Papillomaviruses

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Papillomaviruses
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Classification

• Widespread in nature, infecting many vertebrates
• Highly species specific
• 100 HPV types, classified basis on nucleic
  acid homology

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Human papillomavirus infections

• Transmission
• Direct contact with broken skin or mucosa
• Skin warts
• Genital tract HPV's
• Mucosal HPV's
• Various HPV types show tissue specificity

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HPV and skin warts
(From Fields Virology, 4th ed, Knipe Howley,
eds, Lippincott Williams Wilkins, 2001, Table
66-3.)
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Papillomavirus disease
From Medical Microbiology, 5th ed., Murray,
Rosenthal Pfaller, Mosby Inc., 2005, Fig. 52-4.
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Clinical genital tract and mucosal HPVs
(From Fields Virology, 4th ed, Knipe Howley,
eds, Lippincott Williams Wilkins, 2001, Table
66-4.)
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HPV16 genome
Genomic map of HPV-16. The genome is a
double-stranded circular DNA molecule of 7904
base pairs. Transcription occurs in a clockwise
manner the only transcriptional promoter
presently mapped for HPV-16 is designated P97.
The open reading frames deduced from the DNA
sequence are designed E1 to E7, L1, and L2 and
are indicated outside of the circular genome. AE
and AL represent the early and late
polyadenylation sites. The viral long control
region (LCR) contains transcriptional and
replication regulatory elements. (From Fields
Virology, 4th ed, Knipe Howley, eds, Lippincott
Williams Wilkins, 2001, Fig. 66-2.)
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Papilloma virus gene function
(From Fields Virology, 4th ed, Knipe Howley,
eds, Lippincott Williams Wilkins, 2001, Table
66-1)
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Papillomavirus replication and differentiation of
the epidermis
Differentiation of normal cutaneous squamous
epithelium and papillomaviral activities in
productively infected benign lesions. The various
epithelial strata and the host-differentiation,
stage-specific, gene-expression profile are
indicated in the left and center panels. (From
Fields Vriology (2007) 5th edition, Knipe, DM
Howley, PM, eds, Wolters Kluwer/ Lippincott
Williams Wilkins, Philadelphia Fig. 62.5.)
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Papillomavirus replication
Replication cycle of a papillomavirus. To
establish a wart or papilloma, the virus must
infect a basal epithelial cell. Our knowledge is
limited about the initial steps in the
replication cycle such as attachment (1), uptake
(2), endocytosis (3), and transport to the
nucleus and uncoating of the viral DNA (4).
Early-region transcription (5), translation of
the early proteins (6), and steady-state viral
DNA replication (7) all occur in the basal cell
and in the infected suprabasal epithelial cell.
Events in the viral life cycle leading to the
production of virion particles occur in the
differentiated keratinocyte vegetative viral DNA
replication (8), transcription of the late region
(9), production of the capsid proteins L1 and L2
(10), assembly of the virion particles (11),
nuclear breakdown (12), and release of virus
(13). (From Fields Virology, 4th ed, Knipe
Howley, eds, Lippincott Williams Wilkins, 2001,
Fig. 65-6.)
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Papillomavirus pathogenesis
From Medical Microbiology, 5th ed., Murray,
Rosenthal Pfaller, Mosby Inc., 2005, Fig. 52-3.
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Cervical HPV infection
Natural history of cervical HPV infection.
Approximate number of US cases of the different
categories of infeciton. Most subclinical
infections and low-grade dysplasias regress
spontaneously. Even high-grade dysplasia has
some potential to regress spontaneously.
Infection with HPV-16 or HPV-18 represents a
minority of the subclinical infections and
low-grade dysplasias, whereas they represent most
of the high grade dysplasias and invasive
cancers. (From Fields Vriology (2007) 5th
edition, Knipe, DM Howley, PM, eds, Wolters
Kluwer/ Lippincott Williams Wilkins,
