Vaccination with toxofilin DNA in combination with an alum-monophosphoryl lipid A mixed adjuvant induces significant protective immunity against Toxoplasma gondii

Abstract

BackgroundA widely prevalent disease, toxoplasmosis poses serious health threats to both humans and animals; therefore, development of an ideal DNA vaccine against Toxoplasma gondii is needed eagerly. The purpose of the present study is to assess the protective efficacy of a DNA vaccine encoding the T. gondii toxofilin gene (pEGFP-toxofilin). In addition, toxofilin DNA vaccine combined with the individual adjuvants, alum or monophosphoryl lipid A (MPLA), or a mixture of alum-MPLA adjuvant were screened for their ability to enhance antibody responses.MethodsUsing bioinformatics, we analyzed the gene and amino acid sequences of the toxofilin protein, recognizing and identifying several potential linear B and T helper (Th)-1 cell epitopes. BALB/c mice were immunized three times with either toxofilin DNA vaccine alone or in combination with the adjuvants such as alum, MPLA or an alum-MPLA mixture. The systemic immune response was evaluated by cytokine, the percentage of CD4 (+) and CD8 (+) T cells and specific antibody measurement. Two weeks after the last immunization, protective efficacy was evaluated by challenging intraperitoneally with 1 × 104 tachyzoites of T. gondii or intragastrically with 20 cysts of T. gondii PRU strain.ResultsAll experimentally immunized mice developed strong humoral and cellular immune responses compared with the control groups. Moreover, by comparison with the non-adjuvant toxofilin DNA vaccine group, adding alum adjuvant to toxofilin DNA vaccine resulted in an increase in humoral response and a skewed Th2 response. However, the MPLA adjuvant with toxofilin DNA vaccine induced significantly enhanced humoral and Th1-biased immune responses. Importantly, the co-administration of alum-MPLA adjuvant in combination with the toxofilin DNA vaccine shifted the Th2 immune response to a Th1 response compared with the alum-toxofilin group, and elicited the strongest humoral and Th1 responses among all the groups. At the same time, a longer survival time and less cyst amounts against T. gondii infection were also observed in the alum-MPLA-toxofilin group in comparison with single or no adjuvant groups.Conclusions Toxoplasma gondii toxofilin is a promising vaccine candidate that warrants further development. Co-administration of the alum-MPLA adjuvant mixture with DNA vaccine could effectively enhance immunogenicity and strongly skew the cellular immune response towards a Th1 phenotype.

Vaccination with poly(D,L-lactide-co-glycolide) nanoparticles loaded with soluble <em>Leishmania</em> antigens and modified with a TNF&alpha;-mimicking peptide or monophosphoryl lipid A confers protection against experimental visceral leishmaniasis

“…Encapsulation of MPLA in PLGA-sLiAg NPs resulted in significant reduction of parasitic load in accordance with previous studies demonstrating the necessity for an adjuvant for experimental vaccines against leishmaniasis [36][37][38][39][40] but also against other intracellular pathogens. 41,42 The conjugation of the p8 peptide to PLGA-sLiAg NPs resulted in protection levels similar to those induced by PLGA-sLiAg-MPLA vaccination. Interestingly, vaccination with PLGA-sLiAg-MPLA or p8-PLGA-sLiAg resulted in almost sterile protection in the spleen 4 months post-challenge infection indicating an important role of MPLA encapsulation, as well as for p8 conjugation to nanoformulations.…”

A lipid A-based TLR4 mimetic effectively adjuvants a Yersinia pestis rF-V1 subunit vaccine in a murine challenge model

“…Our data demonstrate that use of BECC438 as an adjuvant induces strong T H 1 and T H 2 immune responses, similar to PHAD, and suggest that it may be beneficial as a component of next-generation vaccine formulations against intracellular pathogens and cancer, and that comprise purified protein, peptide [30], and DNA [31] antigens. In addition to enhancing the magnitude of the antibody responses in our vaccine study, BECC438 effected immunoglobulin class switching to T H 1-associated subtypes.…”

Study on Circulating Antigens in Serum of Mice With Experimental Acute Toxoplasmosis

“…Most CAgs are ESA that play important roles in inducing appropriate humoral and cellular immune responses against T. gondii ( Hafid et al, 2005 ; Jongert et al, 2009 ; Costa-Silva et al, 2012 ; Chen et al, 2013 ; Daryani et al, 2014 ). Moreover, some proteins identified herein such as PLP1 ( Yan et al, 2011 ), M2AP ( Dautu et al, 2007 ), SAG1 ( Mohamed et al, 2003 ), protease inhibitor PI1 ( Cuppari et al, 2008 ), Histone H2A ( Yu et al, 2020 ), Elongation factor 1-alpha (EF-1α; Wang et al, 2017 ), CDPK9 ( Wang H. L. et al, 2016 ; Wang J. L. et al, 2016 ), HSP70 ( Mohamed et al, 2003 ), protein disulfide-isomerase ( Wang et al, 2013 ), and toxofilin ( Song et al, 2017 ) elicit powerful specific immune responses, providing partial protection against acute or chronic T. gondii infection. Thus, we evaluated the protective ability of TgRuvBL1, TgRNase H1, and TgRPS2.…”