Immunity to Viruses Flashcards
Immunity to Viruses
Mechanisms:
Soluble extracellular factors
– neutralizing antibody and complement (opsonin)
Immunity to Viruses
Mechanisms:
Inhibition of intracellular replication
– interferons, host cell
Immunity to Viruses
Mechanisms:
Immune-mediated lysis of infected cells
– CTL (CD8) and NK cells
Innate immune system:
Pattern recognition
– C-type lectins, membrane TLRs, cytosol sensors (Nod-like receptor), NK cells (viral surface products)
Innate immune system:
Soluble
– complement, interferons, cytokines recognize and neutralize free virons
Innate immune system:
Soluble
Interferons
– induced by TLRs → act via Jak/Stat → ↑transcription of MHC-1 for better viral antigen presentation
Innate immune system:
Soluble
Complement
– C3b opsonin → phagocytes, blocks viral attachment, enveloped viruses, EBV uses C3b to facilitate binding
Innate immune system:
Soluble
NK cells
– activated by ↓ MHC-1 → granzymes, perforin → apoptosis of infected cells, produce IFN, recognize Ab coated cells
Innate immune system: Importance
– newborns, early infection, pattern recognition, no memory, unaffected by vaccine
Adaptive immune system:
Antibody
– mucosal secretory IgA, protective Ab to epitopes, IgG/M clearance, block attachment/uncoating, target infected cells
Adaptive immune system:
Seroconversion
Seroconversion – rise in serum antibody titer, 4-fold increase indicates acute/chronic infection
Adaptive immune system:
CTLs
CTLs – resolving infection, latent and persistent infection, facilitate apoptosis, impaired with T cells deficiency
Adaptive Immune System:
T helper
T helper – regulate Ab production (class switching), CTL differentiation, NK activation, IFN-γ production
Adaptive immune system:
Importance
Importance – extracellular and intracellular elimination, induced by vaccines, low function in infants/immunocompromised
Microbial immune evasion:
co-evolves with immune mechanisms
Microbial immune evasion:
Cell-to-cell spread
Cell-to-cell spread – avoids extracellular environment, latency and avoidance of detection
Microbial immune evasion:
Antigenic variation
Antigenic variation – Abs can recognize, shift and drift allows for reinfection of a new strain, seasonal vaccines
Microbial immune evasion:
MHC
MHC – downregulation of MCH inhibits antigen presentation and recognition of infected cells, HSV, CMV, EBV
Microbial immune evasion:
Cytokines
Cytokines - production of mimic cytokines, soluble receptors
Microbial immune evasion:
Apoptosis
Apoptosis – blocked by viruses, promotes immortalization and chances for mutation
Types of vaccines:
Subunit
- recombinant antigen protein → Ab production – Hep B
Types of vaccines:
Inactivated
Inactivated – dead whole virus → no mucosal immunity – Polio, HAV, rabies
Types of vaccines:
Attenuated live
Attenuated live – whole weakened virus → mucosal immunity, CD8 cells
Vaccine Schedule
Schedule – certain vaccines interfere with maternal IgG, blood products, other vaccines, etc.
Immune globulin:
Uses
vaccine does not exist, progression is rapid, viral load reduction is critical, or viremia is common
Immune globulin:
IVIG
IVIG - some neutralizing antibodies, pathogen-specific IG, post-exposure, ex: rabies, HBV
Risks for viral infections:
Marrow transplant
– cyclosporine, GVH → herpes infections are common, CMV
Risks for viral infections:
Antibody deficiency
Antibody deficiency – enteroviruses, respiratory viruses
Risks for viral infections:
T cell deficiency
T cell deficiency – herpes viruses
