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Other Single-Stranded DNA Viruses
Published in Paul Pumpens, Peter Pushko, Philippe Le Mercier, Virus-Like Particles, 2022
Paul Pumpens, Peter Pushko, Philippe Le Mercier
By analogy with the Circoviridae family of the order Cirlivirales described in Chapter 10, the family Anelloviridae is comprised of animal viruses with circular ssDNA genomes, including well-studied chicken anemia virus (CAV) of the Chicken anemia virus species of the genus Gyrovirus. The latter was transposed recently from the Circoviridae family to the Anelloviridae family. Figure 10.1 presents the first 3D view of CAV in comparison with the true circovirus. Generally, according to the ICTV report (Biagini et al. 2012) and current ICTV taxonomy, the large Anelloviridae family is composed of 31 genera and 155 species altogether. The virions are nonenveloped, T = 1 icosahedra, with reported diameters of about 30 nm for torque teno viruses (TTVs, genus Alphatorquevirus) and torque teno mini viruses (TTMVs, genus Betatorquevirus). The virions contain a single molecule of circular negative-sense ssDNA, which ranges from about 2 to about 3.9 kb in size, where the ORF1 is believed to encode the putative capsid protein and replication-associated protein of human and animal anelloviruses (Biagini et al. 2012).
Viruses
Published in Loretta A. Cormier, Pauline E. Jolly, The Primate Zoonoses, 2017
Loretta A. Cormier, Pauline E. Jolly
Alphatorquevirus is a recently discovered genus in the recently established family of Anelloviridae which includes the torque teno virus (TTV) species (Kekarainen and Segalés 2012). TTV viruses have been identified in dogs, cats, nonhuman primates, and wild and domesticated swine (Ssemadaali et al. 2016). TTV is a ubiquitous virus, found in water and sewage, in the air, and on surfaces; infection occurs in all major organs, secretions, excretions, and the blood (Ssemadaali et al. 2016). TTV has a high prevalence in the human population, is typically asymptomatic, and may be a commensal (Béland et al. 2014). In one study of 205 Japanese children aged 1–12, over 98% were positive at two years of age (Ninomiya et al. 2008). However, TTV can be an opportunistic co-infection with a variety of afflictions, including viral hepatitis, asthma, autoimmune disorders, and respiratory illnesses (Ssemadaali et al. 2016). It has also been associated with post-trans-fusion and organ transplant infections (Béland et al. 2014). Two additional Alphatorqueviruses have been identified in humans: TTMV (torque teno mini virus) and TTMDV (torque teno midi virus) (Ninomiya et al. 2009). Wild and domesticated pigs are frequently infected with TTVSuV (torque teno sus virus), which has been transmitted zoonotically to humans through contact with pork products (Ssemadaali et al. 2016).
Predictive tools to determine risk of infection in kidney transplant recipients
Published in Expert Review of Anti-infective Therapy, 2020
Mario Fernández-Ruiz, Francisco López-Medrano, José María Aguado
First isolated in 1997, torque teno virus (TTV) belongs to the genus Alphatorquevirus within the Anelloviridae family. Anelloviruses are small, non-enveloped, single-stranded DNA viruses which account for about 70% of human blood virome. TTV prevalence exceeds 70–80% in the general population of most developed and developing countries. Anelloviruses exhibit a high degree of genetic heterogeneity, similar to that observed among RNA viruses. Originally thought to cause hepatitis, TTV is currently considered an orphan virus [97]. Although TTV replication has been associated with various pro-inflammatory conditions, such as sepsis [98], cancer [99] or chronic pulmonary diseases [100], higher viremia levels are found in immunocompromised populations such as allogeneic hematopoietic stem-cell transplant recipients [101], HIV patients (with an inverse correlation with CD4+ T-cell counts) [102], or those with primary immunodeficiencies [103] or receiving biological therapies [104]. The plausibility and feasibility of monitoring TTV DNAemia to assess post-transplant immunocompetence are supported by the fact that viral replication is not influenced by the administration of valganciclovir prophylaxis and by the recent introduction of commercial real-time PCR assays targeting a highly conserved segment of the 5ʹ untranslated region of the viral genome [105].
