Mucosal immune probiotic vector vaccines: Development and prospects for application in COVID-19

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic of infectious disease characterized by significant morbidity, symptomatic manifestations, and severe outcomes. Vaccines have proven to be an effective means of impeding the transmission of SARS-CoV-2, and have been widely employed globally. Despite breakthroughs such as mRNA vaccine, intramuscular COVID-19 vaccine still faces numerous chanllenges, such as failure to completely avoid infections, high cost, and difficult transport conditions. The mucosa is the primary site through which SARS-CoV-2 invades the body and may induce effective immune responses. In the face of the increasing immune escape capacity of the Omicron variants and the potential outbreak of a new round of epidemics, it is imperative to develop a new generation of mucosal immune vaccines to prevent infection, which is mainly transmitted through the respiratory tract, along with its severe and fatal consequences. Probiotics have not only been used as safe raw materials for fermented foods but have also been developed as oral or nasal vaccine vectors for various pathogens in recent years, showing good mucosal and systemic immune effects in animals or humans. Although the antigen delivery technology based on protein anchoring on the surface of probiotics is rarely applied to COVID-19, probiotic-based vaccines aim at a new development direction for COVID-19 vaccines with low cost, high safety, and potential mucosal immune programs. In this review, we will discuss in detail the feasibility, advantages, and possible limitations of probiotics as a mucosal immune vaccine vector, which will be conducive to coping with the current situation of COVID-19.