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A single site for N-linked glycosylation in the envelope glycoprotein of feline immunodeficiency virus modulates the virus-receptor interaction.

Willett BJ, McMonagle EL, Logan N, Samman A, Hosie MJ - Retrovirology (2008)

Bottom Line: Prototypic FIV vaccines based on the FL4 strain of FIV contain a cell culture-adapted strain of FIV Petaluma, a CD134-independent strain of FIV that interacts directly with CXCR4.In addition to a characteristic increase in charge in the V3 loop homologue of FIVFL4, we identified two mutations in potential sites for N-linked glycosylation in the region of FIV Env analogous to the V1-V2 region of HIV and SIV Env, T271I and N342Y.The T271I mutation did not confer CD134-independent infection upon GL8 or CPG41, nor did it increase the affinity of the CXCR4 interaction, suggesting that the principal effect was targeted at reducing the complexity of the Env-CD134 interaction.

View Article: PubMed Central - HTML - PubMed

Affiliation: Retrovirus Research Laboratory, Institute of Comparative Medicine, Faculty of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow, G61 1QH, UK. b.willett@vet.gla.ac.uk

ABSTRACT
Feline immunodeficiency virus (FIV) targets helper T cells by attachment of the envelope glycoprotein (Env) to CD134, a subsequent interaction with CXCR4 then facilitating the process of viral entry. As the CXCR4 binding site is not exposed until CD134-binding has occurred then the virus is protected from neutralising antibodies targeting the CXCR4-binding site on Env. Prototypic FIV vaccines based on the FL4 strain of FIV contain a cell culture-adapted strain of FIV Petaluma, a CD134-independent strain of FIV that interacts directly with CXCR4. In addition to a characteristic increase in charge in the V3 loop homologue of FIVFL4, we identified two mutations in potential sites for N-linked glycosylation in the region of FIV Env analogous to the V1-V2 region of HIV and SIV Env, T271I and N342Y. When these mutations were introduced into the primary GL8 and CPG41 strains of FIV, the T271I mutation was found to alter the nature of the virus-CD134 interaction; primary viruses carrying the T271I mutation no longer required determinants in cysteine-rich domain (CRD) 2 of CD134 for viral entry. The T271I mutation did not confer CD134-independent infection upon GL8 or CPG41, nor did it increase the affinity of the CXCR4 interaction, suggesting that the principal effect was targeted at reducing the complexity of the Env-CD134 interaction.

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Sensitivity of GL8 WT and T271, N342Y and Δ2N mutants to virus neutralising antibody. HIV (FIV) pseudotypes bearing the WT, T271, N342Y or Δ2N Envs were incubated with 1/100, 1/1000 or 1/10,000 dilutions of plasma from 8 GL8-infected cats (Q251-258), or a no plasma negative control (neg), and plated onto CLL-CD134 cells. Luciferase activity was assayed at 72 hrs post-infection. (A) Luciferase activity (counts per minute), each point represents the mean of three replicates +/- SE, (B) Percent neutralisation relative to no plasma control.
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Figure 7: Sensitivity of GL8 WT and T271, N342Y and Δ2N mutants to virus neutralising antibody. HIV (FIV) pseudotypes bearing the WT, T271, N342Y or Δ2N Envs were incubated with 1/100, 1/1000 or 1/10,000 dilutions of plasma from 8 GL8-infected cats (Q251-258), or a no plasma negative control (neg), and plated onto CLL-CD134 cells. Luciferase activity was assayed at 72 hrs post-infection. (A) Luciferase activity (counts per minute), each point represents the mean of three replicates +/- SE, (B) Percent neutralisation relative to no plasma control.

Mentions: The predicted N-linked glycosylation sites ablated by the T271I and N342Y mutations are highly conserved among field isolates of FIV and reinstated rapidly (as early as 1 month post-infection) following in vivo replication of mutant virus [87]. These data suggest that the predicted N-link glycosylation sites at N269 and N342 are critical for maintaining the replicative capacity of the virus in vivo. It is possible that glycosylation at these sites protects the virus from virus neutralising antibody (VNA), thus the sensitivity of HIV(FIV) pseudotypes bearing the wild type GL8 Env or the T271I, N342Y and Δ2N mutants to sera from 8 cats infected with GL8 (4 years post-infection) was compared. Of the 8 sera evaluated, 5 sera (Q251, Q253, Q254, Q255 and Q256) contained potent virus neutralising activity (>90% neutralisation at 1/100, Fig. 7) while more modest neutralising activity was detected in sera from Q252, Q257 and Q258 (Fig. 7). There was no consistent difference in sensitivity to VNA between the WT and the T271I, N342Y and Δ2N mutants, suggesting that this region is not a major target for the humoral response to wild type virus.


