**7. A search for functional cure: Is it functional or sterilising cure?**

There is currently no cure for HIV/AIDS, but recent research interest on HIV treatment tends to focus on functional cure which has renewed optimism for HIV cure. The aim of the functional cure is to get rid of all viruses from the system and remove any negative effects of HIV on the body and prevent viral rebound after discontinuation of the antiviral treatment. In other words, people who had been functionally cured would never develop AIDS or other signs of HIV disease as classified by WHO [16] and US CDC [17, 18]. Current HIV themes are now focused on this approach to solve the problem of HIV infection globally.

This type of *HIV cure* does not translate to eradicating all viruses from the body but being able to control viremia without antiviral drugs [108]. The difference between a functional cure or remission and eradication/sterilisation cure is that while the former may de-emphasise the HIV viral reservoir clearance and establish a sufficiently strong immune response with lowthe problem of HIV infection globally.

level viremia at <50 copies/ml, the latter sees it as a central task to eliminate the virus from all body compartments with a plasma HIV RNA count of <1 copy/ml. In addition, the reservoir is significantly smaller in elite controllers with decreased concentration of HIV DNA. Viral reservoir is simply different areas of the body where viral copies hide quietly and undetected and are unable to be treated until they are stimulated or activated to reproduce. Anatomical reservoirs include the gastrointestinal tract (GIT), lymphoid tissue and the central nervous system (CNS). These compartments may harbour unique long-lived latently infected cells, and penetration of cART may be limited at these sites. What are the phenotypic characteristics of functional cure? First is the undetectable or very low noninfective levels of the virus (<50 copies/ml) though some authors suggested <75 copies/ml for six months [109], and second is a normal range of CD4 cell count when cART is discontinued. Although cART have tremen‐ dously improved the lives of individuals with HIV, they come with significant side effects, perhaps not the ideal functional cure which would get HIV-infected patients to the point where cART are no longer needed to keep their infections under control. while the former may de-emphasise the HIV viral reservoir clearance and establish a sufficiently strong immune response with low-level viremia at <50 copies/ml, the latter sees it as a central task to eliminate the virus from all body compartments with a plasma HIV RNA count of <1 copy/ml. In addition, the reservoir is significantly smaller in elite controllers with decreased concentration of HIV DNA. Viral reservoir is simply different areas of the body where viral copies hide quietly and undetected and are unable to be treated until they are stimulated or activated to reproduce. Anatomical reservoirs include the gastrointestinal tract (GIT), lymphoid tissue and the central nervous system (CNS). These compartments may harbour unique long-lived latently infected cells, and penetration of cART may be limited at these sites. What are the phenotypic characteristics of functional cure? First is the undetectable or very low noninfective levels of the virus (<50 copies/ml) though some authors suggested <75 copies/ml for six months [109], and second is a normal range of CD4 cell count when cART is discontinued. Although cART have tremendously improved the lives of individuals with HIV, they come with significant side effects, perhaps not the ideal functional cure which would get HIV-infected patients to the point where cART are no longer needed to keep their infections under control.

remove any negative effects of HIV on the body and prevent viral rebound after discontinuation of the antiviral treatment. In other words, people who had been functionally cured would never develop AIDS or other signs of HIV disease as classified by WHO [16] and US CDC [17, 18]. Current HIV themes are now focused on this approach to solve

antiviral drugs [108]. The difference between a functional cure or remission and eradication/sterilisation cure is that

**Figure 1.** Schematic diagram representing a putative mechanistic model of oxidative stress (OS) activity in elite con‐ trollers and in HIV disease progression. (Consequences of oxidant/antioxidant activation in the different stages of HIV infection and interrelationship between OS and HIV control. OS= oxidative stress, ARE= antioxidant responsive ele‐ ment.)

