Parenteral vaccine delivery: From basic principles to new developments

Parenteral administration of vaccines has been a highly effective strategy for preventing and controlling infectious diseases. Parenteral vaccines are administered through routes other than the gastrointestinal tract, such as intramuscular, subcutaneous, or intradermal injections. These routes offer several advantages, including the rapid and efficient delivery of antigens to the immune system, induction of robust immune responses, and enhanced vaccine stability. Moreover, parenteral vaccines can be formulated with adjuvants to further enhance their immunogenicity. Recent advancements in parenteral vaccine development have focused on several key areas. First, there has been significant progress in the design and formulation of novel antigen delivery systems, such as liposomes, virus-like particles, and nanoparticle-based carriers. These systems offer improved antigen stability, controlled release, and targeted delivery to specific immune cells. Second, advances in recombinant DNA technology have enabled the production of highly purified and well-characterized antigens, improving the safety and efficacy of parenteral vaccines. Third, the development of novel adjuvants, including toll-like receptor agonists and nanoparticle-based adjuvants, has facilitated the modulation of immune responses and the induction of long-lasting immunity. However, parenteral vaccine development also faces several challenges. Vaccine formulation and stability are critical factors, as certain antigens may degrade or lose potency during storage and transportation. Additionally, the choice of adjuvants requires careful consideration, as they need to elicit robust immune responses without causing adverse reactions. Furthermore, the high cost and complex manufacturing processes associated with parenteral vaccines can limit their accessibility, particularly in resource-limited settings. This chapter provides an overview of parenteral vaccine development, highlighting recent advancements and addressing the challenges associated with this approach.<br/

Optimisation of batch culture conditions for cell-envelope-associated proteinase production from lactobacillus delbrueckii subsp. lactis ATCC® 7830™

Using a combination of conventional sequential techniques, the batch growth conditions for the production of cell-envelope-associated proteinases have for the first time been studied and optimised in Lactobacillus delbrueckii subsp. lactis 313 (ATCC 7830; LDL 313). Concentrations of inoculum (0.1 < X < 10 % vol/vol), agitation speed (0 < S < 200 rpm), varying incubation temperature (30 < T < 50 °C), starting pH (4.5 < pH < 7) and carbon/nitrogen ratio of production medium (0.2 < r < 5) had an individual effect on proteinase yield (p < 0.01). Optimal conditions for proteinase production included an initial pH of 6.0, 45 °C incubation temperature, 2 % (v/v) inoculum size of OD560 = 1, 150 rpm agitation speed, and growth medium carbon/nitrogen ratio of 1.0. Maximum proteinase activity obtained for whole cells was 0.99 U/ml after 8 h of incubation. The variables studied are very relevant due to their significance in improving the productivity of proteinase synthesis from LDL 313, under process and, likely, economic optimum conditions