Development of an Immunoassay for Detection of Torque Teno Virus (TTV) Antibodies Using the N22 Expression Product from TTV Genotype 2.

AIMS

This study describes an immunoassay to detect anti-torque teno virus (TTV) antibodies using a peptide obtained from expression of the N22 region of TTV genotype 2.

METHODS

The N22 region (∼500 bp) of TTV genotype 2 was cloned in a pET-28a(+) vector and expressed in ZYM-5052 autoinduction medium. Following metal affinity chromatography, a purified polypeptide was used as an antigen for the development of an immunoassay to detect anti-TTV antibodies in human sera.

RESULTS

Recombinant protein (∼25-kDa) was obtained after 24 h of incubation at 25°C in ZYM-5052 autoinduction medium. A blot assay developed using this polypeptide as an antigen and TTV-positive sera as the primary antibody produced a distinct spot on the nitrocellulose membrane. Serum samples from 36 of 42 patients with renal disease and 29 of 48 patients with liver diseases produced a positive signal using this immunoassay. Simultaneously, 18 of 48 healthy controls were also detected to be positive for anti-TTV antibodies. These results were found to be comparable with TTV detection using PCR, and the assay showed a high sensitivity and specificity (i.e., 97.44 and 91.67%, respectively). Moreover, this assay could detect TTV infection irrespectively of the genotype, including cases of mixed infection.

CONCLUSION

The present immunoassay using the N22 expression product may be used as an alternative to PCR to detect TTV infection in large populations.