Recombinant adeno-associated virus serotype 9 AAV-RABVG expressing a Rabies Virus G protein confers long-lasting immune responses in mice and non-human primates

A modified recombinant adenovirus vector containing dual rabies virus G expression cassettes confers robust and long-lasting humoral immunity in mice, cats, and dogs

During the COVID-19 epidemic, the incidence of rabies has increased in several countries, especially in remote and disadvantaged areas, due to inadequate surveillance and declining immunization coverage. Multiple vaccinations with inactivated rabies virus vaccines for pre- or post-exposure prophylaxis are considered inefficient, expensive and impractical in developing countries. Herein, three modified human recombinant adenoviruses type 5 designated Adv-RVG, Adv-E1-RVG, and Adv-RVDG, carrying rabies virus G (RVG) expression cassettes in various combinations within E1 or E3 genomic regions, were constructed to serve as rabies vaccine candidates. Adv-RVDG mediated greater RVG expression both in vitro and in vivo and induced a more robust and durable humoral immune response than the rabies vaccine strain SAD-L16, Adv-RVG, and Adv-E1-RVG by more effectively activating the dendritic cells (DCs) - follicular helper T (Tfh) cells - germinal centre (GC) / memory B cells (MBCs) - long-lived plasma cells (LLPCs) axis with 100% survival after a lethal RABV challenge in mice during the 24-week study period. Similarly, dogs and cats immunized with Adv-RVDG showed stronger and longer-lasting antibody responses than those vaccinated with a commercial inactivated rabies vaccine and showed good tolerance to Adv-RVDG. In conclusion, our study demonstrated that simultaneous insertion of protective antigens into the E1 and E3 genomic regions of adenovirus vector can significantly enhance the immunogenicity of adenoviral-vectored vaccines, providing a theoretical and practical basis for the subsequent development of multivalent and multi-conjugated vaccines using recombinant adenovirus platform. Meanwhile, our data suggest Adv-RVDG is a safe, efficient, and economical vaccine for mass-coverage immunization.

rAAV expressing a COBRA-designed influenza hemagglutinin generates a protective and durable adaptive immune response with a single dose

Influenza remains a worldwide public health threat. Although seasonal influenza vaccines are currently the best means of preventing severe disease, the standard-of-care vaccines require frequent updating due to antigenic drift and can have low efficacy, particularly in vulnerable populations. Here, we demonstrate that a single administration of a recombinant adenovirus-associated virus (rAAV) vector expressing a computationally optimized broadly reactive antigen (COBRA)-derived influenza H1 hemagglutinin (HA) induces strongly neutralizing and broadly protective antibodies in naïve mice and ferrets with pre-existing influenza immunity. Following a lethal viral challenge, the rAAV-COBRA vaccine allowed for significantly reduced viral loads in the upper and lower respiratory tracts and complete protection from morbidity and mortality that lasted for at least 5 months post-vaccination. We observed no signs of antibody waning during this study. CpG motif enrichment of the antigen can act as an internal adjuvant to further enhance the immune responses to allow for lower vaccine dosages with the induction of unique interferon-producing CD4+ and CD8+ T cells specific to HA head and stem peptide sequences. Our studies highlight the utility of rAAV as an effective platform to improve seasonal influenza vaccines.

IMPORTANCE

Developing an improved seasonal influenza vaccine remains an ambitious goal of researchers and clinicians alike. With influenza routinely causing severe epidemics with the potential to rise to pandemic levels, it is critical to create an effective, broadly protective, and durable vaccine to improve public health worldwide. As a potential solution, we created a rAAV viral vector expressing a COBRA-optimized influenza hemagglutinin antigen with modestly enriched CpG motifs to evoke a robust and long-lasting immune response after a single intramuscular dose without needing boosts or adjuvants. Importantly, the rAAV vaccine boosted antibody breadth to future strains in ferrets with pre-existing influenza immunity. Together, our data support further investigation into the utility of viral vectors as a potential avenue to improve our seasonal influenza vaccines.

Single-injection subunit vaccine for rabies prevention using lentinan as adjuvant

Current rabies vaccines require 5 doses to provide full protection from the deadly virus, which significantly reduce the compliance of recipients. To minimize the number of immunizations herein single injection vaccines were developed. First a single injection vaccine was designed using rabies virus glycoprotein (G protein) as antigen. A time-controlled release system which uses dynamic layer-by-layer films as erodible coating was employed to accomplish multiply pulsatile releases of G protein. The single-injection vaccine elicits potent humoral and cellular immune responses comparable to the corresponding multi-dose ordinary vaccines because of their similar release pattern of G protein. To further improve its performance, a second single injection vaccine, in which lentinan was added as adjuvant, was designed. This single-injection vaccine again elicits humoral and cellular immune responses comparable to the corresponding multi-dose ordinary vaccines because of their similar release pattern of antigen and adjuvant. In addition, the second single-injection vaccine elicits higher level immune response and provides higher efficiency on virus inhibition than the first one because lentinan can booster immune response.

A single vaccination of nucleoside-modified Rabies mRNA vaccine induces prolonged highly protective immune responses in mice

Background

Rabies is a lethal zoonotic disease that kills approximately 60,000 people each year. Although inactivated rabies vaccines are available, multiple-dose regimensare recommended for pre-exposure prophylaxis or post-exposure prophylaxis,which cuts down the cost- and time-effectiveness, especially in low- and middle incomecountries.

Methods

We developed a nucleoside-modified Rabies mRNA-lipid nanoparticle vaccine (RABV-G mRNA-LNP) encoding codon-optimized viral glycoprotein and assessed the immunogenicity and protective efficacy of this vaccine in mice comparing to a commercially available inactivated vaccine.

Results

We first showed that, when evaluated in mice, a single vaccination of RABV-G mRNA with a moderate or high dose induces more potent humoral and T-cell immune responses than that elicited by three inoculations of the inactivated vaccine. Importantly, mice receiving a single immunization of RABV-G mRNA, even at low doses, showed full protection against the lethal rabies challenge. We further demonstrated that the humoral immune response induced by single RABV-G mRNA vaccination in mice could last for at least 25 weeks, while a two-dose strategy could extend the duration of the highly protective response to one year or even longer. In contrast, the three-dose regimen of inactivated vaccine failed to do so.

Conclusion

Our study confirmed that it is worth developing a single-dose nucleoside-modified Rabies mRNA-LNP vaccine, which could confer much prolonged and more effective protection.