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The role of N-glycans of HIV-1 gp41 in virus infectivity and susceptibility to the suppressive effects of carbohydrate-binding agents.

Mathys L, Balzarini J - Retrovirology (2014)

Bottom Line: In accordance, we found that the gp120 levels in the envelope of N616Q mutant gp41 strains NL4.3, IIIB and HE were severely decreased.Single gp41 glycan deletions had no marked effects on CBA susceptibility, whereas some combinations of two to three gp41 glycan-deletions had a minor effect on CBA activity.In addition, we demonstrated that the deletion of up to three gp41 N-linked glycans only slightly affected CBA susceptibility.

View Article: PubMed Central - PubMed

Affiliation: Rega Institute for Medical Research, KU Leuven, Minderbroedersstraat 10, B-3000, Leuven, Belgium. leen.mathys@rega.kuleuven.be.

ABSTRACT

Background: Carbohydrate-binding agents (CBAs) are potent antiretroviral compounds that target the N-glycans on the HIV-1 envelope glycoproteins. The development of phenotypic resistance to CBAs by the virus is accompanied by the deletion of multiple N-linked glycans of the surface envelope glycoprotein gp120. Recently, also an N-glycan on the transmembrane envelope glycoprotein gp41 was shown to be deleted during CBA resistance development.

Results: We generated HIV-1 mutants lacking gp41 N-glycans and determined the influence of these glycan deletions on the viral phenotype (infectivity, CD4 binding, envelope glycoprotein incorporation in the viral particle and on the transfected cell, virus capture by DC-SIGN(+) cells and transmission of DC-SIGN-captured virions to CD4(+) T-lymphocytes) and on the phenotypic susceptibility of HIV-1 to a selection of CBAs. It was shown that some gp41 N-glycans are crucial for the infectivity of the virus. In particular, lack of an intact N616 glycosylation site was shown to result in the loss of viral infectivity of several (i.e. the X4-tropic IIIB and NL4.3 strains, and the X4/R5-tropic HE strain), but not all (i.e. the R5-tropic ADA strain) studied HIV-1 strains. In accordance, we found that the gp120 levels in the envelope of N616Q mutant gp41 strains NL4.3, IIIB and HE were severely decreased. In contrast, N616Q gp41 mutant HIV-1ADA contained gp120 levels similar to the gp120 levels in WT HIV-1ADA virus. Concomitantly deleting multiple gp41 N-glycans was often highly detrimental for viral infectivity. Using surface plasmon resonance technology we showed that CBAs have a pronounced affinity for both gp120 and gp41. However, the antiviral activity of CBAs is not dependent on the concomitant presence of all gp41 glycans. Single gp41 glycan deletions had no marked effects on CBA susceptibility, whereas some combinations of two to three gp41 glycan-deletions had a minor effect on CBA activity.

Conclusions: We revealed the importance of some gp41 N-linked glycans, in particular the N616 glycan which was shown to be absolutely indispensable for the infectivity potential of several virus strains. In addition, we demonstrated that the deletion of up to three gp41 N-linked glycans only slightly affected CBA susceptibility.

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Analysis of gp120 levels in the viral envelope of WT and mutant N616Q gp41 virus strains. Relative protein levels based on quantification of western blot data using the ImageJ software, and presented as normalized to p24 levels. Data are the means ± SD of 2 independent experiments.
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Fig11: Analysis of gp120 levels in the viral envelope of WT and mutant N616Q gp41 virus strains. Relative protein levels based on quantification of western blot data using the ImageJ software, and presented as normalized to p24 levels. Data are the means ± SD of 2 independent experiments.

Mentions: Based on the observation that HIV-1NL4.3 containing the gp41 N616Q glycan deletion had a severely decreased viral infectivity (Figures 2, 3, 9) due to significantly decreased levels of gp120 and gp41 in the viral envelope (Figure 5), we studied the gp120 levels in the other WT and N616Q mutant HIV-1 strains. As shown in Figure 11, severely decreased gp120 levels were found for mutant N616Q gp41 HIV-1 strains NL4.3, IIIB and HE. This is in agreement with the decreased viral infectivities observed for these mutant virus strains, as compared to their WT counterparts. In contrast, the N616Q gp41 mutant HIV-1ADA showed gp120 levels that were comparable to the levels observed in WT HIV-1ADA. This explains why the N616Q glycan deletion in gp41 of HIV-1ADA did not result in a loss of viral infectivity.Figure 11


The role of N-glycans of HIV-1 gp41 in virus infectivity and susceptibility to the suppressive effects of carbohydrate-binding agents.

