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Broad-spectrum inhibition of HIV-1 by a monoclonal antibody directed against a gp120-induced epitope of CD4.

Burastero SE, Frigerio B, Lopalco L, Sironi F, Breda D, Longhi R, Scarlatti G, Canevari S, Figini M, Lusso P - PLoS ONE (2011)

Bottom Line: In particular, a CD4-specific MAb designated DB81 (IgG1Κ) was found to preferentially bind to a complex-enhanced epitope on the D2 domain of human CD4.Functionally, MAb DB81 displayed broad HIV-1-inhibitory activity, but it did not exert suppressive effects on T-cell activation in vitro.Due to its broad-spectrum anti-HIV-1 activity and lack of immunosuppressive effects, a humanized derivative of MAb DB81 could provide a useful complement to current preventive or therapeutic strategies against HIV-1.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Transplantation and Infectious Diseases, San Raffaele Scientific Institute, Milan, Italy. s.burastero@hsr.it

ABSTRACT
To penetrate susceptible cells, HIV-1 sequentially interacts with two highly conserved cellular receptors, CD4 and a chemokine receptor like CCR5 or CXCR4. Monoclonal antibodies (MAbs) directed against such receptors are currently under clinical investigation as potential preventive or therapeutic agents. We immunized Balb/c mice with molecular complexes of the native, trimeric HIV-1 envelope (Env) bound to a soluble form of the human CD4 receptor. Sera from immunized mice were found to contain gp120-CD4 complex-enhanced antibodies and showed broad-spectrum HIV-1-inhibitory activity. A proportion of MAbs derived from these mice preferentially recognized complex-enhanced epitopes. In particular, a CD4-specific MAb designated DB81 (IgG1Κ) was found to preferentially bind to a complex-enhanced epitope on the D2 domain of human CD4. MAb DB81 also recognized chimpanzee CD4, but not baboon or macaque CD4, which exhibit sequence divergence in the D2 domain. Functionally, MAb DB81 displayed broad HIV-1-inhibitory activity, but it did not exert suppressive effects on T-cell activation in vitro. The variable regions of the heavy and light chains of MAb DB81 were sequenced. Due to its broad-spectrum anti-HIV-1 activity and lack of immunosuppressive effects, a humanized derivative of MAb DB81 could provide a useful complement to current preventive or therapeutic strategies against HIV-1.

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Immunosuppressive and complement-fixing effects of MAb DB81.A. Inhibition of PBMC proliferation by MAb DB81. PBMC from 4 healthy blood donors were incubated with the indicated stimuli in a 5-day proliferation assay. Either no inhibitors (“nil”) or the indicated mAbs (3 µg/ml) were added at the beginning of the culture time. Proliferation was measured by incorporation of tritiated thymidine in triplicate wells. The values indicate the mean ± standard error of the mean. B. Complement fixation by MAb DB81. Flow cytometry analysis of PM-1 cells treated with complement only (C, top left) or with C plus thymoglobulin (polyclonal rabbit antibodies to human thymocyte antigens, ATG, bottom right), C plus MAb Leu-3a (bottom left) or C plus DB81 (top right). Cells were stained with propidium iodide as a marker for cell death. Numbers in panels indicate the percent of stained (complement lysed, dead) cells, which fell within the double arrow markers in the different experimental settings.
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pone-0022081-g008: Immunosuppressive and complement-fixing effects of MAb DB81.A. Inhibition of PBMC proliferation by MAb DB81. PBMC from 4 healthy blood donors were incubated with the indicated stimuli in a 5-day proliferation assay. Either no inhibitors (“nil”) or the indicated mAbs (3 µg/ml) were added at the beginning of the culture time. Proliferation was measured by incorporation of tritiated thymidine in triplicate wells. The values indicate the mean ± standard error of the mean. B. Complement fixation by MAb DB81. Flow cytometry analysis of PM-1 cells treated with complement only (C, top left) or with C plus thymoglobulin (polyclonal rabbit antibodies to human thymocyte antigens, ATG, bottom right), C plus MAb Leu-3a (bottom left) or C plus DB81 (top right). Cells were stained with propidium iodide as a marker for cell death. Numbers in panels indicate the percent of stained (complement lysed, dead) cells, which fell within the double arrow markers in the different experimental settings.

Mentions: Since a major concern with the potential clinical use of antibodies directed against T cell-expressed antigens is the risk of inducing immunosuppression, we evaluated the effects of MAb DB81 on nominal antigen-induced T-cell proliferation. As shown in Figure 8A, MAb DB81 did not exert inhibitory effects on the proliferation of primary human PBMC stimulated with a nominal antigen (tetanus toxoid) or with a polyclonal activator (PHA), while the isotype-matched anti-CD4 MAb Leu3a displayed marked suppressive effects. MAb DB81 was also poorly efficient in inducing complement fixation and cytolysis, as measured by propidium iodide incorporation following exposure of MAb-treated cells to rabbit complement; again, the isotype matched MAb Leu3a displayed a markedly higher activity (Fig. 8B).


