Oral Vaccination of Mice With Trichinella spiralis Putative Serine Protease and Murine Interleukin-4 DNA Delivered by Invasive Lactiplantibacillus plantarum Elicits Protective Immunity

Abstract

Trichinellosis is a serious zoonotic parasitic disease caused by Trichinella spiralis (T. spiralis) that causes considerable economic losses for the global pig breeding and food industries. As such, there is an urgent need for a vaccine that can prevent T. spiralis infection. Previous studies have reported that recombinant invasive Lactococcus lactis (LL) expressing Staphylococcus aureus fibronectin binding protein A (LL-FnBPA+) can transfer DNA vaccines directly to dendritic cells (DCs) across an epithelial cell monolayer, leading to significantly higher amounts of heterologous protein expression compared to non-invasive Lactococcus lactis. In this study, the invasive bacterium Lactiplantibacillus plantarum (L. plantarum) expressing FnBPA was used as a carrier to deliver a novel oral DNA vaccine consisting of T. spiralis adult putative serine protease (Ts-ADpsp) and murine interleukin (IL)-4 DNA to mouse intestinal epithelial cells. Experimental mice were orally immunized 3 times at 10-day intervals. At 10 days after the last vaccination, mice were challenged with 350 T. spiralis infective larvae by oral inoculation. Immunization with invasive L. plantarum harboring pValac-Ts-ADpsp/pSIP409-FnBPA induced the production of anti-Ts-ADpsp-specific IgG of serum, type 1 and 2 helper T cell cytokines of mesenteric lymph node (MLN) and spleen, secreted (s) IgA of intestinal lavage, and decreased T. spiralis burden and intestinal damage compared to immunization with non-invasive L. plantarum expressing Ts-ADpsp (pValac-Ts-ADpsp/pSIP409). Thus, invasive L. plantarum expressing FnBPA and IL-4 stimulates both mucosal and cellular immune response to protect against T. spiralis infection, highlighting its therapeutic potential as an effective DNA vaccine for trichinellosis.

Gastrointestinal worms and bacteria: From association to intervention

“…69 An alternative immunization strategy against T. spiralis consisted in the administration of recombinant L. plantarum expressing fibronectinbinding protein A from Staphylococcus aureus that confers lactobacilli the ability to effectively invade mammalian cells. [70][71][72] Invasive lactobacilli transformed with eukaryotic expression plasmids act as live bacterial vectors of exogenous DNA directly into host cells. 70…”

“…These protective effects were linked to enhanced local (IgA) and systemic (IgG) antibody responses against T . spiralis antigens, as well as increased production of Th1 and Th2 cytokines in the mesenteric lymph nodes and spleen of immunized mice post‐challenge infection 71,72 . Whilst, in both studies, vaccination with eukaryotic vectors coding for both T .…”

“…This observation suggests that the bacterial vector alone might assist the development of effective immune responses against T . spiralis 71,72 …”

“…Whilst, in both studies, vaccination with eukaryotic vectors coding for both T. spiralis antigens and mouse IL-4 was associated with the highest level of protection against infection, adult worm and larval burdens were significantly lower in mice treated with control invasive L. plantarum (i.e., transformed with empty vectors) compared to bacteria-unexposed mice. This observation suggests that the bacterial vector alone might assist the development of effective immune responses against T. spiralis 71,72.…”

“…Repeated oral immunization with transformed invasive L. plantarum coding for T. spiralis antigens-either alone or in combination with mouse IL-4-conferred partial protection against challenge Trichinella infection and resulted in reduced burdens of both adult worms and larvae. These protective effects were linked to enhanced local (IgA) and systemic (IgG) antibody responses against T. spiralis antigens, as well as increased production of Th1 and Th2 cytokines in the mesenteric lymph nodes and spleen of immunized mice post-challenge infection 71,72. Whilst, in both studies, vaccination with eukaryotic vectors coding for both T. spiralis antigens and mouse IL-4 was associated with the highest level of protection against infection, adult worm and larval burdens were significantly lower in mice treated with control invasive L. plantarum (i.e., transformed with empty vectors) compared to bacteria-unexposed mice.…”