Viruses 2 - Retroviruses, HSV, etc. - KMS Flashcards
What is the genetic makeup of a retrovirus? What enzymes must be packaged in the capsule?
•Enveloped +ssRNA with reverse transcriptase (RNA-dependent DNA polymerase) and integration into host cell DNA
What viruses are pertinent from the Oncornavirus family?
•Oncornaviruses: HTLV 1, HTLV 2 (Human T-cell Lymphotropic Virus)
(a type of retrovirus)
Generally speaking, Oncornaviruses are what?
•Oncogenic transforming viruses
What does an HTLV-1 infection cause?
•HTLV-I produces HTLV myelopathy/tropical spastic paraparesis and T-cell leukemia/lymphomas
What does an HTLV-2 infection cause?
•HTLV-II associated with several cases of myelopathy/tropical spastic paraparesis and T cell lymphoproliferative disease (hairy-cell leukemia-like)
Why are Lentiviruses are clinically important?
Lentiviruses include HIV-1 and HIV-2
How is HIV spread?
•Spread by fluids (sex, transfusions, contaminated needles) or during pregnancy
How is an HIV virus able to gain access to a cell? What cells do they need to gain access to initially? What is essential for this process?
•Attach to CD4 receptor & CCR5 (mφ) or CXCR4 (TH cell) coreceptors
Absolutely need co-receptor for this process to occur
What cells does HIV-1 have a predilection for?
•Tropism for CD4+ (T-helper) cells
What are the initial symptoms of an HIV-1 infection?
•Lymphadenopathy, fever, weight loss and malaise
What is a common-ish neurological manifestation of AIDS? Why?
•AIDS dementia: mimics Alzheimer disease, may involve HIV infection of the brain and microglia
AIDS is frequently associated with what change in body habitus due to what syndrome?
•Wasting syndrome (“slim disease“) common in Africa.
Where is HIV-2 commonly found?
•HIV-2 similar to HIV-1 infection but restricted to W. Africa
How is AIDS diagnosed? What is tested for to help this Dx?
- Dx- Occurrence of AIDS defining disease (opportunistic infection, malignancy, etc.)
- Serology for HIV antibodies using the ELISA (Enzyme-Linked Immuno-Sorbent Assay) and Western Blot (tests for antibodies against viral proteins), PCR
How is HIV and AIDS treated?
•Rx – Antiretrovirals:
nucleoside/nucleotide analogues
nonnucleoside reverse transcriptase inhibitors
protease inhibitors
fusion inhibitors
chemokine coreceptor antagonists
integrase inhibitors
Why are the gag genes important for HIV infection? What genes are included, and what do they make?
Gag (group specific antigens) polyprotein
gag
p24 - capsid, early marker of infection
p7p9 - core nucleocapsid
p17 - matrix
Why are the pol genes important for HIV infection?
Pol (polymerase) polyprotein
pol:
Reverse transcriptase - produces provirus
Integrase - DNA integration into host DNA
Protease - cleaves viral polyprotein
Why are env genes important for HIV infection?
Envelope proteins
env:
gp120 - Binds CD4 & CCR5(mφ)or CXCR4(TH-cell)
gp41 - Host cell fusion protein
Why are LTR genes important for HIV infection?
- LTR*: Long terminal repeat sequences
- LTR* - Integration and viral gene expression
What is the genetic makeup of Herpesviruses? enveloped?
•Large, dsDNA and enveloped
What histological findings are common with Herpesvirus infection?
•Produce intranuclear inclusions and multinucleated giant cells
What unusual feature about Herpesviruses allow them to create recurrent infections? What types stay where in the body?
- Capable of latency and can lead to recurrent infections
- HSV-1, HSV-2 and VZV are “neurotropic”
- CMV and EBV are “lymphotropic“
What is the natural reservoir of HSV, CMV, VZV, and EBV?
humans
Name the 8 types of HHVs and the diseases they cause.
- *1.HHV 1 [α] - Herpes Simplex 1 (HSV-1)
2. HHV 2 [α] - Herpes Simplex 2 (HSV-2)
3. HHV 3 [α] - Varicella-Zoster virus (VZV)
4. HHV 4 [ȣ] - Epstein-Barr virus (EBV) (Oncogenic transforming virus)
5. HHV 5 [β] - Cytomegalovirus (CMV) (Oncogenic transforming virus)**
6. HHV 6 [β]– Causes roseola infantum/exanthema subitum (sixth disease)
7. HHV 7 [β]– Causes roseola infantum/exanthema subitum (sixth disease) - *8.HHV 8 [ȣ]– Kaposi Sarcoma-associated Herpesvirus (Oncogenic transforming virus)**
Where does herpes simplex initially replicate? How does reinfection manifest?
•Replicate initially in skin or mucosae followed by latent neural infection with subsequent recurrences of skin and mucosal lesions
What histological findings should you associate with herpes simplex infections?
