ovalbumin and Avian-Leukosis

Myeloblastosis-associated virus type 1 (MAV-1) is an exogenous avian retrovirus with oncogenic potential. MAV-1 was detected in young chicks hatching from eggs produced by an experimental genetic line of egg-type chickens. Transmissibility of MAV-1 had not been documented previously. This investigation was intended to partially characterize the virus involved and to study its transmissibility and oncogenicity in naturally and contact-infected chickens. Commercially produced white and brown layer pullets free of exogenous avian leukosis viruses were commingled at hatch with naturally MAV-1-infected chickens. The original MAV-1-infected chickens were discarded after approximately 8 wk, and the contact-exposed chickens were maintained in isolation for 36 wk. Young specific-pathogen-free (SPF) single comb white leghorn chickens were added to the group to study possible horizontal transmission of MAV-1 in young chickens. Upon weekly virus isolation attempts, MAV-1 was readily isolated from the contact-exposed white layers but not from the brown layers between 36 and 53 wk of age (18 wk in total). Three-week-old SPF chickens were readily infected with MAV-1 by contact as early as 1 wk postexposure. Throughout 22 hatches derived from the white and brown MAV-1-contact-exposed layers (between 36 and 53 wk of age), MAV-1 was frequently detected in the white layer progeny, whereas the virus was seldom isolated from the progeny produced by the brown layers during the same 18-wk period. MAV-1 induced a persistent infection in some of the SPF chickens that were exposed by contact at 3 wk of age. Gross tumors were not detected in any of the originally infected experimental chickens at 8 wk of age, in the contact-exposed brown or white layers at the termination of the study at 53 wks of age, or in the contact-exposed SPF chickens at the end of the study at 12 wk of age. Exogenous avian leukosis-related viruses may still be detected in egg-type chickens, emphasizing the importance of thorough screening before incorporation of experimental genetic material into commercial genetic lines of egg-type chickens.

Topics: Animals; Antibodies, Viral; Avian Leukosis; Avian Myeloblastosis Virus; Chickens; DNA, Viral; Enzyme-Linked Immunosorbent Assay; Female; Male; Ovalbumin; Phylogeny; Poultry Diseases; Sequence Analysis, DNA; Specific Pathogen-Free Organisms; Viremia

1. The course of infection by exogenous avian leukosis virus was followed in a commercial strain of White Leghorn domestic fowls by measuring viral antigen in feather pulp and egg albumin. Ten days after hatching, 2 out of 360 birds tested positive and at 286 days of age about 60% of the birds had been antigen positive at least once. 2. Among the antigen positive birds, two groups could be distinguished: those which permanently and those which transiently expressed viral antigen. Permanent antigen expression was associated with low antibody titres, while transient antigen expression was associated with high antibody titres. 3. The strain segregated for the two endogenous viral genes ev6 and ev9, both of which express endogenous viral envelope protein, and have been implicated in affecting immune-responsiveness. The antibody titre in individuals positive for both ev6 and ev9, was significantly lower than in those which had none or only one of the two ev-genes. In addition, individuals positive for both ev-genes occurred more frequently in the group permanently positive for viral antigen than in the group transiently antigen positive. 4. The results indicate that there was a strong synergism between ev6 and ev9 in reducing the antibody response to exogenous avian leukosis virus infection, perhaps by inducing immune tolerance or interfering with antibody formation.

Topics: Animals; Antibodies, Viral; Antigens, Viral; Avian Leukosis; Avian Leukosis Virus; Chickens; Enzyme-Linked Immunosorbent Assay; Feathers; Genes, Viral; Immune Tolerance; Immunity; Immunoglobulin G; Ovalbumin; Poultry Diseases

An enzyme-linked immunosorbent assay (ELISA) for detecting avian leukosis virus (ALV) antigens was developed with rabbit anti-ALV serum. The ELISA detected purified ALV of subgroups A and B at a concentration of 0.4 ng/well and about 10(3) infectious units/well estimated by a resistance-inducing factor (RIF) test, and antigens in culture fluids from chicken embryo fibroblasts infected with subgroups A, B or E of ALV. These results showed that common antigens among the subgroups were detected by the ELISA. When virus titration was performed, virus infectivity could be determined by the ELISA within 7 days after cultivation. The titer was similar to that obtained by the RIF test on 19 days after 3 subcultures. These results indicate that the ALV-isolation test by the ELISA was superior to the RIF test in rapidity and applicability to large-scale field trials. Four specific pathogen-free (SPF) chicken lines maintained in this laboratory were examined for endogenous ALV antigens by the ELISA. Sera from laying hens had considerably high absorbance (A) values, whereas albumen samples showed low A values except for some samples (7/40 hens). Although most of sera from 1-day-old SPF chicks showed lower A values than those from laying hens, some sera showed A values as high as those from viremic chicks in 2 lines. Endogenous ALV was isolated from sera from laying hens (6/40) and their albumens (4/7) with high A values. Two SPF chicken lines were found to produce endogenous virus at a high frequency.

