Bacillus subtilisspores expressing the VP28 antigen: a potential oral treatment to protectLitopenaeus vannameiagainst white spot syndrome

Abstract

The envelope protein VP28 of white spot syndrome virus (WSSV) is considered a candidate antigen for use in a potential vaccine to this important shrimp pathogen (the cause of white spot syndrome, WSS). Here, we used spores of Bacillus subtilis to display VP28 on the spore surface. Trials were conducted to evaluate their ability to protect shrimps against WSSV infection. The gene cotB-vp28 was integrated into the chromosome of the laboratory strain B. subtilis PY79, and expression of CotB-VP28 was detected by Western blotting and immunofluorescence. Expression of CotB-VP28 was equivalent to 1000 molecules per spore. PY79 and CotB-VP28 spores were mixed with pellets for feeding of whiteleg shrimps (Litopenaeus vannamei), followed by WSSV challenge. Superoxidase dismutase (SOD), phenoloxidase activities and mortality rates of the two shrimp groups were evaluated. Groups fed with PY79 and CotB-VP28 spores at day 7 had increased SOD activities of 29% and increased phenoloxidase activities of 15% and 33%, respectively, compared to those of the control group. Fourteen days postchallenge, 35% of vaccinated shrimps had died compared to 49% of those fed naked spores (PY79) and 66% untreated, unchallenged animals. These data suggest that spores expressing VP28 have potential as a prophylactic treatment of WSS.

Protection of Penaeus monodon against white spot syndrome by continuous oral administration of a low concentration of Bacillus subtilis spores expressing the VP28 antigen

“…) and whiteleg shrimps ( Litopeanus vanamei ) (Nguyen et al . ), similar levels of protection (46–50%) were reported for both shrimp species when challenged with WSSV by IM injection. With reference to the VP26 and VP28 antigens, Valdez et al .…”

“…) and 47% in whiteleg shrimps against WSSV (Nguyen et al . ). However, the protective efficacy of orally administered CotB‐VP28 spores in black tiger shrimps has not been studied.…”

“…This could be influenced by no change in PO and SOD activities when black tiger shrimps fed PY79 spores, meanwhile 15% increased PO and 49% increased SOD have been detected in whiteleg shrimps fed PY79 spores (Nguyen et al . ). In contrast to Untreated and PY79 groups, the CotB‐VP28 group showed slow feed consumption and death 2 days later compared to the Unchallenged and PY79 groups (day 4 post challenge).…”

“…) and CotB‐VP28 spores (Nguyen et al . ), and in F. chinensis following vaccination with B. subtilis vegetative cells expressing VP28 (Fu et al . ).…”

Progress in Bacillus subtilis Spore Surface Display Technology towards Environment, Vaccine Development, and Biocatalysis

“…Surface-displayed recombinant spores can be used as an oral vaccine, such as expressing the tetanus toxin fragment C of Clostridium tetani or heat labile toxin from Escherichia coli with serum IgG titters, which were used in a mouse parental model to induce an immunogenic response and are considered for oral administration [Mauriello et al, 2004]. The efficiency of a vaccine can also be increased to some extent as with VP28, the white spot syndrome virus envelope protein, which is considered to be an effective prophylactic vaccine against white shrimp white spot syndrome and shows a slight decrease in mortality rate up to 31% after being fed VP28-displayed spore-mixed tablets [Nguyen et al, 2014]. Recombinant B. subtilis spores has the ability to induce systemspecific and mucosal humoral immunity, and Zhou et al [2015] concluded higher amounts of IgG and IgA antibody titers against H. pylori antigen in the mice serum immunized with recombinant spores with urease B. subtilis spores are able to tolerate harsh environments and regrow after inactivation in most conditions.…”