Using this cut-off, 5 out of 45 (11.1%) and 3 out of 19 (15.8%) of individuals had IgG Liquiritigenin levels below the cut-off against all three antigens (the spike protein, the RBD and the nucleoprotein) between 145 and 217 days POS (TP3 and TP4) and 257 and 305 days POS (TP5), respectively. findings will inform the optimization of vaccines to protect against SARS-CoV-2 variants. Subject terms:Viral infection, SARS-CoV-2 The authors assess the durability and long-term cross-reactivity of neutralizing antibodies raised in response to infections with SARS-CoV-2 or variants of concern in humans. == Main == Neutralizing antibodies against the spike glycoprotein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are important in protection against re-infection and/or severe disease16. An important component of vaccines that protect against COVID-19 is the elicitation of neutralizing antibodies that bind the SARS-CoV-2 spike protein. A major challenge in controlling the COVID-19 pandemic will be the elicitation of a durable neutralizing antibody response that also provides protection against emerging variants of SARS-CoV-2. While the kinetics and correlates of the neutralizing antibody response have been extensively studied in the early phase following SARS-CoV-2 infection712, information on the durability and long-term cross-reactivity of the antibody response against SARS-CoV-2 following infection and/or vaccination is limited due to its recent emergence in the human population and large-scale COVID-19 vaccination only being initiated in December 2020. We have previously studied the antibody response in SARS-CoV-2-infected healthcare workers and in hospitalized individuals Liquiritigenin in the first 3 months following infection using longitudinal samples8. We showed that the humoral immune response was typical of that following an acute viral infection whereby the sera neutralizing activity peaked around 35 weeks post onset of symptoms (POS) and then declined as the short-lived antibody-secreting cells die3. However, it remained to be seen whether the neutralizing antibody response would continue to decline after the first 3 months POS or reach a steady state. In the absence of current long-term COVID-19 vaccine follow-up, knowledge of the longevity of the neutralizing antibody response acquired through natural infection with ancestral SARS-CoV-2 during wave 1 of the COVID-19 pandemic at late time points (up to 10 months POS) may provide important indicators for the durability of vaccine-induced humoral immunity. SARS-CoV-2 variants encoding mutations in the spike protein have been identified and include B.1.1.7 (Alpha variant, initially reported in the United Kingdom)13, Rabbit polyclonal to GSK3 alpha-beta.GSK3A a proline-directed protein kinase of the GSK family.Implicated in the control of several regulatory proteins including glycogen synthase, Myb, and c-Jun.GSK3 and GSK3 have similar functions.GSK3 phophorylates tau, the principal component of neuro P.1 (Gamma variant, first reported in Brazil), B.1.351 (Beta variant, first reported in South Africa)14and B.1.617.2 (Delta variant, first reported in India)15, which have been associated with more efficient transmission1618. Mutations of particular concern for vaccine immunity are those present in the receptor binding domain (RBD) of the spike protein, which is a dominant target for the neutralizing antibody response1922. Despite B.1.1.7, P.1, B.1.351 and B.1.617.2 showing increased resistance to neutralization by convalescent and vaccinee sera collected at the peak of the antibody response20,2339, cross-neutralizing activity has been observed. In contrast, complete loss of neutralization has been observed for some monoclonal antibodies (mAbs) focusing on specific epitopes on either Liquiritigenin the amino-terminal website (NTD) or the RBD of the spike protein20,25,27,28,40. Combined, Liquiritigenin these studies indicate that mutations in the spike protein may be arising in part due to the selective pressure of neutralizing antibodies in convalescent plasma4143. To counter such mutations and their attendant antigenic changes, vaccines using the spike proteins from these variants of concern (VOCs) are under investigation4447. Whether the variant spike proteins will elicit a strong neutralizing response with superior cross-neutralizing activity against parental strains and newly emerging variants has not been extensively analyzed29,48,49. Natural infection provides an important opportunity to compare the neutralizing antibody titres and cross-neutralizing activity generated from individuals exposed to different spike variants and will give insights into the antigenic range between spike variants, therefore informing the design of second-generation vaccine candidates based on VOCs. We set out to investigate the longevity of the neutralizing and cross-neutralizing antibody response against viral variants from wave 1 infections up to 10 weeks POS, the immunogenicity of the B.1.1.7, B.1.351 and B.1.617.2 spike variants in natural illness, and the antigenic range between SARS-CoV-2 VOCs. We collected sera in an observational study between 145 and 305 days POS from individuals infected in wave 1 who have been hospitalized patient and healthcare worker cohorts8,.