A single site for N-linked glycosylation in the envelope glycoprotein of feline immunodeficiency virus modulates the virus-receptor interaction.

Willett BJ, McMonagle EL, Logan N, Samman A, Hosie MJ - Retrovirology (2008)

Sensitivity of GL8 WT and T271, N342Y and Δ2N mutants to virus neutralising antibody. HIV (FIV) pseudotypes bearing the WT, T271, N342Y or Δ2N Envs were incubated with 1/100, 1/1000 or 1/10,000 dilutions of plasma from 8 GL8-infected cats (Q251-258), or a no plasma negative control (neg), and plated onto CLL-CD134 cells. Luciferase activity was assayed at 72 hrs post-infection. (A) Luciferase activity (counts per minute), each point represents the mean of three replicates +/- SE, (B) Percent neutralisation relative to no plasma control.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2563026&req=5

Figure 7: Sensitivity of GL8 WT and T271, N342Y and Δ2N mutants to virus neutralising antibody. HIV (FIV) pseudotypes bearing the WT, T271, N342Y or Δ2N Envs were incubated with 1/100, 1/1000 or 1/10,000 dilutions of plasma from 8 GL8-infected cats (Q251-258), or a no plasma negative control (neg), and plated onto CLL-CD134 cells. Luciferase activity was assayed at 72 hrs post-infection. (A) Luciferase activity (counts per minute), each point represents the mean of three replicates +/- SE, (B) Percent neutralisation relative to no plasma control.
Mentions: The predicted N-linked glycosylation sites ablated by the T271I and N342Y mutations are highly conserved among field isolates of FIV and reinstated rapidly (as early as 1 month post-infection) following in vivo replication of mutant virus [87]. These data suggest that the predicted N-link glycosylation sites at N269 and N342 are critical for maintaining the replicative capacity of the virus in vivo. It is possible that glycosylation at these sites protects the virus from virus neutralising antibody (VNA), thus the sensitivity of HIV(FIV) pseudotypes bearing the wild type GL8 Env or the T271I, N342Y and Δ2N mutants to sera from 8 cats infected with GL8 (4 years post-infection) was compared. Of the 8 sera evaluated, 5 sera (Q251, Q253, Q254, Q255 and Q256) contained potent virus neutralising activity (>90% neutralisation at 1/100, Fig. 7) while more modest neutralising activity was detected in sera from Q252, Q257 and Q258 (Fig. 7). There was no consistent difference in sensitivity to VNA between the WT and the T271I, N342Y and Δ2N mutants, suggesting that this region is not a major target for the humoral response to wild type virus.

Bottom Line: Prototypic FIV vaccines based on the FL4 strain of FIV contain a cell culture-adapted strain of FIV Petaluma, a CD134-independent strain of FIV that interacts directly with CXCR4.In addition to a characteristic increase in charge in the V3 loop homologue of FIVFL4, we identified two mutations in potential sites for N-linked glycosylation in the region of FIV Env analogous to the V1-V2 region of HIV and SIV Env, T271I and N342Y.The T271I mutation did not confer CD134-independent infection upon GL8 or CPG41, nor did it increase the affinity of the CXCR4 interaction, suggesting that the principal effect was targeted at reducing the complexity of the Env-CD134 interaction.

View Article: PubMed Central - HTML - PubMed

Affiliation: Retrovirus Research Laboratory, Institute of Comparative Medicine, Faculty of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow, G61 1QH, UK. b.willett@vet.gla.ac.uk

ABSTRACT
Feline immunodeficiency virus (FIV) targets helper T cells by attachment of the envelope glycoprotein (Env) to CD134, a subsequent interaction with CXCR4 then facilitating the process of viral entry. As the CXCR4 binding site is not exposed until CD134-binding has occurred then the virus is protected from neutralising antibodies targeting the CXCR4-binding site on Env. Prototypic FIV vaccines based on the FL4 strain of FIV contain a cell culture-adapted strain of FIV Petaluma, a CD134-independent strain of FIV that interacts directly with CXCR4. In addition to a characteristic increase in charge in the V3 loop homologue of FIVFL4, we identified two mutations in potential sites for N-linked glycosylation in the region of FIV Env analogous to the V1-V2 region of HIV and SIV Env, T271I and N342Y. When these mutations were introduced into the primary GL8 and CPG41 strains of FIV, the T271I mutation was found to alter the nature of the virus-CD134 interaction; primary viruses carrying the T271I mutation no longer required determinants in cysteine-rich domain (CRD) 2 of CD134 for viral entry. The T271I mutation did not confer CD134-independent infection upon GL8 or CPG41, nor did it increase the affinity of the CXCR4 interaction, suggesting that the principal effect was targeted at reducing the complexity of the Env-CD134 interaction.

Show MeSH
Related in: MedlinePlus