Evaluation of Line Immunoassay to Detect HTLV-1 Infection in an Endemic Area, Southwestern Japan; Comparison with Polymerase Chain Reaction and Western Blot.
BACKGROUND
Human T-lymphotropic virus type 1 (HTLV-1) has been recognized as a cause of adult T-cell leukemia/lymphoma, HTLV-1-associated myelopathy/tropical spastic paraparesis, and HTLV-1-associated uveitis. HTLV-1 infection is normally detected by screening for HTLV-1 antibodies, and positive samples are confirmed by Western blot (WB). However, WB fails to confirm some samples that were positive for HTLV-1 antibodies on screening. Line immunoassay (LIA) is commonly used in Europe and Brazil, but not in Japan. Therefore, we evaluated the performance of LIA as a method of confirming HTLV-1 antibodies using samples in Japan.


METHODS
LIA was compared with polymerase chain reaction (PCR) and WB using 50 negative and 70 positive samples tested by chemiluminescent enzyme immunoassay (CLEIA) in Miyazaki, Japan, an HTLV-1 endemic area. LIA (INNO-LIA HTLVI/II Score) and WB (Problot HTLV-I) were performed according to the manufacturer's instructions. Real-time PCR for HTLV-1 pX region was performed using DNA derived from white blood cells. The samples that tested negative by real-time PCR were further tested by nested PCR.


RESULTS
All 50 CLEIA negative samples were determined to be negative by LIA and PCR. Of the 70 positive samples, 66 tested positive by both of LIA and PCR. Three samples tested negative by LIA and PCR, and the remaining sample (PCR negative) showed non-specific staining in LIA and WB. WB showed more indeterminate results than LIA. Gp21 antibody in LIA demonstrated a high ability to discriminate between positive and negative PCR results. Furthermore, the degree of gp21 antibody reaction by LIA showed correlation with HTLV-1 proviral loads (PVLs).


CONCLUSIONS
Our results indicate that LIA performs well in confirming HTLV-1 seropositivity by showing a low incidence of indeterminate results and good agreement with PCR using samples in Japan, although the number of samples tested was small. In addition, semi-quantitative antibody titer to gp21 correlated well with HTLV-1 PVLs. Further study including larger samples is necessary to determine the positioning of LIA for HTLV-1 detection in Japan.
Kazumi
K
Umeki
Kunihiko
K
Umekita
Yuuki
Y
Hashikura
Ikuo
I
Yamamoto
Kazuyoshi
K
Kubo
Yasuhiro
Y
Nagatomo
Akihiko
A
Okayama
D000914:Antibodies, Viral / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D015153:Blotting, Western; D004279:DNA, Viral / Q000097:blood / Q000235:genetics; D019353:Endemic Diseases; D015490:HTLV-I Infections / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology; D015368:Human T-lymphotropic virus 1 / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007124:Immunoenzyme Techniques; D007564:Japan / Q000453:epidemiology; D011237:Predictive Value of Tests; D060888:Real-Time Polymerase Chain Reaction; D015203:Reproducibility of Results; D012698:Serologic Tests; D019562:Viral Load; D054299:env Gene Products, Human Immunodeficiency Virus / Q000276:immunology*
D000914:Antibodies, Viral; D015415:Biomarkers; D004279:DNA, Viral; D054299:env Gene Products, Human Immunodeficiency Virus; C055265:gp21 protein, Human T-lymphotropic virus 1