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Association of VH4-59 Antibody Variable Gene Usage with Recognition of an Immunodominant Epitope on the HIV-1 Gag Protein.

Chukwuma VU, Hicar MD, Chen X, Nicholas KJ, Joyner A, Kalams SA, Landucci G, Forthal DN, Spearman PW, Crowe JE - PLoS ONE (2015)

Bottom Line: We found no evidence that mAb 3E4 exhibited any function in laboratory studies aimed at elucidating the immunologic activity, including assays for neutralization, Ab-dependent cell-mediated virus inhibition, or enhanced T cell reactivity caused by Gag-3E4 complexes.The findings suggest this immunodominant epitope in Gag protein, which is associated with VH4-59 germline gene usage, may induce a high level of B cells that encode binding but non-functional antibodies that occupy significant repertoire space following HIV infection.The studies define an additional specific molecular mechanism in the immune distraction activity of the HIV virion.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, Tennessee, United States of America.

ABSTRACT
The human antibody response against HIV-1 infection recognizes diverse antigenic subunits of the virion, and includes a high level of antibodies to the Gag protein. We report here the isolation and characterization of a subset of Gag-specific human monoclonal antibodies (mAbs) that were prevalent in the antibody repertoire of an HIV-infected individual. Several lineages of Gag-specifc mAbs were encoded by a single antibody heavy chain variable region, VH4-59, and a representative antibody from this group designated mAb 3E4 recognized a linear epitope on the globular head of the p17 subunit of Gag. We found no evidence that mAb 3E4 exhibited any function in laboratory studies aimed at elucidating the immunologic activity, including assays for neutralization, Ab-dependent cell-mediated virus inhibition, or enhanced T cell reactivity caused by Gag-3E4 complexes. The findings suggest this immunodominant epitope in Gag protein, which is associated with VH4-59 germline gene usage, may induce a high level of B cells that encode binding but non-functional antibodies that occupy significant repertoire space following HIV infection. The studies define an additional specific molecular mechanism in the immune distraction activity of the HIV virion.

No MeSH data available.


Related in: MedlinePlus

Binding of VH4-59 encoded antibodies to HIV antigens.Binding of mAb b12 or VH4-59 gene-encoded mAbs at a concentration of 1 μg/mL to Env VLP (black), Gag-only VLP (grey), BaL gp120 (white), or YU2 gp140 (pattern) tested by ELISA.
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pone.0133509.g002: Binding of VH4-59 encoded antibodies to HIV antigens.Binding of mAb b12 or VH4-59 gene-encoded mAbs at a concentration of 1 μg/mL to Env VLP (black), Gag-only VLP (grey), BaL gp120 (white), or YU2 gp140 (pattern) tested by ELISA.

Mentions: To characterize the binding phenotype of these VH4-59 gene-encoded mAbs, we synthesized genes encoding these mAbs as cDNAs optimized for expression in mammalian cells and expressed recombinant IgGs in 293F cells. The purified IgGs were examined for binding to VLPs displaying envelope (Env-VLP), VLPs lacking Env (Gag-only VLPs), or purified gp120 from the BaL strain (BaL gp120). The most remarkable finding noted was the binding of mAb 3E4 to both Env-VLP and Gag-only VLP, with no binding observed to BaL gp120 protein. This finding showed that mAb 3E4 binding to the VLPs was not Env-specific. As expected, the previously described Env protein CD4-binding site-specific mAb b12 bound to Env-VLP and BaL gp120, but not to Gag-only VLPs. To determine whether this Gag-only VLP binding phenotype was prevalent among five other VH4-59 encoded mAbs, we tested binding to Env-VLP, Gag-only VLP, BaL gp120, or YU2 gp140. All the VH4-59 gene-encoded mAbs tested showed binding to the VLPs independent of Env, but binding was not observed to purified Env proteins in monomeric or trimeric forms (Fig 2). The binding to Gag-only VLPs but not to purified Env suggested an Env-independent mode of binding to some component of Gag-only VLPs, such as lipids in cell membrane, host proteins incorporated into budded particles, or an HIV protein component of Gag.


