Mudrick, Haley

Background: Adeno-associated viruses (AAVs) are widely used vectors for in vivo gene therapy, but their standard storage at −80 °C limits deployment in regions lacking ultracold infrastructure. Strategies enabling stable AAV storage at higher temperatures are needed to support global distribution. Methods: Nine AAV serotypes were lyophilized in simple sucrose-based buffers. Post-lyophilization vector integrity was assessed by measuring in vitro transduction efficiency using a luciferase reporter in cell-based assays. Stability of selected serotypes (AAV2.5 and AAV6) was further evaluated over 8 weeks under varying storage temperatures. Results: Lyophilization in sucrose preserved transduction activity for all tested serotypes (AAV1, AAV2, AAV2.5, AAV3, AAV4, AAV5, AAV6, AAV8, AAV9, and AAVrh10). Notably, AAV2, AAV2.5, and AAV6 exhibited 3- to 6-fold increases in transduction, an effect attributable to the sucrose excipient rather than the lyophilization process itself. Long-term stability of lyophilized vectors varied by serotype, temperature, and vial-seal integrity. AAV6 retained full activity for at least 8 weeks when stored at 4 °C or −20 °C. Conclusions: AAV vectors can be effectively lyophilized in simple sucrose solutions, enabling storage at standard −20 °C freezer temperatures while maintaining functional activity. Optimization of lyophilization buffers and excipients may further extend AAV stability at higher temperatures, improving feasibility for global gene therapy deployment.

Background: Long-lived, re-activatable immunity to SARS-CoV-2 and its emerging variants will rely on T cells recognizing conserved regions of viral proteins across strains. Heterologous prime–boost regimens can elicit elevated levels of circulating CD8+ T cells that provide a reservoir of first responders upon viral infection. Although most vaccines are currently delivered intramuscularly (IM), the initial site of infection is the nasal cavity. Methods: Here, we tested the hypothesis that a heterologous prime and boost vaccine regimen delivered intranasally (IN) will generate improved immune responses locally at the site of virus infection compared to intramuscular vaccine/booster regimens. Results: In a transgenic human ACE2 murine model, both a Spike-expressing single-cycle adenovirus (SC-Ad) and an IFNß safety-enhanced replication-competent Vesicular Stomatitis Virus (VSV) platform generated anti-Spike antibody and T-cell responses that diminished with age. Although SC-Ad-Spike boosted a prime with VSV-Spike-mIFNß, SC-Ad-Spike alone induced maximal levels of IgG, IgA, and CD8+ T-cell responses. Conclusions: There were significant differences in T-cell responses in spleens compared to lungs, and the intranasal boost was significantly superior to the intramuscular boost in generating sentinel immune effectors at the site of the virus encounter in the lungs. These data show that serious consideration should be given to intranasal boosting with anti-SARS-CoV-2 vaccines.

Most gene-based severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines are nonreplicating vectors. They deliver the gene or messenger RNA to the cell to express the spike protein but do not replicate to amplify antigen production. This study tested the utility of replication in a vaccine by comparing replication-defective adenovirus (RD-Ad) and replicating single-cycle adenovirus (SC-Ad) vaccines that express the SARS-CoV-2 spike protein. SC-Ad produced 100 times more spike protein than RD-Ad and generated significantly higher antibodies against the spike protein than RD-Ad after single immunization of Ad-permissive hamsters. SC-Ad–generated antibodies climbed over 14 weeks after single immunization and persisted for more than 10 months. When the hamsters were challenged 10.5 months after single immunization, a single intranasal or intramuscular immunization with SC-Ad-Spike reduced SARS-CoV-2 viral loads and damage in the lungs and preserved body weight better than vaccination with RD-Ad-Spike. This demonstrates the utility of harnessing replication in vaccines to amplify protection against infectious diseases.

Clostridium difficile causes nearly 500,000 infections and nearly 30,000 deaths each year in the U.S., which is estimated to cost $4.8 billion. C. difficile infection (CDI) arises from bacteria colonizing the large intestine and releasing two toxins, toxin A (TcdA) and toxin B (TcdB). Generating humoral immunity against C. difficile’s toxins provides protection against primary infection and recurrence. Thus, a vaccine may offer the best opportunity for sustained, long-term protection. We developed a novel single-cycle adenovirus (SC-Ad) vaccine against C. difficile expressing the receptor-binding domains from TcdA and TcdB. The single immunization of mice generated sustained toxin-binding antibody responses and protected them from lethal toxin challenge for up to 38 weeks. Immunized Syrian hamsters produced significant toxin-neutralizing antibodies that increased over 36 weeks. Single intramuscular immunization provided complete protection against lethal BI/NAP1/027 spore challenge 45 weeks later. These data suggest that this replicating vaccine may prove useful against CDI in humans.

Most infections occur at mucosal surfaces. Providing a barrier of protection at these surfaces may be a useful strategy to combat the earliest events in infection when there are relatively few pathogens to address. The majority of vaccines are delivered systemically by the intramuscular (IM) route. While IM vaccination can drive mucosal immune responses, mucosal immunization at intranasal (IN) or oral sites can lead to better immune responses at mucosal sites of viral entry. In macaques, IN immunization with replicating single-cycle adenovirus (SC-Ads) and protein boosts generated favorable mucosal immune responses. However, there was an apparent “distance effect” in generating mucosal immune responses. IN immunization generated antibodies against HIV envelope (env) nearby in the saliva, but weaker responses in samples collected from the distant vaginal samples. To improve on this, we tested here if SC-Ads expressing genetic adjuvants could be used to amplify antibody responses in distant vaginal samples when they are codelivered with SC-Ads expressing clade C HIV env immunogen. SC-Ads env 1157 was coadministered with SC-Ads expressing 4-1BBL, granulocyte macrophage colony-stimulating factor (GMCSF), IL-21, or Clostridoides difficile (C. diff.) toxin fragments by IN or IM routes. These data show that vaginal antibody responses were markedly amplified after a single immunization by the IN or IM routes, with SC-Ad expressing HIV env if this vaccine is complemented with SC-Ads expressing genetic adjuvants. Furthermore, the site and combination of adjuvants appear to “tune” these antibody responses towards an IgA or IgG isotype bias. Boosting these priming SC-Ad responses with another SC-Ad or with SOSIP native-like env proteins markedly amplifies env antibody levels in vaginal washes. Together, this data may be useful in informing the choice of route of delivery adenovirus and peptide vaccines against HIV-1.