Reversibility of the pathological changes in the follicular dendritic cell network with treatment of HIV-1 infection

In Situ Characterization of Human Lymphoid Tissue Immune Cells by Multispectral Confocal Imaging and Quantitative Image Analysis; Implications for HIV Reservoir Characterization

CD4 T cells are key mediators of adaptive immune responses during infection and vaccination. Within secondary lymphoid organs, helper CD4 T cells, particularly those residing in germinal centers known as follicular helper T cells (Tfh), provide critical help to B-cells to promote their survival, isotype switching and selection of high affinity memory B-cells. On the other hand, the important role of Tfh cells for the maintenance of HIV reservoir is well documented. Thus, interrogating and better understanding the tissue specific micro-environment and immune subsets that contribute to optimal Tfh cell differentiation and function is important for designing successful prevention and cure strategies. Here, we describe the development and optimization of eight multispectral confocal microscopy immunofluorescence panels designed for in depth characterization and immune-profiling of relevant immune cells in formalin-fixed paraffin-embedded human lymphoid tissue samples. We provide a comprehensive library of antibodies to use for the characterization of CD4+ T-cells -including Tfh and regulatory T-cells- as well as CD8 T-cells, B-cells, macrophages and dendritic cells and discuss how the resulting multispectral confocal datasets can be quantitatively dissected using the HistoCytometry pipeline to collect information about relative frequencies and immune cell spatial distributions. Cells harboring actively transcribed virus are analyzed using an in-situ hybridization assay for the characterization of HIV mRNA positive cells in combination with additional protein markers (multispectral RNAscope). The application of this methodology to lymphoid tissues offers a means to interrogate multiple relevant immune cell targets simultaneously at increased resolution in a reproducible manner to guide CD4 T-cell studies in infection and vaccination.

Impact of Integrase Inhibition Compared With Nonnucleoside Inhibition on HIV Reservoirs in Lymphoid Tissues

BACKGROUND

HIV is produced in lymphoid tissues (LT) and stored on the follicular dendritic cell network in LT. When antiretroviral therapy is started, plasma viremia decays in 2 phases; the first within days of starting therapy and the second over weeks. Raltegravir (RAL), an integrase inhibitor, has been associated with only a single rapid phase of decay, and we speculated this may be due to higher intracellular concentration (IC) of RAL in LT. We have previously measured suboptimal ICs of antiretroviral therapy agents in LT, which were associated with slower decay of both vRNA+ cells and the follicular dendritic cell network pool.

SETTING

Outpatient clinic at the Joint Clinical Research Center in Kampala, Uganda.

METHODS

We compared the rate of decay in LT in people starting RAL with those starting efavirenz (EFV).

RESULTS

There was no difference in the rate of virus decay in LT. The ratio of the ICs of RAL and EFV in lymph node to the concentration of drug that inhibits 95% of virus in blood was 1 log lower in lymph node for EFV and >3 logs lower for RAL.

CONCLUSION

These data further highlight the challenges of drug delivery to LT in HIV infection and demonstrate that RAL is not superior to EFV as judged by direct measurements of the source of virus in LT.

Altered immune cell follicular dynamics in HIV infection following influenza vaccination

HIV infection changes the lymph node (LN) tissue architecture, potentially impairing the immunologic response to antigenic challenge. The tissue-resident immune cell dynamics in virologically suppressed HIV+ patients on combination antiretroviral therapy (cART) are not clear. We obtained LN biopsies before and 10 to 14 days after trivalent seasonal influenza immunization from healthy controls (HCs) and HIV+ volunteers on cART to investigate CD4+ T follicular helper (Tfh) and B cell dynamics by flow cytometry and quantitative imaging analysis. Prior to vaccination, compared with those in HCs, HIV+ LNs exhibited an altered follicular architecture, but harbored higher numbers of Tfh cells and increased IgG+ follicular memory B cells. Moreover, Tfh cell numbers were dependent upon preservation of the follicular dendritic cell (FDC) network and were predictive of the magnitude of the vaccine-induced IgG responses. Interestingly, postvaccination LN samples in HIV+ participants had significantly (P = 0.0179) reduced Tfh cell numbers compared with prevaccination samples, without evidence for peripheral Tfh (pTfh) cell reduction. We conclude that influenza vaccination alters the cellularity of draining LNs of HIV+ persons in conjunction with development of antigen-specific humoral responses. The underlying mechanism of Tfh cell decline warrants further investigation, as it could bear implications for the rational design of HIV vaccines.

Visualizing the Immune System: Providing Key Insights into HIV/SIV Infections

Immunological inductive tissues, such as secondary lymphoid organs, are composed of distinct anatomical microenvironments for the generation of immune responses to pathogens and immunogens. These microenvironments are characterized by the compartmentalization of highly specialized immune and stromal cell populations, as well as the presence of a complex network of soluble factors and chemokines that direct the intra-tissue trafficking of naïve and effector cell populations. Imaging platforms have provided critical contextual information regarding the molecular and cellular interactions that orchestrate the spatial microanatomy of relevant cells and the development of immune responses against pathogens. Particularly in HIV/SIV disease, imaging technologies are of great importance in the investigation of the local interplay between the virus and host cells, with respect to understanding viral dynamics and persistence, immune responses (i.e., adaptive and innate inflammatory responses), tissue structure and pathologies, and changes to the surrounding milieu and function of immune cells. Merging imaging platforms with other cutting-edge technologies could lead to novel findings regarding the phenotype, function, and molecular signatures of particular immune cell targets, further promoting the development of new antiviral treatments and vaccination strategies.

