Efficacy of a polyvalent injectable vaccine against Flavobacterium psychrophilum administered to rainbow trout (Oncorhynchus mykiss L.)

Abstract

Flavobacterium psychrophilum is one of the most important pathogens affecting cultured rainbow trout (Oncorhynchus mykiss). Recent information from UK salmonid farms showed country‐wide distribution of genetically and serologically divergent clones, which has hampered the development of a vaccine for rainbow trout fry syndrome. The current study assessed the efficacy of an injectable polyvalent vaccine containing formalin‐inactivated F. psychrophilum in rainbow trout. The vaccine was formulated with an oil adjuvant (Montanide ISA 760VG) or formalin‐killed cells alone. Duplicate groups of trout (60 ± 13 g) were given phosphate‐buffered saline or vaccine formulated with Montanide by intra‐peritoneal (i.p.) injection and challenged by intra‐muscular (i.m.) injection with a homologous and a heterologous isolate of F. psychrophilum at 525 degree days post‐vaccination (dd pv). Significant protection was achieved in vaccinated fish (p = 0.0001, RPS 76% homologous, 88% heterologous). Efficacy of the adjuvanted vaccine was also demonstrated by heterologous challenge at 1155 dd pv resulting in 100% protection, whereas survival in the un‐adjuvanted group was not significantly different from control fish. Levels of specific antibody at 1155 dd pv, as measured by ELISA, were significantly higher in the fish vaccinated with adjuvant when compared with unvaccinated fish.

Plasma Proteome Responses in Salmonid Fish Following Immunization

“…An important part of the development pipeline is vaccine efficacy testing, which can be assessed directly via the extent of protection (e.g. using disease challenge tests), or indirectly, by studying changes in immune parameters, for example by confirming an antigen-specific antibody response ( 8 , 9 ) or recording changes in the expression of immune molecules (e.g. ( 10 , 11 )).…”

Assessment of immune responses in Indian major carp, Labeo rohita against multiple antigenic components of three bacterial fish pathogens; Aeromonas hydrophila , Pseudomonas aeruginosa and Staphylococcus aureus

“…Looking into the fact that it is not possible to immunize the fish with individual pathogens due to practical difficulties, stress factors and adverse reactions at injected area (Hastein et al, 2005), herein in this study attempt has been made to evaluate the immune response in fish to a multiple antigenic preparation containing whole‐cell Sa antigen and Pa antigen along with Ah ECP antigen. Researchers in the past have succeeded in developing polyvalent vaccine for different fish species including IMCs (Chandran et al, 2002; Hoare et al, 2018; Shoemaker et al, 2012; Silva et al, 2009; Swain et al, 2007; Zheng et al, 2012). In this study, multiple antigenic preparations consisting of Pa antigen, Sa antigen and Ah ECP antigen were immunized to assess the immunoresponses and the findings showed very promising results in terms of specific immune responses and non‐specific immune responses in L .…”

“…While specific antibody level against individual antigen was at par with that of individual antigen‐immunized groups, non‐specific parameters were mostly significantly higher ( p ≤ 0.05) than individual antigen‐immunized groups. Earlier, different several researchers have demonstrated significant antibody in various fish species using polyvalent vaccines (Hoare et al, 2018; Silva et al, 2009; Swain et al, 2007; Zheng et al, 2012). Significantly high antibody production against bivalent vaccine containing Streptococcus iniae and Vibrio vulnificus , response in hybrid tilapia, Oreochromis niloticus × Oreochromis aureus (Shoemaker et al, 2012), against trivalent whole‐cell antigens of A .…”

“…On the contrary, immunization strategy involving the multiple antigens can be useful to elicit immune responses thereby protecting against a wide range of pathogens and this may also reduce the cost of immunization and handling stress to fish. Recently, researchers have tried to develop polyvalent vaccines ranging from two to five antigens (Fredriksen et al, 2013; Hoare et al 2018; Nikoskelainen et al 2017; Shoemaker et al, 2012; Silva et al 2009; Swain et al, 2007; Zheng et al 2012). Most of these studies involved bacterial pathogens of Gram +ve and Gram −ve either one group or mixed group.…”

Salmonid Antibacterial Immunity: An Aquaculture Perspective

“…Similarly, it is believed that F. psychrophilum has both intracellular and extracellular aspects of its pathologic cycle, making vaccine development difficult [ 263 , 271 ]. Despite all that is unknown regarding F. psychrophilum , some promising vaccine candidates have been developed recently for BCWD [ 272 , 273 , 274 ], but these studies must be repeated and tested during natural outbreak/exposure conditions. For many bacterial pathogens, developing an effective vaccine or improving current formulations has required an understanding of the bacterial pathogenesis.…”