Abstract

Background:
Frequent coronavirus (CoV) outbreaks in recent decades have raised global concerns regarding their impact on both public health and animal populations. Probiotics, particularly Bifidobacterium spp. and Lactobacillus spp., are known to exert immunomodulatory and hematological benefits that may enhance vaccine responses.

Aim:
This study aimed to evaluate the immunomodulatory and hematological effects of Bifidobacterium and Lactobacillus probiotics in a murine model subjected to canine coronavirus (CCV) vaccine induction.

Methods:
Twenty-four mice were randomly divided into four groups: control, CCV induction, CCV induction + isoprinosine, and CCV induction + probiotics. The CCV vaccine (60 mg/kg BW) was administered subcutaneously for seven days, while probiotics were given orally for 14 days. On day 15, blood samples were collected for hematological and immunological assessments, including leukocyte count, hemoglobin, lymphocytes, neutrophils, caspase-3 (Casp-3), and interferon-gamma (IFN-γ) levels. Lung and duodenum tissues were fixed in 10% neutral buffered formalin, embedded in paraffin, and sectioned for hematoxylin–eosin (H&E) staining. IHC staining for Caspase-3 and IFN-γ was performed using specific primary antibodies (Abcam, UK), followed by HRP-conjugated secondary antibodies and DAB chromogen development. The sections were counterstained with hematoxylin and examined under a light microscope at 40× magnification.

Results:
The probiotic-treated group showed significant improvements in hematological parameters (leukocytes, hemoglobin, lymphocytes, and neutrophils) as well as reduced Casp-3 levels and increased IFN-γ expression compared with the other groups (p < 0.05).
The T2 group exhibited reduced staining intensity in the mucosal and submucosal regions of the duodenum and alveolar structures of the lung, indicating downregulation of apoptosis and inflammation compared to the C+ and T1 groups.

Conclusion:
Probiotic supplementation with Bifidobacterium and Lactobacillus demonstrated beneficial immunomodulatory and hematological effects in a murine CCV vaccine model, supporting their potential role as adjuncts in enhancing coronavirus vaccination strategies.

Key words: Bifidobacterium; Canine coronavirus; Hematology; Isoprinosin; Probiotics.