Concanamycin A : Antibiotic molecule enables immune system to kill HIV infected cells


Ever since the first cases of a mysterious disease in the early 1980s exploded into the HIV/AIDS pandemic, researchers have been searching for ways to outsmart the deadly virus.

Now thanks to anti-retroviral therapy, people living with HIV can live relatively normal lifespans – as long as they take their medications every day.

“If they ever stop, in short order the virus rebounds and resets at the high levels seen before starting – and that seems to be the case even after decades of therapy,” says Mark Painter, Ph.D., a graduate student in the University of Michigan Medical School’s department of microbiology and immunology.

The reason is that HIV can hide inside the human genome, lying dormant and ready to emerge at any time. Because of this, a true cure for HIV relies on waking the latent virus and eliminating it before it has a chance to again take hold of the body’s cells, an approach known as shock and kill.

Working with a team under the direction of Kathleen Collins, M.D., Ph.D., they set out to find a weapon to kill HIV by targeting a protein called Nef.

In 1998, Collins, who is a professor of internal medicine and microbiology and immunology, discovered that HIV uses Nef to evade the body’s immune system by overriding the functioning of a protein on a cell’s surface that lets immune cells know that the cell is infected and in need of elimination.

By disabling this protein, called MHC-I, infected cells are able to proliferate.

The research tried determine if there was an FDA-approved drug or molecule already on the market that could override Nef, restore the functioning of MHC-I and allow the body’s own immune system, specifically cells known as cytotoxic T lymphocytes, to recognize the HIV-infected cells and destroy them.

“We started out screening a library of 200,000 small molecules and found none inhibited Nef,” says Painter.

Undeterred, they approached David Sherman, Ph.D. of the U-M Life Sciences Institute, whose lab studies the biosynthesis of natural products from microbes, such as cyanobacteria.

“Often synthetic molecules have quite a low molecular weight, meaning they are fairly small. And if you need to disrupt a large protein surface or interface, such as with Nef, a small molecule won’t work well or at all,” explains Sherman.

“A natural products library like the one at the LSI, on the other hand, is going to have molecules with a large range of weights and sizes.”

After screening approximately 30,000 molecules, they discovered that a class of antibiotic molecules called pleicomacrolides inhibited Nef.

“Pleicomacrolides are widely used in lab experiments when you want to shut down the lysosome. Because of this, they are considered toxic and risky to use as drugs,” says Painter. The lysosome is an essential cell organelle used to break down worn out cell parts, viruses and bacteria.

However, the team determined that a pleicomacrolide called concanamycin A inhibits Nef at much lower concentrations than those needed to inhibit the lysosome.

“As a lead compound for drug development, it’s fairly exciting because we can use a very low dose, and inhibit Nef without short-term toxicity to the cells,” said Painter.

In a proof of concept experiment, they treated HIV-infected, Nef expressing cells with concanamycin A and found that cytotoxic T cells were able to clear the infected T cells.

“It’s been extremely gratifying for this project, which began in my lab over a decade ago to finally come to fruition. I had hoped we would find something that worked as well as this compound does but it was never a guarantee that we would actually be successful.

This type of research is risky but extremely important because of the potential reward,” says Collins. But, she adds, the molecule is not yet ready to be used as a drug for treatment of HIV infected people.

“More research will be needed to optimize the compound. We will need to further separate the potent Nef inhibitory activity from the more toxic effect on lysosomal function to make it a viable therapy.”

Collins, Painter and their colleagues are continuing work on refining the chemistry of concanamycin A to make it even more viable as a potential therapy.

When combined with ART and future treatments that shock latent HIV awake, Painter notes the therapy could be used to clear any remaining virus, essentially curing HIV.

Antiretroviral treatment (ART) has significantly reduced morbidity and mortality among people living with HIV (PLHIV) to the point where, with consistent access to and use of ART, they may assume a life expectancy similar to uninfected populations [1] and HIV is now often considered a chronic illness.

