Longhorn Vaccines and Diagnostics Presents Compelling Data on LHNVD-303 Vaccine for Sepsis Related to Bacterial Infections at the World Vaccine Congress

BETHESDA, Md. & GAITHERSBURG, Md.--(BUSINESS WIRE)--Longhorn Vaccines and Diagnostics, a One Health company developing vaccines and diagnostic tools for global public health and zoonosis concerns, presented new data at the World Vaccine Congress 2025 on LHNVD-303, the company's composite peptide vaccine for sepsis due to bacterial infections and its applications in inflammatory diseases. The World Vaccine Congress took place in Washington, D.C. from April 22-24.

Sepsis is a life-threatening complication of bacterial infections that triggers an immune response to circulating pathogens and toxins while driving systematic inflammation. Current treatments for these bacterial infections rely heavily on antibiotics and supportive care, which is ineffective for the growing number of antimicrobial resistant (AMR) strains.

To overcome these challenges, LHNVD-303 contains a breakthrough design as a novel, unconjugated, broad-spectrum peptide vaccine combining conserved epitopes from lipopolysaccharide (LPS), peptidoglycan (PGN), and lipoteichoic acid (LTA) —three key bacterial cell wall components. The vaccine is also formulated with a universal T cell epitope and adjuvanted with AddaVax to boost immunogenicity.

“LHNVD-303 is a broad-based composite peptide vaccine designed to kill gram-positive and gram-negative bacteria and bind and clear the toxins they release, with the goal of preventing bacterial infections and reducing acute and chronic inflammation without compromising the immune system,” said Longhorn Vaccine and Diagnostics President Jeff Fischer. “In animal studies to date, LHNVD-303 has shown powerful activity in its ability to generate broad antibody responses, kill harmful live bacteria, and bind key toxins that cause systematic inflammation, which could have wide ranging applications from inflammaging to sepsis. We plan to continue our study of LHNVD-303 while rapidly progressing an extended half-life monoclonal antibody cocktail comprised of the same targets.”

Longhorn's animal model presentation, titled, “A Broad-Based Composite Peptide Vaccine Targeting Conserved Bacterial Cell Wall and Toxin Epitopes: Towards the Prevention of Sepsis and Inflammation,” demonstrated several outcomes with transformative global implications.

Broad and Effective Antibody Response

LHNVD-303 generated high-titer IgG1 antibodies in both mice and pigs against LPS, PGN, and LTA, confirming the ability to target conserved epitopes. Antisera demonstrated strong binding to multiple gram-positive and gram-negative bacteria, including Staphylococcus aureus, Mycobacterium smegmatis, E. coli, and Group B Streptococcus.

Functional Efficacy – Not Just Binding, But Killing

LHNVD-303 demonstrated potent opsonophagocytic killing activity against live bacteria using U-937 macrophage-like cells. Antibodies promoted functional immune clearance, not just recognition, underscoring their therapeutic relevance.

Dual Impact on Infection and Inflammation

By targeting conserved bacterial cell wall structures and toxins, the vaccine-induced antibodies are positioned to neutralize pathogens and reduce systemic inflammation—offering protection not only against infection, but also against sepsis and chronic inflammation. LHNVD-303's non-reactogenic profile in pigs supports its safety and tolerability in large animal models.

Implications for AMR and Healthy Aging

By reducing bacterial burden and inflammatory toxin load, the vaccine holds promise to reduce antibiotic use, a key strategy in addressing the global AMR crisis. It also has the potential to mitigate inflammaging—chronic, low-grade inflammation linked to aging and degenerative diseases—through suppression of bacterial-driven immune activation.

For more information about Longhorn, visit www.LHNVD.com.

About Longhorn Vaccines and Diagnostics

Longhorn Vaccines and Diagnostics is a closely held One Health company based in Maryland that is developing broad coverage vaccines and diagnostic tools for worldwide public health concerns such as anti-microbial resistance, sepsis and to prevent future pandemics. Since its inception in 2006, Longhorn has focused on developing broad coverage vaccines and diagnostic tools that can impact a pandemic on a global scale and at all socio-economic levels. Since pandemics flow between humans and animals, Longhorn products play a significant role to surveil, diagnose, prevent and treat the next infectious disease.

Longhorn’s core diagnostic product, PrimeStore® Molecular Transport Medium (MTM), is a patented, FDA cleared, state-of-the-art ambient temperature molecular diagnostic collection and transport device that can help governments, global health organizations, and drug manufacturers improve the diagnosis and treatment of highly infectious diseases such as Influenza, SARS-CoV-2, and Mycobacterium tuberculosis (TB). Unlike standard devices for collecting and transporting virus samples, PrimeStore® MTM is the first molecular transport device that can safely deactivate pathogens and stabilize RNA and DNA, allowing enhanced point of care and ambient temperature transport for laboratory based molecular testing and characterization.