ABSTRACT
BackgroundData on Covid-19 booster vaccinations and subsequent infections on immune responses in the immunocompromised is limited. We studied antibody responses after the fourth dose and subsequent breakthrough infection to define patient groups benefiting most from boosters. MethodsIn Finland, fourth vaccine (booster) doses were first recommended for severely immunocompromised individuals, whom we invited to participate in 2022. We assessed spike protein specific IgG antibody levels and neutralizing antibodies (NAb) against the ancestral and Omicron BA.1 strains one month after the fourth dose from 488 adult participants and compared to the levels of 35 healthy controls after 3 doses. We used Bayesian generalized linear modelling to assess factors explaining antibody concentrations after the fourth dose. We assessed vaccine-induced and hybrid immunity six months after the last vaccine dose. ResultsChronic kidney disease (CKD) and immunosuppressive therapy (IT) were identified as factors explaining sub-optimal antibody responses. The proportion of participants with a normal antibody response and NAbs were significantly lower in CKD patients as compared to controls. By the 6-month sampling one third of the participants became infected, which enhanced antibody levels notably in most immunocompromised participants. ConclusionsImpaired antibody responses, especially NAbs against the Omicron lineage, predict limited protection in individuals with CKD, and highlight the need for alternative pharmaceutical preventive strategies. Vaccination strategies should take into account development of robust hybrid immunity responses also among the immunocompromised.
Subject(s)
Breakthrough Pain , Kidney Diseases , Neoplasms, Second Primary , COVID-19ABSTRACT
The prime-boost COVID-19 mRNA vaccination strategy has proven to be effective against severe COVID-19 disease and death. However, concerns have been raised due to decreasing neutralizing antibody levels after COVID-19 vaccination and due to the emergence of new immuno-evasive SARS-CoV-2 variants that may require additional booster vaccinations. Here we show that within the vaccinated health care workers (HCWs) the third mRNA vaccine dose recalls both humoral and T cell-mediated immune responses and induces high levels of neutralizing antibodies against Omicron BA.1 and BA.2 variants. Three weeks after the third vaccine dose, SARS-CoV-2 wild type spike protein-specific CD4+ and CD8+ T cells are observed in 82% and 71% of HCWs, respectively, and the T cells cross-recognize both Omicron BA.1 and BA.2 spike peptides. Although the levels of neutralizing antibodies against Omicron BA.1 and BA.2 decline 2.5 to 3.8-fold three months after the third dose, Th1-type memory CD4+ T cell responses are maintained for at least 7 months post the second dose and 3 months post the third vaccine dose suggesting durable immune protection.
Subject(s)
Death , COVID-19ABSTRACT
Background Previous SARS-CoV-2 infection primes the immune system and thus individuals who recovered from infection have enhanced immune responses to subsequent vaccination (hybrid immunity). However, it remains unclear how well hybrid immunity induced by severe or mild infection can cross-neutralize emerging variants. We aimed to compare the strength and breadth of antibody responses in vaccinated recovered and uninfected subjects. Methods We measured spike-specific IgG and neutralizing antibodies (NAbs) from vaccinated subjects including 320 with hybrid immunity and 20 without previous infection. From 29 subjects with a previous severe or mild infection, we also measured NAb responses against Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2) and Omicron (B.1.1.529/BA.1) variants following vaccination. Results A single vaccine dose induced 2-fold higher anti-spike IgG concentrations and 3-fold higher neutralizing potency of antibodies in previously infected compared to uninfected fully vaccinated subjects. We found similar IgG concentrations in previously infected subjects after one or two vaccine doses. NAb titers were higher in subjects with severe compared to those with mild infection. This difference remained after vaccination with sequentially decreasing titers against Alpha, Beta, Delta, and Omicron variants. Conclusions Hybrid immunity induced strong IgG responses, particularly after severe infection. However, the NAb titers were low against heterologous variants, especially against Omicron.