Philadelphia Fig. 62.18.)
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HPV and cervical dysplasia
Progression from benign cervical condylomatous
liesion to invasive carcinoma. Infection by
oncogenic HPV types, especially HPV16, may
directly cause a benign condylomatous lesion,
low-grade dysplasia, or sometimes even an early
high-grade lesion. Carcinoma in situ rarely
occurs until several years after infection. It
results from the combined effects of HPV genes,
particularly those encoding E6 and E7, usually
after integration of the viral DNA into the host
DNA and a series of genetic and epigenetic
changes in cellular genes. HSIL, high-grade
squamous intraepithelial lesion, LSIL, low-grade
squamous intraepithelial lesion CIN, cervical
intraepithelial neoplasia. (From Fields Vriology
(2007) 5th edition, Knipe, DM Howley, PM, eds,
Wolters Kluwer/ Lippincott Williams Wilkins,
Philadelphia Fig. 62.16.)
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Cervical dysplasia
Low-grade squamous intraepithelial lesions of the
cervix. A Histologic section showing koilocytes
with vacuolated cytoplasm and parakeratosis (HE,
234). B The darkly stained nuclei contain
papillomavirus capsid antigen. Immunoperoxidase
stained with genus-specific antiserum (HE,
234). C Cervical smear. The squamous
epithelial cells are rounded. They occur in
clumps and display koilocytic changes
(Papanicolaou stain HE 375). D Cervical
smear. The darkly stained nuclei contain
papilloamavirus capsid antigen. (Immunoperoxidase
staind with genus-specific antiserum HE, 750).
(From Fields Virology, 4th ed, Knipe Howley,
eds, Lippincott Williams Wilkins, 2001, Fig.
66-5.)
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Papillomavirus cytology
Papanicolaou stain of the exfoliated
cervicovaginal squamous epithelial cells showing
the perinuclear cytoplasmic vacuolization, termed
koilocytosis (vacuolated cytoplasm), which is
characteristic of human papillomavirus
infection.(From Medical Microbiology, 5th ed.,
Murray, Rosenthal Pfaller, Mosby Inc., 2005,
Fig. 52-5. )
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Correlation between HPV type, integration, and
histology
(From Cullen, A.P., Reid, R., Campion, M.,
Lorincz, A.T (1991), "Analysis of the physical
state of different human papillomavirus DNAs in
intraepithelial and invasive cervical neoplasm",
Journal of Virology, vol. 65, p. 606-612, Fig. 4)
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HPV DNA integration into a human chromosome
Structure of the single copy of HPV-16 DNA
integrated into the SiHa cell line derived from a
cervical carcinoma. The jagged line represents
human chromosomal sequences the nucleotide
numbers pertain to the integrated HPV-16 genome.
The open boxes indicate the early and late open
reading frames (ORFs). Integration has occurred
in the E2 ORF, and a portion of the E2 ORF has
been deleted. (From Fields Virology, 4th ed,
Knipe Howley, eds, Lippincott Williams
Wilkins, 2001Fig. 66-9.)

• Integration leads to up-regulation of E6 and E7
• Inactivation of E2
• Host transcription elements
• Host sequences stabilize mRNA

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Diagnosis

• Pathology, cytology
• Immunohistochemistry
• Nucleic acid
• Hybridization (Southern, in situ), PCR
• Identification of specific HPV type can assist in
  evaluating prognosis and treatment
• Integration state?

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Prevention/Treatment

• Recombinant virus-like particle vaccines
• Gardasil
• FDA approved HPV 16, 18, 6, 11
• Cervarix
• FDA approval pending HPV 16, 18
• Pap smear
• Surgery

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Summary human papillomavirus

• Structure
• Small (8 kb) circular dsDNA genome, naked capsid
• Pathogenesis
• transmission by direct contact or sexual skin,
  mucosa
• replication in nucleus of basal cells of
  epithelium very host dependent coupled to
  epithelial differentiation
• no spread
• primarily cellular immune response
• transforming infection warts are tumors
  cervical carcinoma
• Diagnosis
• cytology (PAP smear koilocytosis)
• immunohistochemistry
• nucleic acid
• Prevention/treatment
• recombinant subunit (VLP) vaccine
• PAP smear
• surgery