Furthermore, several large studies provide evidence that there is no risk of sexual transmission of HIV to others from PLHIV whose virus is supressed, summarised by the expression now used widely in HIV prevention, treatment uptake and anti-stigma campaigns, undetectable = untransmittable [2, 3], and pre-exposure prophylaxis medication provides reliable options for prevention of HIV infection [4]. The lower disease burden has lessened the impact of HIV on affected communities with consistent access to ART.

However, globally, fewer than half of all PLHIV have reliable access to ART because of major financial, logistical, cultural and political barriers to ART scale-up [5]. In addition, while ART improves immune function, it may not reverse existing negative health effects related to HIV infection.

Toxicities associated with long-term ART may also have a negative impact on health [1]. For these reasons, a cure for HIV is still considered clinically and strategically important [1].

In recent years, there has been a growing momentum in scientific research toward finding a cure for HIV infection. This has been supported by the International AIDS Society’s ‘Towards a Cure Initiative’ and other international networks focused on HIV cure research [6].

Globally, there are a number of early stage (phase I/II) clinical trials exploring potential pathways to achieve a cure for HIV. The risks and benefits of being involved in these trials have been well documented, showing that some trials present a risk to the health of PLHIV who participate due to interruption of ART for research purposes [7].

Despite this, recent studies have indicated PLHIV in high-income countries, including the United Kingdom, United States, Thailand and Australia, are likely to be motivated to participate in HIV cure research for altruistic reasons, including a desire to help future generations and/or to advance science [8–11].

A small number of studies have explored the expectations of PLHIV for the longer-term outcomes of HIV cure research [12]. In particular, studies have focused on what PLHIV perceive to be the most desired outcomes associated with an HIV cure.

For example, a study of PLHIV in the Netherlands found the most highly desired outcomes of a cure were: alleviating uncertainty about future health problems; reducing the negative social impact of HIV associated with stigma; and no longer being concerned about onward HIV transmission [13].

Similar results have been found in British and Australian studies [9, 14]. These studies highlight complexity in the way ‘HIV cure’ is defined. A cure for HIV has often been used in reference to long-term, medication-free, viral suppression (also called HIV ‘control’ or ‘remission’) [15], as well as a cure in which HIV is eliminated from the body (sometimes referred to as a ‘sterilizing’ cure) [16, 17].

These outcomes could be quite different with respect to whether PLHIV consider themselves to be cured of HIV or not, particularly if they are looking to achieve long-term certainty about their health and inability to transmit HIV, or if a cure is defined as being HIV antibody negative.

Understanding the perspectives of PLHIV on HIV cure outcomes sheds light on assumptions about, and desires for, HIV cure research held by populations who are most affected by HIV and who are likely to be involved in future observational and interventional clinical trials [12, 18].

This paper reports findings from a research project in which Australian PLHIV were interviewed about issues likely to influence their willingness to participate in clinical trials related to HIV cure research, including the perceived impact that a cure for HIV would have on their lives.

Here, we present findings focused on the personal significance of a potential HIV cure to study participants and the way that this influenced their perceptions of HIV cure research. This analysis follows on from our previous report of findings from this study on willingness to participate in HIV cure trials in Australia [11].

All participants interpreted a cure as being ‘HIV free’, i.e. elimination of HIV from the body. Being asked about how a cure for HIV would change their lives typically led participants to reflect on the impact of HIV on their lives to date as a way of identifying the likely social and psychological benefits of being HIV free.

In a separate question, participants were asked about the acceptability of other possible outcomes of cure research such as sustained viral suppression or remission. No participants considered these to be a cure for HIV. Rather, a cure was something that offered certainty that HIV would not return, their viral load would not rebound, and they could no longer transmit HIV to others. Treatments or interventions that offered less certainty were seen as welcome advances in HIV treatment, but not as a cure.

Three key themes emerged relating to the meaning and significance this definition of a cure held for participants: (1) a cure would offer certainty about future health; (2) a cure would mean an absence of everyday worry; and (3) a cure would be relief from the burden of stigma. Participants tended to hold both hope and uncertainty about the potential for a cure to be achieved.

