SARS-CoV-2 persistence is associated with antigen-specific CD8 T-cell responses

Area of Science:

• Virology
• Immunology
• Epidemiology

Background:

• Most individuals develop immunity after SARS-CoV-2 infection.
• Some recovered individuals remain PCR positive for SARS-CoV-2 weeks after symptom resolution.
• The contagiousness and immune stimulation by persistent viral RNA are unknown.

Purpose of the Study:

• To investigate the contagiousness of persistent SARS-CoV-2 RNA in recovered individuals.
• To assess SARS-CoV-2-specific immune responses in persistent carriers.
• To determine if persistent PCR positivity poses a transmission risk.

Main Methods:

• Cohort study of 203 COVID-19 recovered individuals.
• Collected serum for antibody detection (ELISA) and pharyngeal swabs for viral RNA (ddPCR).
• Analyzed PBMCs for anti-SARS-CoV-2 CD8 T-cell responses using dextramer analysis.

Main Results:

• 12.8% and 5.3% of participants were PCR positive at 23 and 90 days post-recovery, respectively.
• No difference in antibody levels between PCR positive and negative groups.
• Persistent PCR positive individuals showed enhanced SARS-CoV-2-specific CD8 T-cell responses.
• Zero new COVID-19 cases were observed among 757 close contacts of persistent PCR positive individuals.

Conclusions:

• Persistent pharyngeal SARS-CoV-2 PCR positivity is linked to heightened cellular immunity.
• Viral RNA in persistent carriers may represent replication but is not associated with transmission.
• Post-symptomatic individuals with persistent PCR positivity are not contagious.