Edited by Genoveffa Franchini and Cynthia Masison
HTLV-1 is the only known retrovirus to directly cause cancer in humans. HTLV-1 discovered in the late seventy at the NIH in 1980, is transmitted through breast feeding, trans-placentally, sexually and by blood transfusion and organ transplants. HTLV-1 causes a lethal disease, Adult T-cell Leukemia/Lymphoma (ATLL), and a plethora of inflammatory conditions such as uveitis and dermatitis including the neurological degenerative condition designated as Tropical Spastic Paraparesis/HTLV-1 Associated Myelopathy (TSP/HAM) that results in paralysis of the lower limbs. HTLV-1 infection affects millions of people worldwide and currently there is neither targeted antiretroviral therapy nor a vaccine for HTLV-1.
There are several sub-types of HTLV-1. The most prevalent are HTLV-1 subtypes A and B that are found worldwide and are endemic in Japan, the Caribbean, South America and Africa. However, pockets of HTLV-1 infections have also been described in the United States, Iran, Romania and more recently in the UK. In contrast, HTLV-1C, found first in Melanesia in 1993, was described later in New Caledonia and Australia, appears limited to Oceania. It is estimated that HTLV-1C has evolved independently in remote indigenous populations of Oceania in the last 40,000 years.
The current prevalence of HTLV-1 infection in the world is not known, as the last large-scale epidemiological studies were performed more than 30 years ago. Recently, an extraordinarily high prevalence of HTLV-1C, up to 50% in both female and males, has been described in underserved communities in the Norther Territory of Australia. HTLV-1C infection is associated not only with ATLL and TSP/HAM but also with a high mortality at a young age (mid 40s), due to lung inflammation, bronchiectasis, and infectious diseases. By the age of 40, both sexes exhibit a 30-40% HTLV-1C seroprevalence.
Despite the serious health problem caused by infection with all HTLV-1 subtypes, infection by these viruses has become a neglected condition and only palliative treatments are available to the 10-20 million of HTLV-1 infected individuals living mostly in resource deprived countries. Furthermore, the serious medical condition associated with HTLV-1C infection in indigenous populations of Australia, highlights the urgent need to extend HTLV-1 research.
Research on HTLV-1, a virus that has adapted to humans since ancient time, has thought us unexpected novel viral strategies to hijack host cellular pathways in T-cells and to counteract immune responses. There is an urgent need to discover novel preventive or therapeutic remedies for this virus that may relieve not only the suffering of HTLV-1 infected individuals but also augment our understanding of other chronic infection with cancer viruses.
The recent awareness of the serious medical condition associated with HTLV-1C infection in indigenous populations of Australia, highlights the urgent need to revitalize HTLV-1 research. Thus, the scope of this collection is to summarize what is known on HTLV-1 replication, pathogenesis, treatment and prevention and identify essential areas of unmet need in HTLV-1 basic and translational research.
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