RESUMO
BackgroundAntibodies and T cells cooperate to control virus infections. The definition of the correlates of protection necessary to manage the COVID-19 pandemic, require both immune parameters but the complexity of traditional tests limits virus-specific T cell measurements. MethodsWe test the sensitivity and performance of a simple and rapid SARS-CoV-2 Spike-specific T cell test based on stimulation of whole blood with peptides covering the SARS-CoV-2 Spike protein followed by cytokine (IFN-{gamma}, IL-2) measurement in different cohorts including BNT162b2 vaccinated (n=112; 201 samples), convalescent asymptomatic (n=62; 62 samples) and symptomatic (n=68; 115 samples) COVID-19 patients and SARS-CoV-1 convalescent individuals (n=12; 12 samples). ResultsThe sensitivity of the rapid cytokine whole blood test equates traditional methods of T cell analysis (ELISPOT, Activation Induced Markers). Utilizing this test we observed that Spike-specific T cells in vaccinated preferentially target the S2 region of Spike and that their mean magnitude is similar between them and SARS-CoV-2 convalescents at 3 months after vaccine or virus priming respectively. However, a wide heterogeneity of Spike-specific T cell magnitude characterizes the individual responses irrespective of the time of analysis. No correlation between neutralizing antibody levels and Spike-specific T cell magnitude were found. ConclusionsRapid measurement of cytokine production in whole blood after peptide activation revealed a wide dynamic range of Spike-specific T cell response after vaccination that cannot be predicted from neutralizing antibody quantities. Both Spike-specific humoral and cellular immunity should be tested after vaccination to define the correlates of protection necessary to evaluate current vaccine strategies.
RESUMO
Virus-specific humoral and cellular immunity act synergistically to protect the host from viral infection. We interrogated the dynamic changes of virological and immunological parameters in 12 patients with symptomatic acute SARS-CoV-2 infection from disease onset to convalescence or death. We quantified SARS-CoV-2 viral RNA in the respiratory tract in parallel with antibodies and circulating T cells specific for various structural (NP, M, ORF3a and spike) and non-structural proteins (ORF7/8, NSP7 and NSP13). We observed that while rapid induction and quantity of humoral responses were associated with increased disease severity, an early induction of SARS-CoV-2 specific T cells was present in patients with mild disease and accelerated viral clearance. These findings provide further support for a protective role of SARS-CoV-2 specific T cells over antibodies during SARS-CoV-2 infection with important implications in vaccine design and immune-monitoring.
RESUMO
To date, the SARS-CoV-2 genome has been considered genetically more stable than SARS-CoV or MERS-CoV. Here we report a 382-nt deletion covering almost the entire open reading frame 8 (ORF8) of SARS-CoV-2 obtained from eight hospitalized patients in Singapore. The deletion also removes the ORF8 transcription-regulatory sequence (TRS), which in turn enhances the downstream transcription of the N gene. We also found that viruses with the deletion have been circulating for at least four weeks. During the SARS-CoV outbreak in 2003, a number of genetic variants were observed in the human population [1], and similar variation has since been observed across SARS-related CoVs in humans and bats. Overwhelmingly these viruses had mutations or deletions in ORF8, that have been associated with reduced replicative fitness of the virus [2]. This is also consistent with the observation that towards the end of the outbreak sequences obtained from human SARS cases possessed an ORF8 deletion that may be associated with host adaptation [1]. We therefore hypothesise that the major deletion revealed in this study may lead to an attenuated phenotype of SARS-CoV-2.
