Liposomal vaccine formulations as prophylactic agents: design considerations for modern vaccines

DDA-based cationic liposomal vaccines for the 
treatment of tuberculosis
The World Health Organization (WHO) estimated 1.8 
million deaths in 2015 were related to tuberculosis infec-
tions (TBIs) [
120
]. The global estimate for latent tubercu-
losis infections (LTBI) was recently determined to be 23% 
(approximately 1.7 billion persons from the total popula-
tion) [
121
]. Because of current tuberculosis (TB) vaccine 
efficacy variability, inefficiency and waning immunity 
(like Bacillus Calmette–Guerin, BCG) [
57
, 
58
], it is 
imperative to develop novel vaccines strategies that will 
improve prophylactic avenues for TBIs and reduce the 
overall death rate or latency associated with them. One 
Table 6 Liposomal vaccine formulations tested in parasitic infection models
Cell cultures and no vaccination in animal models were employed
N/A not applicable
Lipid(s) and sterol used
Parasite
Cell line/animal model 
used
Administration route Promising liposome 
formulation
References
MPL/QS21 (liposome-
based)
Plasmodium falciparum Rhesus macaques
Intramuscular
MPL/QS21 (liposome-
based)
[
114
]
Egg lecithin/Chol, egg 
lecithin/SA and egg 
lecithin/PA
Leishmania donovani
BALB/c mice
Intraperitoneal
Lecithin/Chol/SA
[
116
]
PC/Chol, PC/SA, PC/PA and 
PC/PS
L. donovani
–
Intravenous, N/A
PC/SA
[
117
, 
118
]
EPC/EPG, EPC/EPG/Chol 
and DSPC/DPPG/Chol
P. vinckei
Female C57BL/6J mice
Intraperitoneal
EPC/EPG, EPC/EPG/Chol 
and DSPC/DPPG/Chol
[
113
]

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Page 16 of 23
De Serrano and Burkhart  J Nanobiotechnol (2017) 15:83 
of the principal improvements revealed in the last years is 
the development of adjuvanted subunit vaccines.
To diminish the detrimental effects of tuberculosis in 
humans, certain studies have focused on subunit vac-
cine development based in cationic lipid formulations 
(Table 
7
). Adjuvants are required for the development 
and efficacy of subunit vaccines, potentiating immune 
responses. Several adjuvants have been studied in the 
past 20 years including the adjuvanting properties of the 
lipid DDA [
122
]. Forty years ago, Snippe et al. investi-
gated the effect of DDA in mice (via an intracutaneous 
administration) determining that delayed hypersensitiv-
ity occurred by the onset of footpad swelling 5 days after 
vaccination [
123
]. Subsequently, a study by van Houte 
et al., where low- (DOPC and DLPC) and high-transi-
tion temperature (DSPC) lipids were utilized with DDA 
as liposome bilayer components, discovered less immu-
nogenicity of the liposomes as DDA concentration 
decreased [
50
]. Additionally, an earlier review discussed 
the immunostimulatory properties of DDA and its uses 
in different vaccines for veterinary and human infections 
[
47
]. We will present the reader with the most significant 
studies performed that cover the utilization of the cati-
onic lipid DDA in subunit vaccine development.
Holten-Andersen et al. mixed the recombinant immu-
nodominant M. tuberculosis antigens (ESAT-6 and 
Ag85B-ESAT6), DDA and different immunomodulators, 
analyzing the immune responses against BCG vaccina-
tion in mice (subcutaneous administration) [
124
]. The 
studied immunomodulators included saponin, calci-
triol, β-glucan, n-hexadecane, TDB, muramyl dipeptide 
(MDP) and monophosphoryl lipid A (MPL). Investiga-
tors determined that the combination of the antigens 
with DDA and TDB generated a strong protective T
H
1 
immune response against the mycobacterium, contrast-
ing with BCG vaccination. In another study, M. bovis 
BCG lipid extracts were tested for their adjuvant char-
acteristics [
125
]. BCG lipids were incorporated in DDA-
based liposomes and administered subcutaneously to 
female BALB/c or C57BL/6 mice. BCG lipids coupled 
with the antigen Ag85B-ESAT-6 fusion protein in cati-
onic liposomes induced significant levels of IFN-γ and 
relevant antibodies (IgG2A) titers, characteristic of T
H
1 
immune responses. Antigens from other sources (Chla-
mydia muridarum and tetanus toxoid) were studied and 
relevant antibodies were detected when administered 
with the so called mycosomes (BCG lipids + cationic 
liposomes).