Estimation of the infectious viral load required for transfusion-transmitted human T-lymphotropic virus type 1 infection (TT-HTLV-1) and of the effectiveness of leukocyte reduction in preventing TT-HTLV-1.
OBJECTIVE
The risk of transfusion-transmitted human T-lymphotropic virus type 1 infection (TT-HTLV-1) after prestorage leucocyte reduction (LR) remains unknown, as the proviral load in the blood component that would cause TT-HTLV-1 is undetermined. On the basis of the distribution of HTLV-1 proviral load among HTLV-1-sero-positive blood donors, we attempted to estimate the proviral load for transfusion-related infectivity. We also discuss the effectiveness of LR in preventing TT-HTLV-1.


METHODS
The HTLV-1 proviral load in 300 HTLV-1-sero-positive blood donors was determined by real-time polymerase chain reaction analysis. The proviral load required for transfusion-related infectivity was estimated using historical TT-HTLV-1 frequency data from a retrospective study on patients who had received blood from HTLV-1-sero-positive blood donors and the distribution pattern of HTLV-1 proviral load among blood donors.


RESULTS
HTLV-1 proviral loads ranged between < 0.01 and 25.0 copies per 100 leucocytes. Historical data showed TT-HTLV-1 frequency to be 80%. Assuming that 80% of the 300 sero-positive samples are infectious, it is estimated that the transfer of ≥ 9 × 10(4) cells containing the HTLV-1 provirus is required to establish TT-HTLV-1.


CONCLUSIONS
The residual number of HTLV-1-infected cells after LR is substantially lower than the viral load necessary for TT-HTLV-1. LR therefore appears to be effective in minimizing the incidence of TT-HTLV-1.
Central Blood Institute, Blood Service Headquarters, Japanese Red Cross Society, Tokyo, Japan.
R
R
Sobata
Central Blood Institute, Blood Service Headquarters, Japanese Red Cross Society, Tokyo, Japan.
C
C
Matsumoto
Central Blood Institute, Blood Service Headquarters, Japanese Red Cross Society, Tokyo, Japan.
S
S
Uchida
Japanese Red Cross Kanto-Koshinetsu Block Blood Center, Tokyo, Japan.
Y
Y
Suzuki
Central Blood Institute, Blood Service Headquarters, Japanese Red Cross Society, Tokyo, Japan.
M
M
Satake
Central Blood Institute, Blood Service Headquarters, Japanese Red Cross Society, Tokyo, Japan.
K
K
Tadokoro
D000293:Adolescent; D000328:Adult; D004279:DNA, Viral / Q000097:blood; D005260:Female; D015490:HTLV-I Infections / Q000517:prevention & control* / Q000635:transmission; D015368:Human T-lymphotropic virus 1 / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D006801:Humans; D047589:Leukocyte Reduction Procedures; D008297:Male; D008875:Middle Aged; D065227:Transfusion Reaction; D019562:Viral Load
D004279:DNA, Viral
HTLV-1; leucocyte reduction; proviral load; transfusion; transfusion-transmitted infection