Lactic acid bacteria (LAB)
By Mehwish Manzoor

Contents...
• Lactic acid bacteria (LAB)
• Potential biomedical LAB applications
• LAB as Vaccines
• Steps of medical translation of live L. lactis-based
vaccines
• Benefits of LAB based Vaccines
• Future perspectives

Lactic acid bacteria (LAB)
• Represent a group of different gram-positive
microorganisms,
• non sporulating bacteria
• This group is distinguished by the ability to carry out
• fermentation of carbohydrates to form lactic acid
• Beneficial role played by these microorganisms in the
humans and other animals

Cont……..
• Present in many foods and are frequently used as
probiotics
• to improve some biological functions in the host

Lactic Acid Bacteria (LAB) or Lactics applications
• plants, meat, and dairy
• Dairy products - acidophilus milk, yogurt, buttermilk,
and cheeses
• The Lactics are also important commercially in the
processing of meats (sausage, cured hams), alcoholic
beverages (beer, fortified spirits), and vegetables
(pickles, and saukerkraut).

Potential biomedical LAB applications
• LAB as adjuvants,
• immunostimulators, or
• Therapeutic drug delivery systems
• Factories to produce therapeutic molecules

Why we choose LAB as vaccines?
• Lactobacillus genus, are able to colonise cavities
such as the mouth, the urogenital or the
gastrointestinal tracts, where they play a critical role
in maintaining a balanced normal micro flora •
Preventing or lowering the incidence or recurrent
urinary or digestive tract infections

Cont…..
• LAB are quite acid resistant and certain strains are
able to effectively survive passage through the
stomach
• • Absence of LPS in their cell wall virtually eliminates
the risk of
• endotoxic shock

Lactic acid bacteria (LAB)
• Important genera of (LAB) Lactococcus,
Lactobacillus, Leuconostoc, Streptococcus and
Pediococcus.
• Therapeutically used species L. acidophilus , L.
brevis, L. casei, L. bulgaricus and L. bifidus.

Exploitation of LAB
• Live vaccine or vaccine delivery vehicle
• The evolution of genetic engineering techniques
• Expressing heterologous proteins in different cellular
compartments
• improving their antigenic potential for the
production of vaccines against viruses, bacteria, and
parasites.

LAB as vaccine delivery vehicle
• The use of bacteria as vaccine delivery vehicles
implies construction of recombinant strains that
contain the gene cassette encoding the antigen
• Several genera of LAB are being tested as vaccine
delivery vehicles

Cont……
• Vaccines deliver vehicle
• Expresses an antigen from another species
• The vaccine component to be delivered can be
either protein or DNA
• Use of live viral or bacterial vectors for the
production of replicative particulate antigens in vivo

LAB as live vaccine
• As Live bacterial vaccines
• Designed to induce an immune response Itself
• To develop LAB as live vaccines, they have to be
genetically transformed

Recent developments
• Lactococcus lactis - Brucella abortis and Helicobacter
pylori
• Streptococcus gordonii prototype vaccines against
HIV and measles
• With Lactobacillus, prototype vaccines against
anthrax and rotavirus are under development, and
have already been obtained against tetanus

Benefits of LAB based Vaccines
• Eg: Lactococcus lactis
• Lactococcus lactis is a GRAS (generally regarded as
safe) bacterium that is widely used in the food
industry
• Intensive genetic and molecular research potential
new biomedical applications –vaccine delivery, –gene
delivery, –heterologous protein expression and –
therapeutic drug delivery

Future perspectives
• No or few lactococcal vaccine candidates are
currently under clinical investigation
• The use of biological containment strategies may be
necessary to prevent survival of genetically modified
vaccine strains in the environment
• The ultimate aim will be to develop environmentally
safe, multi-valent LAB vaccine vectors against a
variety of different pathogens