7 HIV Persistence Workshop: third day
The second day of the HIV Persistence Workshop addressed the issues of:
-immunology of HIV persistence
-pharmacology of HIV persistence
-practical issues in designing HIV cure trials
SESSION 5: Immunology of HIV persistence
Dr Goonetilleke (Chapel Hill) showed that HIV-1 specific responses are at low frequency but broadly detectable in durably suppressed adults.So, they are rare but with a broad distribution.
HIV infected cells reside in lymph node follicules and sites of immune privilege. CD8+ T cells are excluded from B cell follicules in lymph nodes.
Shifting T cell immunodominance is observed as infection progresses, and escape occurs.
Immunodominance and epitope entropy explain almost 50% of time to virus escape.
Dr Prado (Barcelona) studied 38 HIV controllers and found, ex vivo, a reduced reactivation from their resting CD4+ T cells that correlates with DNA levels.
Ex vivo HIV spread is also limited in HIV controllers and they carry homogenous viral populations without major genetic defects.
HIV controllers with no HIV-1 protein production in vitro from their CD4+ T cells have a reduced amplitute of CD8+ T cell responses
Dr Clutton (Chapel Hill) addressed the isuue wheather LRA can impair in vivo CD8+ T cell functions.
PBMCs from patients on ART were taken and different LRAs tested:
-HDAC inhibitors: vorinostat, romidepsin, panobinostat
-PKC modulators: Ingenol dibenzoate, prostratin, bryostatin
Vorinostat has little effect on activation.
Romidepsin and panobinostat had a modest effect on activation which was not durable.
PK inhibitors had an important effect (increase) on activation.
Romidepsin, Panobinostat, Prostratin and Bryostatin affected cell viability.
PKC modulators induce non-specific cytokine production by T cells (MIP-1beta, TNF-alpha, INF-alpha).
Panobinostat diminishes antigen specific CD8+ T cell responses although Ingeneol)db increased it by 2 fold.
PKC modulators induce non-specific T cell proliferation.
Romidepsin, Panobinostat, Prostratin and Bryostatin inhibit antigen-specific CD8+ T cell proliferation.
Dr Ruiz (Barcelona) adressed the issue whether LRAs induce CTL activation and at what level of p24 production.
They showed that LRAs can induce HIV antigen presentation to CTL recognition and that the amount of antigen produced was sufficient for effective killing.
In their hands, LRAs do not produce CTL toxicity and extremely low levels of HIV reactivation were efficient.
Dr Wacleche (Montreal) showed that long-lived Th17 subsets contribute to HIV-1 persistence during ART.
The frequency of CCR6+ DN (double negative) cells is preserved in ART treated patients. They are the most preponderant Th17 subset, harbour HIV DNA. When they are reactivated, p24 is produced.
On the contrary, Th17 and CCR6+ DP (double positive) cells are depleted on ART.
Dr Boritz (Bethesda) sequenced HIV strains from HIV controllers. He found that most infected cells in blood come from a few precursors that became infected in the distant past and underwent masssive proliferation. Most HIV DNA is in TTM and TEM. Sequencing shows that HIV controllers harbor repetitive sequences that differ from plasma virus. Some of the clones can produce replication competent virus.
Most sequences correspond to a small cluster.
The lymphoid tissue in most controllers is rich in recently infected cells. Lymph node samples showed that most of viral DNA is in the Tfh subset.
No virus transcripts were found in blood and a few in lymph nodes.
In lymph nodes, virus was closely related to plasma virus, not only in B cell follicles but in all the lymph nodes.
Dr Wacleche (Montreal) showed that HIV permissiveness in Th17 cells is regulated at entry and post entry.
Transcripts associated with T-cell polarization/differentiation (RORC, KLF2), circadian clock (ARNTL), TCR signaling (ZAP-70, Lck), apoptosis (PPARG) were up regulated in Th17 versus Th1 cells.
Th17 exhibit superior sensitivity to TCR triggering, increased proliferation potential, and superior NK-kB DNA-binding activity.