#### Figure 1. Implication of oxidative stress (OS) in elite controllers and in HIV disease progression. (Consequences of oxidant/antioxidant activation in the different stages of HIV infection and interrelationship between OS and HIV control. OS= oxidative stress, ARE= **8. Oxidative stress regulation of elite controllers: A reality or a hoax of functional cure**

antioxidant responsive element.) **8. Oxidative stress regulation of elite controllers: A reality or a hoax of functional cure** It seems certain that oxidative stress control of HIV elite controllers may contribute to the expected functional cure in HIV patients (Fig. 1). Examination of possible and established cases implicates the action of redox control instead as an approach for the cure. But is this a mis‐ conceived theory or a deception?

approach for the cure. But is this a misconceived theory or a deception?

It seems certain that oxidative stress control of HIV elite controllers may contribute to the expected functional cure in HIV patients (Fig. 1). Examination of possible and established cases implicates the action of redox control instead as an

Epidemiology of elite or aviremic control of HIV infection appears to occur in approximately 1 in 300 HIV-infected persons and represents a distinct phenotype among HIV-infected individuals [110]. Through a recently established international collaboration (HIV Controller Consortium), over 300 elite controllers have been identified and recruited for study [111]. Achieving either a functional cure (long-term control of HIV in the absence of cART) or a sterilising cure (elimination of all HIV-infected cells) still remains a major challenge to scientists. As noted previously, establishment of a latent or 'silent' infection in resting CD4+ T-cells is a major impediment to finding HIV cure. Several randomised clinical trials have shown that treatment intensification even with additional ART has little impact on latent reservoirs. Some potential drugs used to reduce latency, including histone deacetylase inhibitors, currently used and licensed for the while the former may de-emphasise the HIV viral reservoir clearance and establish a sufficiently strong immune response with low-level viremia at <50 copies/ml, the latter sees it as a central task to eliminate the virus from all body compartments with a plasma HIV RNA count of <1 copy/ml. In addition, the reservoir is significantly smaller in elite controllers with decreased concentration of HIV DNA. Viral reservoir is simply different areas of the body where viral copies hide quietly and undetected and are unable to be treated until they are stimulated or activated to reproduce. Anatomical reservoirs include the gastrointestinal tract (GIT), lymphoid tissue and the central nervous system (CNS). These compartments may harbour unique long-lived latently infected cells, and penetration of cART may be limited at these sites. What are the phenotypic characteristics of functional cure? First is the undetectable or very low noninfective levels of the virus (<50 copies/ml) though some authors suggested <75 copies/ml for six months [109], and second is a normal range of CD4 cell count when cART is discontinued. Although cART have tremendously improved the lives of individuals with HIV, they come with significant side effects, perhaps not the ideal functional cure which would get Epidemiology of elite or aviremic control of HIV infection appears to occur in approximately 1 in 300 HIV-infected persons and represents a distinct phenotype among HIV-infected individuals [110]. Through a recently established international collaboration (HIV Controller Consortium), over 300 elite controllers have been identified and recruited for study [111]. Achieving either a functional cure (long-term control of HIV in the absence of cART) or a sterilising cure (elimination of all HIV-infected cells) still remains a major challenge to scientists. As noted previously, establishment of a latent or 'silent' infection in resting CD4+ Tcells is a major impediment to finding HIV cure. Several randomised clinical trials have shown that treatment intensification even with additional ART has little impact on latent reservoirs. Some potential drugs used to reduce latency, including histone deacetylase inhibitors, currently used and licensed for the treatment of some cancers, methylation inhibitors, cytokines such as IL-7 or activators of NF-κB such as prostratin, show promising activity in reversing latency in vitro when used either alone or in combination [112]. Prodrugs provoked through ferrocene-mediated oxidation currently have been developed to enhance the selec‐ tivity and specificity of anticancer drugs. Peng et al. [113] described how the strategies of ROS activation can be employed for further development of new ROS-targeting prodrugs, which must eventually lead to novel approaches and/or combined technology for more efficient and selective treatment of cancers.