•Have intranuclear acidophilic Cowdry type A inclusions
How is HSV-1 typically transmitted, and what can it cause?
- Usually transmitted by saliva
- “Cold sores” (herpes labialis)
- Gingivostomatitis – oropharyngeal blister in kids
- Herpetic keratitis - if accompanied by conjunctivitis can lead to corneal scarring and blindness
What is a potentially disastrous outcome of HSV-1?
•Fatal sporadic encephalitis, #1 cause in U.S.
What is the typical presentation of an HSV-2 infection?
•Genital herpes – blistering skin/mucosal lesions
What are 2 lesser known presentations of HSV-2 infections?
- Whitlows – erythematous lesions on toes or nail cuticle
- Neonatal herpes - local or disseminated (50% mortality if untreated) Herpetic meningitis & encephalitis also occur
How is HSV-2 typically transmitted? What other infection can it increase chances contracting?
- Generally transmitted by sexual contact or during delivery
- Increases risk of subsequent HIV infection
How is a HSV infection Dx’ed?
•Dx – cytology, immunostaining, PCR
How is an HSV infection treated?
•Rx – acyclovir (other “ciclovir” anti-virals)
How is Varicella-Zoster Virus (VZV) typically transmitted?
•Respiratory transmission
What does the “Varicella” half of VZV cause? What does this disease look like?
Chickenpox:
•Mild infection in children (worse in adults)
•Usually transmitted by saliva
•After 2 weeks, skin rash first on the head and trunk, and later on the extremities (asynchronous and centripetal spread)
•Macules to papules to vesicles to pustules to crusts
•Intranuclear inclusions at base of vesicle
How does the chickenpox rash typically spread?
•Usually transmitted by saliva
- After 2 weeks, skin rash first on the head and trunk, and later on the extremities (asynchronous and centripetal spread)
- Macules to papules to vesicles to pustules to crusts
What does the “Zoster” half of VZV cause?
Shingles - zoster
- Older individuals with reactivation of latent infection
- Skin areas innervated by sensory nerves of the dorsal root ganglia
- Trigeminal nerve is common distribution
- Very painful radiculoneuritis
- Occasional debilitating transverse myelitis
What is the distribution of the rash and the symptoms associated with shingles?
- Skin areas innervated by sensory nerves of the dorsal root ganglia
- Trigeminal nerve is common distribution
- Very painful radiculoneuritis
- Occasional debilitating transverse myelitis
How is a shingles infection Dx’ed?
•Dx – clinical, cytology, PCR
(Rash will be very distinctive - often unilateral dermatome distribution)
How is shingles treated?
•Rx - acyclovir
How is shingles prevented?
- 2 doses of varicella (VAR); 12 through 15 months & 4-6 years
- Zoster vaccine (Zostavax®) for people aged 60 years and older
What is the genetic makeup of Epstein-Barr virus (EBV)?
•dsDNA & envelope
How is EBV typically spread?
•Human to human via saliva
How does EBV gain entrance to cells, and what cells and receptors does it seek out?
•Attach via CD21
•= Complement receptor 2 = EBV receptor
•Normally acts as receptor for C3d, C3dg, and iC3b
What common disease does EBV cause? What are the symptoms and findings?
•Infectious mononucleosis
•Fever, fatigue, malaise and pharyngitis
•Atypical activated T-lymphocytes (Downey cells)
•Can develop hepatitis, splenomegaly and other complications
EBV latently affects what cells? What can this cause?
•EBV latently infects B-cells, potential for recurrence
EBV also has what worrying characteristic? What other diseases is it associated with due to this characteristic?
- Oncogenic transforming virus
- Hodgkin lymphoma, Burkitt lymphoma, central nervous system lymphomas, & nasopharyngeal carcinoma
•Hairy oral leukoplakia in HIV patients
How is an EBV infection Dx’ed?
•Dx – heterophile antibodies (Monospot), antibodies to viral capsid antigens
How is an EBV infection usually treated?
•Rx - supportive
What histological findings are associated with Cytomegalovirus (CMV) infection?
•Owl-eye basophilic intranuclear inclusions
What cells does CMV infect?
•Infects monocytes and monocyte precursors
Name 8 ways CMV is transmitted. (Or at least 4 important ones.)
•Transplacental - primary infection pregnant mother
•Neonatal - cervical or vaginal secretions during birth
•Perinatal -breast milk from a mother who has active infection
•Saliva – common during preschool years
•Genital - dominant mode after about 15 years of age
•Respiratory secretions
•Fecal-oral
•Iatrogenic - organ transplants or blood transfusions
CMV infections are often asymptomatic. However, what 2 diseases are associated with infection?
•CMV mononucleosis-syndrome with fever, fatigue and atypical lymphocytes
•Congenital cytomegalovirus infection (cytomegalic inclusion disease of the newborn)-in utero infections with jaundice, purpura, hepatosplenomegaly and central nervous system development disorders
•Associated with mucoepidermoid carcinoma
How is a CMV infection Dx’ed?
