RESUMO
The rapid emergence of the Omicron variant and its large number of mutations has led to its classification as a variant of concern (VOC) by the WHO(1). Initial studies on the neutralizing response towards this variant within convalescent and vaccinated individuals have identified substantial reductions(2-8). However many of these sample sets used in these studies were either small, uniform in nature, or were compared only to wild-type (WT) or, at most, a few other VOC. Here, we assessed IgG binding, (Angiotensin-Converting Enzyme 2) ACE2 binding inhibition, and antibody binding dynamics for the omicron variant compared to all other VOC and variants of interest (VOI)(9), in a large cohort of infected, vaccinated, and infected and then vaccinated individuals. While omicron was capable of binding to ACE2 efficiently, antibodies elicited by infection or immunization showed reduced IgG binding and ACE2 binding inhibition compared to WT and all VOC. Among vaccinated samples, antibody binding responses towards omicron were only improved following administration of a third dose. Overall, our results identify that omicron can still bind ACE2 while pre-existing antibodies can bind omicron. The extent of the mutations appear to inhibit the development of a neutralizing response, and as a result, omicron remains capable of evading immune control.
RESUMO
The SARS-CoV-2 pandemic virus is consistently evolving with mutations within the receptor binding domain (RBD)1 being of particular concern2-4. To date, there is little research into protection offered following vaccination or infection against RBD mutants in emerging variants of concern (UK3, South African5, Mink6 and Southern California7). To investigate this, serum and saliva samples were obtained from groups of vaccinated (Pfizer BNT-162b28), infected and uninfected individuals. Antibody responses among groups, including salivary antibody response and antibody binding to RBD mutant strains were examined. The neutralization capacity of the antibody response against a patient-isolated South African variant was tested by viral neutralization tests and further verified by an ACE2 competition assay. We found that humoral responses in vaccinated individuals showed a robust response after the second dose. Interestingly, IgG antibodies were detected in large titers in the saliva of vaccinated subjects. Antibody responses showed considerable differences in binding to RBD mutants in emerging variants of concern. A substantial reduction in RBD binding and neutralization was detected for the South African variant. Taken together our data reinforces the importance of administering the second dose of Pfizer BNT-162b2 to acquire high levels of neutralizing antibodies. High antibody titers in saliva suggest that vaccinated individuals may have reduced transmission potential. Substantially reduced neutralization for the South African variant highlights importance of surveillance strategies to detect new variants and targeting these in future vaccines.
RESUMO
BO_SCPLOWACKGROUNDC_SCPLOWSeroreactivity against human endemic coronaviruses has been linked to disease severity after SARS-CoV-2 infection. Assays that are capable of concomitantly detecting antibodies against endemic coronaviridae such as OC43, 229E, NL63, and SARS-CoV-2 may help to elucidate this question. We set up a platform for serum-screening and developed a bead-based Western blot system, namely DigiWest, capable of running hundreds of assays using microgram amounts of protein prepared directly from different viruses. MO_SCPLOWETHODSC_SCPLOWThe parallelized and miniaturised DigiWest assay was adapted for detecting antibodies using whole protein extract prepared from isolated SARS-CoV-2 virus particles. After characterisation and optimization of the newly established test, whole virus lysates of OC43, 229E, and NL63 were integrated into the system. RO_SCPLOWESULTSC_SCPLOWThe DigiWest-based immunoassay system for detection of SARS-CoV-2 specific antibodies shows a sensitivity of 87.2 % and diagnostic specificity of 100 %. Concordance analysis with the SARS-CoV-2 immunoassays available by Roche, Siemens, and Euroimmun indicates a comparable assay performance (Cohens Kappa ranging from 0.8799-0.9429). In the multiplexed assay, antibodies against the endemic coronaviruses OC43, 229E, and NL63 were detected, displaying a high incidence of seroreactivity against these coronaviruses. CO_SCPLOWONCLUSIONC_SCPLOWThe DigiWest-based immunoassay, which uses authentic antigens from isolated virus particles, is capable of detecting individual serum responses against SARS-CoV-2 with high specificity and sensitivity in one multiplexed assay. It shows high concordance with other commercially available serologic assays. The DigiWest approach enables a concomitant detection of antibodies against different endemic coronaviruses and will help to elucidate the role of these possibly cross-reactive antibodies.
RESUMO
Given the importance of the humoral immune response to SARS-CoV-2 as a global benchmark for immunity, a detailed analysis is needed to monitor seroconversion in the general population, understand manifestation and progression of COVID-19 disease, and ultimately predict the outcome of vaccine development. In contrast to currently available serological assays, which are only able to resolve the SARS-CoV-2 antibody response on an individual antigen level, we developed a multiplex immunoassay, for which we included spike and nucleocapsid proteins of SARS-CoV-2 and the endemic human coronaviruses (NL63, OC43, 229E, HKU1) in an expanded antigen panel. Compared to three commercial in vitro diagnostic tests, our MULTICOV-AB assay achieved the highest sensitivity and specificity when analyzing a well-characterized sample set of SARS-CoV-2 infected and uninfected individuals. Simultaneously, high IgG responses against endemic coronaviruses became apparent throughout all samples, but no consistent cross-reactive IgG response patterns could be defined. In summary, we have established and validated, a robust, high-content-enabled, and antigen-saving multiplex assay MULTICOV-AB, which is highly suited to monitor vaccination studies and will facilitate epidemiologic screenings for the humoral immunity toward pandemic as well as endemic coronaviruses.
