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Research Project: Integrated Research to Improve Aquatic Animal Health in Warmwater Aquaculture

Location: Aquatic Animal Health Research

Title: Immunological and biochemical changes in Pacific white shrimp, Litopenaeus vannamei, challenged with Vibrio parahaemolyticus

Author
item Aksoy, Mediha
item Eljack, Rashida
item PEATMAN, ERIC - Auburn University
item Beck, Benjamin

Submitted to: Microbial Pathogenesis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2022
Publication Date: 9/17/2022
Citation: Aksoy, M., Eljack, R.M., Peatman, E., Beck, B.H. 2022. Immunological and biochemical changes in Pacific white shrimp, Litopenaeus vannamei, challenged with Vibrio parahaemolyticus. Microbial Pathogenesis. 172:105787. https://doi.org/10.1016/j.micpath.2022.105787.
DOI: https://doi.org/10.1016/j.micpath.2022.105787

Interpretive Summary: Acute hepatopancreatic necrosis disease (AHPND), a bacterial shrimp disease, has been causing global losses to the shrimp farming industry. Vibrio parahaemolyticus (Vpara) that naturally inhabits coastal waters is the causative agent of AHPND. As an invertebrate, shrimp lacks an adaptive immune system (also called acquired immunity) is activated by exposure to pathogen and uses an immunological memory to learn about the threat and enhance the immune response accordingly. They depend solely on innate immunity which attacks only based on the identification of general threats. To better understand the defense mechanisms of shrimp to this problematic pathogen, we evaluated the changes in hematology (study of blood), immunology and biochemical values of the hemolymph (invertebrate blood) from shrimp infected with V. parahaemolyticus up to 8 days. Thirty-six shrimp (12g) were distributed in 9 tanks (75L), divided into three groups (non-challenged, challenged with low dose and challenged with high dose) with three aquaria for each group. Pacific white shrimp, Litopenaeus vannamei, were administered an inoculum of bacteria (Vpara) under the shell between the 5th and 6th abdominal segment to assess immune responses. Total hemocyte count (THC, shrimp blood cells) significantly decreased in shrimp challenged with Vpara at 6h, 12h and 24h-post infection. Hemocyte lysate phenoloxidase (major defense system in many invertebrates) activity in Vpara-challenged shrimp at 48h post challenge was significantly increased compared to that of control shrimp. No significant differences were observed in total plasma protein between plasma from control and Vpara-challenged shrimp. However, shrimp challenged with low and high doses had significantly lower hemocyanin (copper-containing oxygen transporter protein in the hemolymph of invertebrates) at 6h and 48h sampling point, respectively. Plasma from Vpara-challenged shrimp at 6h and 12h-post infection significantly suppressed V. parahaemolyticus growth. The concentration of calcium did not differ between Vpara-challenged and control shrimp. Potassium level in the plasma of Vpara-challenged shrimp, however, increased at 6h and 12h post-infection sampling points. The changes observed in hemolymph parameters may be useful indicators of the health status of shrimp.

Technical Abstract: Vibrio parahaemolyticus (Vpara) the causative agent of Acute Hepatopancreatic Necrosis Disease (AHPND), or Early Mortality Syndrome (EMS), in shrimp. Shrimp, like other invertebrates, lack an adaptive immune system and depend solely on innate immunity against invading pathogens. To better understand the defense mechanisms of shrimp to this problematic pathogen, we evaluated the changes in hematology, immunology and biochemical values of the hemolymph from shrimp challenged with V. parahaemolyticus up to 8 days post-challenge. Thirty-six shrimp (12g) were distributed in 9 tanks (75L), divided into three groups (non-challenged, challenged with 5x102cfu/shrimp and challenged with 1x103cfu/shrimp) in triplicate. Pacific white shrimp, Litopenaeus vannamei, were administered an inoculum of V. parahaemolyticus under the shell between the 5th and 6th abdominal segment to assess cellular and humoral immune responses. Total hemocyte count (THC) significantly decreased in shrimp challenged with Vpara at 6h, 12h and 24h-post infection. Hemocyte lysate phenoloxidase (PO) activity in Vpara-challenged shrimp at 48h post challenge was significantly increased compared to that of control shrimp. No significant differences were observed in total plasma protein between plasma from control and Vpara-challenged shrimp. However, shrimp challenged with 5x102, and 1x103cfu/shrimp had significantly lower hemocyanin at 6h and 48h sampling point, respectively. At 24h post-challenge, the =140 kDa and 70kDa bands from SDS-PAGE of hemocyanin-concentrated hemolymph lysate samples showed a higher and lower intensity, respectively, in Vpara- challenged group than those of the control group. Plasma from Vpara-challenged shrimp at 6h and 12h-post infection significantly suppressed V. parahaemolyticus growth. The concentration of calcium did not differ between Vpara-challenged and control shrimp. Potassium level in the plasma of Vpara-challenged shrimp, however, increased at 6h and 12h post-infection sampling points. The changes observed in hemolymph parameters may be useful indicators of the health status of shrimp.