of SARS-CoV-2 mRNA vaccines in adult patients with inflammatory bowel disease, rheumatoid arthritis, ankylosing spondylitis or psoriatic disease, with or without maintenance immunosuppressive therapies. T cell and antibody responses to SARS-COV-2, including neutralization against SARS-CoV-2 variants were determined pre-vaccination and after 1 and 2 vaccine doses. Findings We prospectively followed 150 subjects, 26 healthy controls, 9 IMID patients on no treatment, 44 on anti-TNF, 16 on anti-TNF with methotrexate/azathioprine (MTX/AZA), 10 on anti-IL-23, 28 on anti-IL-12/23, 9 on anti-IL-17, and 8 on MTX/AZA. Most patients showed increased antibody responses from dose 1 to dose 2, with decreases apparent by 3 months post dose 2, albeit with considerable variability within groups. Overall, T cell responses were not consistently different between groups;however, antibody levels and neutralization efficacy in the anti-TNF treated group was lower than controls and waned substantially by 3 months post-dose 2. Implications These findings support the need for a third dose of mRNA vaccine and for continued monitoring of immunity over time.

10.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-322524

ABSTRACT

Background: The prevalence of infection in Canada’s COVID-19 viral waves, the predictors of infection, and the durability of antibody responses to infection remain undocumented.Methods: We organized serial online surveys of a representative group of Canadian adults about their COVID experience in the first (n=19 994;April-July 2020) and second viral wave (n=14 621;October 2020-March 2021). We paired these with IgG analysis of SARS-CoV-2 seroprevalence in self-collected dried blood spots after the first (n=8967) and second (n=7102) waves.Findings: Canada’s cumulative seroprevalence of SARS-CoV-2 among unvaccinated adults rose from ~2% after the first wave to 7% after the second. The seropositivity pattern was heterogeneous demographically and geographically during the first wave, but more homogeneous by the second (except in the four Atlantic Provinces, cumulative seroprevalence ~3%). Seroprevalence among visible minorities rose sharply from about 2% to >8% from the first to second wave. About a quarter of those reporting COVID symptoms during the second wave were seropositive, and in both waves the odds ratio (OR) of seropositivity for COVID symptoms exceeded six. About one-fifth of seropositives reported no symptoms. Of 134 seropositive adults in the first wave who were retested after the second, 83% (111) remained seropositive at least seven months later. Current smokers and people with a history of diabetes had lower ORs of infection. We calculated the absolute numbers of seropositive adults nationwide, which nearly quadrupled from 0.57 million to 1.90 million, with the largest increases among older adults. Infection fatality rates fell from 3.7 to 2.6/1000 infections, most notably at older ages.Interpretation: Canada’s COVID pandemic grew substantially between the first and second viral waves. Home-based DBS collection offers a practicable way to document evolving demographic and geographic patterns and to assess the levels and durability of population immunity, including from SARS-CoV-2 vaccination.Funding: Pfizer Global Medical, Unity Health Foundation, and the Canadian COVID-19 Immunity Task Force. Declaration of Interest: None to declare. Ethical Approval: The Ab-C study was approved by the Unity Health Toronto Ethics Review Board.

