Vaccine xxx (2005) xxx–xxx A novel synthetic adjuvant effectively enhances the immunogenicity of the influenza vaccine R. Segura-Vel´ azquez a , A. P´ erez-Torres b , G. Rosas c , A. Toledo a , M. Restelli d , E. Acosta a , R. Corral d , F. Rosetti b , G. Fragoso a , S. Grinstein d , E. Sciutto a,∗ a Instituto de Investigaciones Biom´ edicas, A.P. 70228, Ciudad Universitaria, 04510 M´ exico, D.F., M´ exico b Facultad de Medicina, UNAM, M´ exico, D.F., M´ exico c Facultad de Medicina, UAEM, Cuernavaca, M´ exico d Laboratorio de Virolog´ ıa, Hospital del Ni ˜ no Ricardo Guti´ errez, Buenos Aires, Argentina Received 9 June 2005; received in revised form 25 August 2005; accepted 5 September 2005 Abstract Influenza vaccination is a key intervention to reduce morbidity and mortality provoked by this disease. To date, the challenge of improving its efficacy remains unmet. The immunogenic synthetic peptide GK1 from Taenia crassiceps cysticerci was tested herein in its capacity as adjuvant, co-administered with the inactivated anti-influenza vaccine before and after challenge with influenza virus in both young and aged mice. Co-administration of GK1 with the influenza vaccine increased levels of anti-influenza antibodies in aged mice before and after infection, reduced the local inflammation that accompanied influenza vaccination itself and favored virus clearance after infection in both young and aged mice. © 2005 Elsevier Ltd. All rights reserved. Keywords: Influenza vaccine; Adjuvant; GK-1 1. Introduction Senescence of the immune system is reflected at different levels, e.g. defects in the expression of pattern-recognition co-stimulatory molecules in antigen-presenting cells, dereg- ulation of nitric oxide (NO) and cytokine production, and altered balance of memory CD4+ T cells [1–3]. This decline must be related to the impaired immunity conferred by infec- tion or vaccination as age advances [4–6]. Global rise of the aging population also causes an increase in the need to improve immunity of the elderly, e.g. the UK govern- ment’s actuary department has forecasted that 20% of the population will be >65 years of age. This makes it of spe- cial relevance to overcome the low vaccine efficacy against different pathogens. ∗ Corresponding author. Tel.: +52 55 5622 3153; fax: +52 55 5622 3369. E-mail address: edda@servidor.unam.mx (E. Sciutto). Influenza is an acute febrile respiratory disease that rep- resents a health problem responsible for thousands of yearly hospitalization and deaths [7]. In this context, an improve- ment in the response to influenza vaccination is one of the clearest needs considering the low response of the elderly compared to younger adults. Thus, enormous efforts are cur- rently under way in order to improve the influenza vaccine [8]. Several novel strategies, including the use of immunomodu- lators such as adjuvants, may overcome some of the defects of aging immunity [9], since they are more effective in priming the cellular and humoral responses. The oil-in-water adjuvant emulsion MF59 may significantly improve vaccine immunity [10,11]. MF59 is the most extensively explored and recently approved adjuvant to be used in humans, albeit it does not completely solve the low efficiency of the influenza vaccine in the elderly, which still remains a challenge [12]. In this study, the immunostimulatory properties of a parasite-derived synthetic peptide termed GK1 were exper- imentally explored when administered together with the 0264-410X/$ – see front matter © 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.vaccine.2005.09.014 JVAC-5664; No. of Pages 8