Assessment of the toxicity of different antiretroviral drugs and their combinations on Sertoli and Leydig cells

The human immunodeficiency virus continues to pose a significant global public health challenge, affecting millions of individuals. The current treatment strategy has incorporated the utilization of combinations of antiretroviral drugs. The administration of these drugs is associated with many deleterious consequences on several physiological systems, notably the reproductive system. This study aimed to assess the toxic effects of abacavir sulfate, ritonavir, nevirapine, and zidovudine, as well as their combinations, on TM3 Leydig and TM4 Sertoli cells. The cell viability was gauged using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) and neutral red uptake (NRU) assays. Reactive oxygen species (ROS) production was assessed via the 2',7'-dichlorofluorescein diacetate (DCFDA) test, and DNA damage was determined using the comet assay. Results indicated cytotoxic effects at low drug concentrations, both individually and combined. The administration of drugs, individually and in combination, resulted in the production of ROS and caused damage to the DNA at the tested concentrations. In conclusion, the results of this study suggest that the administration of antiretroviral drugs can lead to testicular toxicity by promoting the generation of ROS and DNA damage. Furthermore, it should be noted that the toxicity of antiretroviral drug combinations was shown to be higher compared to that of individual drugs.

Detection of unreported usage of the antiretroviral drug lamivudine in two blood donors

BACKGROUND

Unreported HIV antiretroviral (ARV) drug usage by blood donors compromises the ability to detect evidence of HIV infection in blood screening tests and represents a risk for blood transfusion safety. Our objective was to determine the frequency of undeclared ARV drug use by blood donors with altered HIV markers.

STUDY DESIGN AND METHODS

This was a retrospective cross-sectional analysis of donations that were tested for HIV antibody (ab), antigen (ag), and RNA by chemiluminescent immunoassay and nucleic acid screening tests. Positive samples were retested and were subjected to ARV drug testing by high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

Of 345,252 blood donations, 361 (0.1%) were positive on initial testing. Samples from 296 (81.9%) of these donations were available for further analysis. The presence of HIV ab/ag and/or RNA was confirmed in 83 (28.0%) of these samples. All 296 bloods were subjected to ARV testing. The ARV drug lamivudine, at 11.3 and 6.7 ng/mL, was detected in 2 of 83 (2.4%) donations that were HIV positive. Other drugs were not detected.

CONCLUSION

Unreported ARV usage was identified in two candidates for blood donation. More intensive efforts to educate donors about disclosure and to investigate the extent of this phenomenon in Brazil are needed.

Combined Nano-Vector Mediated-Transfer to Suppress HIV-1 Infection with Targeted Antibodies in-vitro

Introduction

Broadly neutralizing antibodies (bNAbs) have the ability to neutralize a considerable breadth of genetically diverse human immunodeficiency virus (HIV) strains. Passive immunization can potentially provide protection against HIV infection in animal models. However, the direct antibody infusion effect is limited due to the short half-life and deficient immunogenicity of the antibody. As an alternative strategy, we propose the use of nano viral vectors, specifically the adeno-associated virus (AAV), to continuously and systematically produce bNAbs against HIV.

Methods

Plasmids expressing bNAbs PG9, PG16, 10E8, and NIH45-46 antibodies were constructed, targeting three different epitopes of HIV. Additionally, the bNAbs gene mediated by rAAV8 was administered to generate long-term expression with a single injection. We established both single and combined immunization groups. The neutralizing activity of antibodies expressed in mice sera was subsequently evaluated.

Results

The expression of bNAbs in BALB/c mice can last for >24 weeks after a single intramuscular injection of rAAV8. Further studies show that neutralization of the HIV pseudovirus by sera from co-immunized mice with rAAV8 expressing 10E8 and PG16 was enhanced compared with mice immunized with 10E8 or PG16 alone.

Conclusion

The prolonged expression of neutralizing antibodies can be maintained over long periods in BALB/c mice. This combined immunization is a promising candidate strategy for HIV treatment.

Transitioning Long-Acting Products to a Generic Marketplace: What's Missing?

