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Capacity of Broadly Neutralizing Antibodies to Inhibit HIV-1 Cell-Cell Transmission Is Strain- and Epitope-Dependent.

Reh L, Magnus C, Schanz M, Weber J, Uhr T, Rusert P, Trkola A - PLoS Pathog. (2015)

Bottom Line: Cell-cell spread is known to promote a highly efficient infection with HIV-1 which can inflict dramatic losses in neutralization potency compared to free virus infection.Activity loss varied considerably between virus strains and was inversely associated with neutralization of free virus spread for V1V2- and V3-directed bnAbs.Pre-CD4 attachment activity proved strongest amongst CD4bs bnAbs and varied substantially for V3 and V1V2 loop bnAbs in a strain-dependent manner.

View Article: PubMed Central - PubMed

Affiliation: Institute of Medical Virology, University of Zürich, Zürich, Switzerland.

ABSTRACT
An increasing number of broadly neutralizing antibodies (bnAbs) are considered leads for HIV-1 vaccine development and novel therapeutics. Here, we systematically explored the capacity of bnAbs to neutralize HIV-1 prior to and post-CD4 engagement and to block HIV-1 cell-cell transmission. Cell-cell spread is known to promote a highly efficient infection with HIV-1 which can inflict dramatic losses in neutralization potency compared to free virus infection. Selection of bnAbs that are capable of suppressing HIV irrespective of the transmission mode therefore needs to be considered to ascertain their in vivo activity in therapeutic use and vaccines. Employing assay systems that allow for unambiguous discrimination between free virus and cell-cell transmission to T cells, we probed a panel of 16 bnAbs for their activity against 11 viruses from subtypes A, B and C during both transmission modes. Over a wide range of bnAb-virus combinations tested, inhibitory activity against HIV-1 cell-cell transmission was strongly decreased compared to free virus transmission. Activity loss varied considerably between virus strains and was inversely associated with neutralization of free virus spread for V1V2- and V3-directed bnAbs. In rare bnAb-virus combinations, inhibition for both transmission modes was comparable but no bnAb potently blocked cell-cell transmission across all probed virus strains. Mathematical analysis indicated an increased probability of bnAb resistance mutations to arise in cell-cell rather than free virus spread, further highlighting the need to block this pathway. Importantly, the capacity to efficiently neutralize prior to CD4 engagement correlated with the inhibition efficacy against free virus but not cell-cell transmitted virus. Pre-CD4 attachment activity proved strongest amongst CD4bs bnAbs and varied substantially for V3 and V1V2 loop bnAbs in a strain-dependent manner. In summary, bnAb activity against divergent viruses varied depending on the transmission mode and differed depending on the window of action during the entry process, underscoring that powerful combinations of bnAbs are needed for in vivo application.

No MeSH data available.


Related in: MedlinePlus

The capacity to neutralize free viruses prior to completion of CD4 attachment varies across bnAb classes.A: Schematic of free virus infection of A3.01-CCR5 target cells to measure total and pre-attachment activity of bnAbs. Total activity of each bnAb-virus combination (where bnAbs were present throughout the infection process) was set to 100% and pre-attachment inhibition displayed relative to it. To assess pre-attachment activity, bnAbs were removed following attachment by spinoculation. B: Pre-attachment neutralization activity is strain- and epitope-dependent. Pre-attachment activity (relative, %) of the bnAb classes CD4bs, V3 glycans, V1V2 loop, MPER was assessed against the indicated virus strains. Data are means of two to three independent experiments. C: Pre-attachment activity correlates with high potency against free virus, decreased post- attachment inhibition capacity and loss in activity during cell-cell transmission. Summary of the interdependencies of pre-attachment, post-attachment inhibition, IC50 for free virus inhibition, IC50 for cell-cell inhibition and loss in activity during cell-cell inhibition. Correlations were determined by Spearman correlation based on the untransformed data sets and are shown in S8 Fig. R and p values are depicted. n.s. indicates a non-significant correlation. Direct correlation is denoted in blue, inverse correlation in orange.
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ppat.1004966.g007: The capacity to neutralize free viruses prior to completion of CD4 attachment varies across bnAb classes.A: Schematic of free virus infection of A3.01-CCR5 target cells to measure total and pre-attachment activity of bnAbs. Total activity of each bnAb-virus combination (where bnAbs were present throughout the infection process) was set to 100% and pre-attachment inhibition displayed relative to it. To assess pre-attachment activity, bnAbs were removed following attachment by spinoculation. B: Pre-attachment neutralization activity is strain- and epitope-dependent. Pre-attachment activity (relative, %) of the bnAb classes CD4bs, V3 glycans, V1V2 loop, MPER was assessed against the indicated virus strains. Data are means of two to three independent experiments. C: Pre-attachment activity correlates with high potency against free virus, decreased post- attachment inhibition capacity and loss in activity during cell-cell transmission. Summary of the interdependencies of pre-attachment, post-attachment inhibition, IC50 for free virus inhibition, IC50 for cell-cell inhibition and loss in activity during cell-cell inhibition. Correlations were determined by Spearman correlation based on the untransformed data sets and are shown in S8 Fig. R and p values are depicted. n.s. indicates a non-significant correlation. Direct correlation is denoted in blue, inverse correlation in orange.