Topics: Animals; Antigens, Viral; Avian Leukosis; Avian Leukosis Virus; Cells, Cultured; Chick Embryo; Chickens; Enzyme-Linked Immunosorbent Assay; Female; Immune Sera; Ovalbumin; Predictive Value of Tests; Specific Pathogen-Free Organisms; Viremia

On the basis of earlier studies, a programme for eradicating exogenous avian leukosis virus from commercial poultry stock was devised and applied to 11 layer breeder lines. After three years of testing, avian leukosis virus infection was eradicated completely from all but one, a slow-feathering line.

Topics: Animals; Avian Leukosis; Avian Leukosis Virus; Chickens; Enzyme-Linked Immunosorbent Assay; Female; Ovalbumin; Poultry Diseases; United Kingdom; Vaginal Smears

Congenital transmission of avian leukosis virus (ALV) in the absence of detectable amounts of group specific (gs) antigen in egg albumen was found to occur in one commercial and one specific pathogen-free (SPF) flock. The prevalence of congenitally transmitting hens which did not excrete gs antigen was particularly high in a commercial flock where 26/27 hens transmitted ALV. Some of the ALV-transmitting hens in the commercial flock had virus in vaginal swabs thus enabling infection to be detected. The reasons for such a high proportion of congenitally transmitting hens which did not shed detectable amounts of gs antigen in the commercial flock was not determined. In the SPF flock, 2/15 hens congenitally transmitted ALV although virus could not be detected in vaginal swabs, whole blood or egg albumen and antibodies to subgroups A or B were not present. This form of ALV-infection persisted in two successive generations. These results indicate the necessity of testing for infectious ALV in embryos, in order to ascertain that a flock is genuinely free of ALV.

Topics: Animals; Antigens, Viral; Avian Leukosis; Avian Leukosis Virus; Chickens; Female; Male; Ovalbumin; Specific Pathogen-Free Organisms

RAV-0, an endogenous avian leukosis virus, does not undergo congenital transmission in infected K28 chickens. In contrast, avian leukosis viruses of exogenous origin undergo highly efficient congenital transmission. The relative abilities of endogenous and exogenous viruses to undergo congenital transmission appear to be determined by the p27 capsid proteins of these viruses.

Topics: Animals; Avian Leukosis; Avian Leukosis Virus; Capsid; Chickens; Eggs; Female; Ovalbumin

Twenty-eight broiler breeder flocks were tested for avian leukosis virus (ALV) group-specific (gs) antigen shedding into the albumen. The rate of shedding ranged from 0 to 17%, rates substantially lower than those observed previously in egg production stocks. The flock shedding at the highest rate was trap nested and dams positive and negative for gs antigen shedding in the albumen produced progeny for a growth trial. Chicks produced by the positive and negative dams had 27 and 1% ALV isolations from their meconia, respectively. Progeny of positive dams or chicks having virus in their meconia weighed 1 to 3% less at 4 and 7 weeks than progeny of negative dams. More infected chicks died or were runted by 7 weeks. Although the proportion of infected chicks and the lower weight gain is very small, the previously reported loss in breeder flock productivity and livability suggest broiler breeders should consider reducing ALV shedding in higher incidence female lines.

Topics: Animals; Antigens, Viral; Avian Leukosis; Avian Leukosis Virus; Body Weight; Chickens; Complement Fixation Tests; Feces; Female; Male; Ovalbumin

The presence of avidin, a progesterone-dependent oviductal glycoprotein, was studied in viral tumors. Newborn chickens were infected with the acute leukemia virus OK 10, and the first tumors occurred within 2-3 weeks. Avidin was assayed using a [14C]biotin-binding method and radioimmunoassay. In the control chickens, avidin concentrations were less than 0.3 microgram/g in the plasma and less than 1.5 microgram/g in various tissues including the immature oviduct. In the OK 10 virus-infected chickens, no significant induction was observed during the acute infection or any time thereafter if no tumors were seen. In chickens that developed tumors, avidin concentrations were significantly increased in tumorous tissue only located in the mesenterium and occasionally in the oviduct. In tumors occurring elsewhere (kidney, ovary, muscle, testis, liver, colon) avidin concentrations were not elevated. Tumor-associated avidin had extraordinary biotin-binding capacity after treatment at +90 degrees C similar to the progesterone-dependent avidin, whereas antibody-binding properties suggested that tumor-associated avidin may have a somewhat altered antigenic structure.

Topics: Animals; Avian Leukosis; Avian Leukosis Virus; Avidin; Chickens; Kinetics; Lung; Ovalbumin; Oviducts

The association of subclinical infections with lymphoid leukosis virus and performance was investigated in a randombred White Leghorn type population. The proportion of birds shedding group specific (gs) antigen into their egg albumen was high (23.8%). Birds with gs antigen in their albumen matured later, produced fewer and smaller eggs, and grew less rapidly tha their nonshedding counterparts.

Topics: Animals; Antigens, Viral; Avian Leukosis; Avian Leukosis Virus; Body Weight; Chickens; Complement Fixation Tests; Female; Male; Ovalbumin; Oviposition; Poultry Diseases