11.
J Immunol ; 208(2): 429-443, 2022 01 15.
Article in English | MEDLINE | ID: covidwho-1674944

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces T cell, B cell, and Ab responses that are detected for several months in recovered individuals. Whether this response resembles a typical respiratory viral infection is a matter of debate. In this study, we followed T cell and Ab responses in 24 mainly nonhospitalized human subjects who had recovered from PCR-confirmed SARS-CoV-2 infection at two time points (median of 45 and 145 d after symptom onset). Ab responses were detected in 95% of subjects, with a strong correlation between plasma and salivary anti-spike (anti-S) and anti-receptor binding domain IgG, as well as a correlation between circulating T follicular helper cells and the SARS-CoV-2-specific IgG response. T cell responses to SARS-CoV-2 peptides were determined using intracellular cytokine staining, activation markers, proliferation, and cytokine secretion. All study subjects had a T cell response to at least one SARS-CoV-2 Ag based on at least one T cell assay. CD4+ responses were largely of the Th1 phenotype, but with a lower ratio of IFN-γ- to IL-2-producing cells and a lower frequency of CD8+:CD4+ T cells than in influenza A virus (IAV)-specific memory responses within the same subjects. Analysis of secreted molecules also revealed a lower ratio of IFN-γ to IL-2 and an altered cytotoxic profile for SARS-CoV-2 S- and nucleocapsid-specific responses compared with IAV-specific responses. These data suggest that the memory T cell phenotype after a single infection with SARS-CoV-2 persists over time, with an altered cytokine and cytotoxicity profile compared with long-term memory to whole IAV within the same subjects.


Subject(s)
Antibody Formation , COVID-19/immunology , Immunity, Cellular , Immunoglobulin G/immunology , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/immunology , Th1 Cells/immunology , Adult , Aged , Female , Humans , Male , Middle Aged , Time Factors
12.
Sci Adv ; 8(3): eabj9815, 2022 Jan 21.
Article in English | MEDLINE | ID: covidwho-1634773

ABSTRACT

Safe and effective vaccines are needed to end the COVID-19 pandemic. Here, we report the preclinical development of a lipid nanoparticle­formulated SARS-CoV-2 mRNA vaccine, PTX-COVID19-B. PTX-COVID19-B was chosen among three candidates after the initial mouse vaccination results showed that it elicited the strongest neutralizing antibody response against SARS-CoV-2. Further tests in mice and hamsters indicated that PTX-COVID19-B induced robust humoral and cellular immune responses and completely protected the vaccinated animals from SARS-CoV-2 infection in the lung. Studies in hamsters also showed that PTX-COVID19-B protected the upper respiratory tract from SARS-CoV-2 infection. Mouse immune sera elicited by PTX-COVID19-B vaccination were able to neutralize SARS-CoV-2 variants of concern, including the Alpha, Beta, Gamma, and Delta lineages. No adverse effects were induced by PTX-COVID19-B in either mice or hamsters. Based on these results, PTX-COVID19-B was authorized by Health Canada to enter clinical trials in December 2020 with a phase 2 clinical trial ongoing.


Subject(s)
COVID-19 Vaccines/immunology , COVID-19/prevention & control , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/immunology , Vaccines, Synthetic/immunology , /immunology , Animals , Antibodies, Neutralizing/blood , Antibodies, Viral/blood , CD4 Lymphocyte Count , CD8-Positive T-Lymphocytes/immunology , COVID-19/immunology , COVID-19 Vaccines/adverse effects , Canada , Cell Line , Cricetinae , Drug Evaluation, Preclinical , Female , HEK293 Cells , Humans , Immunity, Cellular/immunology , Immunity, Humoral/immunology , Liposomes/pharmacology , Male , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Nanoparticles , Spike Glycoprotein, Coronavirus/genetics , Th1 Cells/immunology
13.
Transfusion ; 62(2): 418-428, 2022 02.
Article in English | MEDLINE | ID: covidwho-1571123

