Mml. Pompeu et al., Differences in gamma interferon production in vitro predict the pace of the in vivo response healthy to Leishmania amazonensis in healthy volunteers, INFEC IMMUN, 69(12), 2001, pp. 7453-7460
The initial encounter of Leishmania cells and cells from the immune system
is fundamentally important in the outcome of infection and determines disea
se development or resistance. We evaluated the anti-Leishmania amazonensis
response of naive volunteers by using an in vitro priming (IVP) system and
comparing the responses following in vivo vaccination against the same para
site. In vitro stimulation allowed us to distinguish two groups of individu
als, those who produced small amounts of gamma interferon (IFN-gamma) (n =
16) (low producers) and those who produced large amounts of this cytokine (
n = 16) (high producers). IFN-gamma production was proportional to tumor ne
crosis factor alpha and interleukin 10 (IL-10) levels but did not correlate
with IL-5 production. Volunteers who produced small amounts of IFN-gamma i
n vitro remained low producers 40 days after vaccination, whereas high prod
ucers exhibited increased IFN-gamma production. However, 6 months after vac
cination, all individuals tested produced similarly high levels of IFN-gamm
a upon stimulation of their peripheral blood mononuclear cells with Leishma
nia promastigotes, indicating that low in vitro producers respond slowly in
vivo to vaccination. In high IFN-gamma producers there was an increased fr
equency of activated CD8(+) T cells both in vitro and in vivo compared to t
he frequency in low producers, and such cells were positive for IFN-gamma a
s determined by intracellular staining. Such findings suggest that IVP resp
onses can be used to predict the pace of postvaccination responses of test
volunteers. Although all vaccinated individuals eventually have a potent an
ti-Leishmania cell-mediated immunity (CMI) response, a delay in mounting th
e CMI response may influence resistance against leishmaniasis.