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Subgroup-A Rous sarcoma virus-induced growth stimulation of chick embryos infected via the chorioallantoic membrane
1Indian Veterinary Research Institute, Izatnagar, India.
Insights
Chicks infected with Rous sarcoma virus (RSV) subgroup A showed improved growth. However, chicks with lymphoid leukosis virus (LLV) antigens in eggs exhibited poor growth, indicating complex viral effects on avian development.
Area of Science:
- Avian Virology
- Poultry Genetics
- Disease Resistance
Background:
- Lymphoid leukosis virus (LLV) infection in chicks leads to poor growth.
- Identifying LLV-A resistant/susceptible genotypes requires precise methods.
- Rous sarcoma virus (RSV) subgroup A is homologous to LLV-A.
Purpose of the Study:
- To evaluate the effect of RSV subgroup A infection on embryonic growth in different chicken breeds.
- To compare growth parameters between infected and control groups.
- To investigate the influence of viral dose and egg size on chick growth.
Main Methods:
- Chorioallantoic membrane (CAM) assay and liver tumour (LT) assay were used for precise identification.
- Progeny testing was employed to identify resistant and susceptible genotypes.
- Experiments were conducted on White Leghorn (light breed) and Rhode Island Red (heavy breed) chickens.
Main Results:
- Infected LT-negative chicks showed a highly significant (P < 0.01) increase in mean relative body weight (rbw) by 2% compared to controls.
- Neither viral inoculation dose nor egg size significantly affected the rbw of day-old chicks (P > 0.05).
- No significant difference in rbw was observed between LT-positive and control chicks.
Conclusions:
- RSV subgroup A infection can enhance embryonic growth in certain contexts.
- LLV presence in eggs is associated with impaired chick growth.
- Further research is needed to fully elucidate the complex interactions between avian viruses and host genetics affecting growth.
Abstract:
Chicks that hatch from eggs containing group specific antigen (gs antigen) of lymphoid leukosis virus (LLV) subgroups, grow poorly. In our laboratory for more precise identification of LLV-of subgroup A (LLV-A) resistant and susceptible genotypes by progeny testing, the chorioallantoic membrane (CAM) assay in complemented by liver tumour (LT) assay, wherein Rous sarcoma virus (RSV) of subgroup A (homologous to LLV-A) was used. The present study was conducted in a light breed (White Leghorn) and also in a heavy breed (Rhode Island Red) to ascertain the effect of infection on embryonic growth by RSV subgroup A. Mean relative body weight (rbw) of infected LT negative chicks of either breed exceeded the control highly significantly (P < 0.01) by 2%. However, neither the dose of virus inoculated per embryo, nor egg size influenced the relative body weight of day old chicks (P > 0.05). No difference in relative body weight of LT positive and control chicks was observed.