1. Herpesviruses Dongli Pan
Herpes comes from Greek word “herpein”（to creep or crawl）
Herpesviruses
Dongli Pan
Department of Medical Microbiology and Parasitology
Zhejiang University School of Medicine

2. Recommended reading

3. Classification Herpesviridae Alphaherpesvirinae HSV-1 HSV-2 VZV
..…. (animal viruses)
Betaherpesvirinae
HCMV
HHV-6
HHV-7
…...(animal viruses)
Gammaherpesvirinae
EBV
KSHV
There are 8 currently known human herpesviruses

4. Baltimore classification
DNA viruses
RNA viruses
Baltimore classification
Fields Virology, 6th edition

5. Viruses are small
Principle of Virology

6. Common features
1.Shape and structure：spherical, nm in diameter, dsDNA genome ( kb，encoding proteins）；Capsids have icosahedral symmetry. There is a tegument and an envelope

7. 2. Viral replication: Replication and assembly of viral capsids occurs in the nucleus.
3.Immunity: The viruses encode multiple proteins to evade and manipulate host immunity. Host immunity can control productive infection, but cannot prevent establishment of latency, nor can eliminate latent virus.
4. Types of infection
All herpesviruses
a. Primary infection: viral replication and cytolysis
b. Latent infection: No viral replication, DNA genome remains in host for the life time of host
c. Recurrent infection: viral replication after reactivation
Some herpesviruses
d.Congenital infection：HSV-1, HSV-2, VZV, HCMV
e.Integrated infection：HHV-6, occasionally in EBV

8. Replication cycle
HSV-1

9. Biological Cycle of Herpesviruses
(Including congenital infection)
Primary Infection
Establish latency
Latent infection
Productive (lytic) infection
Reactivation
Establish latency
Recurrent Infection

10. Human herpesviruses Subfamily Virus Species Primary Target Cell
Site of Latency
Means of Spread
Diseases α
herpesvirinae
HSV-1
(HHV-1)
Mucoepithelial cells
Neuron
Close contact
Cold sores, gingivostomatitis
Herpetic keratitis, Encephalitis
HSV-2
(HHV-2)
Close contact ( sexual transmission)
Genital herpes
VZV
(HHV-3)
Respiratory and close contact
Chicken pox, Shingles β
HCMV
(HHV-5)
Monocyte, lymphocyte, and epithelial cells
Monocyte, lymphocyte, and ?
Close contact transfusions, tissue transplant, congenital
Infectious mononucleosis, Retinitis,
Diseases for newborn and immunocompromised
HHV-6
T cells and ?
Roseola, Others?
HHV-7 ? γ
EBV
(HHV-4)
B cell and epithelial cell
B cell
Saliva ( Kissing disease )
Infectious mononucleosis, nasopharyngeal carcinoma,
Burkitt’s lymphoma
malignant lymphoma
KSHV
(HHV-8)
Lymphocyte and other cell
Close contact (sexual), saliva?
Kaposi’s sarcoma

11. Herpesviridae Herpes Simplex Virus (HSV) • HSV-1 (HHV-1)

12. Biological properties
Spherical, nm, 150 kb dsDNA
Can be easily propagated in many cell lines (most commonly Vero cells)
Form visible plaques, multinucleated giant cells and Cowdry type 1 inclusion bodies (acidophilic nuclear inclusion bodies)
Animal models: mouse, rabbit, Guinea pig.
multinucleate cell with dark
staining inclusions
Plaque

13. Diseases caused by HSV HSV-1 HSV-2 Cold sores
Herpetic gingivostomatitis
Herpetic keratitis
Herpes simplex encephalitis (70% fatality rate)
Neonatal herpes
Genital herpes, can be caused by HSV-1 too)
Herpetic meningitis
Neonatal herpes 13

14. Pathogenesis • Primary infection Congenital infection
– Transmission by direct touch or sex
– cytolysis
– Blisters in the skin, ulcer in the eye, or swelling of brain tissues
Congenital infection
Mother to baby transmission through placenta
It can lead to abortion, premature delivery, stillbirth, malformation, or encephalitis

15. Reactivation and recurrent infection
• Latent infection
– The virus establishes a non-replicating state in sensory neurons
– HSV-1, trigeminal ganglia
– HSV-2, sacral ganglia, also HSV-1
Reactivation and recurrent infection
Triggers: fever, emotional stress, fatigue, menstruation, immunosuppression, etc.
The virus starts to replicate and travels back to peripheral tissues, resulting in recurrent infection.

16. HSV latency and reactivation
Field’s Virology, 6 edition

17. Diagnosis Approach Test/Comment
Tzanck test: Direct microscopic examination of cells from base of lesion
Multinucleated giant cells and cowdry type A inclusion bodies.
Cell culture (gold standard)
Inoculate Vero, BHK-21 cells, etc. HSV replicates and cause identifiable cytopathic effects (CPE): see plaques.
Assay of tissue biopsy, smear, cerebrospinal fluid, or vesicular fluid for HSV antigen or genome
ELISA, immunofluorescent stain, in situ hybridization and PCR
Serology
Specific IgM indicates recent infection

