Day 4: Herpesviruses, Intro Virus Vaccines, Picornaviruses Flashcards
HC09, 10, 11
HC09:Generally, animal vaccines mean:
Less quality, more frequent
Classification Herpesviruses
- Large dsDNA viruses 80-240 kb
- Enveloped
- Pox viruses are also enveloped large dsDNA viruses
ICTV
Committee on taxonomy of viruses
3 subfamilies within orthoherpesviridae within herpesvirales order
- Alphaherpesviridae
- Betaherpesviridae
- Gammaherpesviridae
Lineages of herpesvirues are … specific
Species-specific > some human-specific
8 human herpesviruses
- HHV1 tm 8
> HHV-1/2: HSV-1/2: Herpes simplex virus
> HHV-3: VZV (varicella zoster virus)
> HHV-4: Epstein-Barr virus (EBV): causes mononucleosis (Fiver), lymphoma
> HHV-5: Cytomegalovirus (CMV): disease of Fiver, retinitis, congenital infection
> HHV-6/7 (Roseolavirus)
> HHV-8: KSHV: causing Kaposi sarcoma, lymphoma, multicentric Castleman disease
Prevalence herpesviruses in Europe/USA
- 100% for HHV-6/7
- 60% HSV-1
- > 95% VZV
- 40% CMV (100% in developing countries)
- 25-50% EBV (90-95% worldwide)
- <5% HHV-8
- 16% HSV-2
Length genomes herpesviruses in general
very long
> 100-250 kb
Herpes virus particle
- Space between the capsids and envelope > proteins with them from cytosol of the host cell
» in retroviruses as well: including nucleotides for next cycle
» maybe selective - Four morphologically distinct structures
> DNA core
> Capsid
> Tegument: space between nucleocapsid and envelope with tegument proteins which are virus-encoded and are important for viral protein processes
> Envelope
Which cells infected by herpesviruses
- Alphaherpesviruses: Mucosal cells and neurons
- Betaherpesviruses: monocytes, macrphages, T-cells (HHV-6/7), DCs, megakaryotes, myeloid progenitor cells in bone marrow
- Gammaherpesviruses: B-cells, endethelial cells, macrophages, epithelial cells
» start in immune cells and let the infect other cells
Herpesviruses latency
Just like retroviruses
> can become latent
> In alphaherpesviruses: latency in neurons
> beta: in nonneuronal cells (several)
> gamma: mainly in B and T lymphocytes
- Stay in the cell, can become lytic again, activation, make particles and reactivation
Genome herpesviruses in particle and in host
Linear in virion and becomes circular in the host cell
Expression virus herpes after infection in latent cycle
Some proteins, not all of them
> cell not recognized as infected: active process of silencing by not expressing
> but still potency to reactivate lytic cycle
> immune system thus involved
Latency is characterized by three distinct processes, namely
- Viral persistance, circularization of genome
- Restricted virus expression which alters cell growth and proliferation
- Retained potential for reactivation to lytic cycle
Herpesvirus and HIV
Herpes can replicate again because immune deprivation
Herpes reactivation and eldery
Less immunity so more reactivation into lytic cycle
Genuses of Alphaherpesviruses
Simplexviruses and varicelloviruses
Herpes simplex 1/2 infection and replication
After infection, replication in mucosal cells, then enters sensory nerve endings in lesion and becomes transported to dorsal root ganglion
> primary lesion is resolved when adaptive immune responses evolve
> latent virus remains in ganglion
> when lytic reactivation: goes to neural ends and to the mucosal cells once agains
> cold sores (koortslip)
> dangerous for small children
Pathogenesis cold sores and zoster (gordelroos)
HSV and VZV
> both infections in mucocutaneous nerve endings to travels up axon to reach and hide latent in sensory neurons
> recurrence are due to reactivation of virus within the neuron to become infectious followed by passage of virus down the axon to mucocutaneous sites and local spread and replication to form clinical lesions
> from waterpokken if it comes back> crawls out
> vaccines for eldery
> vesicles with fluid: the lesions
> can be transmitted
Genital herpes
HSV-2
HSV-2 character
dsDNA
- re-infection possible, recombination possible > recombinants detected
> alphaherpesvirus subfamily
> different strains exist
> origin: cross-species transmission
Epidemiology HSV-2
Etiologic agent of genital herpes and most common cause of genital ulcer disease (GUD)
> highly prevalent STI: sexually transmitted infection
> prevalence varies by geographic region, age, gender, study population and HIV-1 serostatus
A lot of genital herpes is through HSV-1 nowadays instead of HSV-2, how
HSV-1 causes oral herpes
> different sexual behaviour (oral sex)
> HSV-1 could be first herpesvirus to be infected with, as the infection is likely to spread during childhood (parent to child), then it will already be there during first sexual experience.
