Sheep with a green glow, indicating vaccination.

Brucellosis Breakthrough: Tagging Vaccines for Safer Sheep

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Beau Callahan in Health & Wellness December 2025 • 4 min read.

"Scientists are one step closer to eradicating brucellosis with a novel vaccine tagging method, ensuring healthier livestock and safer dairy for everyone."


Brucellosis is a global disease that hits both the economy and public health hard. It's a zoonosis, meaning it spreads from animals to humans, and it's a major concern wherever sheep and goats are raised. The disease leads to abortions in animals and reproductive issues, and that's just the start of the economic and health problems it brings.

For years, vaccination has been a key strategy in controlling brucellosis in sheep and goats. The B. melitensis Rev1 vaccine is widely used, but it comes with a significant drawback. It triggers a long-lasting antibody response, making it tough to distinguish vaccinated animals from those that are actually infected. This poses a challenge for disease surveillance and eradication programs.

Now, researchers are excited about a potential solution: a genetically modified version of the Rev1 vaccine tagged with green fluorescent protein (GFP). This innovative approach allows for easy identification of vaccinated animals, paving the way for more effective brucellosis control and eradication.

How Does GFP Tagging Work?

Sheep with a green glow, indicating vaccination.

The researchers created a special strain of the Rev1 vaccine, called Rev1::gfp, by inserting a mini-Tn7-gfp into the glmS-recG region of the bacterial chromosome. This insertion ensures that the GFP is produced continuously, acting like a fluorescent tag on the vaccine strain. This doesn't mess with the normal operations of the vaccine, but it makes it super easy to spot.

To identify vaccinated animals, the team also developed an indirect ELISA-GFP test. This test detects antibodies against GFP in vaccinated animals. When sheep are vaccinated with the tagged vaccine, their immune systems produce antibodies against both Brucella and the GFP tag. If a blood sample tests positive for anti-GFP antibodies, it indicates that the animal has been vaccinated.

  • Visual Identification: The Rev1::gfp strain can be directly visualized under ultraviolet illumination or fluorescence microscopy.
  • PCR-GFP multiplex: A multiplex PCR test can identify the presence of the gfp gene in the vaccine strain.
  • ELISA-GFP test: This serological assay detects anti-GFP antibodies in vaccinated animals.
The Rev1::gfp strain maintained the same biological properties as the original Rev1 strain, including its effectiveness and safety. When tested in mice, it provided similar protection against Brucella infection. The real advantage is that the GFP tag allowed researchers to easily differentiate vaccinated animals from those infected with the bacteria. After vaccinating lambs, the scientists found that the Rev1::gfp vaccine didn't cause them to produce anti-GFP antibodies on their own. However, when they combined the vaccine with recombinant GFP, the lambs developed a strong and lasting anti-GFP antibody response. This response could be easily detected with the ELISA-GFP test.

Why This Matters

The ability to easily differentiate vaccinated from infected animals is a game-changer for brucellosis control programs. It enables more targeted surveillance, reduces unnecessary culling of livestock, and supports brucellosis eradication efforts. By tagging the Rev1 vaccine with GFP, scientists have created a valuable tool for improving livestock health and safeguarding public health.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

1

What is brucellosis and why is it a concern?

Brucellosis is a zoonotic disease, meaning it can spread from animals to humans. It primarily affects sheep and goats, causing abortions and reproductive issues in animals. This leads to significant economic losses for farmers and poses a public health risk. The disease is a major concern in regions where these animals are raised, impacting both livestock health and the safety of dairy products. Vaccination is a key strategy to combat this.

2

What is the *B. melitensis Rev1* vaccine, and what are its limitations?

The *B. melitensis Rev1* vaccine is a widely used tool for controlling brucellosis in sheep and goats. However, a major drawback is that it triggers a long-lasting antibody response, making it difficult to differentiate vaccinated animals from those actually infected with brucellosis. This limitation complicates disease surveillance and eradication efforts.

3

How does GFP tagging of a vaccine work?

GFP tagging involves genetically modifying the *Rev1* vaccine to include a green fluorescent protein (GFP) marker. This modified vaccine, called *Rev1::gfp*, allows researchers to easily identify vaccinated animals because the GFP acts like a fluorescent tag. The presence of GFP can be detected using methods like fluorescence microscopy or specific antibody tests, enabling clear differentiation between vaccinated and infected animals.

4

What is the *ELISA-GFP* test, and how does it help in identifying vaccinated animals?

The *ELISA-GFP* test is designed to detect antibodies against GFP in vaccinated animals. When sheep are vaccinated with the *Rev1::gfp* vaccine, their immune systems produce antibodies against both Brucella and the GFP tag. A positive result for anti-GFP antibodies indicates that the animal has been vaccinated, providing a reliable way to distinguish vaccinated animals from those that may be infected.

5

Why is GFP tagging of the *Rev1* vaccine considered important for brucellosis control?

Tagging the *Rev1* vaccine with GFP is crucial for brucellosis control because it enables more effective surveillance and targeted interventions. By easily differentiating vaccinated from infected animals, resources can be focused on managing actual infections, reducing unnecessary culling of livestock, and improving the overall effectiveness of eradication programs. This approach enhances livestock health and safeguards public health by reducing the spread of brucellosis.

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