Exam 4 Flashcards
Serotypes
numerous strains of the same pathogen existing as a means to evade the immune system
S. pneumoniae
has 90 different serotypes that differ in capsular polysaccharide but only one antibody can recognize one serotype capsule
epidemics
local population spread
influenza virus
displays genetic variation since antibodies rise against is tend to bind to hemagglutinin and neuroamindiase (glycoprotein of viral coat)
antigenic drift
RNA replication is error prone and can introduce mutations; this evolution through mutation allowing for survival is this.
pandemic
world wide spread i.e. viruses that emerge and are quite different from predecessors that can infect almost everyone
antigenic shift
strains that cause pandemics are recombinate viruses that derive from some RNA genome from a human influenza virus and some from an influenza virus that infects a different species
Trypanosomes
protozans like trypanosma brucei (sleeping sickness), S. typhimurium, N. honorrhoease.
gene conversion
what happens when a variable surface glycoprotein is produced one at a time but rearrangment makes the expression site into requred for synthesis
VSG gene
variable surface glycoproteines….for T. brucei there are more that 100 genes encoding this weird trypanosome surface glycoprotein
hemagglutinin and neuraminidase
glycoproteins of influenza’s viral envelope and where antibodies tend to bind
Trypanosome life cycle
involves both insect and human host where the insects transmit it to humans through bite.
Trypanosome surface
made of glycoprotein and has 1000 genes encoding for varibale surface glycoproteins (VSGs), but only produce one at a time. Need rearrangement into the expression site for synthesis, VSG genes are moved into this expression site by gene conversion. Different human antibodies have to be made every time the VSG switches.
Normal virus elimination
established viral infections are terminated by CD8 cytotoxic T cells after MHC class I presentation. Great for handling rapidly replicating viruses since there are more proteins around.
Viral latency
dorment non-replicating state of virus where they do not produce enough proteins form MHC class I presentation
M. tuberculosis and L. monocytogenesis
bacteria that live intracellularly after phagocytosis
Toxoplasma gondii
creates a specialized intracellular environment
Treponema pallidum (syphilis) and schistosome
coat themselves with human proteins
Ways viruses subvert immune system
capuring cytokine genes, inhibition of complement, and inhibition of MHC class 1 presentation and synthesis
Human Cytomegalovirus (HCMV)
Makes proteins aimed at MHC class 1 molecules. Some of the proteins lower MHC class 1 at the surface (should increase NK action) and other proteins block NK inhibitory receptor action responsible for sensing MHC class I
Staphylococcal enterotoxins and toxic shock syndrome toxin-1
These are superantigens
Superanitgens
Bind MHC class II and T-cell receptors together in absence of a specific antigen. This causes T cells to divide and differentiate randomly (polyclonal response) so the adaptive immune response is not specific or functioning. Causes a lot of IL-1, IL-2, TNF-a and thus systemic shock
Normal monomeric Iga
normally functions as an opsonin for delivery to phagocyte
Staphylococcal superantigen-like protein 7
(SSLP7) protein made by S. aureus which has binding sites for IgA and C5. Prevents IgA and C5 from working and stops bacteria from being phagocytosed
Pathology
the disease symptoms
Respiratory syncytial virus
(RVS) all of the symptoms are caused by T(h)2 cells responding to the infection and causing wheezing bronchiolitis. Vaccine just makes it worse by activating T(h)2 cells that produce cytokines on subsequent infection thus exacerbating the disease
Schistosoma mansoni
parasite who lays eggs which can get stuck in the liver. T(h)2 cells cause inflammation, hepatic fibrosis, and liver failure
Which of the following explains why Streptococcus pneumoniae can infect an individual recurrently?
Immune responses against S. pneumoniae are serotype-specific and protect only against strains that possess the same capsular polysaccharide antigens
The mode of evolution responsible for the production of recombinant influenza viruses composed of a genome derived from two different influenza variants is called .
antigentic shift
Which of the following contribute to new epidemics and the long-term survival of the influenza virus in the human population? (Select all that apply)
a. New viral strains possess epitopes not recognized by antibodies made in the previous epidemic
b. The first influenza strain provoking a primary immune response constrains the types of antibodies made during a subsequent encounter with a different strain
c. The RNA genome of the influenza virus is subject to point mutations during viral replication
d. The virus loses the capacity to express hemagglutinin, thereby rendering neutralizing antibodies useless
e. The virus uses gene rearrangement to achieve antigenic variation, which creates new epitopes
a, b, c
Trypanosomes escape from adaptive immunity by altering the type of expressed on the parasite surface.
