Prevalence of TT viral DNA in italian blood donors with and without elevated serum ALT levels: molecular characterization of viral DNA isolates.
OBJECTIVE
A novel non-enveloped DNA virus, called TT virus (TTV), has been reported to be associated with post-transfusion hepatitis of unknown etiology. Although its clinical role still remains obscure, its presence in blood donations might cause problems. It, therefore, appeared of interest to investigate TTV prevalence in voluntary blood donors.


METHODS
A total of 595 Italian blood donors with and without elevated serum alanine aminotransferase (ALT) levels were tested by polymerase chain reaction using two sets of semi-nested primers that amplify the well-known region in the N22 clone. The amplified products were then sequenced to assess the genotype by phylogenetic and restriction fragment length polymorphism analyses.


RESULTS
The prevalence of TTV in blood donors was 5+/-1.9% (25 out of 500) with a 95% confidence limit. A similar prevalence was found in 95 selected blood donors with increased ALT levels. A viral load of 10(3)-10(4) viral DNA molecules/mL was found, thus indicating a rather narrow range of variability. A phylogenetic tree built up on the basis of 210 base sequences of ORF1 allowed isolates to be classified into 2 groups corresponding, at least, to two of the putatives TTV genotypes, group 1 and group 2 of Okamoto's classification. A similar classification was also obtained by site restriction enzyme analysis.


CONCLUSIONS
The results show that TTV infection is present among Italian blood donors. No significant difference in prevalence of TTV infection was found between patients with normal and increased ALT, making the association between TTV infection and human hepatitis questionable.
Pisani
G
G
Laboratory of Immunology, Istituto Superiore di Sanità, Rome; degrees National Blood Transfusion Center, Italian Red Cross, Rome, Italy.
Antigoni
I
I
Bisso
G
G
Wirz
M
M
Iudicone
P
P
Miceli
M
M
Gentili
G
G
D000293:Adolescent; D000328:Adult; D000368:Aged; D000410:Alanine Transaminase / Q000097:blood*; D001782:Blood Donors; D004267:DNA Viruses / Q000235:genetics / Q000302:isolation & purification*; D004279:DNA, Viral / Q000032:analysis* / Q000235:genetics; D005260:Female; D006525:Hepatitis, Viral, Human / Q000453:epidemiology; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D010802:Phylogeny
D004279:DNA, Viral; D000410:Alanine Transaminase