Viral Infections, Oncoviruses & Antiviral Chemotherapy Flashcards
What is detailed in viral pathogenesis?
*process for a virus producing a disease
1. infect their specific hosts cells
2. replicate efficiently within host
3. damage targeted tissues
4. overcome immune system
What is the persistence or clearance + clinical outcomes of viral pathogenesis?
persistence or clearance:
- acute, chronic, latent, or persistent
clinical outcomes:
- asymptomatic, mild, severe
What are the signs and symptoms of an inapparent/ asymptomatic infection?
signs: objective, measurable indicators observed by clinician/ pharmacist (fever, rash)
symptoms: subjective experiences apparent to the patient (e.g pain, fatigue)
What are the properties of an acute infection?
- short incubation periods upon virus entry
- rapid onset disease
- brief period of symptoms (days to 1 week)
- often self limiting with a quick resolution by immunity
What are the properties of a latent viral infection?
*viruses persists for long periods (or lifelong =) in the hot without active replication
* evades immune detection by hiding in cells
* no symptoms, but reactivation can occur (triggered by different factors)
- common in herpesviruses (HSV, VZV,EBV)
What are the properties of persistent/ chronic viral infections?
*long term viral presence
*continuos or intermittent viral replication
- can be symptomatic or asymptomatic for extended periods
What are the details of Herpesvirus and latency?
- Establishes lifelong infection with periods of dormancy and reactivation
- Viral genome persists in host cells without active replication
- Latency sites vary by virus type
- No viral particles produced during latency, preventing immune detection
ANY VIRAL LATENCY IS IRREVERSIBLE AND CANNOT BE CURED OR REVERTED!
What is the latency establishment for HSV & VZV?
*primary infection occurs in epithelial cells, causing acute symptoms
- cold sore for HSV-1
- chicken pox for VZV
* viruses enter sensory neuron’s and travel to sensory ganglia
* viral genome persists (as circular DNA) in the neurones nucleus → latency
* during latency, no viral particles or symptoms produced
What is the reactivation of herpesvirus?
*triggered by stress, immunosuppression, uv exposure, fever or trauma
*immune system responds to controls the outbreak but cannot eliminate latency.
What are oncoviruses?
- Oncoviruses are viruses linked to cancer development
- virus induced cancers are not contagious
- most oncoviruses integrate their genomes into host DNA, triggering tumour formation
What are the mechanisms of viral induced cancer?
- Encode viral oncogenes promoting uncontrolled cell divisions
Induce conversion of cellular proto-oncogenes (normal) to
unregulated oncogenes (always active)
Inactivate tumour suppressor genes - Inactivate apoptosis
*loss of checkpoint control leading to unregulated cell cycle progression - unsustained cell proliferation - continuous cell divisions without regulation
- genetic chromosome instability
What are some virus cultivation methods?
*animal models
* embryonated eggs (e.g influenza vaccine production)
* continuous cell cultures will indefinitely ability to divide in vitro
What is the viral quantification technique (viral plaque)?
- cells are grown in plates, infected with viruses
- agar or reagent overlay restricts virus spread, confining infection to neighbouring cells
- infected cells lyse, forming localised plaques over time
- dye staining highlights plaques, distinguishing dead cells from viable ones
- each plaque originates from a single infectious virus, measured as plaque forming units (PFU)
What are the vaccination principles only?
*primary method to prevent viral diseases or severe cases
* induce immune protection by targeting an external & immunogenic portion of the virus
* use various technologies
* used to eradicate smallpox and it has nearly eradicated poliovirus
What are the principles of antiviral drugs to treat specific viral infections?
Interfere selectively with viral replication, being effective with minimal impact on host
cell activity, ensuring viability and safety
Inhibit essential steps of the viral life cycle, preventing replication and spread of the virus
To treat infections caused by specific virus
No universal antiviral drugs are available
What are the details of HIV?
Retroviridae family
two subtypes: HIV-1 and HIV-2.
HIV-1 is more virulent and more infective.
Viruses that insert a copy of its RNA genome into the host cell’s genome (lifespan chronic infection).
What does HIV cause and how does it make the body vulnerable for cancers?
HIV causes acquired immunodeficiency syndrome (AIDS),
resulting in the progressive failure of the immune system.
A decrease in CD4+ T-lymphocyte count makes the body vulnerable to life-threatening opportunistic infections (e.g., Cryptococcus) and cancers (e.g., oncovirus).
What are the 3 stages of HIV progression?
*acute
*chronic
*AIDS
if not treated the median time from infection to AIDS is 8-10 years. HIV infection needs to be treated
What does acute HIV entail?
flu like symptoms that occur days to weeks after contracting HIV
What does Chronic HIV entail?
the latent and asymptomatic stage that can last several years
What does AIDS entail?
occurs when CD4 cell count falls below 200 cell/mm3. This makes people vulnerable to opportunistic infections and AIDS-defining conditions.
What is HAART/cART?
*highly active antiretroviral therapy, composed of two/three anti-HIV drugs
THIS does NOT cure HIV due to latency.
- prevents transmission
- reduces mortality and morbidity
- prevent or reduce drug resistance
- reduce viral RNA to an undetectable level
