Human herpesvirus 6 (HHV-6), which belongs to the betaherpesvirus subfamily and infects mainly T cells in vitro, causes acute and latent infections. Two variants of HHV-6 have been distinguished on the basis of differences in several properties. We have determined the complete DNA sequence of HHV-6 variant B (HHV-6B) strain HST, the causative agent of exanthem subitum, and compared the sequence with that of variant A strain U1102. A total of 115 potential open reading frames (ORFs) were identified within the 161,573-bp contiguous sequence of the entire HHV-6 genome, including some genes with remarkable differences in amino acid identity. All genes with <70% identity between the two variants were found to contain deleted regions when ORFs that could not be expressed were excluded from the comparison. Except in the case of U47, these differences were found in immediate-early/regulatory genes, DR2, DR7, U86/90, U89/90, and U95, which may represent characteristic differences of variants A and B. Also, we have successfully typed 14 different strains belonging to variant A or B by PCR using variant-specific primers; the results suggest that the remarkable differences observed were conserved evolutionarily as variant-specific divergence.

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Aldose reductase (AR) is an NADPH dependent enzyme that catalyses the reduction of the aldehyde to the corresponding alcohols. Diabetic complications including neuropathy, nephropathy, cataracts and retinopathy are considerately caused by accumulation of sorbitol, which is produced from glucose by AR in polyol pathway. The aim of AR inhibitor therapy is to normalize the elevated flux of blood and sorbitol through the polyol pathway in the target tissue. A large number of inhibitors have been prepared synthetically, and some of them are used therapeutically. However, none of them is satisfactory. From the plants, many AR inhibitors have been found, which are discussed in this review. By the structure based functioning of AR and its inhibitors, some will be developed promising in the treatment of diabetic complications. The main structural features of the inhibitors will be a polar head group and a hydrophobic ring system. The plants that contain the AR inhibitors may prevent from diabetic complications.

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