Cellular immune responses of pigs induced by vaccination with either a whole cell sonicate or pepsin-digested Brachyspira (Serpulina) hyodysenteriae bacterin W.R. Waters a, *, B.A. Pesch b , R. Hontecillas a , R.E. Sacco c , F.A. Zuckermann d , M.J. Wannemuehler a a Veterinary Medical Research Institute, Iowa State University, 1802 Elwood Drive, Ames, IA 50011, USA b US Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Metabolic Diseases and Immunology Unit, P.O. Box 70, Ames, IA 50010-0070, USA c US Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Avian and Swine Respiratory Diseases Unit, P.O. Box 70 Ames, IA 50010-0070, USA d Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, IL, USA Received 1 April 1999; received in revised form 20 May 1999; accepted 1 June 1999 Abstract Brachyspira (Serpulina) hyodysenteriae infection of pigs (swine dysentery) causes a mucohemorrhagic diarrhea resulting in signi®cant economic losses for producers. A commercial vaccine consisting of a proteinase-digested bacterin has shown ecacy in the reduction of disease due to B. hyodysenteriae. Vaccines consisting of whole cell bacterins, however, generally fail to protect pigs from disease. In the present study, cellular immune responses induced by a proteinase-digested bacterin were compared to responses induced by a whole cell sonicate antigen preparation. In addition, usage of either squalene or Freund's incomplete adjuvants in combination with each antigen preparation was also compared. Both antigen preparations induced signi®cant cellular immune responses as measured by in vitro (IFN-g production and T cell proliferation) and in vivo methods (DTH responses). No signi®cant dierences were detected in proliferative, interferon-g (IFN-g), or delayed type hypersensitivity (DTH) responses by pigs receiving either adjuvant or antigen preparation. T cells (CD3 + ) but not B cells from vaccinated animals proliferated in response to in vitro stimulation with B. hyodysenteriae antigen. CD8 + (single positive and CD4/CD8 double positive) and gd + T cells were particularly responsive. In addition, high percentages of both CD8 single positive and CD4/CD8 double positive cells were detected in antigen-stimulated cultures. These ®ndings demonstrate the unique sensitivity of porcine CD8 + T cells to priming for recall response by vaccination with a proteinase-digested B. hyodysenteriae bacterin. # 1999 Elsevier Science Ltd. All rights reserved. Keywords: Brachyspira (Serpulina) hyodysenteriae; CD8 + lymphocytes; gd T cells; Protease-digested vaccine 1. Introduction The etiologic agent of swine dysentery, Brachyspira (Serpulina) hyodysenteriae, is an aerotolerant, gram negative, anaerobic spirochete. Infection of pigs with B. hyodysenteriae induces a colitis without systemic spread of the organism. Pigs that have recovered from swine dysentery are protected from subsequent infec- tions [1]. Vaccines consisting of whole cell bacterins induce serum antibody responses to B. hyodysenteriae yet generally fail to protect pigs from disease. The use of B. hyodysenteriae bacterins prepared from whole cell lysates may even exacerbate disease upon infection [2]. However, proteinase-digested B. hyodysenteriae bacterins given intramuscularly are ecacious in redu- cing disease severity [3]. Proteinase digestion of B. hyo- Vaccine 18 (2000) 711±719 0264-410X/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0264-410X(99)00266-2 www.elsevier.com/locate/vaccine * Corresponding author. Tel.: +1-515-294-6842; fax: +1-515-294- 1401. E-mail address: wwaters@iastate.edu (W.R. Waters)