A single-dose live-attenuated YF17D-vectored SARS-CoV-2 vaccine candidate.

The expanding pandemic of coronavirus disease 2019 (COVID-19) requires the development of safe, efficacious and fast-acting vaccines. Several vaccine platforms are being leveraged for a rapid emergency response1. Here we describe the development of a candidate vaccine (YF-S0) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that uses live-attenuated yellow fever 17D (YF17D) vaccine as a vector to express a noncleavable prefusion form of the SARS-CoV-2 spike antigen. We assess vaccine safety, immunogenicity and efficacy in several animal models. YF-S0 has an excellent safety profile and induces high levels of SARS-CoV-2 neutralizing antibodies in hamsters (Mesocricetus auratus), mice (Mus musculus) and cynomolgus macaques (Macaca fascicularis), and-concomitantly-protective immunity against yellow fever virus. Humoral immunity is complemented by a cellular immune response with favourable T helper 1 polarization, as profiled in mice. In a hamster model2 and in macaques, YF-S0 prevents infection with SARS-CoV-2. Moreover, a single dose conferred protection from lung disease in most of the vaccinated hamsters within as little as 10 days. Taken together, the quality of the immune responses triggered and the rapid kinetics by which protective immunity can be attained after a single dose warrant further development of this potent SARS-CoV-2 vaccine candidate.

The Role of Epstein-Barr Virus in Modulating Key Tumor Suppressor Genes in Associated Malignancies: Epigenetics, Transcriptional, and Post-Translational Modifications.

Epstein-Barr virus (EBV) is ubiquitous and carried by approximately 90% of the world's adult population. Several mechanisms and pathways have been proposed as to how EBV facilitates the pathogenesis and progression of malignancies, such as Hodgkin's lymphoma, Burkitt's lymphoma, nasopharyngeal carcinoma, and gastric cancers, the majority of which have been linked to viral proteins that are expressed upon infection including latent membrane proteins (LMPs) and Epstein-Barr virus nuclear antigens (EBNAs). EBV expresses microRNAs that facilitate the progression of some cancers. Mostly, EBV induces epigenetic silencing of tumor suppressor genes, degradation of tumor suppressor mRNA transcripts, post-translational modification, and inactivation of tumor suppressor proteins. This review summarizes the mechanisms by which EBV modulates different tumor suppressors at the molecular and cellular levels in associated cancers. Briefly, EBV gene products upregulate DNA methylases to induce epigenetic silencing of tumor suppressor genes via hypermethylation. MicroRNAs expressed by EBV are also involved in the direct targeting of tumor suppressor genes for degradation, and other EBV gene products directly bind to tumor suppressor proteins to inactivate them. All these processes result in downregulation and impaired function of tumor suppressors, ultimately promoting malignances.

Biodistribution and environmental safety of a live-attenuated YF17D-vectored SARS-CoV-2 vaccine candidate.

New platforms are needed for the design of novel prophylactic vaccines and advanced immune therapies. Live-attenuated yellow fever vaccine YF17D serves as a vector for several licensed vaccines and platform for novel candidates. On the basis of YF17D, we developed an exceptionally potent COVID-19 vaccine candidate called YF-S0. However, use of such live RNA viruses raises safety concerns, such as adverse events linked to original YF17D (yellow fever vaccine-associated neurotropic disease [YEL-AND] and yellow fever vaccine-associated viscerotropic disease [YEL-AVD]). In this study, we investigated the biodistribution and shedding of YF-S0 in hamsters. Likewise, we introduced hamsters deficient in signal transducer and activator of transcription 2 (STAT2) signaling as a new preclinical model of YEL-AND/AVD. Compared with YF17D, YF-S0 showed improved safety with limited dissemination to brain and visceral tissues, absent or low viremia, and no shedding of infectious virus. Considering that yellow fever virus is transmitted by Aedes mosquitoes, any inadvertent exposure to the live recombinant vector via mosquito bites is to be excluded. The transmission risk of YF-S0 was hence compared with readily transmitting YF-Asibi strain and non-transmitting YF17D vaccine, with no evidence for productive infection of mosquitoes. The overall favorable safety profile of YF-S0 is expected to translate to other vaccines based on the same YF17D platform.

