Herpesvirus Biology Quiz

Herpesviruses

• Herpesviruses are a group of DNA enveloped viruses.
• Herpes simplex virus types 1 and 2, varicella-zoster virus, cytomegalovirus, Epstein-Barr virus, and human herpesvirus 8 are examples of herpesviruses.
• Herpes simplex virus type 1 (HSV-1) typically causes lesions above the waist, while HSV-2 typically causes lesions below the waist.
• HSV-1 and HSV-2 are indistinguishable morphologically and structurally.
• Genomes can be differentiated using restriction digestion analysis and glycoprotein G antisera analysis.
• HSV-1 binds to heparin sulfate on the host cell surface.
• Replication needs DNA polymerase and thymidine kinase.
• In latently infected cells, circular HSV DNA is not integrated into the cellular DNA.
• Transcription of HSV DNA produces latency-associated transcripts (LATS).
• LATs are non-coding regulatory RNAs that suppress viral replication.
• Reactivation of viral replication can occur when genes encoding LATs are excised.
• Treatment for encephalitis and systemic diseases from HSV-1 is acyclovir.
• Primary and recurrent HSV-2 can be treated with acyclovir, which shortens lesion duration and reduces shedding.
• Foscarnet is used when acyclovir is resistant.
• No vaccine exists for HSV.

Poxviruses

• Poxviruses are large, complex viruses classified as a linear, double-stranded DNA.
• Vaccinia virus, molluscum contagiosum virus, and smallpox virus are examples of poxviruses.
• Smallpox is the only poxvirus that has been eradicated.
• The virus typically replicates in the cytoplasm and cannot access the host RNA polymerase in the nucleus.
• Smallpox virus has a single, stable serotype.
• Humans are the only host for smallpox.
• Vaccination can protect people exposed to smallpox.

Human Papillomavirus (HPV)

• HPV is a common, sexually transmitted infection. It leads to benign tumors of squamous cells causing warts.
• HPV is non-enveloped and has double-stranded circular DNA.
• Over 100 HPV types exist.
• HPV types 1 to 4 usually cause skin warts. Types 6 and 11 can cause genital warts.
• HPV types 16 and 18 are frequently associated with intraepithelial neoplasia, which can progress to carcinomas.
• Skin warts can be treated with liquid nitrogen.
• Genital warts can be treated with topical imiquimod, podophyllin, or other treatments.
• Gardasil 9 vaccine protects against several HPV types that cause warts and cancer.

Respiratory Viruses

• Respiratory viruses cause predominantly upper and lower respiratory tract symptoms.

Influenza Viruses

• Influenza is a segmented, single-stranded RNA virus.
• Hemagglutinin and neuraminidase are protein spikes on the influenza envelope.
• Influenza A and B both cause worldwide epidemics and major outbreaks, respectively.
• The H and N proteins vary antigenically resulting in wide diversity within each strain, causing annual epidemics and pandemics, potentially resulting in reassortment of gene segments
• Oseltamivir and zanamivir are examples of treatments that inhibit neuraminidase.
• There are inactivated and attenuated vaccines for Influenza.

Parainfluenza Virus

• Parainfluenza is an RNA virus causing croup, laryngitis, bronchiolitis, and pneumonia, especially in children.
• It has an RNA genome, similar nucleocapsid to other paramyxoviruses.
• Surface spikes are formed from H, N, and F proteins.

Respiratory Syncytial Virus (RSV)

• RSV is an RNA virus that is the primary cause of pneumonia and bronchiolitis, especially in infants.
• RSV can cause otitis media and pneumonia in the elderly.
• The virus has an RNA genome, a similar nucleocapsid to paramyxoviruses, and only a fusion F protein.
• Treatment with ribavirin is used for severely ill infants and is not guaranteed to be effective.
• Monoclonal antibodies (e.g., palivizumab and nirsevimab) to target the F protein can be used for passive immunity.

Coronavirus

• Coronaviruses are enveloped RNA viruses, causing common colds, SARS, MERS, and COVID-19.
• They have nonsegmented RNA genomes, a helical nucleocapsid, and do not have virion polymerase.
• Coronavirus replication occurs in the cytoplasm.
• Treatment options include ribavirin and steroids, but with uncertain efficacy.

Rhinovirus

• Rhinovirus is a non-enveloped virus causing the common cold.
• The RNA genome is single-stranded and nonsegmented.
• It has multiple serotypes.
• The virus is inactivated by stomach acid upon ingestion. Replication is optimal at 30°C, and poor at 37°C
• No antiviral therapy currently approved.

Adenovirus

• Adenovirus is a non-enveloped virus causing pharyngitis, conjunctivitis, common colds and pneumonia.
• It has a double-stranded linear DNA genome.
• The icosahedral capsid includes a fiber that facilitates attachment.
• No antiviral therapy currently available.