Virus-Host Interaction & Pathogenesis Flashcards
Susceptibility factors maintaining viral diseases:
* _________ of viral virulence
* _________ of viral virulence
* Determination of host ________
* Factors affecting virus/host ______/______
Assessment, Determination, susceptibility, resistance, susceptibility
Mechanisms of viral infections and viral dissemination
* Routes of viral ____
* Host ______ and tissue _____
* Methods of viral _______/_____ inside the host
entry, specificity, tropism, dissemination, spread
Mechanisms of viral spread and infection of target organs
* Types of virus-cell ______
* Virus mediated tissue organ _____
interactions, injury
Virus induced tumour
- RNA viruses induced oncogenesis
- DNA viruses induced oncogenesis
Viral pathogenesis is defined as the process by which a viral infection leads to _____.
disease
The outcomes of the viral infections depends on the interplay between some ____ and ____ factors
viral, host
Factors affecting viral pathogenesis:
1. Effects of viral infections on ____ (?)
2. Entry into the ____
3. _____ of the infection ( _____ replication, _____ spread & ______ replication).
-Cell/tissue _____
-Cell/tissue _____
- _____ immune response
-Virus _______ or ______
cells, Cellular Pathogenesis, Host, Course, primary, secondary, tropism, damage, host, clearance, persistence
Virulent virus: relevant term to measure the ability of the virus to ______ ______ in a particular host
induce disease
Factors affecting the viral virulence:
-Ability of he virus to ____ and ____ in a particular host
- Virus must have the ability to ____ the host
-Virus has the ability to ____ the host immune response
- Virus is able to cause ______ in the target host
grow, multiply, invade, evade, damage
Viral virulence is based on some viral/host related factors
- Age, gender, immune status
-Virus concentration
Permissive cells are cells that ?
support viral replication (receptors, co/receptors, transcription, translation
factors)
Non-permissive cells are defined as ?
cells in which viral infection can not be established
Mechanisms of viral induced diseases in the affected host
Steps of viral replication in the host
Essential steps in the viral
infections/requirement for viral
survival and progression of infection
Types of viral infections - Productive
Productive
-Virus introduced its
genome into the cells
-New viral progeny
are made
Types of viral infections - Latent
-Viral genome is
incorporated into the
host cell genome
-Production of
infectious virus does not
occur immediately
Productive infection
occur latter on
Types of viral infections - Abortive
Virus initiated the
infection
- No viral progeny
produced
Types of viral infections - Persistent
Long term viral infection
when the immune system
failed to clear acute viral
infection
Recrudescence: a new outbreak after a period of ______ or ______.
abatement, inactivity
Types of viral infections with reference to viral load and timeline
Recurrent: repeated cycle of viral infection. Recover a little bit, then feel sick again b/c you do not have complete clearance.
Types of viral infections - Lytic infection
Destruction of cells at greater
rates than they may be
replaced
Ex: Pseudorabies virus: CNS cells
Ex: ICHV: liver cells
Types of viral infections - Latent infection
-Viral genome incorporated into
the host cell genome with no
synthesis of viral proteins until
animals exposed to stress
conditions thus the viral
replication will be activated
Ex: Herpesvirus infection in
neurons and ganglions
Ex-2: Reovirus in lymphocytes
Types of viral infections - Persistent infecton
-BVDV: Intrauterine infection
of foetus during mid stage of
pregnancy results in immune
tolerant calves
-Calves shed the virus either
continuously or intermittently
acting as source of infection to
other animals
Types of viral infections - Immune complex disease
-EIAV: Abs may cause
immunopathologic conditions
Abs combines with virus to
cause immune complex
deposited in the glomeruli in
the kidney and in organs
causing inflammation
Shedding of the virus and the occurrence of the clinical signs in acute-self limiting
infections in various kinds of persistent
infection
Typical curve of acute viral infection
Entry of virus
Incubation period = no clinical signs
Patterns of viral infection
* Acute infection followed by viral _____
* Acute infection but ‘______’ tissue infected with ______ damage despite viral clearance
* ______ infection: latent, slow, transforming
* ____ incubations
clearance, accidental, permanent, Persistent, Long
Ex: Influenza virus, Rhinovirus, Rotavirus, Coronavirus
Patterns of viral infection
Patterns of viral infection
Viral persistence is defined as?