The Lymph Node in HIV Pathogenesis

Lymph nodes play a central role in the development of adaptive immunity against pathogens and particularly the generation of antigen-specific B cell responses in specialized areas called germinal centers (GCs). Lymph node (LN) pathology was recognized as an important consequence of human immunodeficiency virus (HIV) infection since the beginning of the HIV epidemic. Investigation into the structural and functional alterations induced by HIV and Simian immunodeficiency virus (SIV) has further cemented the central role that lymphoid tissue plays in HIV/SIV pathogenesis. The coexistence of constant local inflammation, altered tissue architecture, and relative exclusion of virus-specific CD8 T cells from the GCs creates a unique environment for the virus evolution and establishment of viral reservoir in specific GC cells, namely T follicular helper CD4 T cells (Tfh). A better understanding of the biology of immune cells in HIV-infected lymph nodes is a prerequisite to attaining the ultimate goal of complete viral eradication.

Lymphoid Tissue Mesenchymal Stromal Cells in Development and Tissue Remodeling

Secondary lymphoid organs (SLOs) are sites that facilitate cell-cell interactions required for generating adaptive immune responses. Nonhematopoietic mesenchymal stromal cells have been shown to play a critical role in SLO function, organization, and tissue homeostasis. The stromal microenvironment undergoes profound remodeling to support immune responses. However, chronic inflammatory conditions can promote uncontrolled stromal cell activation and aberrant tissue remodeling including fibrosis, thus leading to tissue damage. Despite recent advancements, the origin and role of mesenchymal stromal cells involved in SLO development and remodeling remain unclear.

Successful isolation of infectious and high titer human monocyte-derived HIV-1 from two subjects with discontinued therapy

Background

HIV-1 DNA in blood monocytes is considered a viral source of various HIV-1 infected tissue macrophages, which is also known as “Trojan horse” hypothesis. However, whether these DNA can produce virions has been an open question for years, due to the inability of isolating high titer and infectious HIV-1 directly from monocytes.

Results

In this study, we demonstrated successful isolation of two strains of M-HIV-1 (1690 M and 1175 M) from two out of four study subjects, together with their in vivo controls, HIV-1 isolated from CD4+ T-cells (T-HIV-1), 1690 T and 1175 T. All M- and T- HIV-1 isolates were detected CCR5-tropic. Both M- HIV-1 exhibited higher levels of replication in monocyte-derived macrophages (MDM) than the two T- HIV-1. Consistent with our previous reports on the subject 1175 with late infection, compartmentalized env C2-V3-C3 sequences were identified between 1175 M and 1175 T. In contrast, 1690 M and 1690 T, which were isolated from subject 1690 with relatively earlier infection, showed homogenous env C2-V3-C3 sequences. However, multiple reverse transcriptase (RT) inhibitor resistance-associated variations were detected in the Gag-Pol region of 1690 M, but not of 1690 T. By further measuring HIV DNA intracellular copy numbers post-MDM infection, 1690 M was found to have significantly higher DNA synthesis efficiency than 1690 T in macrophages, indicating a higher RT activity, which was confirmed by AZT inhibitory assays.

Conclusions

These results suggested that the M- and T- HIV-1 are compartmentalized in the two study subjects, respectively. Therefore, we demonstrated that under in vitro conditions, HIV-1 infected human monocytes can productively release live viruses while differentiating into macrophages.

Lymphoid Proliferations Associated With Human Immunodeficiency Virus Infection

Context.—Individuals who are immune deficient are at an increased risk for developing lymphoproliferative lesions and lymphomas. Human immunodeficiency virus (HIV) infection is 1 of 4 clinical settings associated with immunodeficiency recognized by the World Health Organization (WHO) in which there is an increased incidence of lymphoma and other lymphoproliferative disorders.

Objectives.—To describe the major categories of benign lymphoid proliferations, including progressive HIV-related lymphadenopathy, benign lymphoepithelial cystic lesions, and multicentric Castleman disease, as well as the different types of HIV-related lymphomas as defined by the WHO. The characteristic morphologic, immunophenotypic, and genetic features of the different entities will be discussed in addition to some of the pathogenetic mechanisms.

Data Sources.—The WHO classification of tumors of hematopoietic and lymphoid tissues (2001 and 2008), published literature from PubMed (National Library of Medicine), published textbooks, and primary material from the authors' current and previous institutions.

Conclusions.—HIV infection represents one of the clinical settings recognized by the WHO in which immunodeficiency-related lymphoproliferative disorders may arise. Although most lymphomas that arise in patients with HIV infection are diffuse, aggressive B-cell lesions, other lesions, which are “benign” lymphoid proliferations, may also be associated with significant clinical consequences. These lymphoproliferations, like many other immunodeficiency-associated lymphoproliferative disorders, are often difficult to classify. Studies of HIV-associated lymphoid proliferations will continue to increase our understanding of both the immune system and lymphomagenesis.