> it is apparently not an HSV-2 specific characteristic to infect genital tissue and HSV-1 to infect oral mucosae, but preference could have changed
VZV disease
Varicella-zoster virus (alphaherpesvirus subfamily) causes two clinically distinct forms of disease
> varicella: chickenpox (waterpokken)
> herpes zoster: shingles (gordelroos)
Primary VZV infection results in …
Varicella: chickenpox
Infection VZV
When close contact with vesicles of zoster or varicella
Macule, papule and vesicle
Macule: change in surface color, without elevation or depression
Papule: small curcumscribed solid elavation of skin with no visible fluid
Vesicle: small blister, circumscribed, fluid-containing epidermal elevation
4 betaherpesviruses in human
- Cytomegalovirus (CMV/HHV5)
- HHV6A and HHV6B
- HHV7
CMV seroprevalence correlates inversely with country …
socioeconomic development: highest rate in developing countries
CMV character
Very infectious
- also transmission possible via placenta
- many problems: early in embryo: no vital child, later: congenital disorders
Transmission CMV
- Sexual: virus can be detected in genital tract
- Close contacts; seroconverion well-described among family members and children in daycare centers > contacts exposed to virus shed from upper respiratory tract and urine
- Blood or tissue exposure: transmission of CMV following transfusion of blood products and transplantation of organs from seropositive donors
- Perinatal: neonates and infants via utero during maternal viremia, exposure secretions in birth canal or postnatally from breast milk
CMV disease
CMV Mononucleosis
> syndrome resembling infectious mononucleosis is most common presentation of symptomatic CMV in immunocompetent adults
> children most at risk > saliva > mother also chance for CMV infection when pregnant
> Infectious mononucleosis (IM): fever, tonsillar pharyngitis and lymphadenopathy
> IM mostly caused by EBV
> congenital malformations
> disease of Fiver / Kissing disease > tonsils swell and transmitted through saliva
HHV6 and HHV7 character
Genus roseolovirus
> establish latency in leukocytes
> ubiquitous: everybody gets it
> no serious disease known, although HHV6A in some studies linked to MS
>
The sixth disease
Maculopapular rash in roseola infantum
HHV-6 is the only herpesvirus that can …
integrate in host genome
HHV-6 and HHV-7 has so called TRS motifs. Where? And how recombination?
Telomere repeat sequences at genomic DNA terminal ends
> integration in host genome through homologous recombination
> HHV-6 (but not HHV-7) codes for protein (U94) with a possible role in integration process
> HHV-7 does not integrate
HHV-6 can be reactivated in a treatment for cancer, which one?
CAR T-cells
> byproduct, encephalitis because many viral infections
How to test for integrated HHV-6 in genome of all cells
Test hair follicles > HHV-6 should not infect there > if its DNA is present, it was integrated from germ-line
Reactivation HHV-7 causes:
Lichen planus: red rash
Gamma herpesviruses infecting humans: 2
- Epstein-Barr virus
- HHV-8
EBV character
- Acquired during childhood years and often subclinical
- Traditionally peak incidence of infection in 15-24 years age
- EBV is major cause of infectious mononucleosis
Genome EBV
Circular with a lot of genes
dsDNA, also some RNAs coded in genome
Phases EBV
Primary latent phase and lytic phase
EBV receptor
Receptor for EBV on B-cells is CD21
EBV DNA form in virion and in cell
In virus particle: linear
> the terminal repeats mediate circularization in infected cells
> each infected cell contains 1-20 copies of EBV episomes in nucleus
EBV types and strains
2 types
> EBV-1
> EBV-2
» extensive homology between the two.