A cure offers certainty about future health
Participants were asked what physical, emotional or life changes would need to occur for them to consider themselves cured of HIV and what impact this would have on their lives. Health, not surprisingly, was a central theme in most participants’ reflections on the benefits a cure for HIV would bring to their lives.

However, participants did not describe this as an improvement in their current state of health. Rather, a cure for HIV was seen to offer freedom from anxiety about future ill health. This was mentioned by participants who had a range of experiences with HIV, including those who were newly diagnosed and had not experienced ill health associated with their infection as well as those living with HIV longer-term.

Well, see, if a cure did become available, oh, it would remove a question I have about my survivability into the future. It would remove questions that I have about very long-term maintenance on antiretroviral therapy … So, I don’t know–well really, it would be about removing the questions about what’s going on in the future.

(Male, gay, 54, living with HIV for 25 years)

[Since] becoming HIV positive, I’ve had this general overarching concern of just getting sick, even though it doesn’t necessarily make much sense, because my viral load is very low and the agency of the HIV is quite–is pretty minimal in the affairs of my health at the moment.

(Male, gay, 23, living with HIV for four months)

Participants were looking for certainty when it came to a cure; a ‘cure’ that did not guarantee permanent viral suppression or elimination was not considered a cure because it did not offer relief from anxiety about future ill health, as one participant stated:

[A cure would mean] that I wouldn’t be worried that what if I got a flu or, you know … if you got shingles, or you know something that’s meant one of the other viruses to go a bit wild, would that set off the HIV again?

(Male, gay, 46, living with HIV for 22 years)

When questioned about their perceptions of sustained medication-free control of HIV (or remission) versus elimination of HIV, participants saw long-term control as an advance on HIV treatment rather than a cure–something that was welcomed and considered important, but without offering the same level of certainty, as the following participants stated:

Remission is not [a cure]. Cure would be knowing it can’t come back, knowing that any reservoir of HIV would not be reactivated if I ceased medication, that it would be undetectable as a HIV test in my body, not just undetectable viral load … I think that’s my stopping point around cure. It would have to be confirmed HIV negativity.

(Male, gay, 52, living with HIV for 22 years)

Do you know what that [idea of remission] makes me feel? Cheated, actually. That’s not a sufficient outcome; it’s a step towards an outcome. You know, I struggle with this as a concept with cancer. They’re in remission. They’re in remission. They’re in remission. And then the cancer’s gone. In a sense, it screams that we’ve put all the time and money and research into only getting to second base. It’s not a home run and we need the home run. We need the home run to push back against the stigma and discrimination, because second base isn’t going to cut it.

(Male, MSM, 43, living with HIV for 18 years)

Living with HIV was expressed by participants as a state of uncertainty about their future. While participants did not describe this as something they held consistently at the front of their minds, questions about what it would feel like to live without HIV evoked responses that described this sense of uncertainty, vulnerability and vigilance about their health. This sense of vulnerability was related to the knowledge of HIV being in their body rather than the physical impact of HIV or of daily ART regimens.

A cure would mean an absence of everyday worry
Participants offered complex answers to questions about the effects a cure for HIV might have on their lives beyond health. Several participants initially responded by explaining that being cured of HIV would not have a major impact on their everyday lives apart from not having to take medication.

Then, as participants thought more about the question, they identified potential social and emotional benefits. The following quotation illustrates this well:

How would [a cure] change my life? It would not change my day-to-day life to be honest because of the way I live. It would–there is an underlying fear and worry with regards to my family. My partner is not HIV positive; neither are any of my children.

Thank goodness. So–and I actually haven’t disclosed to any of my children, just because I’ve been well, and it hasn’t been necessary–and as they get older, they’ve got so much to deal with anyway just being children, that we’ve chosen not to tell them. So, in that way, it would give no relief to them.

It would be lovely not to have to take medication every day and to just have that underlying, you know, that little-voice worry if I get a cold. It still happens, you know, if something–if I don’t get better within a week, then there’s always that little worry, that niggling little fear.

