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HIV-1 Group P is unable to antagonize human tetherin by Vpu, Env or Nef.

Sauter D, Hué S, Petit SJ, Plantier JC, Towers GJ, Kirchhoff F, Gupta RK - Retrovirology (2011)

Bottom Line: Vpu, Env and Nef proteins from both Group P viruses failed to counteract human or gorilla tetherin to promote efficient release of HIV-1 virions, although both Group P Nef proteins moderately downmodulated gorilla tetherin from the cell surface.Notably, Vpu, Env and Nef alleles from the two HIV-1 P strains were all able to reduce CD4 cell surface expression.The inability to antagonize human tetherin may potentially explain the limited spread of HIV-1 Group P in the human population.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Molecular Virology, Ulm University Medical Center, 89069, Ulm, Germany.

ABSTRACT

Background: A new subgroup of HIV-1, designated Group P, was recently detected in two unrelated patients of Cameroonian origin. HIV-1 Group P phylogenetically clusters with SIVgor suggesting that it is the result of a cross-species transmission from gorillas. Until today, HIV-1 Group P has only been detected in two patients, and its degree of adaptation to the human host is largely unknown. Previous data have shown that pandemic HIV-1 Group M, but not non-pandemic Group O or rare Group N viruses, efficiently antagonize the human orthologue of the restriction factor tetherin (BST-2, HM1.24, CD317) suggesting that primate lentiviruses may have to gain anti-tetherin activity for efficient spread in the human population. Thus far, three SIV/HIV gene products (vpu, nef and env) are known to have the potential to counteract primate tetherin proteins, often in a species-specific manner. Here, we examined how long Group P may have been circulating in humans and determined its capability to antagonize human tetherin as an indicator of adaptation to humans.

Results: Our data suggest that HIV-1 Group P entered the human population between 1845 and 1989. Vpu, Env and Nef proteins from both Group P viruses failed to counteract human or gorilla tetherin to promote efficient release of HIV-1 virions, although both Group P Nef proteins moderately downmodulated gorilla tetherin from the cell surface. Notably, Vpu, Env and Nef alleles from the two HIV-1 P strains were all able to reduce CD4 cell surface expression.

Conclusions: Our analyses of the two reported HIV-1 Group P viruses suggest that zoonosis occurred in the last 170 years and further support that pandemic HIV-1 Group M strains are better adapted to humans than non-pandemic or rare Group O, N and P viruses. The inability to antagonize human tetherin may potentially explain the limited spread of HIV-1 Group P in the human population.

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Tetherin Counteraction by HIV-1 Group P Vpu and Nef. (A) FACS analysis of 293T cells cotransfected with a human or gorilla tetherin expression vector and pCGCG plasmids expressing GFP alone (GFP only) or together with the indicated vpu or nef alleles. (B) Reduction of Vpu- and Nef-mediated tetherin expression in 293T cells. Shown is the n-fold reduction of tetherin cell surface expression levels relative to those measured in cells transfected with the eGFP only control vector. The range of GFP expression used for the calculation is indicated in panel A. The mean (± SD) of two independent experiments is shown. (C) Western blot analysis of cell and virion lysates following cotransfection of 293T cells with a vpu- and nef-defective proviral HIV-1 NL4-3 construct, pCGCG plasmids expressing eGFP alone (eGFP only) or together with the indicated vpu or nef alleles and an empty vector (no tetherin) or human or gorilla tetherin expression plasmids. Cell and virion lysates were probed with an anti-HIV-1 capsid p24 monoclonal antibody. Sup., cell culture supernatant. (D) Infectious virus and (E) p24 release from 293T cells following cotransfection with a vpu- and nef-defective proviral HIV-1 NL4-3 construct, pCGCG plasmids expressing eGFP alone (eGFP only) or together with the indicated vpu or nef alleles and different amounts of human or gorilla tetherin expression plasmids. Infectious virus was determined by infection of TZM-bl reporter cells and p24 release was quantified by ELISA. Values are shown as percentage of values obtained in the absence of tetherin. All infections were performed in triplicates. The mean of two independent experiments is shown.
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Figure 3: Tetherin Counteraction by HIV-1 Group P Vpu and Nef. (A) FACS analysis of 293T cells cotransfected with a human or gorilla tetherin expression vector and pCGCG plasmids expressing GFP alone (GFP only) or together with the indicated vpu or nef alleles. (B) Reduction of Vpu- and Nef-mediated tetherin expression in 293T cells. Shown is the n-fold reduction of tetherin cell surface expression levels relative to those measured in cells transfected with the eGFP only control vector. The range of GFP expression used for the calculation is indicated in panel A. The mean (± SD) of two independent experiments is shown. (C) Western blot analysis of cell and virion lysates following cotransfection of 293T cells with a vpu- and nef-defective proviral HIV-1 NL4-3 construct, pCGCG plasmids expressing eGFP alone (eGFP only) or together with the indicated vpu or nef alleles and an empty vector (no tetherin) or human or gorilla tetherin expression plasmids. Cell and virion lysates were probed with an anti-HIV-1 capsid p24 monoclonal antibody. Sup., cell culture supernatant. (D) Infectious virus and (E) p24 release from 293T cells following cotransfection with a vpu- and nef-defective proviral HIV-1 NL4-3 construct, pCGCG plasmids expressing eGFP alone (eGFP only) or together with the indicated vpu or nef alleles and different amounts of human or gorilla tetherin expression plasmids. Infectious virus was determined by infection of TZM-bl reporter cells and p24 release was quantified by ELISA. Values are shown as percentage of values obtained in the absence of tetherin. All infections were performed in triplicates. The mean of two independent experiments is shown.