Viral persistence: the inability of the immune system to clear an acute viral infection
Causes of viral persistence
-Immunodeficiency due to HIV infection
-Transplant
-Chemotherapy
-Genetic conditions
-Congenital infections (BVDV)
Outcomes of the persistent viral infections
- No apparent effects (Polyomavirus, Herpesvirus)
-Chronic or progressive infections (measles, chronic hepatitis)
-Cancer
-Clinical reactivation (Genital herpesvirus infection)
Significance of persistent infections
Maintenance of virus in animal population
Mechanisms of viral persistence
Viral evasion to the host innate immune response
* Modulation of the adaptive immune system
* Induction of latency
* Infection of tissues not readily accessible to the immune system such as keratinocytes
* Immune response escape mutants: HBCV, HIV
* Prolonged survival of the infected cell (oncogene)
Mechanism of Herpesvirus reactivation
Routes of viral infection - Respiratory tract
-Inhalation of droplet nuclei of 1-10
cause infection
-1-3 um droplets penetrates into
bronchioles
-Resp tract defense
Mucociliary clearance
Phagocytosis by alveolar macrophages
in lung
-Influenza virus produce
neuraminidase liquefy mucous
Routes of viral infection - Skin
-Intact skin act as impermeable
barrier against viruses but can be
breached by
-insect bites (BTV, EEEV)
-Animal bites (Rabies)
-Contaminated instruments (EIAV)
Routes of viral infection - Genital tract
-Venereal infection is rare in animals
-BHV-1 transmitted by venereal routes
EHV-3 causes coital exanthema in
horses
Routes of viral infection - alimentary tract
-Virus ingested with food and water or
licking contaminated objects
-Low pH of stomach and high pH of
intestine inactivates some viruses
-Digestive tract protected by layer of
mucous
-Peristaltic action helps to remove
viruses
Routes of viral infection - Placenta
-Viremia in pregnant female the virus
may cross the placenta and infect foetus
-Killed foetus resulted in
A- infertility
B-Mummified foetus
C-Abortion
D- Stillbirth
-Survived foetus may be congenital
anomalies
Routes of viral infection - genital tract
-Venereal infection is rare in animals
-BHV-1 transmitted by venereal routes
EHV-3 causes coital exanthema in
horses
Routes of viral infection - conjunctiva
IBRV conjunctival form
Viral entry/spread- through respiratory epithelium
Respiratory tract: the respiratory tract and all other mucosal surfaces possess sophisticated
immune defense mechanisms, as well as non-specific inhibitory mechanisms
(ciliated epithelium, mucus secretion, lower temperature) which viruses must overcome
Respiratory tract is protected by
Respiratory tract is protected by
1- The mucous blanket
2-The beating of the ciliated epithelium
Influenza
* IBRV (Infectious bovine rhinotracheitis)
* Common Cold (Rhino, Adeno, Corona) viruses
* Parainfluenza Virus
* Respiratory syncytial virus (RSV)
SEM pictures of
Rhinovirus infection
in trachea
A: Normal trachea showing the ‘’carpet’’
* B: Trachea of Rhinovirus infection: only
some tufts of the epithelium are showing
(loss of the carpet appearance
Pathogenesis of ectromelia (mousepox) virus
Pathogenesis of ectromelia (mousepox) virus
Viral invasion to the sub-epithelial layers and lymphatic spread
Virus damages epithelial linining to ente rlymphatic vessels –> lymph nodes –> blood stream
Droplet infection: an infection transmitted
from one individual to another by droplets
of moisture expelled from the ______ _______ ____ through ______ or _____
upper respiratory tract, sneezing, coughing
Aerosol: Aerosol Transmissible Diseases
Aerosol transmissible diseases (ATDs), such as _____, are transmitted by infectious ______ or ______ through ______ or _____ contact with ______ membranes in the ______ tract or ____
measles, particles, droplets, inhalation, direct, mucous, respiratory, eyes
- Fomite: or environmental surfaces
- (1) Clinical contact surfaces such as dental
units, x-ray machines, equipment knobs, etc - (2) Housekeeping surfaces