Viral Structure & Replication
While most DNA viruses replicate in the host nucleus, this complex family of DNA viruses brings its own DNA-dependent RNA polymerase to replicate entirely within the cytoplasm.
What is the Poxvirus family (Poxviridae)?
In response to viral infection, host cells secrete Alpha and Beta forms of this cytokine, which induce neighboring cells to produce RNase L and Protein Kinase R (PKR) to halt viral protein synthesis.
What is interferon?
Acyclovir inhibits viral DNA polymerase by causing premature chain termination because its chemical structure uniquely lacks this specific functional group on the ribose ring.
What is the 3' hydroxyl (3'-OH) group?
High-risk HPV strains 16 and 18 promote cervical carcinoma primarily through the viral oncoprotein E6, which binds to and triggers the proteasomal degradation of this critical host tumor suppressor.
What is p53?
A 19-year-old unvaccinated male presents with fever, malaise, and bilateral swelling of the parotid glands. Three days later, he develops severe unilateral testicular pain and swelling.
What is Mumps (causing parotitis and orchitis)?
Viruses with this type of genome can be directly translated by host ribosomes into a single, massive polyprotein that is subsequently cleaved by viral proteases.
What is a positive-sense single-stranded RNA (+ssRNA) virus?
Respiratory Syncytial Virus (RSV) and Measles evade neutralizing antibodies by spreading directly from cell to cell using this viral surface protein to merge host cell membranes.
What is the Fusion (F) protein?
This antiviral drug, often used for acyclovir-resistant HSV or ganciclovir-resistant CMV, does not require kinase phosphorylation but carries a black box warning for significant nephrotoxicity and severe electrolyte abnormalities.
What is foscarnet?
Infection with HSV or VZV typically produces these distinct eosinophilic, intranuclear inclusion bodies surrounded by a clear halo, best visualized on a Tzanck smear or tissue biopsy.
What are Cowdry Type A inclusions?
A 17-year-old female is prescribed amoxicillin for a presumed bacterial pharyngitis. Three days later, she develops a diffuse, pruritic maculopapular rash. A heterophile antibody test is positive.
What is Epstein-Barr Virus (Infectious Mononucleosis)?
Because they lack this lipid bilayer structure, viruses like Norovirus and Hepatitis A are highly resistant to desiccation, heat, and standard detergents, allowing them to survive on surfaces for weeks.
What is a viral envelope?
During latency, Epstein-Barr Virus (EBV) avoids immune detection by maintaining its genome in memory B cells not as integrated DNA, but as this circular, extrachromosomal structure.
What is an episome?
Oseltamivir works by inhibiting this specific viral enzyme, thereby preventing the cleavage of terminal sialic acid residues and trapping newly assembled virions on the host cell membrane.
What is neuraminidase?
Histologic examination of lymphoid tissue in a patient with this highly contagious childhood viral infection may reveal Warthin-Finkeldey multinucleated giant cells with intracytoplasmic and intranuclear inclusions.
What is Measles (Rubeola)?
A 42-year-old male with untreated HIV presents with decreased visual acuity and "floaters" in his right eye. Fundoscopy reveals yellow-white retinal lesions with perivascular exudates and hemorrhage. His CD4 count is 35 cells/mm³.
What is Cytomegalovirus (CMV retinitis)?
This unique family of DNA viruses replicates via an RNA intermediate, utilizing a virion-associated reverse transcriptase to synthesize its partially double-stranded circular DNA genome.
What is the Hepadnavirus family (Hepadnaviridae / Hepatitis B)?
HIV actively evades the cytotoxic CD8+ T-cell response by using its Nef protein to downregulate the expression of this critical molecule on the surface of infected host cells.
What is MHC Class I?
Unlike most antiretrovirals that target viral enzymes, this entry inhibitor drug works by allosterically binding to a host cell chemokine receptor, blocking the interaction with HIV gp120.
What is maraviroc (binds CCR5)?
A liver biopsy from a patient with chronic Hepatitis B will classicly show hepatocytes with this specific morphologic appearance, caused by the massive accumulation of Hepatitis B surface antigen in the endoplasmic reticulum.
What are "ground-glass" hepatocytes?
A neonate born to an unimmunized mother presents with a continuous machine-like cardiac murmur, bilateral cataracts, and profound sensorineural hearing loss.
What is Congenital Rubella Syndrome?
The phenomenon of antigenic shift, responsible for major pandemics, is exclusively seen in viruses like Orthomyxoviruses and Rotaviruses because they possess this specific architectural feature.
What is a segmented genome?
As a master of immune evasion, Epstein-Barr Virus secretes a viral homolog of this specific host cytokine, which actively inhibits macrophages and Th1 cell responses.
What is Interleukin-10 (IL-10)?
Sofosbuvir revolutionized the treatment of Hepatitis C by acting as a nucleotide analog that directly inhibits this specific viral enzyme, stopping viral RNA synthesis.
What is the NS5B RNA-dependent RNA polymerase?
Epstein-Barr virus gains entry into B lymphocytes by binding its viral envelope glycoprotein (gp350) directly to this specific host cell surface receptor, which also serves as the receptor for the C3d complement component.
What is CD21?
A 24-year-old male presents with a 2-week history of fever, sore throat, generalized lymphadenopathy, and painful mucocutaneous ulcers on his buccal mucosa. A rapid heterophile antibody test is negative, and a 4th-generation antigen/antibody test shows high levels of p24 antigen.
What is Acute HIV Infection (Acute Retroviral Syndrome)?