Antimicrobial peptide LL-37 produced by HSV-2-infected keratinocytes enhances HIV infection of Langerhans cells

Herpes simplex virus (HSV)-2 shedding is associated with increased risk for sexually acquiring HIV. Because Langerhans cells (LCs), the mucosal epithelium resident dendritic cells, are suspected to be one of the initial target cell types infected by HIV following sexual exposure, we examined whether and how HSV-2 affects HIV infection of LCs. Although relatively few HSV-2/HIV-coinfected LCs were detected, HSV-2 dramatically enhanced the HIV susceptibility of LCs within skin explants. HSV-2 stimulated epithelial cell production of antimicrobial peptides (AMPs), including human β defensins and LL-37. LL-37 strongly upregulated the expression of HIV receptors in monocyte-derived LCs (mLCs), thereby enhancing their HIV susceptibility. Culture supernatants of epithelial cells infected with HSV-2 enhanced HIV susceptibility in mLCs, and this effect was abrogated by blocking LL-37 production. These data suggest that HSV-2 enhances sexual transmission of HIV by increasing HIV susceptibility of LCs via epithelial cell production of LL-37.

Critical role of CD4 T cells in maintaining lymphoid tissue structure for immune cell homeostasis and reconstitution

Loss of the fibroblastic reticular cell (FRC) network in lymphoid tissues during HIV-1 infection has been shown to impair the survival of naive T cells and limit immune reconstitution after antiretroviral therapy. What causes this FRC loss is unknown. Because FRC loss correlates with loss of both naive CD4 and CD8 T-cell subsets and decreased lymphotoxin-β, a key factor for maintenance of FRC network, we hypothesized that loss of naive T cells is responsible for loss of the FRC network. To test this hypothesis, we assessed the consequences of antibody-mediated depletion of CD4 and CD8 T cells in rhesus macaques and sooty mangabeys. We found that only CD4 T-cell depletion resulted in FRC loss in both species and that this loss was caused by decreased lymphotoxin-β mainly produced by the CD4 T cells. We further found the same dependence of the FRC network on CD4 T cells in HIV-1-infected patients before and after antiretroviral therapy and in other immunodeficiency conditions, such as CD4 depletion in cancer patients induced by chemotherapy and irradiation. CD4 T cells thus play a central role in the maintenance of lymphoid tissue structure necessary for their own homeostasis and reconstitution.

Follicular dendritic cells activate HIV-1 replication in monocytes/macrophages through a juxtacrine mechanism mediated by P-selectin glycoprotein ligand 1

Follicular dendritic cells (FDCs) are located in the lymphoid follicles of secondary lymphoid tissues and play a pivotal role in the selection of memory B lymphocytes within the germinal center, a major site for HIV-1 infection. Germinal centers are composed of highly activated B cells, macrophages, CD4(+)T cells, and FDCs. However, the physiological role of FDCs in HIV-1 replication remains largely unknown. We demonstrate in our current study that FDCs can efficiently activate HIV-1 replication in latently infected monocytic cells via an intercellular communication network mediated by the P-selectin/P-selectin glycoprotein ligand 1 (PSGL-1) interaction. Upon coculture with FDCs, HIV-1 replication was significantly induced in infected monocytic cell lines, primary monocytes, or macrophages. These cocultures were found to synergistically induce the expression of P-selectin in FDCs via NF-kappaB activation and its cognate receptor PSGL-1 in HIV-1-infected cells. Consistent with this observation, we find that this response is significantly blocked by antagonistic Abs against PSGL-1 and almost completely inhibited by PSGL-1 small interfering RNA. Moreover, a selective inhibitor for Syk, which is a downstream effector of PSGL-1, blocked HIV-1 replication in our cultures. We have thus elucidated a novel regulatory mechanism in which FDCs are a potent positive bystander that facilitates HIV-1 replication in adjacent infected monocytic cells via a juxtacrine signaling mechanism.

Influence of antiretroviral therapy on programmed death-1 (CD279) expression on T cells in lymph nodes of human immunodeficiency virus-infected individuals

Human immunodeficiency virus infection leads to T-cell exhaustion and involution of lymphoid tissue. Recently, the programmed death-1 pathway was found to be crucial for virus-specific T-cell exhaustion during human immunodeficiency virus infection. Programmed death-1 expression was elevated on human immunodeficiency virus-specific peripheral blood CD8+ and CD4+ T cells and correlated with disease severity. During human immunodeficiency infection, lymphoid tissue acts as a major viral reservoir and is an important site for viral replication, but it is also essential for regulatory processes important for immune recovery. We compared programmed death-1 expression in 2 consecutive inguinal lymph nodes of 14 patients, excised before antiretroviral therapy (antiretroviral therapy as of 1997-1999) and 16 to 20 months under antiretroviral therapy. In analogy to lymph nodes of human immunodeficiency virus-negative individuals, in all treated patients, the germinal center area decreased, whereas the number of germinal centers did not significantly change. Programmed death-1 expression was mostly found in germinal centers. The absolute extent of programmed death 1 expression per section was not significantly altered after antiretroviral therapy resulting in a significant-relative increase of programmed death 1 per shrunken germinal center. In colocalization studies, CD45R0+ cells that include helper/inducer T cells strongly expressed programmed death-1 before and during therapy, whereas CD8+ T cells, fewer in numbers, showed a weak expression for programmed death-1. Thus, although antiretroviral therapy seems to reduce the number of programmed death-1-positive CD8+ T lymphocytes within germinal centers, it does not down-regulate programmed death-1 expression on the helper/inducer T-cell subset that may remain exhausted and therefore unable to trigger immune recovery.

