|Bauermann, Fernando - South Dakota State University|
Submitted to: Archives of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2017
Publication Date: 8/9/2017
Publication URL: http://handle.nal.usda.gov/10113/5801880
Citation: Falkenberg, S.M., Bauermann, F.V., Ridpath, J.F. 2017. Characterization of thymus-associated lymphoid depletion in bovine calves acutely or persistently infected with bovine viral diarrhea virus 1, bovine viral diarrhea 2 or HoBi-like pestivirus. Archives of Virology. 1-8. doi. 10.1007/s00705-017-3523-x.
Interpretive Summary: Bovine viral diarrhea viruses (BVDV) belong to two different species (BVDV-1 and BVDV-2). In addition, several unassigned atypical pestiviruses have been characterized and proposed as putative species, such as HoBi-like virus. Clinical signs resulting from HoBi-like virus infection of cattle are indistinguishable from those that result from infection with either BVDV-1 or BVDV-2. These pestiviruses can cause both acute and persistent infections, but the immune responses associated with each of these infections differ. While persistent infections appear to be a complex interaction between immune tolerance and the viral swarm, the immune response to acute infection is relatively simple and variations in clinical response are more likely due to variations in the strain and type of the infecting virus. Data from this study demonstrates that while minor differences were observed between groups acutely infected with the different pestivirus strains, the degree of thymic depletion observed in acute infections in this study is dependent on viral strain. In contrast, the degree of thymic depletion in persistently infected (PI) calves was related to the survival of the PI calf rather than the viral isolate. These results would suggest that the degree of thymic depletion is linked to survivability and immune tolerance of the persisting virus.
Technical Abstract: Viruses from recognized pestivirus species bovine viral diarrhea 1 (BVDV-1) and BVDV-2 and the proposed pestivirus species HoBi-like virus infect primarily cattle. Exposure of cattle to these viruses can lead to either acute or persistent infections depending on the timing and status of the animal exposed. Naïve pregnant cattle exposed during the first trimester of gestation can give birth to persistently infected (PI) calves. Clinical presentation and survivability, in PI cattle, is highly variable even with the same pestivirus strain whereas the clinical presentation in acute infections is more uniform with severity of symptoms being primarily a function of virulence of the infecting virus. The aim of this study was to compare thymic depletion in acute and persistent infections of the same pestivirus isolate. The same general trends were observed with each pestivirus isolate. Thymic depletion was observed in both acutely and persistently infected calves. The average thymic depletion observed in acutely infected calves was greater than that in age matched PI calves. PI calves, regardless of infecting virus, revealed a greater variability in response compared to acutely infected calves. A trend was observed between survivability and depletion of the thymus, with PI calves surviving less than 5 weeks having lower cortex: medulla ratios and greater depletion. These are the first observations to compare PI and acutely infected calves with the same isolates as well as evaluate PI calves based on survivability. Further, these studies identify a quantifiable phenotype associated with potential survivability.