Herpes Virus Flashcards
Herpes Virus Features
Large Envelope, ds DNA virus. = Approx 120 - 200 nm in diameter ,
Icosahedral Capsid Symmetry -Surrounded by Lipoprotein Envelope.
What do all herpes viruses have in common?
A common virion morphology.
A basic mode of replication.
The capacity to establish acute , latent and recurrent infections
The space between capsid & envelope is called?
Tegument
Tegument - purpose
filled by protein and enzymes , that help to initiate replication
Herpes - life cycle
1) Recognition of host cell
↓
2) Attachment
↓
3) Penetration
↓
4) Uncoating-split of double stranded DNA.( Linear ds DNA )
↓
Circularisation –becomes circular
↓
5) Transcription
↓
6) Protein synthesis(α, β, γ)
↓
7) Replication - by rolling circle
↓
8) Assembly & Envelopment
9) Exocytosis- Lysis & release
Human herpes viruses are grouped into 3 sub-families, based on difference in viral characteristics, which are?
Genome structure , tissue tropism , cytopathogenicity , site of latent infection
Human Herpes Simplex type 1 & 2 and Varicella-Zoster virus ( HHV3) are part of which group?
α Group
- Short reproductive cycle
- Latent in sensory neurons
- Painful skin disease
Human Herpes Simplex type 1 & 2
Skin lesions & other diseases
Varicella-Zoster virus ( HHV3)
Varicella (Chickenpox) & Zoster
Cytomegalovirus (HHV5) (CMV), Human Herpes virus 6 (HHV 6) and Human Herpes virus 7 ( HHV 7 )
β Group
- Long reproductive cycle
- Latent in WBCs
Cytomegalovirus (HHV5) (CMV)
Cytomegalic inclusion disease (CID) , Disseminated diseases in immuno compromised patients
Human Herpes virus 6 (HHV 6)
Roseola infantum /lymphydenopathy
Human Herpes virus 7 ( HHV 7 )
Roseola infantum / febrile seizures
Human Epstein- Barr virus (HHV4) and Human Herpes virus 8
γ Group
- Latent in lymphocytes
- Associated with cancer
Human Epstein- Barr virus (HHV4)
Infectious Mononucleosis , Burkitt’s Lymphoma & Nasophyryngeal Carcinoma .
Human Herpes virus 8
Kaposi’s sarcoma related herpesvirus (HHV8)
Human herpes virus 1 - virus
Herpes simplex type 1 ( HSV -1 )
Human herpes virus 1 - Disease caused
Oral , Ocular lesion , Encephalitis , Skin lesions
Human herpes virus 1 - Site of latency
Neuron-Trigeminal ganglia
Human herpes virus 1 - Transmission
Close contact
Human herpes virus 2 - virus
Herpes simplex type 2 ( HSV- 2 )
Human herpes virus 2 - Disease caused
Genital , Neonatal infection , aseptic meningitis
Human herpes virus 2 - Site of latency
Neuron-Sacral ganglia
Human herpes virus 2 - Transmission
Close contact , S.T.D.
Human herpes virus 3 - virus
Varicella Zoster ( VZV )
Human herpes virus 3 - disease caused
Chickenpox & herpes zoster
Human herpes virus 3 - site of latency
Neuron- Trig.gang
Human herpes virus 3 - transmission
Respiratory & Close contact
Alpha- herpesvirinae - primary target cell
Mucoepithelial cells – Fast-growing
Human herpes virus 5 - virus
Cytomegalovirus ( CMV )
Human herpes virus 5 - primary target cell
Leucocytes, Monocytes (M), Lymphocytes(L), Epithelial cells (EC)
Human herpes virus 5 - site of latency
Kidneys ; Glands Monocytes (M) Lymphocytes(L)
Human herpes virus 5 - means of spread
Close contact, Transfusions, Tissue transplant, Congenital, STD
Human herpes virus 6 - virus
Herpes lymphotropic RosealaInfantum
Human herpes virus 6 - primary target cell
T cells, M, L, EC
Human herpes virus 6 - site of latency
Lymphoid tissue ( T cells )
Human herpes virus 6 - means of spread
Respiratory & close contact
Slow-growing , ( Massive enlargment of infected cells ) .