Choice of fixative is crucial to successful immunohistochemical detection of phosphoproteins in paraffin-embedded tumor tissues

Protein phosphorylation is frequently used as an indicator of cellular signaling activity. Elevated phosphorylation of tyrosine kinase receptors plays an important role in cancer pathogenesis. However, phosphoproteins are usually poorly preserved in clinical tissue samples that are routinely fixed in 10% formalin. Nonetheless, in oncology clinical trials, use of phosphoproteins as biomarkers has been considered to be of great value in evaluating the effectiveness of a given drug candidate. Therefore, it is worthy of investigating whether alternative fixatives would improve the preservation of phosphoproteins in tissue. We compared the IHC staining of a number of phosphoproteins in xenograft and human surgical tumor tissues fixed in three different fixatives: 10% formalin, 4% paraformaldehyde (PFA), and Streck's tissue fixative (STF). We found that STF significantly enhanced the staining intensity of phosphoproteins compared with 10% formalin or 4% PFA. STF fixative also showed superiority of preservation of phosphoproteins in human surgical samples. Our results indicate that the choice of fixative could significantly affect the usability of clinical tissue samples for evaluating phosphoprotein by IHC.

Effect of antiretroviral therapy on apoptosis markers and morphology in peripheral lymph nodes of HIV-infected individuals

BACKGROUND

CD4+ T cell depletion and destruction and the involution of the lymphoid tissue are hallmarks of HIV infection. Although the underlying mechanisms are still unclear, apoptosis appears to play a central role. The objective of this study was to investigate the effect of antiretroviral therapy on the lymph node tissue, particularly with respect to morphology and apoptosis.

PATIENTS AND METHODS

Between 1997 and 1999, two inguinal lymph nodes were excised from 31 previously untreated individuals who were in an early stage of HIV infection, the first one prior to treatment and the second after 16 to 20 months of treatment. Paraffin sections were investigated for lymph node architecture, distribution of cellular and viral markers, apoptosis, and expression of apoptotic key molecules which indirectly reflect apoptotic processes.

RESULTS

After 16-20 months of antiretroviral therapy, a significant decrease in highly activated HIV-driven immune response was observed in the lymph node tissue as a marked reduction in follicular hyperplasia, a normalization of the follicular dendritic cell network, a significant increase in the number of CD4+ T cells, and a significant decrease in the number of CD8+ T cells. The expression of several proapoptotic (Fas, TRAIL, and active caspase 3) and antiapoptotic (Bcl-2 and IL-7Ralpha) molecules that were reconstituted in the tissues during therapy resembled their expression in lymph nodes of HIV-negative individuals. Limitations of the study are (a) the lack of untreated patients in the late stages, (b) for ethical reasons, the lack of a control group with untreated patients, and (c) for methodological reasons, the restriction of sequential measurements of apotpotic markers to one-third of the patients.

CONCLUSION

Antiretroviral therapy initiated in the early stages in HIV infection may halt the irreversible destruction of the lymph node tissue and may partially normalize apoptotic processes.

Cutting edge: anti-tumor necrosis factor therapy in rheumatoid arthritis inhibits memory B lymphocytes via effects on lymphoid germinal centers and follicular dendritic cell networks

Rheumatoid arthritis (RA) is mediated by a proinflammatory cytokine network with TNF at its apex. Accordingly, drugs that block TNF have demonstrated significant efficacy in the treatment of RA. A great deal of experimental evidence also strongly implicates B cells in the pathogenesis of RA. Yet, it remains unclear whether these two important players and the therapies that target them are mechanistically linked. In this study we demonstrate that RA patients on anti-TNF (etanercept) display a paucity of follicular dendritic cell networks and germinal center (GC) structures accompanied by a reduction in CD38+ GC B cells and peripheral blood memory B cell lymphopenia compared with healthy controls and RA patients on methotrexate. This study provides initial evidence in humans to support the notion that anti-TNF treatment disrupts GC reactions at least in part via effects on follicular dendritic cells.

Complement-HIV interactions during all steps of viral pathogenesis

Upon crossing the endothelial barrier of the host, HIV initiates immediate responses of the immunity system. Among its components, the complement system is one of the first the first elements, which are activated to affect HIV propagation. Complement participates not only in the early phase of the immune response, but its effects can be observed continuously and also concern the induction and modification of the adaptive immune response. Here we discuss the role of complement in early and late stages of HIV pathogenesis and review the escape mechanisms, which protect HIV from destruction by the complement system.

Delayed memory B cell recovery in peripheral blood and lymphoid tissue in systemic lupus erythematosus after B cell depletion therapy

OBJECTIVE

Recent data suggest that the reconstituting peripheral B cell compartment after B cell depletion therapy may be functionally immature, with a preponderance of transitional B cells and a paucity of memory B cells. This study was undertaken to determine the magnitude, duration, and cause of these defects in rituximab-treated systemic lupus erythematosus (SLE) patients.

METHODS

Fifteen patients with SLE previously treated with rituximab as part of a phase I/II dose-escalation study were evaluated during a long-term followup (mean followup period 41 months). B cells from peripheral blood and tonsils were assessed using multicolor flow cytometry, and their developmental pathway was classified based on the expression of defined surface markers.

