Abstract
Lactic acid bacteria (LAB) are a diverse group of Gram-positive, nonsporulating, low G + C content bacteria. Many of them have been given generally regarded as safe status. Over the past two decades, intensive genetic and molecular research carried out on LAB, mainly Lactococcus lactis and some species of the Lactobacillus genus, has revealed new, potential biomedical LAB applications, including the use of LAB as adjuvants, immunostimulators, or therapeutic drug delivery systems, or as factories to produce therapeutic molecules. LAB enable immunization via the mucosal route, which increases effectiveness against pathogens that use the mucosa as the major route of entry into the human body. In this review, we concentrate on the encouraging application of Lactococcus and Lactobacillus genera for the development of live mucosal vaccines. First, we present the progress that has recently been made in the field of developing tools for LAB genetic manipulations, which has resulted in the successful expression of many bacterial, parasitic, and viral antigens in LAB strains. Next, we discuss the factors influencing the efficacy of the constructed vaccine prototypes that have been tested in various animal models. Apart from the research focused on an application of live LABs as carriers of foreign antigens, a lot of work has been recently done on the potential usage of nonliving, nonrecombinant L. lactis designated as Gram-positive enhancer matrix (GEM), as a delivery system for mucosal vaccination. The advantages and disadvantages of both strategies are also presented.
Highlights
Lactic acid bacteria (LAB) are a diverse group of Gram-positive, nonsporulating, low G+C content bacteria
Many LAB have received generally regarded as safe (GRAS) status from the American Food and Drug Administration (FDA), but it is worthwhile to mention that pathogenic bacteria such as Streptococcus pyogenes and Streptococcus pneumonia belong to this group (Daniel et al 2011)
Some species are recognized as probiotics, which—according to the definition proposed by the World Health Organization (WHO)—confer a health benefit on the host when administered in adequate amounts
Summary
Lactic acid bacteria (LAB) are Gram-positive, nonsporulating bacteria, with low-GC content genomes. A number of different systems for the expression of genes encoding heterologous proteins in the cells of L. lactis were developed using both constitutive and inducible promoters. In studies aimed at examining the potential application of LAB in immunoprophylaxis, promoters induced under conditions prevailing in the immunized body are useful. One such expression system is stress inducible controlled expression system (SICE). Rapid research progress on the use of LAB for treatment and prophylaxis occurred at the turn of the twenty-first century In these studies, plasmid-cured strains of L. lactis subsp. Parameters affecting the immune response induced by prototypes of LAB vaccines will be discussed in a later part of this subsection
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