ABSTRACT

BACKGROUND: Randomized clinical trial data show that early plasma transfusion may save lives among trauma patients. Supplying plasma in remote environments is logistically challenging. Freeze-dried plasma (FDP) offers a possible solution. STUDY DESIGN AND METHODS: A Terumo BCT plasma freeze-drying system was evaluated. We compared pooled frozen plasma (FP) units with derived Terumo BCT FDP (TFDP) units and pooled COVID-19 convalescent apheresis fresh-frozen plasma (CC-AFFP) with derived CC-TFDP units. Parameters measured were: coagulation factors (F) II; V; VII; VIII; IX; XI; XIII; fibrinogen; Proteins C (PC) and S (PS); antithrombin (AT); α2 -antiplasmin (α2 AP); ADAMTS13; von Willebrand Factor (vWF); thrombin-antithrombin (TAT); D-dimer; activated complement factors 3 (C3a) and 5 (C5a); pH; osmolality; prothrombin time (PT); and activated partial thromboplastin time (aPTT). Antibodies to SARS-CoV-2 in CC-AFFP and CC-TFDP units were compared by plaque reduction assays and viral protein immunoassays. RESULTS: Most parameters were unchanged in TFDP versus FP or differed ≤15%. Mean aPTT, PT, C3a, and pH were elevated 5.9%, 6.9%, 64%, and 0.28 units, respectively, versus FP. CC-TFDP showed no loss of SARS-CoV-2 neutralization titer versus CC-AFFP and no mean signal loss in most pools by viral protein immunoassays. CONCLUSION: Changes in protein activities or clotting times arising from freeze-drying were <15%. Although C3a levels in TFDP were elevated, they were less than literature values for transfusable plasma. SARS-CoV-2-neutralizing antibody titers and viral protein binding levels were largely unaffected by freeze-drying. In vitro characteristics of TFDP or CC-TFDP were comparable to their originating plasma, making future clinical studies appropriate.


Subject(s)
Blood Component Removal , Blood Component Transfusion , COVID-19 , Freeze Drying , Antithrombins , COVID-19/therapy , Canada , Hemostatics , Humans , Immunization, Passive , Plasma , SARS-CoV-2 , Viral Proteins
14.
Transfusion ; 62(1): 37-43, 2022 01.
Article in English | MEDLINE | ID: covidwho-1470483

ABSTRACT

BACKGROUND: This pilot study assesses the ability of plasma collected from Canadian blood donors in the first wave of the SARS-CoV-2 pandemic to neutralize later SARS-CoV-2 variants of concern (VOCs). STUDY DESIGN AND METHODS: A repeated cross-sectional design was used, and a random cross-sectional sample of all available Canadian Blood Services retention samples (n = 1500/month) was drawn monthly for April and May of 2020. Qualitative IgG analysis was performed on aliquots of specimens using anti-spike, anti-receptor binding domain, and anti-nucleocapsid protein enzyme-linked immunosorbent assays as well as the Abbott Architect SARS CoV-2 IgG assay (Abbott Laboratories) against the anti-nucleocapsid protein. Selected plasma specimens were then assessed for neutralization against VOCs using pseudotyped lentivirus inhibition assays as well as plaque reduction neutralization test 50% (PRNT50 ). RESULTS: Six specimens with a high neutralizing titer against wild-type SARS-CoV-2 and three specimens with a low neutralizing titer against wild-type SARS-CoV-2 were chosen for further analysis against VOCs. Four of six high neutralizing titer specimens had a reduced neutralizing capacity against beta VOCs by both neutralization methods. Three of six high neutralizing titer specimens had reduced neutralization capacity against gamma VOCs. CONCLUSIONS: This preliminary data can be used as a justification for limiting the use of first wave plasma products in upcoming clinical trials but cannot be used to speculate on general trends in the immunity of Canadian blood donors to SARS-CoV-2.


Subject(s)
Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , Blood Donors , COVID-19 , SARS-CoV-2 , COVID-19/therapy , Canada , Cross-Sectional Studies , Humans , Immunization, Passive , Immunoglobulin G/immunology , Neutralization Tests , Pilot Projects , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus
15.
PLoS One ; 16(9): e0257743, 2021.
Article in English | MEDLINE | ID: covidwho-1435621

