TAT-mediated oral subunit vaccine against white spot syndrome virus in crayfish

Determination of the efficacy of using a serine protease gene as a DNA vaccine to protect against Vibrio parahaemolyticus infection in Litopenaeus vannamei

Serine proteases are proteolytic enzymes that exhibit biological roles in many biological systems. Previously, a Vibrio parahaemolyticus serine protease was reported to be a virulence factor. Here, the serine protease gene of V. parahaemolyticus was investigated as a DNA vaccine against V. parahaemolyticus in Litopenaeus vannamei. The serine protease gene was mutated to replace the conserved residues His82, Asp131 and Ser231 with Gly, Asp and Pro, respectively. Then, a pcDNA3.1 vector to express mutVpSP (mutant serine protease) was constructed for in vitro and in vivo DNA vaccine investigation. In vivo mutVpSP transcriptional analysis revealed expression in various immunized white shrimp tissues, such as hemocytes, hepatopancreas, stomach, intestine, gills, and muscle. The efficiency of prevention of V. parahaemolyticus infection was investigated in vaccinated shrimp, and the lowest cumulative mortality percentage was 30%, while the control shrimp had a 60% cumulative mortality rate. The immune system was stimulated in shrimp vaccinated with the DNA vaccine. The mRNA expression of the shrimp immune-responsive genes phenoloxidase, peroxinectin and C-type lectin was significantly upregulated. Additionally, the humoral and cellular immune responses, including the PO, phagocytic, and encapsulation activities and nodule formation, were elevated. These results suggested that the serine protease could be a V. parahaemolyticus virulence determinant and that this DNA vaccine could be applied as an effective vaccine candidate for control of acute hepatopancreatic necrosis disease syndrome (AHPND) in shrimp.

Antigenic properties of VP15 from white spot syndrome virus in kuruma shrimp Marsupenaeus japonicus

White spot syndrome virus (WSSV) is known as one of the most lethal pathogenic viruses in shrimp causing massive damage to shrimp aquaculture industries. To date, no effective treatment or prevention has been found. In this study, five recombinant viral proteins VP15, VP19, VP24, VP26, and VP28 were expressed and purified in E. coli, which were employed as candidates against WSSV in Kuruma shrimp Marsupenaeus japonicus. In vivo antiviral assay in this study newly revealed that VP15 of major nucleocapsid protein, being known as a DNA-binding protein provided the substantial protection against the viral infection when pre-injected into shrimps. Furthermore, we also verified the immunogenic effects of purified VP15 and VP19 proteins produced in a silkworm-bacmid expression system. Taken together, our study identified VP15 as an effective candidate against WSSV infection in the Kuruma shrimp. It is interesting to uncover why and how VP15 is involved in the immune memory in shrimp in the future study.

Cell-penetrating Peptides: Efficient Vectors for Vaccine Delivery

Subunit vaccines are composed of pathogen fragments that, on their own, are generally poorly immunogenic. Therefore, the incorporation of an immunostimulating agent, e.g. adjuvant, into vaccine formulation is required. However, there are only a limited number of licenced adjuvants and their immunostimulating ability is often limited, while their toxicity can be substantial. To overcome these problems, a variety of vaccine delivery systems have been proposed. Most of them are designed to improve the stability of antigen in vivo and its delivery into immune cells. Cell-penetrating peptides (CPPs) are especially attractive component of antigen delivery systems as they have been widely used to enhance drug transport into the cells. Fusing or co-delivery of antigen with CPPs can enhance antigen uptake, processing and presentation by antigen presenting cells (APCs), which are the fundamental steps in initiating an immune response. This review describes the different mechanisms of CPP intercellular uptake and various CPP-based vaccine delivery strategies.