Development of and increased access to generic oral medications to treat high-burden diseases including human immunodeficiency virus (HIV), tuberculosis, viral hepatitis, and malaria have had a major impact on reducing global morbidity and mortality. However, access and adherence to these life-saving treatments remains limited for some of the most vulnerable and underserved populations, for whom stigma, control, and discretion are critical to decisions around care. Current efforts to develop long-acting formulations to treat and prevent these conditions could overcome many of these barriers. However, generic manufacturing of these innovative products will be required to ensure affordable access to the communities and patients in greatest need. Strategic investments in new infrastructure will be required even before markets and manufacturing costs are clear, to ensure that access to these new products is not delayed, particularly for patients in low- and middle-income countries. Unlike conventional oral medications, long-acting products require greater investment for formulation, packaging, and delivery. The requirement for long-term bioequivalence studies will introduce additional delays in regulatory approval of generic long-acting products, and expedited approval pathways must be developed. Lessons learned from the development of long-acting hormonal contraceptives and long-acting antiretroviral products may provide a way forward.

The LEAP Process: Streamlining the Development of Long-Acting Products and Formulations for Infectious Diseases

Developing long-acting products and formulations for infectious diseases is a nontrivial undertaking that is frequently classified as high risk and low reward by the pharmaceutical industry. The Long-Acting/Extended Release Antiretroviral Research Resource Program (LEAP) was founded in 2015 with the support of the National Institutes of Health to encourage, promote, and accelerate the development of such products. Assessment methodology for any new proposal brought to this group is part of a framework-the LEAP Process-that includes a landscape analysis of what is currently available in the public domain. This is followed by in silico modeling and simulation offered as a service to the relevant scientific community. A variety of preclinical and clinical outcome metrics are applied to each new agent as part of a continuous feedback loop to improve product characteristics. This allows us to catalog knowledge gaps and barriers that can be addressed by engaged stakeholders. Results are communicated in scientific articles, reviews, and position papers. This undertaking serves to de-risk discovery, development, and implementation by bridging the gaps between academic, regulatory, and industrial investigators, and by engaging those in the community who will be the eventual users of these medicines. The LEAP Process has supported formulations now approved for human immunodeficiency virus, as well as products in clinical and preclinical development for tuberculosis and hepatitis viruses B and C.

Transfusion-Acquired HIV: History, Evolution of Screening Tests, and Current Challenges of Unreported Antiretroviral Drug Use in Brazil

Prevention of HIV acquisition by blood transfusion from its emergence to the present day is reviewed, and current challenges are delineated. The experience of Fundação Pró-Sangue/Hemocentro de São Paulo, Brazil, is highlighted in the quest for improvements in blood safety and the evolution of increasingly sensitive and specific screening tests. Concerns and establishing stringent criteria in the screening of potential blood donors are emphasized, and the current criteria for identifying and deferring candidates at high risk of acquiring sexually transmitted diseases are summarized. Future challenges relate to the identification of donors with unreported use of antiretroviral drugs for prophylaxis against possible HIV exposure or for treatment of an HIV infection whose viral expression is undetectable by current analyses. There is a need to better understand the motivation of HIV-exposed donors and to educate them about the risk of transfusion-mediated HIV transmission despite having low or undetectable viral loads. In situations in which traditional HIV RNA or antibody detection assays remain negative, more sensitive analyses are needed to identify potential donors at risk for HIV transmission.

Bioactive Effects of Curcumin in Human Immunodeficiency Virus Infection Along with the Most Effective Isolation Techniques and Type of Nanoformulations

Human immunodeficiency virus (HIV) is one of the leading causes of death worldwide, with African countries being the worst affected by this deadly virus. Curcumin (CUR) is a Curcuma longa-derived polyphenol that has attracted the attention of researchers due to its antimicrobial, anti-inflammatory, antioxidant, immunomodulatory and antiviral effects. CUR also demonstrates anti-HIV effects by acting as a possible inhibitor of gp120 binding, integrase, protease, and topoisomerase II activities, besides also exerting a protective action against HIV-associated diseases. However, its effectiveness is limited due to its poor water solubility, rapid metabolism, and systemic elimination. Nanoformulations have been shown to be useful to enhance curcumin’s bioavailability and its effectiveness as an anti-HIV agent. In this sense, bioactive effects of CUR in HIV infection are carefully reviewed, along with the most effective isolation techniques and type of nanoformulations available.