RORC is a major regulator of HIV replication in Th17 cells.
Dr Boucau (Cambridge) studied LRAs and cellular activation in the way they affect antigen processing in primary CD4+ T cells.
Only Bryostatin-1 and Ingenol caused a significant increase in cellular activation after drug treatment, and they changed the degradation of extended peptides.
SESSION 6: Pharmacology of HIV persistence
Dr Fletcher (Omaha) gave the introducing talk. He first mentionned data obtained by whole body ImunoPET in SIV models. They show that the probe uptake is globaly very low but that residual signals are found in colon, spleen, male genital tract and LN.
He also showed previously published data with Maraviroc in mice where distribution is limited in CNS but far more greater in GALT and LNs than in blood.
Then he listed the factors that can affect drug penetration in tissues:
-transporters. For exemple MRP1 and MRP4 mRNA expression in healthy donors have different distribution accross the colon. PgP expression increases from duodenum to ileum.
In a model of lymphatic endothelial cells, the author showed that Atazanavir experiences a large efflux which is 5 times larger than the influx.
-lymph nodes fibrosis.
He then took the exemple of Tenofovir which concentrates well in rectal cells and hypothezised that this could explain the efficacy of PrEP.
In PrEP an intracellular TFV-DP concentration of 16 fMol/million rectal cells was associated with a 90% reduction in HIV acquisition.
Then, he looked at LNs in 35 subjects and found that even in the same drug class, different drugs do not behave equally.
Regarding TAF, its concentrations are increased in lung, inguinal LNs, spleen, ileum, prostate, bone marrow, but it remains below the limit of detection in the brain.
Nanoformulations of ARVs could improve tissue diffusion. For exemple, a formulation of Tenofovir, Lopinavir and ritonavir given sub-cutaneously in macaques showed an increased concentration in LNs for Lopinavir and Ritonavir, but not for Tenofovir.
Other future approaches also include Cabotegravir nanosuspension.
Finally, anti-fibrotic therapy is studied in macaques with Pirfenidone.
Dr Bui (Pittsburg) studied 5 aviremic patients (suppressed for more than 2 years) and stimulated ex vivo their cells with PMA/Ionomycin given from day 0 to day 7 and day 21 to day 28. He then sequenced the supernatant. Virus production was found after 1 stimulation and then a plateau was obtained. He showed that dynamics of proviral populations are complex after cell activation. There are persistant clonal populations from which it is possible to recover intact proviruses. Cells with non-induced proviruses at the first stimulation can be induced by repeated stimulation. Cells with non-induced proviruses can proliferate.
Dr Greene (San Francisco) showed the differences in CD4+ T cells beetwen blood and tonsils. In tonsils HLA-DR is up regulated, there is an increase in CD69 expression and MHC class II receptors.
Blood CD4 T cells are resistant to death by the pyroptotic pathway, but not CD4 cells from tissues.
CD4 from blood show a weak response to single LRA and also a weak response when LRA are combined.
CD4 from tonsils show a higher response and there is synergy when LRAs are combined.
JQ1 exerts, unexpectedly, a potent effect alone and in combination with Ingenol B.
Dr Bendayan (Toronto) studied the expression of drug transporters in the testis. In uninfected patients, she found expression of ABC transporters and SLC transporters at the level of capillaries and Sertoli cells.
In 4 HIV-infected patients from the Orchid study reported yesterday, she found the following ratio between testis and blood:
-for Darunavir: 0.10 in 1 patient and 0.22 in another
-for EFV: 0.25
-for ATV: 0.79
SESSION 7: Drug discovery
Dr Barnard (Kenilworth) addressed 4 questions:
1-Can HDAC inhibitors induce (enough) antigen alone or in combination?
He showed that SAHA (which opens chromatin) plus IL-15 (which increases transcription) is a synergistic combination.
HDACi are able to drive expression from genetically diverse proviruses.
