Protein-Based Vaccine Protect Against Piscirickettsia salmonis in Atlantic Salmon (Salmo salar)

An effective and economical vaccine against the Piscirickettsia salmonis pathogen is needed for sustainable salmon farming and to reduce disease-related economic losses. Consequently, the aquaculture industry urgently needs to investigate efficient prophylactic measures. Three protein-based vaccine prototypes against Piscirickettsia salmonis were prepared from a highly pathogenic Chilean isolate. Only one vaccine effectively protected Atlantic salmon (Salmo salar), in correlation with the induction of Piscirickettsia-specific IgM antibodies and a high induction of transcripts encoding pro-inflammatory cytokines (i.e., Il-1β and TNF-α). In addition, we studied the proteome fraction protein of P. salmonis strain Austral-005 using multidimensional protein identification technology. The analyzes identified 87 proteins of different subcellular origins, such as the cytoplasmic and membrane compartment, where many of them have virulence functions. The other two prototypes activated only the innate immune responses, but did not protect Salmo salar against P. salmonis. These results suggest that the knowledge of the formulation of vaccines based on P. salmonis proteins is useful as an effective therapy, this demonstrates the importance of the different research tools to improve the study of the different immune responses, resistance to diseases in the Atlantic salmon. We suggest that this vaccine can help prevent widespread infection by P. salmonis, in addition to being able to be used as a booster after a primary vaccine to maintain high levels of circulating protective antibodies, greatly helping to reduce the economic losses caused by the pathogen.

Identification of Cryptosporidium parvum oocyst/sporozoite antigens recognized by infected and hyperimmune lambs

The appearance, persistence and eventual decline of IgG, IgM and IgA antibodies recognizing Cryptosporidium parvum antigens were studied in naturally infected lambs using a Western blot technique, and the results compared with those obtained using sera from immunized lambs. There was an intense recognition of some low molecular weight proteins (15-17 kDa by IgG and IgA; 28-30 kDa by IgA, IgM and IgG) during the infection and early post-infection period. These peptides were not recognized after Days 45-60 of life. Some high molecular weight antigens (94 kDa) were weakly recognized on Day 15 but more intensely recognized from Day 30 onwards, persisting until at least Day 90. Antibody recognition of these C. parvum proteins could be an indicator of recent or past exposure to the parasite.

Serum antibody response in lambs naturally and experimentally infected with Cryptosporidium parvum

The immunoglobulin (IgG), IgM and IgA responses in Castellana-Manchega cross-bred colostrum-deprived and colostrum-fed lambs infected neonatally with Cryptosporidium parvum were measured using an enzyme-linked immunosorbent assay. A comparison of oocyst shedding and anti-C. parvum serum IgG levels in lambs suffering either natural or experimental infection was undertaken. Effects on the oocyst shedding and IgG levels of C. parvum rechallenge at 30 and 120 days of age in neonatally infected lambs were also evaluated. Anti-C. parvum immunoglobulin levels in colostrum-deprived animals peaked on Day 30 of life for IgG and on Day 15 for IgM and IgA. Lambs that received maternal colostrum showed elevated anti-C. parvum IgG, IgM and IgA levels at 3 days old indicating a transfer of colostral immunoglobulins. Experimentally infected lambs showed a IgG response similar to naturally infected lambs, suggesting that the serum IgG response is independent of the infective dose. Finally, lambs rechallenged at 30 and 120 days old did not show either appreciable oocyst shedding or any increase in their anti-C. parvum IgG levels when compared with prechallenged animals.

Cross-reactivity of polyclonal serum antibodies generated against Cryptosporidium parvum oocysts

Polyclonal antibodies raised against Cryptosporidium parvum oocysts were found to cross-react with Eimeria spp. oocyst antigens in an indirect immunofluorescence assay, and sera from Eimeria spp.-infected lambs reacted with some antigens from sonicated C. parvum oocysts (between 29 to 30 and 66 to 69 kDa) by Western blot (immunoblot). No cross-reaction was observed with cystozoites of Toxoplasma and Sarcocystis spp. These results show the existence of epitopes common to C. parvum and various Eimeria spp.