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Viremic long-term nonprogressive HIV-1 infection is not associated with abnormalities in known Nef functions.

Heigele A, Camerini D, van't Wout AB, Kirchhoff F - Retrovirology (2014)

Bottom Line: Finally, we found that VNP-Nefs increased virion infectivity and enhanced HIV-1 replication and cytopathicity in primary human cells and in ex vivo infected lymphoid tissues.Our results show that nef alleles from VNPs and progressors of HIV-1 infection show only modest differences in established functions.Thus, the lack of chronic immune activation and disease progression in HIV-1-infected VNPs is apparently not associated with unusual functional properties of the accessory viral Nef protein.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Molecular Virology, Ulm University Medical Center, Ulm, Germany. frank.kirchhoff@uni-ulm.de.

ABSTRACT

Background: A small minority of HIV-1-infected individuals show low levels of immune activation and do not develop immunodeficiency despite high viral loads. Since the accessory viral Nef protein modulates T cell activation and plays a key role in the pathogenesis of AIDS, we investigated whether specific properties of Nef may be associated with this highly unusual clinical outcome of HIV-1 infection.

Findings: Comprehensive functional analyses of sequential HIV-1 strains from three viremic long-term non-progressors (VNP) showed that they encode full-length Nef proteins that are capable of modulating CD4, CD28, CD8ß, MHC-I and CD74 cell surface expression. Similar to Nef proteins from HIV-1-infected individuals with progressive infection (P-Nefs) and unlike Nefs from simian immunodeficiency viruses (SIVs) that do not cause chronic immune activation and disease in their natural simian hosts, VNP-Nefs were generally unable to down-modulate TCR-CD3 cell surface expression to block T cell activation and apoptosis. On average, VNP-Nefs suppressed NF-AT activation less effectively than P-Nefs and were slightly less active in enhancing NF-κB activity. Finally, we found that VNP-Nefs increased virion infectivity and enhanced HIV-1 replication and cytopathicity in primary human cells and in ex vivo infected lymphoid tissues.

Conclusions: Our results show that nef alleles from VNPs and progressors of HIV-1 infection show only modest differences in established functions. Thus, the lack of chronic immune activation and disease progression in HIV-1-infected VNPs is apparently not associated with unusual functional properties of the accessory viral Nef protein.

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Amino acid alignment of VNP- and P-Nef proteins. Nef alleles from VNPs and Ps are compared. Some conserved sequence elements in Nef, including the N-terminal myristoylation signal, the M20 and WL residues (involved in MHC-I or CD4 down-modulation, respectively), the acidic, proline-rich and diarginine motifs, a thioesterase binding site, a C-proximal adaptor-protein (AP) interaction site and a diacidic putative V1H binding site are indicated. Residues 22 and 62 are highlighted yellow. Dots specify identity with the NL4-3 Nef sequence; dashes indicate gaps introduced to optimize the alignment.
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Figure 1: Amino acid alignment of VNP- and P-Nef proteins. Nef alleles from VNPs and Ps are compared. Some conserved sequence elements in Nef, including the N-terminal myristoylation signal, the M20 and WL residues (involved in MHC-I or CD4 down-modulation, respectively), the acidic, proline-rich and diarginine motifs, a thioesterase binding site, a C-proximal adaptor-protein (AP) interaction site and a diacidic putative V1H binding site are indicated. Residues 22 and 62 are highlighted yellow. Dots specify identity with the NL4-3 Nef sequence; dashes indicate gaps introduced to optimize the alignment.

Mentions: To examine their functional properties, we PCR-amplified nef genes from three previously described HIV-1-infected VNPs from the Amsterdam Cohort Studies on HIV infection and AIDS[3] obtained after six to 14 years of documented HIV-1 infection. For comparison, we utilized nef alleles amplified from plasma samples obtained from eight individuals with progressing HIV-1 infection (P) and seven previously characterized HIV-1, HIV-2, SIVmac and SIVsmm nef alleles (Additional file1: Table S1). It has previously been shown that SIV Nefs modulate various receptors and enhance viral infectivity and replication in a species-independent manner[10,14]. Between four and ten nef alleles were sequenced per VNP and P sample and those predicting amino acid sequences that were identical or almost identical to the respective patient and time point-specific consensus sequence and thus most representative were selected for further analysis (Figure 1). All nef alleles encoded and expressed full-length proteins (Additional file1: Figures S1) and previously defined functional domains were conserved (Figure 1), suggesting that Nef proteins from both groups of HIV-1-infected individuals are functionally active. No specific sequence signatures were observed in VNP-Nefs, although they frequently contained 22Q (9/11) and 62T (9/11), whereas those from progressing individuals contained 22R (5/8) and 62A (6/8; numbers indicate positions in the Nef alignment shown in Figure 1). Given the different cohorts from which the VNP and P samples originated, these are likely to be differences in founder sequences.


