Hartley and Rowel reported that the in vitro focus-forming effects of Moloney sarcoma virus (MSV)2 I depended on the presence in the same cells of two virus particles, a defective i\ISV particle and a fully infectious Moloney leukemia particle. Superinfection with additional Moloney leukemia virus potentiated focus formation by MSV, converting a "two-hit" dose response curve to a one-hit curve;...

An avian leukosis virus with a wide host range belonging to a new subgroup for chickens was isolated from meat-type chicken lines. The virus, of which HPRS-103 strain is the prototype, was of low oncogenicity in chickens but appeared to behave like an exogenous leukosis virus. Neutralizing antibodies to the virus were found in three of five meat-type chicken lines, but not in seven layer lines....

Avian leukosis virus subgroup J (ALV-J), an exogenous avian retrovirus, is thought to have evolved by recombination with the highly identical env gene of the endogenous avian retrovirus EAV-HP. Embryonic expression of EAV-HP env has been suggested to be associated with the induction of immunological tolerance, a feature observed in a significant proportion of meat-type chickens infected with AL...

Following the observations on high-speed centrifugation of the avian sarcoma agent by various investigators,1' 8,10,11,12 similar studies of the agent of fowl leukosis have been undertaken. Since the neoplastic nature of this disease is now rather generally recognized, observations on the filterable agent of chicken leukosis have assumed new significance for the study of the etiology of fowl ne...

With total dependence on the host cell, several viruses have adopted strategies to modulate the host cellular environment, including the modulation of microRNA (miRNA) pathway through virus-encoded miRNAs. Several avian viruses, mostly herpesviruses, have been shown to encode a number of novel miRNAs. These include the highly oncogenic Marek's disease virus-1 (26 miRNAs), avirulent Marek's dise...

In order to ensure the safety of vaccines produced on avian cells, rigorous testing for the absence of avian retroviruses must be performed. Current methods used to detect avian retroviruses often exhibit a high invalid-test/false-positive rate, rely on hard-to-secure reagents, and/or have readouts that are difficult to standardize. Herein, we describe the development and validation of two cons...

The commercially important neoplastic diseases of poultry are Marek's disease, which is caused by a herpesvirus, and the avian leukoses and reticuloendotheliosis, which are caused by retroviruses. These diseases are responsible for economic loss due to both mortality and depressed performance. Marek's disease virus (MDV) and avian leukosis viruses (ALVs) are prevalent throughout the world, and ...

The resolution of genes that determine resistance to disease is described using chicken lines maintained at the Avian Disease and Oncology Laboratory (ADOL). This description includes a summary 1) of existing selected and inbred lines differing for resistance to viral-induced tumors, i.e., Marek's disease (MD) and lymphoid leukosis (LL), and of the use of inbred and line crosses to define relev...

A new subgroup of avian leukosis virus (ALV) that includes a unique env gene, designated J, was identified recently in England. Sequence analysis of prototype English isolate HPRS-103 revealed several other unique genetic characteristics of this strain and provided information that it arose by recombination between exogenous and endogenous virus sequences. In the past several years, ALV J type ...

The spring-loaded model stipulates that influenza virus infection is coupled to the transition of the virus hemagglutinin (HA) from a metastable conformation to a highly stable conformation at low pH. The properties of retrovirus envelope glycoproteins indicate that infection is coupled to an analogous conformational change. As a test of this hypothesis, the requirements for avian leukosis viru...