variable surface glycoprotein
Which of the following are used by the herpes simplex virus to subvert host immune responses? (Select all that apply)
a. a virus-encoded Fc receptor
b. a virus-encoded complement receptor
c. inhibition of MHC class I expression
d. inhibition of peptide transport by transporter associated with antigen processing (TAP)
e. inhibition of ICAM-1 expression
a, b, c, d
Herpes simplex virus favors neurons for latency because of the low level of ____, which reduces the likelihood of killing by CD8 T cell.
a) LFA-3
b) Tool-like receptors
c) MHC Class I
d) MHC Class II
c) MHC Class I
The process whereby random mutations lead to viral evasion from previously developed immune responses, leading to epidemics is:
a) antigentic shift
b) antigentic drift
c) serotype switching
d) gene conversion
b) antigenic drift
“good” of inherited immunodeficiencies
There are over 150 with some more sever then others. However, their study and treatment has revealed a lot about the immune system
Inherited Immunodeficiency classification
dominant, recessive, or x-linked
Normal INF-gamma
major cytokine that activates macrohpages, induces phagocytosis, important in intravesicular infections (mycobacterial) is made by NK cells, T(h)1 CD4 T cells, and cytotoxic CD8 T cells.
Normal INF-gamma receptor
functions as a dimer to bind to Jak with activates STATs
INF-gamma receptor mutations
can be recessive or dominant and cause INF-gamma Receptor Deficiency
Recessive INF-g Receptor Mutation
no INF-gamma receptor at the surface leading to complete absence of INFgR1
Dominant INF-g Receptor Mutation
leads to no Jak binding and partial INFgR1 chain
Antibody deficiency
causes increase in infections by pyogenic bacteria (S. pyogenes, S. aureus)
pyrogenic bacteria
encapsulated like S pyogenes and S aureus, that cannot be recognized by professional phagocytes without antibody opsonization
X-Linked Agammaglobuinemia
(XLA was first immunodef found) Defective Btk kinase which is needed for growth and development of pre-B cells preventing mature B cells from forming. Females will have normal development in B cells with inactivated mutated X chromosome)
X-Linked Hyper IgM Syndrome
lack of functional CD40 needed for isotype switching
Complement Deficiency
Also tends to cause pyogenic infections, but can also cause buildup of immune complexes since early components of complement are important in elimination of immune complexes
Complement Activation Protein Deficiencies
can lead to increased infections and autoimmune-like states
C1, C2, C4 Deficiency
immune-complex disease
C3 Deficiency
Susceptibility to pyogenic bacteria
C5-C9 Deficiency
Susceptibility to Neisseria
Factor D, P Deficeincy
Susceptibility to encapsulated bacteria and Neisseria but no immune-complex disease
Factor I Deficiency
similar to C3 with increased pyogentic infections
DAF, CD59 Deficiency
Autoimmune-like conditions including paroxysmal nocurnal hemoglobinuria
C1INH Deficiency
Hereditary angioedemia (HAE)
Hereditary Angioneurotic Edema
HANE is an autosomal dominant disease caused by deficiency in complement regulator C1 inhibitor (C1INH). Causes swelling of face, laryn, abdomen, inactivates C1 protease, inhibits blood clotting proteases.
serpin
serine/cysteine protease inhibitor family…C1INH is one
Bradykinin
if high levels and fluid leaking out of the blood (edema)…due to C1INH not being around since it inhibits blood clotting proteases
Phagocyte Deficiency
Any defect in phagocytosis has a profound effect on infection clearance
Leukocyte adhesion deficiency
lack of integrin necessary for phagocyte homing….results in persistent extracellular bacterial infection
Chrongic granulomatous disease
CDG - defective NADPH oxidase….results in persistent bacterial infection and granuloma formation
Chediak-Higashi Syndrome
defect in vesicle fusion (phagocytosed material not delivered to lysosome)
Severe Combined Immune Dificiency
SCID can be caused by many different aspects of bad T cell development. Infants need to be in pathogen free environment and need bone marrow transplant and passive administration of antibodies
SCID causes
X-Linked (mutation in common gamma chain cytokine receptor, and Wiskott-Aldrich Syndrome), deficiency in Purine degradation, and Bare lymphocyte syndrome
Wiskott-Aldrich Syndrome
mutation in protein involved in cytoskeletal rearrangement needed for sytokine release and signaline
Deficiency in Purine Degradation
(adenosine deaminase and purine nucleoside phosphorylase) thought to lead to an increase in dATP whic hindibits nucleotide biosynthesis and thus DNA synthesis needed for proliferation
Bare lymphocyte syndrome
lack of MHC molecules from lack of AID or AIRE I think
IL-12 receptor deficiency
Also increases intracellular bacterial infections (linked to INF-g defeciecies)
Normal IL-12 Receptor
On NK and MO which are activated by IL-12 and leads to secreation of INF-g and macrophage activation. Oh T cells, IL-12 will induce differentiation into T(h)1 cells which then secrete INF-g for MO activation. On cytotoxic T cells, IL-12 activated leading to secretion of INF-g
