A new lymph node infection model for Streptococcus suis serotype 2 in pigs

Area of Science:

• Veterinary Microbiology
• Infectious Diseases
• Immunology

Background:

• Streptococcus suis (S. suis) is a significant invasive pathogen in pigs.
• Understanding S. suis pathogenesis is crucial for swine health.
• Existing models may not fully capture S. suis dissemination dynamics.

Purpose of the Study:

• To develop and validate a new lymph node infection model for S. suis serotype 2 in piglets.
• To investigate the dissemination patterns of S. suis following direct lymph node inoculation.
• To explore the role of the lymph node microenvironment in S. suis infection.

Main Methods:

• A novel model involving direct injection of S. suis serotype 2 (7 × 10³ CFU) into the left cervical lymph node of 5-week-old piglets.
• Clinical observation and reisolation of S. suis from various tissues post-infection.
• Immunohistochemical analysis to localize S. suis antigen within the lymph node.

Main Results:

• Seven of eight piglets developed clinical signs of disease.
• S. suis was consistently reisolated from the infected lymph node and other systemic sites.
• S. suis antigen was primarily detected within the lymph node sinus.

Conclusions:

• Direct lymph node infection with S. suis leads to rapid systemic dissemination in piglets.
• The lymph node sinus, particularly interactions with mononuclear phagocytic cells, is a key site for S. suis initial host interaction.
• This model provides valuable insights into S. suis pathogenesis and host-pathogen interactions within the lymphatic system.