PKC are more potent but induce inflammatory cytokines at high levels.
2-Is the amount of antigen expression sufficient for clearance of cells?
HDACi flushed cells can be efficiently killed by a bi-specific HIV Env/CD3 antibody and CD8 T cells
3-Does expression we get reflects the diversity of latent infection and of the reservoir?
No clear answer available yet.
4-Can we improve future LRAs?
There are acute CV risks with some HDACi designed for treating cancer.
Future LRAs have to be orally administrable, more potent, more selective, tolerable with no acute CV risk.
Dr Ando (Richmond) presented 4 patients treated with the Sangamo Zinc Finger Nuclease to knock down CCR5 expression. Cells were transfected by an adenoviral vector. Prior conditioning regimen used 1 g/M2 of Cytoxan. Both CD4 and CD8 T cells were modified and reinfused. 3 patients underwent structured treatment interruption.
Both CD4 and CD8 T cells increased within the first week of infusion. These CD8 T cells persisted despite STI. In 2 out of 3 patients STI duration was about 1 year with very low levels of viremia.
One patient failes, with viremia at 22,700 copies/ml after STI.
The large increase in CCR5 modified CD8+ T cells may mimick Elite Controllers.
The SB-728mRT 1401 study used mRNA CCR5 ZFN gene editing in both CD4 and CD8 T cells. Seven subjects were included. They received 1 g/m2 of Cytoxan prior to 2 or 3 infusions of cells.
Dr Murry (Foster City) screened 465,000 compounds and particularly studied one, called GS-46 which is a cyanotriazole. GS-46 and Bortezomib (a proteasome inhibitor) are highly synergistic.
They do not activate T cells.
GS-46 is not an HDACi. It probably works by repressing many pathways associated with T cell activation.
Dr Bosque (Salt Lake City) also performed drug screening and went down with a compound called HoAt which is a triazol-1-ol analog. Its mechanism of work is by blocking the SUMOylation of STAT5.
SESSION 8: Practical issues in designing HIV cure trials
Dr Eron (Chapel Hill) discussed the different trial endpoints that can be used.
This depends on what intervention we study:
-intervention focused on recativating latency
-interventions focused on enhanced killing
-interventions focused on preventing infection of vulnerable cells. For theses intervention a treatment interruption might be the only way to assess the effect.
The timing of the interventions is critical and the timing of outcome measures may also be critical.
What are the populations we should include in GIV cure trials?
Acutely-infected patients have a small reservoir, limited HIV diversity, preserved immunity. But a very small reservoir means that it will be difficult to measure an effect without ART interruption.
Chronically-infected patients have viral diversity, escapes variants, exhausted HIV-specific immune response, but a greater reservoir.
Finally, there is an issue of risk: what kind of risk is acceptable?
Dr Hill (Cambridge) argued that mathematical models can help to design HIV cure trials, even before data exist, due to the existence of some observations.
J. Salzwedel (New York) emphazised the need of implementing GPP (Good Participatory Pratice) by involving stakeholders to facilitate the building of effective partnerships amon all the reserach stakeholfers including "community".
J. Taylor and K. Dubé (CAB) showed the results of a countrywide survey performed last October (400 participants) regarding their willingness to participate to HIV cure trials.
There were 310 males, 86 females, 1% transgenders.
47% have lived for 26-50% of their life with HIV.
The ages most represented were 46-60 years.
97% expressed willingness to participate to cure trials. This number drops to 59% if it is the first study in humans.
Among motivators, there were to gain knowledge about their health (78%) and helping finding a cure (95%).
Among dismotivators were the risk to active cancer genes (49%), the risk of drug resistance (37%), the risk of toxicities (30%), the risk of hair loss (32%), the risk of transmitting HIV (25%).
68% were very willing or willing to stop ART.
8% think that a cure already exist.
33% think that the cure is 6-10 years away
Key words: HIV cure, HIV eradication, HIV latency, HIV persistence, HIV reservpoirs, HIV workshop