Epidemiology and Etiopathology of Human T-Lymphotropic Viruses: Diagnostic and Clinical Implications for Non-Endemic Areas

Are HTLV-II-seropositive injection drug users at increased risk of bacterial pneumonia, abscess, and lymphadenopathy?

Disease associations of HTLV-II are poorly defined, despite a high seroprevalence among injection drug users (IDU). One hundred twenty-four HTLV-II-seropositive emergency room and clinic patients were matched by age, sex, and clinic to 120 HTLV-I/II-seronegative patients. Medical records were reviewed blinded to HTLV-II status, and International Classification of Disease 9th Clinical Modification (ICD-9CM)-coded diagnoses were compared between seropositive patients and controls. After adjustment for relevant confounding variables such as human immunodeficiency virus infection, HTLV-II-seropositive IDU had an increased risk of bacterial pneumonia (odds ratio [OR], 3.45; 95% confidence interval [CI], 1.58, 7.56), abscess (OR, 8.30; 95% CI, 4.02, 17.11), and lymphadenopathy (OR, 3.91; 95% CI, 1.24, 12.32) compared with HTLV-II-negative non-IDU patients. In contrast, HTLV-II-negative IDU were at only marginally increased risk of the same conditions, with OR of 1.76 (95% CI, 0.42, 7.40), 3.00 (95% CI, 0.94, 9.59), and 1.31 (95% CI, 0.15, 11.66), respectively. These results indicate that HTLV-II seropositivity may define a subgroup of IDU who are at particularly high risk of bacterial pneumonia, skin and soft tissue abscess, and lymphadenopathy. Whether HTLV-II has an etiologic role in predisposing IDU to bacterial infections and lymphadenopathy will require further investigation.

Detection of HTLV type I provirus by in situ polymerase chain reaction in mouthwash mononuclear cells of HAM/TSP patients and HTLV type I carriers

Molecular studies have revealed the presence of HTLV-I provirus DNA in saliva of HTLV-I-infected subjects. However, cellular localization has not been determined. In the present study, we have used in situ PCR technique to study saliva-associated cells for localization of HTLV-I proviral DNA. We found that HTLV-I proviral DNA was present in the nuclei and cytoplasm of salivary lymphocytes in five (71%) of seven HTLV-I-seropositive subjects. The percentage of infected cells in positive mouthwash samples ranged from 0.5 to 2%. None of the HTLV-I-negative patients had HTLV-I provirus in saliva. The localization of HTLV-I provirus DNA suggests that salivary lymphocytes can serve as vector for HTLV-I infection through saliva.

The epidemiology of HTLV-I in Europe

Although human T-lymphotropic virus type I (HTLV-I) infection in Europe is thought to be unusual except amongst people who have immigrated from countries where HTLV-I is endemic, the screening of blood donors has revealed a low seroprevalence across Europe, not only in donors originating from endemic areas but also in the indigenous population. Data from blood donors should not be extrapolated to other groups because blood donors are selected to be at low risk of parenterally transmissible infections. Unfortunately only small studies have been conducted in other population groups, including women attending antenatal clinics, despite the importance of breast-feeding in vertical transmission. Data from metropolitan areas of the United Kingdom and France suggest that the seroprevalence of HTLV-I in pregnant women is up to 100 times higher than in blood donors. HTLV-I infection is also more common in patients attending sexually transmitted disease clinics, whilst HTLV-II is endemic in many cities amongst intravenous drug users. There are few incidence data for diseases associated with HTLV-I, even though cases of adult T-cell leukemia/lymphoma and HTLV-I-associated myelopathy have been described in many European countries. Data on the seroprevalence of HTLV-I in central and eastern Europe are scanty but the few published studies suggest a higher rate than has been documented in western Europe.