X-Linked Lymphoproliferative Syndrome
immunodeficiency in SH2D1A (unknown function) leading to increased persistence of Epstien Barr Virus (EBV), which can lead to lymphoma
Immunodeficiency Treatments
Bone marrow transplant, somatic gene therapy since most immunodeficiencies affect hematopoietic cells
Bone Marrow Transplant Process
Patient’s bone marrow destroyed by radiation and chemotherapy, followed by transplations of a graft from a healthy donor to reconsitute the entire hematopoiteic system
somatic gene therapy
replacing the defective gene is being explored as an option
Transplant Considerations
HLA Matching
Purpose of HLA matching
reduces graft-versus-host disease, and ensures reconstitution of immune system. The recipient’s HLA molecules is what drives positive selection in T cell development, but the donor HLA molecules will be doing the presentation of peptides to T cells by antigen-presenting cells
Graft-versus-host disease
response to allogeneic MHC molecules
During bone marrow transplant… Positive selection of T cells
driven by recipient HLA molecules
During bone marrow transplant….presentation of peptides to T cells by antigen-present cells
due to the donor HLA molecules
Which of the following is not an example or mutation found in SCID?
a) Mutation in adenosine deaminase
b) Hereditary Angioneurotic Endema (mutation of C1INH)
c) Wiskott-Aldrich syndrome (mutation in WASP - cytoskeletal protein)
d) Mutation in common gamma chain cytokine receptor
b) Hereditary Angioneurotic Endema (mutation of C1INH)
Symptoms of AIDS first recongnized
Early 1980s characterized by a large reduction in CD4 T cells and subsequent infection by pathogens that normally don’t infect healthy individuals, or by very aggressive lymphomas
Human Immunodeficiency Virus
isolated in 1983 (actually two types HIV-1 and HIV02 but HIV-1 is the principal cause
Early evidence of HIV
Late 1950s, its believed that the virus was caused by antigenic shift from primate virus
HIV infection number
WHO estimated 33 million people are infected
Characteristics of HIV
RNA virus with ribonucleoprotein core, Retrovirus, nucleocapsid proteins (protease, reverse transcriptase, integrase) uses host cells transcription and translatio machinery to make virions
Retrovirus
uses an RNA genome to direct synthesis of a DNA intermediate
Protease
HIV nucleocapsid protein, cleaves glycoprotein to produce gp41 and gp120 at surface
Reverse Transcriptase
converts viral RNA genome into a complementary DNA (cDNA)
provirus
cDNA is integrated into the genome
General Life cycle of HIV
1) virion binds to CD4 and co-receptor on T cell
2) Viral envelope fuses with cell membrane, and viral genome enters cell
3) reverse trascriptase copies viral RNA genome into double-stranded cDNA
4) Viral cDNA enters nucleus and integrates into host DNA
5) T-cell activation induces some transcription of provirus
6) RNA trascriptions are spliced to allow synthesis of early proteins Tat and Rev
7) Tat amplifies transcription of viral RNA. Rev increases transport of RNA to cytoplasm
8) Gag, Pol, and Env are made and assembled with viral RNA into virions which bud from the cell
Cells HIV infects
CD4 T cells, dendritic cells, and macrophages since they all express CD4
gp120
is on outside of HIV and binds tightly to CD4 and a co-receptor (CXCR4(lymphocyte) or CCR5(MO))
gp41
mediates fusion of the viral envelope with the host cell plasma membrane
Virion production
requires T cell activation since T-cell activation causes activation of transcription factor NF-kB which binds the promoter of the provirus, thus directing RNA transcription of viral RNAs
Tat
viral protein that binds long terminal repeat of viral mRNA known as the trascriptional activation region (TAP) to increases viral RNA transcription
Rev
viral protain that controls supply of viral RNA to the cytoplasm and RNA splicing
Rev early action
RNA to encode viral proteins
Rev late action
viral genomes
gp160
made from provirus and is the precursor to gp41 and gp120 after protease cleaves it.
HIV Infection Immediately
either asymptomatic or flu-like, but dramatic decline of CD4 T cells, possible immune response with antibodies and cytotoxic T cells activation
Seroconversion
2-6 weeks after initial HIV infection, when first exhibition of anti-HIV antibodies inblood serum. Slight rebound of CD4 T cells and patient is asymptomatic. Lasts 2-15 years (average 10) and the CD4 T cell population steadily declines until half of normal levels making effeciive immune response unlikely (sympotmatic phase)
Symptomatic phase
Effective immune response does not exist, lasts until 20% of CD4 T cells remain…after full blown AIDs
HIV-infected progession prognosis
Most HIV-infected individuals will progess to AIDs without medical treatment (seen by studying infection of hemophiliacs with contaminated blood.
