Viral Pathophysiology – Composite Lecture Notes

Vocabulary flashcards covering key viruses, pathogenesis, clinical features, diagnostics and treatments across respiratory, hepatotropic, dermotropic, neurotropic, multisystemic and lymphotropic viral infections discussed in the lecture series.

Human Respiratory Syncytial Virus (HRSV)

Enveloped, non-segmented, negative-sense ssRNA virus that forms syncytia and causes severe lower-respiratory infections such as bronchiolitis and pneumonia.

Syncytium

Multinucleated giant cell produced by fusion of infected cells; hallmark of HRSV infection.

HRSV Group A & B

Two major antigenic groups of HRSV; multiple genotypes but only one serotype.

Bronchiolitis

Inflammation and obstruction of bronchioles, commonly caused by HRSV or HMPV in infants.

IL-33 & TSLP

Cytokines induced by HRSV that promote Th2 bias, mucus production and possibly allergic asthma.

Human Metapneumovirus (HMPV)

Enveloped, non-segmented, negative-sense ssRNA virus closely related to HRSV, producing similar respiratory disease but with shorter illness.

Human Rhinovirus (HRV)

Non-enveloped, positive-sense ssRNA Picornavirus responsible for ~50 % of common colds; three species (A,B,C) with many serotypes.

ICAM-1 Up-regulation

HRV-induced increase in adhesion molecule expression that facilitates secondary bacterial attachment (e.g., S. aureus).

Otitis media

Middle-ear infection; 30-40 % of cases linked to HRV, often with bacterial co-infection.

Haemophilus influenzae Co-infection

Bacterium exploits HRV-induced epithelial damage to invade upper airway tissue.

Streptococcus pneumoniae Co-infection

Facilitated by HRV-triggered NF-κB activation and adhesion molecule expression.

HAV (Hepatitis A Virus)

Non-enveloped, positive-sense ssRNA Picornavirus spread mainly by fecal-oral route; causes acute, self-limited hepatitis.

HAV Serology – IgM

Marker of acute HAV infection.

HAV Serology – IgG

Indicates past HAV infection or vaccination and lifelong immunity.

HEV (Hepatitis E Virus)

Non-enveloped, positive-sense ssRNA virus transmitted fecal-orally; severe in pregnant women and immunosuppressed patients.

HBV (Hepatitis B Virus)

Enveloped, circular partially-double-stranded DNA virus; infection marked by Hepatitis B surface antigen (HBsAg).

HBsAg

HBV envelope glycoprotein; presence indicates active infection, target of protective antibodies.

HBV Chronic Infection

Persistence of HBsAg > 6 months with potential progression to cirrhosis and hepatocellular carcinoma.

HDV (Hepatitis D Virus)

Defective, enveloped negative-sense ssRNA virus requiring HBV HBsAg for infectivity; causes coinfection or superinfection.

HDV Superinfection

Acquisition of HDV by chronic HBV carriers; high risk of fulminant hepatitis and chronicity.

HCV (Hepatitis C Virus)

Enveloped, positive-sense ssRNA Flavivirus with high propensity for chronic infection; no vaccine available.

Direct-acting Antivirals (DAA)

Modern drugs targeting HCV enzymes, achieving high cure rates in 8–24 weeks.

HHV-1 (HSV-1)

Enveloped dsDNA alphaherpesvirus typically causing orolabial herpes; establishes lifelong latency in trigeminal ganglia.

HHV-2 (HSV-2)

Enveloped dsDNA alphaherpesvirus usually causing genital herpes; latency in lumbosacral ganglia.

Latency

Persistent viral genome in neurons with minimal gene expression; can reactivate under stress, UV, fever, etc.

Herpes Keratoconjunctivitis

HSV infection of cornea and conjunctiva that can threaten vision.

Aciclovir

Guanosine analogue antiviral activated by HSV thymidine kinase; inhibits viral DNA polymerase.

HHV-3 (Varicella-Zoster Virus, VZV)

Enveloped dsDNA alphaherpesvirus causing varicella (chickenpox) and herpes zoster (shingles) upon reactivation.

Dermatome

Skin region innervated by a single sensory nerve; zoster rash typically restricted to one dermatome and unilateral.