Beta - herpesvirinae
Human herpes virus 7 - virus
RK virus
Human herpes virus 7 - primary target cell
T cells
Human herpes virus 7 - site of latency
Lymphoid tissue ( T cells )
Human herpesvirus 4 - virus
Epstein-Barr virus ( EBV )
Human herpesvirus 4 - primary target cell
B Lymphocytes & EC
Human herpesvirus 4 - site of latency
Lymphoid tissue (B cells)
Human herpesvirus 4 - transmission
Saliva ( Kissing disease )
Human herpes virus 8 - virus
Kaposi’s sarcoma related virus
Human herpes virus 8 - primary target cell
Lymphocytes and others
Human herpes virus 8 - transmission
Saliva
HHV-5 – diseases caused
Congenital CMV infection , Infection in immuno compromised , acquired CMV infection , Mononucleosis like syndrome ( heterophil antibody - negative ) .
HHV-6 – diseases caused
Roseola in infant (primary infection) , Lymphydenopathy ,
Infection in allograft recipient - pneumonia , marrow failure
HHV-7 – diseases caused
Some cases of Roseola , Febrile seizures in children
HHV-4 Epstein Barr virus - ( EBV ) – diseases caused
Infectious mononucleosis ( Kissing Disease) ,Tumor including Burkitt’s lymphoma, Hodgkin’s ds , Nasopharyngeal carcinoma
HHV-8 Kaposi’s sarcoma – diseases caused
Associated with Kaposi’s sarcoma
HSV-1 and HSV-2 – features
- Extremely wide spread in human population
- Establishes latency in nerve cells - reactivation is common
- There are two distinct types of HSVs Type 1 & Type 2.
- Structurally & Morphologically indistinguishable
HSV-1 incubation period
2-12 days
HSV-2 incubation period
3 weeks
Reactivation of HSV 1 and 2 is caused by
Stress stimuli such as
UV light , Fever ,
Hormonal changes ,
Surgical trauma to the neuron.
Antibodies prevent reactivation (T/F)
False
HSV - pathogenesis
Why is HSV1 more commonly recurrent on mouth whilst HSV2 is more commonly recurrent on genitals?
HSV invades and replicates in neurons as well as in epidermal and dermal cells.
Virions travel from the initial site of infection on the skin or mucosa to the (Trigeminal ganglia - HSV-1 and Sacral ganglia- HSV-2) where latency is established.
HSV1 prefers to establish latency in Trigeminal ganglia whilst HSV2 prefers Sacral ganglia (which innervates the genitals)
Innervate - supply an organ with nerves
Acute Gingivostomatitis, Herpes Oro-labialis infection ,
Oropharyngeal infections
Acute Gingivostomatitis occurs in early childhood (T/F)
True
Acute Gingivostomatitis - symptoms
Fever , painful vesicular lesions on gums , lips & oral mucosa ,
these vesicles may rupture leaving a red based ulcer
Herpes Oro-labialis infection - symptoms
Milder recurrent form
Crops of vesicles at the mucocutaneous junction of lips or nose:
Corneal ulcers & lesions of conjunctival epithelium
Herpetic Keratoconjunctivitis
Dendritic ulcer or vesicles on the eye lids
Recurrent Herpetic Keratoconjunctivitis
– Can lead to blindness
Diseases caused by HSV-1
1- Oropharyngeal infections : 2- Herpetic Keratoconjunctivitis 3- Encephalitis : 4- Herpetic Whitlow : fingers 5- Eczema Herpeticum: 6. Meningitis
Encephalitis is more common (T/F)
True
Encephalitis involves where? How high is mortality?
Involves temporal lobe with high mortality.
PCR assay for viral DNA in CSF for which viral infection?
Encephalitis
Herpetic Whitlow also called
Fingers herpes infection
Who mostly contracts Herpetic Whitlow?
