# Evaluation of Mycoplasma mycoides subsp. mycoides antigens capable of stimulating host IRG-47 release identifies Mmm604, Mmm605, and Mmm606 as potential subunit vaccine antigens

## TL;DR

This study identifies three proteins from Mycoplasma mycoides that could be used to develop a new subunit vaccine for contagious bovine pleuropneumonia.

## Contribution

The study introduces Mmm604, Mmm605, and Mmm606 as novel antigen candidates for a subunit vaccine against CBPP.

## Key findings

- Mmm604, Mmm605, and Mmm606 induce IRG-47 release and stimulate cellular and humoral immune responses in mice.
- These proteins activate CD8+ T cells and promote a mixed Th1/Th2/Th17 immune response.
- Mmm604 and Mmm606 also trigger mucosal antibody responses in mice.

## Abstract

Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides subsp. mycoides (Mmm), is a devastating cattle disease with high morbidity and mortality, threatening cattle productivity in Sub-Saharan Africa and potentially in parts of Asia. Cross-border livestock trade increases the risk of CBPP introduction or reintroduction. Current vaccines were developed from attenuated Mmm strains in the last century and face limitations regarding animal welfare, immunity duration, and adverse reactions, necessitating new vaccine strategies. Subunit vaccines offer a promising alternative, but identifying effective antigens is critical. Given the key role of cellular immunity in CBPP control, we focused on antigen identification that elicits a host cellular immune response. This study explores antigen candidates based on Ben-181, a vaccine that successfully eradicated CBPP in China. Ben-181 specifically induces interferon-γ (IFN-γ)-dependent IRG-47 expression, and IFN-γ correlates with cellular immune responses. We propose IRG-47 as a potential marker for Mmm antigen screening. Comparative genomic analysis between Ben-181 and the non-immunoprotective strain Ben-468 identified 35 proteins potentially linked to IRG-47 expression. Further screening revealed Mmm604, Mmm605, and Mmm606 as inducers of IRG-47 release. Intranasal immunization with these proteins in mice enhanced splenic lymphocyte proliferation, CD8 +T cell activation, a mixed Th1/Th2/Th17 response, and humoral antibody production. Mmm604 and Mmm606 also trigger mucosal antibody responses in mice. These proteins effectively stimulate cellular and humoral responses, making them promising candidates for Mmm subunit vaccine development. Our study highlights the potential of IRG-47 in Mmm antigen screening.