54 Serology

Exam 2

what happens to antibody concentrations in persistent or chronic infections

both Igm and IgG may remain detectable for an extended period

why are serotypes important in dengue

antibodies to one serotype wont be effective against other serotypes

can become infected with serotype 1, then infected with serotype 2, and the serotype 1 antibodies offer no protection

have to be sure to test for all serotypes

what is serology

the study of serum and other body fluids

what does serology mean in practice

the diagnostic idenitifcation of antibodies in ther serum

what are serotypes

distinct groupings within a microorganism species or immune cells, classified by shared surface antigens that trigger specific immune responses

why do serotypes matter

differetn serotypes express distinct surface antigens

these unique antigens trigger distinct, non cross reactive antibody responses

how can serotypes be differentiated

neutralizing antibodies

agglutination tests

what is variant based on

genotype

what is serotype based on

serology- neutralizing antibodies

why is there only one rabies vaccine

all rabies variants can be neutralizd by the same antibodies generated by the rabies vaccine

what is the infectious period

time during which the infected individual can infect another individual

what does serology say when first symptomatic

usually negative

what is seroconversion

point at which specific antibodies become detectable in the blood serum follwoing infection or vaccination

when do seroconversion occur

typically within 1-2 weeks after exposure

what factors influence detection in serology

assay sensitivity (ability to detect low levels)

assay specificity (ability to avoid false positives)

why does seroconversion not mean protection all the time

only some concentrations may offer protection

sometimes cell mediated immunity is needed

what animals may not have seroconversion

when an animal is immunosuppressed

many animals develop clinical rabies and never seroconvert- why we check brain

when is infectiousness at its highest in mant infectious diseases

before seroconversion

can be before clinical signs

what viruses can cause an animal to infect a new vector being it seroconverts

west nile virus

eastern equine encephalities virus

why is seroconversion important for interpreting serology results

lack of detection of an antibody may not mean the animal isnt exposed

it could be too early for a primary antibody response to be detected

why else is understanding seroconversion important

screening blood for dontation

knowing when to test

how do we quantify the amount of antibody to a particular antigen of interest

titration and titers

what do titration and titers show

the amount of antibody (to a particular antigen) in a serum sample is determined by testing increasign diltuions of the serum for antibody reactivity (a positive test) to know the known antigen of interest

What is titration

the dilution series of the serum

what is a titer

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

what are common diltuion series

1:10 or 1:8

1:2, 1:4, 1:8, 1:16, 1:32, 1:64

what is a positive result on a titer

a change in color

what is acute serum

serum collected early after onset of illness

what is convalecent serum

serum collected 14-21 days later

what is compatible with a diagnosis of an active infection with acute vs convalescent serum

a four fold (4 dilutions) or greater in titer from acute to convalescent

id one sample is positive, what might be skewing the results

if it is cross reacting antibodies or specific antibodies carried over from an old infection/vaccine

if the antibodies are due to current infection, what should the 2 tests show

0 or very low at first, then high, 4 fold or greater

what is a rising titer

when antibodies level rise over a 2-3 week period with 1st exposure

what is the summary of seroconversion

when antibodies go from 0 to positive

what 2nd test result would show that the positive came from a past infection/vaccination

if the second test remains low

what is the purpose of paired serology (acute and convalescent samples)

to interpret antibody titers and identified recent infection

how is paired serology used in individual animals

may not be helpful to the dog, but shows clinicians what is being transmitted in the community