柳井 広之

Previously, we reported that interleukin-2 (IL-2)-stimulated helper T cells produced an unknown soluble factor which induced dendritic cell-like differentiation in primary cultures of monocytic leukemia cells and we referred to this factor as dendritic cell differentiation factor (DCDF). In this study, we attempted to purify and characterize DCDF and investigated its biological effect on normal human monocytes. Gel filtration chromatography indicated that the molecular weight of DCDF is approximately 30-35 kDa. Chromatofocusing indicated that the isoelectric point of DCDF is approximately 5.0. DCDF, partially purified by subsequent gel filtration, chromatofocusing, and hydrophobic chromatography, significantly enhanced the HLA-DR expression of normal human monocytes and a human monocytic leukemia cell line, THP-1. This biological activity was not neutralized by any known antibodies to human cytokines. DCDF significantly amplified the T-cell stimulatory activity of monocytes in the allogeneic mixed leukocyte reaction (MLR). Moreover, DCDF significantly enhanced IL-1 beta and IL-6 production by monocytes in a dose-dependent manner. These results suggest that DCDF is a novel human cytokine which stimulates the accessory cell function of monocytes.

A simian cell line, Si-IIA, harboring Epstein-Barr-virus (EBV) -related herpesvirus (Si-IIA-EBV), produces malignant lymphoma in rabbits when administered by intravenous inoculation. In this study, we analyzed the Si-IIA-EBV genome and compared it with human EBV and herpesvirus macaca fascicularis 1 (HVMF 1 ), which is associated with B-cell lymphoma developing in SIV-infected immunosuppressed monkeys. DNA from Si-IIA-EBV was amplified by the polymerase chain reaction using three different primer pairs complementary to human EBV (B95-8) DNA; two of the primer pairs covered part of the long internal repeat 1 region (IR 1) and the third covered part of the BRRF 1 region. Direct sequencing of the three PCR products revealed that Si-IIA-EBV DNA had about 82% nucleotide homology to the human EBV DNA in all three regions and 92.4% homology to HVMF1 in the IR1 region. The blotting pattern by Southern blot analysis was different between Si-IIA-EBV and human EBV.

Circulating hepatitis C virus (HCV) particles can be fractionated by means of differential flotation centrifugation. It is reported that in the bottom fraction HCV is in the form immune complexes, whereas in the top, it is free of antibodies. We evaluated the significance of circulating complex and free HCV in chronic hepatitis C, and assessed the relationship in terms of the response to interferon (IFN) therapy. We examined sera before, just after, and 1 year after administering IFN to 18 patients with chronic hepatitis C, 10 of whom responded (group CR), and 8 did not (group NR). The amounts of virus were similar between both groups before therapy. After differential flotation centrifugation with 1.063 g/ml of NaCl, the top and bottom fractions were assayed for HCV RNA. Before therapy, HCV RNA was detected in the top fraction in 1 of 10 in group CR, and in 6 of 8 in group NR (P < 0.05, chi-square test). HCV RNA was positive in the bottom fraction of all samples. In a follow-up study of group NR, HCV RNA was detected in the top fraction in 3 of 8 just after IFN therapy, and in 7 of 8 after 1 year. This study suggests that the presence of HCV in the top fraction can predict a poor response to IFN therapy.