ABSTRACT
Bovine herpesvirus 5 (BHV-5) is a neurovirulent alphaherpesvirus that causes fatal encephalitis in calves. In a rabbit model, the virus invades the central nervous system (CNS) anterogradely from the olfactory mucosa following intranasal infection. In addition to glycoproteins E and I (gE and gI, respectively), Us9 and its homologue in alphaherpesviruses are necessary for the viral anterograde spread from the presynaptic to postsynaptic neurons. The BHV-5 Us9 gene sequence was determined, and the predicted amino acid sequence of BHV-5 Us9 was compared with the corresponding Us9 sequences of BHV-1.1. Alignment results showed that they share 77% identity and 83% similarity. BHV-5 Us9 peptide-specific antibody recognized a doublet of 17- and 19-kDa protein bands in BHV-5-infected cell lysates and in purified virions. To determine the role of the BHV-5 Us9 gene in BHV-5 neuropathogenesis, a BHV-5 Us9 deletion recombinant was generated and its neurovirulence and neuroinvasive properties were compared with those of a Us9 rescue mutant of BHV-5 in a rabbit model. Following intranasal infection, the Us9 rescue mutant of BHV-5 displayed a wild-type level of neurovirulence and neural spread in the olfactory pathway, but the Us9 deletion mutant of BHV-5 was virtually avirulent and failed to invade the CNS. In the olfactory mucosa containing the olfactory receptor neurons, the Us9 deletion mutant virus replicated with an efficiency similar to that of the Us9 rescue mutant of BHV-5. However, the Us9 deletion mutant virus was not transported to the bulb. Confocal microscopy of the olfactory epithelium detected similar amounts of virus-specific antigens in the cell bodies of olfactory receptor neuron for both the viruses, but only the Us9 rescue mutant viral proteins were detected in the processes of the olfactory receptor neurons. When injected directly into the bulb, both viruses were equally neurovirulent, and they were transported retrogradely to areas connected to the bulb. Taken together, these results indicate that Us9 is essential for the anterograde spread of the virus from the olfactory mucosa to the bulb.
Subject(s)
Herpesvirus 5, Bovine/pathogenicity , Lipoproteins/metabolism , Phosphoproteins/metabolism , Amino Acid Sequence , Animals , Base Sequence , Cattle , Encephalitis, Viral/physiopathology , Encephalitis, Viral/virology , Herpesviridae Infections/physiopathology , Herpesviridae Infections/virology , Herpesvirus 5, Bovine/genetics , Herpesvirus 5, Bovine/metabolism , Lipoproteins/chemistry , Lipoproteins/genetics , Meningoencephalitis/physiopathology , Meningoencephalitis/virology , Molecular Sequence Data , Olfactory Bulb/virology , Phosphoproteins/chemistry , Phosphoproteins/genetics , Rabbits , Sequence Analysis, DNA , VirulenceABSTRACT
Organ cultures were prepared from various levels of intestine and kidney of 2 to 4-week old specific-pathogen-free chickens, and their susceptibility to ten strains of infectious bronchitis virus isolated from the chicken intestine and the Massachusetts strain M41 was investigated. The ability of a virus to grow depended on the strain of virus and size of the inoculum. While proventriculus, bursa and kidney were found to be universally susceptible to all viruses tested, some strains did not grow in caecal tonsils or rectum. Strain M41 showed little difference in pattern of tissue replication compared with several other strains isolated from the gut and actually grew in a wider range than some. Duodenum, jejunum and ileum were found to be non-permissive to all strains tested, even after a high input inoculum.
ABSTRACT
Following inoculation of day-old chicks with Moroccan strain 'G' of infectious bronchitis virus (IBV) which has a predilection for the gut, virus was recovered from the trachea up to day 7 and from the cloaca up to day 35. After this no virus could be detected, even following the natural stress of re-housing with unfamiliar birds at 9 weeks. When the birds were 12.5 weeks old, they were injected with cyclosporin, a selective T-cell suppressor. Four of the five birds re-excreted virus very erratically, as did two of five contacts. This was accompanied by the appearance of IBV-specific IgM in the sera of both groups. The results suggest that in long-term infections with IBV, virus persistence is controlled by T lymphocytes.
ABSTRACT
A method is described for the simple application of immunofluorescence (IF) staining for the identification of infectious bronchitis virus (IBV) in tracheal organ cultures (TOC). It involves the application of antiserum and fluorescent antiglobulin to unfixed TOC. In TOC inoculated with high titres of virus, specific fluorescence was observed in less than 24 h. IF staining almost always occurred before ciliostasis. Following experimental infection of chicks with IBV, virus could sometimes be detected in material from tracheal or cloacal swabs within 24 h of inoculation of TOC.
