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Trial Shows Oral Covid-19 Vaccine Produces Antibodies

White pills

(Heung Soon, Pixabay,

20 July 2022. A clinical trial shows a Covid-19 vaccine taken as a tablet produces protective antibodies in nasal membranes that in some cases last for up to a year. A team from Vaxart Inc., a biotechnology company in South San Francisco that developed the vaccine, posted the data yesterday in a pre-publication manuscript not yet peer reviewed.

Vaxart creates preventive and therapeutic vaccines delivered as pills rather than injections. The company says its vaccines are designed to remain stable and workable at room temperatures, making it possible to ship and store the vaccines without refrigeration. Vaxart’s technology uses a form of adenovirus, a naturally occurring and generally benign virus often used in gene therapies, as the delivery vehicle for its vaccines. The company says the virus is engineered to remove its ability to replicate, while still remaining intact to function in the human gut.

With Vaxart vaccines, the adenovirus carrier contains an antigen designed to trigger an immune response and adjuvant molecules that increase that immune response. The company says its vaccines’ active ingredients are designed to interact with epithelial cells lining mucous membranes in the small intestine, delivering the antigen and adjuvant molecules. Vaxart says the modular design makes it possible to quickly create and test new vaccines using the same adenovirus delivery mechanism.

The company is developing two oral vaccines to protect against disease from SARS-CoV-2 infections, one vaccine addressing the virus’s S or spike protein and another targeting both the spike and nucleocapsid or N proteins. The paper posted yesterday reports on an early-stage clinical trial of the second Vaxart vaccine, code-named VXA-CoV2-1, with an antigen expressing both the spike and nucleocapsid genes and a double-stranded RNA adjuvant. The trial enrolled 35 healthy adult volunteers, age 18 to 54, all testing negative for Covid-19 at the time.

1.5 times as many as immunoglobulin A antibodies

Participants were randomly assigned to receive one high or low-dose VXA-CoV2-1 tablet, with five of the low-dose recipients given a second tablet four weeks later. The Vaxart team looked mainly for adverse reactions to the vaccine, both the usual immune-reaction symptoms after taking a vaccine, as well as unexpected or serious adverse effects. The researchers also took blood, saliva, and nasal swab samples immediately after receiving the vaccine tablets, and at one, six, and 12 months later, looking for production of protective antibodies. For comparison, the team took samples from a group of individuals recovering from Covid-19 infections in the previous eight months.

Results show 13 of the 35 participants, or 37 percent, experienced common vaccine reactions, such as mild fever, headache, or muscle aches, including most (60%) of the high-dose group. Five other participants reported unexpected adverse effects for up to 57 days after taking the vaccine. All of the adverse effects, say the authors, were rated mild or moderate.

After a month, nearly half of participants (46%) reported 1.5 times as many as immunoglobulin A or IgA antibodies against SARS-CoV-2 in their nasal mucous membranes as at the beginning of the study, including antibodies that bind to the delta and omicron variants. Between three and eight participants were found with IgA antibodies in their nasal membranes or saliva for as long as a year after taking the vaccine, with more antibodies than found in nasal samples from people who recovered from Covid-19 infections. However, only seven of the 35 participants (20%) reported increases in neutralizing antibodies in their blood serum.

The findings, say Vaxart, support continued development of its VXA-CoV2-1 tablet. “Two key observations in this study,” says Vaxart chief scientist and lead author Sean Tucker in a company statement, “were that vaccination induced a similar mucosal IgA response as seen in convalescent subjects, and that the vaccinated subjects appeared to have better neutralizing antibody potential in the mucosa than infected subjects. We are excited to explore these aspects in depth in future studies.”

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