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