serology

what is the lag time for a primary response?

7-10 days

what is the lag time for a memory (secondary response)?

1-2 days

what is the peak response to how much total antibody produced to antigen of interest in a primary response?

smaller compared to memory response

what is the peak response to how much total antibody produced to antigen of interest in a memory response?

larger compared to primary response

what is the highest antibody isotype in primary response?

IgM

what is the highest antibody isotype in secondary response?

IgG

what is the antibody affinity in a primary response?

lower average affinity

what is the antibody affinity in a secondary response?

higher average affinity

what would a high IgM response correlate?

recent exposure to the antigen of interest (primary response)

what would a high IgG response correlate to?

memory response

what would we expect to regarding antibody levels in a chronic infection?

both IgG and IgM antibodies for a longer time

assume we are looking at a response to a vaccine and that the antibody at a certain level is considered protective; will one see a memory response if boosting after antibody levels were low and maybe undetectable?

yes, the animal has memory B-cells and the boosting will target these cells

assume we are looking at a response to a vaccine and that the antibody at a certain level is considered protective; when should one boost to ensure continued protection?

before level of antibody goes below protective level titer

when do we start vaccinating dogs against rabies?

3 months of age

what is important to understand about the rabies vaccine in regards to protection for the dog?

considered protected 28 days AFTER the vaccine has been given

when do we boost rabies vaccine in dogs?

one year after the first vaccination

Serum from a dog with clinical signs compatible with Disease "A" has a high IgM and low IgG titer to virus "A" that causes Disease "A". These results are most compatible with?

a primary exposure to virus "A"

3 multiple choice options

serology (in practice)

the diagnostic identification of antibodies in serum

serum

fluid fraction (no cells) after blood clots

what is another word for serotype?

serovars

how can serotypes that are closely related microbes such as viruses and bacteria be differentiated?

neutralizing antibody assays

serotypes of viruses and bacteria are defined as...

those that exhibit no antibody cross-reaction with another virus or bacteria of the same genus or species in a neutralizing antibody assay

what does it mean if viruses and bacteria have different serovars?

different serovars have a distinct set of antigens expressed on their surface that generate specific antibody responses so we can distinguish by serum neutralizing antibody assay

what is variant based on?

genotype

what is serotype based on?

serology (neutralizing antibody)

incubation period

time between infection and onset of clinical signs

what is important to understand about infection?

infection does not always lead to disease in all infected individuals

if an animal did not present with disease, it would not have a...

infectious period

infectious period

time during which the infected individual can infect another individual

what is important to understand about infectious period?

an individual can be infectious before onset of clinical signs depending on the pathogen

what is the incubation period for parvovirus infection?

4-14 days

what are clinical signs of parvovirus dependent on?

length of incubation period; viral shedding of virus can occur before clinical signs

viremia

presence of viruses in the blood

what is important to know about the infectious agent for diagnostic testing?

1. incubation period

2. when pathogen is detectable in host

3. what sample will the pathogen be detected in

4. when and what class of antibody is detectable

what are questions we may consider when deciding what diagnostics to perform?

1. if we want to detect infection

2. if we want to confirm or rule out disease

3. how we want to treat

4. know how to prevent transmission to susceptible hosts

seroconversion

the detection of SPECIFIC ANTIBODIES in the blood SERUM due to infection or immunization

how long does seroconversion usually take?

2-3 weeks in the majority of infected or vaccinated individuals

what does seroconversion usually reflect?

first exposure to the microbe of interest either via vaccination or infection

what does seropositivity status depend on?

the sensitivity and specificity of the assay used

what does seroconversion NOT mean?

antibodies are present for an indefinite amount of time

after a primary response has occurred and there has been re-exposure to the antigen of interest, how long would seroconversion take?

1-2 days since there will be memory B-cells to produce a memory antibody response

what is important to understand about seroconversion and protection?

seroconversion does not always mean protection; only certain types and amounts of antibodies may confer protection and we may need CMI for protection

what would an example be of how seroconversion does not mean immediate protection?

dogs vaccinated against rabies will seroconvert in 10-14 days, but they are not considered protected until 28 days after the vaccination (need time to increase neutralizing antibody)

what would an example be of infection not equaling disease?

cattle infected with BLV are infected for life but most never develop disease due to BLV

BLV

bovine leukemia virus

what does a cattle positive for BLV antibody reflect?

infection with BLV not disease due to BLV

what are examples of infected animals that do not undergo seroconversion?

