0264-410X(95)00084-4 Vacnne, Vol. 13, No. 16, pp. 1576-1582, 1995 Copyright Q 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0264-410X/95 $lO+O.OO zyxwvuts Synthetic delivery system for tuberculosis vaccines: immunological evaluation of the M. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA tuberculosis 38 kDa protein entrapped in biodegradable PLG microparticles H.M. Vordermeier*, A.G.A. Coombest, P. Jenkins?, J.P. McGee-f-, D.T. O’Haganf, S.S. Davis? and M. Singhis zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Tuberculosis remains a major public health burden which could be ameliorated bl* eflective and well-defined subunit vaccines, particularly because the protective qJicacy of current M. bovis BCG vmcines is both unpredictable and variable. The iwwumodominant 38 kDa antigen from Mycobacterium tuberculosis was entrapped in biodegradable poly (DL- lactide co-glycolide) (PLG) microparticles ,\!hich served as a delivery system Both cellular and humoral immune responses were assessed and compared with those obtained after immunization with the 38 kDa protein emulsl$ed in incomplete Freund’s adjuvant (IFA). Vaccinution of mice with a single dose sf antigen-loaded microparticles resulted in specljic IgG titres peaking after zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA five weeks comparable to those achieved after vaccination with protein emulsified in incomplete Freund’s adjuvant (IFA). T-cell responses were found to be superior to those induced with antigenlIFA. The T- and B-cell epitope specljicities as judged with synthetic peptides ii’ere identical following immunization M’ith antigen in microparticles or IFA. DifSerences in udjuvanticit_v Ioere revealed bl’ measuring untigen-specific IgGl. IgG2a and antigen-induced IFN-y secretion in vitro: substantially higher titres of IgG2a )j’ere observed following immunization Ic>ith antigenlmicroparticles than with 38 kDa proteinlIFA. This was pnrnlleled bjl a tenfold higher secretion of IFN-y in mice injected with antigenhnicropnrtices. Reduction in colony:fonning units ups not consistent in mice inmuni-_ed Il’ith 38 kDa protein entrapped in microparticles ,i>hich bl’ere subsequently infected with live tubercle bacilli, Taken together these results indicate that biodegradable PLG microparticles constitute a ~f~wourable candidate vaccine delivery system worthy qf further assessment in the quest to develop better nnd dtlfined agents protecting against tuberculosis. Keywords: Tuberculosis: vaccine: 38 kDa antigen: microparticles: delivery system Tuberculosis still represents a major health problem, particularly in developing countries, with C(I. 8 million new cases worldwide in 1992 resulting in the death of CO. 2.7 million people’. This situation is further aggravated by the advent of the AIDS pandemic, where. especially in Africa, tuberculosis is strongly associated with HIV *MRC Clinical Sciences Centre, Tuberculosis and Related Infections Unit, Hammersmith Hospital, London WI.2 ONN, UK. tDepartment of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. SGBF, Department of Gene Expression, Braunschweig, Germany. $To whom correspondence should be addressed. (Received 6 January 1995; revised 24 April 1995; accepted 27 April 1995) infection. In addition, the recent emergence of multidrug- resistant strains of Mycobacteriurn tuberculosis imposes further constraints on the treatment of tuberculosis2. The protective efficacy of current M. bovis BCG vaccines is both unpredictable and variable ranging from virtually no protection to almost complete protec- tion depending on the vaccinated population studiedj. Hence, to improve vaccine efficiency, evaluation of new vaccine delivery systems based on liposomes or, as in this study, biodegradable microparticles composed of poly(DL lactide-co-glycolide) (PLG) used in conjunc- tion with defined recombinant M. tuberculosis antigens seems appropriate. Synthetic, biodegradable poly (a hydroxy acids) such as poly (DL-lactide) (DL.PLA) and copolymers of 1576 Vaccine 1995 Volume 13 Number 16