Despite the recent progress in the development of new antiviral agents, hepatitis C virus (HCV) infection remains a major global health problem, and there is a need for a preventive vaccine. We previously reported that adenoviral vectors expressing HCV nonstructural proteins elicit protective T cell responses in chimpanzees and were immunogenic in healthy volunteers. Furthermore, recombinant HCV E1E2 protein formulated with adjuvant MF59 induced protective antibody responses in chimpanzees and was immunogenic in humans. To develop an HCV vaccine capable of inducing both T cell and antibody responses, we constructed adenoviral vectors expressing full-length and truncated E1E2 envelope glycoproteins from HCV genotype 1b. Heterologous prime-boost immunization regimens with adenovirus and recombinant E1E2 glycoprotein (genotype 1a) plus MF59 were evaluated in mice and guinea pigs. Adenovirus prime and protein boost induced broad HCV-specific CD8 Hepatitis C virus (HCV) infection is a major global health problem affecting an estimated 170 million people worldwide, occurring among persons of all ages, genders, races, and regions of the world. Chronically infected subjects are at risk of developing progressive liver disease, including cirrhosis, and primary hepatocellular carcinoma (1). Although the recent introduction of directly acting antiviral drugs (DAAs) has improved therapy for chronic HCV and interferon (IFN)-free regimens are on the horizon (2), treatment success may be limited by a range of factors, including awareness of infection status, access to and cost of therapy, relative efficacy of different regimens for specific HCV genotypes, adverse effects, comorbidities (e.g., cirrhosis or HIV coinfection), and host factors. For these reasons, the development of a safe, effective, and affordable preventive vaccine against HCV is the optimal long-term goal to control the global epidemic (3).Approximately 20% of infected individuals clear the virus spontaneously, and resolution is associated with HLA type and with potent, multispecific, and long-lasting T cell responses (4). T cell depletion experiments with chimpanzees confirmed the essential role of cellular immunity in controlling HCV infection (5). Moreover, antibodies targeting the HCV envelope glycoproteins have been shown to neutralize infection in vitro (6, 7) and to protect against virus challenge in the human liver-Alb-uPA/SCID murine model (8)(9)(10). A recent report demonstrated that spontaneous clearance of HCV is associated with the early appearance of a broadly neutralizing antibody response (11). Recombinant E1E2 glycoproteins have been shown to induce cross-neutralizing antibody responses against het-

Since the emergence of the novel coronavirus SARS-CoV-2 in late 2019, the COVID-19 pandemic has hindered social life and global economic activity. As of July 2021, SARS-CoV-2 has caused over four million deaths. The rapid spread and high mortality of the disease demanded the international scientific community to develop effective vaccines in a matter of months. However, unease about vaccine efficacy has arisen with the spread of the SARS-CoV-2 variants of concern (VOCs). Time- and cost-efficient in vitro neutralization assays are widely used to measure neutralizing antibody responses against VOCs. However, the extent to which in vitro neutralization reflects protection from infection remains unclear. Here, we describe common neutralization assays based on infectious and pseudotyped viruses and evaluate their role in testing neutralizing responses against new SARS-CoV-2 variants. Additionally, we briefly review the recent findings on the immune response elicited by available vaccines against major SARS-CoV-2 variants, including Alpha, Beta, Gamma, and Delta.

Hepatitis C virus (HCV) is a globally disseminated human pathogen for which no vaccine is currently available. HCV is highly diverse genetically and can be classified into 7 genotypes and multiple sub-types. Due to this antigenic variation, the induction of cross-reactive and at the same time neutralizing antibodies is a challenge in vaccine production. Here we report the analysis of immunogenicity of recombinant HCV envelope glycoproteins from genotypes 1a, 1b and 2a, with a Flag tag inserted in the hypervariable region 1 of E2. This modification did not affect protein expression or conformation or its capacity to bind the crucial virus entry factor, CD81. Importantly, in immunogenicity studies on mice, the purified E2-Flag mutants elicited high-titer, cross-reactive antibodies that were able to neutralize HCV infectious particles from two genotypes tested (1a and 2a). These findings indicate that E1E2-Flag envelope glycoproteins could be important immunogen candidates for vaccine aiming to induce broad HCV-neutralizing responses.

Tick-borne encephalitis virus (TBEV), of the genus Flavivirus, is a causative agent of severe encephalitis in endemic regions of northern Asia and central and northern Europe. Interferon induced transmembrane proteins (IFITMs) are restriction factors that inhibit the replication cycles of numerous viruses, including flaviviruses such as the West Nile virus, dengue virus, and Zika virus. Here, we demonstrate the role of IFITM1, IFITM2, and IFITM3 in the inhibition of TBEV infection and in protection against virus-induced cell death. We show the most significant role being that of IFITM3, including the dissection of its functional motifs by mutagenesis. Furthermore, through the use of CRISPR–Cas9-generated IFITM1/3-knockout monoclonal cell lines, we confirm the role and additive action of endogenous IFITMs in TBEV suppression. However, the results of co-culture assays suggest that TBEV might partially escape IFN- and IFITM-mediated suppression during high-density co-culture infection when the virus enters naïve cells directly from infected donor cells. Thus, cell-to-cell spread may constitute a strategy for virus escape from innate host defenses. Importance: TBEV infection may result in encephalitis, chronic illness or death. TBEV is endemic in northern Asia and Europe; however, due to climate change, new endemic centers arise. Although effective TBEV vaccines have been approved, vaccination coverage is low, and, due to the lack of specific therapeutics, infected individuals depend on their immune responses to control the infection. The IFITM proteins are components of the innate antiviral defenses that suppress cell entry of many viral pathogens. However, no studies regarding the role of IFITM proteins in the TBEV infection have been published so far. Understanding of antiviral innate immune responses is crucial for future development of antiviral strategies. Here, we show the important role of IFITM proteins in the inhibition of TBEV infection and virus-mediated cell death. However, our data suggest that TBEV cell-to-cell spread may be less prone to both IFN- and IFITM-mediated suppression, potentially facilitating escape from IFITM-mediated immunity.

Despite available treatment, Hepatitis C remains one of most serious burdens to public health. Current therapy based on pegylated interferon-alpha and ribavirin has significant side effects and its effectiveness varies for different genotypes of the virus. Four novel drugs - viral protease inhibitors (telaprevir, boceprevir, simeprevir) and polymerase inhibitor - sofosbuvir have been introduced in last years for use in combination with standard-of-care treatment. For the first time interferon free therapies were approved with the use of combination of sofosbuvir+ribavirin. New therapies improve virological response rates but also increase the cost, side effects and raise the issue of drug resistance. Numerous novel anti-HCV compounds have been evaluated in advanced clinical trials including inhibitors of viral proteins (protease, polymerase and NS5A) and inhibitors of host factors involved in HCV replication (cyclophilin A, microRNA - miR-122). New interferon-free therapies reducing severe side effects are expected to enter the market within few months. At the same time efforts are undertaken to determine the host and viral factors with predictive value for HCV treatment response, enabling personalized therapy approach. The main success in this field was the discovery of interleukin IL28B polymorphism, which correlates with positive standard-of-care treatment response. An effective vaccination may be an alternative for antiviral drugs, but no anti-HCV vaccine is available currently. It is well proved that successful vaccination should induce antibody and T-cell responses specific against a range of HCV genotypes. With this aim, new subunit and genetic candidate vaccines have been evaluated in I and II phase clinical trials. This review summarizes the recent developments in the field of new drug development and vaccine studies against hepatitis C virus.