Thanks to Siegfried Schwarze, a research activist from Germany, for writing down these notes from the meeting we had this past Sunday, March 4, 2012 in Seattle prior to CROI-2012.
Sometimes the most important events don‘t take place at the conference
itself but rather at the surrounding
workshops. This seemed to be the case this year. Before the official opening of
the Retrovirus Conference, American activists organized a cure workshop.
Among the 60 or so participants there were even some high-profile researchers
and FDA employees underlining the quality of this workshop.
Dan Kuritzkes started with an overview of the work of the Aids Clinical
Trials Group (ACTG) in the field of the cure, this being meanwhile the focus
of the work of this study network. He emphasized the importance of asking the
right questions first:
– Can the residual virus production below the limit of detection been
suppressed by intensification?
– is there a practically relevant decay of latent reservoirs?
– can strategies that activate latent cells further lower the viral load?
– can a combined approach lead to control of viral replication without
drugs (functional cure)?
Apart from that, we must first find out how to approach the reservoirs
methodically and what to measure.
Then he gave an overview of current ACTG trials:
– A5276s: Patients with ongoing viral replication inspite of therapy (70
patients recruited, further 40 patients identified as suitable)
– Planned study to look at the decay of reservoirs in different patient
groups (acute / chronic infected, elite controller, blipper, patients failing
therapy / resuppressing)
– A5248/9s: Viral dynamics with TDF/FTC/RAL (cf. Abstract 672). Since
viral decay is much faster with Raltegravir-containing regimens, the pecularities of
this combination should be looked at.
– A5281: studying a multi-antigen/cytokine/DNA-vaccine (already
recruiting, so far no tolerability issues)
– A5286: Study looking at Rifaximin (an oral broad-band antibiotic that
is not being resorbed and therefore active only in the gut). Can the microbial
translocation and the resulting systemic inflammation be mitigated? Also the
influence on the reservoirs is to be studied.
– A52301: Anti-PD1-Antibody: Quiescent cells harboring latent HIV can be
forced out of latency with antibodies against the PD1-receptor and start
producing virus. This study is still in concept phase.
– A52308: ART for elite controllers
– PR652: Effect of romidepsin (a cancer drug developed by Celgene that
also acts as HDAC-inhibitor that can activate latent cells but isn‘t mutagenic
in the Ames test as other drugs of this class) on the reservoirs: concept
Finally, Kuritzkes came back to the questions that need to be addressed:
– What is the goal?
– sterilizing cure?
– functional cure, i.e. control of the virus by the immune system?
– reduction / elimination of the remaining viral load?
– reduction / elimination of viral reservoirs in the various
Which endpoints should be looked at?
– proof of biological activity on the target or the selected mechanism?
– proviral DNA in PBMSs?
– proviral DNA in cells of the compartments (which?)?
– cell-/tissue associated viral RNA?
– no viremia during analytical treatment interruption (ATI)
Here he pointed out the (dis-)advantages of an ATI:
-Best test for functional cure
-quantitative and qualitative analysis possible:
-Rebound of viral load
(or lack of)
– time to rebound
– time to new setpoint
– setpoint at a new (lower) level than before therapy
– Risk of inflammatory syndrome like during primary infection
– risk for OI, CV-events, death (like in SMART-study)
– increased transmission risk
We also have to think which patients are best being studied:
– patients with successful ART (i.e. undetectable VL)
– first vs. following regimes?
– highly therapy experienced patients?
– patients with well preserved immune function (high CD4-counts) or with
– Elite controller?
– acutely infected patients?
– patients in need of a bone marrow transplant?
Finally, we must not forget the risk-benefit-balance since all new
therapies will have to compete with established ART which is generally well
tolerated and harbors usually only minor risks.
After that, Romas Geleziunas, Director of Virology at Gilead Sciences
gave an overview of his company‘s activities in this area.
