Adenovirus-Based Vectors for the Development of Prophylactic and Therapeutic Vaccines

Seroprevalence of human adenovirus type 5 neutralizing antibodies in the Philippines

Human adenovirus (HAdV), particularly the HAdV type 5 (HAdV-5), has been extensively utilized in the development of vector vaccines due to its high immunogenicity, good safety profile, and ease of propagation. However, one of the main challenges in its use is the presence of pre-existing immunity among vaccine recipients. Pre-existing neutralizing antibodies (NAbs) can prevent the uptake of HAdV-5 vectors and reduce vaccine efficacy. Hence, this study investigated the seroprevalence of NAbs against HAdV-5 in urban and rural regions of the Philippines. Luciferase-based neutralization assay was performed on 391 plasma/serum samples. Out of these samples, 346 or 88.5% were positive for HAdV-5 NAbs, and the majority of them (56.8%) had high titers against the virus. Among the regions included in this study, Bicol (Region V) had the highest seroprevalence rate (94.1%). Our findings show that a significant number of adults in the Philippines have pre-existing immunity against HAdV-5. This supports the recommendation that vaccination programs in the country should consider implementing vaccination techniques, such as a prime-boost regimen or addition of booster doses, to address the potential negative effects of pre-existing HAdV-5 immunity in the efficacy of adenoviral vector-based vaccines.

Main Targets of Interest for the Development of a Prophylactic or Therapeutic Epstein-Barr Virus Vaccine

Epstein-Barr virus (EBV) is one of the most widespread viruses in the world; more than 90% of the planet's adult population is infected. Symptomatic primary infection by this Herpesviridae corresponds to infectious mononucleosis (IM), which is generally a benign disease. While virus persistence is often asymptomatic, it is responsible for 1.5% of cancers worldwide, mainly B cell lymphomas and carcinomas. EBV may also be associated with autoimmune and/or inflammatory diseases. However, no effective treatment or anti-EBV vaccine is currently available. Knowledge of the proteins and mechanisms involved in the different steps of the viral cycle is essential to the development of effective vaccines. The present review describes the main actors in the entry of the virus into B cells and epithelial cells, which are targets of interest in the development of prophylactic vaccines aimed at preventing viral infection. This review also summarizes the first vaccinal approaches tested in humans, all of which are based on the gp350/220 glycoprotein; while they have reduced the risk of IM, they have yet to prevent EBV infection. The main proteins involved in the EBV latency cycle and some of the proteins involved in the lytic cycle have essential roles in the oncogenesis of EBV. For that reason, these proteins are of interest for the development of therapeutic vaccines of which the objective is the stimulation of T cell immunity against EBV-associated cancers. New strategies aimed at broadening the antigenic spectrum, are currently being studied and will contribute to the targeting of the essential steps of the viral cycle, the objective being to prevent or treat the diseases associated with EBV.

Cloning and rescue of the genome of Bombyx mori bidensovirus, and characterization of a recombinant virus

Background

Bombyx mori bidensovirus (BmBDV), which belongs to the Bidnaviridae family established by the International Committee on Taxonomy of Viruses in 2011, was the first bidensovirus identified in insects. The structure of BmBDV is similar to that of parvoviruses, while its replication is similar to that of adenoviruses. Although BmBDV has the potential to be used as a tool in biological pest control and as an expression vector, virus rescue has been a bottleneck in the application of this virus.

Methods

In this study, we constructed a full-length genomic clone of BmBDV and showed that its terminal structure was restored. A recombinant BmBDV that expressed the green fluorescence protein (GFP) gene was constructed. Then, BmN cells, which are an ovarian cell line, were co-transfected with the linearized genome using continuous culture and expanded cell culture methods.

Results

The results showed that the GFP gene was expressed successfully, and that cell lesions occurred in virus-infected cells. Furthermore, typical densonucleosis viruses were observed in reinfected silkworm larvae and larval midgut tissues infected by BmBDV, as evidenced by the emission of green fluorescence.

Conclusions

Overall, these results suggest that the virus could be rescued from the infected BmN cells after co-transfection with the linear full length virus genome.