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.