Mentions: We next tested the activity of Group P Vpu and Nef proteins against human and gorilla tetherin. To this end, we determined the levels of tetherin surface expression and infectious virus yields from HEK 293T cells cotransfected with a vpu/nef-deleted (ΔvpuΔnef) HIV-1 Group M NL4-3 proviral construct [33], a tetherin expression plasmid, and a vector expressing Vpu or Nef [17]. As expected, HIV-1 Group M Vpus downregulated human tetherin about 5- to 6-fold (Figure 3A, B). In contrast, both HIV-1 Group P vpu alleles did not reduce tetherin cell surface expression (Figure 3B). This is not surprising since HIV-1 Group P Vpus lack the AxxxAxxxW transmembrane motif known to be critical for tetherin antagonism by HIV-1 Group M Vpus and may thus not interact with this restriction factor [34] (Additional file 1). Expression of HIV-1 P RBF168 and 06CMU14788 Nef did not affect surface expression of human tetherin either, but slightly decreased gorilla tetherin surface expression by 1.5- to 2.5-fold (Figure 3B). Unlike the SIVgor Nef, however, both HIV-1 Group P Nef proteins were unable to increase virion release in the presence of gorilla tetherin (Figure 3C-E and Additional file 2). This observation is consistent with reports that Vpu-mediated downmodulation of tetherin and viral release may be separable activities [35,36], although a similar finding has not yet been reported for Nef. Importantly, neither HIV-1 Group P Vpu nor Nef proteins were able to increase infectious virion or p24 release in the presence of human tetherin (Figure 3C-E and S2). This lack of anti-tetherin activity of Nef and Vpu shows that Group P viruses are not yet optimally adapted to the human host.


HIV-1 Group P is unable to antagonize human tetherin by Vpu, Env or Nef.

Sauter D, Hué S, Petit SJ, Plantier JC, Towers GJ, Kirchhoff F, Gupta RK - Retrovirology (2011)

Tetherin Counteraction by HIV-1 Group P Vpu and Nef. (A) FACS analysis of 293T cells cotransfected with a human or gorilla tetherin expression vector and pCGCG plasmids expressing GFP alone (GFP only) or together with the indicated vpu or nef alleles. (B) Reduction of Vpu- and Nef-mediated tetherin expression in 293T cells. Shown is the n-fold reduction of tetherin cell surface expression levels relative to those measured in cells transfected with the eGFP only control vector. The range of GFP expression used for the calculation is indicated in panel A. The mean (± SD) of two independent experiments is shown. (C) Western blot analysis of cell and virion lysates following cotransfection of 293T cells with a vpu- and nef-defective proviral HIV-1 NL4-3 construct, pCGCG plasmids expressing eGFP alone (eGFP only) or together with the indicated vpu or nef alleles and an empty vector (no tetherin) or human or gorilla tetherin expression plasmids. Cell and virion lysates were probed with an anti-HIV-1 capsid p24 monoclonal antibody. Sup., cell culture supernatant. (D) Infectious virus and (E) p24 release from 293T cells following cotransfection with a vpu- and nef-defective proviral HIV-1 NL4-3 construct, pCGCG plasmids expressing eGFP alone (eGFP only) or together with the indicated vpu or nef alleles and different amounts of human or gorilla tetherin expression plasmids. Infectious virus was determined by infection of TZM-bl reporter cells and p24 release was quantified by ELISA. Values are shown as percentage of values obtained in the absence of tetherin. All infections were performed in triplicates. The mean of two independent experiments is shown.
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Related In: Results  -  Collection

