RNAs in Epstein-Barr virions control early steps of infection.

Herpesviruses are dsDNA viruses, but their virions may additionally contain RNAs that can be transduced to recipient cells. The biological functions of herpes virion RNA species are unknown. Here we address this issue for EBV, a widespread human herpesvirus with oncogenic potential. We show that EBV-derived particles that include virions, virus-like particles, and subviral vesicles contain viral mRNAs, microRNAs, and other noncoding RNAs. Viral RNAs were transduced during infection and deployed immediate functions that enhanced EBV's capacity to transform primary B cells. Among these transduced viral RNAs, BZLF1 transcripts transactivated viral promoters triggering the prelatent phase of EBV infection, noncoding EBV-encoded RNA transcripts induced cellular cytokine synthesis, and BNLF2a mRNA led to immune evasion that prevented T-cell responses to newly infected B cells. Hence, transduced viral RNAs govern critical processes immediately after infection of B cells with EBV and likely play important roles in herpesviral infection in general

Murine gammaherpesvirus 68 glycoprotein 150 does not contribute to latency amplification <em>in vivo</em>.

Background: Murine gammaherpesvirus 68 (MHV-68) is used as a model to study the function of gammaherpesvirus glycoproteins. gp150 of MHV-68, encoded by open reading frame M7, is a positional homolog of gp350/220 of EBV and of gp35/37 of KSHV. Since it had been proposed that gp350/220 of EBV might be a suitable vaccine antigen to protect from EBV-associated diseases, gp150 has been applied as a model vaccine in the MHV-68 system. When analyzing the function of gp150, previous studies yielded conflicting results on the role of gp150 in latency amplification, and disparities between the mutant viruses which had been analyzed were blamed for the observed differences. Results: To further develop MHV-68 as model to study the function of gammaherpesvirus glycoproteins in vivo, it is important to know whether gp150 contributes to latency amplification or not. Thus, we re-evaluated this question by testing a number of gp150 mutants side by side. Our results suggest that gp150 is dispensable for latency amplification. Furthermore, we investigated the effect of vaccination with gp150 using gp150-containing exosomes. Vaccination with gp150 induced a strong humoral and cellular immune response, yet it did not affect a subsequent MHV-68 challenge infection. Conclusions: In this study, we found no evidence for a role of gp150 in latency amplification. The previously observed contradictory results on the role of gp150 in latency amplification were not related to differences between the mutant viruses which had been used

Tumour exosomes inhibit binding of tumour-reactive antibodies to tumour cells and reduce ADCC.

In order to grow within an immunocompetent host, tumour cells have evolved various strategies to cope with the host&#39;s immune system. These strategies include the downregulation of surface molecules and the secretion of immunosuppressive factors like IL-10 and PGE2 that impair the maturation of immune effector cells, among other mechanisms. Recently, tumour exosomes (TEX) have also been implicated in tumour-induced immune suppression as it has been shown that TEX can induce apoptosis in T lymphocytes. In this study, we extend our knowledge about immunosuppressive features of these microvesicles in that we show that TEX efficiently bind and sequester tumour-reactive antibodies and dramatically reduce their binding to tumour cells. Moreover, we demonstrate that this antibody sequestration reduces the antibody-dependent cytotoxicity by immune effector cells, which is among the most important anti-tumour reactions of the immune system and a significant activity of therapeutic antibodies. Taken together, these data point to the fact that tumour-derived exosomes interfere with the tumour-specific function of immune cells and constitute an additional mechanism how tumours escape from immune surveillance

Transcriptional activation by EBV nuclear antigen 1 is essential for the expression of EBV's transforming genes

EBV is a paradigm for human tumor viruses because, although it infects most people benignly, it also can cause a variety of cancers. Both in vivo and in vitro, EBV infects B lymphocytes in G(0), induces them to become blasts, and can maintain their proliferation in cell culture or in vivo as tumors. How EBV succeeds in these contrasting cellular environments in expressing its genes that control the host has not been explained. We have genetically dissected the EBV nuclear antigen 1 (EBNA1) gene that is required for replication of the viral genome, to elucidate its possible role in the transcription of viral genes. Strikingly, EBNA1 is essential to drive transcription of EBV's transforming genes after infection of primary B lymphocytes

A Virus-Like Particle-Based Epstein-Barr Virus Vaccine ▿

Epstein-Barr Virus (EBV) is an ubiquitous human herpesvirus which can lead to infectious mononucleosis and different cancers. In immunocompromised individuals, this virus is a major cause for morbidity and mortality. Transplant patients who did not encounter EBV prior to immunosuppression frequently develop EBV-associated malignancies, but a prophylactic EBV vaccination might reduce this risk considerably. Virus-like particles (VLPs) mimic the structure of the parental virus but lack the viral genome. Therefore, VLPs are considered safe and efficient vaccine candidates. We engineered a dedicated producer cell line for EBV-derived VLPs. This cell line contains a genetically modified EBV genome which is devoid of all potential viral oncogenes but provides viral proteins essential for the assembly and release of VLPs via the endosomal sorting complex required for transport (ESCRT). Human B cells readily take up EBV-based VLPs and present viral epitopes in association with HLA molecules to T cells. Consequently, EBV-based VLPs are highly immunogenic and elicit humoral and strong CD8+ and CD4+ T cell responses in vitro and in a preclinical murine model in vivo. Our findings suggest that VLP formulations might be attractive candidates to develop a safe and effective polyvalent vaccine against EBV