RESULTS

Reconstitution of peripheral blood CD27+ memory B cells was delayed for several years after B cell depletion therapy in a subset of patients with prolonged clinical responses and autoantibody normalization. This delay correlated with the degree of expansion of B cells of a transitional phenotype during the B cell reconstitution phase (P = 0.005) and the absence of baseline autoantibodies directed against extractable nuclear antigens (RNP, Sm, Ro antigen, La antigen). Despite the paucity of peripheral blood memory cells and the prolonged expansion of functionally immature transitional B cells, tonsil biopsy tissues revealed active germinal center (GC) reactions, but with decreased Fc receptor homolog 4-positive memory B cells.

CONCLUSION

These results suggest heterogeneity in the B cell depletion and reconstitution process that impacts clinical and immunologic outcomes in SLE. The presence of GC reactions, but with altered memory B cell subpopulations in tonsils, suggests that peripheral blood memory cell reconstitution lags behind a slow secondary lymphoid tissue recovery, with important implications for immunologic competence and tolerance.

Cystatin A and HIV-1 p24 antigen expression in tonsillar lymphoid follicles during HIV-1 infection and during highly active antiretroviral therapy

Cystatin A is a natural cysteine proteinase inhibitor and is found in a wide variety of normal cells. The physiologic role of Cystatin A is not fully known, however. Cystatin A is present in large amounts in follicular dendritic cells, which are important in HIV-1 pathogenesis. We analyzed Cystatin A expression in tonsillar sections from 20 patients at various stages of HIV-1 infection. There was a significant (P < 0.001) difference in Cystatin A fractions between patients and controls, with medians (ranges) of 0.61 (0.46-0.83) and 0.86 (0.78-0.90), respectively. Inverse correlations (Spearman rho) existed between Cystatin A and the rate of follicular fragmentation (rho = -0.658) and HIV-1 p24 antigen expression (rho = -0.622) in germinal centers and the amount of HIV-1 RNA in tonsillar tissue (rho = -0.765). The Cystatin A fraction declined from early chronic HIV-1 infection and was significantly lower in patients with a CD4 count below as compared with above 300 cells/muL of blood (P < 0.001), suggesting a favorable initiation of highly active antiretroviral therapy (HAART) at this level. Regeneration of Cystatin A to normal levels was shown in 11 patients 12 and 48 weeks after initiation of HAART, whereas the rate of follicular fragmentation was still elevated. Thus, we found Cystatin A to be a sensitive marker during HIV-1 infection and for regeneration of follicular lymphoid tissue during HAART.

Molecular mechanisms of HIV-1 associated neurodegeneration

Since identification of the human immunodeficiency virus-1 (HIV-1), numerous studies suggest a link between neurological impairments, in particular dementia, with acquired immunodeficiency syndrome (AIDS) with alarming occurrence worldwide. Approximately, 60% of HIV-infected people show some form of neurological impairment, and neuropathological changes are found in 90% of autopsied cases. Approximately 30% of untreated HIV-infected persons may develop dementia. The mechanisms behind these pathological changes are still not understood. Mounting data obtained by in vivo and in vitro experiments suggest that neuronal apoptosis is a major feature of HIV associated dementia (HAD), which can occur in the absence of direct infection of neurons. The major pathway of neuronal apoptosis occurs indirectly through release of neurotoxins by activated cells in the central nervous system (CNS) involving the induction of excitotoxicity and oxidative stress. In addition a direct mechanism induced by viral proteins in the pathogenesis of HAD may also play a role. This review focuses on the molecular mechanisms of HIV-associated dementia and possible therapeutic strategies.

Immune response in cervical dysplasia induced by human papillomavirus: the influence of human immunodeficiency virus-1 co-infection - review

Human immunodeficiency virus (HIV-1) has become an important risk factor for human papillomavirus (HPV) infection and the development of HPV associated lesions in the female genital tract. HIV-1 may also increase the oncogenicity of high risk HPV types and the activation of low risk types. The Center for Disease Control and Prevention declared invasive cervical cancer an acquired immunodeficiency virus (AIDS) defining illness in HIV positive women. Furthermore, cervical cancer happens to be the second most common female cancer worldwide. The host's local immune response plays a critical factor in controlling these conditions, as well as in changes in the number of professional antigen-presenting cells, cytokine, and MHC molecules expression. Also, the production of cytokines may determine which arm of the immune response will be stimulated and may influence the magnitude of immune protection. Although there are many studies describing the inflammatory response in HPV infection, few data are available to demonstrate the influence of the HIV infection and several questions regarding the cervical immune response are still unknown. In this review we present a brief account of the current understanding of HIV/HPV co-infection, emphasizing cervical immune response.

