Detection and expression of bovine papillomavirus in blood of healthy and papillomatosis-affected cattle.

Papillomaviruses (PV) are double-stranded DNA viruses that can cause benignant and malignant tumors in amniotes. There are 13 types of bovine papillomavirus (BPV-1 to -13); they have been found in reproductive tissues and body fluids. Normally these viruses are detected in epithelial tissue. We looked for BPV in the blood of healthy cattle and cattle with papillomatosis, using PCR and RT-PCR. BPV types 1 and 2 were detected in 8/12 blood samples of asymptomatic bovines and in 8/9 samples from cattle with papillomatosis. Six of 8 asymptomatic samples positive for BPV also showed expression for BPV. Five of 6 samples were positive for E2 expression, while 3/6 samples were positive for E5 expression. Five of 8 symptomatic samples positive for BPV also showed BPV expression. Five of 5 were positive for E2 expression, while 1/5 was positive for E5 expression. Two of 6 blood samples of asymptomatic cattle and 1/5 symptomatic blood samples scored positive for both E2 and E5 expression. This is the first study showing expression of BPV genes in the blood of asymptomatic and papillomatosis-affected animals.

Expression of the bovine papillomavirus type 1, 2 and 4 L1 genes in the yeast Pichia pastoris.

Papillomaviruses are known to cause benign or malignant lesions in various animals. In cattle, bovine papillomavirus (BPV) is the etiologic agent of papillomatosis and neoplasia of the upper gastrointestinal tract and urinary bladder. Currently, there are no standard diagnostic tests or prophylactic vaccines. Protection against papillomavirus infection is conferred by neutralizing antibodies directed towards the major structural protein L1. These antibodies can be efficiently induced by immunization with virus-like particles that are formed spontaneously after L1 gene expression in recombinant systems. The yeast Pichia pastoris is known to provide an efficient system for expression of proteins due to reduced cost and high levels of protein production. We evaluated P. pastoris for expression of the L1 gene from BPV1, BPV2 and BPV4. After methanol induction, the recombinants were able to produce L1 proteins of the three different BPV types. To increase heterologous L1 protein levels, a codon optimization strategy was used for production under bioreactor conditions. The BPV1 L1 protein was identified by monoclonal antibody anti-6xHis. This is the first report of BPV L1 expression in yeast.