Biology Reference
In-Depth Information
phosphatidylglycerol (PG) phospholipids, sometimes including several sulfated gly-
colipids, predominate. Extreme halophiles contain 50-80% archaetidylglycerol meth-
ylphosphate (PGP-Me), an archaeal analogue of PG methylphosphate [31] that con-
tributes to membrane stability in hypersaline environments [32], archaetidylglycerol
(PG), and also some strains have minor amounts of sulfated PG [33].
Analysis of ESI-MS spectra of polar lipid isolates from
H. tebenquichense
,
BM
,
and
GC
, through comparison with the reference data [34, 35] suggested the main phos-
pholipids present in the extracts were PG, phosphatidylglycerophosphate methyl ester
(PGP-Me), and sulfated diglycosyl diphytanylglycerol diether (S-DGD). The promi-
nent peak at 1055.9 corresponded to S-DGD and is representative of the
Halorubrum
genus [36]. The archaeal cardiolipin, bisphosphatidyl glycerol (BPG) was only found
as traces in the three samples. While the complete lipid quantitation from each sample
as well as the RMN identifi cation of the S-DGD sulfonolipid will be accomplished in
ongoing research.
Up to now, only ARC made of TPL extracted from
Methanobrevibacter smithii
,
a methanogen archaea, are known to enhance the recruitment and activation of anti-
gen presenting cells [37, 38], induce co-stimulatory molecules expression [38], elicit
CD8+ cytotoxic responses even in the absence of CD4+ helper T-lymphocytes [39],
and to evoke a profound memory response, those all important stimuli that other ve-
sicular systems such as liposomes, niosomes, and ISCOMS are unable to trigger [40].
Additionally, although infl ammation in innate responses can enable further adaptive
responses [41], ARC made of TPL from
M. smithii
evoke immunologic memory in the
lack of visible infl ammation, activating dendritic cells in the absence of IL-12-depen-
dent initial infl ammatory response [42].
As regard to the extreme halophiles, ARC made of TPL extracted from
Halobacterium
salinarum
was reported to induce a robust initial CTL and antibody response in mice
[43]. Such titers, however, were not increased after boost administration and failed
to induce a signifi cant memory response. Only ARC made of TPL extracted from the
hyperthermophile
Thermoplasma acidophilum
produced the most intense antibody
memory responses to antigen challenge, together with a parallel induction of intense
cell cycling in CD4+ T cells suggesting effi cient maintenance of T-cell memory [43].
A further study showed that among ARC from nine archaeal strains tested, all trig-
gered remarkable primary CTL responses but only
M. smithii
and
T. acidophilum
, both
rich in caldarchaeols, evoked a strong recall at >50 weeks [44].
This is the fi rst report of adjuvancy after parenteral administration of ARC-
BM
/
GC
-BSA. Both ARC elicited a strong and lasting primary antibody response, and re-
markably in the absence of caldarchaeols in their lipid compositions, an enhanced
memory humoral response after boosting with the bare antigen in C3H/HeN mice
upon sc immunization. The ARC-
BM
/
GC
-BSA initially triggered higher antibody ti-
ters than BSA formulated in alum adjuvant. Additionally, IgG isotype analysis of im-
munized mice revealed that both BSA-specifi c IgG1 and IgG2a antibodies were raised
by both ARC-
BM
/
GC
-BSA, suggesting induction of a mixed Th1/Th2 response, in
agreement with a previous report [39]. Our preliminary fi nding of humoral immune
memory response elicited by ARC from extreme halophiles, together with established
