DISCUSSION
Anelloviruses, and Torque Teno virus (TTV) in particular, are now considered potential surrogate markers of cellular immunity in solid organ transplant recipients. Interestingly, recent reports found that high levels of TTV in blood are predictive of a poor response to SARS-CoV-2 vaccination in lung and kidney transplant recipients (13–15).
In this study, we observed that the TTV load in nasopharyngeal samples could predict the need for ICU admission in patients infected with SARS-CoV-2. We established a threshold value as an independent predictor. This analysis was conducted during the initial wave of the SARS-CoV-2 pandemic in France and involved patients who were infected with the virus for the first time. Subsequent to the first wave, point-of-care testing using nasopharyngeal dry swabs was directly implemented in the emergency ward to enhance patient care and optimize bed management (16). Consequently, this prevented the possibility of conducting further analyses on the same sample. It is imperative to corroborate these findings using current SARS-CoV-2 variants and after SARS-CoV-2 vaccination or prior infection, as well as in the context of other acute respiratory viral infections.
Prior studies have documented the correlation between the detection and quantification of TTV and viral respiratory tract infections caused by SARS-CoV-2 and other viruses. In a study conducted before the COVID-19 pandemic, involving children with acute respiratory diseases, Maggi et al. noted that TTV was more frequently detected and at higher levels in nasal secretions of patients with bronchopneumonia compared to those with milder symptoms (8). In an investigation into the respiratory microbiome and virome signatures associated with the severity of COVID-19 infection, Merenstein et al. discovered that within a week of admission, anelloviridae were more prevalent and present in higher titers in patients with severe disease (17). Furthermore, a recent study also observed that viruses from the anelloviridae family were significantly more abundant in samples from deceased and hospitalized patients in comparison to those from ambulatory individuals (18). Conversely, in a study that compared TTV plasma loads over a two-week period between severe and mild-moderate SARS-CoV-2 cases, Solis et al. demonstrated that a TTV DNA load lower than 700 copies/mL was linked to a higher risk of severe COVID-19. However, this association was observed at a time when lymphocyte counts were notably lower in severe cases during the second week after symptom onset (19).
Collectively, the growing body of evidence suggests that anellovirus reactivation is linked to an inadequate cellular antiviral response, and the replication of TTV within the respiratory tract might reflect respiratory immune deficiency. Detecting and quantifying TTV could serve as markers for predicting the severity of acute viral respiratory infections.