Day 3.1.2 Flashcards
How much iron does the human body contain?
4-5 grams
What is quantitatively the most important trace element?
Iron
What are the two major ways in which iron is present in the body?
- Protein-bound in blood
2. Intercellular iron-protein complexes
What is the only form of iron that can be absorbed by the bowel?
Bivalent
What % of the total amount of iron is found in heme proteins?
75%
What are the heme proteins responsible for binding the majority of the iron in blood?
Hemoglobin
Myoglobin
What are the intercellular iron-protein complexes responsible for storing iron?
Ferritin
Hemosiderin
Apart from blood, where is iron stored in the body?
Liver
Spleen
Bone marrow
What is Hemosiderin composed of?
A complex of
- Ferritin
- Denatured ferritin
- Other proteins
What part of the GIT is responsible for the absorption of iron?
Upper part of small intestine - mainly duodenum
What way is iron transported in the blood?
As part of transferrin
What are the formative components of transferrin?
Apotransferrin
Ferrous iron
What type of protein is apotransferrin?
Beta globulin
What kind of binding does iron have in transferrin?
Loose
Where is the majority of excess iron stored in the body?
Liver - 60%
What is storage iron?
Iron stored in ferritin
What promptes iron uptake?
Reducing agents like ascorbate (vitamin C)
Why is iron uptake increased by reduce agents in blood?
Because iron is only absorbed in bivalent form
What is the dominant factor controlling absorption of iron from the GI tract?
Saturation of the mucosal cells with iron - this is controlled by the rate at which the transferrin complex can exit the epithelial complex into the vascular system
Hemochromatosis
Iron storage disease
Characteristic signs of hemochromatosis
Bronzing of skin
Diabetes
Weakness
What is the pathophysiology of hemochromatosis?
Inability to store iron results in the deposition of iron-containing pigments in peripheral tissues
What is bilirubin
A product of heme degradation
What blood type is the universal donor?
O
Why is type O the universal donor?
Type O people do not produce AB antigens
What blood type is the universal recipient?
AB
Why is type AB the universal recipient?
They do not make any AB antibodies so they do not discriminate against any other OAB blood type
What kind of bonds does oxygenate to bind with hemoglobin?
It honda loosely with one or the so called coordination bonds of the iron atom
How is the gaseous tension of oxygen in peripheral tissue capillaries compared to in the lungs?
Much lower
How many states does hemoglobin exist in?
Two conformational states -
T - tense
R - relaxed
Which state of hemoglobin has stronger affinity for oxygen?
R conformation
What is the difference in affinities to oxygen of the two forms of Hb?
R conformation of Hb has a 150-300 fold increase of oxygen affinity over the T conformation of Hb
Where do you find the T conformation of Hb?
Peripheral capillaries
Where do you find the R conformation of Hb?
Lungs
What determines whether Hb binds with or releases O2?
Oxygen partial pressure (PO2)
What is the relationship of PO2 with affinity of Hb for oxygen?
Directly proportional
Where is po2 high?
Pulmonary capillaries
Where is po2 low?
Tissue capillaries
What does the oxyhemoglobin dissociation curve illustrate?
The relationship between PO2 in the blood and the number of O2 molecules bound to Hb
What does a shift of the oxyhemoglobin curve to the right indicate?
Decreased affinity of Hb for O2
Enhanced O2 dissociation
What is p50?
The point on the oxyhemoglobin dissociation curve where 50% of Hb is saturated with O2
What is p50 in normal adults?
27mm Hg
What does a shift of the oxyhemoglobin dissociation curve to the right do to p50?
Increases the p50
What does increase in CO2 do to the oxyhemoglobin dissociation curve?
Shifts it to the right
Factors that shift oxyhemoglobin dissociation curve to right
Increased hydrogen ions (decreased pH)
Increased temperature
Increased BPG (2,3 - biphosphoglycerate)
Increased CO2
According to genome, what are the two major types of viruses?
ssRNA
dsDNA
What are the families of viruses that have the dsDNA genome?
- Herpesvirus
- Adenovirus
- Hepadnavirus
What are the families of viruses that contain the ssRNA genome?
- Paramyxovirus
- Picornavirus
- Flavivirus
- Deltavirus
- Calcivirus
- Orthomyxovirus
- Togavirus
- Retrovirus
What kind of genome does paramyxovirus have?
SsRNA
What kind of genome does herpesvirus family have?
DsDNA
What is the only dsDNA virus that doesn’t have “d” in its name?
Herpesvirus
What kind of genome do the viruses that cause hepatitis have?
All but one (hepatitis B) have ssRNA genome
What family do the Hepatitis viruses belong to?
