Antibody conjugation approach enhances breadth and potency of neutralization of anti-HIV-1 antibodies and CD4-IgG.

Broadly neutralizing antibodies PG9 and PG16 effectively neutralize 70 to 80% of circulating HIV-1 isolates. In this study, the neutralization abilities of PG9 and PG16 were further enhanced by bioconjugation with aplaviroc, a small-molecule inhibitor of virus entry into host cells. A novel air-stable diazonium hexafluorophosphate reagent that allows for rapid, tyrosine-selective functionalization of proteins and antibodies under mild conditions was used to prepare a series of aplaviroc-conjugated antibodies, including b12, 2G12, PG9, PG16, and CD4-IgG. The conjugated antibodies blocked HIV-1 entry through two mechanisms: by binding to the virus itself and by blocking the CCR5 receptor on host cells. Chemical modification did not significantly alter the potency of the parent antibodies against nonresistant HIV-1 strains. Conjugation did not alter the pharmacokinetics of a model IgG in blood. The PG9-aplaviroc conjugate was tested against a panel of 117 HIV-1 strains and was found to neutralize 100% of the viruses. PG9-aplaviroc conjugate IC50s were lower than those of PG9 in neutralization studies of 36 of the 117 HIV-1 strains. These results support this new approach to bispecific antibodies and offer a potential new strategy for combining HIV-1 therapies.

Safety and immunogenicity of modified vaccinia Ankara in hematopoietic stem cell transplant recipients: a randomized, controlled trial.

BACKGROUND: Modified vaccinia Ankara (MVA-BN, IMVAMUNE) is emerging as a primary immunogen and as a delivery system to treat or prevent a wide range of diseases. Defining the safety and immunogenicity of MVA-BN in key populations is therefore important. METHODS: We performed a dose-escalation study of MVA-BN administered subcutaneously in 2 doses, one on day 0 and another on day 28. Twenty-four hematopoietic stem cell transplant recipients were enrolled sequentially into the study, and vaccine or placebo was administered under a randomized, double-blind allocation. Ten subjects received vaccine containing 10(7) median tissue culture infective doses (TCID50) of MVA-BN, 10 subjects received vaccine containing 10(8) TCID50 of MVA-BN, and 4 subjects received placebo. RESULTS: MVA-BN was generally well tolerated at both doses. No vaccine-related serious adverse events were identified. Transient local reactogenicity was more frequently seen at the higher dose. Neutralizing antibodies (NAb) to Vaccinia virus (VACV) were elicited by both doses of MVA-BN and were greater for the higher dose. Median peak anti-VACV NAb titers were 1:49 in the lower-dose group and 1:118 in the higher-dose group. T-cell immune responses to VACV were detected by an interferon γ enzyme-linked immunosorbent spot assay and were higher in the higher-dose group. CONCLUSIONS: MVA-BN is safe, well tolerated, and immunogenic in HSCT recipients. These data support the use of 10(8) TCID50 of MVA-BN in this population. CLINICAL TRIALS REGISTRATION: NCT00565929.

First-in-human evaluation of the safety and immunogenicity of a recombinant adenovirus serotype 26 HIV-1 Env vaccine (IPCAVD 001).

BACKGROUND: We report the first-in-human safety and immunogenicity assessment of a prototype Ad26 vector-based human immunodeficiency virus (HIV) vaccine in humans. METHODS: Sixty Ad26-seronegative, healthy, HIV-uninfected subjects were enrolled in a randomized, double-blinded, placebo-controlled, dose-escalation phase 1 study. Five groups of 12 subjects received 10(9)-10(11) vp of the Ad26-EnvA vaccine (N = 10/group) or placebo (N = 2/group) at weeks 0 and 24 or weeks 0, 4, and 24. Safety and immunogenicity were assessed. RESULTS: Self-limited reactogenicity was observed after the initial immunization at the highest (10(11) vp) dose. No product-related SAEs were observed. All subjects who received the Ad26-EnvA vaccine developed Ad26 NAb titers, EnvA-specific enzyme-linked immunosorbent assays (ELISA) titers, and EnvA-specific enzyme-linked immunospot assays (ELISPOT) responses. These responses persisted at week 52. At week 28 in the 10(9), 10(10), 10(11) vp 3-dose and the 10(10) and 5 × 10(10) vp 2-dose groups, geometric mean EnvA ELISA titers were 6113, 12 470, 8545, 3470, and 9655 and mean EnvA ELISPOT responses were 397, 178, 736, 196, and 1311 SFC/10(6) peripheral blood mononuclear cells, respectively. CONCLUSION: This Ad26 vectored vaccine was generally safe and immunogenic at all doses tested. Reactogenicity was minimal with doses of 5 × 10(10) vp or less. Ad26 is a promising new vaccine vector for HIV-1. CLINICAL TRIALS REGISTRATION: NCT00618605.

HIV-1 ENVELOPE. Effect of the cytoplasmic domain on antigenic characteristics of HIV-1 envelope glycoprotein.

A major goal for HIV-1 vaccine development is the production of an immunogen to mimic native, functional HIV-1 envelope trimeric spikes (Env) on the virion surface. We lack a reliable description of a native, functional trimer, however, because of inherent instability and heterogeneity in most preparations. We describe here two conformationally homogeneous Envs derived from difficult-to-neutralize primary isolates. All their non-neutralizing epitopes are fully concealed and independent of their proteolytic processing. Most broadly neutralizing antibodies (bnAbs) recognize these native trimers. Truncation of their cytoplasmic tail has little effect on membrane fusion, but it diminishes binding to trimer-specific bnAbs while exposing non-neutralizing epitopes. These results yield a more accurate antigenic picture than hitherto possible of a genuinely untriggered and functional HIV-1 Env; they can guide effective vaccine development.