Posted on May 17th, 2009 1 comment
17th May, 2009
[The relationship between herpes viruses and HIV disease is also discussed in a subsequent post:
The relationship between herpes simplex virus type 2 and HIV is in the news again. This time the press reports are that while acyclovir failed to suppress transmission of HIV it did cause a 17% reduction in HIV disease progression.
This reduction in disease progression was assessed by noting differences between the treated and placebo group in the numbers whose CD4 count dropped below 200, and who died. A reduction in HIV viral load was also observed in those treated with acyclovir.
The concept on which this study was based is absolutely solid.
Herpes simplex virus type 2 is the most frequent cause of genital ulcers, and the presence of genital ulcers is associated with enhanced transmission of HIV.
The failure of acyclovir to suppress HIV transmission is a disappointment, but the study should not be seen as a failure.
There is no doubt that anti herpes drugs can suppress the recurrent herpes ulceration that some individuals experience. This was observed in the study.
Herpes viruses – and not just herpes simplex virus, have an impact on the course of HIV infection. This study provides yet another demonstration that treating herpes virus infections has a beneficial effect on the course of HIV disease.
Valtrex, a drug related to acyclovir was reported to reduce HIV viral loads in infected women in 2007.
“Reduction of HIV-1 RNA Levels with Therapy to Suppress Herpes Simplex Virus” and it appeared in the New England Journal of medicine .
(NEJM 2007 356:790)
It is possible that the association of herpetic genital ulcers with HIV transmission is not as direct as generally assumed. The reasonable suppositions included the possibility that the ulcers provided a portal of entry for HIV in the uninfected partner, that there was an accumulation of CD4 cells in the ulcer that provided a good target for HIV, or even that in the infecting partner HIV was present in greater concentrations in the ulcer.
These assumptions about the reasons for increased HIV transmission may all be mistaken.
We do know with some confidence that transmission of HIV is related to viral load in the infecting partner. It may be that the assumptions outlined above derive from observing an increased frequency and duration of genital ulcers in individuals with higher viral loads who are therefore more infectious not by virtue of the ulcers.
An individual with higher HIV viral loads will more easily transmit the infection, and also experience more frequent recurrences herpetic ulcers. This of course only applies to HIV infected individuals.
As far as individuals who are not HIV infected are concerned, a direct causative association between herpetic ulcers and HIV infection may also be spurious.
Herpes simplex infections are ubiquitous but immunological mechanisms generally control the infection so that it remains latent and not manifested.
Sometimes individuals know what provokes a recurrence. Recurrences can be associated with febrile illnesses. It is completely reasonable to suggest that the effects of some intercurrent infections may cause both herpetic recurrences and increase susceptibility to HIV.
Whatever infection causes the fever may also increase susceptibility to HIV, possibly by an association of the infection with perturbed immunological function. Transient immunological perturbations can accompany many viral and tropical infections and so may not only disturb herpes simplex latency but also increase susceptibility to HIV.
For some reason, interest in the relation of HIV to herpes viruses seems to have been almost completely confined to herpes simplex virus type 2. At least regarding what is reported to the public.
However the herpes virus family includes other members which have long been thought by some – including myself, to play an important role in HIV disease.
Cytomegalovirus (CMV) and the Epstein Barr virus (EBV) are perhaps the two that are most important. These viruses are also sensitive to the anti herpes drugs used in these two trials.
Since infections with CMV and EBV are so widespread how can effects of acyclovir and Valtrex on reducing HIV viral loads be attributed to an effect of these drugs on herpes simplex type2?
I cannot recall that these two other members of the herpes virus family – or even a third, HHV6 were even mentioned in the papers demonstrating effects of acyclovir and Valtrex on HIV viral loads.
It is entirely possible that suppression of two viruses, CMV and EBV, contributed, perhaps to the greatest extent, to the anti HIV effects seen.
One can only hope that sera from these studies were frozen and stored. Such samples could provide information on an effect of these drugs t on EBV reactivation and on active CMV infections.
As an historical comment, acyclovir was tried as a treatment for AIDS in 1987 around the time AZT was introduced.
There were several studies of differing design over for some years from about 1987, some based on the hypothesis that CMV contributed to disease progression.
AZT was tried with or without acyclovir, but the results were contradictory. Interestingly AZT also inhibits EBV replication.
One study, ACTG 204, which compared two doses of acyclovir with Valtrex was stopped because 25% of those taking Valtrex died compared to 20% taking acyclovir.