I know that my mother and father would be very thankful, and they would–they’re getting older–and they would stop worrying. But day to day, you know, like, I’m not on any benefits [government financial support], I’m not–I just live quite a normal life. So, day to day, it wouldn’t affect me, but it would have a huge psychological effect on me, I’m sure, and the rest of the people who know me and worry about me.

(Female, heterosexual, 44, living with HIV for 18 years)

As is also evident in the above quotation, one desired outcome of cure for participants was relief from worry. In many participants’ responses, HIV was described as creating a psychological burden relating to anxiety about health, relationships or social interactions, and fear of onward transmission of HIV, which people held despite knowledge of the effectiveness of ART in preventing this.

[With long-term viral suppression] then I could potentially have unprotected sex and not infect anyone, have kids and, like, all of the research that’s gone into that. But, I know it’s [HIV] in my DNA, and I know I’m not cured … For me, cured is that I don’t have to think about it. And the quality of the medicine has almost put us to that point. The last step is the mental.

(Male, gay, 37, living with HIV for four months)

Well, you couldn’t imagine how much [a cure] would change my life. Not being sick isn’t the only thing. It doesn’t erase my past. It doesn’t erase the knowledge of this virus is unlike any other type of illness, and it’s like a cloud hanging over you, your whole life.

(Male, heterosexual, 43, living with HIV for 31 years)

[Being] able to pass on [HIV] is a concern as well, that’s the main fact. I guess, when it comes to my own body, I can live a fairly normal life just taking a pill a day so the biggest thing for me is being able to pass it on to someone else anyway and so yeah–the cure would hopefully mean that I am free of it that I wouldn’t have a risk of infecting someone else–that’s more my own body I guess.

(Male, heterosexual, 45 years, living with HIV for 2 years)

Participants described their view of living free from HIV as relief from tensions or burdens in their social relationships–with their families and partners. These responses are a reminder that living with HIV, is a deeply social experience. The physiological impact is only one aspect. As is evident in the quotations above, HIV that is well managed with ART presents few physical burdens and minimal interruptions to life for many people. The burden of HIV comes from its social impact. As such, the definition of a cure provided by participants was attuned to the social and relational aspects of HIV more than the physical.

A cure as relief from the burden of stigma
The impact of HIV-related stigma was implicit (and, at times explicit) in most participants’ responses to a question in how a cure for HIV would change their lives. For some, being cured of HIV–which was defined by most participants as no longer being identified as HIV positive–would alleviate the burden of stigma that comes with being seen by others as potentially ‘infectious’, as one participant explained:

[A cure for HIV] would remove that sense of being, as it were, infectious or toxic to other people …You don’t have that kind of stigma. The issue of disclosing that you’re positive, sort of, goes out of the window. And, you know, one is left in the situation where it would have been if you’d never had this illness in the sense of you’ve got to contend with whatever life throws at you in terms of aging and other circumstances, but you no longer have that stigmatized disease.

(Male, gay, 62, living with HIV for 21 years)

Look [a cure] would change my life because I wouldn’t have to be so careful about everything that’s… yeah look, the other thing is I am not open [about HIV status] with people; only close people I tell, you know. It’s that constant fear of people–because there’s a lot of misunderstanding out there in the public … Yeah, and I suppose there’s always a fear that you can get painted with a brush because of that lack of understanding–that probably would be the main thing.

I mean outside the obvious not having to take a pill a day or getting worried if you missed one of your medications doses–that’s an inconvenience more than anything else, but yeah, lifestyle, the fear of passing it on–and sexually transmitted or something like that it would be a lot of weight off your shoulders.

[Is that something you’re worried about quite often?] Yes, I am … I am married. My wife [and I], we always use condoms, but it would be nice not have to do that, and yeah, the other side of it would be that even immediate family don’t know. If they come and stay over, I am hiding all the meds and things like that. Just those two factors would be… a relief that’s off your shoulders.

