Papovaviridae Powerpoint

PAPOVA VIRIDAE Dimatatac - Escovidal Esparagoza - Espinosa Fernandez - Fernandez - Flores Galapon - Gelonga - Gigataras

INTRODUCTION

Papovaviridae Family -

Originally Papovaviridae family

-

Later on, split into two separate families: Papillomaviridae and

Polyomaviridae -

Papillomaviruses encode all its genes in only one strand (Polyomaviruses do not)

Papillomaviruses

Papillomaviruses ● Small, non-enveloped, epitheliotropic, double-stranded DNA viruses ● Infect mucosal and cutaneous epithelia ○ Manifests as skin warts, plantar warts, anogenital warts, laryngeal papillomas

● Can induce cell proliferation ○ HPV 16 & 18 = 70% of Cervical Cancers worldwide ○ Cancer in anogenital and oropharyngeal regions

Human Papillomavirus (HPV) More than 100 types specified HPVs, 50% are found to infect the genital

tract

HPV 16 & HPV 18 ⇩ 70% of Cervical Cancers 61.1% invasive cervical cancers (Bruni et al, 2015)

“...most common type of

sexually-transmitted infection (STI) both in men and women in the United States.” (CDC, 2014)

History of Papillomaviruses -

Early 20th century (1930s) Richard Shope Transmission of horn-like skin warts, or

papillomas, between infected rabbits -

Warts were taken, ground, and then

-

injected into healthy rabbits → they acquired the same kind of warts as those of the infected rabbits German virologist: Harald zur Hausen -

HPV, 1976

Polyomaviruses

Polyomaviruses ● Small, non-enveloped DNA viruses ● ‘Polyoma’ - many tumors ● Known to produce tumors, but usually not in their natural hosts ○ Polyomavirus Simian Virus 40 (SV40) produces lymphocytic leukemia and reticuloendothelial cell sarcomas in hamsters, but is not oncogenic in monkeys (natural host)

Polyomaviruses JC Virus*

Progressive multifocal leukoencephalopathy

BK Virus*

Hemorrhagic Cystitis (BM transplant patients), Polyomavirus-associated nephropathy (Renal transplant)

KI Virus & WU Virus

Respiratory infections

Merkel Cell Virus

Merkel Cell Carcinoma

HPyV6 & HPyV7

Common constituent of human skin

SV40

Monkeys are the natural hosts *Both JC and BK Viruses cause human disease

History of JC Virus - James Cunningham -

Patient from whom the first JC virus was isolated

Harmly to most people but fatal to

immunocompromised patients -

Hodgkin’s Disease & PML was JC’s first diagnosis - Postmortem Brain Tissue: JC Virus was discovered -

Gabriele M. Zu Rhein & colleagues

History of BK Virus - 1970 - Incidental discovery - Papovavirus particles in urine sample of patient BK 4 months after renal transplantation

CHARACTERISTICS

Polyomaviruses & Papillomaviruses ➢ ➢

share similarities in morphology, nucleic acid composition, and transforming capabilities differences in genome organization and biology

Structure Virion

Icosahedral

Composition

DNA (10%), protein (90%)

Genome

Double-stranded DNA, circular

Proteins

Structural proteins; cellular histones

Envelope

None (naked)

Replication

Nucleus

Structure

Polyomaviruses

Papillomaviruses

Size (Diameter)

45 nm (smaller)

55 nm (larger)

Genome

5 kbp; open reading frames on two DNA strands

8 kbp; open reading frames on same DNA strand

Proteins

3 structural proteins

2 structural proteins

Genome ❖ Polyomavirus ➢ ➢

Encode early and late genes EARLY: encode large, middle

or small T antigens ➢

LATE: structural capsid proteins, VP1, VP2, and VP3

Genome ❖ Polyomavirus ➢

Early region is expressed soon

after infection ➢

➢

T antigens are continuously synthesized for transformation of cells Late region consists of genes coding for synthesis of coat proteins, which are not

expressed in transformed cells

Replication ❖ Polyomavirus ➢

Dependent on the host cell transcription and replication machinery

➢

Takes place in the nucleus of infected cells, where cellular

enzymes utilized for viral DNA synthesis are available

Replication ■

RNA polymerase - performs transcription of early genes leading to the synthesis of early

proteins ■

DNA polymerase - synthesizes DNA genomes for progeny viruses

➢

Capsid proteins are translocated in the nucleus then released upon cell death

Genome ❖ Papillomavirus ➢

Encode early and late genes

➢

7 or 8 early genes (E1-E8)

➢

2 late structural capsid genes (L1 and L2)

Replication ❖ Papillomavirus ➢ Difficult to appreciate because of lack of studies in culture system ➢ Lacks own transcription and replication machinery ➢ Highly tropic for epithelial cells of skin and mucous membranes