Mathys L, Balzarini J - Retrovirology (2014)

Analysis of gp120 levels in the viral envelope of WT and mutant N616Q gp41 virus strains. Relative protein levels based on quantification of western blot data using the ImageJ software, and presented as normalized to p24 levels. Data are the means ± SD of 2 independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4269863&req=5

Fig11: Analysis of gp120 levels in the viral envelope of WT and mutant N616Q gp41 virus strains. Relative protein levels based on quantification of western blot data using the ImageJ software, and presented as normalized to p24 levels. Data are the means ± SD of 2 independent experiments.
Mentions: Based on the observation that HIV-1NL4.3 containing the gp41 N616Q glycan deletion had a severely decreased viral infectivity (Figures 2, 3, 9) due to significantly decreased levels of gp120 and gp41 in the viral envelope (Figure 5), we studied the gp120 levels in the other WT and N616Q mutant HIV-1 strains. As shown in Figure 11, severely decreased gp120 levels were found for mutant N616Q gp41 HIV-1 strains NL4.3, IIIB and HE. This is in agreement with the decreased viral infectivities observed for these mutant virus strains, as compared to their WT counterparts. In contrast, the N616Q gp41 mutant HIV-1ADA showed gp120 levels that were comparable to the levels observed in WT HIV-1ADA. This explains why the N616Q glycan deletion in gp41 of HIV-1ADA did not result in a loss of viral infectivity.Figure 11

Bottom Line: In accordance, we found that the gp120 levels in the envelope of N616Q mutant gp41 strains NL4.3, IIIB and HE were severely decreased.Single gp41 glycan deletions had no marked effects on CBA susceptibility, whereas some combinations of two to three gp41 glycan-deletions had a minor effect on CBA activity.In addition, we demonstrated that the deletion of up to three gp41 N-linked glycans only slightly affected CBA susceptibility.

View Article: PubMed Central - PubMed

Affiliation: Rega Institute for Medical Research, KU Leuven, Minderbroedersstraat 10, B-3000, Leuven, Belgium. leen.mathys@rega.kuleuven.be.

ABSTRACT

Background: Carbohydrate-binding agents (CBAs) are potent antiretroviral compounds that target the N-glycans on the HIV-1 envelope glycoproteins. The development of phenotypic resistance to CBAs by the virus is accompanied by the deletion of multiple N-linked glycans of the surface envelope glycoprotein gp120. Recently, also an N-glycan on the transmembrane envelope glycoprotein gp41 was shown to be deleted during CBA resistance development.

Results: We generated HIV-1 mutants lacking gp41 N-glycans and determined the influence of these glycan deletions on the viral phenotype (infectivity, CD4 binding, envelope glycoprotein incorporation in the viral particle and on the transfected cell, virus capture by DC-SIGN(+) cells and transmission of DC-SIGN-captured virions to CD4(+) T-lymphocytes) and on the phenotypic susceptibility of HIV-1 to a selection of CBAs. It was shown that some gp41 N-glycans are crucial for the infectivity of the virus. In particular, lack of an intact N616 glycosylation site was shown to result in the loss of viral infectivity of several (i.e. the X4-tropic IIIB and NL4.3 strains, and the X4/R5-tropic HE strain), but not all (i.e. the R5-tropic ADA strain) studied HIV-1 strains. In accordance, we found that the gp120 levels in the envelope of N616Q mutant gp41 strains NL4.3, IIIB and HE were severely decreased. In contrast, N616Q gp41 mutant HIV-1ADA contained gp120 levels similar to the gp120 levels in WT HIV-1ADA virus. Concomitantly deleting multiple gp41 N-glycans was often highly detrimental for viral infectivity. Using surface plasmon resonance technology we showed that CBAs have a pronounced affinity for both gp120 and gp41. However, the antiviral activity of CBAs is not dependent on the concomitant presence of all gp41 glycans. Single gp41 glycan deletions had no marked effects on CBA susceptibility, whereas some combinations of two to three gp41 glycan-deletions had a minor effect on CBA activity.

Conclusions: We revealed the importance of some gp41 N-linked glycans, in particular the N616 glycan which was shown to be absolutely indispensable for the infectivity potential of several virus strains. In addition, we demonstrated that the deletion of up to three gp41 N-linked glycans only slightly affected CBA susceptibility.

Show MeSH
Related in: MedlinePlus