All of them belong to different families
A - Picornavirus B - Hepadnavirus C - Flavivirus D - Deltavirus E - Calicivirus
What is the most common cause of gastroenteritis in children 2 and under?
Rotaviruses
What is the structure of reoviruses?
They have an icosahedral capsid composed of an outer and inner protein shell containing a double stranded segmented genome
What is the envelope of reoviruses composed of?
Reoviruses are non-enveloped
What kind of nuclear material is contained in reoviruses?
dsRNA
Where do reoviruses replicate?
In cytoplasm of human cells
Can reoviruses replicate using human enzymes?
No - the virion contains an RNA dependent RNA polymerase
What is the gastroenteritis virus type B?
Rotaviruses
How is rotavirus spread?
Fecal oral route
What age groups does rotavirus affect?
Most potent in children under 2
They can affect adults but symptoms are mild or absent
From where are Rotaviruses absorbed into the system?
Small intestine
What is the cause of Colorado tick fever?
Coltivirus (Colorado tick fever virus)
24 hour flu, aka
Viral gastroenteritis
Intestinal flu, aka
Viral gastroenteritis
How long does it take to recover from viral gastroenteritis?
12-24 hours
What kind of virus causes the intestinal flu?
RNA viruses - NOT influenza virus
How is viral gastroenteritis diagnosed?
ELISA on fecal samples
Characteristic signs of viral gastroenteritis
Vomiting
Low grade fever
Diarrhea
Metabolic consequences of water and electrolyte loss
What is a major concern in viral gastroenteritis?
Dehydration
Can viral gastroenteritis be fatal?
Yes in infants
Name the RNA non-enveloped virus families
Picornavirus
Reovirus
Calicivirus
What virus causes many respiratory infections in epidemics each winter?
Respiratory syncytial virus
What virus is a common cause of bronchiolitis in infants?
Respiratory syncytial virus
Name the envelope components in paramyxoviruses
Glycoproteins - hemagglutinin, neuraminidase
What viruses make up the paramyxovirus family?
Measles
Mumps
Parainfluenza
Respiratory syncytial virus
Which of the paramyxoviruses are enveloped?
Measles
Mumps
Parainfluenza virus
How is respiratory syncytial virus different from other paramyxoviruses?
It doesn’t have envelope glycoproteins
What does respiratory syncytial virus have instead of envelope glycoproteins?
Surface spikes - made of fusion (F) proteins
What do paramyxovirus spikes contain?
Hemagglutinin
Neuraminidase
Fusion protein
What do the fusion proteins in spikes of the paramyxoviruses do?
Cell fusion
Hemolysis
What is the name of the vaccine for respiratory syncytial virus?
There is no vaccine for respiratory syncytial virus
What gave rise to the name of respiratory syncytial virus?
The multinucleated giant cells formed due to fusion of infected cells because of virion surface proteins
Treatment of respiratory syncytial virus
Aerosolized Ribavirin (virazole) in severe cases
When is intervening treatment indicated in a respiratory syncytial virus infection?
Severe cases with underlying cardiac or respiratory disease
What is the reason for possibility of reinfection by RSV throughout life?
Antigenic drift
Conditions caused by parainfluenza viruses
Children -
Croup
Pneumonia
Adults - common cold
Croup
Acute laryngotracheobronchitis
What do the surface spikes on parainfluenza viruses consist of?
Hemagglutinin
Neuraminidase
Fusion proteins
How are parainfluenza viruses transmitted?
Respiratory droplets
Direct contact
How are conditions caused by parainfluenza viruses treated?
No antiviral therapy or vaccine is available
Which members of the paramyxovirus family cause viremia?
Measles
Mumps viruses
What is most characteristic of a viral pneumonia?
Interstitial pulmonary inflammation
What kind of nuclear material do paramyxoviruses have?
Ss negative RNA
Which ones are larger - Ortho or paramyxoviruses?
Paramyxoviruses
What is the difference between the genomes of para and orthomyxoviruses?
Paramyxoviruses have nonsegmented genomes
What is the hallmark of viral infection?
Cytoplasmic effect (CPE)
Chronology of events in cytopathic effect
Alterations of cell morphology
Marked derangement it cell function
Culminate in lysis and death of cells
List cytopathic changes
Necrosis Hypertrophy Giant cell formation Hypoplasia Metaplasia Altered shape Detachment from substrate Lysis Membrane fusion Altered membrane permeability Inclusion bodies Apoptosis
What is the use of knowing cytologic changes?
They provide useful presumptive evidence for diagnosis of the viruses that induce cytopathic changes
How do viruses gain entry into host cells?
They use specific cell surface receptors to bind to and subsequently gain entry
What does the use of specific cell surface receptors explain about viruses?
