Chapter 7 Flashcards
What do viruses need to reproduce
A host cell
Virus structure
Viral genome - genetic material
Nucleocapsid - casing for genes
Envelope - outer casing
Tissue damage is caused by viruses during the course of their…
Reproduction
Steps of virus reproduction
Absorption
Penetration
Reproduction
Viral absorption
Step 1 in virus reproduction
Contact and adherence to a host cell
Determines viral tropism
Cells depends on surface receptors
Viral penetration
Step 2 in reproduction of viruses
Passage through membrane
Then, 3 steps happen
- endocytosis - formation of vesicles that release genome into cell
- fusion of virus with cell membrane
Adherence and translocation to the host nucleus
Lysogenic cycle
Viral genome is inserted into the host genome
- each time cell replicates, the viral genome is passed on
- remains latent until permissive conditions occur for disease
Lytic cycle
Viruses in which the cell is directed to produce new viral capsid proteins and copy the viral genome
New viruses are then assembled in cytoplasm and either bud out or erupt from the cell all at once
Lysogenic vs lytic cycles
Lysogenic
- viral genome is in cell
- viral DNA passed down when cell replicated
- viral infection will occur under optimal conditions
Lytic
- host cell is forced to make new viruses in it
- viruses either leave the cell via budding or explode out all at once
Budding
Damage caused to the host cell via virus particles leaving the cell
- disrupt membrane, causing leakage and osmotic shock often killing the cell
Enveloped viruses
Those that retain a piece of cell membrane from the host cell membrane
Most viral infections are limited to a…. (2)
Particular host and tissue type
Cytopathic effects of viruses
Cell swelling and changes in morphology due to eruption of viral particles
Cellular effects of viruses that insert DNA into the nucleus
Mutation leading to abnormal cell division changes including aphasia or hyperplasia
Clinical manifestations during the first few days of viral infection
Fever, myalgia, fatigue, rash, respiratory issues
Result of innate defence activation and release of inflammatory mediators
What causes clinical manifestations of viral disease
Cell injury drug in adsorption, reproduction, and release
Examples of oncogenic viruses
Hep B and Hep C
Initial defence against viral attack
Innate immunity
Macrophages and dendritic cells, inflammatory mediators
After initial response to viral attack, …
Adaptive immunity creates antibodies and promotes cytotoxicity in infected host cells causing apoptosis
Mediated by CD8+ cells
Infections caused by DNA viruses (6, 3 enveloped and 3 non enveloped)
Enveloped
- pox viruses
- herpesvirus
- hepadnaviruses
Non enveloped
- adenoviruses
- papovaviruses
- parcocriuses
Poxviruses
Enveloped DNA virus
Causes skin pustules
- smallpox (variola virus)
- human reservoir only
Herpesviruses (family + general facts about Them all)
Enveloped DNA viruses
Family of over 100 viruses
- herpes simplex 1 and 2
- Epstein-Barr virus
- human herpes 6 7 and 8
- cytomegalovirus
Establish latent and recurrent infection
- human reservoir
- some sensitive to antivirals
- some untreatable
- general minor infections but can be dangerous in immmunosuppressed people
- ## transmitted from mucosa or skin contact, or respiratory
Herpes simplex 1 and 2 (HSV1/2)
Herpesvirus family (DNA enveloped)
Transmitted via mucus and skin
- cause of cold sores
- genital sores (HSV 2 mainly)
- enter through sensory nerve endings where they are latent, emerging when triggered
- triggers - fatigue, infection, X-rays, surgery, immunosupression, stress)
Varicella Zoster virus (VZV)
Herpesvirus family (DNA enveloped)
- cause of chickenpox and shingles
CP
- contagious, passed via respiratory, saliva, or pustule contact (vertically too)
- children are susceptible
Shingles
- recurrence of VZV later in life after initial stage
- painful rash and blisters
-
- heals in 2-4 weeks
- activated by immunosupression, X-rays, etc
Cytomegalovirus (CMV)
Herpesvirus family (DNA enveloped)
- 40-100% of people carry it
- transmitted in saliva, resp mucus, milk, urine, semen
- newborns/immunosupressed people are at risk of clinical manifestations
- mental retardation, vision/hearing loss
- common opportunistic infection in AIDS patients
Epstein Barr virus (EBV)
Herpesvirus family (DNA enveloped)
- found everywhere in humans in lymphoid tissue and salivary glands
- causes mono
Hepadnaviruses
Found in humans birds n apes
