Immunotherapy With the PreS-based Grass Pollen Allergy Vaccine BM32 Induces Antibody Responses Protecting Against Hepatitis B Infection

Abstract

Background: We have constructed and clinically evaluated a hypoallergenic vaccine for grass pollen allergy, BM32, which is based on fusion proteins consisting of peptides from the IgE binding sites of the major grass pollen allergens fused to preS (preS1+preS2), a domain of the hepatitis B virus (HBV) large envelope protein which mediates the viral attachment and entry. Aim of this study was the characterization of the HBV-specific immune response induced by vaccination of allergic patients with BM32 and the investigation of the vaccines' potential to protect against infection with HBV.

Methods: Hepatitis B-specific antibody and T cell responses of patients vaccinated with BM32 were studied using recombinant preS and synthetic overlapping peptides spanning the preS sequence. The specificities of the antibody responses were compared with those of patients with chronic HBV infection. Furthermore, the capacity of BM32-induced antibodies, to inhibit HBV infection was investigated using HepG2-hNTCP cell-based in vitro virus neutralization assays.

Findings: IgG antibodies from BM32-vaccinated but not of HBV-infected individuals recognized the sequence motif implicated in NTCP (sodium-taurocholate co-transporting polypeptide)-receptor interaction of the hepatitis B virus and inhibited HBV infection.

Interpretation: Our study demonstrates that the recombinant hypoallergenic grass pollen allergy vaccine BM32 induces hepatitis B-specific immune responses which protect against hepatitis B virus infection in vitro.

Keywords: Allergy; B cell epitope-based allergy vaccine; Hepatitis B; Hepatitis B surface protein; Virus neutralization; preS.

Fig. 1

Scheme for the construction of the BM32 vaccine. BM32 contains fusion proteins consisting of the preS domain (i.e., preS1 and preS2) of the large hepatitis B virus envelope protein (LHB) fused with allergen-derived peptides. LHB: Large hepatitis B virus envelope protein; MHB: Middle hepatitis B virus envelope protein; SHB: Small hepatitis B virus envelope protein.

Fig. 2

IgG responses towards preS and synthetic preS-derived overlapping peptides. Optical density values (y-axes: OD values at 405 nm) corresponding to IgG levels of rabbits immunized with (a) preS (n = 1), (b) 20 μg of BM32 (n = 2), (c) 40 μg of BM32 (n = 2) or to IgG₁ levels of groups of mice (n = 6) immunized with (d) 10 μg, (e) 20 μg or (f) 30 μg of BM32 prior to (grey bars) and after (black bars) immunization, towards preS and synthetic preS overlapping peptides P1–P8 (x-axes). Results represent medians ± interquartile ranges from triplicate determinations.

Fig. 3

Overview of the treatment period of the BM32 trial. (a) Subjects received seven injections of placebo or BM32 over two years as depicted in the time line. Visits during which blood samples were obtained are indicated. (b) IgG responses of subjects vaccinated with BM32 or placebo towards preS and synthetic preS-derived overlapping peptides. Shown are optical density values (y-axes: OD values, means of triplicate determination) corresponding to IgG levels towards preS and peptides P1–P8 measured in subjects with (red symbols) or without (black symbols) prior HBV vaccination who had been immunized with BM32 or placebo before (V5) and at different time points after immunization (V8 and V15) (x-axes). Medians (horizontal bars) and significant differences are indicated: *P < 0.05, **P < 0.01, ***P < 0.001.

Fig. 4

PreS-specific antibody responses of subjects vaccinated with BM32 or placebo and of HBV-infected individuals. Shown are optical density values (y-axes: OD values) of IgA, IgE, IgM, IgG and IgG subclass (IgG₁–IgG₄) levels specific for preS of subjects immunized with placebo (n = 8), 20 μg (n = 10) or 40 μg of BM32 (n = 12) at visit 15 as well as of HBV-infected individuals (n = 19) (x-axes). Medians are indicated by horizontal lines, significant differences are indicated: ***P < 0.001.

Fig. 5

IgG responses of subjects vaccinated with BM32 or placebo and of hepatitis B virus-infected individuals specific for preS peptides. Shown are optical density values (y-axes: OD values) of IgG levels specific for preS-derived peptides (P1–P8) of subjects immunized with placebo (n = 8), 20 μg (n = 10) or 40 μg of BM32 (n = 12) at visit 15 as well as of HBV-infected individuals (n = 19) (x-axes). Medians are indicated by horizontal lines. P1 (aa 2–31); P2 (aa 22–51); P3 (aa 42–71); P4 (aa 62–91); P5 (aa 82–111); P6 (aa 102–131); P7 (aa 122–151); P8 (aa 142–174).

Fig. 6

PreS- and peptide-specific T cell responses. (a) PreS-specific PBMC proliferations (y-axis: stimulation index SI) assessed by [³H] thymidine incorporation in subjects immunized with BM32 (n = 19) at different time points (x-axis). Medians (horizontal bars) and significant differences are indicated: *P < 0.05, **P < 0.001, ***P < 0.001. (b) Percentages of proliferated CD4 (left panel) and CD8 (right panel) T cells (y-axes) after stimulation with preS peptides (P1–P8), preS or an equimolar peptide mix (x-axes) in blood samples of BM32-immunized subjects (n = 11) at time point M2. Results are means of triplicates in each patient, medians for all tested subjects are denoted by the horizontal lines. P1 (aa 2–31); P2 (aa 22–51); P3 (aa 42–71); P4 (aa 62–91); P5 (aa 82–111); P6 (aa 102–131); P7 (aa 122–151); P8 (aa 142–174).

Fig. 7

Inhibition of hepatitis B virus infection of in vitro infected HepG2-hNTCP cell lines (Ni et al., 2014) by BM32-induced antibodies. Intracellular staining of HBV core antigen (HBcAg: green) in cultured HepG2-hNTCP cells seven days after addition of (a) buffer (uninfected), HBV without or with the neutralizing antibody (Ma 18/7), (b) serum from rabbits before (pre) or after (post) immunization with Engerix-B or (c) BM32 (20 μg) or sera obtained at visits V5 and V15 from subjects immunized with (d) placebo, (e) 20 μg or (f) 40 μg of BM32. Bottom: Percentages of the inhibition (HBeAg secretion) of hepatitis B virus infection of cultured HepG2-hNTCP (x-axis) achieved by pre-incubation of virus with, Ma18/7, serum from a placebo-treated subject without prior HBV vaccination, sera from subjects after three (grey bars) or seven (black bars) immunizations with BM32 and sera from rabbits immunized with Engerix-B or BM32.