Immunological Investigations, 2014; 43(7): 653–666 ! Informa Healthcare USA, Inc. ISSN: 0882-0139 print / 1532-4311 online DOI: 10.3109/08820139.2014.914531 A novel adjuvant, the mixture of alum and naltrexone, augments vaccine-induced immunity against Plasmodium berghei Shahram Shahabi, 1 Hakim Azizi, 2 Ebrahim Mazloomi, 3 Khosrow Hazrati Tappeh, 1,2 Shahram Seyedi, 3 and Habib Mohammadzadeh 2 1 Cellular and Molecular Research Center, Urmia University of Medical Sciences, Urmia, Iran, 2 Department of Parasitology and Mycology, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, Iran, and 3 Department of Immunology, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, Iran We previously showed that the mixture of naltrexone (NLT), a general opioid antagonist, and alum, acts as an effective adjuvant in enhancing vaccine-induced T helper 1 (TH1) humoral immune responses against Toxoplasma gondii. Here, we tested the efficacy of the mixture of NLT and alum in the induction of immunity in response to blood stages of Plasmodium berghei (BSPb) as a model vaccine. BALB/c mice were divided into five vaccination groups. Mice in the experimental groups received the BSPb vaccine alone or in combination with the adjuvant alum, NLT or the alum-NLT mixture. Mice in the control group received PBS. All mice were immunized on days 0, 7 and 14. Two weeks after the last immunization, immune responses to Plasmodium berghei were assessed. Our results indicated that including the alum-NLT mixture as an adjuvant during vaccination increased the ability of the BSPb vaccine to enhance lymphocyte proliferation, shifted the immune response towards a TH1 profile and increased Plasmodium berghei-specific IgG2a. This resulted in improved protective immunity against Plasmodium berghei. In conclusion, administering alum-NLT mixture in combination with the BSPb vaccine enhanced the vaccine-induced immunity, and shifted the immune response toward TH1 pattern. Keywords Adjuvant, alum, malaria, naltrexone, Plasmodium berghei, vaccine INTRODUCTION Malaria is responsible for the loss of more young lives than any other infection (Good & Doolan, 2010). Despite intense efforts worldwide, progress towards an effective malaria vaccine has been disappointing (D’Argenio & Wilson, 2010; Douradinha & Doolan, 2011). One barrier to development of suitable malaria vaccines is the unavailability of potent adjuvants (especially those that induce Correspondence: Shahram Shahabi, Habib Mohammadzadeh, Department of Parazitology and Mycology, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, 5756115111, Iran. E-mail: habibmhaji@yahoo.com Immunol Invest Downloaded from informahealthcare.com by 65.49.14.93 on 09/08/14 For personal use only.