Subject(s)
COVID-19ABSTRACT
The emergence of the SARS-CoV-2 Omicron variant capable of escaping neutralizing antibodies emphasizes the need for prophylactic strategies to complement vaccination in fighting the COVID-19 pandemic. Nasal epithelium is rich in the ACE2 receptor and important for SARS-CoV-2 transmission by supporting early viral replication before seeding to the lung1. Intranasal administration of SARS-CoV-2 neutralizing antibodies or antibody fragments has shown encouraging potential as a protective measure in animal models2-5. However, there remains a need for SARS-CoV-2 blocking agents that are more economical to produce in large scale, while less vulnerable to mutational variation in the neutralization epitopes of the viral Spike glycoprotein. Here we describe TriSb92, a highly manufacturable trimeric human nephrocystin SH3 domain-derived antibody mimetic targeted against a conserved region in the receptor-binding domain of the Spike. TriSb92 potently neutralizes SARS-CoV-2 and its variants of concern, including Delta and Omicron. Intranasal administration of a modest dose of TriSb92 (5 or 50 micrograms) as early as eight hours before the challenge with SARS-CoV-2 B.1.351 efficiently protected mice from infection. The target epitope of TriSb92 was defined by cryo-EM, which revealed triggering of a conformational shift in the Spike trimer rather than competition for ACE2 binding as the molecular basis of its strong inhibitory action. Our results highlight the potential of intranasal inhibitors in protecting susceptible individuals from SARS-CoV-2 infection, and describe a novel type of inhibitor that could be of use in addressing the challenge posed by the Omicron variant.
Subject(s)
COVID-19ABSTRACT
The emergence of the SARS-CoV-2 Omicron variant capable of escaping neutralizing antibodies emphasizes the need for prophylactic strategies to complement vaccination in fighting the COVID-19 pandemic. Nasal epithelium is rich in the ACE2 receptor and important for SARS-CoV-2 transmission by supporting early viral replication before seeding to the lung. Intranasal administration of SARS-CoV-2 neutralizing antibodies or antibody fragments has shown encouraging potential as a protective measure in animal models. However, there remains a need for SARS-CoV-2 blocking agents that are more economical to produce in large scale, while less vulnerable to mutational variation in the neutralization epitopes of the viral Spike glycoprotein. Here we describe TriSb92, a highly manufacturable trimeric human nephrocystin SH3 domain-derived antibody mimetic targeted against a conserved region in the receptor-binding domain of the Spike. TriSb92 potently neutralizes SARS-CoV-2 and its variants of concern, including Delta and Omicron. Intranasal administration of a modest dose of TriSb92 (5 or 50 micrograms) as early as eight hours before the challenge with SARS-CoV-2 B.1.351 efficiently protected mice from infection. The target epitope of TriSb92 was defined by cryo-EM, which revealed triggering of a conformational shift in the Spike trimer rather than competition for ACE2 binding as the molecular basis of its strong inhibitory action. Our results highlight the potential of intranasal inhibitors in protecting susceptible individuals from SARS-CoV-2 infection, and describe a novel type of inhibitor that could be of use in addressing the challenge posed by the Omicron variant.
Subject(s)
COVID-19ABSTRACT
The emergence of SARS-CoV-2 Omicron variant (B.1.1.529) with major spike protein mutations has raised concern over potential neutralization escape and breakthrough infections among vaccinated and previously SARS-CoV-2 infected subjects. We measured cross-protective antibodies against variants in health care workers (HCW, n=20) and nursing home residents (n=9) from samples collected 1-2 months following the booster (3rd) dose. We also assessed the antibody responses in prior to Omicron era infected subjects (n=38) with subsequent administration of a single mRNA vaccine dose. Following booster vaccination HCWs had high IgG antibody concentrations to the spike protein and neutralizing antibodies (NAb) were detectable against all variants. IgG concentrations among the elderly remained lower, and some lacked NAbs against the Beta and Omicron variants. NAb titers were significantly reduced against Delta, Beta and Omicron compared to wild-type virus regardless of age. Vaccination induced high IgG concentrations and variable titers of cross-reactive NAbs in previously infected subjects, whereas NAb titers against Omicron were barely detectable 1-month post-infection. High IgG concentrations with cross-protective neutralizing activity were detected after three COVID-19 vaccine doses in HCWs. However, lower NAb titers seen in the frail elderly suggest inadequate protection against Omicron breakthrough infections, yet protection against severe COVID-19 is expected. Clinical trial registration EudraCT 2021-004788-29
Subject(s)
COVID-19ABSTRACT