1. animals that are immunosupressed

2. animals that develop clinical rabies

why in vet med do we not use the detection of serum antibodies to help diagnose clinical rabies in animals?

animal will likely not have any detectable antibodies to the rabies virus in its serum

when would we use seroconversion in regards to rabies?

to determine if animal has responded to vaccination

when is infectiousness at its highest in many infectious diseases?

before seroconversion

in regards to seroconversion what happens in vector-borne viruses and viremia?

the infected animal can infect a new vector before it seroconverts and maybe before it shows clinical signs

why is is important to understand serology results?

lack of detection of antibody to an antigen may not mean that the animals is not infected, just that we tested to early for the primary response to be detected

exposure to pathogen should result in...

seroconversion whether the infection leads to disease or not

Recently a dog was transported from a country where Disease "A" caused by bacterium "A" does no exist to a country where Disease "A" does exist. The incubation period for disease "A" is 5-7 days. 14 days after entering the country, the dog presents with clinical signs of 5 days duration that are compatible with Disease "A". What would you most likely observe in teh serum at this time if it does have Disease "A"?

high IgM and low IgG antibodies to bacterium "A" antigens

3 multiple choice options

Virus "A" causes neurological disease in pigs. The incubation period is from 7-21 days. A pig has clinical signs compatible with disease due to virus

"A". Importantly, these clinical signs are also compatible with disease "B" and disease "C". An antibody test done on a serum sample taken on day 8 of the pig's illness comes back negative for antibodies to Virus "A". All of the controls for the test worked as expected. What is the best interpretation for this result?

it is unlikely that the pig's clinical signs are due to disease "A"

3 multiple choice options

Virus A and Virus B share epitopes x, y, and z. These epitopes are not shared by other viruses. Some of the clinical signs of the diseases caused by these viruses are the same. A test is developed to detect antibodies to Virus A epitopes x, y, and z. Serum from an animal suspected to have disease due to Virus A is tested and the results are positive. What can one conclude from these results?

the animal was exposed to either Virus A or B or both

3 multiple choice options

how do we determine the amount of antibody to a particular antigen in a serum sample?

by testing increasing dilutions of the serum for antibody reactivity to the known antigen of interest

titration

the dilution series of the serum

titer

the reciprocal of the highest dilution of the serum sample that gives a positive test result

what is highest dilution right before we will no longer see the antibody test positive?

titer = 160

to do dilutions the sample must be...

fluid

what are examples of fluids we could use for a dilution?

1. serum

2. joint fluid

3. CSF

what would an example be of when we could determine titers of things other than the antibody?

determine the amount of free virus in serum

when looking at a dilution series what would a 1:10 dilution mean?

1 mL is serum, 9 mL is diluent

in a series dilution what do we coat the wells with?

a known antigen

how can you determine which patient has the highest titer when looking at a well of the dilution series?

the patient with the highest reciprocal serum dilution will have the most antibodies

you testes 10 cows for the antibody to Brucella abortus. All tests negative. You decide to test the cows again 3 weeks later and one tests positive. What does this suggest?

the one cow seroconverted meaning that she had a recent infection since we tested originally

what are the possible interpretations in a serology on a dog is negative for antibodies to leptospira?

1. the dog was never exposed

2. the dog was recently exposed but has not seroconverted yet

3. the dog was infected in the past but current antibody levels are too low to be detected

what are the possible interpretations in a serology on a dog that is positive for antibodies to leptospira?

1. the dog has been exposed to or vaccinated against lepto

2. do not know if it is currently infected

3. detected cross reacting antibodies

when is acute serum collected?

early after onset of illness

when is covalescent serum collected?n

14-21 days later

why do we take both the acute and convalescent serum samples?

1. we want to see the change in antibody production

2. we want to see what stage of exposure the animal is at (primary vs. memory)

what would a four-fold rise or greater in titer from acute to convalescent serum indicate?

a primary active infection

how must the acute sample and convalescent sample be tested?

in parallel

when explaining why we have two serum tested samples, what is the implication if we have just one sample and it is negative?

one sample could not rule out exposure, we may have tested too early for the antibody to be detected

when explaining why we have two serum tested samples, what is the implication if we have just one sample and it is positive?

we may not know if we have cross-reacting antibodies or specific antibodies being carried over from an old infection, or if animal is currently infected

what would it mean if the test in the acute phase was 0 or very low?

body does not have antibodies, you may have taken sample too early

if the antibodies are due to a current infection what trend should be happening on the graph?

antibody levels should be rising from zero or very low number to a high number that has increased by atleast a four-fold

rising titer

when antibody levels increase

when comparing acute to convalescent titers, what does if mean if the 2 titers remain level or the second one falls?

antigen highly unlikely to be the cause of disease in question

when could acute/convalescent antibody titers be helpful?

1. herd situations such as testing ewes in a flock experiencing abortion

2. animal with acute onset clinical signs compatible with several infectious diseases