Genetic Resistance to Marek’s Disease

Differential Cytokine Responses following Marek's Disease Virus Infection of Chickens Differing in Resistance to Marek's Disease

“…1). These markedly different patterns of viral load in splenocytes confirm earlier findings that different resistance mechanisms must operate in susceptible and resistant genotypes (reviewed by Bacon et al [2] and Calnek [14]). Differences in splenocyte viral loads in resistant lines from 10 dpi onwards are consistent with the hypothesis that different mechanisms operate in MHCrelated and non-MHC-related MD resistance (2,14).…”

“…To our knowledge, this is the first detailed comparison of early changes in MDV copy number in spleen cells of chicken genotypes that differ markedly in their resistance and mechanisms of resistance to MD (2,14,49). In earlier studies, these lines have been used in pairs: line N versus line P (1,13,20,39) and line 6 1 versus line 7 2 (3,4,32,45).…”

“…Genes within the class I (B-F) region are most influential, with the B21 haplotype (line N) expressing the lowest levels of class I but possessing the highest order of resistance (29), whereas the B19 haplotype (line P) expresses the highest levels of class I and represents the highest level of susceptibility. Other forms of genetic resistance are associated with genes outside of the MHC, the most notable examples being lines 6 1 and 7 2 , which are homozygous for the B2 haplotype (14,17). Line 6 1 is highly resistant, and line 7 2 is highly susceptible to clinical MD (32).…”

“…Due to the need for contemporaneous sampling of both control and infected chickens and comparisons between the four inbred lines, the experiment was carried out in two parts. The first involved only the MD-susceptible lines 7 2 and P, and the second involved the MD-resistant lines 6 1 and N. In each case, infected birds of both lines were housed in separate cages in the same filtered-air, positive-pressure isolation room and injected intra-abdominally with 1,000 PFU of the virulent serotype 1 MDV strain HPRS-16 (46) in a chick kidney cell (CKC) suspension (0.2 ml). Similarly, controls were kept together in a separate isolation room and injected intra-abdominally with the same number of uninfected CKC (0.2 ml).…”

Genomic Variation between Genetic Lines of White Leghorns Differed in Resistance to Marek’s Disease

“…Yet MD continues to cost the poultry industry, with an estimated revenue of over one billion dollars each year worldwide, which are incurred by the routine prevention measures and condemnation, and remains a serious threat to the poultry industry since commercial lines of chickens at large are susceptible to MD and new isolates of MD viruses (MDV) have been emerging with escalated virulence [6][7][8][9][10][11][12]. Therefore, current control measures using commercially available vaccines in the same routine as has been practiced during the last half century could be overwhelmed at an…”