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Branda F, Romano C, Pavia G, Bilotta V, Locci C, Azzena I, Deplano I, Pascale N, Perra M, Giovanetti M, Ciccozzi A, De Vito A, Quirino A, Marascio N, Matera G, Madeddu G, Casu M, Sanna D, Ceccarelli G, Ciccozzi M, Scarpa F. Human T-Lymphotropic Virus (HTLV): Epidemiology, Genetic, Pathogenesis, and Future Challenges. Viruses 2025; 17:664. [PMID: 40431676 PMCID: PMC12115942 DOI: 10.3390/v17050664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2025] [Revised: 04/24/2025] [Accepted: 04/25/2025] [Indexed: 05/29/2025] Open
Abstract
Human T-lymphotropic viruses (HTLVs) are deltaretroviruses infecting millions of individuals worldwide, with HTLV-1 and HTLV-2 being the most widespread and clinically relevant types. HTLV-1 is associated with severe diseases such as adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), while HTLV-2 shows a lower pathogenic potential, with occasional links to neurological disorders. HTLV-3 and HTLV-4, identified in Central Africa, remain poorly characterized but are genetically close to their simian counterparts, indicating recent zoonotic transmission events. HTLVs replicate through a complex cycle involving cell-to-cell transmission and clonal expansion of infected lymphocytes. Viral persistence is mediated by regulatory and accessory proteins, notably Tax and HBZ in HTLV-1, which alter host cell signaling, immune responses, and genomic stability. Integration of proviral DNA into transcriptionally active regions of the host genome may contribute to oncogenesis and long-term viral latency. Differences in viral protein function and intracellular localization contribute to the distinct pathogenesis observed between HTLV-1 and HTLV-2. Geographically, HTLV-1 shows endemic clusters in southwestern Japan, sub-Saharan Africa, the Caribbean, South America, and parts of the Middle East and Oceania. HTLV-2 is concentrated among Indigenous populations in the Americas and people who inject drugs in Europe and North America. Transmission occurs primarily via breastfeeding, sexual contact, contaminated blood products, and, in some regions, zoonotic spillover. Diagnostic approaches include serological screening (ELISA, Western blot, LIA) and molecular assays (PCR, qPCR), with novel biosensor and AI-based methods under development. Despite advances in understanding viral biology, therapeutic options remain limited, and preventive strategies focus on transmission control. The long latency period, lack of effective treatments, and global neglect complicate public health responses, underscoring the need for increased awareness, research investment, and targeted interventions.
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Affiliation(s)
- Francesco Branda
- Unit of Medical Statistics and Molecular Epidemiology, Università Campus Bio-Medico di Roma, 00128 Rome, Italy; (C.R.); (V.B.); (M.C.)
| | - Chiara Romano
- Unit of Medical Statistics and Molecular Epidemiology, Università Campus Bio-Medico di Roma, 00128 Rome, Italy; (C.R.); (V.B.); (M.C.)
| | - Grazia Pavia
- Unit of Clinical Microbiology, Department of Health Sciences, “Magna Græcia” University of Catanzaro—“Renato Dulbecco” Teaching Hospital, 88100 Catanzaro, Italy; (G.P.); (A.Q.); (N.M.); (G.M.)
| | - Viola Bilotta
- Unit of Medical Statistics and Molecular Epidemiology, Università Campus Bio-Medico di Roma, 00128 Rome, Italy; (C.R.); (V.B.); (M.C.)
| | - Chiara Locci
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.L.); (I.D.); (N.P.); (M.P.); (D.S.)
- Department of Veterinary Medicine, University of Sassari, 07100 Sassari, Italy; (I.A.); (M.C.)
| | - Ilenia Azzena
- Department of Veterinary Medicine, University of Sassari, 07100 Sassari, Italy; (I.A.); (M.C.)
| | - Ilaria Deplano
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.L.); (I.D.); (N.P.); (M.P.); (D.S.)
| | - Noemi Pascale
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.L.); (I.D.); (N.P.); (M.P.); (D.S.)
- Department of Veterinary Medicine, University of Sassari, 07100 Sassari, Italy; (I.A.); (M.C.)
- Department of Chemical, Physical, Mathematical and Natural Sciences, University of Sassari, 07100 Sassari, Italy
| | - Maria Perra
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.L.); (I.D.); (N.P.); (M.P.); (D.S.)
- Department of Veterinary Medicine, University of Sassari, 07100 Sassari, Italy; (I.A.); (M.C.)
| | - Marta Giovanetti
- Department of Science and Technologies for Sustainable Development and One Health, Università Campus Bio-Medico di Roma, 00128 Rome, Italy;
- Instituto Rene Rachou, Fundação Oswaldo Cruz-FIOCRUZ, Belo Horizonte 30190-009, MG, Brazil
| | - Alessandra Ciccozzi
- Facoltà Dipartimentale di Scienze e Tecnologie per lo Sviluppo Sostenibile e One Health, Università Campus Bio-Medico di Roma, 00128 Rome, Italy;
| | - Andrea De Vito
- Unit of Infectious Diseases, Department of Medicine, Surgery and Pharmacy, University of Sassari, 07100 Sassari, Italy; (A.D.V.); (G.M.)
| | - Angela Quirino
- Unit of Clinical Microbiology, Department of Health Sciences, “Magna Græcia” University of Catanzaro—“Renato Dulbecco” Teaching Hospital, 88100 Catanzaro, Italy; (G.P.); (A.Q.); (N.M.); (G.M.)
| | - Nadia Marascio
- Unit of Clinical Microbiology, Department of Health Sciences, “Magna Græcia” University of Catanzaro—“Renato Dulbecco” Teaching Hospital, 88100 Catanzaro, Italy; (G.P.); (A.Q.); (N.M.); (G.M.)
| | - Giovanni Matera
- Unit of Clinical Microbiology, Department of Health Sciences, “Magna Græcia” University of Catanzaro—“Renato Dulbecco” Teaching Hospital, 88100 Catanzaro, Italy; (G.P.); (A.Q.); (N.M.); (G.M.)
| | - Giordano Madeddu
- Unit of Infectious Diseases, Department of Medicine, Surgery and Pharmacy, University of Sassari, 07100 Sassari, Italy; (A.D.V.); (G.M.)
| | - Marco Casu
- Department of Veterinary Medicine, University of Sassari, 07100 Sassari, Italy; (I.A.); (M.C.)
| | - Daria Sanna
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.L.); (I.D.); (N.P.); (M.P.); (D.S.)
| | - Giancarlo Ceccarelli
- Department of Public Health and Infectious Diseases, University of Rome Sapienza, 00161 Rome, Italy;
- Azienda Ospedaliero Universitaria Umberto I, 00185 Rome, Italy
| | - Massimo Ciccozzi
- Unit of Medical Statistics and Molecular Epidemiology, Università Campus Bio-Medico di Roma, 00128 Rome, Italy; (C.R.); (V.B.); (M.C.)
| | - Fabio Scarpa
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.L.); (I.D.); (N.P.); (M.P.); (D.S.)
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