Background/Objectives: Nocardia seriolae and Aeromonas veronii are two important pathogens that can affect a wide range of fish species and cause substantial economic losses. However, a vaccine that simultaneously protects fish from these two bacterial infections is not yet available. Methods: Three formalin-inactivated whole-cell vaccines prepared from N. seriolae and A. veronii (Monovalent Av, Monovalent Ns and Bivalent Av-Ns) were generated, and their efficacy was evaluated through a range of tests. The immune-related gene expression in the spleen and head kidney, enzyme activity, and specific antibody levels in serum were also detected. Results: All groups of vaccinated fish exhibited increased serum enzymatic activity compared with control fish, which peaked at week 3 after vaccination; in particular, that of the Bivalent Av-Ns group increased remarkably. The expression of immune-related genes in the spleen, head, and kidneys increased after immunization and were significantly enhanced (p < 0.05) in the bivalent vaccine group. Specific antibodies were produced at the 1st wpv, peaked at the 4th to the 5th wpv, and then decreased at the 6th wpv in all vaccinated groups. The Monovalent Av and Monovalent Ns against A. veronii and N. seriolae showed 56.67% and 22.22% RPS, respectively. Moreover, Bivalent Av-Ns offered 33.33% and 76.67% RPS for single infection with N. seriolae or A. veronii, as well as providing 44.44% RPS for dual infection with combined N. seriolae and A. veronii. Conclusions: Our findings indicate that the administration of the A. veronii and N. seriolae bivalent vaccine can protect largemouth bass from both bacterial infections.

With industrial development, endocrine-disrupting chemicals have continued to accumulate in the environment, attracting growing attention due to their potential effects on biological health. The reproductive toxicity of diethylstilbestrol (DES), a synthetic estrogen widely present in the environment, is widely documented; however, studies on its effects on the immune system remain limited. In this study, adult male golden hamsters were subcutaneously administered varying doses of DES (0, 0.01, 0.1, and 1.0 mg/kg) for seven consecutive days to assess its immunomodulatory impact on peripheral blood and the spleen. We found that the DES treatment significantly reduced spleen index, white pulp area, and splenic lymphocyte proliferation while increasing caspase-3-positive apoptotic cells and inducible nitric oxide synthase expression. In peripheral blood, DES induced a dose-dependent suppression of lymphocyte proliferation, with lipopolysaccharide- and concanavalin A-stimulated proliferation reduced by 47.68–71.76% and 44.23–72.7%, respectively. Concurrently, DES significantly downregulated the pro-inflammatory cytokines IL-2 and IFN-γ (p < 0.01) while upregulating the anti-inflammatory cytokines IL-4 and IL-10 (p < 0.01). Furthermore, DES treatment impaired antioxidant defenses, decreasing the activity of superoxide dismutase, glutathione peroxidase, and catalase while elevating malondialdehyde levels. Notably, DES led to the upregulation of G protein-coupled estrogen receptor and estrogen receptor α at both transcriptional and protein levels, whereas estrogen receptor β mRNA expression increased despite a decline in protein levels. This study provides critical experimental evidence elucidating the immunoregulatory effects of endocrine-disrupting environmental estrogens.

Due to the growing environmental burden of endocrine-disrupting chemicals (EDCs), there is an increasing concern regarding the reproductive hazards posed by synthetic estrogens, particularly diethylstilbestrol (DES). However, the precise mechanisms by which DES disrupts uterine endocrine function and immune homeostasis leading to pregnancy failure remain unclear. Given that wild rodents serve as key reservoirs for zoonotic diseases such as plague, reproductive interventions targeting their pregnancy processes hold significant ecological implications for disease control. In this study, female mice in estrus were randomly divided into four experimental groups, receiving DES at doses of 0 (control), 0.02 (low), 0.2 (medium), and 2 mg/kg (high), respectively. For five consecutive days, mice were injected subcutaneously on a daily basis, with the goal of examining DES-related alterations in hormone secretion and local immune responses within the uterus and spleen. It was found that high-dose DES treatment significantly increased maternal body weight and spleen weight during early pregnancy (p < 0.05). Meanwhile, reproductive function declined progressively with increasing doses, as indicated by decreased ovarian and uterine weights, fewer embryos, and extended estrous cycle duration (p < 0.05). Hematoxylin and eosin staining revealed that high-dose DES markedly reduced uterine gland density at day P5, accompanied by epithelial vacuolar degeneration and nuclear pyknosis. The proportion of uterine glands relative to total uterine area also decreased significantly with increasing DES doses. Moreover, DES inhibited lymphocyte proliferation in both the uterus and spleen in a dose-dependent fashion, with ConA- and LPS-induced proliferation rates decreasing by 0.78–30.70% and 1.91–18.20%, respectively (p < 0.05). The proinflammatory cytokine IL-2 was significantly elevated by DES, whereas the anti-inflammatory cytokine IL-4 showed a notable decrease (p < 0.05). DES administration notably decreased uterine expression of proliferating cell nuclear antigen. In contrast, the numbers of B-cell lymphoma 2- and Bcl-2-associated X protein-positive cells rose, along with upregulated levels of inducible nitric oxide synthase. Furthermore, DES impaired antioxidant defenses in both the uterus and spleen, evidenced by the decreased activities of superoxide dismutase and glutathione peroxidase, reduced total antioxidant capacity, and elevated malondialdehyde levels. This study elucidates the multifaceted mechanisms by which DES impairs the early gestational reproductive environment, filling a critical knowledge gap regarding its interference with the uterus–immune axis, and expands the current understanding of the ecotoxicological impacts of endocrine-disrupting chemicals.