5 research outputs found
Impaired B cells survival upon production of inflammatory cytokines by HIV-1 exposed follicular dendritic cells
Additional file 3. Activation of B and T cells upon different stimuli. The frequency of activated CD69 + cells among PBMCs (A), B cells (B) and T cells (C) are shown when PBMCs were exposed to different activation stimuli
Astrocytes during HIV infection of the brain : relevance for neuropathogenesis
The overall aim of the present thesis was to characterize the role that
astrocytes play for neuropathogenesis of AIDS dementia complex (ADC).
We studied whether it is possible to derive the phenotype of HIV-1 virus
by analyzing V3 sequences. Our analysis, conducted by comparing V3
sequences and replicative properties of 9 HIV-1 isolates (from four
patients), indicated that the shift from non syncytium inducing to
syncytium inducing phenotype did not always correlate with an increase of
V3 net charge. Thus extrapolation of the biological properties of HIV-1
variants from V3 sequences it is not always possible.
The frequency of ADC in cohorts of patients treated with zidovudine (AZT)
is very low. We analyzed whether AZT resistant strains could be found in
the CSF and blood of six patients treated with AZT. Blood isolates
resistant to AZT have been shown to be mutated at positions 41, 67, 70,
215 and 219 of the reverse transcriptase gene. In our study, we could
show that in the isolates from 4 (of 6) patients different pattern of
mutations were found in CSF isolates as compared to what found at the
same time point in blood. These results show that AZT reaches the CSF and
give support to the different evolution of the HIV-1 virus in the brain
and systemic compartments.
In order to further clarify the role of astrocytes in HIV-1
neuropathogenesis, we infected primary fetal astrocytes with 26 primary
HIV-1 isolates with defined biological properties, including isolates
with slow/low and rapid/high phenotypes and different chemokine receptor
usage. We demonstrated that human fetal astrocytes could be infected in
vitro with primary HIV-1 isolates independently of their biological
phenotype and chemokine receptor usage. Viral replication was not
sustained and stimulation with the cytokine IL-1[beta] promoted virus
production in astrocytes.
The HIV-1 receptor(s) on astrocytes was studied by analysing CD4
expression and chemokine receptor mRNAs and protein expression in primary
astrocytes. We could amplify the mRNAs for CXCR4, CXCR2, CCR5, CCR3, CCR2
and the orphan receptors APJ and Bonzo/STRL33/TYMSTR, although the
astrocytes did not express any of these receptors (nor CD4) at the cell
surface. This result was confirmed when the presence of chemokines
RANTES, MIP-1[alpha] MIP-1[beta], MCP-1 and SDF-1[beta] in culture did
not induce mobilization of intracellular calcium influx in astrocytes.
Therefore we suggest that primary HIV-1 isolates infect astrocyte
independently of CD4 and chemokine receptors.
Since neuropathological studies conducted on AIDS brains have shown that
astrocytes are activated and undergo apoptosis, we focused our attention
on molecules involved in the regulation of apoptosis. We analyzed the
expression of Fas and Fas ligand (FasL) in brain tissues obtained from
HIV-1 infected subjects, including asymptomatic HIV-1 carriers and AIDS
patients, and controls. The amount of Fas transcripts amplified from the
AIDS brains was higher than from the brain of asymptomatic carriers. The
FasL transcripts were expressed in the brain of patients who had
developed AIDS and of one asymptomatic carrier. Fas was predominantly
expressed by reactive astrocytes and FasL by CD3+ T-cells located in
proximity of reactive astrocytes. These results indicate that the
Fas/FasL pathway may be involved in apoptosis dysregulation in the brain
during AIDS.
This possibility was reinforced by the interesting finding that the
levels of soluble Fas (sFas) and sFasL were significantly higher in the
CSF of patients with ADC (n=29) as compared to ADC negative patients
(n=22) and HIV-1 negative controls (n=39). A decline of CSF sFas levels
was observed in patients treated with highly active antiretroviral
therapy (HAART) in parallel to the reduction of viral load in CSF. Taken
together, theses results suggest that sFas and sFasL may represent useful
markers for ADC diagnosis and for monitoring immune activation in the
brain during HAART.
We also explored the possibility that upregulation of Fas expression
during HIV-1 infection would render these cells susceptible to bystander
cell killings executed through virus-specific cytotoxic T-cells (CTLs)
invading the brain. Bystander cell killing has been shown to occur
through the Fas-Fas L pathway in different experimental conditions. The
response of a panel of astroglioma cell lines and primary human
astrocytes to supernatants from peptide activated CTLs was studied. Our
results showed that virus specific CTLs can produce soluble factors
capable of inducing apoptosis in 5110 astroglioma cell lines., Fas L is
not the only factor involved in this pathway of cell damage. Our results
showed that in the supernatant from activated CTLs are present additional
factor(s) that can mediate the apoptosis of astroglioma lines, alone or
in synergy with TNF-[alpha