Neonatal calf infection with respiratory syncytial virus: drawing parallels to the disease in human infants.
Respiratory syncytial virus (RSV) is the most common viral cause of childhood acute lower respiratory tract infections. It is estimated that RSV infections result in more than 100,000 deaths annually worldwide. Bovine RSV is a cause of enzootic pneumonia in young dairy calves and summer pneumonia in nursing beef calves. Furthermore, bovine RSV plays a significant role in bovine respiratory disease complex, the most prevalent cause of morbidity and mortality among feedlot cattle. Infection of calves with bovine RSV shares features in common with RSV infection in children, such as an age-dependent susceptibility. In addition, comparable microscopic lesions consisting of bronchiolar neutrophilic infiltrates, epithelial cell necrosis, and syncytial cell formation are observed. Further, our studies have shown an upregulation of pro-inflammatory mediators in RSV-infected calves, including IL-12p40 and CXCL8 (IL-8). This finding is consistent with increased levels of IL-8 observed in children with RSV bronchiolitis. Since rodents lack IL-8, neonatal calves can be useful for studies of IL-8 regulation in response to RSV infection. We have recently found that vitamin D in milk replacer diets can be manipulated to produce calves differing in circulating 25-hydroxyvitamin D3. The results to date indicate that although the vitamin D intracrine pathway is activated during RSV infection, pro-inflammatory mediators frequently inhibited by the vitamin D intacrine pathway in vitro are, in fact, upregulated or unaffected in lungs of infected calves. This review will summarize available data that provide parallels between bovine RSV infection in neonatal calves and human RSV in infants.
Ruminant Diseases and Immunology Unit, National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, Iowa 50010, USA. Randy.Sacco@ars.usda.gov
Randy E
RE
Sacco
Jodi L
JL
McGill
Mitchell V
MV
Palmer
John D
JD
Lippolis
Timothy A
TA
Reinhardt
Brian J
BJ
Nonnecke
D000818:Animals; D000831:Animals, Newborn; D055745:Bronchioles / Q000473:pathology; D002417:Cattle; D002418:Cattle Diseases / Q000473:pathology* / Q000821:virology*; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D007223:Infant; D009504:Neutrophils / Q000276:immunology; D020545:Respiratory Mucosa / Q000473:pathology; D018357:Respiratory Syncytial Virus Infections / Q000473:pathology* / Q000662:veterinary*; D012136:Respiratory Syncytial Viruses / Q000472:pathogenicity*; D014807:Vitamin D / Q000378:metabolism
D016207:Cytokines; D014807:Vitamin D