Biology subjects

Martin, H. S.

Publications and source records attributed to Martin, H. S..

5 recordsLinked to original sources

bioRxiv2026

Enhancement of a STING Agonist Vaccine for Tuberculosis Using Locally Supercharged MS2 Viral Capsids

Mycobacterium tuberculosis (Mtb) infection kills more people worldwide than any other pathogen. While the Bacille Calmette-Guerin (BCG) vaccine for Mtb has been widely used for over a century, it provides insufficient protection to eradicate this disease. One of our labs has recently established that a protein antigen (H1) can be combined with a STING pathway agonist to achieve strong protection against Mtb in mice, with performance that exceeds that of the BCG vaccine. However, its reliance on a synthetic cyclic dinucleotide (CDN) with relatively poor cell uptake requires higher dosing levels, thus increasing costs. To increase the efficiency of this vaccine and provide a delivery strategy that could also be used in humans, the H1 Mtb antigen and CDN adjuvant were conjugated to genome-free MS2 viral capsids that included cationic mutations to increase cell uptake. Specifically, the H1 antigen was conjugated to the external surface of MS2 using a tyrosinase-mediated oxidative coupling reaction, and the native STING agonist cGAMP was coupled to internal cysteine residues through a reductively cleavable disulfide linker. The resulting MS2-H1 and MS2-cGAMP conjugates were then co-delivered for three doses of vaccination in mice before exposure to Mtb. The MS2-based vaccine platform was observed to have comparable efficacy to the original H1/CDN formulation, but its enhanced uptake properties enabled 57-fold less CDN and 3-fold less H1 antigen. Additionally, this vaccine elicited immune responses that have been previously demonstrated to correlate with protection. The ability of the capsid shells to protect the CDN cargo during transport allowed enzymatically produced, and thus readily accessible, cGAMP to be used instead of more costly CDNs that require many synthetic steps. This, combined with the reduced overall amount of CDN and H1 that was required, could lower the production costs of future vaccines substantially. Finally, the ability of the capsid-based carriers to bypass the membrane transporters for CDNs suggests that this enhanced vaccination platform is likely to exhibit improved human efficacy in future studies.

immunology↗

bioRxiv2026

Viral capsid delivery of cGAMP enhances STING-dependent antitumor immune response

Therapies to activate the STING immune response pathway represent promising potential anticancer treatments. However, the native STING activating molecule, 2,3-cGAMP, is a poor drug candidate due to its susceptibility to nuclease degradation and its relatively poor cell uptake. In this study, we present a nanoscale delivery vehicle based on the bacteriophage MS2 virus-like particle that can both protect cGAMP and deliver it into cells to access and bind cytosolic STING. MS2-delivered cGAMP achieved greatly increased STING activation potency relative to both free cGAMP and a nuclease-resistant synthetic cGAMP analog. In an in vivo murine colon carcinoma model, MS2-cGAMP elicited significant and prolonged antitumor activity in a STING-dependent manner at 50-fold lower concentrations relative to free cGAMP and synthetic analogs. These results demonstrate that MS2 delivery of cGAMP can yield a highly potent STING agonist immunotherapy with in vivo anticancer activity.

immunology↗

bioRxiv2025

Engineered MS2 Virus Capsids for Cellular Display of Peptide Antigens

Our ability to respond to emerging pandemics and pathogen resistance relies critically on our ability to build vaccines quickly and efficiently. In this report we used an efficient enzymatic oxidative coupling reaction to create a viral capsid-based vaccine platform that is modular and quickly adaptable for many different pathogens. Tyrosinase-mediated oxidative coupling was used to conjugate C-terminal tyrosine residues on peptide antigens to cysteine residues installed inside MS2 viral capsids. This strategy is particularly promising because the capsids protect the internally conjugated peptides from protease degradation before they are delivered into cells. The vaccine constructs were tested for MHC presentation followed by T-cell activation. Mutants of the MS2 capsid itself activated DC2.4 cells, serving as an adjuvant to help induce the immune response to delivered antigens. The MS2-peptide constructs were shown to be stable in serum, activate DC2.4 cells, and lead to MHC-presentation of peptide antigens with subsequent activation of antigen-specific T-cell hybridomas. Taken together, these results demonstrate effective activation of the adaptive immune system in vitro. This synthetic platform can be used to build new vaccines for many different diseases for which immunodominant peptide antigens are known because the antigens can be quickly interchanged while the MS2 scaffold remains the same. Additionally, this platform allows for multiple peptide antigens to be delivered simultaneously in each capsid, which could provide enhanced immunity against resistant strains and be useful for cancer vaccine development.

biochemistry↗

bioRxiv2024

Cytosolic delivery of anionic cyclic dinucleotide STING agonists with locally supercharged viral capsids

Cyclic dinucleotide (CDN) STING agonists represent a powerful new immunotherapy treatment modality and are a class of nucleotide-based therapies with broad clinical potential. However, they face practical challenges for administration, largely due to their poor pharmacological properties. We report the development of a drug delivery platform for CDNs and other anionic small-molecule drugs using bacteriophage MS2 viral capsids with engineered cationic residues. Relative to viral capsids lacking locally supercharged regions, these assemblies exhibit substantial increases in mammalian cell uptake while avoiding cell toxicity and hemolysis. CDN drugs were covalently attached to the interior capsid surfaces through reductively cleavable disulfide linkers, which allowed for traceless drug release upon cell entry and exposure to reductive cytosolic environments. MS2-mediated CDN delivery into immune cell populations resulted in an approximately 100-fold increase in delivery efficiency compared to free drugs and showed enhanced STING activation as well as downstream cytokine release.

biochemistry↗

bioRxiv2023

Rapid assembly of SARS-CoV-2 genomes reveals attenuation of the Omicron BA.1 variant through NSP6

Although the SARS-CoV-2 Omicron variant (BA.1) spread rapidly across the world and effectively evaded immune responses, its viral fitness in cell and animal models was reduced. The precise nature of this attenuation remains unknown as generating replication-competent viral genomes is challenging because of the length of the viral genome (30kb). Here, we designed a plasmid-based viral genome assembly and rescue strategy (pGLUE) that constructs complete infectious viruses or noninfectious subgenomic replicons in a single ligation reaction with >80% efficiency. Fully sequenced replicons and infectious viral stocks can be generated in 1 and 3 weeks, respectively. By testing a series of naturally occurring viruses as well as Delta-Omicron chimeric replicons, we show that Omicron nonstructural protein 6 harbors critical attenuating mutations, which dampen viral RNA replication and reduce lipid droplet consumption. Thus, pGLUE overcomes remaining barriers to broadly study SARS-CoV-2 replication and reveals deficits in nonstructural protein function underlying Omicron attenuation.

microbiology↗