18. HSV Thymidine Kinase (UL23)
Treatment and prevention
Acyclovir (or similar nucleoside analogs and their derivatives)
Foscarnet
No vaccine yet. N HN
H2N
CH2 O
HO-CH2
Acyclovir, a nucleoside analog,
inhibits viral DNA polymerase
Acyclovir (ACV) N HN
H2N
CH2 O
HO-CH2
HSV Thymidine Kinase (UL23)
ATP N HN
H2N
CH2 O
P-O-CH2
ATP
ATP N HN
H2N
CH2 O
P-P-P-O-CH2
Inhibit HSV DNA
polymerase
Cellular kinases

19. Herpesviridae
Varicella-Zoster Virus (HHV-3)

20. Biological properties
Similar to HSV
Has only 1 serotype
Replicates in fibroblast or epithelial cells
Form multinucleated giant cells and Cowdry type A inclusion bodies, like HSV
But no working animal model

21. VZV primary infection (Chicken pox)
Droplets, direct contact
Enter through respiratory system, conjunctiva or skin, etc
Skins of whole body
Second Viremia
Proliferate in local lymph node
Proliferate in mononuclear phagocyte system in spleen and liver
First Viremia

22. VZV latency and reactivation: Shingles
Chicken pox as a child
Virus establishes latency in dorsal root ganglia or trigeminal ganglia
Replicate in skin
10-20% of cases
Travel along Axons of sensory neuron to skin
After adulthood, reactivated
VZV reactivation occurs more frequently in immuncompromised persons and in the elderly
Host immunity may help maintain latency

23. Congenital Varicella syndrome
• Caused by infection in utero
during the first trimester
• Leads to scarring of the skin of
the limbs, damage to the lens,
retina and brain

24. Diagnosis and intervention
Symptoms are typical. Usually no need of lab tests.
Tzanck test: Staining of samples scraped from the base of a vesical and look for multinucleated giant cells, Cowdry type A inclusion bodies, etc.
Treatment
Acyclovir
Vaccine
Live attenuated vaccine virus
VZV-Ig for emergency prevention (like for immunocompromised patients)

25. Herpesviridae
Human cytomegalovirus (HCMV, HHV-5)

26. Biological properties
Spherical, nm.
HCMV only infects human cells. Fibroblast cells are used for propagation. It replicates slowly.
Infected cells become enlarged and form owl’s eye inclusion bodies (big acidophilic nuclear inclusions with the appearance of an “owl’s eyes”)
Resistance is weak. Long term storage requires liquid nitrogen.
H&E stain of lung section showing owl’s eye inclusions

27. Modes of transmission
Direct contact: Sexual transmission, mouth to mouth, hand to mouth
Vertical transmission: transplacental, intrauterine infection, cervical secretions, milk, saliva, etc
Medical procedures: Blood transfusion, organ graft
60-90% of adults are seropositive

28. Outcomes of HCMV infections
Infection of healthy children and adults
Usually a lifelong and subclinical infection (60-90% of people are seropositive)
Primary infection can lead to infectious mononucleosis
Congenital infection
HCMV infection is the leading cause of infectious congenital disease
Infection of CNS can cause neurological abnormalities and death
Neonatal infection
Virus reactivated during delivery
Usually protected by mothers’ antibodies
Infection of immunosuppressed individuals
Transplant recipients and AIDS patients
Severe complications including retinitis,
Meningitis, pneumonia, colonitis
90% in North America
HCMV retinitis

29. Diagnosis and intervention
Laboratory diagnosis
Cell culture
qPCR
Tests of pp65 antigen in peripheral blood leukocytes
Serology: ELISA for CMV-specific IgM indicates active infection, but may give false-positives
Treatment and prevention
Ganciclovir
Foscarnet
No vaccine, but under development

30. Herpesviridae
Epstein- Barr Virus (HHV-4)

31. Biological properties
Typical herpesvirus morphology and structure, 180 nm in diameter.
Cannot be grown in normal cell culture.
Lytic infection of EBV usually occurs during primary infection of oropharyngeal epithelial cells or during reactivation from latency in B cells. Important lytic antigens include: early antigen (EA), viral capsid antigen (VCA) and membrane antigen (MA)
Latent infection mostly occurs in B cells. During latent infection limited viral antigens are expressed. They include EB nuclear antigen (EBNA) and latent membrane protein (LMP)
Latent infection by EBV can transform and immortalized B cells, and occasionally results in malignancies. EBNA-2, EBNA-3C and LMP-1 antigens are essential for transformation.

32. Pathogenesis Transmitted mainly by saliva
Replication in oropharyngeal epithelial cells
Infects B cells in the local lymphatic system
Spread throughout the body in B cells
Latent infection of B cells (lifetime)
B cells are transformed resulting in malignancies.

33. Diseases related to EBV infection
Infectious mononucleosis (mostly caused by primary infection, fever, sore throat, enlarged lymph nodes in the neck, and feeling tired)
Nasopharyngeal carcinoma (Guangdong, China; areas in southeast Asia)
Burkitt's lymphoma (Africa)
Malignant lymphoma
A conjunctival hemorrhage of the right eye
of this patient with infectious mononucleosis.
Burkit’s lymphoma.

34. Diagnosis and intervention
Heterophile antibody test: rapid test for antibodies induced by EBV infection. It’s diagnostic for infectious mononucleosis.
EBV-specific antibody test
PCR test for viral DNA
No drugs or vaccines are available for Epstein-Barr virus.

35. Pathogens of vertically transmitted infections