Hepatitis B Vaccine and Immunoglobulin: Key Concepts

Abstract

Hepatitis B virus (HBV) immunization is safe and has been accepted worldwide as a routine practice. The target of such vaccination is to induce the immune response in the host, resulting in the prevention of replication of HBV. There are several immunological and clinical factors which determine the clinical efficacy and safety of the HBV vaccine. In this article we have highlighted the response of the host immune system to HBV vaccination (immunogenicity), efficacy, and safety of the vaccine, issues with booster dosing, paths of development (preclinical and clinical) of the HBV vaccine, novel and upcoming strategies for improvement of HBV vaccination, and the concept of therapeutic HBV vaccination. The different aspects and regulatory recommendations pertaining to HBV vaccine development are also discussed. The new strategies for improvement of HBV vaccination include pre-S1 and pre-S2 portions of the HBV surface antigen, increasing the antigen dose, accelerated vaccination schedules, alternative vaccination route, use of adjuvants like immunostimulatory DNA sequences, etc. Therapeutic vaccination is being explored for initiation of a multifunctional and multispecific T cell response against the major HBV antigens and also effective activation of humoral immunity for viral control.

Keywords: Antibody; Development; Immune response; Immunoglobulin; Vaccine.

Fig. 1.. Schematic representation of the mechanism of action of HBV vaccine.

1. The injected HBV vaccine containing HBsAg proteins are engulfed and processed by the antigen presenting cells. 2. The antigen presenting cells process the antigen and attach the same to the surface of the antigen presenting cells. 3. The antigen presenting cells present the antigen to the T helper cells, leading to clonal expansion of the T cells as well as production of memory T cells. 4. The antigen can be recognized directly by B cells, producing a weak immune response, with binding of the antigen to the Fab region on the B cell receptor and secondary signaling from cytokines released by T-helper cells; B cells begin somatic hypermutation at the Fab region, which further increases the corresponding fit between the Fab region and the antigen. 5. The B cells mature to plasma cells to produce neutralizing antibodies. They also undergo clonal expansion and memory cell formation for future defense.