SARS-CoV-2 recombinant proteins stimulate distinct cellular and humoral immune response profiles in samples from COVID-19 convalescent patients

• Published in: Clinics (São Paulo, Brazil) Vol. 76; p. e3548
• Main Authors: Silva, Laís Teodoro da, Ortega, Marina Mazzilli, Tiyo, Bruna Tiaki, Viana, Isabelle Freire Tabosa, Lima, Tayná Evily de, Tozetto-Mendoza, Tania Regina, Oliveira, Luanda Mara da Silva, Teixeira, Franciane Mouradian Emidio, Lins, Roberto Dias, Almeida, Alexandre de, Mendes-Correa, Maria Cassia, da Silva Duarte, Alberto Jose, Oshiro, Telma Miyuki
• Format: Journal Article
• Language: English
• Published: Brazil Elsevier España, S.L.U 01-01-2021; Faculdade de Medicina / USP; Elsevier España
• Subjects: Antigens; COVID-19; Immune Response; MEDICINE, GENERAL & INTERNAL; Original; SARS-CoV-2; COVID-19; Antigens; SARS-CoV-2; Immune Response
• ISSN: 1807-5932; 1980-5322; 1980-5322
• DOI: 10.6061/clinics/2021/e3548

In this preliminary study we investigated cellular and humoral immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens in blood samples from 14 recovered coronavirus disease 2019 (COVID-19) patients and compared them to those in samples from 12 uninfected/unvaccinated volunteers.
Cellular immunity was assessed by intracellular detection of IFN-γ in CD3+ T lymphocytes after stimulation with SARS-CoV-2 spike (S1), nucleocapsid (NC), or receptor-binding domain (RBD) recombinant proteins or overlapping peptide pools covering the sequence of SARS-CoV-2 spike, membrane and nucleocapsid regions. The humoral response was examined by ELISAs and/or chemiluminescence assays for the presence of serum IgG antibodies directed to SARS-CoV-2 proteins.
We observed differences between humoral and cellular immune profiles in response to stimulation with the same proteins. Assays of IgG antibodies directed to SARS-CoV-2 NC, RBD and S1/S2 recombinant proteins were able to differentiate convalescent from uninfected/unvaccinated groups. Cellular immune responses to SARS-CoV-2 protein stimuli did not exhibit a specific response, as T cells from both individuals with no history of contact with SARS-CoV-2 and from recovered donors were able to produce IFN-γ.
Determination of the cellular immune response to stimulation with a pool of SARS-CoV-2 peptides but not with SARS-CoV-2 proteins is able to distinguish convalescent individuals from unexposed individuals. Regarding the humoral immune response, the screening for serum IgG antibodies directed to SARS-CoV-2 proteins has been shown to be specific for the response of recovered individuals.