Healthcare workers, Dentists
Genital Herpes - transmission
Sexual contact
Genital herpes - symptoms
Vesiculo ulcerative lesions ( painful multiple ) of cervix , vulva , vagina , & perineum of females & On Glans or shaft of penis in males .
Neonatal herpes - transmission
Acquired in utero , during , or after birth
Severe in the newborn so , pregnant females with recurrent herpes should deliver by C .S . - which viral infection?
Neonatal herpes
Specimen - Herpes virus
Vesicular fluid (from vesicles) - Corneal scrapping , Skin swab .
Lab ID methods
Light Microscopy
Tzanck smear
Giesma stained smear
Tzanck smear - describe method + results
- Smear prepared from scrapping from the base of vesicles are stained with 1 % aq. soln. of Toluidine Blue O.
- Multinucleated giant cells with faceted nuclei & homogenously stained ‘ground glass’ chromatin
– Tzanck cells seen
Giesma stained smear -
Intranuclear Cowdry type A inclusion bodies
Direct immunofluorescence
Cell scrapings from lesions – stained with monoclonal antibodies with a fluorescence dye.
Viral inclusion bodies appear in microscope as a bright green Intra nuclear particles
Most appropriate test to confirm the diagnosis of HSV
Polymerase Chain Reaction ( PCR ) Assay
For detection of viral DNA ( genome ) in CSF ,vesicular fluid , skin scraping
Polymerase Chain Reaction ( PCR ) Assay
Tissue culture - Herpes Virus
Grown in human embryonic fibroblasts , Hep-2 cells or HeLa cells .
Result - culture
( CPEs ) - Swollen rounded cells ( enlarged & appear ballooned ) appear within 1-3 days . Fusion of infected cells results in syncytium formation .
What is serology mainly used for with respect to Herpes Virus?
Epidemiological studies
Serological methods - Herpes Virus
Ab (IgM) detection by ELISA , RIA and Western blot Test .or Complement FixationTest (CFT) .
TORCH
( Toxoplasmosis ; Other –(Varicella) ; Rubella ; Cytomegalovirus & Herpes simplex ) in pregnant women
Acyclovir - MoA and administration
Inhibits viral DNA polymerase enzyme.
Topical , Oral or IV.
Acyclovir affects latency.
Does not affect latency.
Drug of choice for acyclovir resistance cases
Foscarnet
Prevention - genital herpes
Avoid contact with individual with lesion .
Safe sexual practice. Use of condom
Varicella
Chickenpox
Zoster
Shingles
Prevalence rate - varicella
Highly communicable , with an attack rate of 90% in close contacts
Shingles occurs regularly (T/F)
False, it occurs sporadically
Shingles reservoir
Humans only
Where does reactivation of varicella zoster virus begin in adults?
reactivation of latent VZV present in trigeminal ganglia in adult life
Varicella - transmission
Airborne droplets & direct contact from varicella patients
Vesicular fluid of Zoster patients - in susceptible child
Pathogenesis - VZV
VZV infects the mucosa of the upper respiratory tract
Multiplies in the regional Lymph Nodes .
Primary viremia and spread to liver and spleen.
Secondary viremia follows with viral spread to the skin.
Typical rash occurs ( Centripetal distribution - highest on Trunk ) .
VZV remains latent in neurons of trigeminal ganglia for life.
Incubation period - Varicella
10-14 days
Symptoms - Varicella
Mild fever & rash
Rash - Varicella
First appear on Face & Trunk , spread rapidly to extremities
Rash formation process
Flat macules become papules, then vesicles followed by crust formation.
The crust is often shed off and heals without scarring.
Does cropping occur in varicella?
Characteristic feature of varicella rash , fresh vesicles appear in crops/groups , so all the stages can be seen simultaneously.
Reactivation for latent vzv
When the vesicles reactivate, intensive pains occur
VZV affecting eyes and face
Keratitis , Conjunctivitis & Iritis.
Bell’s Palsy
- causes a temporary weakness or paralysis of the muscles in the face.
- can occur when the nerve that controls your facial muscles becomes inflamed, swollen, or compressed.
Zoster of the seventh nerve ganglion can cause?
