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Pregnancy After Liver and Other Transplantation
Published in Vincenzo Berghella, Maternal-Fetal Evidence Based Guidelines, 2022
Cytomegalovirus (CMV) infection represents a serious viral infection often occurring within 6–12 months post-transplant. Unfortunately, it is deleterious in early pregnancy given its causality of congenital malformation (microcephaly, cerebral palsy, sensorineural deafness) or congenital liver disease with an incidence of 10–15% of infected pregnancies. It is advisable to screen all transplant recipients with CMV IgG and IgM. If IgM positive, avidity testing should be performed (Chapter 49). The use of antiviral agents in the management of CMV infection during pregnancy remains controversial (Chapter 49) [10].
Breast Imaging with Radiolabeled Antibodies
Published in Raymond Taillefer, Iraj Khalkhali, Alan D. Waxman, Hans J. Biersack, Radionuclide Imaging of the Breast, 2021
Lamk M. Lamki, Bruce J. Barron
The next consideration in the choice of an antibody is the avidity and the affinity of the antibody. The attraction and the strength between the antibody and the antigen and the bond with the radiolabel may determine the success of immunoscintigraphy. The significance of avidity and affinity in imaging results has not been fully realized clinically. However, in theory and in in vitro experiments, these two factors do matter in the outcome of immunoscintigraphy. Another important consideration is the labeling efficiency and bonding between the isotope and the antibody both in vitro after labeling procedure and in vivo after intravenous injection. The impact of dehalogenation of iodinated antibodies after injection has already been discussed. This occurs in vivo independent of labeling efficiency, and contributes to high background activity and poor images. Detailed discussion of these and other factors related to labeling and antibody properties that can affect biodistribution are beyond the scope of this chapter. Likewise, strep-avidin and biotin have been used by several workers to improve labeling and targeting, but discussion of that has to be deferred to specialized texts.
Infectious Disease Data from Surveillance, Outbreak Investigation, and Epidemiological Studies
Published in Leonhard Held, Niel Hens, Philip O’Neill, Jacco Wallinga, Handbook of Infectious Disease Data Analysis, 2019
A separate area of microbiological testing is aimed at documenting indirect evidence of infection by assessing the body’s immunological response to it. These methods also are used to assess vaccine induced immunity. The immune response to infection (and vaccination) usually consists of two different mechanisms: a cellular and a humoral response. In the cellular response, immune cells directly attack the pathogen, while the humoral response acts through antibodies. Microbiological tests aimed at diagnosing infections by assessing the immune response are focused mostly on testing the presence of humoral rather than cellular immunity, since standardized assays for the latter are lacking. Data resulting from microbiological tests of humoral immunity can give qualitative and quantitative results about the presence of antibodies specific for a certain pathogen. It also can give an indication of when the infection was acquired by performing avidity testing, which is used in e.g. HIV diagnosis and surveillance [2].
Multi-functional antibody profiling for malaria vaccine development and evaluation
Published in Expert Review of Vaccines, 2021
D. Herbert Opi, Liriye Kurtovic, Jo-Anne Chan, Jessica L. Horton, Gaoqian Feng, James G. Beeson
Avidity refers to the total binding force between an antibody and antigen. It is not only a product of individual affinities, or binding strength at a single site, but is affected by epitope density and the valency of both binding partners [96]. It is frequently used to describe the overall binding strength of polyclonal antibodies in human serum. Heightened avidity may be used to indicate a sustained immune response as it can reflect the increase in antibody affinity which occurs over the course of an infection due to B cell somatic hypermutation and affinity maturation [97]. As a result, avidity has been used as a marker of the duration of an immune response or successful vaccination for several pathogens [98-101]. However, the role of avidity in malaria is less defined. In malaria-endemic regions, increased avidity of antibodies targeting key proteins has been associated with age and antibody titer, indicating that avidity improves with developing immunity, but this is not consistently observed [102-104]. Others reported an inverse relationship between avidity and transmission intensity thus suggesting that repeated or ongoing infection may hinder rather than support affinity maturation [105].
Immune surveillance for vaccine-preventable diseases
Published in Expert Review of Vaccines, 2020
Gerco den Hartog, Rob van Binnendijk, Anne-Marie Buisman, Guy A. M. Berbers, Fiona R. M. van der Klis
The detection of antigen-specific antibodies has been paramount in the immune surveillance of infectious diseases. While antibody concentration is the most frequently used parameter to define immune protection, the definition of correlates of protection (CoP) based on detected antibody levels alone remains challenging. This can have various reasons, such as which antibodies protect, whether protection is dependent on systemic antibodies, local antibodies, or both, or whether protection is more dependent on cellular mechanisms rather than antibodies [23]. Also, the provided cutoffs should not be regarded as a conservative or fixed value, as there are numerous examples of infections also occurring in persons with pre-exposure antibody levels above the specified cutoff, e.g. in high exposure settings. To answer some of these questions functional assays have been developed to assess the quality of antibodies. At the antibody level, a first indicator for quality is the binding strength of IgG antibodies referred to as antibody avidity. The avidity index determines which proportion of the antibodies is of high affinity, and a better predictor of the antibodies to bind to the pathogen in vivo [74]. The avidity helps in defining the maturation process of the antibody response following antigenic contact by vaccination or infection.
Measuring the effects of macromolecular crowding on antibody function with biolayer interferometry
Published in mAbs, 2019
Dorothy M. Kim, Xiao Yao, Ram P. Vanam, Michael S. Marlow
We also performed standard avidity measurement experiments with antigen-loaded biosensor tips to detect antibody binding. To do this, we site-specifically biotinylated the antigen and loaded it onto the streptavidin-coated biosensor tip. By immobilizing the smaller antigen rather than the mAb, the change in response (in nm) resulting from binding of antibody gave a more pronounced signal, and thus improved signal to noise. Figure 3 shows the results from the standard BLI experiment performed to determine binding affinity for each mAb under ideal solution conditions. The slow dissociation kinetics do not enable an accurate estimate of apparent KD, but the tight binding indicates sub-nanomolar functional binding avidity, which is consistent with Biacore SPR data (not shown).