BACKGROUND: Despite the availability of effective conjugate vaccines, Haemophilus influenza (HI) and Haemophilus somnus (HS) still result in enormous global morbidity in both human and cattle. Vaccines failure to protect against different strains can lead to the spread of Hemophilus infections. The absence of various epitopes from Haemophilus strains in existing vaccines is one of their weaknesses. Therefore, selection of a conserved and common set of proteins in the invasive strains of HI and HS is essential for predicting epitopes as potential vaccine candidate. OBJECTIVES: The aim of this study was to design an effective polyepitopic vaccine against invasive HI and HS strains using in silico approaches. METHODS: First, the protein sequences were retrieved from the databases and were aligned to determine the conserved areas with the Clustal omega software. Then, B and T cell epitopes identification was done for OapA, OMP6, PD, D15, IgA1 Protease and TbpA proteins using various immunoinformatic servers. The high ranked epitopes were selected from mentioned proteins. The selected epitopes were fused together by appropriate linkers. This designed construct was analyzed for physicochemical and structural characteristics using related servers. RESULTS: 6 TCD4+ and 3 B cell epitopes were selected to design the final construct from 6 common proteins. The immunoinformatics analysis revealed that the designed polyepitopic peptide is a safe, soluble, hydrophilic and thermostable antigen that could be a potential vaccine. CONCLUSIONS: The polyepitopic construct can be considered as a vaccine candidate against Haemophilus.

Immunogenicity of the lipid A component of Haemophilus somnus lipooligosaccharide in cattle and mice was examined after purification, detoxification, and covalent conjugation to a protein carrier. After 2 inoculations, a substantial antibody response was induced in most cattle to lipid A and the protein carrier. To determine whether antibodies to lipid A would be protective, 5 X 10(7) colony-forming units of H somnus strain 649 were administered IV to endotoxin-responsive (C3H/HEN) mice. In one study, 8 of 13 C3H/HEN mice aborted when inoculated. In contrast, abortion did not result when mice were inoculated with the same dose of an isolate of H somnus normally found in the prepuce or with the rough mutant Escherichia coli J5. In addition, endotoxin-nonresponsive (C3H/HeJ) mice were significantly (P = 0.03) more resistant to abortion by strain 649 than were C3H/HeN mice, but inoculated C3H/HeN mice were only slightly more resistant to H somnus abortion, compared with control mice. Although a large antibody response to lipid A was detected, there was no significant difference in the immunized group between mice that aborted and mice that delivered normally. Thus, lipooligosaccharide and other properties of virulent H somnus strains may contribute to abortion in mice.

An immunoperoxidase technique was used to study the relationship between the necrotic lesions and causative bacteria found in lungs of 53 calves that had naturally acquired pneumonia. Four types of necrotic lesions were identified on the basis of morphologic characteristics as follows: type 1 had coagulation necrosis surrounded by a dense zone of numerous degenerated leukocytes; type 2 was similar to type 1, but the central area of the lesions was severely affected, had no alveolar architecture remaining, and was surrounded by a thin, sparse layer of degenerated leukocytes; type 3 had small swirling accumulation of degenerated leukocytes; and type 4 had necropurulent lesions resembling abscesses. By use of the immunoperoxidase technique, Pasteurella haemolytica serovar 1 antigen was confirmed to be associated with the necrotic lesions in many cases of type 1 and in some cases of types 2 and 3. Although some lesions were induced by other bacteria (Haemophilus somnus or Actinomyces pyogenes), the pneumonic lesions associated with P haemolytica could be differentiated from other pneumonic lesions in calves by use of the immunoperoxidase technique.

Haemophilus somnus, Mycoplasma bovis and Pasteurella multocida were responsible for respiratory diseases in bovine. Methods for identifying these bacteria had poor sensitivity and specificity. In this paper, PCR assays were applied for rapid identification of H. somnus, M. bovis, P. multocida B:2 and P. multocida capsular types. The specific PCR products were amplified from H. somnus, but not from other bacteria. Ten-fold diluted H. somnus were mixed with P. multocida and then the mixed cultures were inoculated on agar plates.