(Male, heterosexual, 45, living with HIV for 2 years)

Participants described this burden of stigma in terms similar to the persistent low-level anxiety illustrated above: stigma was experienced as a daily awareness of HIV that demanded some form of emotional management to cope with negative feelings. As one participant said:

I think it’s 25 years that I’ve had HIV. I think I’ve developed lots and lots and lots of compensatory and defensive mechanisms about the fact of living with HIV. And that’s a lot to do with, I don’t know, developing resilience or realising resilience, or dealing with internalised stigma or dealing with the shame from, you know, not keeping myself negative, and I had all the lessons and choices and consequences that I’ve made.

And there’s something that I kind of underestimated about that continual low-level burden of maintaining that kind of equilibrium around that sort of stuff. And I don’t know whether cure would ameliorate that or not; but if it did, I think that would be a fine thing. Because, although I work in the sector and stuff, I don’t spend a lot of time talking about this. That’s one of my compensatory mechanisms. But sitting here talking a lot about it. I’m just kind of conscious that it is an all-pervasive kind of burden that, but even if it’s to be ignored it takes up energy to ignore it.

(Male, gay, 54, living with HIV for 20+ years)

As noted previously, the negative impact of living with HIV for many people whose HIV is well managed by ART is social more than physical. This was most apparent when participants spoke about the impact of HIV-related stigma. As can be seen in the quotations above, participants’ responses were powerful illustrations of the ways in which stigma shapes the everyday lives of many PLHIV–some people continually check or modify their emotional responses to internal feelings of shame or stigma, while others are vigilant about what friends and family see or know. Again, these findings suggest that participants’ understanding of a cure incorporates the social aspects of living with HIV.

This paper adds further dimensions to existing research on the expectations for HIV cure research held by PLHIV [13, 29, 30] by exploring the significance and understanding among Australian PLHIV of the potential impact a cure might have on their everyday lives.

In particular, these findings explicate how a cure for HIV is thought to improve the lives of PLHIV who are already in good health due to routine access to ART. For participants in this study, living with HIV brought a level of daily anxiety about social and relational complexities, stigma, and sustaining good health into the future.

ART did not fully relieve these anxieties, with many participants describing experiences of consistently ‘looking over their shoulders’ to check they were okay. This form of vigilance, particularly about future ill-health or the impact of HIV-related stigma, is an ongoing part of the experience of living with HIV for many people that has been documented in various other studies [31, 32].

Even if such worry is low level, it can be constant and wearing, negatively affecting an individual’s overall quality of life [33, 34]. A similar phenomenon in cancer is referred to by the term ‘fear of recurrence’ [35]. However, one important difference between HIV and cancer is disease transmissibility, which adds a higher level of social complexity and contributes to the stigma PLHIV experience.

The potential for HIV stigma to be relieved by biomedical treatment, including a cure for HIV, has been explored elsewhere [30, 36]. These studies have concluded that HIV-related stigma is complex and layered by other forms of discrimination, including homophobia and discrimination against injecting drug users and sex workers [30].

The way HIV is perceived in the social world is a product of social, political and historical factors, as much as it is the biological nature of the virus. A cure for HIV would obviously be a major factor shaping social understanding and attitudes toward HIV, but it would not be the only factor [37]. ART and viral suppression already mean that HIV is, for those who have access, a manageable chronic condition rather than a terminal illness.

It also means HIV is sexually untransmittable (undetectable = untransmittable, U = U) [3]. Despite this, HIV-related stigma endures in ways that have not entirely been changed by ART or U = U [37]. This was evident in this study, as participants described being burdened by fears of onward HIV transmission or negative social reactions.

Given this, a biomedical cure is unlikely to mean HIV is no longer a stigmatised condition. However elimination of the virus from the body may relieve the everyday impact of stigma. PLHIV would no longer have to live long-term with the fear, worry and vigilance that was described by participants in this study.

Participants expressed uncertainty that sustained virological suppression or remission would be sufficient to achieve this, although it would be welcomed as an important advance on existing treatment. Similar conclusions have been drawn in other studies, which have shown that PLHIV want certainty that the virus will not return before they consider themselves cured, as they mistrust virologic suppression to be sustained long term [9, 38, 39].