Replication ❖ Papillomavirus ➢ Late gene expression synthesis of late capsid proteins in infected

keratinocytes ➢ Virus assembly in nucleus followed by release via cell lysis

Replication ❖ Papillomavirus ➢ Infects basal stem

cells and the virus is

➢ ➢

internalized and uncoated Viral DNA is brought into the nucleus Host RNA polymerase transcribes early genes followed by synthesis of early proteins

Replication ❖ Papillomavirus ➢ Host DNA polymerase directs viral DNA synthesis i. Lower epidermis multiple copies of viral DNA for latent infection ii. Differentiated epithelial cells vegetative DNA replication

Oncoproteins and Cellular Protein Interactions ➢

Viral proteins interact with cellular tumor suppressor proteins to promote cell growth

Virus

Viral Oncoproteins

Cellular Targets

Polyomavirus SV40

Large T antigen Small t antigen

P53, pRb, PP2A

Human papillomavirus

E6

P53, DLG, MAGI-1, MUPP1

E7

pRb

Bovine papillomavirus

E5

PDGFβ receptor

Oncoproteins and Cellular Protein Interactions ➢

Interactions of T antigen with the cellular proteins are important in the replicative cycle of the virus

Inactivate growthinhibitory properties of cellular proteins

Cells enter S phase (DNA replication)

Virus-mediated transformation

DNA damage

Tumor suppressor proteins promote apoptosis

Virus binds, cell will not die and will continue to replicate

Immortal cells

CANCER

PATHOGENESIS

Virulence Factors ❖ Papovavirus ➢ ➢

Resistant to treatment with acids, alcohol, and ether Oncogenicity - due to inactivation of cellular tumor suppressor genes ■ Papillomavirus ● Early genes E6 and E7 ■ Polyomavirus ● Large T antigen and small t antigen

Virulence Factors ❖ Papillomavirus ➢

➢

Early genes E6 and E7 interact with tumor suppressor genes of host cells p53 and pRb - to allow tumor growth ■ E6 increases degeneration of p53 ■ E7 interacts with p105Rb, a retinoblastoma protein that prevents excessive cell growth Extrachromosomal DNA as the viral genome ■ Persistence of viral DNA in dividing cells

Virulence Factors ❖ Polyomavirus ➢

➢ ➢

Early genes large T antigen and small T antigen targets p53, pRb, and PP2A - inactivation of tumor suppressors ■ Large T antigen interacts with p53 and pRb ■ Small T antigen interacts with PP2A, a tumor suppressor for blood cancers Reactivation in immunocompromised individuals Reactivation in patients treated with rituximab and natalizumab

Mode of transmission ❖ Papillomavirus ➢ Skin-to-skin contact ➢ Causes cutaneous and mucosal infection leading to warts ➢ Viral particles spread from papillomatous lesions of the infected to other sites or hosts, inducing a proliferation in their basal cell

layers ➢ Being sexually active, especially at a young age, increases risk of genital HPV infection and cervical cancer

Mode of transmission ❖ Papillomavirus ➢ Age as a risk factor for infection ■ Cervical cancers have been shown to originate from a squamocolumnar junction at the cervix where metaplastic changes are continuous ■ Greatest metaplastic changes during puberty, first pregnancy and declines after menopause

Mode of transmission ❖ Polyomavirus ➢ ➢ ➢ ➢ ➢

➢

Often acquired during childhood Persist in the kidneys and lymphoid tissues as primary infection May reactivate when infected individual is immunocompromised Triggered by renal transplantations, pregnancy, increasing age etc. BK virus ■ Hemorrhagic cystititis in bone marrow transplants ■ Nephropathy, graft failure and obstruction of ureter in renal transplant recipients JC virus ■ Progressive multifocal leukoencephalopathy to those with weak CMI due to immunosuppressive therapies or AIDS

CLINICAL SIGNIFICANCE

Diseases ❖ Human Papillomavirus (HPV) ➢ ➢

Transmitted through sexual contact Infection results in three manifestations ■ Anogenital warts ● Formation of warts along the genitalia ● Self limiting; Resolves on it’s own. ■ Latency ■ Active infection ● Neoplasia leading to cancer (Commonly cervical cancer)

Diseases ❖ JC Virus ➢ ➢ ➢ ➢

Polyomavirus Mode of transmission has yet been established Known to reside in the lymph nodes in infected individuals Progressive Multifocal Leukoencephalopathy ■ Causes damage to the oligodendrocytes of the brain

Diseases ❖ BK Virus ➢ ➢

Route of transmission has yet been established Has been linked in cases concerning the brain, eyes, liver, kidney and lung ■ Proven to be associated only in kidney problems ■ Can cause Hemorrhagic Cystititis and Nephritis ■ Can cause Graft rejection in kidney transplant patients.

