# Surface Display of Avian H5 and H9 Hemagglutinin Antigens on Non-Genetically Modified Lactobacillus Cells for Bivalent Oral AIV Vaccine Development

## TL;DR

A new oral vaccine against two types of avian influenza uses non-modified bacteria to display virus antigens, inducing strong immune responses in mice.

## Contribution

A bivalent oral AIV vaccine using non-GMO lactobacilli for surface antigen display is developed and tested.

## Key findings

- Mouse immunization induced strong systemic IgG and mucosal IgA responses against both H5N1 and H9N2 HA1.
- HA1 proteins displayed on lactobacilli showed protease resistance, indicating natural antigen protection.
- The system offers a safe, multivalent vaccine platform using non-GMO probiotics.

## Abstract

A novel bivalent oral vaccine candidate against H5N1 and H9N2 avian influenza virus (AIV) was developed using Lactobacillus surface display technology without genetic modification. The hemagglutinin subunit 1 (HA1) antigens from both subtypes were fused to the surface layer-binding domain of Lactobacillus crispatus K313, expressed in Escherichia coli, and purified. Wild-type Lactobacillus johnsonii H31, isolated from chicken intestine, served as a delivery vehicle by adsorbing and stably displaying the HA1 proteins on its surface. This approach eliminates the need for bacterial engineering while utilizing lactobacilli’s natural capacity to protect surface-displayed antigens, as evidenced by HA1’s protease resistance. Mouse immunization studies demonstrated induction of strong systemic IgG and mucosal IgA responses against both H5N1 and H9N2 HA1. The system offers several advantages, including safety through non-GMO probiotics, potential for multivalent vaccine expansion, and intrinsic antigen protection by lactobacilli. These findings suggest this platform could enable development of cost-effective, multivalent AIV vaccines.