Ribavirin: Difference between revisions

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Ribavirin, when administered in combination with pegylated interferon alpha, induces an antiviral state in host cells, resulting in reduced virus replication rates and activation of the host immune system. It is thought that Ribavirin acts as an antiviral agent by disrupting viral RNA synthesis, which would impact both transcription and genome replication in the Hepatitis C virus. However, the exact mechanism by which the drug interferes with this process is unknown. Several theories have been proposed to explain the effect of Ribavirin in inhibiting the replication of the Hepatitis C virus <ref name="paesh"/>.

Immunomodulation by Ribavirin may be responsible for the drug’s antiviral properties. It has been suggested that the natural CD4+ helper T cell response may be altered in the presence of Ribavirin. It is thought that ribavirin may enhance the T helper 1 response, resulting in greater clearance of virus <ref>doi: 10.1111/j.1478-3231.2008.01896.x</ref>. However, there is conflicting evidence suggesting that the T helper 2 response may be implicated in this process instead <ref>doi: 10.1111/j.1440-1746.2008.05320.x</ref>. Another possible mechanism involves the enhancement of interferon-stimulated gene (ISG) expression by Ribavirin. When a cell becomes infected with a virus, it may release interferons. Interferons are signaling molecules that function in a paracrine fashion to induce an antiviral state in neighboring cells, protecting them from infection. Ribavirin is thought to enhance the interferon signaling pathway ~~(Feld et al)~~, resulting in a wider antiviral response. This theory has been supported in studies using cell culture models (Thomas et al). It has also been suggested that the relationship between Ribavirin and inosine 5’-monophosphate dehydrogenase (IMPDH) may impact this process. IMPDH play a significant role in the guanine nucleotide synthesis pathway. It results in the conversion of inosine 5’-monophosphate to xanthine 5’-monophosphate, which is an intermediate for the nucleotide guanosine (Shu et al). Therefore, modulation of IMPDH activity affects a cell’s reservoir of guanosine. Ribavirin has been shown to function as a competitive inhibitor for IMPDH (Streeter et al). Because guanosine triphosphate (GTP) plays a critical role in the viral genome replication process, inhibition of IMPDH would result in the prevention of viral replication.

Immunomodulation by Ribavirin may be responsible for the drug’s antiviral properties. It has been suggested that the natural CD4+ helper T cell response may be altered in the presence of Ribavirin. It is thought that ribavirin may enhance the T helper 1 response, resulting in greater clearance of virus <ref>doi: 10.1111/j.1478-3231.2008.01896.x</ref>. However, there is conflicting evidence suggesting that the T helper 2 response may be implicated in this process instead <ref>doi: 10.1111/j.1440-1746.2008.05320.x</ref>. Another possible mechanism involves the enhancement of interferon-stimulated gene (ISG) expression by Ribavirin. When a cell becomes infected with a virus, it may release interferons. Interferons are signaling molecules that function in a paracrine fashion to induce an antiviral state in neighboring cells, protecting them from infection. Ribavirin is thought to enhance the interferon signaling pathway <ref>doi: 10.1002/hep.21853</ref>, resulting in a wider antiviral response. This theory has been supported in studies using cell culture models (Thomas et al). It has also been suggested that the relationship between Ribavirin and inosine 5’-monophosphate dehydrogenase (IMPDH) may impact this process. IMPDH play a significant role in the guanine nucleotide synthesis pathway. It results in the conversion of inosine 5’-monophosphate to xanthine 5’-monophosphate, which is an intermediate for the nucleotide guanosine (Shu et al). Therefore, modulation of IMPDH activity affects a cell’s reservoir of guanosine. Ribavirin has been shown to function as a competitive inhibitor for IMPDH (Streeter et al). Because guanosine triphosphate (GTP) plays a critical role in the viral genome replication process, inhibition of IMPDH would result in the prevention of viral replication.

Ribavirin has also been shown to act as an inhibitor for eIF4E, a protein of the translation initiation complex (Kentsis et al). Because of its structural similarity to guanosine, it mimics the 7-methyl guanosine mRNA cap, preventing translation. This would result in reduced capacity for viral replication within an infected cell. The Hepatitis C viral genome is replicated by RNA-dependent RNA polymerase (RdRp). A modified form of Ribavirin, Ribavirin 5’-triphosphate (RTP) is also believed to directly inhibit RdRp activity (Graci et al), resulting in lower rates of genome replication. If Ribavirin is converted to the monophosphate form, RMP, it is believed to be incorporated into the viral genome, functioning as a mutagen.