Some observational studies (including the MACS study) found that there was some survival benefit among those taking acyclovir. Another retrospective observational study found no benefit.
Nothing much can be made of these contradictory early results.
But now, with newer techniques for measuring HIV activity by viral load assays, we have very clear evidence that treating herpes virus infections has a beneficial effect on HIV infection.
With the advent of the newer potent antiviral drugs, interest in anti- herpes drugs did wane, until there was a renewed interest in the past few years in connection with herpes simplex virus 2 and genital ulcer disease, Unfortunately most of the emphasis is on herpes simplex virus, when suppression of CMV and EBV may be as – or I believe, of even greater importance.
Actually there had been interest in CMV and EBV in relation to AIDS from the time the disease was first reported in 1981.
I have been involved in AIDS research and treating patients with this disease from the time it started and so can provide some historical perspective on the interest in herpes viruses, that dates to the late 1970s, even before AIDS was described and long before HIV was discovered. At this early time epidemiological studies on the prevalence of infection by CMV among sexually active gay men were undertaken in the US.
As another historical interlude, interest in herpes viruses also provided the basis for safer sex, as it is understood today. As remarkable as this may seem, the first published and disseminated proposal to use condoms to prevent the transmission of AIDS had nothing to with HIV. Condom use was proposed a few years before this virus was discovered, and had everything to do with herpes viruses, specifically CMV.
From about 1978 I had the opportunity to observe and treat a very large number of men who were to be the first to succumb to this new disease.
I knew that over 90 % of gay men attending a clinic for sexually transmitted diseases around that time had antibodies to CMV compared to 54% of heterosexual men. By 1983 over 40% of a cohort of gay men in New York City carried CMV in their semen. Amongst my patients, studies on EBV carried out by David Purtilo at the University of Nebraska showed an extraordinary high prevalence of reactivated EBV infections. (Epstein Barr Virus and chronic lymphadenopathy in make homosexuals with Acquired Immunodeficiency Syndrome. H Lipscomb et al. AIDS Research 1983 1: 59)
At that time – 1981-1982, many of the patients I was taking care of experienced reactivated EBV infections as determined by serological methods, and were excreting CMV in semen. Of course they were also infected with HIV , but this could not be known at that time.
But from what was known about CMV and EBV it was reasonable to postulate that these viruses were somehow implicated in the disease. It was thus possible to propose a way to at least prevent the sexual transmission of CMV.
This formed the basis for the first published recommendations for condom use.
With two of my patients, Michael Callen and Richard Berkowitz a booklet was written called “How to have sex in an epidemic: One approach”.
The appropriate title was coined by Richard.
The twenty fifth anniversary of the publication of this booklet, that was essentially produced and widely distributed by four individuals, and funded by a single person, went almost completely unnoticed in 2007. Although it is in fact a landmark event in the history of the epidemic.
Richard is only now receiving some acknowledgement for this life saving proposal because a documentary film called Sex Positive has brought attention to his achievement.
An account of our collaboration in producing the safer sex guidelines can be seen by following this link.
Michael Callen is remembered by many for his activism. There is even a clinic in New York City named for him and Audre Lorde .
I actually worked there as a physician for a short period, and with very few exceptions, the health care providers and others working there had no idea of who he was, let alone his contribution to safer sex.
I just visited the Callen Lorde website, and indeed there is a photograph of Michael and of Audre Lorde with a few words about each, but no mention of Michaels contribution to safer sex.
Thus herpes viruses, at least CMV had a role in the development of safer sex recommendations.
As it turns out herpes viruses – CMV and EBV included, have a great deal to do with AIDS. This is quite apart from their multiple clinical manifestations as opportunistic pathogens. Both of these viruses almost definitely contribute to pathogenesis.
Evidence that some herpes viruses can play a critical role in HIV disease progression has accumulated for many years.
In fact some evidence for this was already apparent when AIDS was first described.
This considerable body of evidence did not disappear with the discovery of HIV, but was relatively neglected.
As work on HIV proceeded we gained some understanding of the ways in which herpes viruses can interact with HIV to accelerate disease progression, increase HIV infectivity and thus enhance its transmission.
I should now describe some of the interactions that exist between herpes viruses, particularly CMV and EBV, and HIV.
Many, perhaps most of these interactions also involve herpes simplex viruses types 1 and 2.
The role of CMV in immune system activation, a major force in driving HIV infection.
The systemic effects of CMV and EBV infections are most probably of great importance in this respect.