Viremic long-term nonprogressive HIV-1 infection is not associated with abnormalities in known Nef functions.

Heigele A, Camerini D, van't Wout AB, Kirchhoff F - Retrovirology (2014)

Amino acid alignment of VNP- and P-Nef proteins. Nef alleles from VNPs and Ps are compared. Some conserved sequence elements in Nef, including the N-terminal myristoylation signal, the M20 and WL residues (involved in MHC-I or CD4 down-modulation, respectively), the acidic, proline-rich and diarginine motifs, a thioesterase binding site, a C-proximal adaptor-protein (AP) interaction site and a diacidic putative V1H binding site are indicated. Residues 22 and 62 are highlighted yellow. Dots specify identity with the NL4-3 Nef sequence; dashes indicate gaps introduced to optimize the alignment.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3927655&req=5

Figure 1: Amino acid alignment of VNP- and P-Nef proteins. Nef alleles from VNPs and Ps are compared. Some conserved sequence elements in Nef, including the N-terminal myristoylation signal, the M20 and WL residues (involved in MHC-I or CD4 down-modulation, respectively), the acidic, proline-rich and diarginine motifs, a thioesterase binding site, a C-proximal adaptor-protein (AP) interaction site and a diacidic putative V1H binding site are indicated. Residues 22 and 62 are highlighted yellow. Dots specify identity with the NL4-3 Nef sequence; dashes indicate gaps introduced to optimize the alignment.
Mentions: To examine their functional properties, we PCR-amplified nef genes from three previously described HIV-1-infected VNPs from the Amsterdam Cohort Studies on HIV infection and AIDS[3] obtained after six to 14 years of documented HIV-1 infection. For comparison, we utilized nef alleles amplified from plasma samples obtained from eight individuals with progressing HIV-1 infection (P) and seven previously characterized HIV-1, HIV-2, SIVmac and SIVsmm nef alleles (Additional file1: Table S1). It has previously been shown that SIV Nefs modulate various receptors and enhance viral infectivity and replication in a species-independent manner[10,14]. Between four and ten nef alleles were sequenced per VNP and P sample and those predicting amino acid sequences that were identical or almost identical to the respective patient and time point-specific consensus sequence and thus most representative were selected for further analysis (Figure 1). All nef alleles encoded and expressed full-length proteins (Additional file1: Figures S1) and previously defined functional domains were conserved (Figure 1), suggesting that Nef proteins from both groups of HIV-1-infected individuals are functionally active. No specific sequence signatures were observed in VNP-Nefs, although they frequently contained 22Q (9/11) and 62T (9/11), whereas those from progressing individuals contained 22R (5/8) and 62A (6/8; numbers indicate positions in the Nef alignment shown in Figure 1). Given the different cohorts from which the VNP and P samples originated, these are likely to be differences in founder sequences.

Bottom Line: Finally, we found that VNP-Nefs increased virion infectivity and enhanced HIV-1 replication and cytopathicity in primary human cells and in ex vivo infected lymphoid tissues.Our results show that nef alleles from VNPs and progressors of HIV-1 infection show only modest differences in established functions.Thus, the lack of chronic immune activation and disease progression in HIV-1-infected VNPs is apparently not associated with unusual functional properties of the accessory viral Nef protein.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Molecular Virology, Ulm University Medical Center, Ulm, Germany. frank.kirchhoff@uni-ulm.de.

ABSTRACT

Background: A small minority of HIV-1-infected individuals show low levels of immune activation and do not develop immunodeficiency despite high viral loads. Since the accessory viral Nef protein modulates T cell activation and plays a key role in the pathogenesis of AIDS, we investigated whether specific properties of Nef may be associated with this highly unusual clinical outcome of HIV-1 infection.

Findings: Comprehensive functional analyses of sequential HIV-1 strains from three viremic long-term non-progressors (VNP) showed that they encode full-length Nef proteins that are capable of modulating CD4, CD28, CD8ß, MHC-I and CD74 cell surface expression. Similar to Nef proteins from HIV-1-infected individuals with progressive infection (P-Nefs) and unlike Nefs from simian immunodeficiency viruses (SIVs) that do not cause chronic immune activation and disease in their natural simian hosts, VNP-Nefs were generally unable to down-modulate TCR-CD3 cell surface expression to block T cell activation and apoptosis. On average, VNP-Nefs suppressed NF-AT activation less effectively than P-Nefs and were slightly less active in enhancing NF-κB activity. Finally, we found that VNP-Nefs increased virion infectivity and enhanced HIV-1 replication and cytopathicity in primary human cells and in ex vivo infected lymphoid tissues.

Conclusions: Our results show that nef alleles from VNPs and progressors of HIV-1 infection show only modest differences in established functions. Thus, the lack of chronic immune activation and disease progression in HIV-1-infected VNPs is apparently not associated with unusual functional properties of the accessory viral Nef protein.

Show MeSH
Related in: MedlinePlus