Difference EBV types
In the latent infection cycle nuclear antigen genes
> EBV-1 more prevalent than EBV-2 in USA and Europe but evenly distributed in Africa
EBV and HHV-8 oncogenic potential
- Latent membrane protein 1 (LMP1) is condered major oncogene of EBV as it has transforming properties in cultured cells > B-lymphocyte transformation
- LMP1 functions as constitutively active member of tumor necrosis factor receptor family and activates multiple signalling pathways like MAPK and PI3K/Akt and NF-kB
> several other latent EBV proteins essential for viral immortlization of B-cells
EBV and Burkitt’s lymphoma
Endemic, sporadic and immunodeficiency related types
> EBV in almost all cases
Malaria as co-carcinogen
co-carcinogen in EBV-related nasopharyngeal carcinoma
Dried fish
> common in South East Asia
HHV-8 character
- Latest human herpesvirus to be discovered
- Low prevalence in developed countries except risk groups
- High prevalence in sub-Saharan Africa
- Infects variety cof cells including B-cells, endothelial cells, macrophages, and epithelial cells
Geographical seroprevalence of HHV-8/KSHV correlates with…
Incidence Kaposi’s sarcoma (in males) (KS)
HHV-8 can cause several neoplastic diseases, but generally begin benign in immunocompetent host. Main types of cancers associated:
- Kaposi’s sarcoma (KS) > epithelial cells of lowerextremities
- Primary Effusion Lymphomas (PEL) > B-cells
- Multicentric Castleman’s disease (MCD) > B-cells
HHV-8 transmission
Through saliva
> present in oral cavity
> infectious particles
> prominent and shed in HIV-1 infected patients
Genital herpes: protection when condom or anti-herpes drugs
Not with condom, lesions go outside that
A bit with drugs, but no guarantee
HC10: Vaccine definition
Reagent to induce an artificial active immune response in order to build up immunological memory in preparation for an encounter with a pathogen
Do all vaccines protect against infection?
No, but they do protect against disease
> better response upon infection to prevent disease
Vaccine: primary and secondary immune response
By vaccination > primary immune response, small peak in antibodies > build immunological memory cells which remain
Infection > secondary immune response > more strong and rapid antibody response
FIrst eradicated disease with vaccination
Smallpox > variola virus
Vaccines are an integral part of existence, why?
- We immunize children, adults, demesticated and wildlife animals
- Because vaccination, childhood diseases become rare
- Vaccines are major part of western nations public health care measure
Herd immunity concept
Virus spread stops when the probability of infection drops below a critical threshold, which is virus and population specific
> for example: 93-95% > 80% vaccinated, 76% immune (some non-responders)
R0
Number of people infected by one person
> R0 < 0: disease decreases, vaccine helps
Ring vaccination
Vaccination of all close persons to infected person > lower the infection rate
Why is no vaccine 100% effective
Non-responders and immunocompromised
Effect of declining vaccine coverage
Causing small outbreaks currently of measles and whooping cough for example
Polio virus eradication
- Almost eradicated
- Severe disease for children
- Types 2 and 3 are eradicated
- Endemic type 1 in Afghanistan and Pakistan
- Vaccination is key
- Takes longer than smallpox to eradicate
Active vs passive vaccination
- Active: administration of modified form of pathogen or material derived from it that induces immunity to disease; long term protection
- Passive: mAb or polyclonal serum: administration of products of immune response to the recipient.