Quantification of torque teno virus (TTV) DNA in saliva and plasma samples in patients at short time before and after kidney transplantation
Published in Journal of Oral Microbiology, 2022
Alexandre Mendes Batista, Matheus W. Caetano, Maria A. Stincarelli, Ana C. Mamana, Rodrigo Melim Zerbinati, Dmitry J. S. Sarmento, Marina Gallottini, Rafael A. V. Caixeta, José Medina-Pestana, Bengt Hasséus, Louise Zanella, Tania R. Tozetto-Mendoza, Simone Giannecchini, Paulo H. Braz-Silva
TTV is a naked, small virus with circular single-strand DNA genome, discovered in 1997 [5,6], comprising to date at least 29 genetically different species included in the genus Alphatorquevirus within the Anelloviridae family [7–9]. TTV possesses several characteristics, such as its presence as a main virus of the human virome, high viral load in immunosuppressed patients compared to healthy ones, considerable genetic diversity and lack of association with any human illness [8–11].
Convalescent plasma therapy in COVID-19: Unravelling the data using the principles of antibody therapy
Published in Expert Review of Respiratory Medicine, 2023
Arturo Casadevall, Michael J. Joyner, Liise-Anne Pirofski, Jonathon W. Senefeld, Shmuel Shoham, David Sullivan, Nigel Paneth, Daniele Focosi
In the early days of the COVID-19 pandemic, there was considerable concern that the administration of CCP to patients with COVID-19 would be detrimental by triggering antibody-dependent enhancement (ADE) and/or cytokine storm [37,38]. A further concern was that antibody administration might diminish the magnitude of the endogenous immune response and suppress antibody production [37]. The concern about ADE and unintentional worsening of COVID-19 was alleviated by early observational studies that in the first 5,000 patients treated as part of the US Convalescent Plasma Study conducted under the auspices of the expanded access program (EAP) of the U.S.A. [39], and then in the first 20,000 patients [40], and finally in 105,000 patients [41], which showed it was as safe as regular plasma. Later, RCTs comparing the outcome of CCP in early post-exposure prophylaxis [42], early outpatient treatment and also hospitalized patients found no evidence of toxicity and concluded that its use in COVID-19 was safe [43], dispelling concerns about ADE in clinical use. Additionally, antibodies in CCP show no evidence of producing ADE in laboratory studies [44] and those that promote infection in macrophages do not trigger the production of pro-inflammatory cytokines [45]. Hence, early concerns about ADE were countered by voluminous clinical evidence and experience. The concern that CCP administration to patients with COVID-19 would interfere with or attenuate the development of endogenous immune responses was dispelled by the finding that there were no effects on the adaptive immune response between CCP and control recipients in an RCT [46]. Theoretical concerns about the inadvertent transfer of viruses in CCP not routinely screened by mandatory testing was lessened by a metagenomic virome analysis that showed no known pathogenic DNA or RNA viruses, although it did demonstrate Anelloviridae sequences, which are ubiquitous in human blood and not currently associated with human disease [47]. Given that the pathogenesis of COVID-19 involves coagulation disorders, there was also the concern that CCP administration could promote strokes but there has been no evidence for this [48]. Early in the pandemic it was discovered that some individuals with severe COVID-19 had antibodies to type 1 interferons [49], and it was suggested that if they were found in CCP they might mediate deleterious effects. However, an analysis of the outcome of CCP transfusion found no evidence for this concern even among individuals who received units containing these antibodies [32]. A one-year follow-up analysis of CCP recipients and controls from an RCT in Germany revealed no long-term concerns and the data showed a trend toward improved survival and health that approached statistical significance (p = 0.08) and reached statistical significance in a pre-defined subgroup that received high antibody titer plasma [50]. Hence, the safety of CCP is established.