Seronegative
Very small group of HIV infected people who do not progress to AIDs even with extensive exposure to virus like sex workers. Some even have cytotoxiv lymphocytes and T(h)1 cells directed against infected cells.
CCR5 Deficiency
Causes resistance to HIV infection. Causes mild immunodeficenty. Might have come from selection for this mutation during plague and smallpox
CCR5 normal
plays a role as a chemokine receptor (also the MO co receptor that tightly binds to gp41 of HIV)
CCR5-delta32
the mutation that causes the CCR5 deficiency. Only found in caucasians, and 10% of the population is heterozygous, 1% homozygous)
HLA homozygosity and AIDs
speeds up the progession to AIDs but there are some allotypes that slow the progression (present HIV peptides and activate NK cells)
HIV Therapy Targets
Reverse transcriptase inhibitors, Protease inhibitors, Fusion/Entry inhibitors, Integrase inhibitors, multi-drug combinations, maturation inhibitors…31 FDA-approved drugs on market (ish)
Reverse Transcriptase Inhibitors
nucleoside and non-nucleoside…prevent action of reverse transcriptase
Protease Inhibitors
prevents production of infectious viral particles
Fusion/Entry Inhibitors
prevents viral fusion with host cell membrane
Integrase Inhibitors
blacks integrase, required for viral cDNA incorporation
Multidrug Combination Products
combines more than one drug class into a single product to prevent resistance…HAART
maturatio inhibitors
in development, prevent virion assembly and then prevent HIV outer coat assembly or viral budding)
HAART
highly active antiretrovial therapy…combo of antiretorviral drugs
HIV mutation rate
very high since RNA has lack of proofreadind of reverse transcriptase. complicates vaccine development and effectiveness of antiviral drugs.
Antiviral Failure
when drugs target a specific HIV viral process, the drug will lose effectivness as the virus mutates to be resistant to the drug. Resistance to protease drugs can start within days but then months for reverse transcriptase.
General action of antiviral drugs
1) productive infection of CD4 T cells accounts for more than 99% of virus in plasma
2) Infected cells are short-lived (3-4days) so HIV must continually infect new cells
3) if virus production is blocked by a drug, the virus is rapidly cleared from the blood (neutralizing antibodies, complement, phagocytes)
4) CD4 T cell numbers will rapidly increase to replace those lost by infection
Clinical latency
When during therapy the CD4 T cell numbers increase.. During this, a vast number of viruses and CD4 cells are produced and dying
Onset of AIDs
Even with clinical latency, CD4 T cells will continue to decline until adaptive immune response is not effective and individuals are susceptible to other infections (resembles SCID)
Common AIDs onset infections
usually from opportunistic infections with infectious agents already present in our body but normally under conrol.
First opportunistic infections
Tend to be in oral and respiratory tract (Candida, M, tuberculosis)
Late onset of AIDs infections
herpesvirus reactivation can lead to shingles, B cell lymphoma (EBV), and Kaposi’s sarcoma (endothelial tumor)
AIDs Pneumonia
very common caused by Pneumocystis carinii
Broadly Neutralizing Antibodies
Tend to recognize one or four epitopes on gp120 (all epitopes are in functinally relevant locations) and can be polyractive between two different antigens (gp120 and CD4)
Elite Neutralizers
1 in 500 make antibodies that neutralize a broad range of HIV-1. Targeting this natural production or using passive immunization could be HIV treatments.
Hypersensitivity (allergic) reactions
overreactions of the immune system to harmless environmental agents
Allergens
environmental agents that drive hpersensitivity reactions
Who has allergies?
10-40% of the population in developed countries
Common allergens
Inhaled (pollen, dust mite feces), Injected (insect venom, drugs), Ingested Material (peanuts, shellfish), Contacted Material (plant oil, metal)
Type 1
binding of antigen to IgE, principally on mast cells (typically inhaled antigens) – sometimes referred to as immediate hypersensitivity
Type 2
covalent binding of small molecules producing foreign-looking particles – B cell response leads to IgG production (e.g. penicillin allergy)
Type 3
immune complexes deposit on tissue walls and cause damage (e.g. nonhuman antibodies and proteins used in therapy)
Type 4
lipid-soluble antigens covalently bind to intracellular proteins, yielding abnormal peptides during MHC presentation – thus effector T cells are involved (also called delayed-type hypersensitivity)