Bell’s Palsy
The clinical presentations of varicella or zoster are so characteristic that laboratory confirmation is rarely required (T/F)
True
Specimen for Varicella / Zoster
Smears from vesicular lesions , respiratory secretions .
Direct Virus Demonstration
Light Microscopy: Tzanck smear
Cytology: Cowdry’s A type intra nuclear inclusion bodies (Giemsa Stain)
Direct Immunofluorescence: Viral inclusion bodies in microscope - bright green + intranuclear
PCR: detection of viral DNA
Serology tests
Specific VZV Abs using ELISA ; CFT or Neutralisation test
Neutralization test
Used to quantify the titer of neutralizing antibody for a virus.
Serum antibody sample to be tested is diluted and mixed with a viral suspension.
This is incubated to allow the antibody to react with the virus.
DOC for vzv
Acyclovir , Famciclovir or Valacyclovir
Acyclovir does not affect Latency of vzv (T/F)
True
Prevention methods
- Active immunization-Live attenuated varicella vaccine Single dose .Children aged : 1- 10 years .
- Passive immunization-
Varicella Zoster Immunoglobulins ( VZIG )
Given to:
- Immuno compromised children exposed to infection.
- Mothers infected near term ( before delivery ) and their infants ( immediately after delivery).
Infection Control Measures
Patients infected with VZV should be kept in isolation ( Airborne & Contact Precautions )
Largest virus in Herpesviridae family is?
Cytomegalovirus - Size = 150 – 200 nm
Effect of Cytomegalovirus in host cells
- Causes massive enlargement of infected host cells
How does Cytomegalovirus present in healthy adults?
Asymptomatic infection
High risk group for Cytomegalovirus
- Organ transplant patient .
- HIV patients
Congenital CMV infection does not pose serious effect on foetus or new borne (T/F)
False; Congenital CMV infection may be fatal to foetus or new borne.
CMV transmission
in utero , perinatally or post natally
Infectious virions appear in urine & saliva from time to time (T/F)
True
CMV - mode of transmission
1- Close contact with most body fluids ( Saliva , urine , vaginal secretions & semen ).
2- Transplacental & Perinatal Transmission (Secondary to exposure to Infected birth canal ) & Breast feeding .
3- Sexually through semen & cervical secretions .
4- Blood transfusion .
5- Organ transplantation
Pathogenesis of CMV
First infects upper respiratory tract And lymphocytes .
During their circulation lymphocytes spread the virus to other lymphocytes & monocytes in spleen & lymph nodes.
Finally spread to a variety of epithelial cells of salivary glands , kidney tubules , testes & cervix.
What viral response maintains virus in latent state?
The virus elicits both humoral & cell mediated response that maintains virus in latent state.
Latent virus can reactivate with immunosuppression (T/F)
True
Congenital CMV
Perinatal (before and after birth)
Postnatal (after birth)
Immunocompromised CMV
- Transplant patients
- Cancer patients- chemotherapy
- HIV patients
CMV can cause mononucleosis type symptoms (T/F)
True
CMV mononucleosis type symptoms are the leading cause of morbidity and mortality
True
Heterophil Antibody Test- positive for CMV mononucleosis symptoms
( Heterophil Antibody Test- Negative )
Cytomegalic Inclusion Disease (CID)
Series of signs and symptoms caused by cytomegalovirus infection, toxoplasmosis or other rare infections such as herpes or rubella viruses.
It can produce massive calcification of the central nervous system, and often the kidneys.
Intrauterine infection :– Congenital CMV Infection -> Death
Hepatospenomegaly
Jaundice
Thrombocytopenic purpura (abnormal decrease in platelets)
Hemolytic anaemia (RBCs destroyed faster than they are made)
Microcephaly
Cerebral calcifiaction
High mortality
Mental retardation
Direct Virus Demonstration - CID
Light microscopy - Giemsa stain – owl’s eye cells; large, multinucleated
Direct immunofluorescence and ELISA – finding antigens
PCR (most rapid + sensitive) & Nucleic Acid Hybridization – Finding CMV DNA
Serology - CID
Panel of tests for TORCH
Culture - CID
Sample used is throat washing & urine . CMV grows in human fibroblast cell culture
After 3-5 weeks CPE{ Cyto- Pathic- Effect} with small foci of swollen transluscent cells with large intranuclear inclusions.