Cellular tropism of viruses
What family are Coxsackie viruses a part of
Picornavirus
What are the characteristics of picornavirus family
ssRNA
icosahedral capsid
no envelope
What are the differences between different herpesviruses?
They are all identical morphologically
What are the common characteristics of herpesviruses?
dsDNA
enveloped
nuclear membrane
icosahedral nucleocapsid
What is the major defining characteristic of herpesviruses?
They obtain their virion envelopes by budding from the host nuclear or golgi membrane instead of the host plasma membrane
Where do herpesviruses replicate?
In the nucleus of the host cell
What is the hallmark of all herpesvirus infections
the ability of the viruses to establish latent infections that persist for the life of the individual
Which herpesvirus remains latent in the trigeminal ganglion?
HSV-1
Where does HSV-2 most commonly remain dormant?
Sacral ganglia
Which virus remains latent in dorsal root and cranial nerve ganglia?
VZV - Varicella zoster virus
Where does CMV remain latent?
Nuclei of cells in the endothelium of the arterial wall and in T lymphocytes
Which virus remains latent in resting memory B lymphocytes?
EBV
Which of the herpesviruses cause a vesicular rash?
HSV 1, 2 and VZV
What Herpesviruses have oncogenic potential in humans?
EBV
HSV-8
What virus is associated with Burkitt’s lymphoma?
EBV
What cancers is EBV associated with in humans?
- Burkitt’s lymphoma
- Nasopharyngeal carcinoma
HSV - 8 aka
Kaposi’s sarcoma-associated herpesvirus
What virus is associated with Kaposi’s sarcoma?
HSV - 8
What kinds of Kaposi’s sarcoma are associated with HSV 8?
- Classical
- AIDS related
List of DNA Enveloped viruses
Herpesvirus
Posxvirus
Hepadnavirus
Prions
Most recently recognised
Simplest infectious agents
What is the molecular structure of a prion
a single protein molecule
What kind of nucleic acid do prions contain
None
What kind of genetic info do prions contain?
None
What disease do prions cause?
Creutzfeldt-Jakob disease
What disease is Creutzfeldt-Jakob disease associated with?
Mad Cow disease
How is Creutzfeldt-Jakob disease caused?
Ingestion of beef from a cow infected with mad cow disease
What is the speed of progression of Creutzfeldt Jakob disease in humans?
Slow
How does Creutzfeldt-Jakob disease manifest in humans?
It is a severe degenerative brain disease
How do prions propogate within a host?
They induce the conversion of endogenous prion protein PrP into a protease resistant isoform PrP to the power of Sc
How much inflammation do prions cause?
None
What kind of antibodies deal with prions?
None
What does treatment with formalin, heat, radiation do to prions?
It does not neutralise them, though it can reduce their infectivity
What are the major components of a virion?
Nucleic acids
Protein coat
Lipoprotein envelope
What is the capsid?
Protein coat of virions
What is a nucleocapsid?
Combination of nucleic acid and capsid
What does the presence of a lipoprotein envelope determine
Whether a nucleocapsid is naked or enveloped
What is the capsid composed of?
Polypeptide units called capsomers
What viruses are covered with spikes?
Orthomyxoviruses and paramyxoviruses
What is the difference between viruses and bacteria, fungi and parasites?
Viruses are not cells, cannot reproduce independently, don’t have a nucleus and do not have organelles.
Which is bigger, bacteria or viruses?
Bacteria
Which can be seen in a light microscope, fungi or viruses?
Fungi
Are viruses haploid or diploid?
Haploid, except the retrovirus family
Haploid
Contain a single copy of their genome
Which are the only diploid viruses?
Retrovirus family
Viroids
A single molecule of circular RNA without a protein coat or envelope
What diseases do viroids cause in humans?
None
How is HSV 2 spread?
Mainly through sexual contact
Can HSV 2 be spread from mother to newborn during childbirth?
yes
What kind of lesions does HSV 1 cause?
Labial lesions predominantly
Which HSVs cause manifestations of recurrent infection in otherwise healthy people?
HSV 1, 2
What does HSV 1 cause
Primary herptic gingivostomatitis
How is Primary herpetic gingivostomatitis caused?
Initial exposure to HSV 1
How is primary herpetic gingivostomatitis spread?
From person to person through oral secretions
What age group is generally affected by primary herpetic gingivostomatitis?
Children under 10
Manifestations of primary herpetic gingivostomatitis
Generally subclinical
- flu-like symptoms
- one or two mild sores in the mouth, generally unnoticed by the parents
What kinds of infections can HSV 1 cause?
