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Variations in lentiviral gene expression in monocyte-derived macrophages from naturally infected sheep
Y Chebloune1, B Karr, D Sheffer
1Department of Microbiology, Marion Merrell Dow Laboratory of Viral Pathogenesis, Kansas University Medical Center, Kansas City 66160-7424, USA. YCheblou@KUMC.edu
Abstract:
Seventy-nine 1-year-old lambs from three individual farms and a feedlot were examined for natural lentivirus infection. We used three different methods to detect infection and to identify the stage of the ovine lentivirus life cycle in blood-derived macrophages. Cytopathic infectious virus was obtained from 14/14 Border Leicester animals obtained from a naturally infected flock. Neither virus particles, virus proteins, virus specific antibodies nor viral DNA were detected in samples from 34 lambs from two South Kansas City farms. However, among 31 feedlot lambs, we identified 11 infected animals. Specific viral proteins were immunoprecipitated from macrophages of one animal, but no infectious cytopathic virus was isolated from these cells. Cells from ten of the other feedlot animals harboured viral DNA but neither viral particles nor proteins could be detected by our techniques. Thus, in these naturally infected animals, the virus life cycle either proceeded to completion, subject to differentiation of infected precursor cells in blood, or remained arrested at the DNA stage despite maturation of monocytes to macrophages. Sequence analysis of the env gene of viral genomes from two of the ten feedlot sheep showed sequences distinct from those of known ovine and caprine lentiviruses. Surprisingly, these sequences have a higher identity (of nucleotide and derived amino acid sequences) to caprine arthritis-encephalitis virus than to the ovine prototype, maedi-visna virus. These data suggest that the ovine and caprine lentiviruses found in North American sheep may have a common ancestral genotype that is closely related to the caprine virus.
Insights
Ovine lentivirus infection was studied in 79 lambs. Some lambs showed full infection, while others had arrested viral DNA, suggesting varied disease stages and a potential common ancestor with caprine lentivirus.
Area of Science:
- Veterinary Virology
- Molecular Biology
- Infectious Diseases
Background:
- Ovine lentivirus (OvLV) causes significant economic losses in sheep farming.
- Understanding the OvLV life cycle and genetic diversity is crucial for disease control.
- North American lentiviruses in sheep show complex infection patterns.
Purpose of the Study:
- To investigate natural lentivirus infection in North American sheep.
- To characterize the ovine lentivirus life cycle stages in infected animals.
- To determine the genetic relationship of North American ovine lentiviruses to known caprine lentiviruses.
Main Methods:
- Sample collection from 79 lambs across three farms and a feedlot.
- Detection of infectious virus, viral proteins, antibodies, and viral DNA.
- Macrophage culture and differentiation for in vitro infection studies.
- Sequence analysis of the viral env gene.
Main Results:
- Infectious virus detected in 14/14 Border Leicester lambs from an infected flock.
- No evidence of infection in 34 lambs from two South Kansas City farms.
- 11/31 feedlot lambs showed signs of infection, with varied stages (viral DNA, proteins, or arrested).
- Env gene sequences from feedlot sheep showed higher identity to caprine arthritis-encephalitis virus (CAEV) than to maedi-visna virus (MVV).
Conclusions:
- Ovine lentivirus infection presents diverse life cycle stages in naturally infected sheep.
- North American ovine and caprine lentiviruses may share a common genotype related to CAEV.
- Further research is needed to elucidate the evolutionary origins and transmission dynamics of these lentiviruses.