ABSTRACT
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
We report an experimental infection of American mink with SARS-CoV-2 Omicron variant and show that mink remain virus RNA positive for days, develop clinical sings and histopathological changes, and transmit the virus to uninfected recipients warranting further studies and preparedness.
ABSTRACT
Two COVID-19 mRNA and two adenovirus vector vaccines have been licensed in Europe and various vaccine combinations and dosing strategies have been exploited to maximize the immunity against COVID-19. Here, we show that among health care workers (n=328) two doses of BNT162b2, mRNA-1273, or ChAdOx1 as also a combination of an adenovirus vector and mRNA vaccines induces equally high levels of anti-SARS-CoV-2 spike antibodies and neutralizing antibodies against B.1 and B.1.617.2 when administrated with a long 12-week dose interval. Two doses of BNT162b2 with a short 3-week interval induce 2-3-fold lower titers of neutralizing antibodies compared to the long interval. Third mRNA vaccine dose for the short dose interval group increased the antibody levels 4-fold compared to the levels after the second dose. Importantly, sera from all three-times vaccinated neutralized B.1.1.529 (Omicron). The data indicates that a third COVID-19 mRNA vaccine dose efficiently induces cross-protective neutralizing antibodies against multiple variants.
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
Wastewater-based surveillance is a cost-effective concept for monitoring COVID-19 pandemics at a population level. Here, SARS-CoV-2 RNA was monitored from a total of 693 wastewater (WW) influent samples from 28 wastewater treatment plants (WWTP, N = 21-42 samples per WWTP) in Finland from August 2020 to May 2021, covering WW of ca. 3.3 million inhabitants (~ 60% of the Finnish population). The relative quantity of SARS-CoV-2 RNA fragments in the 24h-composite samples was determined by using the ultrafiltration method followed by nucleic acid extraction and RT-qPCR assay targeted with N2-assay. SARS-CoV-2 RNA signals at each WWTP were compared over time to the numbers of new and confirmed COVID-19 cases in the sewer network area. Over the 10-month surveillance period, the detection rate of SARS-CoV-2 RNA in WW was 79% (including 6% uncertain results), while only 24% of all samples exhibited gene copy (GC) numbers above the quantification limit. The range of the SARS-CoV-2 detection rate in WW varied from 33% (including 10% uncertain results) in Pietarsaari to 100% in Espoo. Only six out of 693 WW samples were positive with SARS-COV-2 RNA when the reported COVID-19 case number from the preceding 14 days was zero. Overall, the 14-day COVID-19 incidence was 7.0, 18 and 36 cases within the sewer network area when the probability to detect SARS-CoV-2 RNA in wastewater samples was 50%, 75% and 95%, respectively. The quantification of SARS-CoV-2 GC required significantly more COVID-19 cases: the quantification rate was 50%, 75% and 95% when the 14-day incidence was 110, 152 and 223 COVID-19 cases, respectively, per 100 000 persons. Multiple linear regression confirmed the relationship between the COVID-19 incidence and the SARS-CoV-2 GC quantified in WW at 15 out of 28 WWTPs (overall R2 = 0.36, p < 0.001). At four of the 13 WWTPs where a significant relationship was not found, the GC of SARS-CoV-2 RNA remained below the quantification limit during the whole study period. In the five other WWTPs, the sewer coverage was less than 80% of the total population in the area and thus the COVID-19 cases may have been inhabitants from the areas not covered. Based on the results obtained, WW-based surveillance of SARS-CoV-2 could be used as an indicator for local and national COVID-19 incidence trends. Importantly, the determination of SARS-CoV-2 RNA fragments from WW is a powerful and non-invasive public health surveillance measure, independent of possible changes in the clinical testing strategies or in the willingness of individuals to be tested for COVID-19.
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 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
As SARS-CoV-2 has been circulating for over a year, dozens of vaccine candidates are under development or in clinical use. The BNT162b2 mRNA COVID-19 vaccine induces spike protein-specific neutralizing antibodies associated with protective immunity. The emergence of the B.1.1.7 and B.1.351 variants has raised concerns of reduced vaccine efficacy and increased re-infection rates. Here we show, that after the second dose, the sera of BNT162b2-vaccinated health care workers (n = 180) effectively neutralize the SARS-CoV-2 variant with the D614G substitution and the B.1.1.7 variant, whereas the neutralization of the B.1.351 variant is five-fold reduced. Despite the reduction, 92% of the vaccinees have a neutralization titre of >20 for the B.1.351 variant indicating some protection. The vaccinees’ neutralization titres exceeded those of recovered non-hospitalized COVID-19 patients. Our work provides strong evidence that the second dose of the BNT162b2 vaccine induces efficient cross-neutralization of SARS-CoV-2 variants currently circulating in the world.
Subject(s)
COVID-19ABSTRACT
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
The causative agent of the current pandemic and coronavirus disease 2019 (COVID-19) is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)1. Understanding how SARS-CoV-2 enters and spreads within human organs is crucial for developing strategies to prevent viral dissemination. For many viruses, tissue tropism is determined by the availability of virus receptors on the surface of host cells2. Both SARS-CoV and SARS-CoV-2 use angiotensin-converting enzyme 2 (ACE2) as a host receptor, yet, their tropisms differ3-5. Here, we found that the cellular receptor neuropilin-1 (NRP1), known to bind furin-cleaved substrates, significantly potentiates SARS-CoV-2 infectivity, which was inhibited by a monoclonal blocking antibody against the extracellular b1b2 domain of NRP1. NRP1 is abundantly expressed in the respiratory and olfactory epithelium, with highest expression in endothelial cells and in the epithelial cells facing the nasal cavity. Neuropathological analysis of human COVID-19 autopsies revealed SARS-CoV-2 infected NRP1-positive cells in the olfactory epithelium and bulb. In the olfactory bulb infection was detected particularly within NRP1-positive endothelial cells of small capillaries and medium-sized vessels. Studies in mice demonstrated, after intranasal application, NRP1-mediated transport of virus-sized particles into the central nervous system. Thus, NRP1 could explain the enhanced tropism and spreading of SARS-CoV-2.