Torquetenovirus Loads in Peripheral Blood Predict Both the Humoral and Cell-Mediated Responses to SARS-CoV-2 Elicited by the mRNA Vaccine in Liver Transplant Recipients

Abstract

Three years into the COVID-19 pandemic, mass vaccination campaigns have largely controlled the disease burden but have not prevented virus circulation. Unfortunately, many immunocompromised patients have failed to mount protective immune responses after repeated vaccinations, and liver transplant recipients are no exception. Across different solid organ transplant populations, the plasma levels of Torquetenovirus (TTV), an orphan and ubiquitous human virus under control of the immune system, have been shown to predict the antibody response after COVID-19 vaccinations. We show here a single-institution experience with TTV viremia in 134 liver transplant recipients at their first or third dose. We found that TTV viremia before the first and third vaccine doses predicts serum anti-SARS-CoV-2 Spike receptor-binding domain (RBD) IgG levels measured 2–4 weeks after the second or third dose. Pre-vaccine TTV loads were also associated with peripheral blood anti-SARS-CoV-2 cell-mediated immunity but not with serum SARS-CoV-2 neutralizing antibody titers.

Torquetenovirus Viremia Quantification Using Real-Time PCR Developed on a Fully Automated, Random-Access Platform

“…Each of these viruses consists of numerous species and strains. The recent evidence that TTV represents the most abundant component of the human virome and establishes a highly successful interaction with the infected host [ 1 ] has highlighted the importance of using the monitoring of TTV viremia as a biomarker of functional immune competence [ 9 , 10 , 11 , 12 , 13 , 14 ]. Thus, the use of diagnostic tests that can be performed for rapid and sensitive quantification of TTV is of utmost importance for follow-up monitoring and therapy decisions in several patient settings, notably solid organ transplant recipients [ 15 , 16 ].…”