Gilead is focussing on the activation of HIV-expression in latently
There are several possibilities:
– De-repress chromatin (HDAC-inhibitors)
– activate transcription factors (NF-ƘB)
– activate HIV mRNA Elongation (PTEF-b)
– Other mechanisms, still to be found by Hight-throughput analysis (HTS)
Gilead has developed an automatic system that can measure the reversal
of latency with high numbers of samples at the same time. Already several new
drugs have been discovered that can wake cells from latency. One of these,
GSI-002 has the advantage of not being mutagenic and not activating T-cells
itself. Some other compounds they found have such unbelievable names as “Thapsigargin“ or “Tyrphostin A“.
Another possible mechanism to eliminate HIV uses the “toll-like-receptor 7“ (TLR7). This receptor binds single-strand RNA and leads
to the production of type-1 interferons (IFN alpha/beta). GS-9620 is a
TLR7-agonist that has been shown to lower RNA and viral antigen production in
several animal models. In a next step they will look whether this drug can play
a role in eliminating HIV-infected cells. The mechanism of HIV latency needs to
be understood still more fully and new drugs need to be discovered that play a
role in or can interfere with this process.
Dale Ando, working for Sangamo Biosciences, once more presented the
method of his company to knock out the gene for the CCR5-receptor with sequence
specific zinc finger nucleases. This leads to CD4-cells that are immune against
infection with CCR5-tropic HIV. Unfortunately, they didn‘t show any new data.
The procedure seemed to have worked exceptionally well in one patient, who is
heterozygous for the Δ32-mutation, i.e. he has only one functional CCR5-gene
per cell. Therefore, the next studies will recruit preferentally such patients.
Furthermore, the procedure will be adapted for stem cells. The problem is, that
the introduction of the zinc finger nuclease into the cells also triggers the
differentiation process and the cells wouldn‘t be stem cells any more.
Sometimes the devil is lurking in the details… Good news is, that the
procedure has been automated, so more patients can be treated which facilitates
Birger Sørensen from Bionor Pharma, a small Norwegian Biotech company
with only 19 employees presented a very interesting approach: They changed
certain highly conservated regions of the p24 protein in a way that makes it
much more effectively recognized by human immune cells. For some time it was
already known that infected people with a strong immune response against p24
have a slower disease progression. In order to further strengthen the vaccine
response, they use their product called Vacc-4x together with GM-CSF (a growth
factor for granulocytes/macrophages). Four primary and booster immunizations in
40 patients led to 92% showing a immune response with good tolerability. In
another study patients were immunized while on ART, then there was a 10 week
waiting period to allow the immune system to calm down and finally ART was
stopped. In all patients the viral load rebounded upon interruption, but the
vaccinated patients reached a new setpoint that was about 0,4 log lower (i.e. average
viral load 20.000 cp/ml instead of 60.000). They hope to further lower the
setpoint with more round of vaccination. In addition they try to improve the
immune response with immune modulators like lenalidomide.
Another approach, called Vacc-C5 aims in a different direction:
antibodies against the C5-region of gp120 cannot neutralize the virus, but they
still lead to a slower disease progression. This is probably because the
complex of C5 and gp41 bears some similiarity with the human HLA-complex and can
hyperactivate the immune system. Antibodies can block this hyperactivation and
so slow down the disease progression. In animal trials it was possible to
produce antibodies with the Vacc-C5 vaccine. Trials in humans are planned. Both
approaches together would make use of the cellular as well as the humoral arm
of the immune system and such a combined approach could be an important step on
the way to a cure. The main problem right now is money because studies are
expensive and a small company like Bionor is heavily dependent on investors.