Post-herpetic Neuralgia

Chronic pain persisting after shingles rash heals.

Measles Virus

Enveloped, negative-sense ssRNA Morbillivirus that is pan-tropic; single serotype; transmitted via respiratory droplets.

CD150 (SLAM)

Primary measles virus receptor on immune cells.

Koplik Spots

Small bluish-white lesions on buccal mucosa pathognomonic for measles.

Measles Immunosuppression

Transient but profound weakening of host defenses, predisposing to secondary infections.

Subacute Sclerosing Panencephalitis (SSPE)

Rare, fatal progressive CNS disease years after measles infection.

Mumps Virus

Enveloped, negative-sense ssRNA Paramyxovirus causing epidemic parotitis; single serotype.

Parotitis

Swelling of parotid salivary glands, hallmark of mumps.

Orchitis

Testicular inflammation occurring in up to 50 % of post-pubertal males with mumps.

Rubulavirus Hemagglutinin-Neuraminidase

Envelope glycoprotein of mumps virus involved in attachment and immune response.

Rabies Virus

Enveloped, bullet-shaped Lyssavirus causing fatal encephalitis; single serotype with multiple variants.

Negri Bodies

Eosinophilic cytoplasmic inclusions in neurons pathognomonic for rabies.

Hydrophobia

Painful pharyngeal spasms triggered by liquids; classic rabies symptom.

Post-Exposure Prophylaxis (PEP)

Wound cleaning, rabies vaccine, and rabies immunoglobulin administered after potential exposure.

Poliovirus

Non-enveloped, positive-sense ssRNA Enterovirus with three serotypes; can cause paralytic poliomyelitis.

Viremia

Presence of virus in the bloodstream; primary and secondary waves seen in polio pathogenesis.

OPV (Oral Polio Vaccine)

Live attenuated poliovirus vaccine inducing mucosal IgA but carries risk of reversion.

IPV (Inactivated Polio Vaccine)

Injectable, killed poliovirus vaccine that is safe for immunocompromised but lacks mucosal immunity.

Post-Polio Syndrome

Late-onset muscular weakness decades after acute infection, due to degeneration of compensatory motor units.

Human Immunodeficiency Virus (HIV)

Enveloped retrovirus with two RNA copies, reverse transcriptase and integrase; targets CD4+ T cells.

Reverse Transcriptase

Viral enzyme that converts HIV RNA into proviral DNA.

Integrase

HIV enzyme catalyzing integration of proviral DNA into host genome.

Protease

HIV enzyme that cleaves polyproteins to form mature infectious virions; target of ARV drugs.

Acute Retroviral Syndrome

Flu-like illness 2–4 weeks post-HIV exposure with high viremia and transmissibility.

Latent HIV Reservoir

Resting memory CD4+ T cells harboring integrated but transcriptionally silent provirus, barrier to cure.

AIDS (Acquired Immunodeficiency Syndrome)

Clinical stage defined by CD4 count < 200 cells/mm³ or AIDS-defining illnesses.

Elite Controllers

HIV-infected individuals who spontaneously suppress viral load < 50 copies/mL without therapy.

ART (Antiretroviral Therapy)

Combination drug regimen suppressing HIV replication and restoring immune function.

Tenofovir (TDF)

Nucleotide reverse-transcriptase inhibitor used in first-line ART and PrEP.

Lamivudina (3TC)

Nucleoside reverse-transcriptase inhibitor paired with TDF in standard ART.

Dolutegravir (DTG)

Potent integrase inhibitor recommended as core of first-line ART regimens.

Pre-Exposure Prophylaxis (PrEP)

Daily antiretroviral intake by high-risk HIV-negative individuals to prevent infection.

Post-Exposure Prophylaxis (PEP) – HIV

28-day antiretroviral course started within 72 h after potential HIV exposure.

Th2 Response

Type of adaptive immunity characterized by IL-4, IL-5, IL-13; promoted by IL-33/TSLP in HRSV infection.

Croup

Laryngotracheobronchitis presenting with barking cough, may be caused by HRV or parainfluenza viruses.

Cyanosis

Bluish discoloration of skin due to hypoxemia; seen in severe HRSV bronchiolitis.

qRT-PCR

Quantitative reverse-transcription PCR; sensitive molecular test for RNA virus detection.

