New needle-free nasal vaccine shows promise for COVID-19

A new study, recently reported in mBio, highlights the first non-infectious, bacteriophage T4-based, multicomponent, needle and adjuvant-free mucosal vaccine. The team includes scientists from the Bacteriophage Medical Research Center, the Catholic University of America and the University of Texas Medical Branch, all US.

In experiments conducted in mice, intranasal administration of two doses of the phage T4-COVID-19 vaccine 21-days apart induced robust mucosal immunity, in addition to strong systemic humoral and cellular immune responses. The intranasal vaccine induced broad virus neutralisation antibody titres against multiple variants and triggered Th1-biased cytokine responses, strong CD4+ and CD8+ T-cell immunity, and high secretory IgA titres in sera and bronchoalveolar lavage of vaccinated mice. All these responses were much stronger in intranasally vaccinated mice than that induced by the injected vaccine. Furthermore, the nasal vaccine provided complete protection and sterilising immunity against the mouse-adapted SARS-CoV-2 MA10 strain, the ancestral WA-1/2020 strain, and the most lethal Delta variant in mouse models. 

Additionally, the T4-COVID-19 vaccine elicited broad virus-neutralising antibodies against SARS-CoV-2 variants in sera and bronchoalveolar lavage, did not affect the gut microbiota, exhibited minimal lung lesions in vaccinated and challenged mice and is stable at ambient temperature. 

“This intranasally administered vaccine generates superior mucosal immunity in mice in addition to inducing robust humoral and cell-mediated immune responses and provides complete protection and sterilising immunity against SARS-CoV-2 variants. The vaccine is stable, adjuvant-free and cost-effectively manufactured and distributed, making it a strategically important next-generation COVID-19 vaccine for ending this pandemic,” concluded senior authors, Dr Venigalla B. Rao and Dr Ashok K. Chopra. “This modular, needle-free, phage T4 mucosal vaccine delivery platform is an excellent candidate to design efficacious mucosal vaccines against other respiratory infections and for emergency preparedness against emerging epidemic and pandemic pathogens.”