Broad-spectrum inhibition of HIV-1 by a monoclonal antibody directed against a gp120-induced epitope of CD4.

Burastero SE, Frigerio B, Lopalco L, Sironi F, Breda D, Longhi R, Scarlatti G, Canevari S, Figini M, Lusso P - PLoS ONE (2011)

Immunosuppressive and complement-fixing effects of MAb DB81.A. Inhibition of PBMC proliferation by MAb DB81. PBMC from 4 healthy blood donors were incubated with the indicated stimuli in a 5-day proliferation assay. Either no inhibitors (“nil”) or the indicated mAbs (3 µg/ml) were added at the beginning of the culture time. Proliferation was measured by incorporation of tritiated thymidine in triplicate wells. The values indicate the mean ± standard error of the mean. B. Complement fixation by MAb DB81. Flow cytometry analysis of PM-1 cells treated with complement only (C, top left) or with C plus thymoglobulin (polyclonal rabbit antibodies to human thymocyte antigens, ATG, bottom right), C plus MAb Leu-3a (bottom left) or C plus DB81 (top right). Cells were stained with propidium iodide as a marker for cell death. Numbers in panels indicate the percent of stained (complement lysed, dead) cells, which fell within the double arrow markers in the different experimental settings.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3139607&req=5

pone-0022081-g008: Immunosuppressive and complement-fixing effects of MAb DB81.A. Inhibition of PBMC proliferation by MAb DB81. PBMC from 4 healthy blood donors were incubated with the indicated stimuli in a 5-day proliferation assay. Either no inhibitors (“nil”) or the indicated mAbs (3 µg/ml) were added at the beginning of the culture time. Proliferation was measured by incorporation of tritiated thymidine in triplicate wells. The values indicate the mean ± standard error of the mean. B. Complement fixation by MAb DB81. Flow cytometry analysis of PM-1 cells treated with complement only (C, top left) or with C plus thymoglobulin (polyclonal rabbit antibodies to human thymocyte antigens, ATG, bottom right), C plus MAb Leu-3a (bottom left) or C plus DB81 (top right). Cells were stained with propidium iodide as a marker for cell death. Numbers in panels indicate the percent of stained (complement lysed, dead) cells, which fell within the double arrow markers in the different experimental settings.
Mentions: Since a major concern with the potential clinical use of antibodies directed against T cell-expressed antigens is the risk of inducing immunosuppression, we evaluated the effects of MAb DB81 on nominal antigen-induced T-cell proliferation. As shown in Figure 8A, MAb DB81 did not exert inhibitory effects on the proliferation of primary human PBMC stimulated with a nominal antigen (tetanus toxoid) or with a polyclonal activator (PHA), while the isotype-matched anti-CD4 MAb Leu3a displayed marked suppressive effects. MAb DB81 was also poorly efficient in inducing complement fixation and cytolysis, as measured by propidium iodide incorporation following exposure of MAb-treated cells to rabbit complement; again, the isotype matched MAb Leu3a displayed a markedly higher activity (Fig. 8B).

Bottom Line: In particular, a CD4-specific MAb designated DB81 (IgG1Κ) was found to preferentially bind to a complex-enhanced epitope on the D2 domain of human CD4.Functionally, MAb DB81 displayed broad HIV-1-inhibitory activity, but it did not exert suppressive effects on T-cell activation in vitro.Due to its broad-spectrum anti-HIV-1 activity and lack of immunosuppressive effects, a humanized derivative of MAb DB81 could provide a useful complement to current preventive or therapeutic strategies against HIV-1.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Transplantation and Infectious Diseases, San Raffaele Scientific Institute, Milan, Italy. s.burastero@hsr.it

ABSTRACT
To penetrate susceptible cells, HIV-1 sequentially interacts with two highly conserved cellular receptors, CD4 and a chemokine receptor like CCR5 or CXCR4. Monoclonal antibodies (MAbs) directed against such receptors are currently under clinical investigation as potential preventive or therapeutic agents. We immunized Balb/c mice with molecular complexes of the native, trimeric HIV-1 envelope (Env) bound to a soluble form of the human CD4 receptor. Sera from immunized mice were found to contain gp120-CD4 complex-enhanced antibodies and showed broad-spectrum HIV-1-inhibitory activity. A proportion of MAbs derived from these mice preferentially recognized complex-enhanced epitopes. In particular, a CD4-specific MAb designated DB81 (IgG1Κ) was found to preferentially bind to a complex-enhanced epitope on the D2 domain of human CD4. MAb DB81 also recognized chimpanzee CD4, but not baboon or macaque CD4, which exhibit sequence divergence in the D2 domain. Functionally, MAb DB81 displayed broad HIV-1-inhibitory activity, but it did not exert suppressive effects on T-cell activation in vitro. The variable regions of the heavy and light chains of MAb DB81 were sequenced. Due to its broad-spectrum anti-HIV-1 activity and lack of immunosuppressive effects, a humanized derivative of MAb DB81 could provide a useful complement to current preventive or therapeutic strategies against HIV-1.

Show MeSH