Immunoarchitecture of lymphoid tissue in HIV-infection during antiretroviral therapy correlates with viral persistence

Plasma viral load and T-cell subset determinations in blood are the markers used for monitoring HIV-1 infection. However, key pathogenesis events, viral replication and most immunologic changes occur in the lymphoid tissues. We have studied the tonsillar biopsies of 30 patients in the early stages of the disease, before initiating treatment and after 12 and 36 months of fully effective highly active antiretroviral therapy. We have investigated the HIV RNA by polymerase chain reaction (lymphoid tissue viral load), the immunohistochemical HIV-p24 antigen expression, as well as the lymphoid tissue architecture and lymphoid cell subsets using morphometry. The lymphoid tissue viral load and the immunoexpression of p24, which was found to be mainly associated with follicular dendritic cells, decreased significantly after treatment, but did not disappear in all cases, even after 36 months of treatment. A significant improvement of the lymphoid tissue architecture was also observed after treatment, with recovery of follicular structures. These histological changes correlated with the lymphoid tissue viral load. Moreover, the counts of CD4+ increased whereas CD8+ and cytotoxic lymphocytes (CD8+ granzyme B+) decreased significantly, the latter in both interfollicular and intrafollicular areas. However, these cellular counts after treatment did not reach those of lymphoid tissue of non-HIV-infected patients used as control cases. Naive (CD45RA+) and memory (CD45RO+) cells also improved significantly after treatment. In conclusion, in HIV-infection the impact of treatment can only be assessed completely in the lymphoid tissue reservoir, where most of the virus is stored and associated with follicular dendritic cells. Highly active antiretroviral therapy produces a significant recovery of lymphoid tissue architecture and lymphoid cell subsets, which are associated with the decrease of lymphoid tissue viral load. However, these parameters studied in lymphoid tissue are not re-established completely, even after 36 months of highly active antiretroviral therapy.

HIV-Infected Lymphocytes Regulate Fibronectin Synthesis by TGFβ1 Secretion

Alterations in lymph node architecture occur with HIV infection and contribute to immunological derangements. We previously showed that matrix fibronectin stabilized HIV and increased HIV infection of PBL. We showed increased fibronectin deposition in lymph nodes of HIV-infected patients. However, we did not detect a difference in fibronectin synthesis between uninfected and infected PBL. Therefore, we hypothesized that interactions of HIV-infected cells with fibroblasts resulted in increased fibronectin deposition. We detected increased fibronectin deposition by immunofluorescence on fibroblasts cocultured with HIV-infected PBL. We also found a 6-fold increase in fibronectin mRNA levels in fibroblasts cocultured with HIV-infected PBL by real-time PCR. Furthermore, when HIV-infected PBL were added to reporter fibroblasts stably transfected with a fibronectin promoter, we found a 1.5- to 2-fold increase in promoter activity. Since conditioned medium from HIV-infected PBL also increased fibronectin promoter activity, we hypothesized that a soluble factor such as TGFbeta was responsible for increased fibronectin secretion. Pretreatment of supernatant from HIV-infected PBL with a neutralizing Ab to TGFbeta1 abrogated the increased fibronectin promoter activity. We confirmed that HIV-infected PBL produced increased TGFbeta1 by ELISA. Using Mv1Lu reporter cells, we found a 2- to 3-fold increase in biologically active TGFbeta in supernatants of HIV-infected PBL. Finally, we determined that HIV infection did not change the percentage of active TGFbeta. Our data suggest that HIV-infected lymphocytes indirectly contribute to lymph node remodeling by secretion of TGFbeta1, which increases fibronectin synthesis by fibroblasts.

Mamu-A*01 allele-mediated attenuation of disease progression in simian-human immunodeficiency virus infection

Expression of several major histocompatibility complex (MHC) class I alleles is associated with a protective effect against disease progression in both human immunodeficiency virus type 1 and simian immunodeficiency virus infection. To understand the mechanism underlying this effect, we investigated the expression of the MHC class I allele Mamu-A*01 in simian-human immunodeficiency virus (SHIV) infection, one of the major models for evaluation of AIDS vaccine candidates. We found that disease progression was significantly delayed in Mamu-A*01-positive rhesus monkeys infected with the highly pathogenic SHIV 89.6P. The delay corresponded not only to a noted Mamu-A*01-restricted dominant cytotoxic T-lymphocyte (CTL) response but also to a lower viral load in lymph nodes (LN) and, importantly, to minimal destruction of LN structure during early infection. In contrast, Mamu-A*01-negative monkeys exhibited massive destruction of LN structure with accompanying rapid disease progression. These data indicate that MHC class I allele-restricted CTL responses may play an important role in preservation of lymphoid tissue structure, thereby resulting in attenuation of disease progression in immunodeficiency virus infection.

Mucosal plasma cell repertoire during HIV-1 infection

Impaired development of local Ab responses may predispose HIV-1-infected patients to an increased rate, severity, and duration of mucosal infections. We characterized the repertoire of Ig-producing cells in the intestinal effector compartment (the lamina propria) of HIV-1-infected (n = 29) and seronegative control (n = 27) subjects. The density of Ig-producing cells per area was similar in both groups. However, the proportions of IgA-producing cells were lower in both the duodenum and colon from HIV-1-infected patients compared with those of control subjects (p < 0.05), with compensatory increases in IgG-producing cells in the colon and IgM-producing cells in the duodenum. Similarly, among Abs in the lumen the proportions of IgA were also decreased and the proportions of IgG were increased among HIV-1-infected patients. On a molecular level, V(H) gene repertoire analyses by RT-PCR revealed comparable proportions of the V(H)3 family among duodenal IgA transcripts (50-53%) from both groups. V(H)3 expression was decreased only for IgM among patients with advanced HIV-1 disease (n = 6) compared with that of control subjects (n = 8) (48 +/- 8 vs 62 +/- 13%; p < 0.01). Moreover, the frequencies of individual IgM and IgA V(H)3 genes were comparable in each group, including rates of putative HIV-1 gp120-binding V(H)3 genes (V3-23, V3-30, V3-30/3-30.5). We conclude that, despite a decrement in local IgA producing cells, the density and molecular V(H) repertoire of mucosal plasma cells are relatively intact among patients with HIV-1 infection. These data suggest that HIV-1-infected patients use functional regulatory mechanisms to provide sufficient V(H) diversity and effective induction and differentiation of mucosal B cells.

