Viral Infections and Immune Response Quiz

Clinical Virology - Study Notes

• This chapter covers various viruses and their clinical implications.

DNA Viruses - Papillomaviruses

• At least 100 types of papillomaviruses have been identified.
• They are naked double-stranded DNA viruses.
• They can infect cutaneous or mucosal surfaces.
• Some HPV types are associated with cervical cancer.
• The HPV genome is circular and approximately 8,000 base pairs long.
• HPV DNA encodes seven or eight early genes (E1 to E8) and two late/structural genes (L1 and L2).

Viral Pathogenesis of Papillomaviruses

• Inoculation of the virus into the epithelium (skin or mucosal surfaces)
• Local multiplication of the virus.
• Resolution (latency) or
• Wart formation or
• Cell transformation.

Clinical Syndromes of Papillomaviruses

• Warts: Benign, self-limiting skin proliferations that regress over time. Common warts occur on hands and feet.
• Head and Neck Benign Tumors: Single oral papillomas are the most common benign epithelial tumors of the oral cavity. Laryngeal papillomas, often associated with HPV-6 and HPV-11, are the most prevalent benign epithelial tumors of the larynx.

Clinical Syndromes of Papillomavirus II

• Anogenital Warts: Also known as condylomata acuminata, these warts occur predominantly on the external genitalia and perianal areas.
• Cervical Dysplasia or Neoplasia: High-risk HPV types (HPV-16 and HPV-18) infection of the female genital tract is linked to cervical neoplasia and cancer. Initial microscopic changes are called dysplasia and sometimes regress spontaneously.

Treatment, prevention, and control of Papillomaviruses

• Removal of warts (surgical cryotherapy, electrocautery, or chemical agents like podophyllin)
• Topical or intralesional cidofovir therapy to kill HPV-infected cells
• Vaccination with Gardasil (HPV-6, -11, -16, and -18) or Cervarix (HPV-16 and -18) is recommended, primarily for females, starting at age 11, to prevent cervical cancer and anogenital warts. Vaccination is also being introduced for males.

DNA Viruses - Polyomaviruses

• Polyomaviruses include BK, JC, and SV40.
• Acquired via the respiratory route and are typically asymptomatic.
• Establishes latent and persistent infections.
• These viruses can reactivate in immunocompromised hosts, causing severe conditions like progressive multifocal leukoencephalopathy (PML).

Viral Pathogenesis of Polyomaviruses

• Inoculation into the respiratory tract.
• Multiplication in the respiratory tract.
• Primary viremia.
• Multiplication in the kidneys.
• Latent in the kidneys.
• Virus in Immunocompetent hosts can lead to: Viruria and possible hemorrhagic cystitis.
• Reactivation due to immunocompromise can lead to: BK virus multiplication in the urinary tract resulting in reactivation.
• JC virus viremia which results in a wide spread throughout the CNS including possible PML.

Clinical Syndromes of Polyomaviruses

• Primary infection is usually asymptomatic. Reactivation is more common in people with weakened immune systems (e.g., those with AIDS).
• PML (progressive multifocal leukoencephalopathy) is an increasingly prevalent and often fatal complication associated with JC virus reactivation.

Treatment, Prevention, and Control of Polyomaviruses

• Treatment is limited and usually involves antiviral medications (e.g., cidofovir).
• Preventing primary (initial) infections is not possible.
• Preventing reactivation is important to improve health outcomes in immunocompromised patients.

DNA Viruses - Adenoviruses

• First isolated using human adenoid cell culture.
• Naked double-stranded DNA viruses.
• Spread by aerosols, close contact, and fecal-oral routes.
• Causes lytic (mucoepithelial cells), latent (lymphoid and adenoid cells), and transforming (animal cells only) infections

Viral Pathogenesis of Adenoviruses

• Invasion of upper respiratory tract, gastrointestinal tract, and skin, followed by viremia potentially to multiple organs and potentially lymph nodes.
• Resolution and latency or a variety of other clinical symptoms.

