Replication of TT virus in hepatocyte and leucocyte cell lines

Abstract

The TT virus (TTV) is a non-enveloped, single-stranded, circular, DNA virus, first isolated from a patient with hepatitis of unexplained etiology. The much deliberated pathological role of the virus continues to be conjectural in the absence of a suitable in vitro replication model. So far, the liver and the bone marrow have been shown to be the main sites of TTV replication. In this study, the human cell lines HepG2 and Chang Liver, the rat hepatoma cell line MH1C1, phytohemagglutinin (PHA)-stimulated TTV-negative peripheral blood mononuclear cell (PBMC) cultures and the B lymphoblast cell line, Raji were investigated as potential in vitro replication systems for TTV. The cell lines were infected with an inoculum prepared by pooling TTV genotype1 DNA positive sera and monitored for virus replication. Of the three hepatocyte cell lines, while the HepG2 and MH1C1 cell lines did not support TTV replication, the Chang Liver cell line showed clear morphological changes as a result of the in vitro infection, which included clumping and granular degeneration of the entire cell sheet over a period of 6 days. The infected cells also showed presence of virus-specific mRNA representative of viral transcription. The consistent presence of infectious viral particles in the supernatant culture fluid at 24-hr fluid replacement intervals indicated limited extra-cellular release of viral particles. The PHA-stimulated TTV-negative PBMC cultures and the Raji cell line were also able to support TTV replication and released significant levels of infectious viral particles into the supernantant culture fluid.

Progression towards AIDS leads to increased torque teno virus and torque teno minivirus titers in tissues of HIV infected individuals

“…Peripheral blood mononuclear cells (PBMCs) were thought to act as a reservoir for TTV but double stranded intermediates have not been isolated from these cells suggesting that this is not a site of replication [Okamoto et al, 2000b]. However, TTV replication has been achieved in vitro by stimulation of PBMCs with phytohemagglutinin, lipopolysaccharide, and interleukin-2 [Mariscal et al, 2002;Desai et al, 2005]. Similar titers of TTV/TTMV in bone marrow and spleen suggests either the spleen is also a site of replication or the infiltration of spleen by cell types supporting replication.…”

Torque teno virus (TTV): current status

“…There are no reports of a culture system to support the replication of TTV effectively, except for the minimal growth in PBMC and Chang liver cells [48,53]. However, most of the TTV sequences reported in the database possessed a common arrangement of frameworks and continuous open reading frames.…”

“…Moreover, the TTV þ signal disappeared in PBMCs after degradation of ssDNA by mung bean nuclease [51]. In the study by Desai et al [48], PBMCs stimulated with PHA and also Raji cells transiently supported virus replication. But as before, quantitative analysis of these observations is lacking.…”

“…Desai et al [48] recently reported that the Chang liver cell line showed clear morphological changes following in vitro infection with genotype 1a virus samples. They claimed that infectivity with the culture supernatant could be transferred into neighbouring cultures.…”

TT virus in peripheral blood cells from patients with human papillomavirus (HPV): investigating association with cervical carcinoma

“…Certain endogenous and exogenous factors can act as cofactors by influencing the risk of HPV persistence and cancer progression. TTV replication has been demonstrated in hepatocyte and leukocyte cell lines (Desai et al 2005). Barril et al (2000) observed the presence of TTV in serum and peripheral mononuclear cells from continuous ambulatory peritoneal dialysis using primers for the ORF1 and ORF 2 regions of TTV.…”