Manipulation of lymphoid microenvironments in nonhuman primates by an inhibitor of the lymphotoxin pathway

Reticular networks in lymphoid organs play critical roles in the organization of local microenvironments. A number of these elements are maintained by continual signaling through the lymphotoxin system. Evaluation of the lymphotoxin (LT) pathway in primates using a fusion protein decoy provides a unique opportunity to assess modulation of splenic microenvironments in a species with considerably greater background immunological activity compared with rodents. Within the germinal center microenvironment, treatment resulted in a collapse of follicular dendritic cell (FDC) networks and in the disappearance of a ringlike network of immune complex-carrying cells, although some other attributes of the germinal center appeared to be unaltered. Treatment also resulted in changes in the splenic marginal zone, a microenvironment where the architecture is notably different from that of the rodent. Cessation of treatment and recovery allowed us to monitor reemergence of these cell types and revealed that FDCs rely on LT-dependent signals to recompact into appropriately positioned tight networks. Despite the loss of FDC networks, the primary Ab response to keyhole limpet hemocyanin was unaltered over a 20-day period. Manipulation of these microenvironments may represent a novel approach to modulating immune function in human disease.

Collagen deposition in HIV-1 infected lymphatic tissues and T cell homeostasis

Lymphatic tissues (LTs) are structurally organized to promote interaction between antigens, chemokines, growth factors, and lymphocytes to generate an immunologic response and maintain normal-sized populations of CD4(+) and CD8(+) T cells. Inflammation and tissue remodeling that accompany local innate and adaptive immune responses to HIV-1 replication cause damage to the LT architecture. As a result, normal populations of CD4(+) and CD8(+) T cells cannot be supported and antigen-lymphocyte interactions are impaired. This conclusion is supported herein following LT sampling before and during anti-HIV therapy in persons with acute, chronic, and late-stage HIV-1 infection. Among seven individuals treated with anti-retroviral therapy (ART) and four individuals deferring therapy we found evidence of significant paracortical T cell zone damage associated with deposition of collagen, the extent of which was inversely correlated with both the size of the LT CD4(+) T cell population and the change in peripheral CD4(+) T cell count with anti-HIV therapy. The HIV-1-associated inflammatory changes and scarring in LT both limit the ability of the tissue to support and reestablish normal-sized populations of CD4(+) T cells and suggest a novel mechanism of T cell depletion that may explain the failure of ART to significantly increase CD4(+) T cell populations in some HIV-1-infected persons.

Dynamics of T cells and TCR excision circles differ after treatment of acute and chronic HIV infection

We quantified T cell proliferation and thymic function in primary HIV infection (PHI; n = 19) and chronic HIV infection (CHI; n = 14) by measuring Ki67 staining and TCR excision circle (TREC) number. After antiretroviral therapy of PHI there is a profound decrease in the number and percentage of Ki67(+) T cells (<6% Ki67(+)) with no significant increase in TREC per million cells and a transient increase in TREC per milliliter. In contrast, after antiretroviral therapy of CHI there is a reduction in the percentage but little change in the total number of Ki67(+)CD4(+) T cells associated with increases in both TREC per million cells and TREC per milliliter. Using a mathematical model that accounts for proliferation, death, and redistribution of T cells, we find that redistribution is consistent with the TREC changes observed during treatment of PHI and that an increase in thymic output is needed to explain the increase in TREC during treatment of CHI. Consideration of TREC per milliliter shows that changes in proliferation alone cannot explain the changes in TREC. In addition, although increased proliferation of memory cells in HIV infection has been established, we find no difference in TREC per million CD45RA(-) "memory" T cells between healthy and infected individuals (p = 0.154 for CD4(+); p = 0.383 for CD8(+)). Finally, although the number of TREC per million cells is always much lower in memory T cells than in naive T cells, in the setting of HIV infection, given that memory cells make up a larger proportion of total T cells, we find that 50% of TREC per milliliter in CD4(+) T cells is harbored in the CD45RA(-) "memory" subset of our infected subjects.

Disrupted homeostasis of Langerhans cells and interdigitating dendritic cells in monkeys with AIDS

Langerhans cells (LCs) are immature dendritic cells (DCs) that capture antigen in peripheral tissues and migrate to draining lymph nodes, where they reside in the paracortex as interdigitating dendritic cells (IDCs). We studied the effects of simian immunodeficiency virus (SIV) on LCs and IDCs during different stages of infection in monkeys. LCs isolated from monkeys with acute SIV infection or acquired immunodeficiency syndrome (AIDS) underwent normal maturation in vitro, including a switch in chemokine receptor expression from CCR5 to CXCR4 and CCR7. LCs migrated normally from skin in response to contact sensitization in monkeys with acute SIV infection. In contrast, LC migration from skin was markedly impaired during AIDS, associated with a reduction in antigen-bearing DCs in draining lymph nodes. Lymph node IDCs were increased in proportion during acute SIV infection and had an activated phenotype, whereas during AIDS IDCs had significantly lower expression of CD40 and the activation marker CD83. IDCs from monkeys with AIDS were refractory to stimulation with CD40L, demonstrating a functional consequence of decreased CD40 expression. SIV-infected DCs were not identified in lymph nodes or skin of monkeys with AIDS, suggesting an indirect effect of infection on DC populations in vivo. These data indicate that DCs are mobilized to lymph nodes during acute SIV infection, but that during AIDS this process is suppressed, with LC migration and IDC activation being impaired. We conclude that disruption of DC homeostasis may play a role in immunopathology induced by human immunodeficiency virus and suggest that therapeutic strategies targeting DCs may have limited efficacy during AIDS.