Clinical Syndromes of Adenoviruses

• Respiratory illnesses (undifferentiated upper respiratory tract infection, pharyngoconjunctival fever, acute respiratory illness, pertussis-like syndrome, pneumonia).
• Acute hemorrhagic cystitis
• Epidemic keratoconjunctivitis.
• Gastroenteritis
• Hepatitis
• Meningoencephalitis in all infants and children and immunocompromised patients

Treatment, prevention, and control of Adenoviruses

• No specific treatment exists.
• Handwashing and disinfection of surfaces are important preventive measures.

Enveloped DNA Viruses - Herpesviruses

• Enveloped double-stranded DNA viruses.
• Three subfamilies: Alphaherpesviruses (HHV-1, HHV-2, HHV-3) Betaherpesviruses (HHV-5, HHV-6, HHV-7) Gammaherpesviruses (HHV-4, HHV-8)
• Establish latent or persistent infections.
• Reactivation is commonly associated with periods of immunosuppression

Viral Pathogenesis of Herpesviruses

• Transmission-related to a variety of clinical pathways that vary between viruses.
• Cellular infection occurs as a result of viral entry, infection, and replication.
• Latency or persistent or other clinical symptoms
• The site of latency and the symptoms will vary depending on the virus.

Clinical Syndromes of Herpesviruses

• Herpes simplex virus (HSV-1 and HSV-2): cold sores, oral herpes, genital herpes, keratitis, encephalitis, and neonatal herpes.
• Varicella-zoster virus (VZV): chickenpox, shingles
• Epstein-Barr virus (EBV): infectious mononucleosis, Burkitt's lymphoma, nasopharyngeal carcinoma
• Cytomegalovirus (CMV): congenital infection, pneumonia, retinitis, in immunocompromised patients.
• HHV-6 and HHV-7: roseola
• HHV-8: Kaposi's sarcoma.

Treatment, prevention, and control of Herpesviruses

• Antiviral medications are used for treatment for all of the viruses
• Vaccination exists for certain types

RNA Viruses - Picornaviruses

• Small RNA viruses.
• Naked (no envelope) icosahedral capsids.
• Include enteroviruses (poliovirus, coxsackieviruses A and B, echoviruses, rhinoviruses, cardioviruses, aphthoviruses) and hepatitis A virus (HAV).

Viral Pathogenesis of Picornaviruses

• Transmission of the virus happens via a wide variety of direct and indirect pathways - e.g., respiratory droplets from direct contact with infected surfaces.
• Cellular infection occurs with subsequent local replication to dissemination and viremia.

Clinical Syndromes of Picornaviruses

• Poliovirus: asymptomatic, abortive, non-paralytic, and paralytic polio.
• Coxsackieviruses A and B: herpangina, hand-foot-and-mouth disease, myocarditis, pericarditis.
• Echoviruses: various mild infections.
• Rhinoviruses: common cold.
• Hepatitis A virus (HAV): acute hepatitis.

Treatment, prevention, and control of Picornaviruses

• Treatment is not always available.
• Prevention is focused on hygiene and sanitation to prevent the transmission of the virus.

RNA Viruses - Coronavirus

• Single-stranded positive-sense RNA viruses.
• Coronaviruses are named for the corona-like appearance of the virion.
• A variety of clinical syndromes are associated with coronavirus infections

Viral Pathogenesis of Coronaviruses

• Transmission occurs via respiratory droplets, but also in sweat, urine, and feces (varies with the specific coronavirus).
• Replication in the oropharynx.
• Viremia that may potentially lead to a wide variety of symptoms.

Clinical Syndromes of Coronaviruses

• Common cold (2nd cause after Rhinovirus), SARS, MERS, COVID-19.

Treatment, prevention, and control of Coronaviruses

• Treatment and prevention measures vary considerably depending upon the specific coronavirus and its associated clinical symptoms.

RNA Viruses - Other groups

• Other RNA viruses like Norovirus, Orthomyxoviruses, Paramyxoviruses, Rhabdoviruses, Filoviruses, Reoviruses, and Togaviruses/Flaviviruses have various pathologies, clinical manifestations, prevention, and treatment.
• Research is ongoing to better understand, prevent and develop treatments for many.

Test your knowledge on various viral infections, including Rhinovirus, Herpes Simplex Virus, and others. This quiz explores symptoms, transmission, and immune responses related to these viruses. Perfect for students studying virology or infectious diseases.