Table 3 Plasmid-based secretion of functional elements in Lactobacilli

Secreting vaccines for treating virus infection

L. plantarum NC8

Co-expressing hemagglutinin (HA) with the dendritic cell-targeting peptide (DCpep)

Plasmid-based

Inducing avian influenza virus-specific cell-mediated and humoral immune responses

Against H9N2 AIV

Improving the survival rate of AIV-infected mouse and chicken models by inducing robust immune responses

Mice and chicken challenged with H9N2 virus

[57]

L. casei ATCC 393

Co-expressing CSFV-specific cytotoxic T lymphocyte (CTL) epitope 290 and the VP2 antigen of PPV

Plasmid-based

Increasing the mucosal and systemic immune responses

Against CSFV and PPV

This engineered strain showed 86.7% effective protection for the CSFV-challenged pig

Pig challenged with

CSFV strain Shimen

[58]

L. casei ATCC 393

Secreting the VP2 protein of infectious pancreatic necrosis virus (IPNV)

Plasmid-based

Inducing local mucosal and systemic immune responses

Against IPNV

This recombinant strain induced more than 3-fold reduction in viral load compared to control group

Rainbow trout (Oncorhynchus mykiss) that intraperitoneally injected with IPNV

[59]

Secreting vaccine for treating parasite infection

L. casei Zhang

Expressing immunodominant surface protein P23 of C. parvum sporozoites

Plasmid-based

Inducing mucosal immune system to elicit serum immunoglobulin G (IgG)

and mucosal IgA

Against C. parvum

Increasing the secretion of immunity factors such as IgA, IL6, and IFN-γ

BALB/c mice

[60]

Secreting vaccines for treating pathogens infection

L. casei ATCC 393

Expressing F4 (K88) fimbrial adhesin FaeG

Plasmid-based

Inducing effective fimbriae-specific mucosal and systemic immune responses

Against enterotoxigenic Escherichia coli (ETEC) infection

Using LTAK63 and LTB as oral adjuvant, this engineered strain exhibited 100% protection against ETEC challenge and developed mild diarrhea for 2–3 days

SPF BALB/c mice challenged with F4 + ETEC strain CVCC 230

[61]

L. acidophilus NCFM

Secreting the protective antigen (PA) of B. anthracis that genetically fused to a DC-binding peptide (DCpep)

Plasmid-based

Inducing PA-neutralizing antibody and T-cell mediated immune responses

Against B. anthracis infection

Increasing the survival rate of B. anthracis-infected mice from 0–100%

A/J mice challenged with B. anthracis Sterne pXO1⁺/pXO2⁻

[62]

L. reuteri 3630 and 3632

Secreting the nanobodies against NetB and α toxin of C. perfringens

Plasmid-based

Neutralizing NetB and α toxin of C. perfringens

Against necrotic enteritis

Protecting the chickens from necrotic enteritis-associated mortality (1.7- to 2.6-fold reduction) and reducing the pathological scores by 2.5- to 3.6-fold

Chickens challenged with Eimeria maxima and C. perfringens

[63]

Secreting vaccines for treating neurodegeneration disease

L. lactis subsp. cremoris MG1363

Expressing human p62 protein

Plasmid-based

Improving memory function, modulating of neuronal proteolysis, and decreasing AD typical signs

Against Alzheimer’s disease (AD)

The Aβ(1–42) peptide level was decreased by 42%; The activities of proteasome T-L and branched-chain amino acid preferring (BrAAP) were inhibited by 70% and 50%, respectively; The levels of protein oxidation products (3-NT and carbocyanine) were decreased by 1.37- to 1.78-fold; The levels of lipid peroxidation product (4-HNE) was decreased by 65%; The expression of anti-inflammatory cytokine (IL-10) was upregulated by 3-fold; The expression of pro-inflammatory cytokines (e.g., INF-γ, IL-1β, TNF-α, IL-2) were decreased by 2.0- to 3.25-fold

Triple transgenic mice 3xTg-AD

[65]

Secreting allergens for treating allergy

L. plantarum NCIMB8826 Int-1

Secreting the major birch pollen allergen Bet v 1

Plasmid-based

Decreasing allergen-specific IgE and increasing allergen-specific IgA at the mucosae

Against birch pollen allergy

This engineered strain could activate the Th1-type immune responses effectively in mice and reduce the production of IL-5 significantly

Aerosol challenges with a 1% birch pollen solution in female BALB/c mice

[66]

L. plantarum NCL21

Secreting the Japanese cedar pollen allergen Cry j 1 (Cry j 1-LAB)

Plasmid-based

Suppressing the allergen-specific IgE response and nasal symptoms

Against cedar pollinosis

Bringing 2-fold reduction for the allergen-specific IgE response

Female BALB/c mice immunized with Cry j 1/alum

[67]

Secreting antibodies

L. paracasei

Secreting the 3D8 single-chain variable fragment (scFv)

Plasmid-based

Hydrolyzing the nucleic acids of virus

Against avian influenza virus (AIV)