Background. Validation and standardization of accurate serological assays are crucial for the surveillance of the coronavirus disease 2019 (COVID-19) pandemic and population immunity. Methods. We describe the analytical and clinical performance of an in-house fluorescent multiplex immunoassay (FMIA) for simultaneous quantification of antibodies against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleoprotein and spike glycoprotein. Furthermore, we calibrated IgG-FMIA against World Health Organisation (WHO) International Standard and compared FMIA results to an in-house enzyme immunoassay (EIA) and a microneutralisation test (MNT). We also compared the MNT results of two laboratories. Results. IgG-FMIA displayed 100% specificity and sensitivity for samples collected 13-150 days post-onset of symptoms (DPO). For IgA- and IgM-FMIA 100% specificity and sensitivity were obtained for a shorter time window (13-36 and 13-28 DPO for IgA- and IgM-FMIA, respectively). FMIA and EIA results displayed moderate to strong correlation, but FMIA was overall more specific and sensitive. IgG-FMIA identified 100% of samples with neutralising antibodies (NAbs). Anti-spike IgG concentrations correlated strongly ({rho}=0.77-0.84, P<2.2x10-16) with NAb titers. The NAb titers of the two laboratories displayed a very strong correlation ({rho}=0.95, P<2.2x10-16). Discussion. Our results indicate good correlation and concordance of antibody concentrations measured with different types of in-house SARS-CoV-2 antibody assays. Calibration against WHO international standard did not, however, improve the comparability of FMIA and EIA results. keywords: SARS-CoV-2, COVID-19, antibody, immunoassay, nucleoprotein, spike glycoprotein, WHO international standard, neutralising antibodies, microneutralisation, receptor-binding domain
Subject(s)
Coronavirus Infections , COVID-19ABSTRACT
Background Household transmission studies offer the opportunity to assess both secondary attack rate and persistence of SARS-CoV-2 antibodies over time. Methods We invited confirmed COVID-19 cases and their household members to attend up to four household visits with collection of nasopharyngeal and serum samples over 28 days after index case onset. We calculated secondary attack rates (SAR) based on the presence of SARS-CoV-2 nucleoprotein IgG antibodies (IgG Ab) and/or neutralizing antibodies (NAb) overall and per households. Three and six months later, we assessed the persistence of SARS-CoV-2 antibodies. Findings We recruited 39 index cases and 90 household members. Among 87 household members evaluated, SAR was 48% (n=42), including 37 symptomatic secondary cases. In total, 80/129 (62%) participants developed both IgG Ab and NAb, while three participants only developed IgG Ab. Among participants who had both IgG Ab and NAb during the initial follow-up, 68/69 (99%) and 63/70 (90%) had IgG Ab and NAb at 3 months, while at 6 months, 59/75 (79%) and 63/75 (84%) had IgG Ab and NAb, respectively. Participants who required hospital care had initially 5-fold IgG Ab concentrations compared to cases with mild symptoms and 8-fold compared to asymptomatic cases. Interpretation Following detection of a COVID-19 case in a household, other members had a high risk of becoming infected. Follow-up of participants showed strong persistence of antibodies in most cases. Funding This study was supported by THL coordinated funding for COVID-19 research (Finnish Government's supplementary budget) and by the Academy of Finland (Decision number 336431).
Subject(s)
COVID-19ABSTRACT
Background: Household transmission studies offer the opportunity to assess both secondary attack rate and persistence of SARS-CoV-2 antibodies over time.Methods: We invited confirmed COVID-19 cases and their household members to attend up to four household visits with collection of nasopharyngeal and serum samples over 28 days after index case onset. We calculated secondary attack rates (SAR) based on the presence of SARS-CoV-2 nucleoprotein IgG antibodies (IgG Ab) and/or neutralizing antibodies (NAb) overall and per households. Three and six months later, we assessed the persistence of SARS-CoV-2 antibodies.Findings: We recruited 39 index cases and 90 household members. Among 87 household members evaluated, SAR was 48% (n=42), including 37 symptomatic secondary cases. In total, 80/129 (62%) participants developed both IgG Ab and NAb, while three participants only developed IgG Ab. Among participants who had both IgG Ab and NAb during the initial follow-up, 68/69 (99%) and 63/70 (90%) had IgG Ab and NAb at 3 months, while at 6 months, 59/75 (79%) and 63/75 (84%) had IgG Ab and NAb, respectively. Participants who required hospital care had initially 5-fold IgG Ab concentrations compared to cases with mild symptoms and 8-fold compared to asymptomatic cases.Interpretation: Following detection of a COVID-19 case in a household, other members had a high risk of becoming infected. Follow-up of participants showed strong persistence of antibodies in most cases.Funding Information: This study was supported by THL coordinated funding for COVID-19 research (Finnish Government’s supplementary budget) and by the Academy of Finland (Decision number 336431).Declaration of Interests: THL has received research funding for studies not related to COVID-19 from GlaxoSmithKline Vaccines (NE, CV, AAP and MM as investigators), Pfizer (AAP) and Sanofi Pasteur (AAP). Other authors have no competing interests.Ethics Approval Statement: The Finnish communicable diseases law and the law on the duties of the Finnish Institute for Health and Welfare allowed the implementation of the initial household transmission study and 3 months convalescent sample collection without seeking further institutional ethical review11,12. The protocol for the follow-up visits at 6 months was reviewed and approved by the HUS ethical committee and registered under the Development of seroprevalence in Finland during the new coronavirus (SARS-CoV-2) epidemic – serological population study protocol HUS/1137/2020. Informed consent was obtained from all cases and contacts or their parents or legal guardian before any procedure was performed.
