---start immuno 2.21.97---- finishing up w/immunization and vaccines. the book is mostly re: human medicine. part talks about immune system inhibiting viral and bacterial infxns, that part read well. immunization: active: natural, unintended - acquired by infxn artificial, deliberate - acquired by vaccination passive: natural - transplacental, colostrum artificial - administration of immune globulins passive lasts shorter time than active. intracellular pathogens (bacteria) are degradedin acidified vesicles. peptides bind to MHCII and are presented to CD4+ T cells. TB, leprosy, brucellosis.... cause CD4 Th1 cells to make gamma interferon which activates macrophages. CMI/DTH type reaction... extracellular bacteria are eliminated by effect of Ab, complement fixation and lysis or opsonization, where C3b attaches to bacteria w/IgM or IgG... note that bacteria do their damage by liberating toxins that kill cells and cause an inflammatory rxn and increase bm output of wbcs, etc. cytosolic pathogens -not inside vesicles, but truly in the cytoplasm - these are VIRUSES. they are degraded in the cytoplasm. peptides bind to MHC I, and are presented to CD8+ T cells - Tc cells. the cytotoxic t cells cause death of the infected cell. realize that viruses themselves tend to kill cells after they take over the cell. most frequently viruses themselves just kill cells. eg, a neutrophil will pick up a TB organism but it can't do anything. but when neutrophil dies, it liberates the TB organism to infect another cell. but macrophages can kill TB. when you think of bacteria it should be clear that a bacterium has a whole bunch of epitopes present at the same time. bacteria don't present just one epitope. there are flagellae, pili, capsule, membrane, cell wall, cytosol, all these things can present different epitopes. so generally you see a polyclonal Ab response to bacteria - to many epitopes. but only a few of the Ab will be protective Ab, and be the main ones responsible for helping to eliminate the bacteria. only a few will be effective. sometimes it's against one particular part of the bacterium. so how is a bacterium eliminated? An extracellular organism. like staph, strep, e coli, which lives between cells. well, some part of innate defense can work against it - eg lysozyme can kill some bacteria. most of the time we're talking about Ab development and complement activation and opsonization - C3b is put on surface of bacterium, targeting it for phagocytosis. also gram negs with LPS can trigger complement alternative pathway by itself, ad you still get opsonization and phagocytosis by the mphage. also toxin neutralization: many bacteria make toxins, and immune system makes antitoxin. if youconsider at white time one would have to give an antitoxin that you suspect being infected w/toxin making bug...you wanna give it ASAP because as soon as toxin is made and absorbed into cells, antitoxin isn't useful anymore. so you may want to give passive Ab protection right away, because by the time patient does may be too late. usually passive immunization is needed to treat these patients with antitoxin... anti bacterial immunity: neutralization of bact toxin: by antitoxic Abs in concert w/innate immune system: opsonization, IgM, IgG, Ab/C/bacteria--lysis CMI - intracellular organisms (TB) when to give antitoxin? right away immunize pregnant dam: transfer of antibacterial Abs via placenta IgG or colostrum. but must be careful - some vaccines cause abortions or other problems. only give at time when fetus is already well developed. antiviral immunity: very complex, depends on: route of viral entry, site of initial attachment and subsequent spread: measles --> respiratory tract = site of entry, then becomes systemic, goes to many other tissues, but main immunity is needed in respiratory tract. immunization is given IM, and some of the IgG you make will get to respiratory mucosa, even though little IgA made, hopefully you make enough to protect you. If you immunize animal via resp tract via aerosol or nasal entry, you get IgA response, which is what you want here for this virus, but since measles also goes to other tissues, you can do it this way and cover the resp tract as well. With Polio, it comes in through GI tract, and that's where you want immunity. old polio vacc was orally administered, because primarily lymphoid tissue in pharynx and tonsils was crucial to setting up IgA response. the virus then goes to other location after GI, but it's important to realize where the site of entry will be and where you need the most protection. tonsilectomized patients who got oral poliovaccine had poor immune response, because tonsils are responsible for getting IgA response to rest of digestive tract. how does immunity get to rest of GI tract? lymphocytes triggered in mucosal tissue will migrate through lymphoid system to other mucosal tissue. also innate immune system: induction of interferons- when you have a viral infxn primarily alpha and beta IFN (non immune IFN) is made by many cells and is liberated and picked up by neighboring cells, and that preps cell to make "antiviral substances" which prevent viral replication. so this limits the spread of infxn and works way before an antibody response would kick in. starts showing up in 3 days, peaks at 7 -takes 10-14 days for Ab response CMI ativation of T DTH cytotoxic T cells- limits viral infxn, kills virally infected cells. viral Ag is on cell, with MHC I, Tc cell makes direct contact and lyses cell w/perforins. Ab response - humoral Ab have to be present to neutralize virus, to lyse virus, to prevent viral infxn of cells. but