Decreasing virus shedding to protect the chickens from H9N2 infection

SPF chickens challenged with AIV

[68]

L. paracasei BL23

Secretion and surface display of TcdB-neutralizing antibody

Plasmid-based

Neutralizing the cytotoxic effect of the toxin B

Against C. difficile

Improving the survival rate of C. difficile spore-challenged hamsters from 0–50%

Hamsters challenged with spores of a TcdA⁻TcdB⁺ strain of C. difficile

[69]

Secreting pharmaceutical compounds

L. johnsonii FI9785

Exportation of bacteriophage endolysin CP25L

Plasmid-based

Lysing C. perfringens

Against C. perfringens

2- to 2.6-log less C. perfringens was observed in the coculture experiment

[70]

L. Reuteri 6475

Secreting murine interleukin-22 (IL-22)

Plasmid-based

Modulating the cytokines level in the serum and intestine

Against total body irradiation (TBI)

The survival rate of irradiation-treated mice was improved from 10–60% at day 30

C57BL/6NTac mice irradiated to 8.75 and 9.25 Gy

[71]

L reuteri 6475

Secreting murine interleukin-22 (IL-22)

Plasmid-based

Reducing the liver weight and triglycerides

Against fatty liver disease

22.3% decrease for liver weight ratio; 4.6-fold decrease for liver triglyceride

Male C57BL/6J mice with high-fat diet-induced obesity

[72]

L. reuteri 6475

Secreting murine interleukin-22 (IL-22)

Plasmid-based

Irradiation protection

Against alcoholic liver disease (ALD)

Increasing the expression level of Reg3g in small intestine, decreasing the level of Cxcl1 and Cxcl2 mRNAs, and reducing the bacteria translocation to liver

C57BL/6 mice with chronic and binge alcohol feeding (NIAAA)

[73]

L. plantarum NC8

Expressing angiotensin converting enzyme inhibitory peptide (ACEIPs)

Plasmid-based

Inhibiting angiotensin-converting enzyme (ACE)

Against hypertension

The SBP was decreased from 184.810 ± 4.305 mmHg to 167.111 ± 3.418 mmHg at day 15; The serum triglyceride was decreased from 1.213 ± 0.176 mM to 0.750 ± 0.181 mM

The spontaneously hypertensive rats (SHR)

[74]

L. reuteri 647

Secreting the Kv1.3 potassium blocker ShK-235

Plasmid-based

Blocking the Kv1.3 currents

Against rheumatoid arthritis

Reducing the mean score of arthritis from 25 ± 2 to 4 ± 1(84% reduction)

Rat model of rheumatoid arthritis

[75]

Secreting functional enzymes

L. plantarum WCFS1

Secreting the hydrolase domain of glycoside hydrolase PelA (PelAh) from P. aeruginosa

Plasmid-based

Degrading the biofilm of P. aeruginosa

Against P. aeruginosa

The cultures and supernatants of this engineered strain exhibited 80% and 85% reduction in biofilm biomass of P. aeruginosa

[76]

L. paracasei F19

Expressing human N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD)

Plasmid-based

Anti-inflammation

Against ulcerative colitis (UC)

Decreasing the DAI score (71% reduction), spleen weight (62% reduction), colitis histopathological score (47% reduction), MPO activity (56% reduction), the colonic level of iNOS (80% reduction), COX-2 (75% reduction) and IL-1β (63% reduction), the plasma level of NO (79% reduction), PGE2 (74% reduction), IL-1β (81% reduction) and TNF-α (86% reduction); Increasing the colon length (1.13-fold increment) and colonic expression of zonula occludens (ZO-1) (5.43-fold increment) and occluding (3.97-fold increment)

DSS-induced colitis mouse model

[77]

L. paracasei ATCC 27092

Secreting angiotensin converting enzyme 2 (ACE2) that fused with the non-toxic subunit B of cholera toxin

Plasmid-based

Reducing inflammation and oxidative stress by degrading Angiotensin II

Against diabetic retinopathy

Reducing the number of acellular capillaries, blocking the 20% retinal ganglion cell loss, and decreasing the expression of retinal inflammatory cytokines

STZ-induced diabetic eNOS^−/− mice and Akita mice

[78]

L. plantarum WCFS1

Secreting oxalate decarboxylase (OxdC)

Plasmid-based

Increased intestinal oxalate degradation

Against hyperoxaluria

Reducing serum uric acid (34% reduction), urinary oxalate excretion (40% reduction) and CaOx crystal deposition

Male wistar albino rats with hyperoxaluria

[79]

L. reuteri 100–23 C

Expressing phenylalanine lyase

Plasmid-based

Decreasing blood Phe concentrations

Against phenylketonuria (PKU)

PHA^enu2 mouse model of PKU

[80]

L. plantarum CM_PUJ411

Secreting the human phenylalanine hydroxylase (PAH)

Plasmid-based

Secreting PAH to transport through the cell monolayer of Caco-2 cells and decrease phenylalanine (Phe)

Against phenylketonuria (PKU)

Decreasing the Phe levels (28% reduction)

Caco-2 cells

[81]