Live-attenuated YF17D-vectored COVID-19 vaccine protects from lethal yellow fever virus infection in mouse and hamster models.

BACKGROUND: The live-attenuated yellow fever vaccine YF17D holds great promise as alternative viral vector vaccine platform, showcased by our previously presented potent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine candidate YF-S0. Besides protection from SARS-CoV-2, YF-S0 also induced strong yellow fever virus (YFV)-specific immunity, suggestive for full dual activity. A vaccine concomitantly protecting from SARS-CoV-2 and YFV would be of great benefit for those living in YFV-endemic areas with limited access to current SARS-CoV-2 vaccines. However, for broader applicability, pre-existing vector immunity should not impact the potency of such YF17D-vectored vaccines. METHODS: The immunogenicity and efficacy of YF-S0 against YFV and SARS-CoV-2 in the presence of strong pre-existing YFV immunity were evaluated in mouse and hamster challenge models. FINDINGS: Here, we show that a single dose of YF-S0 is sufficient to induce strong humoral and cellular immunity against YFV as well as SARS-CoV-2 in mice and hamsters; resulting in full protection from vigorous YFV challenge in either model; in mice against lethal intracranial YF17D challenge, and in hamsters against viscerotropic infection and liver disease following challenge with highly pathogenic hamster-adapted YFV-Asibi strain. Importantly, strong pre-existing immunity against the YF17D vector did not interfere with subsequent YF-S0 vaccination in mice or hamsters; nor with protection conferred against SARS-CoV-2 strain B1.1.7 (Alpha variant) infection in hamsters. INTERPRETATION: Our findings warrant the development of YF-S0 as dual SARS-CoV-2 and YFV vaccine. Contrary to other viral vaccine platforms, use of YF17D does not suffer from pre-existing vector immunity. FUNDING: Stated in the acknowledgments.

Suppressors of Cytokine Signaling and Protein Inhibitors of Activated Signal Transducer and Activator of Transcriptions As Therapeutic Targets in Flavivirus Infections.

Flaviviruses cause significant human diseases putting more than 400 million people at risk annually worldwide. Because of migration and improved transportation, these viruses can be found on all continents (except Antarctica). Although a majority of the viruses are endemic in the tropics, a few [West Nile virus (WNV) and tick-borne encephalitis virus (TBEV)] have shown endemicity in Europe and North America. Currently, there are vaccines for the Yellow fever virus, Japanese encephalitis virus, and TBEV, but there is no effective vaccine and/or therapy against all other flaviviruses. Although there are intensive efforts to develop vaccines for Zika viruses, dengue viruses, and WNVs, there is the need for alternative or parallel antiviral therapeutic approaches. Suppressors of cytokine signaling (SOCS) and protein inhibitors of activated signal transducer and activator of transcription (STATs; PIAS), both regulatory proteins of the Janus kinase/STAT signaling pathway, have been explored as therapeutic targets in herpes simplex and vaccinia viruses, as well as in cancer therapy. In this review, we briefly describe the function of SOCS and PIAS and their therapeutic potential in flaviviral infections. [Figure: see text].

The Modulatory Effect of Lead Drug Candidates on Inflammatory Gene Expression in Sepsis: A Mini-Review.

Sepsis is a debilitating clinical syndrome of systemic inflammation in response to microorganisms especially Gram-positive and Gram-negative bacteria. A minority of sepsis cases could be due to non-pathogenic insult such as trauma. Much of the tissue and organ injury observed among septic patients is a consequence of the inflammatory response. The search for effective treatments of sepsis has led to several studies by different research groups across the globe. Although many targets and molecules have been identified, there is still no effective treatment for sepsis. The aim of this report is to review the literature on drugs and drug candidates against sepsis and how they modulate the expression of inflammatory genes. Many compounds have been identified to regulate inflammatory gene expression by interacting with targets such as topoisomerase 1 and nuclear factor kappa B, which regulate the production of pro- and anti-inflammatory cytokines. Even though these compounds appear promising as potential drugs against sepsis, no effective therapies have been discovered to date and thus the fight against sepsis continues.