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Human T cell lymphotropic virus I ( HTLV-I ) is the etiological agent for adult T cell leukemia and tropical spastic paraparesis (also termed HTLV-I -associated myelopathy ).
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
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