Systemic effects resulting in immune system activation and activation of HIV replication may also accompany reactivated herpes simplex virus infecteions.
Among the systemic effects of active herpes virus infections are the secretion of pro inflammatory cytokines. These circulate and attach to specific receptors on the cell surface. A consequence of this is that certain sequences on DNA will be activated resulting in the transcription of HIV DNA and ultimately the production of new HIV particles. So, this is but one way in which an active herpes virus infections can promote the replication of HIV. The general mechanisms are described in a previous post..
An important and interesting paper that also deals with EBV and CMV in relation to HIV replication was published by V Appay and colleagues. It can be seen by clicking the following link.
I am reproducing some excerpts from Dr Appay’s paper here as the descriptions are very clear and there are references. The references can be seen in the complete text seen by following the above link.
“HIV-1 also causes immune activation and inflammation through indirect means. Antigenic stimulation during HIV-1 infection may be induced by other viruses, such as CMV and EBV”
“In addition, inflammatory conditions occurring during HIV infection (eg release of proinflammatory cytokines) may also participate in
the reactivation of latent forms of CMV and EBV. Recent studies have shown significant activation of EBV- and CMV-specific CD8+ T cells during HIV-1 acute infection [40,41] . Hence, sustained
antigen mediated immune activation occurs in HIV-1-infected
patients, which is due to HIV-1, but also to other viruses (and may be restricted to CMV and EBV)”.
“CMV has been associated with strong and persistent expansions of T cell subsets that show characteristics of late differentiation and replicative exhaustion [94-96]. The anti-CMV response appears
to monopolize a significant fraction of the whole T cell repertoire , so that it might compromise the response to other antigens by shrinking the remaining T cell repertoire and reducing T cell diversity. CMV infection is actually extremely common in HIV-1- infected individuals and its recurrent reactivation may put further stress on their immune resources. Interestingly, CMV-seropositive subjects generally experience more rapid HIV disease progression than CMV seronegative subjects “.
Herpes virus (including herpes simplex) infected cells express Fc receptors on their surface. These receptors can bind certain sequences on antibody molecules. If these antibodies are attached to HIV, a portal for entry of HIV is provided on herpes infected cells that do not possess CD4 molecules on their surface. This process has in fact been demonstrated.
Transactivation of HIV by herpes viruses.
In cells infected with both viruses herpes virus gene products can activate HIV and promote its replication. The transactivation is reciprocal as HIV can promote herpes virus replication.
In the early 1980s when we had no effective measures against this disease I treated my patients with high dose acyclovir.
There then was evidence, albeit theoretical and indirect for a role for these viruses in this new disease.
In the absence of clear evidence from clinical studies, and given the gravity of the disease, it seemed completely appropriate to be guided by these theoretical considerations, particularly involving a drug that is so free of toxicity.
But interestingly, at that time, none of these theoretical considerations placed much importance on HSV 2.
The practice of medicine in those years, dealing with such a mysterious and deadly disorder of unknown causation , demanded responses that could only be based on one’s best judgment.
Fortunately I also had had some experience in the transplant field and was also able to provide bactrim to my patients years before recommendations for its use were issued.
But it was not until potent antiviral drugs became available that we were able to make significant and life saving, rather than life extending interventions.
What I have written of this experience with bactrim in the early years can be seen by following this LINK
In the light of later evidence, I believe it is possible I was able to provide some small benefit in prescribing high dose acyclovir in those very early years.
[i] Acyclovir, when phosphate is added to it, acts like the nucleoside analogues active against HIV, drugs like AZT, D4T, 3TC etc. But this drug has a truly remarkable quality. The cellular enzyme that adds phosphate to make drugs of this type active, does not work on acyclovir as it does on AZT, 3TC and other anti HIV nucleoside analogues. But an enzyme, thymidine kinase that is encoded by herpes viruses, and therefore only appears in herpes virus infected cells has the ability to add the phosphate group and turn acyclovir into an active drug. This is the reason why acyclovir is such a safe drug. It only disrupts DNA synthesis in herpes virus infected cells, where of course this effect is desirable; it has no effect on uninfected cells.
However, if the same cell happens to be infected with HIV and a herpes virus, the herpes thymidine kinase will phosphorylate acyclovir, which now can work to terminate HIV DNA synthesis just as 3TC , AZT and similar drugs do when phosphorylated by the cellular enzyme.
This effect , only observed in doubly infected cells in the laboratory is unlikely to be of much significance in the body.