Serum antibody titers against T10 surface antigens were determined by indirect ELISA

Serum antibody titers against T10 surface antigens were determined by indirect ELISA. antigens against were 1:160 and 1:4,000, respectively. Following intranasal challenge with A2 (1 105 CFU), all four control BHS died within 48 h. Necropsy revealed acute fibrinonecrotic pneumonia characteristic of infection. None of the vaccinated BHS died during the 8 weeks postchallenge observation period. Radiography at 3 weeks postchallenge revealed no lung lesions in two vaccinated BHS and moderate lesions in the other two, which resolved by 8 weeks postchallenge. These results indicate that if BHS can be induced to develop high titers of Lkt-neutralizing antibodies and antibodies to surface antigens, they are likely to survive challenge which is likely to reduce the BHS populace decline due to pneumonia. INTRODUCTION The Lannaconitine bighorn sheep (BHS; have been isolated from several pneumonia outbreaks, only has been shown to consistently cause fatal pneumonia in BHS under experimental conditions (4, 7, 9, 22). Virulence factors of include capsule, outer membrane proteins, neuraminidase, lipopolysaccharide, and a potent exotoxin called leukotoxin (Lkt), which is usually cytolytic to all subsets of ruminant leukocytes (3, 14). Based on the fact that Lkt deletion mutants cause no mortality in BHS (4) and lower mortality and moderate lung lesions in cattle (12, 19, 24), Lkt has been accepted as the major virulence factor of this organism. Although causes pneumonia in all ruminants, BHS are highly susceptible to this disease (4, 7, 9, 22). There are a number Lannaconitine of potential factors contributing to the apparent difference in susceptibility to pneumonia. Enhanced susceptibility of polymorphonuclear leukocytes (PMNs) from BHS to Lkt-induced cytolysis is one of the factors responsible for the higher susceptibility of BHS (20, 22), which underscores the importance of Lkt-neutralizing antibodies (Lkt-nAb) for protection of BHS against pneumonia. Vaccination studies in cattle have shown that antibodies against Lkt and surface antigens of confer protection against experimental challenge (13, 21) and that such antibodies can be induced by vaccination of cattle or BHS with log-phase culture supernatant fluid (1, 13, 16, 27). However, to date systematic analysis of the response of BHS to vaccination and subsequent challenge with has not been performed. Thus, unambiguous data around the role of antibodies in protection of BHS against pneumonia caused by are not available. Several pneumonia outbreaks have occurred in the recent past, resulting in the death of large numbers of BHS (17). Thus, there is a critical need for development of efficacious vaccines to protect BHS against pneumonia. This study represents an initial step in addressing this need. BHS are more susceptible to pneumonia than the related species of domestic sheep ([DS] and as commensal bacteria in the nasopharynx, DS carry mostly Lkt-positive strains while BHS carry Lkt-negative strains (23; S. Shanthalingam et al., unpublished data). It is very likely that because of the difference in Lkt expression levels by the strains inhabiting the nasopharynx of DS and BHS and the consequent difference in exposure to the Lannaconitine immune system, Lkt-nAb are present at much higher titers in DS than in BHS, where Lkt-nAb are present at negligibly low titers (11). We hypothesized that if BHS can be induced to develop high titers of antibodies to surface antigens and Lkt, they will withstand subsequent challenge with also was used in this vaccine because Lkt-positive has been shown to cause fatal pneumonia in BHS (R. P. Dassanayake et al., unpublished data). Therefore, the objective of this study was to determine whether repeated immunization with a multivalent culture supernatant vaccine would protect BHS against experimental challenge. MATERIALS AND METHODS Experimental animals. All experimental protocols were reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) at Washington State University (WSU) before the onset of the study. Eight (2-year-old) BHS from your hand-raised captive herd at WSU were divided into two groups of four each. At the onset of the experiment, all the animals were healthy and did Lannaconitine not have any history of respiratory disease. Nasal and pharyngeal swabs were collected to determine the presence of and in the nasopharynx before the onset of the study. Blood samples were collected to determine serum antibody titers against Lkt and surface antigens of and and in nasopharynx. Nasal and pharyngeal swabs Rabbit Polyclonal to SHIP1 were submitted to the Washington Animal Disease Diagnostic Laboratory (WADDL).