Leukocyte populations and cytokine expression in the mammary gland in a mouse model of Streptococcus agalactiae mastitis

• Published in: Journal of medical microbiology Vol. 58; no. 7; pp. 951 - 958
• Main Authors: Trigo, Gabriela, Dinis, Marcia, Franca, Angela, Bonifacio Andrade, Elva, Gil da Costa, Rui M, Ferreira, Paula, Tavares, Delfina
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.07.2009; Society for General Microbiology
• Subjects: Animals; Antibodies, Bacterial; Bacterial diseases; Bacteriology; Biological and medical sciences; Cattle; Cytokines - genetics; Cytokines - metabolism; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Experimental bacterial diseases and models; Female; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - physiology; Infectious diseases; Leukocytes - metabolism; Mammary Glands, Animal - cytology; Mammary Glands, Animal - immunology; Mammary Glands, Animal - microbiology; Mammary Glands, Animal - pathology; Mastitis - immunology; Mastitis - microbiology; Mastitis - pathology; Medical sciences; Mice; Mice, Inbred BALB C; Microbiology; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Streptococcal Infections - immunology; Streptococcal Infections - microbiology; Streptococcus agalactiae; Time; Animal model; Mastitis; Microbiology; Leukocyte; Rodentia; Cytokine; Infection; Mammary gland diseases; Streptococcaceae; Vertebrata; Mammalia; Mouse; Streptococcal infection; Bacteriosis; Bacteria; Micrococcales; Mammary gland; Streptococcus agalactiae
• ISSN: 0022-2615; 1473-5644
• DOI: 10.1099/jmm.0.007385-0

1 Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal 2 Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal Correspondence Delfina Tavares dtavares{at}icbas.up.pt Received October 22, 2008 Accepted March 6, 2009 Streptococcus agalactiae is a contagious, mastitis-causing pathogen that is highly adapted to survive in the bovine mammary gland. This study used a BALB/c mouse model of Streptococcus agalactiae mastitis to evaluate leukocyte populations in regional lymph nodes and cytokine expression in the mammary gland involved in the immune response against Streptococcus agalactiae . It was found that the bacteria replicated efficiently in the mammary gland, peaking after 24 h and increasing by 100-fold. Dissemination of bacteria to systemic organs was observed 6 h after infection. At the same time, a massive infiltration of polymorphonuclear cells and an increase in the inflammatory cytokines interleukin (IL)-1 β , IL-6 and tumour necrosis factor- were detected in mammary glands, indicating an early inflammatory response. A decrease in the levels of inflammatory cytokines in mammary glands was observed 72 h after infection, accompanied by an increase in the levels of IL-12 and IL-10, which were related to a gradual decrease in bacterial load. An increase in the number of macrophages and B220 + lymphocytes and similar increases in both CD4 + and CD8 + T cells in regional lymph nodes were observed, being most pronounced 5 days after infection. Moreover, increased levels of anti- Streptococcus agalactiae antibodies in the mammary gland were observed 10 days after infection. Overall, these data suggest that the host exhibits both innate and acquired immune responses in response to Streptococcus agalactiae mastitis.