In this study, being cured of HIV was defined by participants as being definitively virus free–complete elimination of HIV from the body.

There has been much discussion among researchers working in the HIV cure field about the ethics of using HIV cure terminology to describe research for which a likely outcome is therapeutic interventions to achieve sustained medication-free suppression of HIV (or remission), rather than elimination of HIV from the body [16, 18, 40].

Many PLHIV may be likely to participate in research aimed toward developing therapies for medication-free viral suppression due to the benefits of reduced reliance on everyday ART [8]. However, the aspiration for HIV cure research held by participants in this study was the longer-term goal of being HIV free.

There is an ethical need to consider the ways in which HIV cure research is presented and discussed in forums such as media reporting, including the terminology used to describe trials for which elimination of HIV from the body is unlikely to be achieved in the shorter term [15].

Use of specific terminology in public and media reporting on HIV cure research will also help to ensure community expectations for HIV cure research are realistic. This is important to sustain levels of public trust and engagement in HIV science over the longer term.

The tension with this, however, is that the aspiration and language of ‘cure’ is powerful and captures attention and imagination that attracts funding and support for research. There is a challenge in maintaining energy and focus on the longer-term goal of achieving elimination of HIV from the body while also ensuring affected communities are presented with realistic expectations of shorter-term research outcomes.

Active involvement of both researchers and community advocates in the design and delivery of public messages about HIV cure research will help to ensure messages are created with due consideration to how they may be received by affected communities and PLHIV.

In this respect, fulfilling the global principle of ensuring greater and meaningful involvement of PLHIV (GIPA/MIPA) in research is politically and ethically important, but also plays a role in managing quality and accuracy of research output [41].

The findings of this study also suggest there may be value in further research to explore acceptability among PLHIV of therapeutic interventions designed explicitly to achieve sustained, medication-free, viral suppression or remission.

If PLHIV are seeking certainty with respect to viral suppression in order to allay anxiety about onward transmission and future ill health, there will need to be a high level of confidence that any new therapeutic interventions will provide this level of certainty.

These findings build on existing research about the reasons why PLHIV might be willing to take risks with their health to volunteer for HIV cure clinical trials. Various studies have shown that PLHIV in many parts of the world have expressed willingness to be involved in HIV cure research for social and altruistic motivations, including a desire to give back to communities that have supported them [8, 11, 42].

Some PLHIV already are involved in early stages of HIV research towards a cure [11, 14, 43]. There is a strong culture of support for research in all sectors of the HIV community in Australia and internationally [44, 45]. This suggests that many PLHIV are conversant with research, its processes, its strengths and limitations, and are familiar with many long-serving researchers in the HIV field.

However, HIV cure research is different from other HIV-related research in that it asks PLHIV to take a risk with their current state of good health to be part of early stage research and, potentially, threaten the gains they have achieved in securing that health for no likely clinical benefit.

For example, many HIV cure-focused clinical trials involved analytic treatment interruptions, during which participants are required to suspend ART for a period of time, and which may increase the chance of onward HIV transmission through sexual contact–something interviewees in this study were clearly concerned about [7, 46–48].

However, findings from this study show that, despite the effectiveness of modern ART, a cure for HIV would have a significant psychological and social impact on the everyday lives of PLHIV. PLHIV may consider the risks of participation in an HIV cure-related clinical trial through this lens.

Even among PLHIV who are physically healthy, there may be vulnerabilities and stressors associated with living with HIV that might reduce people’s perception of their wellbeing when weighing up risks [40]. In addition, living with everyday stressors and vulnerabilities associated with HIV may be what makes participation in research toward a possible cure meaningful and significant for PLHIV in ways that are difficult to assess objectively [42]. Again, this speaks to the importance of including PLHIV on clinical trial research teams so perspectives gained through the experience of living with HIV can inform these trials.

reference link :

More information: Mark M. Painter et al, Concanamycin A counteracts HIV-1 Nef to enhance immune clearance of infected primary cells by cytotoxic T lymphocytes, Proceedings of the National Academy of Sciences (2020). DOI: 10.1073/pnas.2008615117


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