An Algae-Made RBD from SARS-CoV-2 Is Immunogenic in Mice

Area of Science:

• Vaccinology
• Immunology
• Biotechnology

Background:

• Sustaining population immunity against SARS-CoV-2 requires effective boosting strategies.
• Developing low-cost, easily administered oral vaccines is crucial for global accessibility.
• Algae present a viable, edible platform for producing and delivering immunogens.

Purpose of the Study:

• To evaluate the feasibility of a Chlamydomonas-based oral immunogen for SARS-CoV-2.
• To assess the stability and immunogenicity of algae-produced SARS-CoV-2 receptor-binding domain (RBD).

Main Methods:

• Production of SARS-CoV-2 RBD in Chlamydomonas algae.
• Oral administration of freeze-dried algae biomass containing the immunogen to mice.
• Analysis of systemic and mucosal humoral responses, including IgG subclasses.
• Assessment of antibody reactivity against SARS-CoV-2 variants (Delta and Omicron).

Main Results:

• The oral immunogen was stable in freeze-dried algae biomass.
• Oral administration induced systemic and mucosal humoral responses comparable to injected antigen with adjuvant.
• A sustained Th2-biased immune response was observed for over 4 months.
• Induced antibodies demonstrated cross-reactivity against Delta and Omicron variants.

Conclusions:

• Algae-based oral immunogens are a promising strategy for SARS-CoV-2 vaccine development.
• This approach could facilitate affordable and scalable booster vaccine administration.
• Further development could accelerate global immunization efforts.