trehalosiorM. epitope onM. haemolyticaleukotoxin that is not present onB. trehalosileukotoxin. The mAb AM321 identified a non-neutralizing epitope shared from the leukotoxins ofB. trehalosiandM. haemolytica. The mAb AM113 should pave the way for mapping the leukotoxin-neutralizing epitope onB. trehalosileukotoxin and the development of subunit vaccines and/or virus-vectored vaccines against this economically important respiratory pathogen of ruminants. Keywords:Bibersteinia trehalosi,Mannheimia haemolytica, leukotoxin, neutralizing epitope == 1. Intro == Mannheimia haemolyticaandBibersteinia trehalosiare important pathogens of pneumonia in home and crazy ruminants worldwide [1,2,3].M. haemolyticaandB. trehalosiwere originally known asPasteurella haemolyticabiotype A andPasteurella haemolyticabiotype T of speciesPasteurella haemolyticaunder GenusPasteurellain the FamilyPasteurellaceae(Number 1).Pasteurella haemolyticabiotype A had 13 serotypes andPasteurella haemolyticabiotype T had 4 serotypes. Subsequently, in 1999, based on the results from DNA-DNA hybridization and 16S RNA studies, all serotypes KRX-0402 ofP. haemolticabiotype A were grouped under a newly produced GenusMannheimia[4]. All serotypes becameMannheimia haemolyticaexcept A11 which becameMannheimia glucosida. All four serotypes ofPasteurella haemolyticabiotype T were named asPasteurella trehalosiunder GenusPasteurella. Further taxonomical analysis in 2007 resulted in the creation of a new Genus,Bibersteinia, under which all fourPasteurella trehalosiserotypes were placed asBibersteinia trehalosi[5]. == Number 1. == Earlier and current taxonomical classification ofBibersteinia trehalosiandMannheimia haemolytica. WhileM. haemolyticahas been the predominant pathogen of pneumonia in ruminants,B. trehalosiis growing as an important pathogen of ruminant pneumonia [6,7,8]. In conjunction with active viral illness and stress factors,M. haemolyticaandB. trehalosicause an acute fibrinonecrotic pleuropneumonia [9]. Both these organisms produce several virulence factors including the capsule, outer membrane proteins, adhesins, neuraminidase, lipopolysaccharide and leukotoxin (Lkt) [10]. Lkt is definitely a 102 kD protein made up of 953 amino acids. Based on the observation that Lkt-deletion mutants cause no mortality [11] or reduced mortality and milder lung lesions [12,13] than the wild-type organisms, Lkt is approved as the most important virulence element of these organisms. Lkt belongs to the family of RTX (repeats in toxins) toxins and shares considerable homology with the exotoxins produced byEscherichia coli[14],Actinobacillus pleuropneumoniae[15], andActinobacillus actinomycetemcomitans[16]. However, cytolytic activity of Lkt is definitely specific for ruminant leukocytes [17,18]. Although all subsets of leukocytes are susceptible to the cytolytic effects of Lkt, polymorphonuclear cells (PMNs) are the most vulnerable subset [19]. Lkt-induced PMN lysis and degranulation are the primary causes of acute swelling and lung injury characteristic of this disease [20,21,22]. Lkt-neutralizing antibodies present protection against challenge with wild-typeM. haemolytica[23,24]. Hence vaccines against this organism consist of Lkt as the primary component [25,26]. While the Lkt ofM. haemolyticahas been analyzed extensively [22,27,28,29], characterization ofB. trehalosiLkt offers lagged behind. As the first step towards dealing with this problem, we developed KRX-0402 monoclonal antibodies against the Lkt ofB. trehalosiand used them to characterize the Lkt epitopes. Although all serotypes ofB. trehalosican cause respiratory disease in ruminants, serotype T10 has been generally isolated from pneumonic lungs of sheep and cattle. Similarly, while all serotypes ofM. haemolyticacan cause respiratory disease in ruminants, serotype A1 mainly causes pneumonia in cattle, while serotype A2 is the common cause of pneumonia in home and crazy sheep [21]. Therefore, with this study we focused on the Lkts ofB. trehalosiserotype T10 andM. haemolyticaserotype A1 and Rabbit Polyclonal to SH2D2A serotype A2. == 2. Results and Conversation == == 2.1. Monoclonal Antibody AM113 Reacts Only with B. trehalosi Lkt While AM 321 Reacts with Lkts of B. trehalosi and M. haemolytica == KRX-0402 A total of 304 hybridoma clones were from two self-employed fusions. To simplify the screening process, culture fluids from these clones were first tested by ELISA on plates coated with a mixture of Lkts ofB. trehalosiandM. haemolytica. The clones that were positive by this ELISA were consequently tested by another ELISA on plates coated with Lkt ofB. trehalosiorM. haemolyticaserotype A1 or serotype A2. These two ELISAs recognized two positive clones. One of them secreted a mAb (AM113) that reacted only with the Lkt ofB. trehalosiwhile the additional one (AM321) reacted with Lkts ofB. trehalosiandM. haemolyticaserotypes A1 and A2 (data not demonstrated). == 2.2. Western Blot Analysis Confirms the Specificity of mAbs AM113 and AM321 == Western blot analysis of mAbs AM113 and AM321 with Lkts ofB. trehalosiandM. haemolyticarevealed that mAb AM113 reacts only withB. trehalosiLkt, while AM321 reacts with Lkts ofB. trehalosiandM. haemolyticaserotypes A1 and A2, confirming the results of ELISA (Number 2). Both mAbs reacted with an approximately 100.