John Zaia from Beckmann Research Institute gave an overview over the
state of stem cell research in the area of HIV. It was a stem cell transplant
that led to the cure of the “Berlin patient” and brought cure research back on
the scientific agenda of the HIV researcher. But it is still unknown which
factors were important for this experiment to succeed. Some researchers think
that the graft-vs.-host-reaction, which almost killed the patient, was crucial
– in addition to the radiation and the intense chemotherapy. So far, there is
no second “Berlin patient”, probably because the combination of the right
tissue antigens and the CCR5-Mutation is rather rare. That‘s why they try to
introduce the required CCR5-mutation artifically in bone marrow cells of
donors. Another possibility to get stem cells is cord blod from newborns. But
again here is the problem of the rare occurence of a CCR5-Mutation so there are
plans to found a blood bank of cord blood with CCR5-Mutation. Alltogether the
field of stem cell therapy is still in it‘s infancy. In patients who don‘t need
a stem cell transplant for medical reasons (i.e. lymphoma), the risks are still
too high. This method has only a chance for broader use when there will be new
developments making radiation and chemotherapy unnecessary.
Pablo Tebas gave an overview over the activities of his workgroup.
Apart from collaboration with Sangamon in the field of zinc finger nuclease
(see above), the group also tries to increase the CD8-mediated killing of
HIV-infected cells by providing the CD8s with a new T-cell-receptor that can
recognize HIV much better than it‘s natural counterpart. Clinical studies
including 16 weeks of ATI and rectum biopsies are planned. And there is renewed
interest in the long known antiviral activity of interferon alpha against HIV.
In a study with HIV patients that had undetectable viral load, stopped therapy
and used pegylated interferon alpha as monotherapy, the viral load could be
kept below 400 cp/ml in 45%. At the same time, the number of integrated HIV
genomes in the circulating CD4-cells went down. Interestingly, this effect was
also seen in a group of patients receiving only half of the standard dose (90
µg instead of 180 µg interferon alpha per week) – with much better
David Evans and Nelson Vergel, two of the activists who had organized
the workshop, did a internet survey about the willingness of patients to
participate in clinical studies that are not of immediate benefit to them but
maybe even have some serious risks. They found among many other things, that
unexpectedly many patients would consider participating in such studies for
mainly altruistic reasons.
Steven Deeks provide additional insight in the mechanisms of viral
persistence of HIV:
– reservoir of long living CD4 positive Tcm (Central Memory cells)
harboring transcriptionally inactive HIV genome (latently infected)
– homeostatic proliferation of these cells (i.e. because these cells
divide to make up for natural decay, the integrated HIV genome will also be
distributed to the daughter cells and the number of latently infected cells
therefore decreases very slowly)
– low level („cryptic“) viral replication induced by environmental
stimuli, e.g. interactions with HIV infected CD4-cells in tissue.
– failure to develop or maintain an effective anti HIV immune response
Deeks described these mechanisms in further detail and also some ideas
how to overcome them, e.g. antibodies against PD1 to reverse latency.
Keith Jerome and Hans-Peter Kiem were the last presenter and described
their efforts to
– establish an HIV-resistant immune system permanently in patients and to
– eliminate existing HIV reservoirs.
For the first goal they also use zinc finger nucleases. The viral
reservoirs will be attacked with different tools: One idea is to mark infected
cells with siRNA-probes to make them visible for the immune system so that
killer cells can get rid off the infected cells. Another method uses “homing
endonucleases”, special restriction enzymes from yeast. The enzyme Y2-Anil has
been changed in a way to recognize HIV-specific areas in the genome and cut
them. These cuts will be recognized by the cells repair system and the gaps
will be filled with random nucleosides. This leads to “nonsense“ viral sequence
that doesn‘t produce active virus anymore. This method has a big advantage
against the Tre-recombinase that has been described some time ago. Y2-Anil
recognizes longer, very conserved regions of HIV so that it could be effective
against a broad range of different HIV types whereas Tre recombinase is limited
to the LTR region of HIV (in fact the efficacy of Tre recombinase has been
shown only against a very artificial laboratory strain of HIV and not the wild
All speakers of this exceptional workshop shared the view that we must
not raise premature and unrealistic hopes in patients. First steps have been
made but we need many more successes in analytics, basic science and
translational research in the animal model as well as in patients before the cure
will be within reach.