Medical Importance in the Philippines ❖ Human Papilloma Virus (HPV) ➢ ➢ ➢ ➢ ➢ ➢ ➢ ➢

Men are both carriers and vectors 660 million people worldwide infected; most common reproductive tract viral infection Peak incidence: adolescents and young adults Linked to 99% of cervical and 80% of anal cancer cases Remains a major health concern for Filipinos Women are at a health and mental risk 12 women die of cervical cancer every day 6000 new cases every year with more than half expected to die within 5 years

LABORATORY DIAGNOSIS

Laboratory Diagnosis ❖ Human Papillomavirus (HPV) ➢ ➢ ➢

Does not grow in routine tissue culture Antibody tests rarely used ■ results remain positive after 1st HPV genotype infection Routine Papanicolaou (Pap) Smear ■ Primary method for detection of HPV ■ Primary screening test for cervical cancer ■ Screening tool for changes in cells of the transformation zone of cervix (poikilocytosis of vaginal or cervical epithelium) ■ CPE prompts colposcopy (confirmatory test)

Laboratory Diagnosis ❖ Human Papillomavirus (HPV) ➢

➢

Colposcopy ■ Confirmatory procedure done using colposcope ■ Examination of cervix, vagina and vulva after application of 3% acetic acid solution (stain patterns of dysplasia and carcinoma) ■ Greater abnormalities, more severe infection ■ Allows for tissue sampling/biopsy Biopsy ■ Confirmatory method by observing histopathologic features like acanthosis and koilocytosis, pathognomonic of HPV

Laboratory Diagnosis ❖ Human Papillomavirus (HPV) ➢

➢

Use of immunoassays and PCR to detect specific viral DNA ■ more sensitive than Pap smear ■ Labor-intensive, time consuming, low-sensitivity US-FDA Detection Tests: HC High-Risk test, HC Low-Risk HPV test, Cervista HPV 16/18 test, Cervista HPV High-Risk test

Laboratory Diagnosis ❖ Polyomavirus ➢ ➢ ➢ ➢

Clinical presentation & Antibody presence = Best means of diagnosis Viral DNA can be detected in suspect tissues by PCR or nucleic acid hybridization Tissues and body fluids may be examined by electron microscopy to detect papovavirus particles The hemagglutination-inhibition test is useful for serodiagnosis of JC and BK virus infections

Laboratory Diagnosis ❖ Renal Tract Infections ➢ ➢

Cytological examination for inclusion-bearing cells, EM and virus isolation = method used to detect polyomavirus in the URINE inclusion bearing cells: have a characteristic appearance and are often present in large numbers

❖ Serological Diagnosis ➢ ➢

HAI = most widely used serological technique for measuring antibodies against the polyomaviruses CFT, neutralization, ELISA and RIAs have also been used

Laboratory Diagnosis ❖ BK Virus ➢ ➢ ➢ ➢ ➢

Urine of patients excreting polyomaviruses may contain “decoy” cells similar to those of cytomegalovirus, but can be distinguished cytologically. BK Virus can be isolated by culture in diploid fibroblast or Vero monkey kidney cells Neuropathy is preceded by plasma PCR positivity Only kidney biopsy is available for definitive diagnosis Immunoassays for viral antigen detection

❖ JC Virus ➢

PCR of CSF is a diagnostic test for PML (Progressive Multifocal Encephalopathy)

TREATMENT PREVENTION & CONTROL

Papillomavirus ❖

❖

Preventive Measures ➢ Health Education ➢ Contraception ➢ Proper sterilization ➢ Proper Hygiene Vaccination ➢ Gardasil ➢ Gardasil 9 ➢ Cervarix

Papillomavirus ❖

Treatment ➢ Medication ❏ ❏

➢

Immune Response Modifiers Cytotoxic Agents

Surgery ❏ ❏ ❏ ❏

Cryosurgery Electrosurgery Carbon Dioxide Laser Therapy Surgical Excision

Polyomavirus ❖

BK Virus ➢ Prevention ❏ Detection of BKV DNA in blood or Urine ❏ Reduction of Immunosuppression ➢ Treatment ❏ Medication- Leflunomide ❏ Bladder Irrigation

Polyomavirus ❖

JC Virus ➢ Increases continuously in some individuals but clinically silent unless immunosuppression occurs. ➢ Prevention is best done through immunosurveillance and immune system strengthening ➢ No specific therapy existing yet but Anti-retroviral therapy is being advised for reversal of immunosuppression

REFERENCES ● ●

Butel, J. S. (n.d.). Chapter 66 Papovaviruses. Retrieved April 04, 2016, from http://www.ncbi.nlm.nih. gov/books/NBK7644/ Brooks, G., Jawetz, E., Melnick, J., & Adelberg, E. (2013). Jawetz, Melnick & Adelberg's medical microbiology. New York: McGraw-Hill Medical.

●

Delos Reyes, R. (2014). Expert says HPV infection may cause genital warts and cervical cancer. Retrieved 03 April 2016 from http://www.msd.com.ph/Newsroom/Pages/Expert-says-HPV-infection-may-cause-genital-warts-and-cervical -cancer.aspx

●

Laboratory Diagnosis of Polyomaviruses Infection, Detection of Polyomavirus Infection. (n.d.). Retrieved April 04, 2016, from http://virology-online.com/viruses/polyomaviruses4.htm