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Longitudinal Sequence and Functional Evolution within Glycoprotein E2 in Hepatitis C Virus Genotype 3a Infection.

Alhammad YM, Maharajh S, Butcher R, Eden JS, White PA, Poumbourios P, Drummer HE - PLoS ONE (2015)

Bottom Line: In the second patient, the ability of the week 36 RBD, just prior to viral clearance, to bind CD81 was reduced ~50% relative to RBD sequences obtained earlier.The binding of a NAb specific to a conserved epitope located within E2 residues 411-428 was significantly reduced by week 108 despite complete conservation of its epitope suggesting that E2 antigenicity is allosterically modulated.By contrast, the exposure of non-neutralizing epitopes was reduced in the patient that cleared his/her infection and could in part be attributed to sequence changes in the igVR.

View Article: PubMed Central - PubMed

Affiliation: Centre for Biomedical Research, Burnet Institute, 85 Commercial Rd, Melbourne, 3004, Australia; Department of Microbiology, Monash University, Clayton, Victoria, Australia.

ABSTRACT
The E2 glycoprotein of Hepatitis C virus (HCV) is a major target of the neutralizing antibody (NAb) response with the majority of epitopes located within its receptor binding domain (RBD; 384-661). Within E2 are three variable regions located at the N-terminus (HVR1; 384-411), and internally at 460-480 (HVR2) and 570-580 [intergenotypic variable region (igVR)], all of which lie outside a conserved core domain that contains the CD81 binding site, essential for attachment of virions to host cells and a major target of NAbs. In this study, we examined the evolution of the E1 and E2 region in two patients infected with genotype 3a virus. Whereas one patient was able to clear the acute infection, the other developed a chronic infection. Mutations accumulated at multiple positions within the N-terminal HVR1 as well as within the igVR in both patients over time, whereas mutations in HVR2 were observed only in the chronically infected patient. Mutations within or adjacent to the CD81 contact site were observed in both patients but were less frequent and more conservative in the patient that cleared his/her infection. The evolution of CD81 binding function and antigenicity was examined with longitudinal E2 RBD sequences. The ability of the RBD to bind CD81 was completely lost by week 108 in the patient that developed chronic HCV. In the second patient, the ability of the week 36 RBD, just prior to viral clearance, to bind CD81 was reduced ~50% relative to RBD sequences obtained earlier. The binding of a NAb specific to a conserved epitope located within E2 residues 411-428 was significantly reduced by week 108 despite complete conservation of its epitope suggesting that E2 antigenicity is allosterically modulated. The exposure of non-neutralizing antibody epitopes was similarly explored and we observed that the epitope of 3 out of 4 non-NAbs were significantly more exposed in the RBDs representing the late timepoints in the chronic patient. By contrast, the exposure of non-neutralizing epitopes was reduced in the patient that cleared his/her infection and could in part be attributed to sequence changes in the igVR. These studies reveal that during HCV infection, the exposure of the CD81 binding site on E2 becomes increasingly occluded, and the antigenicity of the E2 RBD towards both neutralizing and non-neutralizing antibodies is modulated via allosteric mechanisms.

No MeSH data available.


Related in: MedlinePlus

Amino acid changes within the E2 RBD from longitudinal samples of chronic and cleared patients.Samples of HCV infected patients were obtained from the Australian Trial in Acute Hepatitis C (ATAHC) prospective study. cDNA of the HCV E1E2 region was recovered from each timepoint of two patients (A) and (B). At least twenty clones were isolated from five and three timepoints of patients A and B, respectively. Sequences of each timepoint were aligned and amino acid differences within HVR1, HVR2, igVR, and epitopes I, II and III were marked with reference to the earliest timepoint available for each patient. Residue numbering is according to the H77c prototype sequence. SC = screening, BL = baseline.
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pone.0126397.g001: Amino acid changes within the E2 RBD from longitudinal samples of chronic and cleared patients.Samples of HCV infected patients were obtained from the Australian Trial in Acute Hepatitis C (ATAHC) prospective study. cDNA of the HCV E1E2 region was recovered from each timepoint of two patients (A) and (B). At least twenty clones were isolated from five and three timepoints of patients A and B, respectively. Sequences of each timepoint were aligned and amino acid differences within HVR1, HVR2, igVR, and epitopes I, II and III were marked with reference to the earliest timepoint available for each patient. Residue numbering is according to the H77c prototype sequence. SC = screening, BL = baseline.

Mentions: Two individuals from the ATAHC cohort were selected for analysis in this study. One patient developed chronic HCV (patient A) while the other cleared his/her HCV infection after week 36 (patient B). Mutations in the E1E2 region amplified from longitudinal samples that resulted in amino acid changes deviating from the E1E2 sequence obtained at the earliest available time point are summarised in Fig 1 with full sequences of the E2 RBD region provided in S1 and S2 Figs. The overall dN/dS ratios in the E1E2 region for patient A and patient B were similar, 0.74 and 0.76, respectively. However, at individual sites within this region, stronger evidence of viral adaptation was apparent in patient A (S4 Table).


