THE MAJOR HISTOCOMPATIBILITY COMPLEX OF CHICKENS CONTROLS THE INFECTION OF EARLY CHICKEN EMBRYOS BY MC29 VIRUS

Embryos from isogeneic chicken lines belonging to different haplotypes and known to be resistant to infection by avian retroviruses of subgr oups A and E were infected on the 3rd (E3) and 5th day (E5) of incubat ion with MC29 virus (MC29-RAV-1 pseudotype; A subgroup-derived envelop e). Despite the trait for resistance, E3 embryos developed the specifi c heart tumors previously described in outbred E3 embryos. The CB line (B12/812, C/AE) was more susceptible than the congenic line CC (84/84 , C/AE). In both lines, the heart was the unique target at E3 for MC29 . No tumors of the heart or other organs appeared upon infection at E5 or E10. In the A subgroup susceptible line 6 (B2/B2, C/E) both heart (50%) and skin (100%) were transformed upon E3 infection. Hybrids of l ine 6 with the CB line expressed skin (100%) and heart (95.4%) tumors. On the other hand, the 6 x CC combination revealed 96.7% of skin tumo rs while heart tumors occurred only in 1 of 31 embryos (3.2%). To dist inguish the respective influences of the MHC and of the tv-a allele, c rosses with the la line (B7/B7, C/O) were carried out and tested with MC29. The findings indicate that resistance of the embryos to MC29 hea rt tumors is associated with the 84/84 haplotype, supporting the inter pretation that the MHC has a role in MC29 cell tropism and v-myc expre ssion. The target cells in tumors were determined by immunofluorescenc e staining. Cells infected in the heart belonged to the myogenic linea ge, as expected from previous studies. In skin anomalies the epidermal cells were double-stained with anticytokeratin and anti-env antibodie s, many cells in the dermis also reacted with anti env antibodies. (C) 1994 Academic Press, Inc.