ABSTRACT

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence studies bridge the gap left from case detection, to estimate the true burden of the COVID-19 pandemic. While multiple anti-SARS-CoV-2 immunoassays are available, no gold standard exists. METHODS: This serial cross-sectional study was conducted using plasma samples from 8999 healthy blood donors between April-September 2020. Each sample was tested by four assays: Abbott SARS-Cov-2 IgG assay, targeting nucleocapsid (Abbott-NP) and three in-house IgG ELISA assays (targeting spike glycoprotein, receptor binding domain, and nucleocapsid). Seroprevalence rates were compared using multiple composite reference standards and by a series of Bayesian Latent Class Models. RESULT: We found 13 unique diagnostic phenotypes; only 32 samples (0.4%) were positive by all assays. None of the individual assays resulted in seroprevalence increasing monotonically over time. In contrast, by using the results from all assays, the Bayesian Latent Class Model with informative priors predicted seroprevalence increased from 0.7% (95% credible interval (95% CrI); 0.4, 1.0%) in April/May to 0.7% (95% CrI 0.5, 1.1%) in June/July to 0.9% (95% CrI 0.5, 1.3) in August/September. Assay characteristics varied over time. Overall Spike had the highest sensitivity (93.5% (95% CrI 88.7, 97.3%), while the sensitivity of the Abbott-NP assay waned from 77.3% (95% CrI 58.7, 92.5%) in April/May to 64.4% (95% CrI 45.6, 83.0) by August/September. DISCUSSION: Our results confirmed very low seroprevalence after the first wave in Canada. Given the dynamic nature of this pandemic, Bayesian Latent Class Models can be used to correct for imperfect test characteristics and waning IgG antibody signals.


Subject(s)
COVID-19/immunology , SARS-CoV-2/immunology , Adult , Aged , Antibodies, Viral/immunology , Bayes Theorem , Blood Donors , Canada , Cross-Sectional Studies , Female , Humans , Immunoglobulin G/immunology , Male , Middle Aged , Nucleocapsid/immunology , Pandemics/prevention & control , Sensitivity and Specificity , Seroepidemiologic Studies , Spike Glycoprotein, Coronavirus/immunology , Young Adult
17.
J Immunol ; 206(1): 37-50, 2021 01 01.
Article in English | MEDLINE | ID: covidwho-934539

ABSTRACT

There is a pressing need for an in-depth understanding of immunity to SARS-CoV-2. In this study, we investigated human T cell recall responses to fully glycosylated spike trimer, recombinant N protein, as well as to S, N, M, and E peptide pools in the early convalescent phase and compared them with influenza-specific memory responses from the same donors. All subjects showed SARS-CoV-2-specific T cell responses to at least one Ag. Both SARS-CoV-2-specific and influenza-specific CD4+ T cell responses were predominantly of the central memory phenotype; however SARS-CoV-2-specific CD4+ T cells exhibited a lower IFN-γ to TNF ratio compared with influenza-specific memory responses from the same donors, independent of disease severity. SARS-CoV-2-specific T cells were less multifunctional than influenza-specific T cells, particularly in severe cases, potentially suggesting exhaustion. Most SARS-CoV-2-convalescent subjects also produced IFN-γ in response to seasonal OC43 S protein. We observed granzyme B+/IFN-γ+, CD4+, and CD8+ proliferative responses to peptide pools in most individuals, with CD4+ T cell responses predominating over CD8+ T cell responses. Peripheral T follicular helper (pTfh) responses to S or N strongly correlated with serum neutralization assays as well as receptor binding domain-specific IgA; however, the frequency of pTfh responses to SARS-CoV-2 was lower than the frequency of pTfh responses to influenza virus. Overall, T cell responses to SARS-CoV-2 are robust; however, CD4+ Th1 responses predominate over CD8+ T cell responses, have a more inflammatory profile, and have a weaker pTfh response than the response to influenza virus within the same donors, potentially contributing to COVID-19 disease.


