Characterization of the cellular and humoral immune responses to persistent colonization of Brucella abortus strain RB51 in a Jersey cow

Authors: Boggiatto, Paola; GREIMAN, HALEY - Iowa State University; FALKENBERG, SHOLLIE - Auburn University; Sarlo Davila, Kaitlyn; Putz, Ellie; Olsen, Steven

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Brucella abortus strain RB51 (RB51) is the commercial cattle vaccine against bovine brucellosis used in the United States and many parts of the world. It was licensed in 1996 and has been shown to be safe and efficacious in providing protection against disease in cattle. However, in 2017, the Centers for Disease Control and Prevention (CDC) identified human cases of brucellosis caused by infection with RB51, and traced them back to the consumption of unpasteurized products. These products were traced back to several dairies, which identified healthy cows that were shedding RB51 in their milk. The National Animal Disease Center (NADC) obtained one of these animals with the aim of understanding the mechanisms of action resulting in this animal shedding RB51 in its milk. To do so, we performed various analysis to examine the animal's immune response at arrival and following revaccination with RB51. Understanding why some animals do not clear the vaccine strain and furthermore, shed it in their milk will help develop improvements on the current vaccine and/or prevent the vaccination of susceptible animals. The data presented here is of interest to brucellosis researchers, veterinarians and public health officials, as RB51 is important for the control of bovine brucellosis but also poses a significant public health impact.

Technical Abstract: Brucella abortus strain RB51 is the commercial cattle vaccine used in the United States and many parts of the world against bovine brucellosis. RB51 was licensed for use in 1996, and it has been shown to be safe and efficacious in cattle, eliciting humoral and cellular responses in calves and adult animals. In 2017, an epidemiological trace back investigation performed by the Centers for Disease Control and Prevention (CDC) identified human cases of brucellosis caused by infection with RB51. These infections resulted from the consumption of unpasteurized dairy products, which were traced back to otherwise healthy animals that were shedding RB51 in their milk. We obtained an animal identified as an RB51 shedder and have been housing it on the National Animal Disease Center (NADC) campus. Improved understanding of the host cellular and humoral immune response to RB51 in persistently colonized cattle may be achieved by characterization of these shedding animals. We demonstrate that in the presence of persistent RB51, there is a lack of peripheral anti-RB51 CD4+ T cell response with a concurrent high anti-RB51 IgG humoral response. By analyzing these responses and understanding the mechanisms that result in RB51 persistence, we aim to develop intervention strategies to improve on the current vaccine and/or prevent vaccination of susceptible animals, which poses a risk to human health.