Longitudinal Sequence and Functional Evolution within Glycoprotein E2 in Hepatitis C Virus Genotype 3a Infection.

Alhammad YM, Maharajh S, Butcher R, Eden JS, White PA, Poumbourios P, Drummer HE - PLoS ONE (2015)

Amino acid changes within the E2 RBD from longitudinal samples of chronic and cleared patients.Samples of HCV infected patients were obtained from the Australian Trial in Acute Hepatitis C (ATAHC) prospective study. cDNA of the HCV E1E2 region was recovered from each timepoint of two patients (A) and (B). At least twenty clones were isolated from five and three timepoints of patients A and B, respectively. Sequences of each timepoint were aligned and amino acid differences within HVR1, HVR2, igVR, and epitopes I, II and III were marked with reference to the earliest timepoint available for each patient. Residue numbering is according to the H77c prototype sequence. SC = screening, BL = baseline.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4430534&req=5

pone.0126397.g001: Amino acid changes within the E2 RBD from longitudinal samples of chronic and cleared patients.Samples of HCV infected patients were obtained from the Australian Trial in Acute Hepatitis C (ATAHC) prospective study. cDNA of the HCV E1E2 region was recovered from each timepoint of two patients (A) and (B). At least twenty clones were isolated from five and three timepoints of patients A and B, respectively. Sequences of each timepoint were aligned and amino acid differences within HVR1, HVR2, igVR, and epitopes I, II and III were marked with reference to the earliest timepoint available for each patient. Residue numbering is according to the H77c prototype sequence. SC = screening, BL = baseline.
Mentions: Two individuals from the ATAHC cohort were selected for analysis in this study. One patient developed chronic HCV (patient A) while the other cleared his/her HCV infection after week 36 (patient B). Mutations in the E1E2 region amplified from longitudinal samples that resulted in amino acid changes deviating from the E1E2 sequence obtained at the earliest available time point are summarised in Fig 1 with full sequences of the E2 RBD region provided in S1 and S2 Figs. The overall dN/dS ratios in the E1E2 region for patient A and patient B were similar, 0.74 and 0.76, respectively. However, at individual sites within this region, stronger evidence of viral adaptation was apparent in patient A (S4 Table).

Bottom Line: In the second patient, the ability of the week 36 RBD, just prior to viral clearance, to bind CD81 was reduced ~50% relative to RBD sequences obtained earlier.The binding of a NAb specific to a conserved epitope located within E2 residues 411-428 was significantly reduced by week 108 despite complete conservation of its epitope suggesting that E2 antigenicity is allosterically modulated.By contrast, the exposure of non-neutralizing epitopes was reduced in the patient that cleared his/her infection and could in part be attributed to sequence changes in the igVR.

View Article: PubMed Central - PubMed

Affiliation: Centre for Biomedical Research, Burnet Institute, 85 Commercial Rd, Melbourne, 3004, Australia; Department of Microbiology, Monash University, Clayton, Victoria, Australia.

ABSTRACT
The E2 glycoprotein of Hepatitis C virus (HCV) is a major target of the neutralizing antibody (NAb) response with the majority of epitopes located within its receptor binding domain (RBD; 384-661). Within E2 are three variable regions located at the N-terminus (HVR1; 384-411), and internally at 460-480 (HVR2) and 570-580 [intergenotypic variable region (igVR)], all of which lie outside a conserved core domain that contains the CD81 binding site, essential for attachment of virions to host cells and a major target of NAbs. In this study, we examined the evolution of the E1 and E2 region in two patients infected with genotype 3a virus. Whereas one patient was able to clear the acute infection, the other developed a chronic infection. Mutations accumulated at multiple positions within the N-terminal HVR1 as well as within the igVR in both patients over time, whereas mutations in HVR2 were observed only in the chronically infected patient. Mutations within or adjacent to the CD81 contact site were observed in both patients but were less frequent and more conservative in the patient that cleared his/her infection. The evolution of CD81 binding function and antigenicity was examined with longitudinal E2 RBD sequences. The ability of the RBD to bind CD81 was completely lost by week 108 in the patient that developed chronic HCV. In the second patient, the ability of the week 36 RBD, just prior to viral clearance, to bind CD81 was reduced ~50% relative to RBD sequences obtained earlier. The binding of a NAb specific to a conserved epitope located within E2 residues 411-428 was significantly reduced by week 108 despite complete conservation of its epitope suggesting that E2 antigenicity is allosterically modulated. The exposure of non-neutralizing antibody epitopes was similarly explored and we observed that the epitope of 3 out of 4 non-NAbs were significantly more exposed in the RBDs representing the late timepoints in the chronic patient. By contrast, the exposure of non-neutralizing epitopes was reduced in the patient that cleared his/her infection and could in part be attributed to sequence changes in the igVR. These studies reveal that during HCV infection, the exposure of the CD81 binding site on E2 becomes increasingly occluded, and the antigenicity of the E2 RBD towards both neutralizing and non-neutralizing antibodies is modulated via allosteric mechanisms.

No MeSH data available.


Related in: MedlinePlus