China
Africa
Explore chapters and articles related to this topic
Toxoplasma gondii
Published in Peter D. Walzer, Robert M. Genta, Parasitic Infections in the Compromised Host, 2020
Acute and chronic infection with Toxoplasma have paradoxical effects on the cell-mediated immune system. Chronic infection with Toxoplasma confers upon mice nonspecific resistance to a variety of intracellular pathogens and to transplantable and autochthonous tumors. However, acute and chronic infection with Toxoplasma also appear to have a profound immunosuppressive effect on other immunological functions. Strickland et al. (146) and Huldt (147) demonstrated that the primary humoral response to immunization with sheep red blood cells in mice chronically infected with Toxoplasma was depressed compared with uninfected controls. In addition, Huldt et al. noted severe atrophy of the thymus associated with acute infection (148). Hibbs et al. (149) also showed that chronically infected mice that were reinfected with the same strain of Toxoplasma had a suppressed primary antibody response to sheep red blood cells and to tetanus toxoid; however, the secondary antibody response to both sheep red blood cells and tetanus toxoid remained intact. In addition, primary humoral response in mice to Clostridium welchii typhii vaccine, louping ill virus vaccine, bovine serum albumin, and live louping ill virus has been depressed in mice with Toxoplasma (150). Buxton et al. (151) demonstrated that the antibody response to enzootic abortion vaccine and louping ill vaccine was significantly depressed in sheep infected for 7 or 28 days with Toxoplasma compared with uninfected controls.
Recombinant Antibodies
Published in Siegfried Matzku, Rolf A. Stahel, Antibodies in Diagnosis and Therapy, 2019
Melvyn Little, Sergey M. Kipriyanov
Cytoplasmic expression in BSR cells (a clone of baby hamster kidney cells) of scFv against the envelope protein of the tick-borne flavivirus was shown to significantly reduce the infectivity of the louping ill virus (Jiang et al., 1995). Analogously, the expression of scFv that recognizes the CD4 binding region of the HIV-1 envelope protein in ER of COS cells inhibited env protein maturation and led to the reduction of envelope protein-mediated syncytia formation (Marasco et al., 1993). Recombinant antibody fragments can be targeted to different subcellular compartments: to the cytoplasm by removal of the hydrophobic amino acid core sequence of the signal peptide (Biocca et al., 1995), to the endoplasmic reticulum by adding a C-terminal ER retention signal (Richardson et al., 1995), to the nucleus by adding the nuclear localization signal to the N-terminus of the antibody fragment (Biocca et al., 1995) and even to mitochondria by fusion with the N-terminal presequence of cytochrome c oxidase (Biocca et al., 1995). The expression levels of the mutated antibody domains vary, according to the type of targeting signal, from high expression levels for those fragments localized in ER to much lower levels for the cytosolic and nuclear scFvs, with the mitochondrial scFv displaying intermediate levels (Biocca et al., 1995).
Tick-Borne Encephalitis
Published in Sunit K. Singh, Daniel Růžek, Neuroviral Infections, 2013
Daniel Růžek, Bartosz Bilski, Göran Günther
Recently, a new taxonomic scheme based on the comparison of the complete coding sequences of all recognized tick-borne flavivirus species has been proposed. This suggests the assignment of TBEV and Louping ill virus to a unique species (TBEV) including four viral types (i.e., Western Tick-borne encephalitis virus, Eastern Tick-borne encephalitis virus, Turkish sheep Tick-borne encephalitis virus, and Louping ill Tick-borne encephalitis virus) (Grard et al. 2007). However, this classification has not been approved by the International Committee for Taxomony of Viruses yet, and it is not widely accepted since it combines viruses with different biological characteristics into one species.
Low prevalence of tick-borne encephalitis virus antibodies in Norwegian blood donors
Published in Infectious Diseases, 2021
Åshild Marvik, Yngvar Tveten, Anne-Berit Pedersen, Karin Stiasny, Åshild Kristine Andreassen, Nils Grude
Interference caused by flavivirus cross-reactive antibodies, due to common antigenic sites within the E protein, is well documented with the ELISA method among several flaviviruses that infect humans, like Japanese encephalitis virus, dengue virus and yellow fever virus [38,43–45]. A comparative study of different commercial TBEV IgG-ELISA kits, including Enzygnost, revealed particularly specificity problems with dengue virus IgG [45]. In the current study, exposure to other flaviviruses, either through vaccination or undergone infections, were obtained. Two of the three donors with a history of dengue fever had a reactive TBEV IgG ELISA due to cross-reactivity. In addition, at least two other donors had a reactive ELISA due to vaccination against Japanese encephalitis and/or yellow fever. Thus, at least four cases of flavivirus cross-reactive antibodies were observed. Skarpaas et al. did not assess false-positive TBEV IgG ELISA results due to any flavivirus exposure, while Thortveit et al. obtained information about TBE and/or yellow fever vaccinations. According to the literature, and our observations, a history of dengue fever is an important flavivirus exposure to identify. Louping-ill virus (LIV) is another flavivirus transmitted by I. ricinus ticks and is antigenically closely related to TBEV [44]. LIV can cause encephalomyelitis of sheep and is mainly restricted to the British Isles. However, LIV infections in sheep have been reported in Norway although the last case was in 1991 [46,47]. LIV is a rare cause of human disease and no human cases have ever been reported in Norway [48]. Thus, at present, cross-reactivity due to LIV antibodies is not a current issue.