This document summarizes information about Human T-Lymphotropic Viruses Type 1 and 2 (HTLV-1 and HTLV-2). It describes their taxonomy as retroviruses, morphology and composition, replication and pathogenesis. HTLV-1 can cause Adult T-cell leukemia/lymphoma and Tropical Spastic Paraparesis, while HTLV-2 is rarely associated with disease. Transmission occurs through blood, sexual contact, and mother-to-child. While no treatment exists for the viruses, some therapies may help related diseases. Diagnosis involves blood tests and DNA detection by PCR.

1. Human T-Lymphotropic
Viruses
oHuman T-Lymphotropic Virus Type 1
oHuman T-Lymphotropic Virus Type 2

2. A. Taxonomy
o Family: Retroviridae
o Subfamily: Orthoretrovirinae
o Genus: Deltaretrovirus
o Species: Human T-Lymphotropic Virus 1
• Subtype:
a. Cosmopolitan Group
b. Central African Group
c. Melanesian Group
d. New Central African group
o Species: Human T-Lymphotropic Virus 2

3. B. Morphology & Composition
o Virion: spherical to pleomorphic, 80-110nm in
diameter
o Capsid: Icosahedral with helical nucleoprotein
o Composition: RNA(2%), Protein(about 60%),
Lipid(about 35%), Carbohydrate(3%)
o Genome: ssRNA, linear, positive-sense, 7-11kb
o Proteins: Reverse transcriptase- enzyme contained
inside the virions
o Envelope: Present
**Oncogenic

4. C. Replication, Morphogenesis, & Maturation

5. D. Pathogenesis
o Host:
o Humans (HTLV-1 and HTLV-2)
o Cell Tropism:
 HTLV-1: CD4+ Tcells
 HTLV-2: CD8+ Tcells

6. o Diseases:
o Asymptomatic Infection (Most common; HTLV-1 & 2)
o HTLV-1
o Adult T-cell leukemia-lymphomas (ATL) - Malignant
neoploasm of T lymphocytes
o Tropical Spastic Paraparesis - “HTLV-1 associated
myelopathy”
o HTLV-2
o Atypical Hair-cell leukemia
o Adult T-cell leukemia(ALT; RARE)

7. Mode of Transmission (HTLV-1 and HTLV-2)
Blood transfusion

8. Sharing of blood contaminated needles
(drug abusers)

9. Sexual intercourse

10. Mother-to-Child transmission

11. E. Treatment
o No treatment exists for HTLV virus
o combination of interferon-alpha and
zidovudine had been reported to be effective
in treating ATL patients.
o combination of zidovudine, danazol, and
Vitamin C provides a temporary relief for TSP
patients.

12. F. Laboratory Diagnosis
o Peripheral blood smear
o ATLL cells present
o Serology
o EIA
o Western Blot
o Detection of Proviral DNA
o PCR

13. i. Reference
o Medical Microbiology, 26th ed.: Jawetz, Melnick, and
Aldelberg
o Medical Virology, 4th ed,: White, and Fenner
o http://emedicine.medscape.com/article/219285-overview
o http://www.mayomedicallaboratories.com/test-
catalog/Clinical+and+Interpretive/9539
o http://viralzone.expasy.org/
o https://www.youtube.com/watch?v=eS1GODinO8w
o http://www.arupconsult.com/Topics/HTLV.html
o http://virology-online.com/viruses/HTLV4.htm