COVID-19 in twins: What can we learn from them

Investigations on the concordance in monozygotic (MZ) as compared to dizygotic (DZ) twins may reveal if there is a genetic component increasing the susceptibility or resistance against an infectious disease. Here, we compared the concordance rates of SARS-CoV-2 infection in MZ versus DZ young twins who shared the same bedrooms and were equally exposed to the virus. The concordance rate was higher in the MZ group supporting a complex multifactorial inheritance responsible for SARS-Cov-2 infection.

Monozygotic twins discordant for severe clinical recurrence of COVID-19 show drastically distinct T cell responses to SARS-Cov-2

BackgroundClinical recurrence of COVID-19 in convalescent patients has been reported, which immune mechanisms have not been thoroughly investigated. Presence of neutralizing antibodies suggests other types of immune response are involved. MethodsWe assessed the innate type I/III IFN response, T cell responses to SARS-CoV-2 with IFN{gamma} ELISPOT, binding and neutralizing antibody assays, in two monozygotic twin pairs with one COVID-19 recurrence case. ResultsIn pair 1, four months after a first mild episode of infection for both siblings, one displayed severe clinical recurrence of COVID-19. Twin pair 2 of siblings underwent non-recurring asymptomatic infection. All fours individuals presented similar overall responses, except for remarkably difference found in specific cellular responses. Recurring sibling presented a reduced number of recognized T cell epitopes as compared to the other three including her non-recurring sibling. ConclusionsOur results suggest that an effective SARS-CoV-2-specific T cell immune response is key for complete viral control and avoidance of clinical recurrence of COVID-19. Besides, adaptive immunity can be distinct in MZ twins. Given the rising concern about SARS-CoV-2 variants that evade neutralizing antibodies elicited by vaccination or infection, our study stresses the importance of T cell responses in protection against recurrence/reinfection. Key pointsImmune parameters leading to COVID-19 recurrence/reinfection are incompletely understood. A COVID-19 recurrence case in a monozygotic twin pair is described with an intact antibody and innate type I/III Interferon response and drastically reduced number of recognized SARS-CoV-2 T cell epitopes.