Mentions: Comparing total and post-attachment activity additionally provided insight into the pre-attachment activity of the bnAbs, which was measured as the activity against the unbound virus (during pre-incubation) and the initial steps of CD4 engagement (during spinoculation) in our experimental setup (Fig 7A). While a low post-attachment activity implies that a bnAb preferentially acts prior to CD4 engagement, the reverse is not necessarily the case as action during both stages, pre- and post-CD4 attachment may occur. Thus, to investigate the pre-attachment activity more precisely, we assessed the potential of bnAbs to neutralize when solely present before CD4 binding has been completed (Fig 7A). To this end, we first pre-incubated virus and bnAbs to allow for bnAb binding to the native spike. Concentrations of bnAbs were chosen to yield maximal inhibition (S5 Table). During subsequent spinoculation of the inoculum onto the target cells, virus binding to CD4 was initiated [25] allowing bnAb binding to epitopes exposed in the CD4-bound stage. Spinoculation was performed at room temperature to permit trimer binding to CD4 while arresting further structural rearrangements and fusion. The excess bnAbs and unbound virus were washed off and the infected target cells cultivated in absence of bnAbs. Efficacy in blocking virus entry was compared to controls in which bnAbs remained in the culture after spinoculation and therefore provided reference values for total neutralization activity covering bnAb action during the entire infection period (Fig 7A).


Capacity of Broadly Neutralizing Antibodies to Inhibit HIV-1 Cell-Cell Transmission Is Strain- and Epitope-Dependent.

Reh L, Magnus C, Schanz M, Weber J, Uhr T, Rusert P, Trkola A - PLoS Pathog. (2015)

The capacity to neutralize free viruses prior to completion of CD4 attachment varies across bnAb classes.A: Schematic of free virus infection of A3.01-CCR5 target cells to measure total and pre-attachment activity of bnAbs. Total activity of each bnAb-virus combination (where bnAbs were present throughout the infection process) was set to 100% and pre-attachment inhibition displayed relative to it. To assess pre-attachment activity, bnAbs were removed following attachment by spinoculation. B: Pre-attachment neutralization activity is strain- and epitope-dependent. Pre-attachment activity (relative, %) of the bnAb classes CD4bs, V3 glycans, V1V2 loop, MPER was assessed against the indicated virus strains. Data are means of two to three independent experiments. C: Pre-attachment activity correlates with high potency against free virus, decreased post- attachment inhibition capacity and loss in activity during cell-cell transmission. Summary of the interdependencies of pre-attachment, post-attachment inhibition, IC50 for free virus inhibition, IC50 for cell-cell inhibition and loss in activity during cell-cell inhibition. Correlations were determined by Spearman correlation based on the untransformed data sets and are shown in S8 Fig. R and p values are depicted. n.s. indicates a non-significant correlation. Direct correlation is denoted in blue, inverse correlation in orange.
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Related In: Results  -  Collection

