Human herpesvirus 6 and cytomegalovirus infections in children with human immunodeficiency virus infection and cancer

Optimization of immunotherapy in elderly cancer patients

Increasing evidence has revealed the incidence of cancer augments with aging, which could be attributed to a multitude of age-associated changes including the dysregulation of the immune system. Although many reports demonstrate the efficacy of cancer immunotherapies in numerous preclinical studies, most experiments have been performed in young animals. Studies from our group and others show that cancer immunotherapy could be ineffective in old mice, even though the same therapeutic treatment works efficiently in young mice. Given that cancer occurs mostly in the elderly, we should take age-associated immune dysregulation into consideration to achieve the effectiveness of immunotherapeutic interventions in the old. Understanding both age-related and tumor-related immune alterations might be equally important in improving the effectiveness of immunotherapy. This article reviews a number of age-associated immune alterations with specific attention given to the impact on antitumor responses, and also discusses possible strategies for optimization of immunotherapeutic interventions in the elderly.

The roles of viruses in brain tumor initiation and oncomodulation

While some avian retroviruses have been shown to induce gliomas in animal models, human herpesviruses, specifically, the most extensively studied cytomegalovirus, and the much less studied roseolovirus HHV-6, and Herpes simplex viruses 1 and 2, currently attract more and more attention as possible contributing or initiating factors in the development of human brain tumors. The aim of this review is to summarize and highlight the most provoking findings indicating a potential causative link between brain tumors, specifically malignant gliomas, and viruses in the context of the concepts of viral oncomodulation and the tumor stem cell origin.

Epigenetic control during lymphoid development and immune responses: aberrant regulation, viruses, and cancer

Methylation of cytosines controls a number of biologic processes such as imprinting and X chromosomal inactivation. DNA hypermethylation is closely associated with transcriptional silencing, while DNA hypomethylation is associated with transcriptional activation. Hypoacetylation of histones leads to compact chromatin with reduced accessibility to the transcriptional machinery. Methyl-CpG binding proteins can recruit corepressors and histone deacetylases; thus, the interplay between these epigenetic mechanisms regulates gene activation. Methylation has been implicated as an important mechanism during immune development, controlling VDJ recombination, lineage-specific expression of cell surface antigens, and transcriptional regulation of cytokine genes during immune responses. Aberrations in epigenetic machinery, either by genetic mutations or by somatic changes such as viral infections, are associated with early alterations in chronic diseases such as immunodeficiency and cancer.

Identification and characterization of the gene products of open reading frame U86/87 of human herpesvirus 6

The human herpesvirus 6 (HHV-6) immediate early-A locus (IE-A) locates in the position analogous to the human cytomegalovirus (HCMV) major IE (MIE) locus that is well-known to play critical roles in viral infection. Similarly to HCMV MIE, HHV-6 IE-A consists of two genetic units, IE1 and IE2, corresponding to open reading frames U90-U89 and U90-U86/87, respectively. However, the HHV-6 IE-A locus exhibits limited sequence homology with the HCMV MIE locus. In this study, to characterize HHV-6 IE2 gene products, polyclonal antibodies against four domains of the U86/87 open reading frame were generated by immunization of rabbits with bacterially-expressed proteins. Three polypeptides derived from the U86/87 region with apparent molecular masses of 100, 85 and 55 kD were detected in HHV-6-infected cells 3 days after infection, while IE1 polypeptides with apparent molecular mass greater than 170 kD were detectable as early as 8 h. Mapping of the IE2 gene products with the antibodies suggests differential splicing and alternative translation initiation in the IE2 genetic unit. The IE2 products show a mixed cytoplasmic and nuclear localization pattern. In addition, the 437 amino acid carboxyl-terminus domain bound to a DNA fragment containing the putative IE-A promoter. These results suggest that HHV-6 IE2 plays a critical role in transcriptional regulation and viral growth as does HCMV IE2, although it is likely that HHV-6 IE2 has expression kinetics different from HCMV IE2.