Engineered Lactobacilli for Use in Oral Vaccines Against Human Coronaviruses (COVID-19)

A Self-Administered Vaccination Method to combat COVID-19

At a Glance

​To avoid antibody-dependent enhancement (ADE), researches at Colorado State University in collaboration with North Carolina State University have developed an oral vaccine targeting the COVID-19 virus-host cell interaction which depends on protease cleavage of viral spike proteins.  Preventing cleavage has been shown to reduce virus infectivity by preventing exposure of viral fusion peptides.

On this premise, the group is currently validating and testing this novel orally-delivered vaccine against SARS-CoV-2.


Emergence of novel human coronaviruses from animal reservoirs has likely been ongoing throughout the history of humanity. Only recently has this come to our attention because of technological advances to detect new viruses and the devastating potential of rapid spread achieved by global movement of people. Despite persistent efforts, there are no efficacious vaccines available against human coronaviruses or most animal coronaviruses. Coronavirus infection in populations is characterized by a variety of virologic and serologic states that may not be associated with clinical disease. For example, virus shedding can vary in duration and may be episodic or persistent. Seropositivity does not predict virus shedding and may not persist once virus is cleared, so reinfection is possible. The outcome is that coronaviruses have adapted to continually churn within susceptible populations and under the right conditions can cause epidemic outbreaks.

Because the viral spike protein is responsible for binding the host cell receptor and because neutralizing antibodies against spike have been demonstrated, most coronavirus vaccines have targeted the spike protein as the key immunogen. Unfortunately, spike protein, including the host receptor binding domain (RBD) also induces antibodies that can enhance infection and accelerate disease. This is termed antibody-dependent enhancement (ADE) and is primarily mediated by IgG binding to Fcg receptors.


  • Oral vaccination – does not require cold-chain or medical personnel administration
  • Rapid and inexpensive to manufacture
  • Induces strong mucosal IgA response to reduce or prevent viral infection and replication at the respiratory and intestinal mucosa
  • Can be easily adapted to novel emerging coronaviruses
Last Updated: December 2021
Woman preparing to take her pills

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