Infect and persist

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As Infect-and-persist mechanism (of English infect and persist , infect and remain ') or Persistent infection is used in medicine one of the two main types of infectious gradients in the infection of living things by pathogens referred. It is characterized by a relatively moderate reproduction rate , a lower burst size , a lower viral load and a long duration of the disease.

The other type of gradient is called hit and run .

mechanism

Persistent pathogens use a wide variety of mechanisms to bypass the immune response ( immune evasion ). After infection, for example, a lysogenic (synonym: latent) virus can dormant in the host and usually leads to a very limited infectious disease. In the course of this, the host (or host cell) hardly excretes any viruses, and in the course of an immune reaction the virus is usually not eliminated from the organism. For example, the translation of viral proteins is throttled in the latent phase . Furthermore, pathogens can withdraw into cell types with immune privilege where the resources of the immune system are limited (e.g. neurons or stem cells ). A further persistence mechanism can be found in pathogens with strongly varying genomes (e.g. HIV or hepatitis viruses of type B or C), which can escape an immune reaction through mutations while maintaining their functions ( escape mutants ). The host then often remains permanently infected. In bacteria and fungi , spores also occur as resting forms.

The persistent infection type occurs in pathogens that have developed persistence mechanisms adapted to their host , or in viruses against which the host does not develop antibodies and cytotoxic T cells very effectively due to a continuous change in the pathogen , which can eliminate the viruses (escape mutation) . After the infection of such an organism, in the best case scenario, there are even no consequences of the illness ( inapparent infection ), or an acute phase of illness may develop, which the organism in question usually survives well. During this entire time, the organism is available to the virus for its own reproduction. Even if a clinical illness does not last very long, this type of infection is referred to as infect-and-persist if the virus is not completely eliminated (English. Clearance ), but can hide itself from the immune system of the infected organism. In this case, either complete viruses can remain in the body (in cells with immune privilege ) or their genome remains dormant (latent) . In the case of latent pathogens, periodic reactivation of the pathogen and renewed virus excretion is possible (e.g. herpes simplex , HIV after discontinuation of HAART ). In addition, a chronic infection with relatively high virus concentrations (e.g. HIV without therapy, hepatitis B virus or hepatitis C virus ) can also occur. Often develops after years of latency a secondary disease (secondary Leiden) .

Examples

Human medicine

Veterinary medicine

literature

  • S. Modrow, D. Falke, U. Truyen: Molecular Virology. 2nd edition, Spektrum, Heidelberg 2003, ISBN 3-8274-1086-X .
  • DM Knipe, PM Howley, DE Griffin, (Eds.): Fields Virology. 5th edition, Lippincott Williams & Wilkins, Philadelphia 2007, ISBN 978-0-7817-6060-7 .

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