level viremia at <50 copies/ml, the latter sees it as a central task to eliminate the virus from all body compartments with a plasma HIV RNA count of <1 copy/ml. In addition, the reservoir is significantly smaller in elite controllers with decreased concentration of HIV DNA. Viral reservoir is simply different areas of the body where viral copies hide quietly and undetected and are unable to be treated until they are stimulated or activated to reproduce. Anatomical reservoirs include the gastrointestinal tract (GIT), lymphoid tissue and the central nervous system (CNS). These compartments may harbour unique long-lived latently infected cells, and penetration of cART may be limited at these sites. What are the phenotypic characteristics of functional cure? First is the undetectable or very low noninfective levels of the virus (<50 copies/ml) though some authors suggested <75 copies/ml for six months [109], and second is a normal range of CD4 cell count when cART is discontinued. Although cART have tremen‐ dously improved the lives of individuals with HIV, they come with significant side effects, perhaps not the ideal functional cure which would get HIV-infected patients to the point where

HIV-infected patients to the point where cART are no longer needed to keep their infections under control.

**8. Oxidative stress regulation of elite controllers: A reality or a hoax of functional cure**

**Figure 1.** Schematic diagram representing a putative mechanistic model of oxidative stress (OS) activity in elite con‐ trollers and in HIV disease progression. (Consequences of oxidant/antioxidant activation in the different stages of HIV infection and interrelationship between OS and HIV control. OS= oxidative stress, ARE= antioxidant responsive ele‐

**8. Oxidative stress regulation of elite controllers: A reality or a hoax of**

It seems certain that oxidative stress control of HIV elite controllers may contribute to the expected functional cure in HIV patients (Fig. 1). Examination of possible and established cases implicates the action of redox control instead as an approach for the cure. But is this a mis‐

It seems certain that oxidative stress control of HIV elite controllers may contribute to the expected functional cure in HIV patients (Fig. 1). Examination of possible and established cases implicates the action of redox control instead as an

Epidemiology of elite or aviremic control of HIV infection appears to occur in approximately 1 in 300 HIV-infected persons and represents a distinct phenotype among HIV-infected individuals [110]. Through a recently established international collaboration (HIV Controller Consortium), over 300 elite controllers have been identified and recruited for study [111]. Achieving either a functional cure (long-term control of HIV in the absence of cART) or a sterilising cure (elimination of all HIV-infected cells) still remains a major challenge to scientists. As noted previously, establishment of a latent or 'silent' infection in resting CD4+ T-cells is a major impediment to finding HIV cure. Several randomised clinical trials have shown that treatment intensification even with additional ART has little impact on latent reservoirs. Some potential drugs used to reduce latency, including histone deacetylase inhibitors, currently used and licensed for the

remove any negative effects of HIV on the body and prevent viral rebound after discontinuation of the antiviral treatment. In other words, people who had been functionally cured would never develop AIDS or other signs of HIV disease as classified by WHO [16] and US CDC [17, 18]. Current HIV themes are now focused on this approach to solve

cART are no longer needed to keep their infections under control.

194 Trends in Basic and Therapeutic Options in HIV Infection - Towards a Functional Cure

approach for the cure. But is this a misconceived theory or a deception?

the problem of HIV infection globally.

antioxidant responsive element.)

**functional cure**

conceived theory or a deception?

ment.)

The major reason why HIV cannot be cured is the persistence of HIV in a latent form in different cellular reservoirs which may be pre- or post-integration latency. Functional cure strategies tend to reduce effects of this latency. The case report of a German patient with acute myeloid leukaemia, who received a bone marrow transplant from a donor with a 32-base pair deletion in the CCR5 gene, may remain the only current example of a sterilising cure [114]. After transplantation, the patient discontinued cART for 45 months and HIV RNA remained at below 1 copy/ml with no virus found in reservoir compartments. However, a strategy of using bone marrow transplantation with a CCR5 mutant donor is not a realistic cure for HIV, given the toxicity and complexity of the treatment. Similarly, Sangamo Biosciences used zinc finger nucleases, a genome editing technique, to cut off the gene in CD4 cells that controls the expression of CCR5 coreceptor which the virus uses to enter cells, based on the coreceptor theory [115,116]. The data generated from the clinical trials with the drug SB-728-T showed control of viremia, improved CD4 cells and reduced proviral reservoirs with no safety concerns; these were sustained for 56 weeks after disruption of treatment [117,118]. How costeffective this treatment and its availability to the large population of HIV patients remain to be answered.

