B-080 Analytical Performance of ESPLINE HTLV-I/II
Authors: Kin A , Yamakawa K , Kojima S , Kaneko A , Aoyagi K 
Published: September 2023

Abstract

Background
The human T-cell lymphotropic virus (HTLV) infects a type of white blood cell called T-cell or T-lymphocyte. There are two types of HTLV, HTLV-I and HTLV-II, which are closely related to human C retroviruses. HTLV-I is endemic in the Caribbean, Japan, South America, and parts of Africa. HTLV-I has been recognized as a cause of adult T-cell leukemia (ATL) and HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-II is found among Africa and the Americas, and injecting drug users in many cities of Western Europe and North America. Currently, an effective vaccine against HTLV is not available, and clinical treatment is limited. The diagnosis and identification of patients are very important for controlling the spread of HTLV infection. There are HTLV-infected lymphocytes in the peripheral blood of patients, but little virus in the serum or plasma can be detected. Therefore, screening tests for HTLV that generally detect antibodies using reagents need dedicated instruments. We have developed an anti-HTLV-I/II reagent ( ESPLINE HTLV-I/II) based on the immunochromatography principal using an enzyme immunometric assay that can easily detect both anti-HTLV-I and anti-HTLV-II antibodies in serum and plasma. This report evaluates its efficacy.

Methods
This reagent has a test line coated with a recombinant protein and peptides derived from three env gene proteins (HTLV-I gp21, HTLV-I gp46, and HTLV-II gp46) to detect anti-HTLV-I/II antibodies. The antibodies in the sample bind to antigens labelled with alkaline phosphatase (ALP), and then immunocomplexes are formed. These complexes are captured by the antigens on the test line, and the blue line is detected by ALP enzymatic reaction with a colorimetric substrate. It only takes 15 minutes to obtain the results without any instruments. To evaluate the fundamental performance, we tested specificity, limit of detection, and method comparison with Lumipulse HTLV-I/II, Lumipulse Presto HTLV-I/II, and Serodia HTLV-I, following the CLSI protocol. Commercially available serum and/or plasma were used for most evaluations.

Results
Regarding specificity, 1014 anti-HTLV-I/II negative serum samples, which were confirmed by highly sensitive CLEIA Lumipulse Presto HTLV-I/II, were tested by ESPLINE HTLV-I/II. Then, all 1014 samples were shown as nonreactive, demonstrating a specificity of 100.0%. Regarding the limit of detection, by the analysis of serial dilution from 2 positive plasma specimens, ESPLINE HTLV-I/II assay showed high sensitivity compared to conventional Serodia HTLV-I. Regarding the method comparison, 57 anti-HTLV-I and 30 anti-HTLV-II positive plasma samples from different individuals were tested. All samples showed positive results with ELPLINE HTLV-I/II, Lumipulse Presto HTLV-I/II, Lumipulse G HTLV-I/II, and conventional Particle Agglutination Serodia HTLV-I.

Conclusion
The novel anti-HTLV-I and anti-HTLV-II antibodies assay, ESPLINE HTLV-I/II, showed higher sensitivity than Particle Agglutination Serodia HTLV-I and had good concordance with highly sensitive CLEIA Lumipulse Presto HTLV-I/II and Lumipulse G HTLV-I/II. The ESPLINE system can be used easily to complete an assay in 15 min. This procedure is considered useful in situations such as on-site tests at health centers, screening tests at medical institutions with a small number of specimens, and other emergency tests.