Human herpesvirus 6 (HHV-6) infection was studied in 82 bone marrow transplant (BMT) recipients (72 allogeneic, 10 autologous). All recipients and 30 donors were seropositive for HHV-6 antibody at the time of bone marrow transplantation. Thirty-one recipients (37.8%) had HHV-6 viremia 2-4 weeks after transplantation. The incidence of HHV-6 viremia was significantly higher among allogeneic BMT recipients than in autologous BMT recipients (P=.011). Therefore, the following analyses of allogeneic BMT recipients were carried out (n=72). Geometric mean antibody titers (log(10)) were significantly higher in recipients without viremia than in those with viremia (1.84+/-0.39 vs. 1.61+/-0.42; P=.022). Logistic regression analysis demonstrated that leukemia or lymphoma is an independent risk factor (P=.031) for HHV-6 viremia. Rash occurring within 1 month after transplantation was observed in 17 (54.8%) of 31 recipients with HHV-6 viremia but in only 8 (19.5%) of 41 recipients without HHV-6 viremia (P=.001).

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Primers for herpes simplex virus type 1 (HSV 1)-specific loop-mediated isothermal amplification (LAMP) method amplified HSV-1 DNA, while HSV-2-specific primers amplified only HSV-2 DNA; no LAMP products were produced by reactions performed with other viral DNAs. The sensitivities of the HSV-1-and HSV-2-specific LAMP methods, determined by agarose gel electrophoresis, reached 500 and 1,000 copies/tube, respectively. The turbidity assay, however, determined the sensitivity of the HSV-1-and HSV-2-specific LAMP methods to be 1,000 and 10,000 copies/tube, respectively. After initial validation studies, 18 swab samples (in sterilized water) collected from patients with either gingivostomatitis or vesicular skin eruptions were examined. HSV-1 LAMP products were detected by agarose gel electrophoresis in the 10 samples that also demonstrated viral DNA detection by real-time PCR. Nine of these 10 samples exhibited HSV-1 LAMP products by turbidity assay. Furthermore, both the agarose gel electrophoresis and the turbidity assay directly detected HSV-1 LAMP products in 9 of the 10 swab samples collected in sterilized water. Next, we examined the reliability of HSV type-specific LAMP for the detection of viral DNA in clinical specimens (culture medium) collected from genital lesions. HSV-2 was isolated from all of the samples and visualized by either agarose gel electrophoresis or turbidity assay.Viral isolation and serological assays are standard methods of herpes simplex virus (HSV) diagnosis. Both viral isolation and serological testing, however, require substantial time to obtain accurate final results. More rapid detection has been achieved by modification of cell culture techniques by centrifugation of inocula on cell monolayers and the use of immunofluorescence techniques (6). Recent studies have suggested that detection of HSV DNA by PCR increases the sensitivity of viral infection detection compared to antigenic detection or cell culture methods (3,4,11,13,14). While quantitative analysis of viral DNA by real-time PCR may become a valuable tool for bedside monitoring of HSV infection and progression (1, 2, 7, 10, 17, 21, 22), it has not yet become a common procedure in hospital laboratories due to the requirement of specific expensive equipment (a thermal cycler).Recently, Notomi et al. (18) reported a novel nucleic acid amplification method, termed loop-mediated isothermal amplification (LAMP), which is used to amplify DNA under isothermal conditions with high specificity, efficiency, and speed. The most significant advantage of LAMP is the ability to amplify specific sequences of DNA between 63 and 65°C without thermocycling. Thus, the technique requires only simple and cost-effective equipment amenable to use in hospital laboratories. The LAMP method also exhibits both high specificity and high amplification efficiency. As the LAMP method uses four primers which recognize six distinct target DNA sequences, the specificity is extremely high. This method also exhibits extremely high amplification efficiency, due in...

Summary:We investigated whether a causal relationship exists between human herpesvirus 6 (HHV-6) and skin rash resembling acute graft-versus-host disease (GVHD) following bone marrow transplantation (BMT). Isolation of HHV-6 was used to monitor active HHV-6 infection in this study. We analyzed 25 episodes of skin rash in 22 recipients. All recipients were seropositive for HHV-6 before BMT. The onset of skin rash started prior to 30 days post transplantation (group A) in 15 of 25 cases, but after that (group B) in the remaining 10 cases. Twenty-five skin tissue samples were obtained from 22 recipients. The HHV-6 genome was detected in four of 15 skin samples from group A, but not detected in those from group B. HHV-6 was isolated from 11 of 22 recipients around 2 to 3 weeks after BMT (range 14 to 28 days after BMT). HHV-6 was isolated at a time between 10 days before and after the onset of skin rash (skin rash-related viremia) in nine cases in group A. Meanwhile, no skin rash-related viremia was observed in group B. Of the four recipients with positive detection of HHV-6 genome in their skin tissue (group A), two had HHV-6 viremia at the same time. The association between the timing of HHV-6 infection and the onset of skin rash was analyzed statistically. HHV-6 viremia (skin rash-related viremia) was found in nine of 15 (60%) cases in group A, compared with none of 10 (0%) cases in group B. This difference was statistically significant (P = 0.008). Moreover, HHV-6 infection (skin rash-related viremia and/or positive detection of HHV-6 DNA in skin tissue) was demonstrated in 11 of 15 (73.3%) cases in group A, compared with none of 10 (0%) cases in group B (P = 0.001). Thus, this study suggests that HHV-6 may be involved in the development of skin rash in the first month after allogeneic BMT. Bone Marrow Transplantation (2001) 28, 77-81.

A novel nucleic acid amplification method, termed loop-mediated isothermal amplification (LAMP), which amplifies DNA with high specificity, efficiency, and rapidity under isothermal conditions, may be a valuable tool for the rapid detection of infectious agents. LAMP was developed for human herpesvirus 6 (HHV-6), and its reliability was evaluated in this study. Although LAMP products were detected in HHV-6 B and HHV-6 A DNA, they were not detected in HHV-7 and human cytomegalovirus DNA. The sensitivity of the original HHV-6 LAMP protocol was 50 copies/tube. In order to increase the method's sensitivity, HHV-6 LAMP was modified by increasing the primer concentration. As a result of the modification, sensitivity increased to 25 copies/tube. After these initial validation studies, 13 patients with fever were tested for HHV-6 by viral isolation, serological analysis, and HHV-6 LAMP. In three of the eight patients with primary HHV-6 infection, HHV-6 DNA was detected in whole blood by the original HHV-6 LAMP protocol in not only the acute phase but also the convalescent phase. HHV-6 DNA was detected by modified HHV-6 LAMP in all eight plasma samples collected in the acute phase; however, no HHV-6 DNA was detected in plasma samples collected in the convalescent phase. Although HHV-6 DNA was detected in both the acute and convalescent phases of whole-blood samples in patients with past HHV-6 infection, it was not detected in plasma samples that did not contain latent viral DNA. Thus, detection of HHV-6 DNA in plasma by using this modified HHV-6 LAMP protocol is appropriate for diagnosis of active HHV-6 infection.