Primary herpetic gingivostomatitis
Acute herpetic gingivostomatitis
Herpes labialis
Cold sore aka
Herpes labialis
Symptoms of acute herpetic gingivostomatitis
- fever
- irritability
- cervical lymphadenopathy
- fiery red gingival tissues
- small, yellowish vesicles which rupture and result in painful ulcers on free and attached mucosa
What disease shows fiery red gingival tissues in association with yellowish vesicles?
Acute herpetic gingivostomatitis
What disease manifests as painful ulcers on free and attached mucosa?
Acute herpetic gingivostomatitis
What is the most serious potential problem in a child with acute herpetic gingivostomatitis?
Dehydration
Why is there a risk of dehydration in a child with acute herpetic gingivostomatitis?
Due to the child not wanting to eat or drink because of the pain
What is adult recurrence of HSV 1 infection called?
Herpes labialis
Symptoms of herpes labialis
- localized parasthesia of the lip
- cold sore
Most common site of recurrence of HSV 1 in adults
Vermilion border of lips
What is the less common type of recurrent HSV 1 infection
Herpetic conjunctivitis
What herpes infection can be treated prophylactically by a vaccine?
VZV
What diseases does VZV produce?
- Varicella
- Herpes Zoster
Varicella aka
Chickenpox
Herpes zoster aka
Shingles
What is the primary infection of VZV?
Varicella
How does shingles occur?
Reactivation of a latent VZV infection (From the dorsal root and cranial nerve ganglia)
What is the vaccine used for VZV?
Live attenuated variella vaccine
Does VZV vaccine work in adults?
Vaccination of all adults over the age of 60 with a dose higher than that used for chickenpox prophylaxis in childhood reduces shingles-related morbidity and post-herpetic neuralgia
WHich one infects below the waist - HSV 1 or 2
HSV 2 - Genital lesions
Which one infects above the waist - HSV 1 or 2?
HSV 1 - eye and mouth lesions
What kind of HSV lesion can be a result of sexual activity?
Oral-genital activity - HSV 1 above the waist and HSV 2 below the waist
Complications of HSV 1 infection
- transfer to the eye
- acute encephalitis
- skin infections
What eye-related complications are caused by HSV 1?
- dendritic ulceration
- keratitis
What are the skin infections caused as complications of HSV 1 infection?
- herpetic whitlow
- erythema multiforme
How is HSV 1 infection diagnosed?
Tzanck preparation of vesicular fluid - shows multinucleated giant cells
Treatment of HSV 1 infection
Systemic antiviral drugs - acyclovir
- famciclovir
- valacyclovir
Can HSV 1 be completely treated?
No, antiviral therapy is suppressive or episodic
What is the effect of HSV 2 infection on pregnant women?
It can have serious consequences - the virus can be transmitted to the infant during vaginal delivery
What effect does HSV 2 have on infants?
Damage to nervous system and/or eyes
Temperate phage
A bacteriophage with the ability to form a stable, nondisruptive relationship within a bacterium
How does a temperate phage replicate?
An alternate method in which the phage genome is incorporated into the bacterial chromosome
How is a temperate phage different from a virulent phage?
It persists through many cell divisions of the bacterium without destroying the host
Bacteriophage
A virus that can only replicate within specific host bacterial cells
What is a bacteria that contains a temperate bacteriophage
Lysogenic bacterium
Example of a lysogenic bacterium
Corynebacterium diphtheriae
Lysogenic conversion
The alteration of a bacterium to a virulent strain by the transfer of a DNA temperate bacteriophage
What is the integrated viral DNA of a bacteriophage called?
Prophage
What is a phage that infects E coli bacteria called?
Enterobacteria phage T4
Plasmids
Extrachromosomal double stranded circular DNA molecules that are capable of replicating independently of the bacterial chromosome
Lysogenic cycle
Integration of virus into host genome without killing the host
Transduction
Transfer of DNA from a donor cell to a recipient cell with the DNA packaged witin a bacteriophage
Lytic cycle
Viral multiplication within a host cell leading to destruction
What does the nucleic acid core of a bacteriophage contain?
DNA or RNA
Is the core of a bacteriophage single or double stranded?
Either
Do bacteriophages have the same structure as a virion?
They have a protein coat and may be surrounded by lipid
How do bacteriophages infect bacterial host cells?
Some have a tail like structure through which they inject their nucleic acid into the bacterial host cell
Host cell
A cell within which a virus replicates
What does the virus do within a host cell
The viral genome achieves control of the cell’s metabolic activities
How does a virus replicate within a host cell?
It uses the metabolic capacity of the host cell to reproduce new viruses
How does the host cell die when a virus inhabits it?
The replication of the new viruses often causes death of the host cell
How many courses can bacteriophage infection take in a host cell?
Two - lysis or lysogeny
When is a virus said to be lytic?