Figure 1. Implication of oxidative stress (OS) in elite controllers and in HIV disease progression. (Consequences of oxidant/antioxidant activation in the different stages of HIV infection and interrelationship between OS and HIV control. OS= oxidative stress, ARE= There is a possibility that other cases of remission or functional cure exist in patient populations globally who may have started treatment soon after infection. But the figures are not certain on the proportion of these populations that experience functional cure, though some experts have speculated one in seven people. To date, HIV functional cure has not been 100 % successful. In 2010, the Mississippi baby (treatment started early) believed to be functionally cured of HIV after two years of treatment discontinuation now has detectable levels of the virus in her blood [119], though this paved way for rational very early treatment in perinatal HIV infection [120]. Similarly, a German patient who initiated antiretroviral therapy with AZT, 3TC and efavirenz just under three months after exposure to HIV and within one month of confirmed seroconversion, after an acute viral illness had his viral load below limit of detection with stable range of CD4 cell (900–1,000 cells/mm3 ). He has shown no HIV RNA or associated proteins in any tissue/organ compartment after treatment interruption for nine years [121]. This case shows evidence of strong and broad CD8 T-cell responses and strong proliferative CD4 T-cell responses. What might be responsible for this? In contrast, analysis of the CCR5 coreceptor showed that the homozygous CCR5 promoter A59029G was present, but no delta 32 deletion was observed [121] and the HLA-I subtype was A 01, 02 B:44, 52. Nevertheless, HIV was recovered later from the patients using a humanised mouse model after transplan‐ tation of the patient's purified CD4 T-cells and anti-CD3/anti-CD28 stimulation. This indicated the presence of HIV capable of replication and that other factors other than CCR5 mutation may be responsible for viral control. The French VISCONTI cohort study also reported patients who started treatment early and was able to gain control of the virus replication with unde‐ tected viral load after six years of treatment interruption [122]. A period of at least four years of treatment is suggested prior to treatment interruption [123].

In most studies, preferential attention has been given to latent resting CD4+ T-lymphocytes as a source of HIV persistence in the cell and CCR5 coreceptor mutation as responsible for HIV control. While explanations for functional cure have proved inadequate, ROS has been demonstrated to contribute to disease progression and drug design [124]. New strategies for HIV functional cure should incorporate use of ROS-activated prodrugs [113]. Adequate data on OS condition of spontaneous controllers (natural resistance) and the posttreatment controllers (PTC)/functional cure are not available. Luc Montagner, codiscoverer of the HIV, identified oxidative stress as one of the four factors responsible for its variability [125]. Besides, recent report that P13K/Akt inhibitors can drastically sensitise HIV-infected macrophages (reservoir) to oxidative-stress-induced cell death [126] indicates possible ROS therapeutic approach to achieve HIV cure as well as the cytoprotective effect of the virus-activated P13K/ AKt in human microglial cell line and macrophages against apoptotic challenge [127]. In addition, HIV infection increases the cellular levels of ROS, especially superoxide anion and peroxynitrite which accelerates HIV replication in macrophages [28]. Recently, Bhaskar et al. demonstrated that a marginal increase of about ~25mV in *E*GSH is sufficient to switch HIV-1 from latency to reaction using Grx1-roGFP2 biosensor [128], suggesting possibility of purging HIV-1 by redox modulators which shows how fluctuations in *E*GSH modulate expression of antioxidant gene in infected HIV patients [129].
