Effect of Peptidoglycan–Polysaccharide Complex on Reproductive Efficiency in Sheep INTRODUCTION Early embryonic mortality accounts for most preg- nancy losses in many mammalian species (20–30% in cows, 1–3 sheep, 4,5 and goats, 5 5–40% in rodents, 6 10– 20% in primates 7–9 ). For enhanced profitability, dairy cows must be pregnant within 90 days after partur- ition, 10 which means they must be inseminated during peak lactation when metabolic demand is high. Maternal disease during early embryonic development can adversely affect survival of the embryo. Contrac- tion of mastitis, an inflammation of the mammary gland, shortly after artificial insemination, but not before insemination or later in pregnancy, decreased conception rate in Jersey cows. 11 Hence, infection with mastitis-causing pathogens between fertilization and placentation might be a critical factor for loss of pregnancy. Two toxic components of bacteria, lipopolysaccha- ride (LPS) and peptidoglycan (PG; synonyms: glyco- peptide, mucopeptide, or murein), have been used to delineate the link between infection, such as mastitis, and early embryonic failure. Pregnancy rate in sheep was reduced after administration of 30 or 60 lg/kg of PG on day 5 after breeding. 12 The biologic attributes of PG are: it is a main immunogenic component of the cell wall of gram-positive bacteria, 13–15 a macrophage and complement activator, 14 as well as a B-cell mitogen. 16 For these and additional reasons, PG is responsible for many clinical manifestations including inflammation, fever, leukocytosis, hypotension, decreased peripheral perfusion, malaise, sleepiness, and arthritis. 16,17 These physiologic effects are brought about by inflammatory mediators 17 produced by antigen presenting cells (APC) after PG binds to the Toll-like receptor-2 (TLR-2). 18 PG and LPS have similar biologic actions 19,20 and evoke common com- ponents of the NF-jB intracellular signaling pathway leading to secretion of inflammatory cytokines, such as tumor necrosis factor a (TNFa) in mononuclear phagocytes. 21 However, the PG-TLR-2 binding, with possible cooperation of TLR-2 and TLR-6, 18,22 American Journal of Reproductive Immunology AJRI 2004; 52: 197–203 Copyright Ó Blackwell Munksgaard, 2004 Hola´skova´ I, Lewis GS, Elliott M, Blemings KP, Dailey RA. Effect of peptidoglycan-polysaccharide complex on reproductive efficiency in sheep. AJRI 2004; 52:197–203 Ó Blackwell Munksgaard, 2004 PROBLEM: Spontaneous mastitis or induced infections mimicking mastitis reduce pregnancy rates in ruminants. The effect of immunization with either a mastitis-related pathogen component, peptidoglycan–polysaccharide (PG–PS), or killed Streptococcus pyogenes on pregnancy outcome was investigated. METHOD OF STUDY: Ewe lambs were immunized with PG–PS (n ¼ 50) or killed bacteria (n ¼ 50) or were not immunized (control, n ¼ 100). Titers of PG–PS immunoglobulin G (IgG) were detected by enzyme-linked immunosorbent assay (ELISA). Ewes were bred by rams at synchronized estrus. All immunized ewes and half of the ewes not immunized were challenged with PG–PS on day 5 after breeding. Pregnancy maintenance was evaluated. RESULTS: Although the proportion of ewes pregnant at day 42 after breeding did not differ among treatments, the probability of pregnancy decreased with total dose of PG–PS (P < 0.05). CONCLUSIONS: Immunization of ewe lambs with PG–PS or killed S. pyogenes did not improve pregnancy maintenance. Furthermore, the toxic streptococcal component decreased pregnancy rate in immunized sheep in a dose-dependent manner. Ida Holµskovµ 1 , Gregory S. Lewis 2 , Meenal Elliott 3 , Kenneth P. Blemings 1 , Robert A. Dailey 1 1 Division of Animal and Veterinary Sciences, West Virginia University, Morgantown, WV, USA; 2 USDA Sheep Experiment Station at Dubois, ID, USA; 3 Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, USA Key words: Fever, gram-positive bacteria, immunization, inflammation, mastitis, pregnancy Address reprint requests to Robert A. Dailey, Division of Animal and Veterinary Sciences, POB 6108, West Virginia University, Morgantown, WV 26506-6108, USA. E-mail: rdailey@wvu.edu Submitted December 8, 2003; revised June 10, 2004; accepted June 22, 2004. AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY VOL. 52, 2004