The polypeptides from purified virions of a herpes simplex 1 (human herpes-virus 1) strain, F1, which had been passaged a limited number of times in cell culture after isolation, formed 33 bands on electrophoretic separation in polyacrylamide gels cross-linked with N, N′ -diallyltartardiamide in contrast to a maximum resolution of only 24 to 25 bands in gels cross-linked with N, N′ -methylenebisacrylamide. This increase in the number of bands was due chiefly to an improved separation of glycosylated polypeptides from nonglycosylated polypeptides with which they co-electrophoresed on methylenebisacrylamide cross-linked gels. Purified virions of HSV-1 [F1] had a protein/DNA mass ratio of 10.7 ± 0.96, and based on a DNA molecular mass of 85 × 10 6 to 100 × 10 6 the estimated weight of virion polypeptides ranges from 16.4 to 19.4 × 10 −16 g. The number of molecules of each polypeptide per virion ranged from less than 50 to 1,500. Comparison of the virion polypeptides of two HSV-1 strains with similar isolation and limited passage history with those of four HSV-1 strains with histories of numerous passages outside the human host showed a number of nonrandom variations in virion polypeptides. Thus, although the virion polypeptides of two strains with similar isolation and limited passage history could not be differentiated, strains with extended passage histories differed markedly from each other and from the limited passage strains in the number and electrophoretic mobility of noncapsid polypeptides and notably in those of the envelope.

Hashimoto's thyroiditis (HT) is the most common of all thyroid diseases and is characterized by abundant lymphocyte infiltrate and thyroid impairment, caused by various cell- and antibody-mediated immune processes. Viral infections have been suggested as possible environmental triggers, but conclusive data are not available. We analyzed the presence and transcriptional state of human herpesvirus 6 (HHV-6) in thyroid fine needle aspirates (FNA) and peripheral blood mononuclear cells (PBMCs) from 34 HT patients and 28 controls, showing that HHV-6 DNA prevalence (82% vs. 10%, p≤0.001) and viral load were significantly increased in FNA from HT patients, and thyrocytes from HT FNA displayed a 100-fold higher HHV-6 DNA load compared to infiltrating lymphocytes. In addition, while HHV-6 was strictly latent in positive samples from controls, a low grade acute infection was detected in HT samples. HHV-6 variant characterization was carried out in 10 HT FNA samples, determining that all specimens harbored HHV-6 Variant A.The tropism of HHV-6 for thyroid cells was verified by infection of Nthy-ori3-1, a thyroid follicular epithelial cell line, showing that thyrocytes are permissive to HHV-6 replication, which induces de novo expression of HLA class II antigens. Furthermore, HHV-6-infected Nthy-ori3-1 cells become targets for NK-mediated killing, NK cells from HT patients show a significantly more efficient killing of HHV-6 infected thyroid cells than healthy controls, and HT patients have increased T-cell responses to HHV-6 U94 protein, associated to viral latency. These observations suggest a potential role for HHV-6 (possibly variant A) in the development or triggering of HT.

Human herpesvirus 6 (HHV-6) like other herpesviruses, expresses sequentially immediate early (IE), early, and late genes during lytic infection. Evidence of ability to establish latent infection has not been available, but by analogy with other herpesviruses it could be expected that IE genes that regulate and transactivate late genes would not be expressed. We report that peripheral blood mononuclear cells of healthy individuals infected with HHV-6 express the U94 gene, transcribed under IE conditions. Transcription of other IE genes (U16͞17, U39, U42, U81, U89͞90, U91) was not detected. To verify that U94 may play a role in the maintenance of the latent state, we derived lymphoid cell lines that stably expressed U94. HHV-6 was able to infect these cells, but viral replication was restricted. No cytopathic effect developed. Furthermore, viral transcripts were present in the first days postinfection and declined thereafter. A similar decline in the level of intracellular viral DNA also was observed. These findings are consistent with the hypothesis that the U94 gene product of HHV-6 regulates viral gene expression and enables the establishment and͞or maintenance of latent infection in lymphoid cells.

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The presence of human herpesvirus 6 (HHV-6) and human herpesvirus 7 (HHV-7) was investigated by the polymerase chain reaction in saliva specimens from healthy persons, donors affected by common cold or recurrent aphthous ulceration (RAU), and human immunodeficiency virus (HIV) positive patients, and in salivary gland biopsies. The sensitivity of the technique made it possible to detect as few as 5-10 target molecules in 15 microliters of saliva. HHV-6 was present in 63% of salivary gland biopsies and in 3% of salivas from healthy persons. No significant difference in the presence of HHV-6 was detected in specimens from donors with common cold, RAU, or HIV-infected patients. HHV-7 was present in 75% of salivary glands and in 55% of salivas from healthy persons. HHV-7 was detected with similar frequency in salivas from donors with common cold or RAU. Salivas from HIV-infected patients harbored HHV-7 with higher frequency (81%) and increased viral load. These results show that salivary glands are a site of persistent infection for both HHV-6 and HHV-7. However, the two viruses seem to differ in their biological properties: 1) HHV-6 is rarely present in saliva in detectable amounts, while HHV-7 is frequently detected; and 2) immunosuppression by acquired immunodeficiency syndrome (AIDS) increases the frequency of detection and the viral load of HHV-7, but does not have a significant effect on HHV-6 shedding in saliva.

Endothelial cells are important targets for herpesvirus infection. To evaluate the biological effects of human herpesvirus-6 (HHV-6) infection, adult heart microvascular and aortic endothelial cells were examined for in vitro susceptibility to HHV-6 and for the alterations induced by viral infection on the production of monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8). Analysis by reverse transcription-polymerase chain reaction and by in situ polymerase chain reaction showed that HHV-6 replicates in endothelium in the absence of cytopathic effects, and that viral sequences were present in 20% umbilical vein and in 10% aortic and 1% microvascular endothelium. HHV-6 infection upregulated the production of MCP-1 and IL-8, with differences observed between aortic and microvascular endothelium. These findings demonstrate that endothelial cells represent a potential reservoir for HHV-6 infection, and the altered pattern of chemokine production can lead to attraction of immunocompetent cells and to the development of inflammatory processes.

In this study the prevalence of human herpesvirus (HHV) 8 DNA was determined in biopsies from persons with lymphoproliferative disorders and in peripheral blood mononuclear cells (PBMC) from human immunodeficiency virus (HIV)-seronegative and HIV-infected persons. The results show that HHV-8 is present in 10% of biopsies from HIV-seronegative persons: HHV-8 is detected with similar prevalence values in HIV-infected patients with lymphoproliferative diseases, but the virus load is higher. HHV-8 was also found in PBMC. The presence of monoclonal Epstein-Barr virus (EBV) genomes in malignant lymphoproliferations was only infrequently associated with HHV-8 infection. Therefore, HHV-8 is fairly common in the population, and the lymphoid system could represent a reservoir of latently infected cells from which the virus may reactivate in conditions of immunodepression; furthermore, HHV-8 and EBV do not seem to act in conjunction in lymphomagenesis.

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