thymosin and Streptococcal-Infections

Thymosin β4 is a multifunctional protein in vertebrates that participates in physiological processes, such as wound healing, immune response, cell proliferation and migration. We assessed the multifarious roles of this small peptide in Pinctada fucata, an oyster commonly used in pearl culture in China. Our results showed that when P. fucata was challenged by bacterial pathogens or LPS, the relative expression level of Pfthymosin β4 mRNA was significantly up-regulated, suggesting its involvement in immune response of the animal. Recombinant Pfthymosin β4 (rPfthymosin β4) was produced and showed in vitro different antibacterial activities against different pathogenic bacteria; the inhibitory effect of rPfthymosin β4 on bacterial growth was relatively stronger in the broth culture than agar culture. The overexpression of Pfthymosin β4 in Escherichia coli BL21(DE3) cells could improve their resistance to Cu

Topics: Animals; Aquaculture; Fish Diseases; Lipopolysaccharides; Pinctada; Streptococcal Infections; Streptococcus agalactiae; Thymosin; Vibrio; Vibrio alginolyticus; Vibrio Infections

Thymosin beta belongs to the thymosin family, which consists of a series of highly conserved peptides involved in various biological processes. In teleosts, understanding of the immunological functions of thymosin beta is limited, particularly in vivo, which is essentially unknown. In the current study, we cloned and identified thymosin beta 4 from the teleost fish Golden pompano (Trachinotus ovatus), which we have named TroTβ4. We investigated the expression patterns and functions of TroTβ4 in both in vivo and in vitro assays. TroTβ4 is composed of 44 amino acids and shares high sequence identities with known thymosin β4 species in other teleosts, which contains a highly conserved actin-binding motif (LKKTET). The expression of TroTβ4 was most abundant in immune organs, and was significantly up-regulated in response to infection bacterial with one of a number of bacteria (including Edwardsiella tarda, Vibrio harveyi, and Streptococcus agalactiae). Purified recombinant TroTβ4 (rTroTβ4) inhibited the growth of bacteria, as measured using an automatic growth curve analyzer, indicating that TroTβ4 has antimicrobial functions. When administered in vivo, overexpression of TroTβ4 in T. ovatus, bacterial colonization of tissues was significantly reduced. In contrast, when a DNA vector-based siRNA technology was used to knock down TroTβ4 expression, bacterial dissemination and colonization of tissues increased significantly. Taken together, these results provide the first in vivo evidence to indicate that teleost thymosin beta 4 plays a significant role in innate antibacterial immune responses in addition to in vitro bacteriostatic activity. This provides valuable information regarding the biological functions of teleost thymosin beta.

Topics: Amino Acid Sequence; Animals; Base Sequence; Edwardsiella tarda; Enterobacteriaceae Infections; Fish Diseases; Fish Proteins; Immunity, Innate; Perciformes; Phylogeny; Sequence Alignment; Streptococcal Infections; Streptococcus agalactiae; Thymosin; Vibrio; Vibrio Infections

Apoptosis is characterized by a series of discrete biochemical events, among which is the truncation of the nuclear polypeptide prothymosin alpha (proTα) by activated caspase-3. This early apoptotic event results in the generation of a carboxy-terminal fragment of proTα, the immunoactive decapeptide proTα(100-109). We hypothesized that the detection of increased levels of proTα(100-109) in serum can be directly correlated with the induction of massive cell apoptosis, resulting from a severe bacterial infection. Thus, using high-affinity-purified polyclonal antibodies (Abs), raised in rabbits and a prototype antibody-capture system, we developed a highly sensitive and specific competitive ELISA for proTα(100-109). The sensitivity of the ELISA (0.1ng/mL to 10μg/mL) is acceptable for the quantification of the decapeptide in serum samples. To assess our initial hypothesis, we determined the concentration of proTα(100-109) in the sera of mice infected with the bacterium Streptococcus pyogenes over the course of the infection. We show that serum concentration of proTα(100-109) was marginal to undetectable before infection, increased over time and peaked at 72h postinfection. In silico analysis suggests that the Abs generated are unlikely to cross-react with any other unrelated mouse or bacterial protein. Further validation of our ELISA using serum samples from humans, infected with bacteria, may provide a useful tool to differentiate the causative agent of a potentially lethal septic infection.

Topics: Amino Acid Sequence; Animals; Antibody Specificity; Apoptosis; Computer Simulation; Enzyme-Linked Immunosorbent Assay; Epitopes; Humans; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Peptide Fragments; Protein Precursors; Rabbits; Streptococcal Infections; Streptococcus pyogenes; Thymosin