|Chase, Christopher C.|
Submitted to: American Association of Bovine Practitioners Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/25/2008
Publication Date: 9/25/2008
Citation: Chase, C.C., Braun, L.J., Ridpath, J.F., Harland, R. 2008. Comparison of the Immune Response Between a Pair of NCP and CP Bovine Viral Diarrhea Virus (BVDV) Type 1 Isolates [abstract]. American Association of Bovine Practitioners. Available: http://www.aabp.org/meeting/program2007.pdf. Interpretive Summary:
Technical Abstract: Bovine viral diarrhea virus (BVDV) is a major pathogen of cattle causing severe respiratory and reproductive disease. BVDV vaccines remain an important part of the control strategy. Previous work has described higher antibody responses in animals infected with a noncytopathic (NCP) BVDV when compared to its cytopathic (CP) BVDV pair. In those studies, animals were challenged 90 days later with either a NCP or a CP BVDV. The animals infected with NCP initially were protected to a higher degree against reinfection with either biotype when compared to the animals initially infected with CP virus. In this study we wanted to compare the level of protection generated following exposure to a type 1 NCP or a CP BVDV. The NCP and CP viruses used were isolated from the same mucosal disease case. Comparison was based on observation of clinical signs and immune responses. Materials and Methods: Two studies investigating the effect of BVDV biotype on the immune response and subsequent challenge with a virulent BVDV type 2 were performed. In Study 1, we used twenty 5-6 month old calves seronegative for BVDV type 1 and BVDV type 2. The animals were randomly sorted into two treatment groups. Group 1 was inoculated intranasally with the cytopathic BVDV TGAC type 1 strain as a primary challenge/inoculation and Group 2 received the non-cytopathic BVDV TGAN type 1 during the primary challenge. Clinical assessments were performed daily and clinical samples were collected. A challenge of type 2 BVDV 1373 was administered to all of the animals on Day 91 of the study. Again, clinical assessment was performed daily for fourteen days and samples were collected. Study 2 was performed using 7 unsuckled calves that were seronegative for BVDV type 1 and BVDV type 2. Three calves were infected with TGAC strain and three calves were infected with the TGAN strain and one calf was a non-inoculated control. Clinical assessments were performed daily and clinical samples were collected three weeks later the calves were infected with virulent type 2 BVDV 1373 strain. Clinical assessments were performed daily and clinical samples were collected Results: In Trial 1,the clinical scores were similar between the groups following the initial infection with either TGAC or TGAN with the exception of day 8 when there was a peak in the febrile response of the TGAN group. No remarkable clinical scores were noted following challenge with type 2 BVDV 1371. The white blood cell count (WBC) was similar between the two treatments following infection with 1373 BVDV. Platelets were more depressed following the initial infection or the challenge with 1373 in the TGAC group. Antibody response indicated that TGAN group developed antibodies faster (7 days sooner) and to higher levels (4-8X) than the TGAC virus. In the second study, calves inoculated with the TGAN virus developed antibody titers faster and to higher levels than TGAC. When challenged with 1373, the TGAN calves had 6 febrile days compared to 16 for the calves initially infected with TGAC. Also none of the febrile responses in the TGAN calves was greater than 104°F while there were 3 febrile responses greater than 104°F in TGAC calves. Significance: These studies indicate that non-cytopathic BVDV intranasal vaccination result in a faster immune response that is protective at an early age (within the first 2 weeks). However at later times there is no difference in protection. This may indicate that NCP BVDV vaccines may result in faster protection for animals at higher risk for BVDV infection.