Meta-analysis of antiviral protection of white spot syndrome virus vaccine to the shrimp

Currently, white spot syndrome virus (WSSV) is one of the most serious pathogens that impacts shrimp farming around the world. A WSSV vaccine provides a significant protective benefit to the host shrimp. Although various types of vaccines against WSSV have emerged, the immune effects among them were not compared, and it remains unclear which type of vaccine has the strongest protective effect. Meanwhile, due to the lack of effective routes of administration and immunization programs, WSSV vaccines have been greatly limited in the actual shrimp farming. To answer these questions, this study conducted a comprehensive meta-analysis over dozens of studies and compared all types WSSV vaccines, which include sub-unit protein vaccines, whole virus inactivated vaccines, DNA vaccines and RNA-based vaccines. The results showed that the RNA-based vaccine had the highest protection rate over the other three types of vaccines. Among the various sub-unit protein vaccines, VP26 vaccine had the best protective effects than other sub-unit protein vaccines. Moreover, this study demonstrated that vaccines expressed in eukaryotic hosts had higher protection rates than that of prokaryotic systems. Among the three immunization modes (oral administration, immersion and injection) used in monovalent protein vaccines, oral administration had the highest protection rate. In natural conditions, shrimp are mostly infected by the virus orally. These results provide a guide for exploration of a novel WSSV vaccine and help facilitate the application of WSSV vaccines in shrimp farming.

What vaccination studies tell us about immunological memory within the innate immune system of cultured shrimp and crayfish

The possibility of immunological memory in invertebrates is a topic that has recently attracted a lot of attention. Today, even vertebrates are known to exhibit innate immune responses that show memory-like properties, and since these responses are triggered by cells that are involved in the innate immune system, it seems that immune specificity and immune memory do not necessarily require the presence of B cells and T cells after all. This kind of immune response has been called "immune priming" or "trained immunity". In this report, we review recent observations and our current understanding of immunological memory within the innate immune system in cultured shrimp and crayfish after vaccination with live vaccine, killed vaccine and subunit vaccines. We also discuss the possible mechanisms involved in this immune response.

Enhanced delivery of human growth hormone across cell membrane by Tat-PTD

In this study, we utilized the HIV protein Tat protein transduction domain (Tat-PTD) to enhance the intestinal absorption of recombinant human growth hormone (rhGH) delivered by oral administration. Insulin-like growth factor 1 (IGF-1), the key factor in the GH signal transduction pathway, was differentially affected at the mRNA level by various concentrations of rhGH. At high rhGH concentrations (500 ng/ml), IGF-1 was downregulated, while low concentrations (5 ng/ml) caused IGF-1 upregulation. The addition of Tat-PTD had a significant facilitating effect on rhGH. Frozen tissue sections visualized with fluorescence microscopy, cultured cells visualized by confocal microscopy and flow cytometry all confirmed that rhGH fused to Tat-PTD demonstrated more intracellular fluorescent signal when compared to rhGH alone. ELISA showed that after 2 h of incubation, Tat-rhGH levels in the rat intestinal cavity were 1.38-fold higher than rhGH. These data indicated that Tat-PTD effectively improved the internalization of rhGH and enhance the signal transduction of rhGH, possibly laying a solid foundation for the novel oral administration of rhGH.

Overexpression of a C-type lectin enhances bacterial resistance in red swamp crayfish Procambarus clarkii

C-type lectins play important roles in the innate immune system of crustaceans. In this study, a novel C-type lectin gene, designated as PcLec4, was obtained from the red swamp crayfish (Procambarus clarkii). Quantitative real-time polymerase chain reaction revealed that PcLec4 is mainly expressed in the crayfish hepatopancreas and intestine, and the PcLec4 mRNA expression is upregulated after challenged with the bacteria Vibrio anguillarum. PcLec4 was recombinantly expressed in Escherichia coli and anti-PcLec4 polyclonal antiserum was prepared. Binding experiments revealed that the recombinant PcLec4 binds to various bacteria and polysaccharides on the bacterial surface, which suggests that PcLec4 recognizes bacterial pathogens. Overexpression of PcLec4 in crayfish using the pIeLec4 vector was performed. The results show that the crayfish overexpressing PcLec4 eliminate injected V. anguillarum more quickly than the control, which suggests that PcLec4 elicits further immune response for removing invading bacteria. The results of the survival experiment confirmed the function of PcLec4 in resisting V. anguillarum because PcLec4 overexpression in crayfish significantly increased the crayfish survival rate. These results reveal that PcLec4 has an important role in the antibacterial immunity of crayfish, and in vivo PcLec4 overexpression might be used as a disease control strategy in aquiculture.