HIV/AIDS Curable Study: New Forms of Therapeutic Trinity

BACKGROUND AND AIMS

AIDS (acquired immune deficient syndrome), a deadly human infectious disease is caused by HIV (human immunodeficiency viruses) infection. Patient's mortality was eventually reduced to one-fourth by combined chemotherapy (usually 3 chemical drugs simultaneously) than earlier HIV/AIDS treatments (single drug or vaccine) in the clinic.

RESULTS

Combined treatments against HIV/AIDS are still incurable for all patients despite a high rate of patient's survival. Basic viral pathological study and advancing drug development systems for curable medications are indispensable nowadays and in the future.

CONCLUSION

Up to date, therapeutic trinity (combined therapy) against HIV/AIDS is generally among chemical drugs. In this article, several forms of other therapeutic attempts for effectively curing efforts against HIV/AIDS are proposed-including the development of next generation therapeutic HIV vaccines and schedules, new categories of bio-therapy, different pathways of immune-modulation, herbal medicines in general (allopathic, Ayurveda and traditional Chinese medicines), high quality of physical exercises, and especially therapeutic combinations guided by latest medical discovery and principles (new forms of therapeutic trinity against HIV-induced pathogenesis and human mortality).

The Ambiguous Roles of Extracellular Vesicles in HIV Replication and Pathogenesis

Cells from all kingdoms of life can release membrane-enclosed vesicles to the extracellular milieu. These extracellular vesicles (EVs) may function as mediators of intercellular communication, allowing the transfer of biologically active molecules between cells and organisms. It has become clear that HIV particles and certain types of EVs, such as exosomes, share many similarities regarding morphology, composition, and biogenesis. This review presents a summary of the literature describing the intricate relationship between HIV and EVs biogenesis. Also, we discuss the latest progress toward understanding the mechanisms by which EVs influence HIV pathogenesis, as well as, how HIV modulates EVs composition in infected cells to facilitate viral spread.

Reduced Chronic Lymphocyte Activation following Interferon Alpha Blockade during the Acute Phase of Simian Immunodeficiency Virus Infection in Rhesus Macaques

Pathogenic human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) infection of humans and rhesus macaques (RMs) induces persistently high production of type I interferon (IFN-I), which is thought to contribute to disease progression. To elucidate the specific role of interferon alpha (IFN-α) in SIV pathogenesis, 12 RMs were treated prior to intravenous (i.v.) SIV_mac239 infection with a high or a low dose of an antibody (AGS-009) that neutralizes most IFN-α subtypes and were compared with six mock-infused, SIV-infected controls. Plasma viremia was measured postinfection to assess the effect of IFN-α blockade on virus replication, and peripheral blood and lymphoid tissue samples were analyzed by immunophenotypic staining. Consistent with the known antiviral effect of IFN-I, high-dose AGS-009 treatment induced a modest increase in acute-phase viral loads versus controls. Four out of 6 RMs receiving a high dose of AGS-009 also experienced an early decline in CD4⁺ T cell counts that was associated with progression to AIDS. Interestingly, 50% of the animals treated with AGS-009 (6/12) developed AIDS within 1 year of infection compared with 17% (1/6) of untreated controls. Finally, blockade of IFN-α decreased the levels of activated CD4⁺ and CD8⁺ T cells, as well as B cells, as measured by PD-1 and/or Ki67 expression. The lower levels of activated lymphocytes in IFN-α-blockaded animals supports the hypothesis that IFN-α signaling contributes to lymphocyte activation during SIV infection and suggests that this signaling pathway is involved in controlling virus replication during acute infection. The potential anti-inflammatory effect of IFN-α blockade should be explored as a strategy to reduce immune activation in HIV-infected individuals.IMPORTANCE Interferon alpha (IFN-α) is a member of a family of molecules (type I interferons) that prevent or limit virus infections in mammals. However, IFN-α production may contribute to the chronic immune activation that is thought to be the primary cause of immune decline and AIDS in HIV-infected patients. The study presented here attempts to understand the contribution of IFN-α to the natural history and progression of SIV infection of rhesus macaques, the primary nonhuman primate model system for testing hypotheses about HIV infection in humans. Here, we show that blockade of IFN-α action promotes lower chronic immune activation but higher early viral loads, with a trend toward faster disease progression. This study has significant implications for new treatments designed to impact the type I interferon system.

