Moraxella catarrhalis outer membrane proteins, CD and ubiquitous surface protein A (UspA), were used as carriers for M. catarrhalis detoxified lipooligosaccharide (dLOS)-based conjugates. Our study was designed to investigate the feasibility of CD and UspA as protein carriers for dLOS-based conjugates and their possible synergic effects on protection from both anti-LOS and anti-CD or anti-UspA antibody responses. Female Balb/c mice were immunized subcutaneously three times with dLOS-CD or dLOS-UspA conjugate in Ribi adjuvant. Antisera elicited by the conjugates showed high titers of specific anti-LOS antibodies with complement-dependent bactericidal activity towards M. catarrhalis strain 25238. In a mouse aerosol challenge model, mice immunized with both conjugates showed a significant enhancement of the clearance of strain 25238 from lungs as compared with the control mice. Although both conjugates elicited reduced (relative to unconjugated CD or UspA) but significant levels of anti-CD or UspA antibodies, they did not show synergetic effects with anti-LOS antibodies on the bactericidal activity or the pulmonary bacterial clearance. Nevertheless, CD and UspA are safe and effective new carriers for dLOS-based or other potential carbohydrate-based conjugate vaccines to help thymus-independent carbohydrate antigens for production of anti-carbohydrate antibodies against target pathogens.
During the past two years, Weil-Felix agglutination tests and the typhus complement-fixation tests with purified rickettsial antigens have been used extensively in this laboratory in the serologic diagnosis of typhus fever. The complement-fixation test has been of great value because of its ability to differentiate between epidemic and murine typhus in non-vaccinated cases (1, 2, 3). Thus, in addition to its value to the clinician, the complement-fixation test has obvious significance to the epidemiologist. In fact, typhus surveys in Morocco, Egypt, Greece, Yugoslavia, Italy, Germany, Arabia, and other countries have been greatly aided by this test (4). In these studies, the complement-fixation test has maintained its specificity, and no false-positive reactions have been encountered (3). However, in view of the fact that epidemic typhus fever and relapsing fever epidemics repeatedly occur simultaneously, it was felt that it would be of value to extend these typhus tests to sera from cases of relapsing fever and to note whether or not false-positive or other interfering reactions occurred.
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