BREAKTHROUGH! Mice Study Shows That Prophylactic Intranasal Administration Of SARS-CoV-2 Specific Immunoglobulin Y Protects Against COVID-19!
A new study involving mice showed that prophylactic intranasal administration of SARS-CoV-2 specific immunoglobulin Y generated in chicken eggs displays protective effects in the infected animal models.
The breakthrough study was conducted by researchers from King Abdulaziz University-Saudi Arabia, University of Iowa-United States of America and the University College London Hospitals-United Kingdom.
According to the study team, safe, passive immunization methods are required against the SARS-CoV-2 and its variants. Immunization of chickens with antigen is known to induce specific IgY antibodies concentrated in the egg yolk and has a good safety profile, high yield of IgY per egg, can be topically applied, not requiring parenteral delivery.
The study findings provided the first evidence of the prophylactic efficacy of Immunoglobulin Y antibodies against SARS-CoV-2 in mice.
For the study, Lohmann hens were injected with recombinant SARS-CoV-2 RBD protein.
Subsequently, IgY-Abs were extracted from the eggs and characterized using SDS-PAGE. Antiviral activity was evaluated using plaque reduction neutralization tests.
In additional experiments, IgY-RBD efficacy was examined in mice sensitized to SARS-CoV-2 infection by transduction with Ad5-hACE2 (mild disease) or by using mouse-adapted virus (severe disease).
The study findings showed that in both cases, prophylactic intranasal administration of IgY-Abs reduced SARS-CoV-2 replication, and reduced morbidity, inflammatory cell infiltration, hemorrhage, and edema in the lungs and increased survival compared to control groups that received non-specific IgY-Abs.
The study team said that the study findings indicate that further evaluation of IgY-RBD antibodies in humans is warranted.
Corresponding author, Dr Esam I. Azhar from the Special Infectious Agents Unit-BSL3 at King Abdulaziz University told Thailand Medical News
, “Our study findings shows the generation, characterization and antiviral activity of egg yolk derived IgY-Abs against the SARS-CoV-2 Receptor Binding Domain. Utilizing two different models of murine SARS-CoV-2 infection, the study showed that intranasal prophylactic administration of IgY-Abs reduced viral replication, and reduced inflammatory cell infiltration, hemorrhage, and edema in the lungs.”
The study findings were published in the peer reviewed journal: PLOS Pathogens. https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1010782
The study is the first to characterize and test the antibody activity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific immunoglobulin Y (IgY) derived from the eggs laid by chickens immunized with recombinant SARS-CoV-2 receptor binding domain (RBD) protein.
Typically, passive immunization, where an individual receives antibodies against specific antigens instead of their immune system generating antibodies against the pathogen, is an effective method to immunize immunocompromised individuals and to provide temporary immunity while robust vaccinations are being developed.<
Importantly, immunoglobulin Y (IgY) antibodies are considered a safe alternative as they do not bind to Fc receptors on immune cells or cause adverse reactions.
It has been known that the egg yolk of oviparous animals is rich in IgY, and specific IgYs can be generated and accumulated in the egg yolks by inoculating chickens with disease-specific antigens.
Past studies have shown that such IgYs are safe therapeutic agents, and the United States Food and Drug Administration has considered IgYs safe for consumption.
Already infections such as pulmonary Pseudomonas aeruginosa have been treated with oral IgY for years with no detrimental effects.
Furthermore, egg yolk-derived IgYs can provide a safe and cost-effective method to confer transient immunity against SARS-CoV-2 and all its variants and could be an efficient tool during recurrent surges of COVID-19.
The study team immunized 25 weeks old Lohmann hens with 200 µg of SARS-CoV-2 RBD protein emulsified with equal quantities of an adjuvant, followed by similar booster shots. The control group consisting of the same type of hens was immunized with only the adjuvant. The eggs were collected 1 week before immunization and until 12 weeks after immunization.
For the study, the polyethylene glycol 8000 precipitation method was used to isolate IgY from egg yolks each week. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was employed to ascertain the purity and molecular weight of extracted IgY. Additionally, a Western blot assay was performed to determine the specificity of the IgY antibody to the SARS-CoV-2 RBD protein.
The detailed neutralization activity of anti-SARS-CoV-2 RBD IgYs was tested on live viruses in a biosafety level 3 facility using plaque reduction neutralization assays.
Subsequently, the prophylactic efficacy of these antibodies was investigated in mice models. Since mice are resistant to SARS-CoV-2, they were infected with mice-adapted SARS2-N501YMA30 or made susceptible to SARS-CoV-2 by the exogenic insertion of human angiotensin-converting enzyme 2 (hACE2) receptors using replication-deficient adenovirus (Ad5).
All viral titers were determined utilizing SARS-CoV-2 plaque assay and histopathology of lungs harvested from mice sacrificed at specific time points post-infection.
The study findings showed that hens inoculated with SARS-CoV-2 RBD protein generated high titers of anti-SARS-CoV-2 RBD IgYs three weeks after immunization, which were maintained at the same level for up to 12 weeks.
Also, the Western blot assay utilizing these IgYs revealed immune activity against the SARS-CoV-2 RBD protein.
Importantly, the plaque reduction neutralization assay with live viruses confirmed that anti-SARS-CoV-2 RBD IgYs were able to inhibit viral replication.
During the study, the mice models infected with SARS2-N501YMA30 or Ad5-hACE2-assisted SARS-CoV-2 displayed signs of infection such as weight loss, alveolar edema, and high viral replication titers in the lungs.
However, the intranasal administration of prophylactic anti-SARS-CoV-2 RBD IgYs resulted in a marked reduction of symptoms and viral load, with nearly complete survival and recovery of body weight.
Just as important, a significant reduction in lung tissue inflammation was also noticed during the histopathology assessments.
The study team believes that intranasally administered IgYs may express anti-viral activity by either binding to the SARS-CoV-2 spike protein and preventing it from binding to the ACE2 receptors or causing mucosal surface agglutination of SARS-CoV-2 and obstructing its entry into the mucosal membrane.
It was also noted that the administration of SARS-CoV-2 RBD-specific IgYs was significantly more effective in increasing survival and reducing morbidity and inflammation compared to the non-specific IgYs generated in the control group.
In conclusion, the research team said that the study presents a safe, relatively fast, and cost-effective method to produce disease-specific IgYs in the egg yolks of immunized chickens. Passive immunoprophylaxis of mice models with these IgYs was shown to be effective in reducing disease morbidity and increasing survival.
Importantly, with the ever-emerging SARS-CoV-2 variants exhibiting immune evasion against vaccine- and infection-induced antibodies, the production of SARS-CoV-2-specific IgYs in egg yolks could provide a fast and effective stop-gap method to contain the severe symptoms of the disease until improved vaccines and monoclonal antibodies are generated.
The study team stressed that the high cost and shortage of resources for manufacturing vaccines still leave a large part of the global population, especially in low-income countries, vulnerable to severe COVID-19 symptoms. In contrast, the relatively low generation time and cost-effective methods of producing SARS-CoV-2 specific IgYs could help protect a larger portion of the world population until viable vaccination options are developed.
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