Bone marrow stem cells to destroy circulating HIV: a hypothetical therapeutic strategy

Human immunodeficiency virus (HIV) still poses enigmatic threats to human life. This virus has mastered in bypassing anti retroviral therapy leading to patients’ death. Circulating viruses are phenomenal for the disease outcome. This hypothesis proposes a therapeutic strategy utilizing receptor-integrated hematopoietic, erythroid and red blood cells. Here, HIV specific receptors trap circulating viruses that enter erythrocyte cytoplasm and form inactive integration complex. This model depicts easy, effective removal of circulating HIV without any adverse effect.

The impact of antiretroviral therapy in resource-limited settings and current HIV therapeutics

Four million people of the global total of 35 million with HIV infection are from South-East Asia. ART is currently utilized by 15 million people and has led to a dramatic decline in the mortality rate, including those in low- and middle-income countries. A reduction in sexually transmitted HIV and in comorbidities including tuberculosis has also followed. Current recommendations for the initiation of antiretroviral therapy in people who are HIV+ are essentially to initiate ART irrespective of CD4 cell count and clinical stage. The frequency of HIV testing should be culturally specific and based on the HIV incidence in different key populations but phasing in viral load technology in LMIC is an urgent priority and this needs resources and capacity. With the availability of simplified potent ART regimens, persons with HIV now live longer. The recent WHO treatment guidelines recommending routine HIV testing and earlier initiation of treatment should be the stepping stone for ending the AIDS epidemic and to meet the UNAIDS mission of 90*90*90.

Novel approaches to HIV therapy

There are approximately 35 million people infected by human immunodeficiency virus (HIV), with an estimated 2 million incident infections annually across the globe. While HIV infection was initially associated with high rates of morbidity and mortality, advances in therapy have transformed it into a chronic and manageable disease. In addition, there is very strong evidence that those on antiretroviral therapy are much less likely to transmit infection to their partners. The success rates for maintaining viral suppression in treated patients has dramatically increased owing to the development of agents that are potent and well tolerated and can often be co-formulated into single pills for simplification. This review will outline advances in treatment over the last several years as well as new strategies that may shift the existing treatment paradigm in the near future.

Exosomes in HIV infection: A review and critical look

Exosomes are nanovesicles released into the extracellular medium by different cell types. These vesicles carry a variety of protein and RNA cargos, and have a central role in cellular signaling and regulation. A PubMed search using the term "exosomes" finds 67 articles published in 2006. Ten years later, the same search returns approximately 1200 results for 2016 alone. The growing interest in exosomes within the scientific community reflects the different roles exerted by extracellular vesicles in biological systems and diseases. However, the increase in academic production addressing the biological function of exosomes causes much confusion, especially where the focus is on the role of exosomes in pathological situations. In this review, we critically interpret the current state of the research on exosomes and HIV infection. It is plausible to assume that exosomes influence the pathogenesis of HIV infection through their biological cargo (primarily membrane proteins and microRNAs). On the other hand, evidence for a usurpation of the exosomal budding and trafficking machinery by HIV during infection is limited, although such a mechanism cannot be ruled out. This review also discusses several biological aspects of exosomal function in the immune system. Finally, the limitations of current exosome research are pointed out.

Chimeric antigen receptor engineered stem cells: a novel HIV therapy

Despite the success of combination antiretroviral therapy (cART) for suppressing HIV and improving patients' quality of life, HIV persists in cART-treated patients and remains an incurable disease. Financial burdens and health consequences of lifelong cART treatment call for novel HIV therapies that result in a permanent cure. Cellular immunity is central in controlling HIV replication. However, HIV adopts numerous strategies to evade immune surveillance. Engineered immunity via genetic manipulation could offer a functional cure by generating cells that have enhanced antiviral activity and are resistant to HIV infection. Recently, encouraging reports from several human clinical trials using an anti-CD19 chimeric antigen receptor (CAR) modified T-cell therapy for treating B-cell malignancies have provided valuable insights and generated remarkable enthusiasm in engineered T-cell therapy. In this review, we discuss the development of HIV-specific chimeric antigen receptors and the use of stem cell based therapies to generate lifelong anti-HIV immunity.