When the infecting virus multiplies within the host cell and destroys it
What is a lytic virus also called?
Virulent
When is a virus said to be temperate?
When it does not replicate but rather integrates into the bacterial chromosome
What is a temperate virus also known as?
Lysogenic
Can a lytic phage be lysogenic and vice versa?
No and yes - a phage in a lysogenic cycle can spontaneously become lytic
Can a host cell be infected by other phages when already inhabited by an integrated virus?
Not similar phages
Prophage
An integrated virus in a host bacterial cell
Does lysogeny result in destruction of the host cell?
no
Transformation
Gene transfer resulting from the uptake by a recipient cell of naked DNA from a donor cell
What is the exchange of genetic material from one bacterial cell to another by close association called?
Conjugation
What structure does the bacterial chromosome or plasmid pass through during conjugation?
F pilus
What kind of nucleic material do retroviruses contain?
2 identical, single stranded positive sense RNA molecules
What is reverse transcriptase
An RNA directed DNA polymerase
Provirus
When reverse transcriptase forms viral DNA from viral RNA and incorporates it into host DNA
What does the creation of a provirus do?
It provides the template for viral RNA synthesis by host-derived mechanisms
How are retroviruses distinguished from other RNA viruses?
Their ability to replicate through a DNA intermediate using an enzyme reverse transcriptase
Human lymphotrophic retroviruses
- Lentivirus - HIV 1 and 2
- Oncovirus - HTLV 1 and 2
What do HIV viruses cause
AIDS
What is the cause of adult T cell leukemia
HTLV 1
What does HTLV 2 cause
Myelopathy
Where does transcription occur for RNA viruses?
Cytoplasm
What are the exceptions for transcription occurring in the cytoplasm for RNA viruses?
Retroviruses
Influenza viruses
What does transcription depend on in RNA viruses?
An RNA dependent RNA polymerase
What RNA virus does not depend on an RNA dependent RNA polymerase?
Retroviruses - RNA directed DNA polymerase - Reverse transcriptase
Where does transcription occur in DNA viruses?
Nucleus
Which DNA virus does not have transcription occuring in the nucleus
Poxviruses
What enzyme does transcription in DNA viruses involve?
A host cell DNA dependent RNA polymerase
Which type of viruses have transcription occurring in cytoplasm?
RNA viruses
What is the primary disease caused by EBV?
Infectious mononucleosis
What are the secondary diseases associated with EBV?
Burkitt’s lymphoma
B cell lymphoma
Hairy leukoplakia
Nasopharyngeal carcinoma
Diseases associated with CMV
Congenital infection - if the mother becomes infected with CMV during pregnancy
INfection in immunocompromised individuals
What cells do human adenoviruses prefer for replication?
Epithelial cells
What system are human adenoviruses unlikely to target?
Central nervous system
What kind of a genome do human adenoviruses have?
Double stranded linear DNA genome
What is the morphology of human adenoviruses?
Naked (non-enveloped), medium sized, composed of anicosahedral nucleocapsid
What are the spikes of adenoviruses made of?
Glycoproteinaceous projections that are hemagglutinin proteins
What do the spikes help do in adenoviruses?
They are involved in the adsorption or attachment of the virus to epithelial derivatives of the host
What kind of infections do adenoviruses cause?
Subclinical infections
How are adenovirus infections transmitted?
Droplets of respiratory or ocular secretions
What diseases are caused by adenoviruses?
Respiratory illnesses in children Conjunctivitis Gastrointestinal disease UTIs Pharyngitis
What is the capsid composed of in a virus?
Repeating protein subunits
What are protomers?
Repeating protein subunits that form capsids
What part of the virus protects the viral genome?
Capsid
What does the capsid protect the viral genome from?
Proteases
What imparts structural symmetry to the virion?
Capsid
What kinds of structural symmetry does the virion have?
2 -
- icosahedral
- helical
What role does the capsid play in infectivity of the virion?
It is essential for the infectivity
What role does the capsid play in naked viruses?
Attachment protein that binds to the host cell receptor
How do hosts react to the capsid?
Capsid is antigenic and provokes host immune response
How many capsids to viruses have?
One - the only exception is retroviridae - two capsids
Matrix protein
Welds the capsid or nucleocapsid to the envelope
Envelope
Viral membrane
What is the envelope composed of
Lipid bilayer carrying viral glycoproteins
What viral antigens are of diagnostic value?
Proteins
What family of viruses is responsible for polio?
Picornaviruses
What human-infecting viruses are included in picornaviruses?
- enteroviruses
- rhinoviruses
- Hep A virus
What does the term entero mean in enteroviruses?
Enteric means of spread of these viruses - via the fecal-oral route
What do enteroviruses include?