Subject(s)
Antigens, Viral/immunology , CD4-Positive T-Lymphocytes/immunology , Inflammation/immunology , Orthomyxoviridae/immunology , SARS-CoV-2/immunology , Adult , Aged , Female , Humans , Male , Middle Aged
18.
Sci Immunol ; 5(52)2020 10 08.
Article in English | MEDLINE | ID: covidwho-842548

ABSTRACT

While the antibody response to SARS-CoV-2 has been extensively studied in blood, relatively little is known about the antibody response in saliva and its relationship to systemic antibody levels. Here, we profiled by enzyme-linked immunosorbent assays (ELISAs) IgG, IgA and IgM responses to the SARS-CoV-2 spike protein (full length trimer) and its receptor-binding domain (RBD) in serum and saliva of acute and convalescent patients with laboratory-diagnosed COVID-19 ranging from 3-115 days post-symptom onset (PSO), compared to negative controls. Anti-SARS-CoV-2 antibody responses were readily detected in serum and saliva, with peak IgG levels attained by 16-30 days PSO. Longitudinal analysis revealed that anti-SARS-CoV-2 IgA and IgM antibodies rapidly decayed, while IgG antibodies remained relatively stable up to 105 days PSO in both biofluids. Lastly, IgG, IgM and to a lesser extent IgA responses to spike and RBD in the serum positively correlated with matched saliva samples. This study confirms that serum and saliva IgG antibodies to SARS-CoV-2 are maintained in the majority of COVID-19 patients for at least 3 months PSO. IgG responses in saliva may serve as a surrogate measure of systemic immunity to SARS-CoV-2 based on their correlation with serum IgG responses.


Subject(s)
Antibodies, Viral/blood , Antigens, Viral/immunology , Betacoronavirus/immunology , Coronavirus Infections/immunology , Pneumonia, Viral/immunology , Saliva/immunology , Spike Glycoprotein, Coronavirus/immunology , Adult , COVID-19 , Coronavirus Infections/virology , Cross-Sectional Studies , Enzyme-Linked Immunosorbent Assay , Female , Humans , Immunoglobulin A/blood , Immunoglobulin A/immunology , Immunoglobulin G/blood , Immunoglobulin G/immunology , Immunoglobulin M/blood , Immunoglobulin M/immunology , Longitudinal Studies , Male , Middle Aged , Pandemics , Pneumonia, Viral/virology , SARS-CoV-2
19.
JCI Insight ; 5(19)2020 10 02.
Article in English | MEDLINE | ID: covidwho-737501

ABSTRACT

Most of the patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mount a humoral immune response to the virus within a few weeks of infection, but the duration of this response and how it correlates with clinical outcomes has not been completely characterized. Of particular importance is the identification of immune correlates of infection that would support public health decision-making on treatment approaches, vaccination strategies, and convalescent plasma therapy. While ELISA-based assays to detect and quantitate antibodies to SARS-CoV-2 in patient samples have been developed, the detection of neutralizing antibodies typically requires more demanding cell-based viral assays. Here, we present a safe and efficient protein-based assay for the detection of serum and plasma antibodies that block the interaction of the SARS-CoV-2 spike protein receptor binding domain (RBD) with its receptor, angiotensin-converting enzyme 2 (ACE2). The assay serves as a surrogate neutralization assay and is performed on the same platform and in parallel with an ELISA for the detection of antibodies against the RBD, enabling a direct comparison. The results obtained with our assay correlate with those of 2 viral-based assays, a plaque reduction neutralization test (PRNT) that uses live SARS-CoV-2 virus and a spike pseudotyped viral vector-based assay.


Subject(s)
Antibodies, Neutralizing/immunology , Coronavirus Infections/immunology , Coronavirus Infections/therapy , Pneumonia, Viral/immunology , Pneumonia, Viral/therapy , Spike Glycoprotein, Coronavirus/immunology , Antibodies, Viral/blood , Area Under Curve , COVID-19 , Enzyme-Linked Immunosorbent Assay , Humans , Immunization, Passive/methods , Neutralization Tests , Pandemics , Regression Analysis , Sampling Studies , Treatment Outcome , Viral Envelope Proteins/immunology
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