Evaluation of <i>HTLV‐1 HBZ</i> and proviral load, together with host <i>IFN λ3</i>, in pathogenesis of HAM/TSP

<jats:sec><jats:label /><jats:p>Human T‐cell lymphotropic virus 1 (HTLV‐1) is associated with two progressive diseases: HTLV‐1‐associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T‐cell leukemia/lymphoma (ATLL). Although HTLV‐1 proviral load (PVL) has been introduced as a risk factor for these diseases’ progression, it is not sufficient on its own to yield an accurate estimation of the outcome of the infection. In the present study, PVL and <jats:italic>HTLV‐1 basic leucine zipper factor (HBZ)</jats:italic> expression level as viral factors, and <jats:italic>IFN λ3</jats:italic> as a host factor, were evaluated in HAM/TSP patients and HTLV‐1 asymptomatic carriers (ACs). During 2014–2015, 12 HAM/TSP patients and 18 ACs who had been referred to the HTLV‐1 Clinic, Ghaem Hospital, Mashhad University of Medical Sciences (MUMS), Mashhad, Iran, were enrolled in this study. Peripheral blood mononuclear cells (PBMCs) were isolated and the DNA and mRNA were extracted for quantification of <jats:italic>HBZ, IFN λ3</jats:italic> expression, and PVL using real‐time PCR (TaqMan method). Although the PVL was higher in the HAM/TSP group, with a 94% confidence interval, there were no considerable differences in terms of <jats:italic>HBZ</jats:italic> mRNA and PVL between ACs and HAM patients. <jats:italic>IFN λ3</jats:italic> expression in the HAM/TSP group was significantly higher than in the ACs (<jats:italic>P</jats:italic> = 0.02). To the best of our knowledge, no study has evaluated the expression level of <jats:italic>IFN λ3</jats:italic> in HTLV‐1 positive patients. The immune response against HTLV‐1 viral antigens and virulent factors will therefore further refine our knowledge of interactions between the virus and host in the pathogenesis of HTLV‐1‐related disorders. The virus PVL and the host <jats:italic>IFN λ3</jats:italic> can be used as pathogenic factors of HTLV‐1 infected patients at risk of HAM/TSP manifestation. <jats:bold><jats:italic>J. Med. Virol. 89:1102–1107, 2017</jats:italic>.</jats:bold> © 2016 Wiley Periodicals, Inc.</jats:p></jats:sec>