Poliovirus types 1-3
Coxsackie A and B
Echoviruses
Enteroviruses 68-71
What does the poliovirus cause?
Poliomyelitis
What is the structure of the poliovirus?
Very small
single stranded positive RNA virus
Icosahedral capsid
No envelope
Where does the poliovirus replicate?
It preferentially replicates in the motor neurons of the anterior horn of the spinal cord
What is the result of the replication of polioviruses in their preferred site?
Death of the motor neurons of the anterior horn of the spinal cord - leading to muscle paralysis
How is poliovirus transmitted?
Consumption of water with fecal contaminants
Is poliovirus common in the western world?
No, because of successful vaccination programs
Initial symptoms of poliomyelitis
Headache
Vomiting
Constipation
Sore throat
What follows the initial symptoms of poliomyelitis?
Paralysis which is asymmetric and flaccid
How many vaccines are used for poliomyelitis?
Two
What kind of immunization do polio vaccines provide?
Active immunization
Name the two vaccines used against poliomyelitis
Salk
Sabin
Salk vaccine composition
Formalin-treated inactivated viruses
How is salk vaccine delivered
IV
Sabin vaccine composition
Live attenuated viruses
How is sabin vaccine delivered
Orally
How many types of polio virus do the vaccines contain?
3 - trivalent
Largest and most complex DNA virus
Poxvirus family
How many viruses of medical importance does the poxvirus family include?
3 -
Smallpox virus (variola virus)
vaccinia virus
Molluscum contagious virus (MCV)
What is the general morphology of poxviruses?
Complex, oval to brick-shaped morphology with internal structure
smallpox virus aka
variola virus
What are the dimensions of the poxviruses?
300nm x 200nm (very large)
What does the viral genome of poxviruses contain?
A large, double stranded, linear DNA that is fused at both ends.
Where do poxviruses multiply?
Cytoplasm of host cells - unusual of DNA viruses which usually multiply in the nucleus
Which is the most important human poxvirus?
Smallpox (variola)
What symptom is associated with poxviruses?
Skin rashes
What is smallpox characterised by?
High fever
Prostration
A vesicular, pustular rash
Smallpox is
An acute, highly infectious, often fatal disease
How was smallpox eradicated?
Global use of the vaccine
What does the smallpox vaccine contain?
Live attenuated vaccinia virus
What enzyme does the virion of poxviruses contain?
DNA Dependent RNA polymerase
Why do poxviruses need DNA dependent RNA polymerase?
They replicate in the cytoplasm, and hence do not have access to the cellular RNA polymerase which is located in the nucleus
How many serotypes does the smallpox virus have?
A single stable serotype
What is the key to the success of the vaccine against smallpox?
The presence of a single stable serotype
What would have caused failure of eradication of smallpox?
A varied antigenicity like that of influenza
Name icosahedral DNA viruses other than the poxviruses
Herpesviruses
Adenoviruses
Papovaviruses
Hepadnavirus
They multiply in the nucleus of the host cells
Which are the only DNA viruses that replicate in the cytoplasm of the host cell?
Poxviruses
Members of the picornaviridae family
Poliovirus Coxsackie virus Enterovirus Hep A virus Rhinovirus
Name a large family of small viruses
Picornaviruses - Small = 30nm viruses
Structure of picornaviruses
Non-enveloped
Single stranded positive RNA genome
Icosahedral capsid
What is peculiar about picornaviruses?
They are incapable of causing cell transformation due to the RNA genome
Why can’t picornaviruses cause cell transformation?
RNA genome
What virus causes herpangina and hand-foot-and-mouth disease?
Coxsackie Group A viruses
How do you distinguish between herpangina and hand-foot-and-mouth disease?
Oral lesion locations
When oral lesions are located on the throat, palate or tongue, what kind of Coxsackievirus disease is it?
Herpangina
What kind of Coxsackie viral disease causes lesions to appear on the buccal mucosa and gingiva?
Hand-foot-and-mouth disease
What are the manifestations of diseases caused by the Coxsackie Group A virus?
Vesicular lesions (location defines specific disease)
- fever
- sore throat
- pain on swallowing
How does Coxsackie Group B virus get its name?
B for body
What are the manifestations of disease with Coxsackie group B virus?
Chest pain with headache
Fatigue
Aching muscles lasting 4-5 days
Diseases associated with echoviruses
Aseptic meningitis Encephalitis Paralysis Rash Fever Acute URTIs Enteritis Pleurodynia Myocarditis Neonatal infections
What is the main cause of the common cold?
Rhinoviruses
How many serologic types of rhinoviruses exist?
> 100
What is the main reason that a vaccine hasn’t been found for the common cold yet?
There are > 100 serologic types of rhinoviruses present
What virus family is EBV part of?
