Imagine an ordinary chicken egg containing a biological weapon capable of protecting human immune cells from the attack of one of the world's most stubborn bacterial toxins. That is the essence of a surprising finding from research led by Prof. drg. Heni Susilowati, M.Kes., Ph.D., PBO., Professor in the Department of Oral Biology, Faculty of Dentistry, Universitas Gadjah Mada—a study that opens a new path in the fight against Pseudomonas aeruginosa, an opportunistic bacterium that has long been a nightmare for the medical world.
The Blue Toxin That Kills Immune Cells
Pseudomonas aeruginosa is no ordinary bacterium. It lives almost everywhere, from soil to hospital surfaces, and is known as one of the leading causes of nosocomial infections— infections acquired by patients while receiving care in healthcare facilities. In patients with cystic fibrosis, infection with this bacterium can be fatal because of its resistance to multiple types of antibiotics.
What makes this bacterium particularly dangerous is not only its resistance to drugs, but also its chemical weapon: pyocyanin (PCN). This blue-green pigment is a secondary metabolite released by P. aeruginosa early in the course of infection. PCN is known to suppress the function of B cells, T cells, and macrophages—three crucial components of the body's immune system. Moreover, PCN induces cell death through the activation of caspase 3, an enzyme that functions like a “self-destruct button” within the cell.
Previous research by the same group had demonstrated that PCN kills human B cells (Raji cells) through this caspase 3 pathway. The question that remained was: is there a way to stop this cell-death process?
From the Chicken Coop to the Laboratory
The answer came from an unexpected source—from the yolks of Leghorn chicken eggs.
The research team, consisting of Prof. drg. Heni Susilowati, M.Kes., Ph.D., PBO., together with Sidna Artanto, Heribertus Dedy Kusuma Yulianto, Wihaskoro Sosroseno, and Suryani Hutomo, designed a carefully controlled immunization protocol. Five three-month-old Leghorn chickens were injected with PCN mixed with complete Freund's adjuvant and then given two booster injections at two-week intervals. One week after the final immunization, the eggs were collected and IgY—an immunoglobulin stored in chicken egg yolks and equivalent to IgG in mammals—was extracted using a specialized purification kit.
The result? Egg yolks from the immunized chickens contained highly specific IgY against PCN. An agarose gel precipitation test (AGPT) showed clear precipitate lines, while ELISA confirmed a significant concentration of specific IgY—the first batch reaching 8.95 μg/μl.
“Antigen-specific IgY antibodies were able to inhibit PCN-induced Raji cell death, suggesting that PCN-specific IgY antibodies may be protective against PCN-induced Raji cell death.” — Prof. drg. Heni Susilowati, M.Kes., Ph.D., PBO., in a 2019 F1000Research research report
Cells That Survived, Hope That Grew
The testing was conducted using Raji cells—a human B-cell line cultured in the laboratory. These cells were exposed to various concentrations of PCN, and the results were consistent: the higher the PCN dose, the more cells died. When anti-PCN-specific IgY was added to the mixture, the picture changed dramatically.
At an IgY concentration of 28.19 μg/mL or higher, the ability of PCN to kill Raji cells was significantly inhibited (p<0.05). This protective effect was dose-dependent—the higher the IgY dose, the greater the protection. Microscopic observations using acridine orange/ethidium bromide staining further supported these findings visually: cells exposed to the PCN-IgY mixture appeared bright green (living), in substantially greater numbers than cells exposed only to PCN, which appeared orange-red (dead).
The exact mechanism has not yet been fully elucidated. The research team hypothesized that the PCN-IgY complex fails to activate caspase 3 inside Raji cells, thereby interrupting the cell-death pathway. However, this hypothesis still requires further validation.
More Than Just a Laboratory Finding
Funded by a grant from the Ministry of Research, Technology, and Higher Education of the Republic of Indonesia, this research is not merely about cells in a Petri dish. It addresses a much broader challenge: how can we confront bacteria that have become resistant to antibiotics?
P. aeruginosa has also been found in dental pulp and periapical lesions, and its presence has been associated with endodontic treatment failure. This means that the bacterium is not unfamiliar in the field of dentistry. IgY-based immunotherapy—which has previously been shown to prevent P. aeruginosa colonization in patients with cystic fibrosis through oral administration—now has an additional layer of evidence: it may also protect immune cells from toxins released by the bacterium itself.
If these findings can eventually be translated into an effective therapy, then that seemingly ordinary chicken egg may contain more answers than we have ever imagined.
Source DOI: https://doi.org/10.12688/f1000research.19327.1
Authors: Anny Anggraini; drg. Achmad Zam Zam Aghasy, M.Kes.
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