Progress 10/01/00 to 09/30/04
Outputs
Evaluation of the Y system genes within a moderately susceptible B system background: We want to further investigate the influence of the Y system on MD resistance by concentrating on the Y alleles degree of influence in a more moderate B system background than B11. This research is ongoing under another grant. Evaluation of the influence of non-Major Histocompatibility Complex genes on Marek's Diseases resistance: We completed 7 challenge trials. Data were analyzed using the chi-square test to examine the homogeneity of disease incidence among haplotypes within each of the non-MHC systems. Overall, the C, D, H and I systems did not show any significant positive or negative effect on development of MD. Statistically significant differences were observed only within the P system. Birds having a B19B19P1P1 haplotype had a significantly lower incidence of MD (21%) when compared with birds bearing the B19B19P4P4 haplotype (73%, P<0.001). In chicks with the B19B21
background, there was a significantly higher incidence of MD in both the P1P1 and the P4P4 haplotypes (80%, 85%) when compared with the P1P4 chicks (27%, P<0.001). There were not enough birds in each respective haplotype to evaluate the L system. The overall incidence of MD in the specific pathogen free sentinel chicks was 71%. A publication is in preparation.
Impacts
This research will provide valuable information on the pathogenesis of Marek's disease in chickens.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
Evaluation of the Y system genes within a moderately susceptible B system background: We want to further investigate the influence of the Y system on MD resistance by concentrating on the Y alleles degree of influence in a more moderate B system background than B11. Other researchers have had difficulty demonstrating an effect of the Y system on MD when evaluated in less resistant chickens. Previously, 2 trials were conducted. In the last year, we conducted two additional pathogenicity studies which ended in July. One hundred and forty three chicks bearing the moderate B2,5 background genes were tested. On gross postmortem examination, 25 birds had lesions of MD compared with 15/30 SPF control birds. Histopathology, clinical chemistry analysis and genotyping are ongoing. Evaluation of the influence of non-Major Histocompatibility Complex genes on Marek's Diseases resistance: We have completed 7 challenge trials to date. Data were analyzed using the chi-square test to
examine the homogeneity of disease incidence among haplotypes within each of the non-MHC systems. Overall, the C, D, H and I systems did not show any significant positive or negative effect on development of MD. Statistically significant differences were observed only within the P system. Birds having a B19B19P1P1 haplotype had a significantly lower incidence of MD (21%) when compared with birds bearing the B19B19P4P4 haplotype (73%, P<0.001). In chicks with the B19B21 background, there was a significantly higher incidence of MD in both the P1P1 and the P4P4 haplotypes (80%, 85%) when compared with the P1P4 chicks (27%, P<0.001). There were not enough birds in each respective haplotype to evaluate the L system. The overall incidence of MD in the specific pathogen free sentinel chicks was 71%. If chicks become available, we want to conduct 1-2 additional trials in order to increase the bird numbers for evaluation of the L system.
Impacts
This research will provide valuable information on the pathogenesis of Marek's disease in chickens.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Production of commercial type genetic stock containing the B11 haplotype: This will allow us to determine whether the B11 gene will confer as strong a resistance to Marek's disease virus (MDV) when it is bred into commercial stock as it has with our Ancona X genetic line. White Leghorn stock for use in pathogenesis studies will arrive Summer 2003. Breeding for the broiler line is in progress. Evaluation of the Y system genes within a moderately susceptible B system background: We want to further investigate the influence of the Y system on MD resistance by concentrating on the Y alleles degree of influence in a more moderate B system background than B11. Other researchers have had difficulty demonstrating an effect of the Y system on MD when evaluated in less resistant chickens. Previously, 2 trials were conducted. In the last year, we conducted two additional pathogenicity studies which ended in July. One hundred and forty three chicks bearing the moderate B2,5
background genes were tested. On gross postmortem examination, 25 birds had lesions of MD compared with 15/30 SPF control birds. Histopathology, clinical chemistry analysis and genotyping are ongoing. Evaluation of the influence of non-Major Histocompatibility Complex genes on Marek's Diseases resistance: We have completed 7 challenge trials to date. Data were analyzed using the chi-square test to examine the homogeneity of disease incidence among haplotypes within each of the non-MHC systems. Overall, the C, D, H and I systems did not show any significant positive or negative effect on development of MD. Statistically significant differences were observed only within the P system. Birds having a B19B19P1P1 haplotype had a significantly lower incidence of MD (21%) when compared with birds bearing the B19B19P4P4 haplotype (73%, P<0.001). In chicks with the B19B21 background, there was a significantly higher incidence of MD in both the P1P1 and the P4P4 haplotypes (80%, 85%) when
compared with the P1P4 chicks (27%, P<0.001). There were not enough birds in each respective haplotype to evaluate the L system. The overall incidence of MD in the specific pathogen free sentinel chicks was 71%. A publication is in preparation on the P system data. If chicks become available, we want to conduct 1-2 additional trials in order to increase the bird numbers for evaluation of the L system.
