Quantum leaps in calf immunology

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You might as well throw away your veterinary school immunology book, someone told me recently. I was horrified. 

However, that individual was somewhat right. The new discoveries in the field of immunology are astounding. My old immunology book might someday read like a geography book from when the world was still thought to be flat.

Calf immunology advances

There are some paradigms regarding calf immunology that are quite simply wrong. Until recently, vaccination programs I recommended followed some of these notions. 

  • The calf has an immature immune system; therefore, avoid early vaccinations. 
  • Do not vaccinate a calf in the face of maternal antibodies.  
  • If the calf does not respond with a measurable titer on a blood sample, then the vaccination was ineffective.

A summation of literature presented by University of Georgia veterinarian Amelia Woolums at the 2007 American Association of Bovine Practitioners meeting altered these recommendations. 

First, calves with a failure of passive transfer were confirmed to benefit from early vaccination. This suggests that calves’ immune system is not necessarily immature or unable to respond to vaccine or other stimulation. 

Next, calves vaccinated in the face of maternal antibodies have varied outcomes. While antibody titers generally do not increase, one branch of the immune system — the cell-mediated line of immune “infantry” — does send in T-cell “troops.” 

A number of trials have demonstrated that the immune system does indeed respond, but researchers were not trained to look for a different type of response than what they had always been looking for. 

New opportunities

Science has also uncovered some interesting things about vaccine delivery.

Traditionally, we have relied on systemic vaccination. We give a vaccine in the muscle and components of the vaccine travel throughout the body and present themselves to various sites in the body to stimulate the immune system. 

Another effective way to administer vaccine is to expose it to mucosal surfaces for absorption. While skin is the largest organ, the mucosa is enormous! Mucosa covers the inside lining of many organs, including the nasal cavity, gut and upper respiratory tract. Taking this information a step further, science has told us that nearly 90 percent of infectious bovine pathogens enter and begin the infection process at the mucosal surface. The alter ego of the cell-mediated “infantry” — the humoral “infantry” and its antibody “troops” — is on the mucosal surface to respond to the invaders. 

And, there are many antibody types besides just IgG, which was often the only response measured to vaccine response. IgA is a surface antibody that plays an important role in surface response and is produced at a much greater rate than IgG, IgM, IgE and others.  

By stimulating the immune system through intranasal presentation, we have an effective way to stimulate the mucoid tissue. While intranasal vaccine is not new technology, we have definitely underestimated the ability of the body to respond to a variety of pathogens when stimulated via this route.

Bringing it all together

If we pull all of this immunology information together, we arrive at vaccines that are safe and efficacious for use in calves at or near birth, in the face of maternal antibodies, and given intranasal to stimulate the largest battlefield in the body — the mucosa. This route eliminates the use of a needle, avoids potential beef-quality issues and is non-invasive. 

So, hang onto your hats, advances in calf immunology are coming in quantum leaps. Ask your veterinarian for more information on this new vaccine technology.

Angela M. Daniels is a veterinarian with Circle H Headquarters, a dairy and swine veterinary practice, food safety laboratory and DHIA milk-testing and contract research organization in  Dalhart, Texas.



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