Subject(s)
COVID-19ABSTRACT
Understanding for how long antibodies persist following Severe acute respiratory coronavirus 2 (SARS-CoV-2) infection provides important insight into estimating the duration of immunity induced by infection. We assessed the persistence of serum antibodies following wild-type SARS-CoV-2 infection six and twelve months after diagnosis in 367 individuals of whom 13% had severe disease requiring hospitalization. We determined the SARS-CoV-2 spike (S-IgG) and nucleoprotein IgG concentrations and the proportion of subjects with neutralizing antibodies (NAb). We also measured the NAb titers among a smaller subset of participants (n=78) against a wild-type virus (B.1) and three variants of concern (VOCs): Alpha (B.1.1.7), Beta (B.1.351) and Delta (B.1.617.2). We found that NAb against the wild-type virus and S-IgG persisted in 89% and 97% of subjects for at least twelve months after infection, respectively. IgG and NAb levels were higher after severe infection. NAb titers were significantly lower against variants compared to the wild-type virus.
Subject(s)
Severe Acute Respiratory Syndrome , COVID-19ABSTRACT
COVID-19 diagnostics was quickly ramped up worldwide early 2020 based on the detection of viral RNA. However, based on the scientific knowledge for pre-existing coronaviruses, it was expected that the SARS-CoV-2 RNA will be detected from symptomatic and at significant rates also from asymptomatic individuals due to persistence of non-infectious RNA. To increase the efficacy of diagnostics, surveillance, screening and pandemic control, rapid methods, such as antigen tests, are needed for decentralized testing and to assess infectiousness. A novel automated mariPOC SARS-CoV-2 test was developed for the detection of conserved structural viral nucleocapsid proteins. The test utilizes sophisticated optical laser technology for two-photon excitation and individual detection of immunoassay solid-phase particles. We validated the new method against qRT-PCR. Sensitivity of the test was 100.0% (13/13) directly from nasopharyngeal swab specimens and 84.4% (38/45) from swab specimens in undefined transport mediums. Specificity of the test was 100.0% (201/201). The test's limit of detection was 2.7 TCID50/test. It showed no cross-reactions. Our study shows that the new test can detect infectious individuals already in 20 minutes with clinical sensitivity close to qRT-PCR. The mariPOC is a versatile platform for syndromic testing and for high capacity infection control screening of infectious individuals.
Subject(s)
COVID-19ABSTRACT
Novel SARS coronavirus causing COVID-19 was recognized in late 2019. Diagnostics was quickly ramped up worldwide based on the detection of viral RNA. Based on the scientific knowledge for pre-existing coronaviruses, it was expected that the RNA of this novel coronavirus will be detected at significant rates from symptomatic and asymptomatic individuals due to existence of non-infectious RNA. To increase the efficacy of diagnostics, surveillance, screening and pandemic control, rapid methods, such as antigen tests, are needed for decentralized testing and to assess infectiousness. The objectives were to verify analytical sensitivity and specificity, and assess the clinical sensitivity, specificity and usability of a novel automated mariPOC SARS-CoV-2 test based on sophisticated optical laser technology detecting viral structure proteins. Analytical performance was verified using bacterial and viral preparations. Clinical performance of the test was evaluated against qRT-PCR in a retrospective study with nasopharyngeal swab specimens (N=211) collected from symptomatic patients suspected of acute SARS-CoV-2 infections. Sensitivity and specificity of the mariPOC test were 92.3% (12/13) and 100.0% (198/198), respectively. The test's limit of detection was 22 PFU/test and it had no cross-reactions with the tested respiratory microbes. Our study shows that the mariPOC can detect infectious individuals already in 20 minutes while clinical sensitivity close to qRT-PCR is achieved in two hours or less. The test targets conserved epitopes of SARS-CoV-2 nucleoprotein, making it robust against strain variations. The new test is a promising and versatile tool for syndromic testing of symptomatic cases and for high capacity infection control screening.