Impacts
Our goal with this portion of the project is to produce both a commercial White Leghorn line and a commercial broiler line of chickens that contain the B11 gene without interference of the Ancona chicken background genes.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
We want to produce both a commercial White Leghorn line and a commercial broiler line of chickens that contain the B11 gene (MD resistant gene) without interference of the Ancona chicken background genes that were present in our research chickens. This will allow us to determine whether the B11 gene will confer as strong a resistance to MD virus (MDV) when it is bred into commercial stock as it has with our Ancona X genetic line. Currently, we are continuing backcrossing the Ancona X chickens that contain the B11 haplotype into commercial type White Leghorn chickens and have approximately 80% of the Ancona background removed. We want to further investigate the influence of the Y system on MD resistance by concentrating on the Y alleles degree of influence in a more moderate B system background than B11. Other researchers have had difficulty demonstrating an effect of the Y system on MD when in less resistant chickens. We are conducting 3 trials using the moderately
susceptible Ancona X White Leghorn B2B5 MHC background. Although we have insufficient data at this early phase to evaluate the Y system, the heterozygote background was somewhat more susceptible to the MD challenge than the B11 homozygotes. Finally, we have conducted 6 challenge trials to date in order to do a preliminary search for other potential gene complexes to concentrate on. Two were completed in this past granting year and 4 were reported on last year. Results of the last two trials supported the previous 4 trials. A total of 650 birds have been examined to date. Overall, the C, D, H and I systems did not show any significant positive or negative effect on development of MD and will not be focused on in future studies. Over all haplotypes, B19B19 birds had an MD incidence of 41% and the MD incidence in B19B2 birds was 62%. Statistically significant differences were observed only within the P system. Birds having a B19B19P1P1 haplotype had a significantly lower incidence of MD
(21%) when compared with birds bearing the B19B19P4P4 haplotype (73%, P<0.001). In chicks with the B19B21 background, there was a significantly higher incidence of MD in both the P1P1 and the P4P4 haplotypes (80% and 85%, respectively) when compared with the P1P4 chicks (27%, P<0.001). Incidence of MD in the SPF control chicks was 71%. There were not enough birds in each respective haplotype to evaluate the L system.
Impacts
Our goal with this project is to both evaluate the different genes that influence Marek's disease (MD) and to produce chicken lines that would be resistant to MD. Most of the important genes are contained in the Major Histocompatibility or 'B' complex portion of the genome. Other areas include the 'Y', 'P', and 'L' complexes. These preliminary data show that at least the P system influences the incidence of MD after challenge. We want to conduct 2-3 additional trials in order to increase the bird numbers for evaluation of the L system and confirm our findings on the P system.
Publications
- Wakenell, P.S., Briles, W.E., Myint, M.S., Farver, T., and D.B. 2001. Link. Investigation of the role of non-MHC alloantigen systems on Marek's disease pathogenicity in chickens. Proceedings of the 138th Annual Convention of the American Veterinary Medical Association, July 14-18, 2001.
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Progress 01/01/00 to 12/31/00
Outputs
Most of the important genes are contained in the Major Histocompatibility or "B" complex portion of the genome. Other areas include the "Y", "P", and "L" complexes. We want to produce both a commercial White Leghorn line and a commercial broiler line of chickens that contain the B11 gene (MD resistant gene) without interference of the Ancona chicken background genes that were present in our research chickens. This will allow us to determine whether the B11 gene will confer as strong a resistance to MD virus (MDV) when it is bred into commercial stock as it has with our Ancona X genetic line. Currently, we are continuing backcrossing the Ancona X chickens that contain the B11 haplotype into commercial type White Leghorn chickens and have approximately 60% of the Ancona background removed. We want to further investigate the influence of the Y system on MD resistance by concentrating on the Y alleles degree of influence in a more moderate B system background than B11.