» for immunocompromised people like chemotherapy patients
Maternal antibody protection
Antibodies passively protect infants through placenta
> for whooping cough and RSV
> combination active and passive vaccination
> mother is vaccinated
types of active vaccines (9)
- Live-attenuated: goes into cells and can replicate but weakened: no disease but immune response
- Killed whole organism: dead virus by radiation is injected, cannot enter cell and replicate, immune system sees whole particle
- Toxoids: can cause disease and results in antibodies
- Subunit: purified protein for example: direct antigens but immune reaction > spike protein for example
- Virus like particles: artificially made virus like particles without DNA or RNA
- Outer membrane vesicle with antigens
- Protein-polysaccharide conjugate
- Viral vectored
- Nucleid acid vaccines: DNA/RNA vaccine with lipid nanoparticles delivered > make protein
Adjuvants
Extra activators of immune system > danger signals to bind the PRRs of immune cells (Pattern Recognizing Receptors)
Recombinant viral vectors
Put genetic material in the cell
> antigen expression > degradation and presentation antigen on MHC molecules on cell surface to immune cells
> make apoptotic bodies and secrete antigens (innate response) > macrophage / APC activates adaptive immune system
mRNA vaccine SARS-CoV-2
mRNA-LNP (lipid nanoparticle) uptkae
> mRNA translation
> RNA sensing by TLRs
> presentation on MHC-I
> secreted proteins (antigens)
> immune cells take up secreted protein and present on MHC-II
Which cells need to be activated by vaccine for best immune reaction
B-cells and T-cells > humoral and cellular responses
Most safe vaccines
Protein and DNA/RNA vaccines
Most effective immune activation: which vaccines?
Live or live-vector
Protein vaccine downside
Bad T-cell response
Why no protein vaccine used for herpes
T-cell response is required
Which kind of vaccine chosen based on …
Which kind of immune response you want
How quick development COVID-19 vaccine
- Clinical testing and manufacturing: staggered versus sequential processes
- Government ensures companies for risks
- Lessons learnt from HIV-1, RSV and SARS/MERS > antigen stabilization
- Newer and quicker antigen delivery platforms > RNA and viral vectors (quick to make)
> protein to be made was known: spike protein
Why not quick development vaccine against other pathogens
- Viral diversity and evolution
- Mostly endemic in low- and middle income countries
- Sterilizing immunity needed for efficacy / persistent viruses (HIV, Herpes)
- many forms of the pathogen / difficult protein structures / many targets
- Some pathogens hide within cells, making them invisible to immune response (latent, herpes)
HIV-1 vaccine requirement
Should protect against infection, after infection, it stays in the body
Why novel vaccine platforms developed?
Because the traditional attenuated and killed viruses can’t be used for all viruses and are more difficult to produce and adapt
HC11; Family picornaviruses character
- Pico (small) RNA
- (+) ssRNA
- Non-enveloped: naked viruses
- Most well-known: Poliovirus
> genus enterovirus
3-4 structural proteins in picornavirus
VP1-4
> at 5’ side of genome
> derived from large polyprotein
Picornavirus classification
Using molecular sequencing for VP1 protein
VP1 protein
Receptor binding protein (for host cell binding) > used for classification (5’ end PCR and sequencing)
Diversity in picornavirus family due to:
Mutation and recombination
> between virus within species: recombination
> high mutation frequency: RNA polymerase, no proofreading: 1 in 10^5 error rate
Replication cycle picornavirus
- VP1 binds host cell receptor
- Receptor mediated endocytosis
- Endolysosome: pH causes capsid to break: RNA to cytosol and viral proteins
- RNA translation directly (+ strand)
- Polyprotein made: cleaved into subunits: P1 to VP1-4
- 3D is RdRp (RNA dependent RNA polymerase): make additional RNAs from other part
- dsRNA after replication: host can detect it: only pathogenic
- Exit replicated genome with structural proteins for capsid
> dsRNA into vesicles to hide
> sometimes empty capsids released
Picornaviruses were thought to make one polyprotein only. What is the consensus now?
They also have ORF to code for RNAs.
Complications rhinovirus
Spinal cors and heart and liver problems
Common symptoms picornaviruses
Encephalitis, poliovirus associated poliomyelitis, acute paralysis
> many organs affected
> VP1 can bind different host receptors
Cell tropism determined by
receptors (partly)
Poliovirus characterics
- Enterovirus genus, picornavirus family
- Almost second virus to eradicate, not there yet
- Effective polio vaccine
- Poliomyelitis
- Paralysis
Why polio epidemics in 1900s?
