TT virus infection: prevalence of elevated viraemia and arguments for the immune control of viral load.
BACKGROUND
The most recent polymerase chain reaction (PCR) detection protocols for the TT virus (TTV) permit one to identify the presence of viral DNA in the serum of a majority of healthy individuals, in the absence of any particular risk factor. This is in contrast with previous epidemiological studies that reported a higher prevalence of TTV infection in populations such as haemodialysis patients (HD), haemophiliacs, intravenous drug users or diabetics.


OBJECTIVE
To show that these discrepant results were due to the different sensitivity (number of viral copies detected) of the detection protocols used in initial and more recent epidemiological studies.


RESULTS
We designed a standardised primary PCR assay that detects only viraemia >5x10(3) to 5x10(4) copies/ml for genotypes 1, 2 and 3, and compared the results of this test with those of a nested PCR assay which is 100-fold more sensitive. Viraemia >5x10(3) to 5x10(4) copies/ml were statistically more frequent in HD patients (54.3%), diabetics (54.7%), and HIV-infected patients with CD4 cells <200/mm(3) (69%) than in blood donors (37%) or HIV-infected patients with CD4 cells >500/mm(3) (33%).


CONCLUSIONS
These data suggest a possible relationship between the prevalence of elevated viral loads and the level of immunocompetence of the populations studied, and therefore that of an immune control of TTV viraemia. This corroborates previous findings showing that the stimulation of the immune system by an interferon treatment was able to clear TTV viraemia.
Touinssi
M
M
Unité des Virus Emergents, Laboratoire de Virologie Moléculaire, Tropicale et Transfusionnelle, Faculté de Médecine de Marseille, Boulevard Jean Moulin, 13385 Marseille cedex 05, France.
Gallian
P
P
Biagini
P
P
Attoui
H
H
Vialettes
B
B
Berland
Y
Y
Tamalet
C
C
Dhiver
C
C
Ravaux
I
I
De Micco
P
P
De Lamballerie
X
X
D000328:Adult; D001782:Blood Donors; D018791:CD4 Lymphocyte Count; D004266:DNA Virus Infections / Q000150:complications / Q000453:epidemiology* / Q000276:immunology / Q000821:virology*; D004279:DNA, Viral / Q000097:blood; D048909:Diabetes Complications; D005260:Female; D015658:HIV Infections / Q000150:complications; D015497:HIV-1; D006801:Humans; D007121:Immunocompetence; D016867:Immunocompromised Host; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D015995:Prevalence; D006435:Renal Dialysis; D012680:Sensitivity and Specificity; D022783:Torque teno virus / Q000276:immunology / Q000302:isolation & purification / Q000502:physiology*; D019562:Viral Load; D014766:Viremia / Q000453:epidemiology / Q000821:virology*
D004279:DNA, Viral