HUMAN T-CELL LEUKEMIA VIRUS (HTLV)

Structure & Property	Transmission	Pathogenesis	Clinical findings	Laboratory diagnosis	Treatment	
Family: retrovirus

Genome: single strand RNA, 2 segments, +ve polarity.

Size: 100nm

Icosahedral nucleocapsid

Spherical enveloped particles surrounded by spikes or knobs.

Two types:
- HTLV-1
- HTLV-II: similar structurally with extensive nucleic acid homology with HTLV-1.	Sexual, vertical (via breast milk) and by blood – transfused blood is hihgly infectious.

Occurs in Japan, the Caribbean & West Africa.	The CD4 receptors on the T cells are the receptors for these viruses.

HTLV-I and II transform and cause the T cells to proliferate.

Role of tax protein:
- acts on viral LTR sequences to stimulate viral mRNA synthesis.
- increase production of IL-2 and IL-2 receptor.	Incubation period: symptoms appear after a prolonged period –usually many years.

T cell leukemia:
- an aggressive malignancy of T cells, with lymphadenopathy and hepatosplenomegaly; sometimes with cerebral involvement.
- may present with lymphomatous infiltration of the skin.
- increased level of calcium in blood due to osteoporotic lesions.

Tropical spastic paraparesis: a progressive non-demyelinating spastic paralysis, more common in females than males.

Symptomless infections: most people do not develop disease.

Antibody persists throughout infection.	Grows in culture in human T cells stimulated with IL-2; cells are transformed or immortalized without CPE.

Detected by EM.

HTLV-I and II can be distinguished serologically and by differences in their gene sequences using products of PCR.	No antiviral or vaccine available.

AZT: first line therapy.