in order to limit viral infxn and get rid of viral infected cells you need Tc cell rxn. NK cell activity - NK cells can kill virus infected cells - no specific recognition, they just see "nonself" probably due to decreased amt of MHC expression. ok. now we're virologists - it's useful to think of them in terms of what they do and what kind of Ag you're dealing with. think of RNA virus that enters cell, takesover machinery, and builds a new virus particle that buds off cell surface. HIV, FeLV do this. so you get a virus coming out that will have viral Ag on surface, that are PART of the virus itself. now, in process of taking over cell machinery, cell can break down part of virus and present it on surface as a viral antigen. how would that be presented on a typical viral infected cell eg in bronchi or whatever? MHC I would present it. then Tc cell will recognize it. now, if one were tomake Ab against viral structures, would it be one Ab or polyclonal? do all work together or areonly a few protective? You will make a polyclonal response just like you do to bacteria. many of the Abs are made to the externally present Ag on the virus, but only a couple will be protective. and you can make Ab against internal viral structures, which are not protective at all because an antibody can't get IN to the virus (or into a cell) to bind. also antibodies can't bind intracellular pathogens. if virus is on cell surface, antibody can bind. Ab may bind to sites on the virus so that they block the virus from binding to a receptor that would let it get into a cell.eg, blocks adhesion molecules. viruses can also trigger alternative pathway. or Ab may be against an enzyme that the virus needs to replicate. there is one Ig class that can work, to a limited extent, in inhibiting viral replication, inside the cell. what isotype? IgA -which is made by plasma cells along GI tract, and gets picked up by epi cells as a dimer, and is transported through epi cells, and IgA isliberated on the other side. but while it's IN the cell...it can actually partially at least inhibit the replication of a virus inside of a cell. antibodies against a viral Ag on cell surface (not virus itself) will bind, complement fixation, cell lysis, etc. cytotoxic t cells kill virally infected cells by direct contact/perforin release. also activated macrophages can play a role in phagocytosing the cell. mphages don't always kill the virus though. mphages can spread a viral infxn eg measles effects of antiviral antibodies: neutralization Complement mediated lysis of infected host cells, etc etc etc etc. what goes on in viral infxn? first - alpha and beta interferons kick in, prevent spread of virus, stop replication. also, surface Ig is next most important protective element. frequently there isn't enough IgA and virus gets disseminated, and youget real viremia - you get reallysick, fever,etc - then you start having an Ab response - IgM first, and then as immune response proceeds you get affinity maturation, etc, and you get protection against the organism,and then you get complement, cytotoxic T cell, IFNg, IgG involvement as well. then you get better :) recent approaches to vaccines: recombinant DNA technology: express foreign pathogenic viral antigen genes in another (innocuous) virus. don't use in animals a lot. mostly we use simpler vaccines. subunit vaccine: automated peptide synthesis. made with just the antigenic epitope or epitopes of the pathogen. anti idiotypes as a vaccine are not in use in veterinary medicine and that's all he has to say about it. anti idiotype configuration is identical to the epitope configuration. so it CAN be a vaccine. but we don't use it. slide; foot and mouth disease - doesn't exist in USA. was seen in mexico, and US vets killed all of those cows. lots of vets got killed by mexican farmers who were pissed about them killing their cows. vaccine: VP1 from foot and mouth disease virus -> dna coding for that was put into e coli plasmid, so now you have e coli making VP1. then you can vaccinate animals with VP1 -that way you aren't using the actual virus, so no risk of spreading dz, but animal will make immune response to the VP1 and then if exposed to virus, has Ab.... types of vaccines... you start with a live virus. those are dangerous. you need to make it no longer pathogenic, so it won't make animals sick, but so it retains immunogenicity so you can protect the animals. -can inactivate the virus- "killed virus" vaccine. we use this. -can attenuate the virus- "modified live virus" vaccine. is still alive,may cause mild infxn, but not overt dz. this is what we mostly use in animals -purified subunits -recombinant products (as in e coli example above) -synthetic product - if you use dna sequencing to get around using recombinant technique. subunit vacc: eliminate unwanted antigenic material, yields high efficiency, is not infxs, so can give large doses, may not be as potent as live organism. administration: systemic immunity: IM, SQ local immunity: intranasal, aerosol, feed or drinking water. if main intent is to get respiratory response, can use aerosol or intranasal methods... immunopotentiation/adjuvants: an adjuvant enhances the immune response to an immunogen but does not confer immunogenicity to haptens. these are allowed only for experimental purposes and cause big reactions.: freund's complete adj: (CFA) ---- water in oil emulsion and killed myc.TB BCG: attenuated mycobacterium corynebacterium parvum LPS -most clinically used vaccines use something like alum precepitate - alum - aluminum hydroxide. causes less reaction. other possible (expt'l) adjuvants: liposomes: phospholipid vesicles: used to increase Ab and CMI response to bacterial, viral, protozoal Ag incluiding small peptides. are nontoxic, biodegradable, structurally versatile. ex: (entrap IL2, MDP, alum, along with Ag). ISCOMs: immunostimulatory complexes. contain Ag, lipids,and mix of glycosides of steroids and triterpines. point is to elicit both CMI and Ab response. TYpesof immunization, active/passive transfer Passive: transfer abs from resistant to susceptible animal -temporary protection -susceptible to reinfxn after varying time after Ab wears off - type III hypersensitivity can occur (serum sickness) risk increases each time -anaphylaxis (type I) risk after repeated administration of antiserum -passively transferred ab interferes w/active immunization 0ab made in foreign species is broken down faster Active: - ideal -prolonged immunization -immunity to vaccinated animal and to offspring -no adverse effects -cheap, stable -adaptible to mass vaccination inactivation/attenuation of organisms used in vaccines: heat chemicals: formaldehyde, acetone, alcohol, ethylene oxide grow organisms in unfavorable medium grow in cell cultures of different species (CDV in ferrets) grow in TC passages for long time (CDV in k9 kidney cells) use related organism adopted in other species --cowpox --CAV2 crossprotects against CAV1 --measles virus protects against CDV --bovine viral diarrhea protects against hog cholera. dog vaccination: multiple antigens in same vaccine: CDV, CAV1, CAV2, CPI, CPB, leptospria canicola - modified live- no problem giving multiple vax at same time, thought that it would exhaust immune system is preposterous. rabies: killed vaccine only. bacterin: dead bacteria vaccine toxoid: chemically altered toxin live vaccines: advantages: highly antigenic, prolonged immunity, few inoculations needed, no adjuvant needed, less chance for hypersensitivity to develop (because give less frequently), virus may stimulate interferon production. disadvantages: residual virulence, reversion to full virulence (a few particles only can be bad), spread to unvaccinated animals, risk of contamination of vaccine with unwanted organisms, instability/storage problems. so you can't use modified live rabies vaccine. you never want to vaccinate immunosuppressed patients with any modified live vaccines, because they make you very sick. acquired immunity--->passive (artificial or maternal) or active(natural infx or artificial) artificial active aquired immunity: metabolic products (toxoids), dead organisms( bacterins), living organisms: fully virulent (contagious erythema), heterologous (measles), attenuated (distemper) heterologous means it's a foreign virus but its epitopes are linked and cross reactive so in this case youuse measles virus to vaccinate against distemper. ----break----- vaccine failures: never get ABSOLUTE protection never equal in all animals: immunogenetics vaccine responses will fall along a bell shaped curve. most will make reasonably good response, some do REALLY well, some do really badly. those that do really well probably more likely to get hypersensitivity rxn. some animals just don't respond well to vaccines at all; may have "holes" in MHC repertoire. expect poor immune response when: malnourished parasitized extreme heat/cold [stress] maternal Abs are present- this is why puppies get a series. animal incubating dz at time of vaccination use of abx when giving live bacterial vaccine excessive alcohol use on skin inactivates live virus vaccine. colostral Ig levels in domestic animals: horse: IgA 500-1500; IgM 100-350; IgG 1500-5000 (mg/dl) bovine 100-700 300-1300 3400-8000 sheep 100-700 400-1200 4000-6000 pig similar to above dog 500-2200 14-57 120-300 placental transfer based on placental layers...4-6 layers, almost no placental transfer. dog and cat - endotheliochorial: do transfer a bit of placental Ig but mostly colostral. rodents almost all placental, no colostral vaccine failure chart: unsatisfactory vaccine - wrong strain of organism employed or inadequate vaccine satisfactory vaccine - satisfactory administration can fail if animal already incubating dz or animal simply fails to mount immune response due to biological variation, prior passive immunization, or animal is immunosuppressed. unsatisfactory administration will fail due to inadequate dosing or death of supposedly live vaccine. Eg, if your patient gets distemper signs 3 days after you give the vaccine, it's because he was already incubating it, most likely. hypersensitivity rxns: (vaccine rxns) RISK INCREASES with increased # of vaccinations (of same vaccine) anaphylactic: type I -to immunizing antigen - to antigen associated w/production of vaccine -more associated w/multiple injections, so seen more with use of dead vaccines. -most common reaction -usually to a contaminant, not the actual vaccine immune complex dz type III -local arthus rxn- this is rare. we don't vaccinate often enoughfor animal to have high level of Ab at time of next vaccine. -generalized vascular disturbance -corneal clouding CAV1 induction of autoimmune dz: -allergic encephalitis -idiopathic polyneuritis (inflammation of nerve sheaths) here, this patient is presenting a cross reactive Ag to immune system which cross reacts w/self Ag. first rabies vaccines: animals were infected w/rabies, their spinal cords were ground up and used for vaccination. patients were protected against rabies but developed reaction to CNS due to cross reactivity. multiple choice for dr weber (60%), dr scott short answer/short paragraph (40%) th1, th2, cytokines, macrophage processing of ag.... *sigh* ----end----