Adenoviruses, parvoviruses, and papillomaviruses

what are some enveloped DNA viruses?

poxvirus, herpesvirus, hepadnavirus

what are some naked capsid DNA viruses?

polyomavirus, papillomavirus, adenovirus, parvovirus

fast facts about adenoviruses

first isolated in 1953 from explant culture of human adenoid tissue, over 60 different serotypes of adenoviruses have been discovered in humans and can cause infections and disease in a variety of tissues and organs, adenoviral vectors have been developed for use as vaccine and gene therapy vectors

what is the structure of adenoviruses?

relatively resistant to inactivation, non-enveloped, icosahedral nucleocapsid, dsDNA genome (~35kbp), >60 serotypes

how do adenoviruses replicate?

replicates its genome using its own viral polymerase and assembles in the nucleus, host cell RNA polymerase transcribes viral genes, progeny virions released by cell lysis, can cause lytic and persistent infections in humans

where and when are adenoviruses found?

worldwide, seasonal, winter is most common time of year for infections

how common are adenovirus infections?

causes 5-10% of cases of respiratory disease in the general population, half of children before age 5 will have 4 different adenovirus infections

spread is greatest among people living in close contact

how are adenoviruses transmitted?

aerosolized droplets, fecal-oral, fomites, perinatal and intrauterine (rare), direct inoculation of conjunctiva (swimming pools, ophthalmic instruments, medications)

where is the primary replication of adenoviruses?

mucosal epithelium of respiratory tract, GI tract, and conjunctiva (depending on serotype)

where are adenoviruses shed from?

upper respiratory tract, fecal shedding may occur for months even in asymptomatic patients

what is the immune response to adenovirus infection?

IgG antibody provides life-long, TYPE-SPECIFIC immunity, cell mediated immunity important in controlling persistent infections

what are the clinical manifestations of adenovirus?

depends on serotype and host age/immunocompetence

most infections are asymptomatic but infected people can still transmit

certain serotypes are associated with clinical disease like respiratory tract infections, pharyngeo-conjunctivitis, hemorrhagic cystitis, and gastroenteritis

most diseases are self-limiting, but pneumonia can be severe and even fatal

what are the lab diagnostic tools for adenoviruses?

viral culture and CPE for presumptive identification, viral antigen assay, PCR, serotyping and genotyping may be done but is not routine

what is the treatment for adenovirus infection?

supportive, antiviral therapy and pooled IV immune globulin reserved for patients who are immunocompromised and/or have severe disease

how can you prevent adenovirus infection?

good hygiene, live oral vaccine for ad types 4 and 7 used in US military personnel age 17-55 years

parvoviruses

some of the smallest viruses and have a high predilection for dividing cells (bone marrow, gut epithelium, developing embryo), B19 is the most important human parvovirus

what is the structure of parvovirus?

very hardy (survives pH 3-9), heat stable (>56C for 1 hr), non-enveloped, icosahedral nucleocapsid, ssDNA genome (5k), negative sense

how do parvoviruses replicate?

transcription, replication, and assembly takes place in the nuclei of dividing cells, especially erythroid- derived cells, requires a cell function present in S phase and host cell DNA polymerase, release of progeny virus occurs by cell lysis

who is most at risk of contracting parvoviruses?

people in close contact with children (teachers, daycare workers, ect), infections most common in late winter/early spring

how can parvoviruses be transmitted?

respiratory route is most common, B19 transmitted efficiently by blood transfusion/clotting factors or needles contaminated with infected blood, vertically (transplacentally) to fetus

what is the primary replication site of parvovirus, and what are the secondary targets?

primary site: respiratory or GI epithelium

secondary site: bone marrow, lymphocytes

B19 productively infects only human erythroid progenitor cells

what does the pathogenesis of parvovirus result from?

cell destruction and in some cases due to immune complexes

after initial infection, are you immune to reinfection of parvovirus?

yes for the specific serotype, B19 only has one serotype

what are the clinical manifestations of B19 parvovirus?

erythema infectiosum (5th disease)

acute, self-limiting contagious, most commonly presents as fever and rash that begins as marked erythema of the face (slapped cheek look), rash spreads to trunk and limbs 1-4 days later and lasts for about a week

what are the clinical manifestations for a non-immune pregnant woman infected with B19 parvovirus?

low incidence of fetal death during the 1st trimester, or hydrops fetalis (abnormal accumulation of fluid in fetal soft tissues and serous cavities, risk is highest if infection occurs during 1st half of pregnancy and is associated with higher risk of fetal loss)

what are the lab diagnostics for parvovirus?

serology (IgM), nucleic acid amplification test (NAAT)

how can you treat parvovirus infections?

supportive treatment

is there a vaccine for parvovirus?

no

fast facts about papillomavirus (HPV)

over 200 genotypes, some are tumorigenic, infections are associated with the development of warts, papilloma, and carcinoma depending on the genotype, vaccines are available that protect against selected genotypes associated with common infections and diseases including cancers

what is the structure of HPV?

small, non-enveloped, icosahedral nucleocapsid, dsDNA, 7.9 kbp

how is HPV classified?

based on DNA sequence homology because there is no in vitro infectivity assay and there are over 200 genotypes

can you shed HPV when you are asymptomatic?

yes

t/f HPV has a resistant capsid

true

how can you get infected with HPV?

abrasions in the skin: direct contact, sexual intercourse, childbirth, chewing (children)

how many people are infected with the STD HPV in the US and how many new cases are there per year?

20 million, 5.5 million per year

what are the clinical manifestations of HPV?

skin warts (verrucae), oral squamous papillomas and warts

what are the lab diagnostics for HPV?

papanicolaou smear (koilocytotic, squamous epithelial cells, a rim of condensed chromatin giving a halo effect)

DNA probes with or without PCR used to determine strain (HPV 16 and 18 are associated with cervical cancer

how is HPV infection treated?

most warts regress, freeze/burn with liquid nitrogen, surgery for larger laryngeal papillomas, inferferon injection

how can you prevent HPV?

condoms (but doesn’t prevent all transmission)

fast facts about HPV vaccines

given to adolescent and young adults, composed of capsid proteins

merck vaccine for HPV

effective against HPV type 6, 11, 16, 18

FDA approved in 2006

gardasil 9

glaxosmithkline vaccine for HPV

effective against HPV types 16 and 18

vaccine was generally safe, well tolerated, and highly immunogenic

cervarix

FDA approved in 2009

________ is an abnormal accumulation of fluid in fetal soft tissues and serous cavities.

A. Koilocytotic, squamous epithelial cell

B. Verrucae

C. Erythema infectiosum

D. Hydrops fetalis

E. Syphilis

D. Hydrops fetalis