Herpesvirus
What is oral hairy leukoplakia?
A whitish, nonmalignant lesion on the tongue
What disease is oral hairy leukoplakia especially associated with?
AIDS
What virus is associated with oral hairy leukoplakia?
EBV
What is EBV associated with the development of?
Burkitt’s lymphoma
Nasopharyngeal ca
What kind of cells does EBV specifically infect?
B lymphocytes
Does EBV remain latent?
Yes - in resting memory B lymphocytes after primary infection
What is a highly diagnostic test for EBV?
Heterophile test
Heterophile test aka
Mononucleosis spot test
Lab findings of mononucleosis
Lymphocytosis
presence of atypical lymphocytes
IgM heterophile antibodies
What does the heterophile test do?
Identifies IgM heterophile antibodies
How many patients show a positive result in the heterophile test?
80% of those with infectious mononucleosis
Rubella aka
German measles
Cause of rubella
Spherical, enveloped RNA virus
How is Rubella virus spread?
Droplets
Characteristic presenting signs of German measles
- Characteristic rash - flat pink spots on the face that spread to other body parts
Characteristic presenting sign of Measles
Koplik’s spots
Measles aka
rubeola
Where are Koplik’s spots found?
Oral cavity, opposite molars
Describe the nature of Koplik’s spots
Small Bluish white lesions Surrounded by a red ring Cannot be wiped off Occur opposite molars
Koplik’s spots
Found in measles
Paramyxoviruses
Heterogenous group of enveloped viruses with negative ssRNA genomes
Enlargement of parotid glands is seen in …
Mumps
Serious complications of mumps
Deafness in children
Orchitis in males past puberty
Orchitis
inflammation of the testis
Causes of parainfluenza
Parainfluenza viruses types I-IV
What do Parainfluenza viruses cause?
Acute respiratory disease
MMR vaccine is used for
Measles mumps and rubella
What does MMR vaccine contain
Three live attenuated virus
How is MMR vaccine administered
Via injection
What is the schedule of administration of MMR vaccine?
1 year old - first dose
Before starting school (age 4/5) - Booster dose
What does the word retro in retroviruses refer to?
The possession of the enzyme reverse transcriptase
What does reverse transcriptase do?
It transcribes RNA to DNA during the process of viral nucleic acid synthesis
Why are HIV 1 and HIV 2 classified as lentiviruses?
Because of their slowly progressive clinical effects
What is reverse transcriptase?
An RNA directed DNA polymerase
What does the nucleocapsid of HIV consist of?
2 single strands of RNA along with 3 enzymes, all encased in an outer lipid envelope
What are the enzymes contained in HIV?
Reverse transcriptase
Protease
Integrase
What is the lipid envelope of HIV derived from?
A host cell
How is the lipid envelope of HIV derived?
It is derived from a host cell via budding
How many surface projections does the envelope of HIV have?
72
What do the surface projections of the HIV envelope contain?
An antigen - gp120
What does the antigen in the surface projections of HIV do?
The antigen - gp120 - aids in the binding of the virus to the target cells with CD4 receptors
Are there other proteins apart from gp120 in the envelope?
Yes - gp41 - it binds gp120 to the lipid envelope
How many major genes does the genome of HIV contain?
3
How many major genes do the genomes of retroviruses contain?
3
What are the major genes in the genome of HIV?
- env gene
- pol gene
- gag gene
What is the gene in HIV that codes for the envelope glycoproteins?
env gene
What gene in HIV codes for its enzymes?
pol gene
What does the gag gene do in HIV?
Codes for the core proteins
How does transmission of HIV occur?
Sexual contact
Transfer of infected blood
What is the action of HIV in the body?
IT infects and kills Helper CD4 T-cells
What is the effect of the death of helper CD4 T-cells?
Depression of both humoral and cell-mediated immunity
What kind of immunity does HIV target?
Both humoral and cell-mediated immunity
Which are the first cells to be infected by HIV?
Macrophages
What distinctive action does HIV have on cells?
It has a distinctive CPE - cytopathic effect - called giant cell (syncytial) formation
What kinds of receptors are required for HIV to infect cells?
- CD4 receptor
- Chemokine (a core receptor)
What is the reason for rapid emergence of new strains of HIV?
Frequent errors introduced by viral reverse transcriptase
How does Acute HIV 1 primary infection present?
A mononucleosis-like syndrome
- fever
- fatigue
- sore throat
- skin rash
How does HIV differ from RNA tumor viruses?
It lyses host cells
What are the other retroviruses apart from HIV?
HTLV 1 and 2, classified as oncoviruses.
Name 3 types of viruses that contain negative sense RNA
Orthomyxoviruses
Paramyxoviruses
Rhabdoviruses
What kind of RNA polarity do retroviruses have?
