Novel vaccine protects mice against Staphylococcus aureus infection, say researchers

Researchers have developed an investigational vaccine that protected immunised mice from Staphylococcus aureus (S. aureus) infection.

The new vaccine called 4X-SA-GP, consisting of fungal β-glucan particles loaded with four S. aureus proteins, is designed to stimulate an anti-fungal immune response sufficient to protect the vaccinated organism against infection by the bacteria S. aureus.

S. aureus is one of the most common bacterial infections worldwide and antibiotic-resistant strains such as methicillin-resistant S. aureus(MRSA) are a major threat and burden to public health. MRSA not only infects immunocompromised patients but also healthy individuals and has rapidly spread from the healthcare setting to the outside community. While vaccines targeting the bacteria have been developed to combat the rapid spread of the disease, all have failed in clinical trials, the reasoning behind which remains unclear.

Immunocompromised individuals such as those with HIV are highly susceptible to S. aureus infections and also at increased risk of developing fungal infections. Based on this evidence, David Underhill of Cedars-Sinai Medical Center, US, and colleagues tested whether stimulation of antifungal immunity would promote the type of immune responses needed for effective host defense against S. aureus.

Mice were vaccinated once a week for three weeks with 4X-SA-GP and then injected with S. aureus either four or eight weeks later. Vaccination induced protective T cell and antibody responses. The T cell responses were essential for vaccine-induced protection from S. aureus infection. Moreover, the mice had detectable antibody levels and reduced S. aureus levels in the spleen and kidneys eight weeks after immunisation. According to the authors, this work potentially broadens the use of the β-glucan particle vaccine system for a much-needed vaccine targeting S. aureus.

The authors concluded: “We need some creative new approaches to explore towards developing a S. aureus vaccine and we are excited to share our recent experiences with antigen-loaded fungal particles.”

The study was published in PLOS Pathogens.