Ribavirin: Difference between revisions

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 Ribavirin, when administered in combination with pegylated interferon alpha, induces an antiviral state in host cells, resulting in reduced virus replication rates and activation of the host immune system. It is thought that Ribavirin acts as an antiviral agent by disrupting viral RNA synthesis, which would impact both transcription and genome replication in the Hepatitis C virus. However, the exact mechanism by which the drug interferes with this process is unknown.  Several theories have been proposed to explain the effect of Ribavirin in inhibiting the replication of the Hepatitis C virus <ref name="paesh"/>.
-Immunomodulation by Ribavirin may be responsible for the drug’s antiviral properties. It has been suggested that the natural CD4+ helper T cell response may be altered in the presence of Ribavirin. It is thought that ribavirin may enhance the T helper 1 response, resulting in greater clearance of virus <ref>doi: 10.1111/j.1478-3231.2008.01896.x</ref>.  However, there is conflicting evidence suggesting that the T helper 2 response may be implicated in this process instead <ref>doi: 10.1111/j.1440-1746.2008.05320.x</ref>.  Another possible mechanism involves the enhancement of interferon-stimulated gene (ISG) expression by Ribavirin. When a cell becomes infected with a virus, it may release interferons. Interferons are signaling molecules that function in a paracrine fashion to induce an antiviral state in neighboring cells, protecting them from infection. Ribavirin is thought to enhance the interferon signaling pathway (Feld et al), resulting in a wider antiviral response. This theory has been supported in studies using cell culture models (Thomas et al). It has also been suggested that the relationship between Ribavirin and inosine 5’-monophosphate dehydrogenase (IMPDH) may impact this process.  IMPDH play a significant role in the guanine nucleotide synthesis pathway.  It results in the conversion of inosine 5’-monophosphate to xanthine 5’-monophosphate, which is an intermediate for the nucleotide guanosine (Shu et al).  Therefore, modulation of IMPDH activity affects a cell’s reservoir of guanosine. Ribavirin has been shown to function as a competitive inhibitor for IMPDH (Streeter et al). Because guanosine triphosphate (GTP) plays a critical role in the viral genome replication process, inhibition of IMPDH would result in the prevention of viral replication.
+Immunomodulation by Ribavirin may be responsible for the drug’s antiviral properties. It has been suggested that the natural CD4+ helper T cell response may be altered in the presence of Ribavirin. It is thought that ribavirin may enhance the T helper 1 response, resulting in greater clearance of virus <ref>doi: 10.1111/j.1478-3231.2008.01896.x</ref>.  However, there is conflicting evidence suggesting that the T helper 2 response may be implicated in this process instead <ref>doi: 10.1111/j.1440-1746.2008.05320.x</ref>.  Another possible mechanism involves the enhancement of interferon-stimulated gene (ISG) expression by Ribavirin. When a cell becomes infected with a virus, it may release interferons. Interferons are signaling molecules that function in a paracrine fashion to induce an antiviral state in neighboring cells, protecting them from infection. Ribavirin is thought to enhance the interferon signaling pathway <ref>doi: 10.1002/hep.21853</ref>, resulting in a wider antiviral response. This theory has been supported in studies using cell culture models (Thomas et al). It has also been suggested that the relationship between Ribavirin and inosine 5’-monophosphate dehydrogenase (IMPDH) may impact this process.  IMPDH play a significant role in the guanine nucleotide synthesis pathway.  It results in the conversion of inosine 5’-monophosphate to xanthine 5’-monophosphate, which is an intermediate for the nucleotide guanosine (Shu et al).  Therefore, modulation of IMPDH activity affects a cell’s reservoir of guanosine. Ribavirin has been shown to function as a competitive inhibitor for IMPDH (Streeter et al). Because guanosine triphosphate (GTP) plays a critical role in the viral genome replication process, inhibition of IMPDH would result in the prevention of viral replication.
 Ribavirin has also been shown to act as an inhibitor for eIF4E, a protein of the translation initiation complex (Kentsis et al).  Because of its structural similarity to guanosine, it mimics the 7-methyl guanosine mRNA cap, preventing translation. This would result in reduced capacity for viral replication within an infected cell.  The Hepatitis C viral genome is replicated by RNA-dependent RNA polymerase (RdRp). A modified form of Ribavirin, Ribavirin 5’-triphosphate (RTP) is also believed to directly inhibit RdRp activity (Graci et al), resulting in lower rates of genome replication.  If Ribavirin is converted to the monophosphate form, RMP, it is believed to be incorporated into the viral genome, functioning as a mutagen.