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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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Inhibitory effect of MAb DB81 on HIV-1 Env-mediated fusion and infection.A. Effect of MAb DB81 on HIV-1 Env-mediated fusion. Chronically infected PM-1 cells were used as effector cells. NIH 3T3 cells expressing CD4 and the appropriate coreceptor were used as target cells. Fusion inhibition is expressed as percent of the fusion obtained with the untreated control (no antibody added). B. Comparison of the inhibitory potency of MAb DB81 with that of other HIV-1 inhibitors. Comparison of fusion inhibition by MAb DB81 with that obtained with equimolar amounts of another mAb to human CD4 (Leu3a) or the coreceptor inhibitor RANTES. PM-1 cells chronically infected with HIV-1 Ba-L were used as effectors. NIH 3T3 cells expressing the CCR5 coreceptor were used as targets. Results are expressed as percent of the fusion measured in the positive control (no inhibitors added). C. Effect of MAb DB81 on HIV-1 infection in primary human PBMC. PBMC from healthy blood donors were infected with the indicated HIV-1 strains in the presence or absence of MAb DB81. HIV-1 92US077 and 92US714 are two primary isolates derived directly from patient blood cells and minimally passaged ex vivo exclusively in primary cells. HIV-1 replication was measured after 4 days by p24 ELISA and expressed as percent of p24 measured in control untreated cultures. IC50 values were calculated using the PRISM software.
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pone-0022081-g007: Inhibitory effect of MAb DB81 on HIV-1 Env-mediated fusion and infection.A. Effect of MAb DB81 on HIV-1 Env-mediated fusion. Chronically infected PM-1 cells were used as effector cells. NIH 3T3 cells expressing CD4 and the appropriate coreceptor were used as target cells. Fusion inhibition is expressed as percent of the fusion obtained with the untreated control (no antibody added). B. Comparison of the inhibitory potency of MAb DB81 with that of other HIV-1 inhibitors. Comparison of fusion inhibition by MAb DB81 with that obtained with equimolar amounts of another mAb to human CD4 (Leu3a) or the coreceptor inhibitor RANTES. PM-1 cells chronically infected with HIV-1 Ba-L were used as effectors. NIH 3T3 cells expressing the CCR5 coreceptor were used as targets. Results are expressed as percent of the fusion measured in the positive control (no inhibitors added). C. Effect of MAb DB81 on HIV-1 infection in primary human PBMC. PBMC from healthy blood donors were infected with the indicated HIV-1 strains in the presence or absence of MAb DB81. HIV-1 92US077 and 92US714 are two primary isolates derived directly from patient blood cells and minimally passaged ex vivo exclusively in primary cells. HIV-1 replication was measured after 4 days by p24 ELISA and expressed as percent of p24 measured in control untreated cultures. IC50 values were calculated using the PRISM software.

Mentions: Next, we examined the ability of MAb DB81 to block fusion mediated by a panel of HIV-1 Envs derived from both laboratory adapted and primary isolates. As shown in Figure 7A, MAb DB81 efficiently inhibited fusion mediated by the Env of three different HIV-1 isolates with diverse coreceptor-usage phenotype, Ba-L (R5), B117 (R5X4), IIIB (X4) and 6195 (R5X4). In these assays, MAb DB81 showed a potency similar to that of Leu3A, a reference anti-CD4 MAb directed against the gp120-binding site, and RANTES, a CCR5 ligand (Fig. 7B). Taken together, these results indicate that the DB81 epitope is accessible on the native oligomeric gp120, and is conserved in CD4-Env complexes formed by HIV-1 strains with different coreceptors-usage phenotype.


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)

Inhibitory effect of MAb DB81 on HIV-1 Env-mediated fusion and infection.A. Effect of MAb DB81 on HIV-1 Env-mediated fusion. Chronically infected PM-1 cells were used as effector cells. NIH 3T3 cells expressing CD4 and the appropriate coreceptor were used as target cells. Fusion inhibition is expressed as percent of the fusion obtained with the untreated control (no antibody added). B. Comparison of the inhibitory potency of MAb DB81 with that of other HIV-1 inhibitors. Comparison of fusion inhibition by MAb DB81 with that obtained with equimolar amounts of another mAb to human CD4 (Leu3a) or the coreceptor inhibitor RANTES. PM-1 cells chronically infected with HIV-1 Ba-L were used as effectors. NIH 3T3 cells expressing the CCR5 coreceptor were used as targets. Results are expressed as percent of the fusion measured in the positive control (no inhibitors added). C. Effect of MAb DB81 on HIV-1 infection in primary human PBMC. PBMC from healthy blood donors were infected with the indicated HIV-1 strains in the presence or absence of MAb DB81. HIV-1 92US077 and 92US714 are two primary isolates derived directly from patient blood cells and minimally passaged ex vivo exclusively in primary cells. HIV-1 replication was measured after 4 days by p24 ELISA and expressed as percent of p24 measured in control untreated cultures. IC50 values were calculated using the PRISM software.
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Related In: Results  -  Collection

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pone-0022081-g007: Inhibitory effect of MAb DB81 on HIV-1 Env-mediated fusion and infection.A. Effect of MAb DB81 on HIV-1 Env-mediated fusion. Chronically infected PM-1 cells were used as effector cells. NIH 3T3 cells expressing CD4 and the appropriate coreceptor were used as target cells. Fusion inhibition is expressed as percent of the fusion obtained with the untreated control (no antibody added). B. Comparison of the inhibitory potency of MAb DB81 with that of other HIV-1 inhibitors. Comparison of fusion inhibition by MAb DB81 with that obtained with equimolar amounts of another mAb to human CD4 (Leu3a) or the coreceptor inhibitor RANTES. PM-1 cells chronically infected with HIV-1 Ba-L were used as effectors. NIH 3T3 cells expressing the CCR5 coreceptor were used as targets. Results are expressed as percent of the fusion measured in the positive control (no inhibitors added). C. Effect of MAb DB81 on HIV-1 infection in primary human PBMC. PBMC from healthy blood donors were infected with the indicated HIV-1 strains in the presence or absence of MAb DB81. HIV-1 92US077 and 92US714 are two primary isolates derived directly from patient blood cells and minimally passaged ex vivo exclusively in primary cells. HIV-1 replication was measured after 4 days by p24 ELISA and expressed as percent of p24 measured in control untreated cultures. IC50 values were calculated using the PRISM software.
Mentions: Next, we examined the ability of MAb DB81 to block fusion mediated by a panel of HIV-1 Envs derived from both laboratory adapted and primary isolates. As shown in Figure 7A, MAb DB81 efficiently inhibited fusion mediated by the Env of three different HIV-1 isolates with diverse coreceptor-usage phenotype, Ba-L (R5), B117 (R5X4), IIIB (X4) and 6195 (R5X4). In these assays, MAb DB81 showed a potency similar to that of Leu3A, a reference anti-CD4 MAb directed against the gp120-binding site, and RANTES, a CCR5 ligand (Fig. 7B). Taken together, these results indicate that the DB81 epitope is accessible on the native oligomeric gp120, and is conserved in CD4-Env complexes formed by HIV-1 strains with different coreceptors-usage phenotype.

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
Related in: MedlinePlus