Mucosal and Systemic Immune Responses Induced by Recombinant Lactobacillus spp. Expressing the Hemagglutinin of the Avian Influenza Virus H5N1

Abstract

To develop a safe, effective, and convenient vaccine for the prevention of highly pathogenic avian influenza (HPAI), we have successfully constructed two recombinant lactobacillus strains (LA4356-pH and DLD17-pH) that express the foreign HPAI virus protein hemagglutinin 1 (HA 1 ). The mucosal and systemic immune responses triggered by these two recombinant lactobacilli following oral administration to BALB/c mice were evaluated. The results showed that both LA4356-pH and DLD17-pH could significantly increase the specific anti-HA 1 IgA antibody level in the mucosa and the anti-HA 1 IgG level in serum, as well as stimulating the splenic lymphocyte proliferative reaction through increased expression of interleukin-4 (IL-4). Compared with LA4356-pH, DLD17-pH was more effective at inducing systemic and mucosal immune responses, with higher anti-HA 1 -specific IgA and IgG levels. Therefore, DLD17-pH could be a promising oral vaccine candidate against HPAI. Highly pathogenic avian influenza (HPAI) virus (H5N1) is a threat to the world's poultry industry. As a zoonotic agent, this virus also has the potential to cause a human pandemic (29). Current vaccination (by intramuscular immunization) against HPAI has succeeded in reducing morbidity and mortality in poultry. However, the intense stress caused by injection could hamper the animal's growth (34). Thus, many investigators are pursuing more convenient and economical avenues for construction of new vaccine candidates, such as recombinant subunit vaccines using baculovirus (28), plasmid DNA (3), or replication-incompetent adenovirus (rAd) (26, 27) vectors. The H5N1 strain can infect animals through their respiratory and intestinal tracts (10). Because there are many mucosa-associated lymphoid tissues underneath the epithelia of the respiratory and intestinal tracts, protective HPAI virus antigens may induce an effective mucosal immune response to prevent the invasion of HPAI virus if they can be transported easily to these tissues. Thus, developing mucosal vaccine candidates based on these considerations is a feasible strategy.Mucosal vaccines, which are administered mainly orally or intranasally, cause less stress in the animal and have been the subject of growing interest due to the advantages that they offer over conventional parenteral vaccines. The biggest advantage is the stimulation of mucosal immune responses (15,24). Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. These beneficial bacteria normally live in the digestive, urinary, and genital systems without causing disease. Their abilities to transit through the stomach intact and to associate closely with the intestinal epithelium, combined with their immunomodulatory properties, have made Lactobacillus spp. attractive candidates as live vehicles for the delivery of immunogens to the intestinal mucosa (6, 12). It was recently shown that specific Lactobacillus species can induce inflammatory responses against infection, increase IgA production, activate mo...

Oral immunization with recombinant hepatitis E virus antigen displayed on the Lactococcus lactis surface enhances ORF2-specific mucosal and systemic immune responses in mice

“…The collected bacteria pellets were washed three times with sterile phosphate-buffered saline (PBS), and the final pellets were resuspended in sterile PBS supplemented with 1% sucrose for oral immunization at an appropriate concentration [14]. Plate counts were performed for each inoculum to determine the number of CFU for administration.…”

“…However, there was an inevitable problem that needs to be pointed out-that the detectable levels of anti-ORF2 specific IgA and IgG were both low and kept short-term compared to relevant researches [14,15]. The major reasons are attributed to (i) low expression rate of the recombinant L. lactis NZ3900 resulted in adequate ORF2-antigen stimulation; (ii) weak colonization of the recombinant L. lactis NZ3900 in mice gut mucosa leads to shrinkage of duration of antigenic stimulation, and (iii) components of the recombinant L. lactis NZ3900 seem not competent enough to act as immunologic adjuvants.…”

Mucosally administered Lactobacillus surface-displayed influenza antigens (sM2 and HA2) with cholera toxin subunit A1 (CTA1) Induce broadly protective immune responses against divergent influenza subtypes

“…As live delivery vehicles for mucosal immunization, lactic acid bacteria (LAB) have excellent adjuvant properties (Stoeker et al, 2011;Thaiwong et al, 2014;Wang et al, 2012). The appendages on the bacterial surface are important component for the adhesion to the host epithelium and for influencing mucosal immune responses (van Baarlen et al, 2013;Tripathi et al, 2013).…”

Immune Responses Induced by Recombinant Bacillus Subtilis Expressing the Hemagglutinin Protein of H5N1 in chickens

“…and B.S.-HA was ultrasonicated. For immunodetection of the fusion proteins by western blotting13, mouse anti-HA (Abcam, USA), followed by HRP-conjugated goat anti-mouse IgG (Sigma, USA) were used. Then the blots were developed by enhanced chemiluminescence.…”