March 29, 2023 – Infection with the fungus Candida auris can be problematic for some and deadly for others, especially for people at higher risk due to advanced age or because they have a weakened immune system, called immunosuppression. A vaccine in development could offer hope.
The major problem is not necessarily the fungus itself but a lack of treatment options. C. auris is resistant to two of the three major categories of antifungal therapies, and in some cases all three.
“It's the only true multidrug-resistant fungus that we have,” said Ashraf Ibrahim, PhD, an investigator at The Lundquist Institute in Torrance, CA. He is also senior author of a new study evaluating how well the monoclonal antibody vaccine from Vitalex Biosciences could work to prevent or treat these infections.
Although relatively rare, C. auris infections can lead to death for between 30% to 70% of those at higher risk, said Ibrahim, who is a founder of Vitalex and an infectious disease doctor at Harbor-UCLA Medical Center.
“So you don’t need a scientist to explain how dangerous this thing is.”
The CDC describes C. auris as an “urgent threat to public health.” C. auris infection primarily spreads in health care settings. The fungus is not airborne – so you don’t get it from someone sneezing or coughing. But it can survive on surfaces and on human skin.
If the vaccine continues to show promise, it could someday be used to boost the immune protection of older people going into a nursing home, people treated with multiple antibiotics in a hospital, and those likely to need ICU care after a medical procedure.
Most Safe, for Now
Public health officials want to boost surveillance for C. auris infections, Ibrahim said. Right now, people with healthy immune systems are not at higher risk unless they become vulnerable at some point. “If you do have any sort of immunosuppression, it really takes advantage of that and starts growing a lot -- and then starts invading.”
The vaccine was able to kill C. auris fungi when combined in lab experiments. The vaccine also reduced the production of a “biofilm” by 30% to 40%. A fungal biofilm is a barrier that can prevent antifungal treatments from entering an infected cell or organ.
In experiments with mice with C. auris infection, for example, the vaccine reduced fungi by 10 times in the kidneys and heart. This means there could be some protection against systemic bloodstream infections with C. auris, the researchers said.
Not the Only Fungus in the Family
You might assume the monoclonal antibody vaccine is being developed directly against C. auris. However, that’s not the case. Scientists are designing the vaccine using Candida albicans, a more common fungus and the one responsible for a majority of yeast infections in healthy women.
So why C. albicans? “We're actually working on both right now, but we're trying to get this vaccine to patients as soon as possible,” said Ibrahim.
C. auris infections were only identified relatively recently compared to C. albicans, which has been known for decades. Vitalex already had a program in progress to develop a dual antigen vaccine against C. albicans. When they compared the two fungi, they found they share specific cell surface proteins that can be targeted to prevent either fungus from attaching to and invading cells in the body.
“We said, ‘Well we have the dual antigen vaccine in hand. Why don’t we just try it in Candida auris and see if it protects?’” Ibrahim said. “And it's clear that the vaccine actually works very well with Candida auris.”
A Possible Role in Treatment
The vaccine holds potential to not only prevent infection, but as a treatment used in combination with other antifungals in someone already infected with C. auris. In research on an earlier version of the vaccine, if the mice were vaccinated and also treated with an antifungal, there was a united, beneficial effect, Ibrahim said.
“So pretty much like the COVID-19 story,” Ibrahim said. “If the vaccine doesn't prevent the disease, then adding a treatment option can actually protect the person from dying.”
Up next is a toxicity study in rabbits to evaluate the safety of the vaccine. After that, clinical trials in humans could follow.
Still Early Days
“Candida auris is a significant concern for a very specific population,” said Aaron Glatt, MD, chief of infectious diseases at Mount Sinai South Nassau in New York, when asked to comment. “For the vast majority of the population right now, that's not a concern. But as public health officials and as infectious disease people, we have to very concerned about everybody,”
“Certainly, the potential for this to become more widespread would put more people at potential risk,” added Glatt.
Glatt advised caution in interpreting preliminary results like these. “It's a very serious public health concern … but it's not something that everybody in the United States needs to think about every moment right now.”