EXPERIMENTAL IMMUNIZATION AGAINST LYME BORRELIOSIS WITH RECOMBINANT OSP PROTEINS - AN OVERVIEW

Interest in human and veterinary vaccines against Lyme borreliosis is growing. Both whole cell immunization and subunit vaccines can protect against infection with Borrelia burgdorferi. For development of a hum an vaccine the focus has been on a subunit vaccine. The most promising candidate is OspA, a major outer membrane lipoprotein of B. burgdorfe ri sensu late. Of Osp proteins A through D, OspA shows the least varia bility between strains in its sequence and in the level of its express ion. Borreliae in ticks express OspA. Antibodies to OspA kill borrelia e in vitro and provide passive protection in mice. Active immunization of mice with OspA provides protection against challenge by syringe in oculation or tick bite, The lipid moiety of the OspA is necessary for immunogenicity in the absence of a potent adjuvant. A recombinant OspA -based vaccine is already in clinical trials. Although there is compel ling evidence that immunization with OspA will provide protection, que stions remain regarding the duration of protection from such immunizat ion, the necessity to have a minimum level of neutralizing antibodies at all times for protection, and the relationship of an immune respons e to OspA and autoimmune features of Lyme borreliosis, The experimenta l aspects of immunization with Osp-A based constructs and other Lyme v accine candidates are reviewed and discussed.