|Chase, Christopher -|
|Braun, L -|
|Harland, Richard -|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 25, 2009
Publication Date: January 25, 2009
Citation: Chase, C.C.L., Braun, L.J., Ridpath, J.F., Harland, R. 2009. Comparison of the Immune Response Between a Pair of NCP and CP Bovine Viral Diarrhea Virus (BVDV) Type 1 Isolates [abstract]. 4th U.S. BVDV Symposium. Poster No. 3. Technical Abstract: Aim: 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 this study we wanted to see the effect of an initial infection (or vaccination) with a type 1 NCP or CP BVDV pair followed by infection with a virulent type 2 BVDV on clinical signs and immune responses. 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 BVDV seronegative calves. The animals were first inoculated intranasally with either Tifton GA cytopathic (TGAC) or noncytopathic (TGAN) pair. A challenge of type 2 BVDV 1373 was administered to all of the animals on Day 91 of the study. Clinical assessments were 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 an uninoculated control. Three weeks later the calves were infected with virulent type 2 BVDV 1373 strain. Clinical assessments were performed daily and clinical samples 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 and 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) higher that the TGAC virus. In the second study, the calves inoculated with the TGAN virus developed antibody titers faster and to higher levels that 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. Conclusions: These studies indicate that non-cytopathic BVDV intranasal vaccination resulted in a faster immune response that is protective at an early age (within the first 2 weeks). However at the 90-day challenge, the only differences observed were more depressed platelet counts in the cytopathic BVDV vaccinated calves. This may indicate that NCP BVDV vaccines may result in faster protection for animals at higher risk for BVDV infection and that there might be some qualitative differences in immunity.