Changes in peripheral blood leucocyte counts and subpopulations after experimental infection with BVDV and/or Mannheimia haemolytica
ABSTRACT Leucocyte counts and subpopulations were studied in peripheral blood from calves experimentally infected in the respiratory tract with either bovine virus diarrhoea virus (BVDV) or Mannheimia haemolytica (Mh), or with a combination of both agents (BVDV/Mh). A non-inoculated control group was included. Peripheral blood samples were obtained for total leucocyte counts, and for neutrophil, lymphocyte and monocyte counts. The numbers of blood lymphocytes expressing the surface antigens CD4, CD8, WC1, B and IL-2R were analysed using flow cytometry. The results showed that BVDV inoculation induced a significant decrease in total leucocyte counts and in neutrophil and lymphocyte numbers, while Mh inoculation induced significant increases in total leucocyte counts and neutrophils, while the lymphocyte count decreased. In the BVDV/Mh group, the total leucocyte count and the lymphocyte numbers decreased significantly. In this group, the lymphocyte numbers remained on a very low level throughout the rest of the study. The numbers of CD4+, CD8+ and WC1+ lymphocytes decreased significantly compared with before inoculations mainly in the BVDV and BVDV/Mh groups. The drops were most pronounced in the BVDV/Mh group. The numbers of B+ lymphocytes and IL-2R+ cells did not change significantly.
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- "M. haemolytica is an opportunestic pathogen that inhabits the nasopharynx and tonsils of cattle and sheep (Radostits et al., 2006) and is capable of causing infection when the body's defense mechanisms are impaired (Haig, 2011). Environmental stress factors like inclement weather, shipment, weaning, overcrowding and complex interactions among several infectious agents can serve as cofactors for pathogenesis of pneumonic pasteurellosis (Kraabel and Miller, 1997; Ganheim et al., 2005). A major problem in the control of pneumonic pasteurellosis is the lack of vaccine which consistently induces protective immunity against M. haemolytica (Dyer, 1982). "
ABSTRACT: This experimental study was done on a total of 40 male lambs with the objectives of developing experimental vaccines from Mannheimia haemolytica serotypes A2 and A7 that express iron regulated outer membrane protein and in vivo evaluation of their efficacy. Lambs were categorized in to four experimental groups and vaccinated with 1 ml of vaccine containing 5 × 108 CFU/ml. Group 1 was vaccinated with M. haemolytica A2, group 2 with A7, group 3 with serotype A2 and A7 combination, and group 4 received saline as control. They were challenged intratracheally by the respective homologous serotype after 35 days of vaccination. Post challenge clinical investigation showed that significant higher rate of morbidity was seen in control group which was demonstrated by raised rectal temperature (by 0.5-1°C) and respiratory signs. From the total of 26 lambs challenged with live M. haemolytica A2 and A7, 6 (23.1%) and 4 (15.3%) lambs were found dead and sick, respectively. Higher mortality and morbidity were observed in unvaccinated control group; however, lesser was recorded in combined vaccinated group. Lung lesions of variable severity were observed in 13 (50.0%) lambs following challenge. From vaccinated groups, 5 (27.8%) lambs were found to have a +1 lung lesion score. All of the lambs in unvaccinated control group had scores between +2 and +3. There was a statistically significant difference (p < 0.05) between control and vaccinated groups, while no statistically significant difference (p > 0.05) was seen among vaccinated groups concerning lung lesion scores. Furthermore, the respective serotypes of M. haemolytica were successfully re-isolated from pneumonic lungs at a mean titre range of 102.2 – 108.1 CFU/g. In conclusion, lambs which received combined vaccine confer relatively good protective efficacy than M. haemolytica A2 or A7 vaccinated groups. Therefore, further study should be done on evaluation of antibody titer at different time points.African journal of microbiology research 03/2014; 8(11):1237-1244. DOI:10.5897/AJMR2013.6371 · 0.54 Impact Factor
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ABSTRACT: Bovine viral diarrhea virus (BVDV) infection altered leukocyte populations in calves that were reflected by depression of T, BoCD4+, and BoCD8+ lymphocytes in the thymus and depression of B lymphocytes in Peyer's patches (PP). The present study was based on mononuclear leukocyte preparations from eighteen 9- to 12-month-old crossbred calves that were each exposed to either bovine respiratory syncytial virus (BRSV), BVDV, or BRSV and BVDV concurrently, or served as mock-infected controls. Peripheral blood leukocytes were collected on postinfection days (PID) 0, 2, 4, 6, and 8, and cell populations from thymus, spleen, mesenteric lymph node, and PP were collected at necropsy on PID 9. The leukocytes were analyzed using flow cytometry for lymphocyte subpopulations expressing antigens specific for BoCD2, BoCD4, BoCD8, BoWC1, lambda light chain of bovine immunoglobulin, BoCD11b and major histocompatibility complex (MHC) class II. Concurrent BRSV and BVDV infections caused exaggerated alterations in leukocyte populations with a greater percentage of T-lymphocytes harvested from the PP. Alterations in the leukocyte populations in lymphatic tissues and in peripheral circulation due to BVDV infection may be an important mechanism for causation of clinically severe diseases of the respiratory and digestive tracts during concurrent BRSV and BVDV infections.Viral Immunology 02/1999; 12(4):323-34. DOI:10.1089/vim.1999.12.323 · 1.64 Impact Factor