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Figure 3: Tetherin Counteraction by HIV-1 Group P Vpu and Nef. (A) FACS analysis of 293T cells cotransfected with a human or gorilla tetherin expression vector and pCGCG plasmids expressing GFP alone (GFP only) or together with the indicated vpu or nef alleles. (B) Reduction of Vpu- and Nef-mediated tetherin expression in 293T cells. Shown is the n-fold reduction of tetherin cell surface expression levels relative to those measured in cells transfected with the eGFP only control vector. The range of GFP expression used for the calculation is indicated in panel A. The mean (± SD) of two independent experiments is shown. (C) Western blot analysis of cell and virion lysates following cotransfection of 293T cells with a vpu- and nef-defective proviral HIV-1 NL4-3 construct, pCGCG plasmids expressing eGFP alone (eGFP only) or together with the indicated vpu or nef alleles and an empty vector (no tetherin) or human or gorilla tetherin expression plasmids. Cell and virion lysates were probed with an anti-HIV-1 capsid p24 monoclonal antibody. Sup., cell culture supernatant. (D) Infectious virus and (E) p24 release from 293T cells following cotransfection with a vpu- and nef-defective proviral HIV-1 NL4-3 construct, pCGCG plasmids expressing eGFP alone (eGFP only) or together with the indicated vpu or nef alleles and different amounts of human or gorilla tetherin expression plasmids. Infectious virus was determined by infection of TZM-bl reporter cells and p24 release was quantified by ELISA. Values are shown as percentage of values obtained in the absence of tetherin. All infections were performed in triplicates. The mean of two independent experiments is shown.
Mentions: We next tested the activity of Group P Vpu and Nef proteins against human and gorilla tetherin. To this end, we determined the levels of tetherin surface expression and infectious virus yields from HEK 293T cells cotransfected with a vpu/nef-deleted (ΔvpuΔnef) HIV-1 Group M NL4-3 proviral construct [33], a tetherin expression plasmid, and a vector expressing Vpu or Nef [17]. As expected, HIV-1 Group M Vpus downregulated human tetherin about 5- to 6-fold (Figure 3A, B). In contrast, both HIV-1 Group P vpu alleles did not reduce tetherin cell surface expression (Figure 3B). This is not surprising since HIV-1 Group P Vpus lack the AxxxAxxxW transmembrane motif known to be critical for tetherin antagonism by HIV-1 Group M Vpus and may thus not interact with this restriction factor [34] (Additional file 1). Expression of HIV-1 P RBF168 and 06CMU14788 Nef did not affect surface expression of human tetherin either, but slightly decreased gorilla tetherin surface expression by 1.5- to 2.5-fold (Figure 3B). Unlike the SIVgor Nef, however, both HIV-1 Group P Nef proteins were unable to increase virion release in the presence of gorilla tetherin (Figure 3C-E and Additional file 2). This observation is consistent with reports that Vpu-mediated downmodulation of tetherin and viral release may be separable activities [35,36], although a similar finding has not yet been reported for Nef. Importantly, neither HIV-1 Group P Vpu nor Nef proteins were able to increase infectious virion or p24 release in the presence of human tetherin (Figure 3C-E and S2). This lack of anti-tetherin activity of Nef and Vpu shows that Group P viruses are not yet optimally adapted to the human host.

Bottom Line: Vpu, Env and Nef proteins from both Group P viruses failed to counteract human or gorilla tetherin to promote efficient release of HIV-1 virions, although both Group P Nef proteins moderately downmodulated gorilla tetherin from the cell surface.Notably, Vpu, Env and Nef alleles from the two HIV-1 P strains were all able to reduce CD4 cell surface expression.The inability to antagonize human tetherin may potentially explain the limited spread of HIV-1 Group P in the human population.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Molecular Virology, Ulm University Medical Center, 89069, Ulm, Germany.

ABSTRACT

Background: A new subgroup of HIV-1, designated Group P, was recently detected in two unrelated patients of Cameroonian origin. HIV-1 Group P phylogenetically clusters with SIVgor suggesting that it is the result of a cross-species transmission from gorillas. Until today, HIV-1 Group P has only been detected in two patients, and its degree of adaptation to the human host is largely unknown. Previous data have shown that pandemic HIV-1 Group M, but not non-pandemic Group O or rare Group N viruses, efficiently antagonize the human orthologue of the restriction factor tetherin (BST-2, HM1.24, CD317) suggesting that primate lentiviruses may have to gain anti-tetherin activity for efficient spread in the human population. Thus far, three SIV/HIV gene products (vpu, nef and env) are known to have the potential to counteract primate tetherin proteins, often in a species-specific manner. Here, we examined how long Group P may have been circulating in humans and determined its capability to antagonize human tetherin as an indicator of adaptation to humans.

Results: Our data suggest that HIV-1 Group P entered the human population between 1845 and 1989. Vpu, Env and Nef proteins from both Group P viruses failed to counteract human or gorilla tetherin to promote efficient release of HIV-1 virions, although both Group P Nef proteins moderately downmodulated gorilla tetherin from the cell surface. Notably, Vpu, Env and Nef alleles from the two HIV-1 P strains were all able to reduce CD4 cell surface expression.

Conclusions: Our analyses of the two reported HIV-1 Group P viruses suggest that zoonosis occurred in the last 170 years and further support that pandemic HIV-1 Group M strains are better adapted to humans than non-pandemic or rare Group O, N and P viruses. The inability to antagonize human tetherin may potentially explain the limited spread of HIV-1 Group P in the human population.

Show MeSH
Related in: MedlinePlus