Priming with DNA Enhances Considerably the Immunogenicity of hCG β-LTB Vaccine

Prevention of nodules and enhancement of antibody response to genetically engineered recombinant vaccine against Human Chorionic Gonadotropin (hCG) for contraception

OBJECTIVE

Human Chorionic Gonadotropin (hCG) plays a crucial role in embryo implantation and in maintenance of pregnancy. An immuno-contraceptive approach involves the use of a recombinant hCGβ-LTB vaccine formulated with adjuvant Mycobacterium indicus pranii (MIP), to prevent pregnancy without disturbing ovulation, hormonal profiles, and menstrual cycles in women. The present work in mice was designed to address issues encountered in clinical trials conducted with hCGβ-LTB vaccine, with focus on two primary concerns. Firstly, it aimed to determine the optimal vaccine dosage required to induce a high level of anti-hCG antibodies. Secondly, it aimed to assess the safety profile of the vaccine, specifically injection site reactions in the form of nodules, observed in some of the subjects.

METHODS AND RESULTS

Studies undertaken indicate that a 2 µg dose of the protein version of the vaccine, administered in mice through the intramuscular route, can induce high anti-hCG titres. Furthermore, administering a booster dose enhances the antibody response. Our findings suggest that the concentration and frequency of administration of the adjuvant MIP can also be reduced without compromising vaccine efficacy.

CONCLUSION

The issue of nodule formation at the injection site can be mitigated either by administering the vaccine along with MIP intramuscularly or injecting hCG vaccine and MIP at separate intradermal sites. Thus, protein vaccine administered at a 2µg dose via the intramuscular route addresses both efficacy and safety concerns.

Bacterial production of recombinant contraceptive vaccine antigen from CatSper displayed on a human papilloma virus-like particle

CatSper is a voltage dependent calcium ion channel present in the principal piece of sperm tail. It plays a crucial role in sperm hyperactivated motility and so in fertilization. Extracellular loops of mouse sperm CatSper were used to develop a vaccine to achieve protection from pregnancy. These loops were inserted at one of the three hypervariable regions of Human Papilloma Virus (HPV) capsid protein (L1). Recombinant vaccines were expressed in E.coli as inclusion body (IB), purified, refolded and assembled into virus-like particles (VLP) in vitro, and adsorbed on alum. Four vaccine candidates were tested in Balb/C mice. All the constructs proved immunogenic, one showed contraceptive efficacy. This recombinant contraceptive vaccine is a non-hormonal intervention and is expected to give long-acting protection from undesired pregnancies.

Heterologous prime-boost immunization with live SPY1 and DnaJ protein of Streptococcus pneumoniae induces strong Th1 and Th17 cellular immune responses in mice

Streptococcus pneumoniae is a leading cause of infectious diseases in children under 5-year-old. Vaccine has been used as an indispensable strategy to prevent S. pneumoniae infection for more than 30 years. Our previous studies confirmed that mucosal immunization with live attenuated strain SPY1 can protect mice against nasopharyngeal colonization of S. pneumoniae and lethal pneumococcal infection, and the protective effects are comparable with those induced by commercially available 23-valent polysaccharide vaccine. However, live attenuated vaccine SPY1 needs four inoculations to get satisfactory protective effect, which may increase the risk of virulence recovery. It is reported that heterologous primeboost approach is more effective than homologous primeboost approach. In the present study, to decrease the doses of live SPY1 and improve the safety of SPY1 vaccine, we immunized mice with SPY1 and DnaJ protein alternately. Our results showed that heterologous prime-boost immunization with SPY1 and DnaJ protein could significantly reduce the colonization of S. pneumoniae in the respiratory tract of mice, and induce stronger Th1 and Th17 cellular immune responses than SPY1 alone. These results indicate heterologous prime-boost immunization method not only elicits better protective effect than SPY1 alone, but also reduces the doses of live SPY1 and decreases the risk of SPY1 vaccine. This work is the first time to study the protective efficiency with two different forms of S. pneumoniae candidate vaccine, and provides a new strategy for the development of S. pneumoniae vaccine.