A breakthrough in the search for a vaccine against pneumonia in foals

"After decades of effort, our research, funded by the Morris Animal Foundation, has resulted in the first effective vaccine to protect foals from R. equi infection, considered the most common form of pneumonia in older chickens. of a few weeks at the age, "said Dr. Noah Cohen, one of the leading authors of the PLOS pathogens document describing the immunization track, and the Patsy Link Chair in Equine Research at Texas A & M University. Researchers from Harvard Medical School were also part of the research team.

In addition to causing severe, insidiously progressive pneumonia, infection with Rhodococcus equi can affect other organs of the body, such as bones (including the spine), abdominal lymph nodes, eyes, the joints and the brain. Mortality rates vary from 20% to 40% of infected foals. There is currently no licensed vaccine against pneumonia in foals, which creates a critical need to develop an effective vaccine.

For the vaccine trial, Dr. Cohen's team first studied whether vaccination of pregnant mares three weeks and six weeks before the birth of their foals protected their newborns from pneumonia in foals. The team discovered that antibodies against pneumonia were transferred to foals via mares' colostrum, an essential element in establishing that horses were unable to transfer antibodies across the placenta. More importantly, these antibodies were able to protect almost all foals born to mares vaccinated against pneumonia.

Then, the team conducted a small, randomized, controlled study of nine foals with R. equi. Five foals received serum with high levels of antibodies against R. equi and four others. The five foals receiving the hyperimmune serum were protected against R. equi pneumonia, while foals receiving the standard plasma all developed pneumonia. Other safety tests are underway, but these early results seem to support the safe and effective use of this new vaccine strategy against pneumonia. In addition, this suggests that immunization of donor horses with this vaccine could be used to produce plasma with which foals could be transfused to prevent R. equi pneumonia.

Pneumonia caused by R. equi, which is often grouped by farms, occurs on every continent, except Antarctica. Some farms have recurring problems and sporadic other farms or none at all. Despite effective antibiotic treatments, the incidence of this disease remains high and many affected foals die. On farms that have problems with this disease, an average of 15% to 20% of foals develop pneumonia in a given year.

In addition to protecting the foals against R. equi-induced pneumonia, Dr. Cohen said the new vaccine could protect against other diseases, including sepsis, the leading cause of death in foals over the course of a year. first weeks of life. Other potential targets of the disease for the vaccine include bacterial infections such as the equi subspecies of Streptococcus equi, at the root of the ancient and widespread disease known as strangles.

"The development of a vaccine to protect foals against pneumonia has long been a priority for the Morris Animal Foundation and the equine researchers we support," said Dr. Kelly Diehl, Acting Vice President of Scientific Programs from the Morris Animal Foundation. "We have invested more than $ 2 million to help fight this disease." The results of Dr. Cohen's team are groundbreaking and could change the way we manage this disease and save the lives of young horses around the world. whole. "

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More information:
Colette Cywes-Bentley et al., Poly-N-Acetylglucosamine Antibody, Protect Against Intracellular Pathogens: Mechanism of Action and Validation in Horse Foals Exposed to Rhodococcus equi PLOS pathogens (2018). DOI: 10.1371 / journal.ppat.1007160