Positive polarity
What does positive sense RNA molecule mean?
RNA with the same base sequence as mRNA
What kind of base sequence does RNA with negative polarity have?
one that is complementary to mRNA
What kinds of viruses does the term positive and negative polarity refer to?
RNA viruses
What is the first step in viral gene expression?
mRNA synthesis
What is the difference in mRNA synthesis faced by positive and negative sense RNA viruses?
Positive polarity RNA viruses can use their RNA genome directly as mRNA
What do negative polarity RNA viruses have that positive polarity RNA viruses don’t?
Their own RNA dependent RNA polymerase - as host cells do not have an RNA polymerase capable of using RNA as a template
What can be the structural variations in an RNA virus genome?
They can be single stranded or double stranded, segmented or non-segmented.
What is the age group most affected by varicella?
Varicella aka chickenpox - 90% of all cases are in children under 9 years of age
Presentation of varicella
Local lesions (vesicles) in skin after dissemination of virus through the body;
The lesions become encrusted and fall off in a week
What does aspirin administration do during childhood viral infections?
Increases the incidence of Reye’s syndrome
What is Reye’s syndrome
It can cause encephalitis and liver impairment
How does shingles present?
Shingles (herpes zoster) presents as painful vesicles on skin or mucosal surfaces along distribution of a sensory nerve
In what kind of patients is shingles more common?
Immunocompromised individuals
Is shingles localised?
Yes - to a single dermatome
Adenosine arabinoside aka
vidarabine
What suppresses the synthesis of varicella zoster and HSVs?
Adenosine arabinoside
What tends to diminish new lesion formation and duration of fever in VZV infections?
vidarabine
What does vidarabine do to VZV spread?
it prevents the spread of the virus through the viscera.
What family do influenza viruses belong to?
Orthomyxovirus family - they are the only members of this family
Composition of influenza virus
Unique segmented, negative, ssRNA genome
Shape of influenza virus
Spherical or filamentous enveloped virus
Types of influenza virus
3 - A, B, C
How are the three types of influenza viruses distinguished?
The nature of their internal proteins
What kind of influenza virus is responsible for pandemics and epidemics?
Influenza A
What kind of influenza virus causes smaller outbreaks which are localised and milder - such as in camps or schools?
Influenza B
What does Influenza C cause?
Mild Upper respiratory tract illness
What kinds of spikes cover the envelope of Influenza viruses?
2 - Hemagglutinin, and neuraminidase
What is the role of Hemagglutinin spikes?
Hemagglutinin is a surface protein and aids attachment of the virus to the cell wall of susceptible host cells at specific receptor sites
What part of the influenza virus facilitates cell penetration?
Neuraminidase spikes in the envelope
How does cell penetration occur in the influenza virus?
Pinocytosis and release of replicated viruses from the cell surface effected by budding through the cell membrane
What is the ability of the influenza virus to cause epidemics dependent on?
Antigenic changes in Hemagglutinin and neuraminidase
What kind of changes can happen in hemagglutinin and neuraminidase?
- Antigenic shifts
- Antigenic drifts
What are antigenic shifts?
Major changes based on reassortment of genome pieces
What are antigenic drifts?
Minor changes based on point mutations
Manifestations of Reye’s syndrome
- Vomiting
- Lethargy
- may result in coma.
What is the fatality rate of Reye’s syndrome?
40%
What kind of infections is Reye’s syndrome associated with?
Influenza or chickenpox (VZV or Herpes zoster) especially in young children treated with aspirin
What medications are not associated with Reye’s syndrome?
Acetaminophen
Ibuprofen
What is the most noticeable symptom of mumps?
painful swelling of the parotid glands - uni or bilateral
Other significant complications of mumps
- deafness in children
- orchitis possibly leading to sterility in post-pubertal males
What medications can be used in influenza?
Amantadine
Rimantadine act to prevent viral replication and are only effective against influenza A
What disease presents with flu like symptoms, lymphadenopathy followed by a rash on the entire body?
German measles (rubeola)
Causative organisms of pharyngitis
Adenoviruses
Coxsackieviruses
what viruses are spread by arthropod vectors?
Arboviruses -
- Alphaviruses
- Flaviviruses
Name flaviviruses
Yellow fever virus
Dengue virus
West Nile virus
What family are alphaviruses a member of?
Togavirus family
What family are rhinoviruses a member of?
Picornaviruses
What is the structure of rhinoviruses?
ssRNA (positive sense) with icosahedral capsid and no envelope
Name other agents likely to cause the symptoms of the common cold
Enteroviruses
Coronaviruses
Adenoviruses
Parainfluenzaviruses