Ganciclovir - CID
Inhibits viral DNA polymerase enzyme
Intravenous route
DOC
Other drugs for CID
Valganciclovir (orally – immunocompromised) and Foscarnet (resistant)
Gangiclovir does not affect CID latency (T/F)
True
Prevention + control – CID
Good hygienic personal practice , careful hand washing after contact with diapers or oral secretions .
Safe sexual practice including usage of condom reduces transmission .
Isolation of infected new borne .
Screening of transplant donors & recipient for CMV antibodies .
Etiological agent
Materials known or reasonably expected to contain a pathogen
Etiological agent of infectious mononucleosis
Epstein Barr Virus
Which cells does EBV infect?
Infects lymphoid cells - B lymphocytes
EBV transmission
Saliva ( kissing disease ).
Rarely by blood or marrow transfusion . By
Sharing contaminated - Glasses , Cups & Tooth brushes.
Infectious mononucleosis - symptoms
High fever , sore throat , headache , myalgia , nausea & abdominal pain
Also associated with: pharyngitis , generalized lymphadenopathy , hepatosplenomegaly and fatigue
EBV Associated tumors/malignancies
Burkitt’s lymphoma – Africa - childhood (swelling of jaw - affects B lymphocytes).
Lymphoma – (Post –transplant lymphomas) in immunodeficient patients.
Nasopharyngeal carcinoma - Asia-Chinese.
Hodgkin’s lymphoma (non-painful enlarged lymph nodes in the neck, under the arm, or in the groin - affects WBCs)
Burkitt’s lymphoma
Cancer starts in immune cells called B-cells - fast growing human tumor
Post-transplant lymphoma
Can be a result of both solid organ transplant (kidney, lung, heart, liver, lung) and allogeneic bone marrow or stem cell transplants
Nasopharyngeal carcinoma
Rare tumor of the head and neck which originates in the nasopharynx
Hodgkin’s lymphoma
Cancer originates from a specific type of white blood cells called lymphocytes
Infectious mononucleosis - pathogenesis
Replicates in nasopharyngeal epithelium .
Spreads to salivary glands & oropharyngeal lymphoid tissue .
Further replication results in viraemia with subsequent infection of reticuloendothelial system , liver , spleen and B lymphocytes.
Host immune response include Cytotoxic T Lymphocytes (CTLs) - Characteristic Atypical Lymphocytes found in peripheral blood (whole blood).
How do this virus cause tumors?
DNA becomes integrated with the host chromosome giving the infected cell the ability to proliferate indefinitely resulting in malignancy / tumor .
Pathogenesis - EBV
Downey cells (abnormal lymphocytes) seen
Samples - EBV
Saliva , peripheral blood (P.S.) & lymphoid tissue
Tests EBV
Direct immunofluorescence
PCR and Nucleic Acid Hybridization :- For detection of viral DNA , most sensitive .
Direct immunofluorescence
Cell scrappings from lesions are stained with monoclonal antibodies conjugated with a fluorescence dye . Viral inclusion bodies appear in Microscope as a Bright Green Intranuclear particles
Monospot test ( horse RBCs ) / monospot test
Heterophil antibodies have the ability to agglutinate red blood cells of different animal species. The Paul-Bunnell test uses sheep erythrocytes( RBCs)
Serology - EBV
A) Detection of Non-specific Heterophil Antibodies:
Patients with Acute Infectious Mononucleosis develop transient non-specific Abs that agglutinate sheep RBCs / horse RBCs.
These are detected by Paul Bunnel or Monospot tests + ve.
B) Detection of specific antibodies by ELISA , Indirect Immunofluorescence:
Presence of IgM antibody to Viral Capsid antigen (VCA) – Suggest Acute Primary Infection . High IgG antibodies to VCA - Seen in Burkitt’s lymphoma , Nasopharyngeal carcinoma & Past infection .