SHIVA - a web application for drug resistance and tropism testing in HIV

BACKGROUND

Drug resistance testing is mandatory in antiretroviral therapy in human immunodeficiency virus (HIV) infected patients for successful treatment. The emergence of resistances against antiretroviral agents remains the major obstacle in inhibition of viral replication and thus to control infection. Due to the high mutation rate the virus is able to adapt rapidly under drug pressure leading to the evolution of resistant variants and finally to therapy failure.

RESULTS

We developed a web service for drug resistance prediction of commonly used drugs in antiretroviral therapy, i.e., protease inhibitors (PIs), reverse transcriptase inhibitors (NRTIs and NNRTIs), and integrase inhibitors (INIs), but also for the novel drug class of maturation inhibitors. Furthermore, co-receptor tropism (CCR5 or CXCR4) can be predicted as well, which is essential for treatment with entry inhibitors, such as Maraviroc. Currently, SHIVA provides 24 prediction models for several drug classes. SHIVA can be used with single RNA/DNA or amino acid sequences, but also with large amounts of next-generation sequencing data and allows prediction of a user specified selection of drugs simultaneously. Prediction results are provided as clinical reports which are sent via email to the user.

CONCLUSIONS

SHIVA represents a novel high performing alternative for hitherto developed drug resistance testing approaches able to process data derived from next-generation sequencing technologies. SHIVA is publicly available via a user-friendly web interface.

Exploiting HIV-1 protease and reverse transcriptase cross-resistance information for improved drug resistance prediction by means of multi-label classification

BACKGROUND

Antiretroviral therapy is essential for human immunodeficiency virus (HIV) infected patients to inhibit viral replication and therewith to slow progression of disease and prolong a patient's life. However, the high mutation rate of HIV can lead to a fast adaptation of the virus under drug pressure and thereby to the evolution of resistant variants. In turn, these variants will lead to the failure of antiretroviral treatment. Moreover, these mutations cannot only lead to resistance against single drugs, but also to cross-resistance, i.e., resistance against drugs that have not yet been applied.

METHODS

662 protease sequences and 715 reverse transcriptase sequences with complete resistance profiles were analyzed using machine learning techniques, namely binary relevance classifiers, classifier chains, and ensembles of classifier chains.

RESULTS

In our study, we applied multi-label classification models incorporating cross-resistance information to predict drug resistance for two of the major drug classes used in antiretroviral therapy for HIV-1, namely protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs). By means of multi-label learning, namely classifier chains (CCs) and ensembles of classifier chains (ECCs), we were able to improve overall prediction accuracy for all drugs compared to hitherto applied binary classification models.

CONCLUSIONS

The development of fast and precise models to predict drug resistance in HIV-1 is highly important to enable a highly effective personalized therapy. Cross-resistance information can be exploited to improve prediction accuracy of computational drug resistance models.

Pharmacogenetics of plasma efavirenz exposure in HIV-infected adults and children in South Africa

AIMS

Genetic factors, notably CYP2B6 516G→T [rs3745274] and 983T→C [rs28399499], explain much of the interindividual variability in efavirenz pharmacokinetics, but data from Africa are limited. We characterized relationships between genetic polymorphisms and plasma efavirenz concentrations in HIV-infected Black South African adults and children.

METHODS

Steady-state mid-dosing interval efavirenz concentrations were measured. We genotyped 241 polymorphisms in genes potentially relevant to efavirenz metabolism and transport, including ABCB1, CYP2A6, CYP2B6, CYP3A4, CYP3A5, NR1I2 and NR1I3.

RESULTS

Among 113 participants (59 adults and 54 children), minor allele frequencies for CYP2B6 516G→T, 983T→C, and 15582C→T [rs4803419] were 0.36, 0.07, and 0.09, respectively. Based on composite CYP2B6 15582/516/983 genotype, there were 33 extensive metabolizer, 62 intermediate metabolizer and 18 slow metabolizer genotypes. Median (IQR) mid-dose efavirenz concentrations were 1.44 (1.21-1.93) µg ml(-1), 2.08 (1.68-2.94) µg ml(-1) and 7.26 (4.82-8.34) µg ml(-1) for extensive, intermediate and slow metabolizers, respectively. In univariate analyses, a model that included composite genotype best predicted efavirenz concentrations (β = 0.28, 95% CI 0.21, 0.35, P = 2.4 × 10(-11)). Among individual CYP2B6 polymorphisms, 516G→T best predicted efavirenz concentrations (β = 0.22, 95% CI 0.13, 0.30, P = 1.27 × 10(-6)). There was also associations with 983T→C (β = 0.27, 95% CI 0.10, 0.44, P = 0.002) and 15582C→T (β = 0.11, 95% CI 0.01, 0.22, P = 0.04). Associations were consistent in adults and children. No other polymorphisms were independently associated with efavirenz concentrations.

