Abstract
Avian leukosis virus subgroup J (ALV-J) is a new type of virus that mainly induces myeloid leukosis (ML) in chickens. To further elucidate the pathogenesis of ALV-J infection and tumor development, expression profiles from the bone marrow tissue of 15 infected and 18 non-infected birds from a local-breed poultry-farm under naturally infected conditions, were analyzed by suppression-subtractive hybridization. The birds were diagnosed as ML+ (or ML-) by specific ALV-J detection methods, involving serological tests for antigens and antibodies, and RT-PCR to detect viral RNA. A total of 59 partial gene sequences were revealed by differential screening of 496 forward and 384 reverse subtracted cDNA clones. Of these, 22 identified genes, including 8 up-regulated and 14 down-regulated, were related to immune functions, these genes being, MHC B-G antigen, translationally-controlled tumor protein (TPT1/TPTC), transferrin and ferritin, hemoglobin and Carbonic anhydrase. Four of the down-regulated genes were selected for further analysis, in view of their predicted roles in infection and immunity by real-time qRT-PCR, using RNA collected from the same birds as those used for SSH. The four genes were expressed at significantly lower levels (p < 0.001) in ALV-J infected birds than in non-infected ones.
Highlights
Avian leukosis viruses (ALV) constitute a group of avian retroviruses that induce malignant neoplasm in poultry
Two libraries of genes that were differentially expressed by Avian leukosis virus subgroup J (ALV-J) infection were constructed by suppressive subtractive hybridization (SSH)
Subtractions were validated when incapable of amplifying G3PDH from either subtracted SSH-cDNAs on using 18 to 33 cycles, this was readily detected with as few as 18 cycles from nonsubtracted cDNAs
Summary
Avian leukosis viruses (ALV) constitute a group of avian retroviruses that induce malignant neoplasm in poultry. The most recently identified subgroup, ALV-J, first isolated in the UK from broiler chickens in 1988 (Payne et al, 1991), was found to be associated with myeloid leukosis (ML). Initially it was assumed that the virus was restricted to the UK, cases of ML in broiler breeding-flocks have cropped up in several other European countries (Payne, 1998), Africa (Aly, 2000) and Australia (Bagust et al, 2004), indicating its world-wide distribution among commercial meat-type poultry (Landman et al, 2002). A flock was spontaneously infected with ALV-J, whereupon PCR-based suppressive subtractive hybridization (SSH) methods were applied to identify genes that were up and down-regulated. This study will aid in discovering candidate genes and contribute to a better understanding of the disease itself
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