Enveloped animal viruses usually possess a surface glycoprotein which mediates fusion between the viral envelope and host cell membrane, hence enabling the initiation of infection, and its biosynthesis often involves post‐translational endoproteolytic activation of the inactive precursor by a host cell protease(s). Therefore, the protease distribution in the host must be critical for determining the viral tropism. We previously isolated from chick embryo a cogent candidate endoprotease of this kind for paramyxovirus infection, and demonstrated its identity with factor X (FX), a vitamin K‐dependent serine protease in the prothrombin family which, in general, is synthesized in the liver and circulates as one of the plasma proteases essential for blood clotting. Here, we examined FX expression with specific cDNA and antibody probes in a series of embryonic tissues. Many tissues other than the liver expressed the specific mRNA but, in most instances, the translation products remained inactive zymogen forms. The enzymatically active FXa was detectable only in the allantoic fluid and amniotic fluid, and virus spreading was strictly confined to the tissues in direct contact with these FXa‐containing fluids. Thus, the ectopically expressed FXa is probably the major host determinant of paramyxovirus tropism in ovo.

Object: To examine the role of human leukocyte antigen (HLA) class II genes in the development of systemic sclerosis (SSc) as well as in the clinical and serologic expression of SSc in patients. Methods: HLA-DRB1, DRB3, DRB4, DQB1, and DPB1 alleles were determined by genotyping; and serum antinuclear antibodies were identified using indirect immunofluorescence, double immunodiffusion and immunoprecipitation. Patients: One hundred and five Japanese patients with SSc and 104 race-matched healthy controls. Results: Frequencies of DRB1and DQB1alleles were not different between SSc patients and healthy controls, while DPBl*0901 was marginally increased in SSc patients. In contrast, SSc-related autoantibodies were closely associated with the clinical features. HLAclass II genes were detected as follows: anti-DNA topoisomerase I antibody with diffuse cutaneous involvement, pulmonary fibrosis, and DRBl*1502-DQBl*0601-DPBl*0901 ; anti-UlRNP antibody with overlapping features of lupus and/or myositis and DRBl*0401/*0802-DQBl*0302; and anticentromere antibody with limited cutaneous involvement and DRBl*0101-DQBl*0501-DPBl*0402. In the analysis of the association of HLAclass II and the clinical features in SSc patients significant differences were obtained only for the increased frequencies of arthritis and rheumatoid factor in patients with DRBl*0405 compared to those without. Conclusion: HLAclass II genes strongly influence the production of SSc-related autoanti-bodies rather than the development of SSc. In addition, SSc is a composite disease of distinctive subsets defined by serum autoantibodies, which have specific clinical and HLAclass II associations. (Internal Medicine 38: 336-344, 1999)

Autoantibodies to RNA polymerases (RNAP) I, II, and III are reported to be highly specific for the diagnosis of scleroderma (systemic sclerosis, SSc). In the present study, the specificity of autoantibodies to RNAP I and III for SSc was confirmed by immunoprecipitation of 35S-labeled proteins. However, we report here the previously unrecognized production of anti-RNAP H autoantibodies by 9-14% of patients with SLE and mixed connective tissue disease/overlap syndrome. 12 out of 32 anti-RNAP H positive sera (group 1) immunoprecipitated a diffuse 220-240-kD band identified as the largest subunit of RNAP H whereas the remaining 20 (group 2) immunoprecipitated preferentially the 240-kD phosphorylated (Ho) form of the large subunit. After pulse labeling, group 1 sera immunoprecipitated only the 220-kD (Ila) RNAP H subunit, whereas the diffuse Ha/Ho band plus the 145-kD second largest RNAP II subunit (Hc) were immunoprecipitated after several hours of cold chase, suggesting that these sera recognized primarily the largest subunit of RNAP H. Group 2 sera recognized the Ilc subunit after pulse labeling, and immunoprecipitated the Ilc and Ho, but not the Ha, subunits after cold chase. Although it has been suggested that autoantibodies to RNAP II are usually accompanied by anti-RNAP I/III in SSc, all but one of the anti-RNAP H positive sera from SLE or mixed connective tissue disease/overlap syndrome patients, as well as most of the SSc sera, were negative for anti-RNAP h/IH. Moreover, in contrast to previous reports suggesting that anti-RNAP antibodies rarely coexist with other SSc subset marker antibodies, anti-RNAP H antibodies were often accompanied by anti-Ku, anti-nRNP, or anti-topoisomerase I autoantibodies in the present study. We conclude that autoantibodies to RNAP H are not a specific marker for SSc, whereas autoantibodies to RNAP I/III are associated primarily with SSc. In addition, we have identified two distinctive patterns of RNAP H antigen recognition by autoanti-

Acacia spp. produce gum exudates, traditionally called gum arabic or gum acacia, which are widely used in the food industry such as emulsifiers, adhesives, and stabilizers. The traditional gum arabic is highly variable with average molecular weights varying from 300,000-800,000. For this reason a standardized sample was used for the present experiments, based on a specific species of gum arabic (Acacia(sen)SUPER GUMEM2). The literature indicates that gum arabic can be fermented by the intestinal bacteria to short chain fatty acid, particularly propionate. However, the bacteria responsible for the fermentation have not been determined. In this study, we used enrichment culture of pig cecal bacteria from the selected high molecular weight specific gum arabic of (M(W )1.77 x 10(6)). We found Prevotella ruminicola-like bacterium as a predominant bacterium that is most likely to be responsible for fermentation of the gum arabic used to propionate.

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