Biology Essay on The role of viral non-structural protein in avoiding the host innate immune response



The paper is to discuss the role of the non structural protein 1 also known as NSP1 which is found among the rotavirus as it is known to be responsible in the blockage of interferon also known as IFN. This is done through signaling during the meditation of the proteasome-dependent degradation found with the IFN-regulatory factors which are referred to as IRFs.  This is also called the β-transducin where there is a repeat of elements which contain the proteins where it will be known as β-TrCP. The paper will also highlight some of the ways in which the NSP1 can subvert some of the innate immune responses through various mechanisms.

In the part where the paper will be discussing on the results, one will understand that NSP1 of the rotavirus known, as OSU will twist while binding of IRF3 takes place with the help of NSP1 as it truncates with SA11 so as to enable the degradation of IRFs. This will take place as the host IFN still responds through indicating that other alternative hosts factors have been targeted by NSP1 other than the IRFs.  One will also discover that the over-expression of NSP1 can result to the blockage of  IFN-β activation of the promoter which is induced by retinoic acid inducible gene I also called RIG-I. This will not inhibit the induction of IFN-β activation which is perpetrated mitochondrial antiviral-signaling protein (MAVS) and indicates that the RIG-1 is targeted by NSP1. This will be supported by the Immunoprecipitation experiments which will indicate that the interaction of NSP1 and RIG-1 will bind and result to an independent IRF3. In addition, one will also know that the RGI-1 will be induced by NSP1 to form a proteasome-independent way. The paper will conclude by demonstrating some of the inhibition of RIG-1 as it responds to different types of I IFN with the help of NSP1 as they contribute to the evasion of the immune rotavirus.


            The major cause of acute diarrhea among children below the ages of 5 is Rotavirus which has the cause of death all over the world with the casualties being reported to be approximately 600,000 annually. The retrovirus infection have been effectively and safely reduced with the use of two vaccines pentavalent human-bovine reassortant (Rotateq™) and attenuated human rotavirus strain (Rotarix™) (Estes , 2006). However, this has not facilitated the understanding of mechanisms used in protection of the vaccine and the pathogenic mechanisms of the rotavirus. The main reason for understanding the pathogenic mechanism in the infection of the rotavirus is to identify the strategies used by novels in developing new vaccines and antiviral reagents especially the subverting of the rotavirus and evasion of host anti viral responses (Estes , 2006).

The innate immune response toward viral infection

            The first line of the host defense adjacent to the virus infection constitutes the type 1 interferon that is mediated by the immune response. The host cells will respond to the viral infection through the production of IFNs, which will further trigger other various genes to express themselves through involving themselves in responding to Activator of Transcription (JAK/STAT) and Janus Kinase/Signal Transducer pathway (Bergmann, et al, 2000).  Downstream immune events are stimulated by the IFNs that will lead to the activation of the immune cells, which are specifically involved in the adaptation of immune responses. Some of the viruses have evolved their viral product that suppresses the mediation of IFN signaling pathways by counteracting their responses, which are induced by IFN-α/β.

            The innate immune response is considered to respond to pathogens in a way which is generic. This is deferent from adaptive immune system, as the protection is not long lasting to the host. The defense offered against infections by the innate immune system is immediate and is in both animals and plants. On the other hand, the defense strategy offered is evolutionary and changes from time to time (Lamb & Parks, 2007).

The strategies viruses use to subvert the immune response

            The rotaviruses are members of the Reoviridae family which are icosahedra viruses that are non-enveloped. These viruses contain 11 segments that are double stranded RNA genome and are found within particles which are triple layered. The genome rotaviruses encode six structural proteins known as VPs and six non-structural proteins known as NSPs. Two sets of structural proteins form the virion (Donelan, et al, 2003). These are VP1 to 4 and VP 6 to 7.  The NSPs function together in the dsRNA replication to translate and transcribe the viral mRNA and maturation of the viral particles. Rotavirus NSP1 contain 55-KDa of RNA binding of protein with a rotavirus gene 5. The interaction of the host signaling proteins and NSP1 are vital for the rotavirus in subverting of innate immune responses.

The mechanism used by NSP1 in signaling of the innate immune responses can be represented through, first, proteasome-dependent degradation is induced by NSP1 through the transcription of the interferon factors. These are IRF3, IRF7, and IRF5 which are used to inhibit IFN response. Secondly, NSP1 will inhibit the nuclear factor-κB (NF-κB) which is activated through inducing of proteasome-dependent while at the same time degrading β-transducin. This will be done continuously to the proteins containing β-TrCP and the subsequent transcription of IFN-β gene (Bergmann, et al, 2000).  Thirdly, the cellular antivirus is antagonized efficiently by rotavirus as the accumulation of the nuclear STAT1, STAT2, and NF-κB is prevented.

Among the rotavirus strains, the NSP1 is the least conserved protein. That is the reason why it has an effect which is specific to the innate immunity. This has lead to the conclusion of the experiments to establish that it targets some degrades of β-TrCP, some degrades of IRFs and in some cases both (Lamb & Parks, 2007). For example, it may not be possible for IRFs degradations to be induced by porcine OSU strain NSP1 but at the same time degradation of β-TrCP will be induced. Therefore, NSP1 can be classified with IRFs and β-TrCP to be in a position of targeting the cellular substrates which are involved in signaling the pathways of the antiviral. In the investigation to find out whether other proteins involved in IFN response can be targeted by the NSP1, it is discovered that NSP1 is capable of inhibiting virus-induced activation which is related to the promoter of IFN-β and is the degradation of IRF3 (Donelan, et al, 2003).

Mechanism 1 Cells and Viruses

            In this methodology, the embryo kidney cell is used. This is a 293FT put into Invitrogen, Carlsbad, CA and cultured in Eagles medium which is modified by Dulbecco and is referred to as DMEM; Invitrogen. This will have a supplement of 10% fetal bovine serum also known as FBS; HyClone, Logan, UT. An additional penicillin of 100 U/ml and streptomycin of 100 μg/ml is added at 37°C in a 5% CO2humidified atmosphere (Bergmann, et al, 2000).

Mechanism 2 Transfection

            Cells of 293FT are added to a confluence of 70 to 80 percent in 24-well plates. Transfection is done in 6-well plates or dihes that are 10 cm with plasmids which are indicated with Lipofectamine 2000 (Invitrogen). The harvested cells after 48 hours were lysed in RIPA buffer (Bergmann, et al, 2000).


            This paper has broken down the possibilities of the interaction of NSP1 proteins with RIG-I which helps with the mediating down of RIG-I as it interferes with the signaling of the pathways. This shows the role of viral non-structural protein in avoiding the host innate immune response (Geiss, 2002). The cells and viruses used include the human kidney, modified Eagles medium, fetal serum African monkey kidney, penicillin, streptomycin, Rotavirus SA11 strain and Sendai virus. The viruses which were put into action include, Transfection, rotavirus infection, Luciferase reporter assay, Immunoprecipitation, Reverse transcription-polymerase chain reaction (RT-PCR), and the western blot.


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