•Dx- cytology, serology. culture or viral DNA by PCR or antigens
How is a CMV infection treated?
•Rx- supportive +/- ganciclovir
What is the genetic makeup of the Poxviridae family?
•dsDNA with envelope
Where do the viruses that make up the Poxviridae family typically replicate?
•Replicate in the cytoplasm of host cell
What 2 clinically important diseases are caused by the Poxviridae family?
Smallpox
Molluscum contagiosum
What is molluscum contagiosum? How is it spread? What does it look like?
Molluscum contagiosum
- Common self-limited viral disease caused by Poxvirus
- Spread by direct contact, particularly seen among young children and adults
- 0.2 -0.4 cm nodules on face, trunk and anogenital area
What is the genetic makeup of Papovariedae/Papillomaviridae/Human Papilloma Virus (HPV)?
•Naked with circular dsDNA (>100 HPV serotypes)
What cells does HPV typically infect?
•Trophic for epithelial cells of the skin and mucus membranes
How common is HPV? How can infection present?
- Possibly the most common sexually transmitted disease in the world
- Infections may be latent (asymptomatic), subclinical, or clinical
HPV is considered an oncogenic transforming virus(es). What lesions can they cause, and what cell cycle regulators do they mess up?
•Oncogenic transforming viruses
•Verrucae, papillomas, condyloma, and cervical, anal and pharyngeal cancers
•Viral E6 inhibits p53 protein and E7 inhibits pRB protein
What are the low risk HPV strains associated with?
•Low risk - types 6 and 11 cause condylomas and oropharyngeal papillomas
What are the high risk HPV strains associated with?
- High-risk - types 16 and 18 responsible for most cancers and high grade dysplasias
- Genome is incorporated into the host genome
How are papillomaviruses generally transmitted?
•Generally transmitted by direct contact
What is the Dx for an HPV infection?
- Dx – Clinical for verrucae and condylomas
- PCR for viral RNA of specific HPV types (e.g. types 16 & 18)
- Cytology and or biopsy for cytopathic effects
What is the Tx for an HPV infection?
•Rx – Depends on lesion type, anywhere from nothing to surgery to radiation and chemo
What is the prevention for HPV infection?
- Prevention – Vaccination (females 9-26 years) and physical barriers
- Gardasil© (types 6, 11, 16 and 18)-three shots (0, 2 and 6 months)
- Cervarix© (types 16 and 18)-three shots (0, 1 and 6 months)
What is the genetic makeup of the Papovariedae/Polyomaviridae?
•Naked dsDNA
What are the 2 clinically important viruses of the Polyomaviridae family?
BK and JC viruses
What is the reservoir and transmission of the BK and JC viruses? What kinds of patients do these cause disease in?
- Respiratory reservoir and transmission
- Cause infections only in immunocompromised patients
What disease does the BK virus cause? How is it Dx’ed?
- BK - Renal disease (failure) in AIDS or post-transplant patients
- Dx - BKV DNA by PCR or urine cytology with decoy cells (basophilic nuclear inclusions)
What disease does the JC virus cause? How is it Dx’ed?
- JC - Progressive multifocal leukoencephalopathy in AIDS or post-transplant
- Dx - JCV DNA by PCR
What is the genetic makeup of Adenoviridae?
•Naked dsDNA with numerous serotypes
What is the transmission of Adenoviridae?
•Respiratory and oral-fecal transmission
What diseases does the Adenoviridae family cause?
- Acute respiratory disease – serotypes 4,7 &21) upper respiratory infections in kids/young adults that can progress to pneumonia
- Gastroenteritis - adenoviruses that lead to diarrhea
- Pharyngoconjunctivitis – pink eye and sore throat
- Epidemic form also exists
- Acute hemorrhagic cystitis – in older boys
How is a Dx of Adenoviridae infection made? How is it treated?
- Dx – Serology or PCR
- Rx – supportive
How is infection by Adenoviridae prevented?
•Prevention – live adenovirus vaccine (types 4 and 7); two concurrent oral tablets only approved for military personnel 17 -50 years of age
What is the genetic makeup of Parvoviridae/Parvovirus 19?
•Naked ssDNA in segments (some positive, others negative)
What is some additional interesting information about parvovirus 19?
•Proteins not well characterized but NS1 protein is thought to possess site-specific DNA-binding, DNA-nicking, ATPase, transcriptional, and helicase activities
(In gray, prolly not a high-yield topic)
What is the reservoir for parvovirus 19? Incubation?
- Reservoir is human respiratory tract with respiratory & vertical transmission
- 7-10 day incubation
What 2 clinically relevant diseases can result from parvovirus 19 infection?
•Erythema infectiosum (fifth disease)
•Fever, arthralgias and cheek rash children
•Aplastic anemia (infects erythroblasts)
•Can cause hydrops fetalis via in utero infection
How is parvovirus 19 Dx’ed and treated?
- Dx- serology or PCR
- Rx- supportive