Expansion of clonotypic T-cell populations in the peripheral blood of asymptomatic Gran Chaco Amerindians infected with HTLV-IIB

Lymphotropic Viruses EBV, KSHV and HTLV in Latin America: Epidemiology and Associated Malignancies. A Literature-Based Study by the RIAL-CYTED

The Epstein-Barr virus (EBV), Kaposi sarcoma herpesvirus (KSHV) and human T-lymphotropic virus (HTLV-1) are lymphomagenic viruses with region-specific induced morbidity. The RIAL-CYTED aims to increase the knowledge of lymphoma in Latin America (LA), and, as such, we systematically analyzed the literature to better understand our risk for virus-induced lymphoma. We observed that high endemicity regions for certain lymphomas, e.g., Mexico and Peru, have a high incidence of EBV-positive lymphomas of T/NK cell origin. Peru also carries the highest frequency of EBV-positive classical Hodgkin lymphoma (HL) and EBV-positive diffuse large B cell lymphoma, not otherwise specified (NOS), than any other LA country. Adult T cell lymphoma is endemic to the North of Brazil and Chile. While only few cases of KSHV-positive lymphomas were found, in spite of the close correlation of Kaposi sarcoma and the prevalence of pathogenic types of KSHV. Both EBV-associated HL and Burkitt lymphoma mainly affect young children, unlike in developed countries, in which adolescents and young adults are the most affected, correlating with an early EBV seroconversion for LA population despite of lack of infectious mononucleosis symptoms. High endemicity of KSHV and HTLV infection was observed among Amerindian populations, with differences between Amazonian and Andean populations.

Prevalence of HTLV-I-associated T-cell lymphoma

In order to assess the prevalence rate of HTLV-1-associated T-cell lymphomas and human retrovirus infection in general, approximately 21,000 individuals representing various patient populations, retroviral risk groups, and blood donors were examined for HTLV-I, HTLV-II, HIV-1, or HIV-2 infection using serologic and PCR assays. The prevalence rates among volunteer blood donors were 0.02% and 0% for HTLV and HIV, respectively. Significantly increased HTLV prevalence rates were observed among paid blood donors, African American health care clinic patients, Amerindians, recipients of HTLV-positive cellular blood products, intravenous drug users, sexual contacts and family members of HTLV-positive people, and patients with primary thrombocytosis and other-than-low-grade non-Hodgkin's lymphoma (NHL). Among some of these groups there were significant differences in the prevalence of HTLV-I versus HTLV-II. The eight HTLV-positive NHL patients all had mature, high-grade, CD4+ T-cell lymphomas with clonally integrated HTLV-I, for a prevalence of 4% among other-than-low-grade NHL patients. Seven of the eight died from their disease within 2 years despite treatment. Interestingly, two groups at risk for HTLV infection, namely needle stick victims and recipients of HTLV-infected and/or pooled plasma products, showed no evidence for infection. Significantly increased HIV-1 prevalence was observed among paid blood donors, African Americans, homosexuals, female prostitutes, hemophiliacs, and other-than-low-grade NHL patients. Only one patient was infected with HIV-2. Of the nine HIV-positive, other-than-low-grade NHL patients, seven HIV-1 positives had B-cell lymphomas, one HIV-1 positive had an HTLV-I-positive CD4+ T-cell lymphoma, and one infected with HIV-2 had a CD4+ T-cell lymphoma that was HTLV negative. The data indicate that HTLV-I lymphoma, while uncommon, is not necessarily rare among other-than-low-grade NHL cases in the United States and, given its poor prognosis, should probably be studied separately in clinical trials.

Comparative performances of an HTLV-I/II EIA and other serologic and PCR assays on samples from persons at risk for HTLV-II infection

BACKGROUND

HTLV-I and HTLV-II are related exogenous pathogenic human retroviruses. Until recently, ELISAs based on HTLV-I antigens have been used to screen for the presence of HTLV-I or -II antibodies. The HTLV-I-based assays have not been as sensitive in detecting antibodies to HTLV-II as in detecting antibodies to HTLV-I. The Abbott HTLV-I/HTLV-II ELISA uses a combination of HTLV-I and HTLV-II antigens to detect antibodies to the whole HTLV group. The performance of this ELISA was compared to that of several HTLV-I-based serologic assays and an HTLV-II PCR assay in cohorts of South American Indians and New York City IV drug users (IVDUs) in whom HTLV-II is endemic.

STUDY DESIGN AND METHODS

Sera from 429 South American Indians and New York City IVDUs were evaluated for HTLV antibodies by the use of three ELISAs (rgp21-enhanced HTLV-I/II, Cambridge Biotech; Vironostika HTLV-I/II, Organon Teknika; and HTLV-I/HTLV-II, Abbott), and a Western blot (WB) assay. Peripheral blood leukocyte DNA from each person was analyzed for HTLV-I and HTLV-II pol DNA via PCR. The HTLV-II PCR-positive samples were further subtyped via cloning and sequencing and/or oligomer restriction.

RESULTS

Two hundred four samples (48%) were positive for HTLV-II by serologic and/or PCR assays. All of the positive samples from the Indians and approximately one-third of the positive samples from the IVDUs were of the HTLV-IIB subtype. Comparative analyses indicate that the sensitivity and specificity of the various assays were: PCR, 98 and 100 percent; Abbott HTLV-I/HTLV-II, 78 and 95 percent; Cambridge Biotech HTLV-I/II, 76 and 96 percent; Vironostika HTLV-I/II, 71 and 98 percent; and WB, 73 and 100 percent, respectively.

CONCLUSION

There were no significant differences among the sensitivities and specificities of the HTLV-I/II ELISAs (p values, 0.056-0.438). The WB and PCR assays were much more specific than the other serologic assays (p</=0.03). However, the PCR assay is significantly (p<0.001) more sensitive than any of the serologic assays in the detection of HTLV-II infection. Thus, optimal detection of HTLV-II infection would seem to require both serologic and DNA PCR assays.

Multiplex detection of four pathogenic retroviruses using molecular beacons

We describe a multiplex nucleic acid assay that identifies and determines the abundance of four different pathogenic retroviruses (HIV-1, HIV-2, and human T-lymphotrophic virus types I and II). Retroviral DNA sequences are amplified in a single, sealed tube by simultaneous PCR assays, and the resulting amplicons are detected in real time by the hybridization of four differently colored, amplicon-specific molecular beacons. The color of the fluorescence generated in the course of amplification identifies which retroviruses are present, and the number of thermal cycles required for the intensity of each color to rise significantly above background provides an accurate measure of the number of copies of each retroviral sequence that were present originally in the sample. Fewer than 10 retroviral genomes can be detected. Moreover, 10 copies of a rare retrovirus can be detected in the presence of 100, 000 copies of an abundant retrovirus. Ninety-six samples can be analyzed in 3 hr on a single plate, and the use of a closed-tube format eliminates crossover contamination. Utilizing previously well characterized clinical samples, we demonstrate that each of the pathogenic retroviruses can be identified correctly and no false positives occur. This assay enables the rapid and reliable screening of donated blood and transplantable tissues.