Other researchers have had difficulty demonstrating an effect of the Y system on MD when in less resistant chickens. We have conducted 2 trials using the moderately susceptible Ancona X White Leghorn B2B5 MHC background. Although we have insufficient data at this early phase to evaluate the Y system, the heterozygote background was somewhat more susceptible to the MD challenge than the B11 homozygotes (Trial 1, 26/84 or 31% birds positive; Trial 2 12/56 or 21% birds positive). Finally, we have conducted 6 challenge trials to date in order to do a preliminary search for other potential gene complexes to concentrate on. Two were completed in this past granting year and 4 were reported on last year. Results of the last two trials supported the previous 4 trials.. Overall, the C, D, H and I systems did not show any significant positive or negative effect on development of MD and will not be focused on in future studies . Statistically significant differences were observed only within the
P system. Birds having a B19B19P1P1 haplotype had a significantly lower incidence of MD (21%) when compared with birds bearing the B19B19P4P4 haplotype (82%, P<0.001). In chicks with the B19B21 background, there was a significantly higher incidence of MD in both the P1P1 and the P4P4 haplotypes (85%) when compared with the P1P4 chicks (34%, P<0.001). There were not enough birds in each respective haplotype to evaluate the L system. These preliminary data show that at least the P system influences the incidence of MD after challenge. We want to conduct 2-3 additional trials in order to increase the bird numbers for evaluation of the L system and confirm our findings on the P system.
Impacts
This project will both evaluate the different genes that influence Marek's disease (MD) and help to produce chicken lines that will be resistant to MD.
Publications
- No publications reported this period
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Progress 01/01/99 to 12/31/99
Outputs
Currently, we are continuing backcrossing the Ancona X chickens that contain the B11 haplotype into commercial type White Leghorn chickens and have approximately 60% of the Ancona background removed. We expect to have a White Leghorn line that contains less than 5 % of the Ancona background genes within the next granting year. Breeding for the broiler line will be initiated when the White Leghorn line is completed. The Major Histocompatibility Complex (MHC) has been proven to be associated with resistance or susceptibility to certain diseases in the chicken. There is a strong link between resistance/susceptibility and the MHC (B system) with MDV. However, breeding for resistance against MDV by selecting for known resistant genes is not always successful. Recently, another group of genes located on the same chromosome as the MHC but not in the traditional area were also found to influence MDV. Our objective of this portion of the project is to ascertain whether there
are other genes that may also influence MDV resistance. We are concentrating on genes that encode for proteins that are located on the surface of leukocytes. Leukocytes are one of the major cell types involved in the immune response and it is known that they use proteins on their cell surfaces to communicate with other cells during the immune response. These genes include the C, D, H, I, L, and P systems (groups of similar genes). We have completed 6 challenge trials to date in order to do a preliminary search for potential systems to concentrate on. These trials were conducted using chicks that came from parent stock whose genes were controlled so that the above systems were the only variable genes from chick to chick. We chose to keep the background MHC as either highly susceptible (B19B19) or moderately susceptible (B19B21) for MDV. The chicks were hatched, wing banded for identification and raised in a common room. At 5 days of age, they were all challenged by intra- abdominal
injection with a virulent strain of MDV. At this time, highly susceptible specific pathogen free chicks from a commercial supplier were added to the experimental flock in order to evaluate the shed of the virus from the experimental birds. Blood was obtained from all birds in order to verify there haplotypes (genes). The studies were terminated 75 days post-challenge and all birds surviving to this point and those that died during the trial were examined for gross and/or microscopic lesions of MDV. The results presented are based upon the first 4 trials with the remaining two ongoing. The incidence of MD in the specific pathogen free sentinel chicks was: Trial 1: 4/12 (33%), Trial 2: 10/12 (83%), Trial 3: 5/13 (39%) and Trial 4: 16/18 (89%). These preliminary data show that at least the P system influences the incidence of MD after challenge. We will be continuing trials in order to increase the bird numbers for evaluation of the D and L systems and confirm our findings on the P
system.
Impacts
Our goal with this portion of the project is to produce both a commercial White Leghorn line and a commercial broiler line of chickens that contain the B11 gene without interference of the Ancona chicken background genes. This will allow us to determine whether the B11 gene will confer as strong a resistance to Marek's disease virus (MDV) when it is bred into commercial stock as it has with our Ancona X genetic line.
Publications
- Wakenell, P.S., Miller, M.M. and W.E. Briles. 1999. Influence of major histocompatibility complex haplotype B-11 on Marek's disease immunity. Proceedings of the 136th Annual Convention of the American Veterinary Medical Association(abstract).
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