Subject(s)
COVID-19 , Severe Acute Respiratory SyndromeABSTRACT
Background: Sensitive and highly specific antibody tests are critical for detection of SARS-CoV-2 antibodies especially in populations where seroprevalence is low. Aim: To set up, optimize and evaluate the analytical and clinical performance of a new in-house microsphere immunoassay for measurement of IgG antibodies to SARS-CoV-2 nucleoprotein for assessment of population seroprevalence in Finland. Methods: We set up a new in-house microsphere immunoassay (FMIA) with SARS-CoV-2 nucleoprotein and optimized its analytical performance. For evaluation of clinical performance, we tested sera collected in a well-characterized cohort of PCR positive-confirmed SARS-CoV-2 patients (n=89) with mostly mild symptoms, and before the COVID-19 pandemic (n=402), for nucleoprotein specific IgG concentrations by FMIA and a commercial chemiluminescent immunoassay and for neutralizing antibodies by the microneutralization test. Results: The analytical performance of FMIA was established in terms of sensitivity, linearity and precision. FMIA discriminated between COVID-19 patient and control samples with high specificity (100%) and sensitivity (100%). We generated FMIA seropositivity cut-offs, 0.46 and 1.71 U/ml, for low- and high-seroprevalence settings, respectively. In addition, we obtained high level of agreement between FMIA results and results by the microneutralization test. Conclusion: The fluorescent microsphere immunoassay showed excellent analytical and clinical performance and is well suited for serosurveillance studies of SARS-CoV-2. However, to optimize analytical sensitivity and clinical specificity of the assay, different seropositivity thresholds depending on the intended use of the assay and the target population, may be needed.
Subject(s)
COVID-19ABSTRACT
Background: The role of children in SARS-CoV-2 transmission is unclear. We investigated two COVID-19 school exposure incidents in the Helsinki area. Methods: We conducted two retrospective cohort studies after schools exposures, with a household transmission extension. We defined a case as an exposed person with either a positive RT-PCR, or positive microneutralisation testing (MNT) as confirmation of SARS-CoV-2 nucleoprotein IgG antibodies detection via fluorescent microsphere immunoassay (FMIA). We recruited close school contacts and families of school cases, calculated attack rates (AR) on school level and families, and identified transmission chains. Findings: In incident A, the index was a pupil. Participation rate was 74% (89/121), and no cases were identified. In incident B, the index was a member of school personnel. Participation rate was 81% (51/63). AR was 16% (8/51): 6 pupils and 1 member of school personnel were MNT and FMIA positive; 1 pupil had a positive RT-PCR, but negative serology samples. We visited all school cases' families (n=8). The AR among close household contacts was 42% (9/20 in 3/8 families) but other plausible sources were always reported. At three months post-exposure, 6/8 school cases were re-sampled and still MNT positive. Interpretation: When the index was a child, no school transmission was identified, while the occurrence of an adult case led to a 16% AR. Further cases were evidenced in 3 families, but other transmission chains were plausible. It is likely that transmission from children to adults is limited. Funding: The Finnish Institute for Health and Welfare funded this study.
Subject(s)
COVID-19ABSTRACT
ObjectiveWe compared the clinical characteristics, findings and outcomes of hospitalized patients with coronavirus disease 2019 (COVID-19) or influenza to detect relevant differences. MethodsFrom December 2019 to April 2020, we recruited all eligible hospitalized adults with respiratory infection to a prospective observational study at the HUS Jorvi Hospital, Finland. Influenza and SARS-CoV-2 infections were confirmed by RT-PCR. Follow-up lasted for at least 30 days from admission. ResultsWe included 61 patients, of whom 28 were COVID-19 and 33 influenza patients with median ages of 53 and 56 years. Majority of both COVID-19 and influenza patients were men (61% vs 67%) and had at least one comorbidity (68% vs 85%). Pulmonary diseases and current smoking were less common among COVID-19 than influenza patients (5 [18%] vs 15 [45%], P=0.03 and 1 [4%] vs 10 [30%], P=0.008). In chest x-ray at admission, ground-glass opacities and consolidations were more frequent among COVID-19 than influenza patients (19 [68%] and 7 [21%], P < 0.001). Severe disease and intensive care unit (ICU) admission occurred more often among COVID-19 than influenza patients (26 [93%] vs 19 [58%], P=0.003 and 8 [29%] vs 2 [6%], P=0.034). COVID-19 patients were hospitalized longer than influenza patients (6 days [IQR 4-21] vs 3 [2-4], P<0.001). ConclusionBilateral ground-glass opacities and consolidations in chest X-ray may help to differentiate COVID-19 from influenza. Hospitalized COVID-19 patients had more severe disease, required longer hospitalization and were admitted to ICU more often than influenza patients, which has important implications for public health policies.