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ppat.1004966.g007: The capacity to neutralize free viruses prior to completion of CD4 attachment varies across bnAb classes.A: Schematic of free virus infection of A3.01-CCR5 target cells to measure total and pre-attachment activity of bnAbs. Total activity of each bnAb-virus combination (where bnAbs were present throughout the infection process) was set to 100% and pre-attachment inhibition displayed relative to it. To assess pre-attachment activity, bnAbs were removed following attachment by spinoculation. B: Pre-attachment neutralization activity is strain- and epitope-dependent. Pre-attachment activity (relative, %) of the bnAb classes CD4bs, V3 glycans, V1V2 loop, MPER was assessed against the indicated virus strains. Data are means of two to three independent experiments. C: Pre-attachment activity correlates with high potency against free virus, decreased post- attachment inhibition capacity and loss in activity during cell-cell transmission. Summary of the interdependencies of pre-attachment, post-attachment inhibition, IC50 for free virus inhibition, IC50 for cell-cell inhibition and loss in activity during cell-cell inhibition. Correlations were determined by Spearman correlation based on the untransformed data sets and are shown in S8 Fig. R and p values are depicted. n.s. indicates a non-significant correlation. Direct correlation is denoted in blue, inverse correlation in orange.
Mentions: Comparing total and post-attachment activity additionally provided insight into the pre-attachment activity of the bnAbs, which was measured as the activity against the unbound virus (during pre-incubation) and the initial steps of CD4 engagement (during spinoculation) in our experimental setup (Fig 7A). While a low post-attachment activity implies that a bnAb preferentially acts prior to CD4 engagement, the reverse is not necessarily the case as action during both stages, pre- and post-CD4 attachment may occur. Thus, to investigate the pre-attachment activity more precisely, we assessed the potential of bnAbs to neutralize when solely present before CD4 binding has been completed (Fig 7A). To this end, we first pre-incubated virus and bnAbs to allow for bnAb binding to the native spike. Concentrations of bnAbs were chosen to yield maximal inhibition (S5 Table). During subsequent spinoculation of the inoculum onto the target cells, virus binding to CD4 was initiated [25] allowing bnAb binding to epitopes exposed in the CD4-bound stage. Spinoculation was performed at room temperature to permit trimer binding to CD4 while arresting further structural rearrangements and fusion. The excess bnAbs and unbound virus were washed off and the infected target cells cultivated in absence of bnAbs. Efficacy in blocking virus entry was compared to controls in which bnAbs remained in the culture after spinoculation and therefore provided reference values for total neutralization activity covering bnAb action during the entire infection period (Fig 7A).

Bottom Line: Cell-cell spread is known to promote a highly efficient infection with HIV-1 which can inflict dramatic losses in neutralization potency compared to free virus infection.Activity loss varied considerably between virus strains and was inversely associated with neutralization of free virus spread for V1V2- and V3-directed bnAbs.Pre-CD4 attachment activity proved strongest amongst CD4bs bnAbs and varied substantially for V3 and V1V2 loop bnAbs in a strain-dependent manner.

View Article: PubMed Central - PubMed

Affiliation: Institute of Medical Virology, University of Zürich, Zürich, Switzerland.

ABSTRACT
An increasing number of broadly neutralizing antibodies (bnAbs) are considered leads for HIV-1 vaccine development and novel therapeutics. Here, we systematically explored the capacity of bnAbs to neutralize HIV-1 prior to and post-CD4 engagement and to block HIV-1 cell-cell transmission. Cell-cell spread is known to promote a highly efficient infection with HIV-1 which can inflict dramatic losses in neutralization potency compared to free virus infection. Selection of bnAbs that are capable of suppressing HIV irrespective of the transmission mode therefore needs to be considered to ascertain their in vivo activity in therapeutic use and vaccines. Employing assay systems that allow for unambiguous discrimination between free virus and cell-cell transmission to T cells, we probed a panel of 16 bnAbs for their activity against 11 viruses from subtypes A, B and C during both transmission modes. Over a wide range of bnAb-virus combinations tested, inhibitory activity against HIV-1 cell-cell transmission was strongly decreased compared to free virus transmission. Activity loss varied considerably between virus strains and was inversely associated with neutralization of free virus spread for V1V2- and V3-directed bnAbs. In rare bnAb-virus combinations, inhibition for both transmission modes was comparable but no bnAb potently blocked cell-cell transmission across all probed virus strains. Mathematical analysis indicated an increased probability of bnAb resistance mutations to arise in cell-cell rather than free virus spread, further highlighting the need to block this pathway. Importantly, the capacity to efficiently neutralize prior to CD4 engagement correlated with the inhibition efficacy against free virus but not cell-cell transmitted virus. Pre-CD4 attachment activity proved strongest amongst CD4bs bnAbs and varied substantially for V3 and V1V2 loop bnAbs in a strain-dependent manner. In summary, bnAb activity against divergent viruses varied depending on the transmission mode and differed depending on the window of action during the entry process, underscoring that powerful combinations of bnAbs are needed for in vivo application.

No MeSH data available.


Related in: MedlinePlus