CONCLUSIONS

Composite CYP2B6 genotype based on CYP2B6 516G→T, 983T→C, and 15582C→T best described efavirenz exposure in HIV-infected Black South African adults and children.

Scale-up of networked HIV treatment in Nigeria: creation of an integrated electronic medical records system

OBJECTIVES

The implementation of PEPFAR programs in resource-limited settings was accompanied by the need to document patient care on a scale unprecedented in environments where paper-based records were the norm. We describe the development of an electronic medical records system (EMRS) put in place at the beginning of a large HIV/AIDS care and treatment program in Nigeria.

METHODS

Databases were created to record laboratory results, medications prescribed and dispensed, and clinical assessments, using a relational database program. A collection of stand-alone files recorded different elements of patient care, linked together by utilities that aggregated data on national standard indicators and assessed patient care for quality improvement, tracked patients requiring follow-up, generated counts of ART regimens dispensed, and provided 'snapshots' of a patient's response to treatment. A secure server was used to store patient files for backup and transfer.

RESULTS

By February 2012, when the program transitioned to local in-country management by APIN, the EMRS was used in 33 hospitals across the country, with 4,947,433 adult, pediatric and PMTCT records that had been created and continued to be available for use in patient care. Ongoing trainings for data managers, along with an iterative process of implementing changes to the databases and forms based on user feedback, were needed. As the program scaled up and the volume of laboratory tests increased, results were produced in a digital format, wherever possible, that could be automatically transferred to the EMRS. Many larger clinics began to link some or all of the databases to local area networks, making them available to a larger group of staff members, or providing the ability to enter information simultaneously where needed.

CONCLUSIONS

The EMRS improved patient care, enabled efficient reporting to the Government of Nigeria and to U.S. funding agencies, and allowed program managers and staff to conduct quality control audits.

In vitro phenotypes to elvitegravir and dolutegravir in primary macrophages and lymphocytes of clonal recombinant viral variants selected in patients failing raltegravir

OBJECTIVES

The cross-resistance profiles of elvitegravir and dolutegravir on raltegravir-resistant variants is still controversial or not available in macrophages and lack extensive evaluations on wide panels of clonal variants. Thus, a complete evaluation in parallel with all currently available integrase inhibitors (INIs) was performed.

METHODS

The integrase coding region was RT-PCR-amplified from patient-derived plasma samples and cloned into an HIV-1 molecular clone lacking the integrase region. Twenty recombinant viruses bearing mutations to all primary pathways of resistance to raltegravir were phenotypically evaluated with each integrase inhibitor in freshly purified CD4+ T cells or monocyte-derived macrophages.

RESULTS

Y143R single mutants conferred a higher level of raltegravir resistance in macrophages [fold change (FC) 47.7-60.24] compared with CD4+ T cells (FC 9.55-11.56). All other combinations had similar effects on viral susceptibility to raltegravir in both cell types. Elvitegravir displayed a similar behaviour both in lymphocytes and macrophages with all the tested patterns. When compared with raltegravir, none to modest increases in resistance were observed for the Y143R/C pathways. Dolutegravir maintained its activity and cross-resistance profile in macrophages. Only Q148H/R variants had a reduced level of susceptibility (FC 5.48-18.64). No variations were observed for the Y143R/C (+/-T97A) or N155H variants.

CONCLUSIONS

All INIs showed comparable antiretroviral activity in both cell types even if single mutations were associated with a different level of susceptibility in vitro to raltegravir and elvitegravir in macrophages. In particular, dolutegravir was capable of inhibiting with similar potency infection of raltegravir-resistant variants with Y143 or N155 pathways in both HIV-1 major cell reservoirs.