Most important one = Hep B
Hepatitis B
Hepadnavirus (DNA enveloped)
- transmitted in blood, semen, vag stuff
- target hepatocytes
- most commonly transported in childbirth
- very resilient
- can cause liver cirrhosis, hepatocellualr carcinoma, liver failure
- high risk groups - gay men, needle users
Pathophysiology of hep B
Proliferation of virus in the liver
- leads to loss of liver function (metabolism, toxin degradation, etc)
- symptoms = malaise, nausea, dark urine, jaundice
Adenoviruses
non enveloped DNA virus
- transmitted via secretions, airborne, fomites
- infect respiratory and intestinal epithelia and conjunctiva
- Lysogenic
- infections common in children
Papovaviruses
Non enveloped DNA virus
- HPV (cause of warts) (more than 100 types)
- HPV 16/18 cause 70% of cervical cancer
- transmitted through sexual contact
Otrhomyxoviruses: influenza viruses
4 types of influenza viruses
ABC and D
- only A and B are important in humans
- has lipoprotein envelop and glycoprotein spikes
Classification of influenza viruse A
Hemagglutinin (1-16) and neuraminadase (1-9)
HxNx
May also include host of origin (duck, pig, etc)
Influenza B is not divided into subtypes
Influenza transmission
Via aerosols and fomites
- virus binds ciliated epithelial cells when it buds and it shed
Key trait of influenza viruses
Rapid evolution leading to variability
- namely influenza A
Point mutations lead to slight changes in surface proteins
- antigen drift
Antigen drift
Slight changes in a virus of proteins or structure
Antigen shift
More rapidly occurring change that involves exchange of genome segments
Occurs when two types of influenza A strains, leading to new hybrids
Paramyxoviruses
Include marbilloviruses, mumps, and respiratory syncytial virus
- transmitted to resp tract
- unstable outside human body
- inactivated by heat, light, solvents, and acidic conditions
Morbillovirus
RNA virus
Measles
Paramyxovirus
Mumps virus (MuV)
Causes mumps (RNA)
- paramyxovirus
- spread via resp droplets
Rhabdoviruses
Rabies, polio, hep A
Rabies
Rhabdovirus (RNA)
Zoonotic
- transmitted via saliva, and droplets
- multiplies at puncture site (bite), and migrates to CNS, then goes to salivary glands
Poliovirus
Rhabdovirus
Cause of poliomyelitis
RNA virus
-transmits via fecal oral route
Hep A virus
Rhabdovirus (RNA)
- first hepatic virus identified
- transmits via fecal oral route
Resilient
- most cases subclinical
- causes liver inflammation, jaundice, dark urine, etc
Coronaviruses
SARS-CoV, MERS-CoV, SARS-CoV-2
Coronaviruses are…
RNA Viruses
- transmitted via resp droplets
- many sub clinical
HIV (what is it?)
Human immunodeficiency virus
Enveloped single stranded RNA virus with reverse transcriptase (retrovirus)
HIV is spread by
Direct transfer of virally infected bodily fluids
Virus enters dendritic cells and proliferates in them, then targets CD4 cells
- due to reverse transcriptase, HIV causes lytic infection
May remain latent for 15 years, once CD4 cell count is low enough AIDS starts
Animal virus replication
Adsorption
Penetration
Duplication
Assembly
Release
Teratogenic meaning
Cross the placenta and cause disturbances in fetus
Herpes simplex type 1 manifestations (3)
Herpes labialis
- lips
- blisters
Herpatic gingivostomatitis
- swollen nodes, fever etc
Herpetic keratitis
- ocular inflammation
Herpes simplex type 2 manifestations
Genital herpes
Burkitt lymphoma
B cell malignancy
- develops in cheek or jaw
HPV manifestations
Warts
Kopliks spots
Oral lesions that occur during measles infection
Respiratory syncytial virus (RSV)
Also called pneumovirus
Fever, rhinitis, wheezing, otitis, croup
Treatment: synagis (antibody), or ribavirin
Rubella virus type
Togavirus
Rubella
SsRNA with loose envelop
Transmitted via resp aerosol
- postnatal rubella (malaise, fever, rash)
- congenital rubella (in 1st trimester, causes abnormalities)
Hep C transmission
Transmitted via blood contact
Arboviruses
Viruses spread by arthropod vectors like toga viruses
Most of these cause fever n stuff, some are much worse
Hemorrhagic arbovirus fevers (2)
Yellow fever
Dengue fever
Primary effects of HIV infection
- extreme leukopenia
- formation of giant T cells
- infected macrophages release the virus (lytic)
Secondary effect of HIV
Destruction of CD4 cells
Poliomyelitis
Polio virus
Transmitted via fecal oral route
If it persists, it will transmit to spinal cord and brain (muscle spasms, meningitis, hypersensitivity)
Flaccid paralysis
