Mechanisms of Viral Infection Flashcards
acute infection
rapid onset –> cytolysis –> resolution –> clearance
systemic signs of fever or low temperature, lethargy, nausea, vomiting, anorexia
SELF LIMITING - host will clear virus by producing neutralizing antibodies
persistent infections
primary infection that is not cleared by the immune system
- causes lifelong, chronic infections with varied level of disease
- often asymptomatic +/- shedding
- can have episodic pathogenicity associated with shedding
what is the challenge with persistent infections
diagnostics are difficult
- detection of the virus may or may not mean that is it causing disease
significance of detecting virus depends on zoonotic potential and likelihood of it causing the disease (ex. Giardia in an animal shelter)
latent infections
subset of persistent disease; lifelong infection with episodic disease
latency = the phase of the viral cycle in which, after initial infection, full genome replication and proliferation of virions ceases
can be clinical disease with or without shedding
can be shedding with or without clinical disease
chronic infections
subset of persistent disease; disease may be present for an extended period of time
virome
host adapted, endogenous viruses
fragments of endogenous viruses have integrated into our genome and exist
host factors that influence viral infection
- age
- genetics
- immunosuppression
- drugs causing immunosuppression
feline herpesvirus 1 (FHV-1)
upper respiratory tract infection in cats
- enters in cuts in oral mucosa
- enters into peripheral nerves
- retrograde transport to trigeminal-facial ganglion and becomes latent
- does NOT produce virions in this stage
- drugs/vaccines unable to cure latent infections - stress induces recrudescence of virus
- anterograde transport back down peripheral nerve to site of infection
- begins replicating
- forms active lesions of FHV-1
- sheds in respiratory tract
what are the lesions of FHV-1
lysis and ulcers of nasal epithelium
what causes clinical manifestation of acute FHV-1
recrudescence of a latent infection caused by stress
unable to know where the primary infection came from
what can happen if URT infection becomes chronic
turbinate destruction and tissue remodeling which will increase susceptibility to secondary infections
FHV-1 diagnostics
- PCR - nasal/pharyngeal swab
- viral isolation - nasal/pharyngeal swab
can NOT do PCR on blood because not viremic
can NOT do serology because antibodies can indicate infection or vaccination
papillomavirus
persistent infection
exists as naked double stranded DNA in the nucleus of some epithelial cells in the basal layer of epithelium
basal layer = stems cells that actively proliferate
- viral replication matches epithelial cell turnover
- once top layer of cells sloughs off –> virus dies
is papillomavirus a problem in health
NO because it exists in cells that have quick turnover and rapidly die anyway
how can papillomavirus cause disease
occurs in young and immunosuppressed animals
can increase mitotic rate and decrease apoptosis of cells
- if host unable to mount appropriate immune response –> causes HYPERPLASIA
- can eventually lead to NEOPLASIA if hyperplasia becomes chronic