Association of VH4-59 Antibody Variable Gene Usage with Recognition of an Immunodominant Epitope on the HIV-1 Gag Protein.

Chukwuma VU, Hicar MD, Chen X, Nicholas KJ, Joyner A, Kalams SA, Landucci G, Forthal DN, Spearman PW, Crowe JE - PLoS ONE (2015)

Binding of VH4-59 encoded antibodies to HIV antigens.Binding of mAb b12 or VH4-59 gene-encoded mAbs at a concentration of 1 μg/mL to Env VLP (black), Gag-only VLP (grey), BaL gp120 (white), or YU2 gp140 (pattern) tested by ELISA.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4520566&req=5

pone.0133509.g002: Binding of VH4-59 encoded antibodies to HIV antigens.Binding of mAb b12 or VH4-59 gene-encoded mAbs at a concentration of 1 μg/mL to Env VLP (black), Gag-only VLP (grey), BaL gp120 (white), or YU2 gp140 (pattern) tested by ELISA.
Mentions: To characterize the binding phenotype of these VH4-59 gene-encoded mAbs, we synthesized genes encoding these mAbs as cDNAs optimized for expression in mammalian cells and expressed recombinant IgGs in 293F cells. The purified IgGs were examined for binding to VLPs displaying envelope (Env-VLP), VLPs lacking Env (Gag-only VLPs), or purified gp120 from the BaL strain (BaL gp120). The most remarkable finding noted was the binding of mAb 3E4 to both Env-VLP and Gag-only VLP, with no binding observed to BaL gp120 protein. This finding showed that mAb 3E4 binding to the VLPs was not Env-specific. As expected, the previously described Env protein CD4-binding site-specific mAb b12 bound to Env-VLP and BaL gp120, but not to Gag-only VLPs. To determine whether this Gag-only VLP binding phenotype was prevalent among five other VH4-59 encoded mAbs, we tested binding to Env-VLP, Gag-only VLP, BaL gp120, or YU2 gp140. All the VH4-59 gene-encoded mAbs tested showed binding to the VLPs independent of Env, but binding was not observed to purified Env proteins in monomeric or trimeric forms (Fig 2). The binding to Gag-only VLPs but not to purified Env suggested an Env-independent mode of binding to some component of Gag-only VLPs, such as lipids in cell membrane, host proteins incorporated into budded particles, or an HIV protein component of Gag.

Bottom Line: We found no evidence that mAb 3E4 exhibited any function in laboratory studies aimed at elucidating the immunologic activity, including assays for neutralization, Ab-dependent cell-mediated virus inhibition, or enhanced T cell reactivity caused by Gag-3E4 complexes.The findings suggest this immunodominant epitope in Gag protein, which is associated with VH4-59 germline gene usage, may induce a high level of B cells that encode binding but non-functional antibodies that occupy significant repertoire space following HIV infection.The studies define an additional specific molecular mechanism in the immune distraction activity of the HIV virion.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, Tennessee, United States of America.

ABSTRACT
The human antibody response against HIV-1 infection recognizes diverse antigenic subunits of the virion, and includes a high level of antibodies to the Gag protein. We report here the isolation and characterization of a subset of Gag-specific human monoclonal antibodies (mAbs) that were prevalent in the antibody repertoire of an HIV-infected individual. Several lineages of Gag-specifc mAbs were encoded by a single antibody heavy chain variable region, VH4-59, and a representative antibody from this group designated mAb 3E4 recognized a linear epitope on the globular head of the p17 subunit of Gag. We found no evidence that mAb 3E4 exhibited any function in laboratory studies aimed at elucidating the immunologic activity, including assays for neutralization, Ab-dependent cell-mediated virus inhibition, or enhanced T cell reactivity caused by Gag-3E4 complexes. The findings suggest this immunodominant epitope in Gag protein, which is associated with VH4-59 germline gene usage, may induce a high level of B cells that encode binding but non-functional antibodies that occupy significant repertoire space following HIV infection. The studies define an additional specific molecular mechanism in the immune distraction activity of the HIV virion.

No MeSH data available.


Related in: MedlinePlus