Sanitation
> infants shortly infected after birth pre-1900s
> maternal antibodies prevent paralysis
Improved sanitation to prevent fecal-oral route
> virus does not go away, once maternal antibodies are gone, no protection: infection leads to symptoms.
Clinical character poliovirus in ratio of population
- 72% no symptoms (majority)
- 24% abortive poliomyelitis: fever, malaise, headache, sore throat, vomiting
- 1-5% non paralytic aseptic meningitis
-0.1-0.5%: paralytic poliomyelitis: weakness, paralysis, death
Incubation period polio virus
7 days
> increase viral lead in throat
> early symptoms: nausea, fever etc.
> pass epithelial laters and reach nervous system : disease
Pathogenesis poliovirus
- Enter through mouth
- Infect oropharynx, tonsils and intestinal tract
- Replication
- Epithelial barrier breached and go to lymph nodes and go into circulation of neurons in gut > reach CNS and cause paralysis
Neuron-muscle (neuromuscular junction) interaction in polio
Disrupted
> neurotransmitter acetylcholine cannot pass signals to muscle
> botox toxin inhibits acetylcholine release, can cause paralysis
2 Types vacccines for polio
- Inactive polio vaccine
- Oral polio vaccine
Inactive polio vaccine
- Most used in Western world
- Not a less active form of wild-type (that is the oral one)
- 3 or 4 doses
- Intramuscular or subcutaneous
Oral polio vaccine
- In developing countries more used
- Less-active form of virus
- Must replicate to be effective: administered orally
- Attenuated: cannot replicate in neurons but in GI tract only
- Live-attenuated
- Local immune response but not neurovirulent
- Stimulates local IgA and humoral IgM and IgG
- 3-4 doses
- Virus excreted in feces, community protection
Strains made for oral polio vaccine
Sabin Type 1/2/3
Inactivated (injection) vs Attenuated (oral) polio vaccine
- Inactivated: only IgG vs Oral: IgG, IgM and IgA
- Duration immunity longer for oral
- Possible mutation to neurovirulence is possible in oral vaccine > very rare, due to recombination
> most polio cases are vaccine derived nowadays - Attenuated vaccine is cheaper and simple administration, easier storage, less skilled staff needed
Human Rhinovirus types
A, B and C
> rhinvirus is most prevalen human virus which causes cold
Non-polio enteroviruses: most problematic one
4 different at species level
> most problematic: causing hand-foot-mouth disease
> blisters in feet and mouth
> enterovirus type A: EV-A71, CVA6, CVA10, CVA16
EV-A71
> EV-A71
> neurotropic entervirus
> epidemics in Asia
> infections of Brain: complications
Poliovirus is a enterovirus species ..
C
Enteroviruses vs Rhinoviruses
Acid resistance
> Entero: resistant: survives passage through stomach
> Rhino: sensitive
Replication
> E: In repiratory tract or small intestine
> R: Respiratory tract
Invasion
> E: Can invade body and travel to other end organs
> R: not invasive
Diagnosis
> E: feces PCR, respiratory sample and more
> P: respiratory sample PCR
Risk Netherlands for polio outbreak
- Contaminated waters
- Antivaxx
Enterovirus D68 (EV-D86)
Another enterovirus causing paralysis
> peaks every two years, also in Netherlands
> if it can transmit more efficiently: risks
Pathogenicity and treatment picornaviruses
- Narrow species tropism of enteroviruses
- severity related to virus type and host factors
- Humoral immunity is key: mostly acute and self-limiting
- Target population for severe infections are neonates and immunocompromised
- No effective antivirals and few vaccines available (polio vaccine and EV-A71)
Chronic infections picornaviruses
In primary immunodeficiency
> shortcomings in development and function immune system
> Examples
» common variable immunodeficiency (CVID): low Ab levels
» X-linked agammaglobulinemia: no mature B-cells
» severe combined immunodeficiency: distrubed development T/B cells
Most frequent infections in mankind are:
Picornaviruses, mostly mild
Knowledge gaps picornaviruses
Prevalence, pathogenesis, transmission\
> no effective antivirals and limited vaccine availability
