Immunization
Julius P. Kreier in Infection, Resistance, and Immunity, 2022
Artificially induced immunity may not be complete, and even with generally functional vaccines, one cannot always assume that protection has developed after immunization. One way of evaluating the immune response following injection of vaccine is the measurement of circulating antibodies to the antigens in the vaccine. The process of development of antibodies is called seroconversion. In some instances, the presence of circulating antibodies correlates well with development of protection. This is the case with hepatitis B and rubella vaccines. Antibody levels, however, do not tell the whole story. If there is a strong immunologic memory response, protection may exist in the absence of detectable antibody. For example, following vaccination with agents such as live attenuated measles and rubella vaccines, there will be an initial IgM antibody response, followed by a rise in IgG antibody titers. Over time, the antibody titers will fall, and although they may fall to undetectable levels, when infection occurs there is a rapid response by the memory cells. In such situations there is a prompt increase in IgG antibodies specific for the virus and protection from disease. The mere presence of antibody, however, may not be sufficient to assure protection from disease, but rather a minimum level of antibody may be required. Such is the case if immunity to tetanus is to be induced by injection of tetanus toxoid.
Trichinella
Dongyou Liu in Handbook of Foodborne Diseases, 2018
The diagnosis of trichinellosis should be based on the anamnesis (source of infection, amount of infected meat ingested, number of larvae present in the infected meat, when possible, and number of cases in the epidemic focus), clinical evaluation (recognition of the signs and symptoms of trichinellosis and definition of the form of the disease, on which significantly depends the choice of treatment), and laboratory tests (immunodiagnosis and/or detection of larvae in a muscle biopsy). An algorithm that can be used for the diagnosis is shown in Table 83.2. The most highly recommended technique is serology by enzyme-linked immunosorbent assay (ELISA) with excretory-secretory antigens, which gives the highest ratio between sensitivity and specificity and is best used in combination with immunoblotting, still with excretory-secretory antigens to confirm ELISA positive samples (Figure 83.3). Seroconversion occurs between 12 (in severe or moderate cases) and 60 (in mild or asymptomatic cases) days postinfection.
Supplemental Tests for HIV-1 Infection
Niel T. Constantine, Johnny D. Callahan, Douglas M. Watts in Retroviral Testing, 2020
No universally accepted criteria define a positive WB profile. Several organizations have formulated their own requirements for a WB result considered to be positive. The lack of consensus among these organizations reflects the still-incomplete understanding of the immune response, or disagreement in the interpretation of reactive bands. There is inconsistency in the immune responses from some individuals, making a general interpretation of results difficult. It is also difficult to determine whether certain antibody profiles are indicative of true infection. Some individuals who exhibit reactivity to p24 and p55 will later be shown to seroconvert, indicating that a p24 and p55 profile can be indicative of early infection. Conversely, other individuals may have the identical profile for long periods of time (years) and never exhibit evidence of seroconversion or even seroprogression (i.e., they are not infected). In fact, most indeterminate WB results from noninfected individuals exhibit the p24 and/or p55 profile.
New insights in Coxiella burnetii infection: diagnosis and therapeutic update
Published in Expert Review of Anti-infective Therapy, 2020
Cléa Melenotte, Matthieu Million, Didier Raoult
Serology remains the main tool to diagnose C. burnetii infection. Seroconversion is usually detected within the 6 weeks after the onset of symptoms and is estimated to be positive in 90% of the cases 3 weeks after initial symptoms. Indirect immunofluorescence antibody test (immunofluorescence assay, IFA), complement fixation, ELISA and microagglutination are the techniques the most used to diagnose Q fever, the first three being commercially available [21]. IFA remains the reference method because of its simplicity and accuracy [22,23]. As most reference laboratories have developed their own immunofluorescence test and the serological tests used are sometimes variable in the event of an outbreak, the comparison of serological levels and the exploitation of the cutoff remain difficult. Cross reactivity have been described with Legionella micdadei (34%) and Bartonella (50%) [24,25].
Rigid monoclonal antibodies improve detection of SARS-CoV-2 nucleocapsid protein
Published in mAbs, 2021
Curtis D. Hodge, Daniel. J. Rosenberg, Patricia Grob, Mateusz Wilamowski, Andrzej Joachimiak, Greg L. Hura, Michal Hammel
SARS-CoV-2 nucleocapsid proteins (NP) are critical for incorporating and packaging viral genomic RNA into mature virions. In infected cells, NPs are produced in large amounts from subgenomic mRNA and are present at the replication-transcription complexes (RTCs), the sites of RNA synthesis. The NP gene is relatively conserved, with a sequence identity of 91% and 50% to SARS-CoV and MERS-CoV, respectively, and is rather stable, as it acquires few mutations over time.1,2 Although the NP from SARS-CoV-2 is abundant and highly immunogenic,3–5 most SARS-CoV-2 detection assays use different spike protein regions as the antigen in immunoassays. This is mainly because antibodies against the spike protein are believed to be less cross-reactive6 and are expected to correlate better with neutralizing capacity.7 Testing for serum antibodies against NP from SARS-CoV-2 was suggested to increase diagnostic capacity.4,8,9 However, serological assays cannot achieve diagnosis early in the onset of an infection because seroconversion occurs after 7–10 days in patients.3,4,10
Benznidazole for the treatment of Chagas disease
Published in Expert Review of Anti-infective Therapy, 2021
Irene Losada Galván, Julio Alonso-Padilla, Nuria Cortés-Serra, Cristina Alonso-Vega, Joaquim Gascón, María Jesús Pinazo
Seroconversion is also a consequence of the acute phase of the infection. Levels of anti-parasitic immunoglobulins rise and remain steady for years (mainly IgG class). Although beneficial toward achieving a diagnosis of the chronic stage by serological methods, the long-standing seropositive state largely precludes an early assessment of treatment efficacy. This is because levels of anti-T. cruzi IgG stay above their detection threshold despite the intake of anti-parasitic treatments. The consequence is that the evaluation of treatment response cannot be made early upon its administration by means of currently available serological tools. These might only be useful decades after treatment, which is the time that takes for anti-T. cruzi IgG levels to lower and become negative again in the absence of re-infection events [55]. This time-span offers an absolutely impractical perspective both for the management of patients in the daily clinic as well as for the evaluation of new drugs in clinical trials [56]. In search of a solution, several biomarkers are under research at present, including parasite-derived and host-derived ones [56]. But, despite advancements in the past few years, still there are no biomarker-based tests available for the early assessment of treatment efficacy.
Related Knowledge Centers
- Adaptive Immune System
- Antibody
- Humoral Immunity
- Immunization
- Immunology
- Isotype
- Vaccination
- Infection
- Antigen
- Immunodeficiency