RESUMO

Single nucleotide polymorphisms (SNPs) are the best genetic markers for associative studies of the immune system in invertebrates. In the marine shrimp Litopenaeus vannamei, SNPs linked to disease resistance have been reported for some genes, such as hemocyanin, anti-lipopolysaccharide factor, and heat-shock protein 70 (Hsp70). In the present study, polymorphisms in the Hsp70 gene were investigated among three commercial L. vannamei populations bred in Northeast and South Brazil. The first population withstood a strong white spot disease outbreak; the second population suffered extended exposure to infectious myonecrosis; the third population was a high health population, which was experimentally infected with white spot syndrome virus (WSSV) in the present study. All five previously known SNPs (C661A, T712C, C782T, C892T, and C1090T) were detected in the coding region of Hsp70, by Sanger sequencing of 119 shrimp. Significant differences in genetic and genotype frequencies among populations were observed for C661A, C892T, and C1090T. In the population submitted to WSSV challenge, no frequency differences were found between dead and surviving shrimp groups. These results indicate that the Hsp70 polymorphisms described here cannot be associated with WSSV tolerance. However, significant frequency differences were observed for the population exposed to infectious myonecrosis virus. This is the first time that L. vannamei Hsp70 gene polymorphisms were studied in correlation with these important shrimp viruses.

Assuntos

RESUMO

The present study aimed to evaluate the mortality, reactive oxygen species production (ROS) and total hemocyte counts (THC) of the marine shrimp Litopenaeus vannamei infected with the white spot syndrome virus (WSSV) at three levels of oxygen saturation. For this, 360 shrimp (20±2g) were distributed in 24 tanks (60L), divided in two groups (infected and non-infected), which were subjected to 30, 60 and 100% of dissolved oxygen saturation (in quadruplicate). During 96 hours after infection, daily hemolymph samples were collected for hemato-immunological parameter evaluation (THC and ROS) and dead animals were removed and computed to assess cumulative mortality rates. In the infected group, animals subjected to 100% saturation showed higher ROS production (P<0.05) after 48 hours, while THC was significantly reduced (P<0.05), regardless of oxygen saturation. The hypoxia resulted in high mortality when compared to 100% saturation condition. In the uninfected group, no significant differences were observed in all evaluated parameters. Thus, the hypoxia condition increased the susceptibility of shrimp to the infection of WSSV, which may be partly related to the low ROS production showed by the animals subjected to 30% oxygen saturation.(AU)

O presente estudo teve por finalidade avaliar a mortalidade e a contagem total de hemócitos (CTH) e espécies reativas de oxigênio (EROs) de camarão Litopenaeus vannamei infectados com o vírus da mancha branca (WSSV) e submetidos a três níveis de saturação de oxigênio. Para tanto, 360 camarões (20±2g) foram distribuídos em 24 tanques (60L), divididos em dois grupos, infectados e não infectados e submetidos a 30, 60 e 100% de saturação de oxigênio (em quadruplicata). Após a infecção, diariamente foram coletadas amostras de hemolinfa dos animais para avaliação dos parâmetros hematoimunológicos (CTH e EROs) e foi estimada a mortalidade, por 96 horas. No grupo com infecção, os animais submetidos à saturação de 100% apresentaram um aumento na produção de EROs (P<0,05) após 48 horas, ao mesmo tempo em que a CTH demonstrou uma redução (P<0,05) independentemente da saturação do oxigênio, e a condição de hipóxia acarretou maiores mortalidades quando comparada à do grupo com 100% de saturação. No grupo sem infecção, não foram observadas diferenças significativas nos parâmetros avaliados nem mortalidade. Dessa forma, pode-se concluir que a hipóxia aumentou a susceptibilidade do camarão à infecção com o vírus da mancha branca, que pode estar, em parte, relacionada com a baixa contagem de hemócitos e produção de EROs observadas nos animais submetidos a essa condição.(AU)

Assuntos

RESUMO

The present study aimed to evaluate the mortality, reactive oxygen species production (ROS) and total hemocyte counts (THC) of the marine shrimp Litopenaeus vannamei infected with the white spot syndrome virus (WSSV) at three levels of oxygen saturation. For this, 360 shrimp (20±2g) were distributed in 24 tanks (60L), divided in two groups (infected and non-infected), which were subjected to 30, 60 and 100% of dissolved oxygen saturation (in quadruplicate). During 96 hours after infection, daily hemolymph samples were collected for hemato-immunological parameter evaluation (THC and ROS) and dead animals were removed and computed to assess cumulative mortality rates. In the infected group, animals subjected to 100% saturation showed higher ROS production (P<0.05) after 48 hours, while THC was significantly reduced (P<0.05), regardless of oxygen saturation. The hypoxia resulted in high mortality when compared to 100% saturation condition. In the uninfected group, no significant differences were observed in all evaluated parameters. Thus, the hypoxia condition increased the susceptibility of shrimp to the infection of WSSV, which may be partly related to the low ROS production showed by the animals subjected to 30% oxygen saturation.

O presente estudo teve por finalidade avaliar a mortalidade e a contagem total de hemócitos (CTH) e espécies reativas de oxigênio (EROs) de camarão Litopenaeus vannamei infectados com o vírus da mancha branca (WSSV) e submetidos a três níveis de saturação de oxigênio. Para tanto, 360 camarões (20±2g) foram distribuídos em 24 tanques (60L), divididos em dois grupos, infectados e não infectados e submetidos a 30, 60 e 100% de saturação de oxigênio (em quadruplicata). Após a infecção, diariamente foram coletadas amostras de hemolinfa dos animais para avaliação dos parâmetros hematoimunológicos (CTH e EROs) e foi estimada a mortalidade, por 96 horas. No grupo com infecção, os animais submetidos à saturação de 100% apresentaram um aumento na produção de EROs (P<0,05) após 48 horas, ao mesmo tempo em que a CTH demonstrou uma redução (P<0,05) independentemente da saturação do oxigênio, e a condição de hipóxia acarretou maiores mortalidades quando comparada à do grupo com 100% de saturação. No grupo sem infecção, não foram observadas diferenças significativas nos parâmetros avaliados nem mortalidade. Dessa forma, pode-se concluir que a hipóxia aumentou a susceptibilidade do camarão à infecção com o vírus da mancha branca, que pode estar, em parte, relacionada com a baixa contagem de hemócitos e produção de EROs observadas nos animais submetidos a essa condição.

Assuntos

RESUMO

In the present study we investigated the proPO activating system of the penaeid Penaeus paulensis, focusing on its role in the shrimp immune system. The great majority of PO activity (more than 90%) was found in the shrimp hemocytes. The enzyme activity was greatly enhanced by components of microorganism cell walls, such as LPS and beta-1,3-glucans, suggesting its involvement in non-self recognition. PO activity was also found in the shrimp serum and trypsin, and LPS were able to increase the enzyme activity. Thus, serum can be used as an alternative for the study of the shrimp proPO activating system, as it is much more readily obtained than HLS. PO activity was cation-dependent, and 5 mM of calcium and 10 mM of magnesium were the optimal concentrations for the enzyme activity. An immune factor was found in the shrimp HLS, capable of inducing cell-adhesion and degranulation of the penaeid hemocytes.

Assuntos