ELISA

Enzyme-linked immunosorbent assay used for detecting viral antigens or specific antibodies.

Ribavirin

Broad-spectrum antiviral nucleoside analogue used for severe HRSV or HEV in immunosuppressed, but highly toxic.

Immunoglobulin Hyperimmune (VZIG)

High-titer anti-VZV antibody preparation administered to high-risk contacts for passive protection.

Varicella Vaccine

Live attenuated VZV vaccine preventing chickenpox and lowering shingles risk.

Latency-Associated Transcript (LAT)

HSV RNA expressed during latency, thought to help maintain quiescent state and inhibit apoptosis.

Stress-Induced Reactivation

Resumption of productive HSV infection triggered by UV light, fever, trauma, or hormonal changes.

Hemagglutinin (Measles & Mumps)

Viral envelope glycoprotein mediating attachment to host receptors; major antigenic target.

PVRL4 / Nectin-4

Epithelial receptor enabling measles virus exit into airways and facilitation of contagion.

Sarcoma Kaposi

Endothelial tumor associated with advanced AIDS and HHV-8 infection.

Candidiasis Esophageal

Fungal infection of esophagus; AIDS-defining when CD4 < 200 cells/mm³.

Toxoplasma Encephalitis

Opportunistic CNS infection in AIDS patients with CD4 < 100 cells/mm³.

Meningoencephalitis (HMPV/HRSV complications)

Inflammation of brain and meninges occasionally resulting from severe respiratory viral infection.

Gastrointestinal Junction Breakdown

HRV-induced loss of tight junctions leading to increased mucus and bacterial invasion.

Hepatocellular Carcinoma

Primary liver cancer linked to chronic HBV and HCV infection.

Circular dsDNA (HBV genome)

Partially double-stranded relaxed circular DNA unique to HBV.

Supercoiled cccDNA

Covalently closed circular DNA minichromosome of HBV persisting in hepatocyte nuclei as template for viral replication.

Bile Excretion of HAV

Mechanism by which HAV reaches intestine for fecal shedding.

Carcinoma Bulbospinal Polio

Severe poliomyelitis affecting both brainstem and spinal cord causing high mortality.

Eczema Herpeticum

Widespread HSV infection in patients with skin disorders such as atopic dermatitis.

Vaccine-Derived Poliovirus (VDPV)

OPV strain that has genetically reverted to neurovirulence and can circulate in under-immunized populations.

Interferon-α (VZV therapy)

Cytokine occasionally used with antivirals to treat severe VZV infections.

SLAM/CD150 Tropism

Measles virus preference for immune cells via CD150 receptor, contributing to immunosuppression.

Paramyxovirus Fusion Protein

Surface glycoprotein that mediates viral-cell membrane fusion; target for neutralizing antibodies.

Hydrogen Peroxide Inactivation

Envelope lipid susceptibility explaining herpesvirus sensitivity to detergents and organic solvents.

Lyssavirus Variants

Different wildlife-adapted strains of rabies virus; seven circulate in Brazil.

Fibrosis of Lymph Nodes (HIV)

Replacement of lymphoid tissue by collagen following chronic HIV replication, impairing immunity.

Antigen Drift (Polio)

Gradual mutation within OPV strains that may restore neurovirulence.

Glycoprotein G (Rabies)

Rabies surface protein inducing neutralizing antibodies and target of vaccines.

Genotype vs Serotype

Genetic classification versus antigenic grouping; HRV has many serotypes but three genetic species.

Mastitis (Mumps)

Inflammation of breast tissue occurring in ~15 % post-pubertal women with mumps.

IgA Secretory

Antibody class providing mucosal immunity; induced by live oral vaccines such as OPV.

Nucleoside Reverse Transcriptase Inhibitor (NRTI)

Class of antiretroviral drugs mimicking natural nucleosides to terminate viral DNA synthesis.

Integrase Strand Transfer Inhibitor (INSTI)

Drug class blocking insertion of HIV DNA into host genome, e.g., dolutegravir.

Protease Inhibitor (PI)

Antiretroviral class preventing maturation of HIV particles by blocking viral protease.