INTRODUCTION
SARS-CoV-2 infection is associated with a significant rate of severe disease requiring intensive care (1,2). While various risk factors have been identified (3), severe illness can affect anyone, the potential for severe illness extends to a broad range of individuals, and reliable individual biological markers to predict unfavorable outcomes remain lacking. The severity depends, in particular, on an inefficient and unbalanced immune response. The severity of the disease is notably influenced by an inadequate and imbalanced immune response. Firstly, an insufficient interferon response contributes to uncontrolled SARS-CoV-2 replication (4), and secondly, an overactive proinflammatory response results in damage to respiratory epithelial cells (5).
Anelloviridae, a family of non-enveloped single-stranded DNA viruses, persistently inhabit various compartments within infected hosts, constituting a significant component of the human virome (6). Torque teno virus (TTV), belonging to the Alphatorquevirus genus, ranks among the most prevalent anelloviruses in humans (7). TTV is not associated with any specific disease. However, its presence in blood is indicative of cellular immune function, and TTV load is currently being investigated in clinical trials for adjusting immunosuppression in solid organ transplant cases to prevent opportunistic infections and graft rejection.
The respiratory tract stands as a hypothesized primary entry site for initial infection and serves as a frequent shedding source (8). TTV is detectable in respiratory samples from nearly all individuals. Elevated viral loads have been correlated with lung impairment in patients with respiratory conditions such as asthma (9) and linked to respiratory bacterial dysbiosis in lung transplant recipients (10).
Given its affinity for the respiratory mucosa and its connection with cellular immunity, our study aimed to ascertain whether the assessment of TTV levels in nasopharyngeal samples upon admission to the emergency ward could serve as a predictive indicator for identifying the potential risk of severe disease in patients infected with SARS-CoV-2.