Heterologous immunization with Covishield and Pfizer vaccines against SARS-CoV-2 elicits a robust humoral immune response

  • Ali Toloue Ostadgavahi Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
  • Ryan Booth Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
  • Gary Sisson Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
  • Nichole McMullen Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
  • Michelle Warhuus Canadian Centre for Vaccinology, Dalhousie University, Halifax, Nova Scotia, Canada
  • Peter Robertson Canadian Centre for Vaccinology, Dalhousie University, Halifax, Nova Scotia, Canada
  • Matthew Miller Canadian Centre for Vaccinology, Dalhousie University, Halifax, Nova Scotia, Canada
  • Wanda C Allen Canadian Centre for Vaccinology, Dalhousie University, Halifax, Nova Scotia, Canada
  • May El Sherif Canadian Centre for Vaccinology, Dalhousie University, Halifax, Nova Scotia, Canada
  • Robert Brownlie Vaccine and Infectious Disease Organization (VIDO), Saskatoon, Saskatchewan, Canada
  • Darryl Falzarano Vaccine and Infectious Disease Organization (VIDO), Saskatoon, Saskatchewan, Canada
  • Christopher D Richardson Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
Keywords: SARS-CoV-2, COVID-19, heterologous immunization, humoral immunity, vaccines, neutralizing antibodies, serum titers, VSV-S reporter pseudovirus

Abstract

Understanding the efficacy and durability of heterologous immunization schedules against SARS-CoV-2 is critical, as supply demands and vaccine choices become significant issues in the global vaccination strategy. Here we characterize the neutralizing antibodies produced in two subjects who received combination immunizations against SARS-CoV-2, first with Covishield (Oxford–AstraZeneca) vaccine, followed 33 days later with a second dose (booster) shot of the Pfizer-BioNTech vaccine. Serum samples were collected 25 days following the primary vaccination and 13 days after the secondary Pfizer vaccination. Both subjects exhibited increased levels of isotype IgG and IgM antibodies directed against the entire spike protein following immunizations. These antibodies also exhibited increased reactivity with the receptor binding domain (RBD) in the spike protein and neutralized the infectivity of replicating vesicular stomatitis virus (VSV) that contains the COVID-19 coronavirus S protein gene in place of its normal G glycoprotein. This VSV pseudovirus also contains the reporter gene for enhanced green fluorescent protein (eGFP). Antibody titers against the spike protein and serum neutralization titers against the reporter virus are reported for the 2 heterologous vaccinated individuals and compared to a positive control derived from a convalescent patient and a negative control from an unexposed individual. The Pfizer-BioNTech vaccine increased antibody binding to the spike protein and RBD, and approached levels found in the convalescent positive control. Neutralizing antibodies against the VSV-S pseudovirus in the 2 subjects also approached levels in the convalescent sera. These results firmly validate the value of the Pfizer-BioNTech vaccine in boosting immunity following initial Covishield inoculation.

Published
2021-05-31
How to Cite
1.
Ostadgavahi AT, Booth R, Sisson G, McMullen N, Warhuus M, Robertson P, Miller M, Allen WC, El Sherif M, Brownlie R, Falzarano D, Richardson CD (2021) Heterologous immunization with Covishield and Pfizer vaccines against SARS-CoV-2 elicits a robust humoral immune response. J Infect Dev Ctries 15:653-656. doi: 10.3855/jidc.15368
Section
Coronavirus Pandemic

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