Determination and phylogenetic analysis of partial sequences from TT virus isolates

Area of Science:

• Virology
• Molecular Biology
• Infectious Diseases

Background:

• The TT virus (TTV) is a widespread human virus with a largely unknown clinical significance.
• Understanding TTV genetic diversity is crucial for tracking its transmission and evolution.

Purpose of the Study:

• To analyze the genetic variability of the TT virus (TTV) in French in-patients.
• To identify and classify different TTV genotypes and assess the potential for chronic infection.

Main Methods:

• Polymerase chain reaction (PCR) with degenerate primers in ORF1 was used to detect the TTV genome in patient sera.
• Sequencing of TTV isolates and phylogenetic analysis were performed to determine genetic relationships.
• Longitudinal follow-up of haemodialysis patients was conducted to assess chronic infection.

Main Results:

• High genetic variability was observed among TTV isolates, with up to 47% difference in amino acid sequences.
• Phylogenetic analysis identified three main groups, corresponding to genotypes 1, 2, and a newly identified genotype 3.
• Distinct genotypes were defined by a genetic distance > 27%; no clear criteria for sub-types were found.
• Chronic TTV infection was confirmed in haemodialysis patients over a 15-31 month period.
• One patient was found to be co-infected with two different TTV genotypes simultaneously.
• Viral sequences in ORF1 and ORF2 remained stable for a given strain during follow-up.

Conclusions:

• TTV exhibits significant genetic diversity, necessitating the definition of new genotypes.
• Chronic TTV infection is possible, particularly in immunocompromised individuals like haemodialysis patients.
• The study highlights the complexity of TTV infection, including the potential for co-infection with multiple genotypes.