Understanding torquetenovirus (TTV) as an immune marker

Abstract

Torquetenovirus (TTV), a small, single stranded anellovirus, is currently being explored as a marker of immunocompetence in patients with immunological impairment and inflammatory disorders. TTV has an extremely high prevalence and is regarded as a part of the human virome, the replication of which is controlled by a functioning immune system. The viral load of TTV in plasma of individuals is thought to reflect the degree of immunosuppression. Measuring and quantifying this viral load is especially promising in organ transplantation, as many studies have shown a strong correlation between high TTV loads and increased risk of infection on one side, and low TTV loads and an increased risk of rejection on the other side. As clinical studies are underway, investigating if TTV viral load measurement is superior for gauging antirejection therapy compared to medication-levels, some aspects nevertheless have to be considered. In contrast with medication levels, TTV loads have to be interpreted bearing in mind that viruses have properties including transmission, tropism, genotypes and mutations. This narrative review describes the potential pitfalls of TTV measurement in the follow-up of solid organ transplant recipients and addresses the questions which remain to be answered.

The assessment of microbial infection in children with autism spectrum disorders and genetic folate cycle deficiency

“…The microbial profile of the SG children was dominated by the microorganisms currently considered the most typical triggers of immune-dependent complications, including immune-mediated disorders of the central nervous system [ 18 , 20 ]. Therefore, it is necessary to identify microbial agents in children with ASD.…”

“…These infectious agents include herpesviruses of various types [ 11 – 13 ], Beta-hemolytic Group A Streptococcus [ 14 ], Вorrelia burgdorferi [ 15 ], Yersinia enteroсolitica [ 10 ], Candida albicans [ 16 ], Mycoplasma and Chlamydia pneumoniae [ 11 ], and Toxoplasma gondii [ 17 ]. At the same time, scientists have not studied infection with some other opportunistic pathogens common in the human population, such as TTV [ 18 ], in children with ASD.…”

The Impact of First-Time SARS-CoV-2 Infection on Human Anelloviruses

“…In solid organ transplantation, a careful fine-tuning of immunosuppressive treatment is important to either prevent allograft rejection due to insufficient immunosuppression or to prevent infections in the case of excessive immunosuppression. It has been postulated that the pre- and post-transplantation comparison of TTV concentrations in blood and the examination of the rise in TTVs in the first two years after transplantation can guide immunosuppressive treatment dosing [ 21 , 22 ]. In the same line of thinking, one would expect, in an immunocompetent situation, the concentrations of human anelloviruses to decrease when immunity is activated, for instance during an acute respiratory infection.…”

Respiratory torque teno virus load at emergency department visit predicts intensive care unit admission of SARS‐CoV‐2 infected patients

“…TTV is not associated with any specific disease. However, its presence in blood is indicative of 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 8–11 …”

“…However, its presence in blood is indicative of 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. [8][9][10][11] The respiratory tract stands as a hypothesized primary entry site for initial infection and serves as a frequent shedding source. 12 TTV is detectable in respiratory samples from nearly all individuals.…”