IL-2-regulated persistent human herpesvirus-6B infection facilitates growth of adult T cell leukemia cells.

Human herpesvirus-6B (HHV-6B), a causative agent of exanthem subitum, infects human adult T cell leukemia (ATL) cell lines. We established a persistent HHV-6B infection in an ATL cell line, TaY, in the presence of 20 units/ml interleukin-2 (IL-2). The HHV-6B infected culture proliferated with a constant ratio of infected (1%) to the uninfected (99%) cells. When the IL-2 concentration was reduced to 5 units/ml, the number of infected cells in the culture increased transiently by 60% in 11 days, a new balance of 25% infected cells and 75% uninfected cells was established thereafter. PCR analysis confirmed a 125-fold increase in the amount of viral genome in the culture, while the treatment with ganciclovir reduced the proportion of infected cells, indicating that an efficient replication of virus was induced in the culture. Both of these cultures were maintained in the presence of 20 or 5 units/ml IL-2 over one year without loss of infected cells. Interestingly, we found that cultures containing the infected cells grew significantly faster than the parental uninfected cells at the same concentration of IL-2. The infected culture continued to grow for 7 days even in the absence of IL-2. Because the infection induces cell cycle arrest, these results indicate that the HHV-6B-infected ATL cells stimulate the growth of the uninfected cells during persistent infection in culture.

Transcriptional profiling of human herpesvirus type B (HHV-6B) in an adult T cell leukemia cell line as in vitro model for persistent infection.

Human herpesvirus 6 (HHV-6), which is present in more than 90% of the human, is known to cause infectious diseases in immuno-compromised patients, e.g., transplant patients. To clarify the possible role of the pattern of expression of HHV-6 genes in various types of HHV-6B infection, we sought to determine whether or not viral DNA microarray could be used for detailed characterization of viral transcription using a HHV-6B DNA microarray that contains 97 known open reading frames of HHV-6B. A subset of genes are preferentially expressed in persistent infection: U16 (IE-B, transactivator, US22 gene family), U18 (IE-B, homolog to HCMV IE glycoprotein), U20 (glycoprotein), U27 (DNA polymerase processivity transactivator), U82 (gL, gH accessory protein), U83 (chemokine), U85 (OX-2 homology, glycoprotein), U90 (IE-A), and U94 (transactivator), respectively. Although the function of each HHV-6B is not fully understood, our study suggests that comprehensive analysis of HHV-6B transcription is useful not only to clarify the pathogenesis of the virus but also to develop new strategies for anti-viral drugs.

Quantification of human cytomegalovirus using bronchoalveolar lavage cells in pulmonary complications associated with hematologic neoplasia.

Human cytomegalovirus (CMV) has been recognized as a frequent pathogen involved in interstitial pneumonia (IP), and CMV-IP is a severe and life-threatening complication in the immunocompromised patients. The use of real-time PCR in molecular diagnostics has increased to the point where it is now accepted as the gold standard for detecting a wide variety of templates including viruses. Therefore, we developed a rapid quantification system of CMV using a LightCycler in order to clarify the possible role of CMV reactivation in patients with hematologic neoplasia showing pulmonary complications. Sixty-nine bronchoalveolar lavage fluid (BALF) specimens were obtained from consecutively treated patients showing interstitial shadow including 20 patients with hematologic neoplasia. First, we determined the viral burden in BAL cells from healthy volunteers, idiopathic interstitial pneumonia (IIP) and sarcoidosis. CMV copy numbers in samples obtained from healthy volunteers, IIP and sarcoidosis, were less than 10(2) copies per 1 microg of DNA, whether or not BAL cells were composed of high percentage of lymphocytes. Among 20 patients with hematologic neoplasia analyzed, two specimens obtained from leukemia patients with pulmonary alveolar proteinosis, two from GvHD, one with CMV interstitial pneumonia and one with Hodgkin's disease had high level of CMV viral DNA. Our results suggest that measurement of CMV genomes in BAL cells using real-time PCR may be useful not only to understand the involvement of CMV in systematic respiratory tract disease but also in management of the care of respiratory complications in hematologic neoplasia.