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. Learning Objectives
Be familiarized with all human herpesviruses and their associated diseases.
Know herpesvirus replication cycle and latency-reactivation cycle.
Know the infection cycles and pathogenesis of HSV-1, HSV-2, VZV, HCMV, EBV.
Know anti-herpesvirus drugs and their mechanisms of action

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

5. Classification of herpesviruses
Family
Herpesviridae
Subfamily
Alphaherpesvirinae
HSV-1
HSV-2
VZV
..…. (animal viruses)
Betaherpesvirinae
HCMV
HHV-6A
HHV-6B
HHV-7
…...(animal viruses)
Gammaherpesvirinae
EBV
KSHV
Species
There are 9 currently known human herpesviruses

6. Size of herpesviruses
Principle of Virology

7. Herpesvirus structural components
Spherical, nm in diameter
dsDNA genome ( kb)，encoding protein
Capsids have icosahedral symmetry
There is a tegument and an envelope
Envelope proteins
Envelope
dsDNA
Tegument
Capsid

8. Types of herpesvirus infections
Herpesviruses can typically undergo the following three types of infections:
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
HSV-1, HSV-2, VZV, HCMV can also undergo congenital infections (mother to child transmission during pregnancy or birth)
HHV-6A and HHV-6B can undergo integrated infection.

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

10. HSV replication cycle
Principles of Virology

11. Human herpesviruses Wikipedia.org 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-6A and 6B
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
Wikipedia.org

12. Cytopathic effects of herpesviruses
HSV in Hep-2 cells
VZV in human kidney cells
HCMV in human fibroblasts
HCMV in human fibroblasts
Medical Microbiology

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

14. 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)
multinucleate cell with dark
staining inclusions
Plaque

15. 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 15

16. Transmission and primary infection
– Transmission by direct touch or sex (HSV-2 mostly by sex)
– cytolysis
– Blisters in the skin
Congenital infection
Mother to baby transmission through placenta
Principles of Virology

17. HSV Latency and reactivation
• Latent infection
– latently infected ganglia in a non-replicating state
– HSV-1, trigeminal ganglia(三叉神经节);
– HSV-2, sacral ganglia(骶神经节)
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.
Latency/reactivation cycles are with you LIFE TIME.

18. HSV life cycle
Field’s Virology, 6 edition

19. Diagnosis Cell culture: often use Vero cells (plaque assay)
Serology: Specific IgM indicates recent infection
Viral antigen detection: Scrape off damaged tissue. Use antibodies to detect viral antigens
PCR: most sensitive and widely used.
Sample:
10-4
Viral titers:
plaque forming unit (pfu)/ml
10-5
10-6
Plaque assay

20. Plaque assay
Viral titers: plaque forming units/milliliter (pfu/ml)

21. 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

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

23. Biological properties
Similar to HSV
Replicates in fibroblast or epithelial cells
Form multinucleated giant cells and Cowdry type A inclusion bodies, like HSV

24. Chicken pox
99.5% of people are seropositive
Principles of Virology

25. Shingles Chicken pox as a child
Virus establishes latency in dorsal root ganglia or trigeminal ganglia
背根神经节
三叉神经节
Replicate in skin
10-20% of cases
After adulthood, when stimulated
Travel along Axons of sensory neuron to skin
Reactivated
VZV reactivation occurs more frequently in immuncompromised persons and in the elderly
A decline in VZV-specific T-cell levels may allow the virus to reactivate

26. Congenital Varicella syndrome
(先天性水痘综合征)
• Caused by infection early during pregnancy
• Affect skin, limbs, eyes and brain

27. Diagnosis and intervention
Symptoms are typical. Usually no need of lab tests.
IgM, PCR
Treatment
Acyclovir
Vaccine
Live attenuated vaccine virus
VZV-Ig for emergency prevention (like for immunocompromised patients)
VZV特异性免疫球蛋白

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

29. Biological properties of HCMV
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”)
H&E stain of lung section showing owl’s eye inclusions

30. HCMV 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
Principles of Virology

31. Outcomes of HCMV infections
60-90% of adults are seropositive
Infection of healthy children and adults
Usually a lifelong and subclinical infection
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
视网膜炎
脑膜炎 肺炎
结肠炎
HCMV retinitis

32. Diagnosis and intervention
Laboratory diagnosis
Cell culture
PCR
Tests of pp65 antigen in peripheral blood leukocytes
Serology: ELISA for CMV-specific IgM indicates active infection
Treatment and prevention
Ganciclovir （更昔洛韦）
Foscarnet（膦钾酸）
No vaccine, but under development

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

34. Lytic and latent infection of EBV
>90% of people are infected with EBV during childhood
Lytic infection occurs during primary infection of oropharyngeal epithelial cells or during reactivation from latency in B cells.
Latent infection occurs in B cells.
Latent infection by EBV can transform and immortalized B cells, and occasionally results in malignancies. 口咽

35. 激活
潜伏感染B细胞
B cell transformation and cancer

36. Diseases related to EBV infection
Primary infections in children are usually subclinical, but if they occur in young adults, acute infectious mononucleosis (polyclonal stimulation of lymphocytes: fever, sore throat, enlarged lymph nodes in the neck, and feeling tired) often developes.
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.

37. Diagnosis and intervention of EBV infection
Serology: Detect EBV-specific antibody (mainly IgM) in the serum.
Heterophile antibody test: Heterophile antibodies are antibodies induced by external antigens that can also cross-react with self-antigens
PCR test for viral DNA
No drugs or vaccines are available for Epstein-Barr virus.

38. Pathogens of congenital (vertical) infections

39. Herpesviruses are a global burden of infection