Molecular and biological aspects of porcine rubulavirus (LPMV) lytic and persistent infectionsHjertner, Bernt
This thesis summarises and discusses results of studies on the porcine rubulavirus (LPMV). LPMV is the causative agent of blue eye disease of pigs. The specific goals of these studies have been to establish the relatedness of LPMV to other members of the family paramyxoviridae and to describe different aspects of persistent infections in both cell cultures and pigs.
Study I is an analysis of the phosphoprotein (P) gene, which is an essential component of the viral polymerase. LPMV was found to have the P gene organised in a way similar to other members of the rubulavirus genus including the human pathogen mumps virus. Rubulaviruses commonly have an open reading frame which does not encode the P protein but instead encodes a protein designated V. The P protein is expressed by an mRNA in which two additional nontemplated G nucleotides are inserted by the viral polymerase (editing). The editing event occurs at a frequency of-50% for LPMV.
Studies H and m describes the establishment and molecular characterisation of a persistent infection in porcine kidney cells in vitro. The cells showed reduced amounts of the L protein and to a certain extent the P protein, which was reflected in low mRNA levels and a shift in the editing frequency, respectively. Several subgenomic RNAs were also identified. Any of these changes could theoretically have the capacity to modulate an infection, and could ultimately lead to a persistent state.
Study IV addresses the possibility ofwhether porcine rubulavirus could remain in acute infected pigs after full recovery from the disease. Virus could only be detected in organ samples from pigs which had recovered from acute LPMV infection by RT-PCR. This was especially evident after pigs were immunosuppressed, enabling detection of LPMV RNA in the lung. Furthermore, evidence that LPMV was still transcriptionally active was also obtained. The persistence ofLPMV in tissues could be of clinical importance, and the risk of reactivation and shedding of virus in situations of immunosuppression could have profound effects on the epidemiology of the disease.
Keywordsporcine rubulavirus (LPMV); persistent infection; L protein; P protein; transcription; editing; subgenomic RNA
Published inActa Universitatis Agriculturae Sueciae. Veterinaria
1997, number: 17
Publisher: Swedish University of Agricultural Sciences