Human T-Lymphotrophic Virus Types I, II - HTLV I, II

Human T-Lymphotrophic Virus Types I, II - HTLV I, II

 

HTLV-I is etiologically associated with adult T-cell leukemia/lymphoma (ATLL), a demyelinating neurological disorder termed tropical spastic paraparesis (TSP) and with HTLV-I associated myelopathy (HAM).

Epidemiology

  • Incidence – 15-20 million globally infected with HTLV I
    • Endemic in Japan, Caribbean countries and Sub-Saharan Africa
  • Transmission
    • Parenteral
    • Sexual

Organism

  • HTLV I and II are human type-C retroviruses
    • Several subtypes exist that are geographically specific
  • Majority of human infection caused by subtype 1

Risk factors

  • Cellular blood products (most efficient mode of transmission)
  • Breast milk – 20% of children of infected mothers will also become infected
  • Sexual contact – associated with unprotected sex, multiple partners, presence of genital sores, exchanging sex for drugs or money
  • Sharing contaminated needles and syringes (intravenous drug users)
  • Perinatal transmission suspected
  • Poverty

Clinical Presentation

  • ATLL
    • Life-time risk for ATLL in those with HTLV-I antibodies is low;
      • Even in countries with a high-prevalence of HTLV-I (eg, Japan), the risk for developing ATLL is only 1-2%
    • 4 types of ATLL – acute, chronic, smoldering, lymphoma type
    • Acute ATLL most common
      • Rapidly fatal without treatment
      • Pulmonary complications, opportunistic infections, sepsis
      • Uncontrolled hypercalcemia may occur
  • HAM/TSP
    • Slowly progressive spastic paraparesis
    • Develops in up to 4% of infected patients
    • Gender – F>M
    • Age – 4th to 5th decade
    • Caused by immune response to HTLV-I
  • HTLV and AIDS
    • HTLV-I does not cause AIDS
    • Antibodies of HTLV-I have no relationship to antibodies of HIV-I, and antibodies to HTLV-I do not imply excess risk for AIDS
    • HTLV-I virus only remotely related to AIDS virus, HIV-I
    • HTLV-I and HTLV-II have transmission similar to HIV-I and HIV-II
    • Individuals with HTLV-I or HTLV-II may be co-infected with HIV due to common risk factors (sexual contact, intravenous drug use)

Diagnosis

  • Laboratory testing
    • HTLV-I antibody testing
      • HTLV-II antibodies significantly cross-react to HTLV-I antigens
      • Populations such as parenteral drug abusers infected with HTLV-II may test positive for HTLV-I antibodies due to antibody cross-reactivity
      • Asymptomatic patients with HTLV-I antibodies
        • May be infected and should not donate blood
        • May not have ATLL or TSP and may not develop ATLL, HAM or TSP
      • Proviral loads correlate with infectivity

See Also