Evasion of the immune response

The use of viral chemokine/receptor mimics and inhibitors identified in particular virus families such as herpesviruses, poxviruses and HIV indicates their importance in pathogensis of these viruses, either for evasion of the immune response as with poxviruses and herpesviruses or addtionally the use of recptors for viral entry as with HIV and poxviruses. Further studies will almost certainly identify a greater range of viruses producing such mimics. 

T cells. Further, they demonstrated that tumor exosomes carry NKG2D ligand, such as MICA (MHC class I polypeptide-related sequence A) and MICE (MHC class 1 polypeptide-related sequence B), triggering a selective down-regulation of cell surface NKG2D. These effects of cancer-cell-derived exosomes may mediate suppression of lymphocyte functions, even in the presence of inflammatory cytokines such as IL-15 (interleukin 15), and therefore may mediate the evasion of the immune response by cancer cells. 

Some bacteria produce HA as a capsular polysaccharide by the HA synthase, which facilitates evasion of the immune response by host organ-... 

Antigenic variation (trypanosomes) Varies Nonreciprocal gene conversion Successive expression of different genes encoding the variable surface glycoproteins (VSGs) allows evasion of host immune response. 

Both rodent CM Vs provide useful systems to analyse virus-host interactions and hence to discern the role of immune-evasive proteins encoded by their genomes. In the case of MCMV, a wealth of knowledge concerning the importance of host genetic factors and dissection of various compartments of the immune response in... 

Evasion of host immunity. Implicit in the ability to invade is the ability to evade host responses that would block parasite migration or be directly lethal to the organism. Mechanisms by which parasite helminths evade the host immune response have been extensively analyzed and debated, and the reader is referred to the numerous reviews on this subject, particularly for the well-studied example of schistosomiasis (26). 

Scalsp In the case of MCMV we find quite a lot of genetic variation in some immune evasion genes. This results in differences in the immune response and how the virus escapes from different arms of the innate and adaptive immune response. 

So far, the described phenotypes that led to the identification of viral genes interfering with the immune response are frequently the modulation of MHC class I functions that affect the CTL and NK response of the host. The description of the loss of MHC class I from the cell surface led to the identification of immune-evasive... 

The immune system has evolved so as to require only minute amounts of antigen for detection of a foreign invader. Herpesviruses have withstood the selective pressure exerted by the host through evasion of the host immune response and have had millions of years to bring these strategies to perfection. The fact that most, if not all, herpesviruses are capable of establishing persistent infections illustrates the effectiveness of the stealth technology employed by these viruses. 

During primary acute infection, and during reactivation, the actively replicating HSV is susceptible to immune attack. During latency in the nervous system, in contrast, the virus is relatively sheltered. During the early events of acute infection HSV is especially vulnerable to the effects of innate immunity such as IFNs. Such innate responses are capable of shaping the future adaptive response to the virus, and it is likely therefore that evasion of innate immunity is... 

Extracellular barriers in systemic delivery involve hurdles to nucleic acid delivery encountered from the point of injection to the surface of the cellular target. For cationic polymer-based systems, these barriers typically include the toxicity of the nanoparticles, interactions with semm proteins, extracellular matrices, and nonspecific cell surfaces, clearance by the innate immune system, aggregation due to physiological salt conditions, and evasion of the adaptive immune response. Ideally, the nanoparticle should (1) remain nontoxic, small, and dis-aete, (2) bypass the immune system, and (3) interact only with the cells of interest. Efforts to prepare polymer systems that endow nanoparticles with these characteristics are discussed below. 

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