Retention of antigen on follicular dendritic cells and B lymphocytes through complement-mediated multivalent ligand-receptor interactions: theory and application to HIV treatment

In HIV-infected patients, large quantities of HIV are associated with follicular dendritic cells (FDCs) in lymphoid tissue. During antiretroviral therapy, most of this virus disappears after six months of treatment, suggesting that FDC-associated virus has little influence on the eventual outcome of long-term therapy. However, a recent theoretical study using a stochastic model for the interaction of HIV with FDCs indicated that some virus may be retained on FDCs for years, where it can potentially reignite infection if treatment is interrupted. In that study, an approximate expression was used to estimate the time an individual virion remains on FDCs during therapy. Here, we determine the conditions under which this approximation is valid, and we develop expressions for the time a virion spends in any bound state and for the effect of rebinding on retention. We find that rebinding, which is influenced by diffusion, may play a major role in retention of HIV on FDCs. We also consider the possibility that HIV is retained on B cells during therapy, which like FDCs also interact with HIV. We find that virus associated with B cells is unlikely to persist during therapy.

High frequency of virus-specific B lymphocytes in germinal centers of simian-human immunodeficiency virus-infected rhesus monkeys

The etiology of the lymphadenopathy and follicular hyperplasia associated with human immunodeficiency virus type 1 (HIV-1) infection has remained unclear. To determine whether the B-lymphocyte expansions characteristic of this syndrome represent polyclonal and virus-specific processes, the antigen specificity of B cells in lymphoid tissues of monkeys infected with simian-human immunodeficiency virus (SHIV) chimeras was assessed using an inverse immunohistochemical assay with biotinylated HIV-1 envelope gp120 (Env) as an antigen probe. Env-binding B cells were found aggregated in lymph node and splenic germinal centers (GCs). Most Env-binding GCs also contained an unstained population of B cells, suggesting the GCs were formed by a polyclonal (oligoclonal) process. By day 42 following infection, Env-binding B cells were present in 19% of all lymph node GCs. Env-binding cells were present in 25% of GCs even during chronic infection. This extraordinarily high frequency of Env-specific B lymphocytes suggests that the expansion of virus-specific B cells may largely account for the follicular hyperplasia in AIDS virus-infected individuals.

Structural normalization of the lymphoid tissue in asymptomatic HIV-infected patients after 48 weeks of potent antiretroviral therapy

BACKGROUND

The hallmark of HIV infection is the involution and destruction of lymphoid tissue. However, very little information exists on the effect of highly active antiretroviral therapy (HAART) on lymphoid tissue structure.

OBJECTIVE

To evaluate the effect of a HAART regimen after 48 weeks on the architecture and cell regeneration of tonsil lymphoid tissue in HIV-infected patients with CD4 T cell counts > or = 500/microl.

METHODS

From June 1997 to February 1998 all asymptomatic HIV-infected patients with CD4 T cell counts > or = 500/microl seen at our unit were offered quadruple antiretroviral therapy. Tonsil biopsies were obtained at baseline and at 48 weeks. Tonsil tissue sections were examined to evaluate structural and immunohistochemical changes by two blinded and independent pathologists. Cell numbers were counted for selected markers in T-dependent zones.

RESULTS

Eleven patients were evaluable, six were excluded because of insufficient or inadequate sampling in at least one of the biopsies. Cellular depletion, plasma cell accumulation and prominent vessels were observed in all cases; three excluded patients with evaluable baseline biopsies showed similar tissue lesions. Follow-up biopsies demonstrated some degree of improvement in all patients. Germinal centres appeared in seven cases that were not seen at baseline. CD4 cell counts increased and CD8 cell counts decreased significantly in lymphoid tissue. An increase in CD45RA+ cells was observed; however, the proportion of CD45+Ki67+ cells did not differ between baseline and 48 weeks.

CONCLUSION

This study shows an unexpected range of moderate to severe lymphoid tissue lesions in mildly immunosuppressed HIV-infected patients, which was partly restored after 48 weeks of HAART.

Human immunodeficiency virus pathogenesis: insights from studies of lymphoid cells and tissues

Although plasma virus load is invaluable for monitoring human immunodeficiency virus (HIV) infection, key pathogenesis events and most viral replication take place in lymphoid tissues. Decreases in virus load associated with therapy occur in plasma and tissues, but persistent latent infection and ongoing viral replication are evident. Many unanswered questions remain regarding mechanisms of HIV-associated lymphocyte depletion, but partial CD4(+) cell reconstitution after therapy likely reflects retrafficking from inflamed tissues, increased thymic or peripheral production, and decreased destruction. Rapid establishment of latent infection and the follicular dendritic cell-associated viral pool within lymphoid tissues suggest that only early intervention could substantially alter the natural history of HIV. If therapy is started prior to seroconversion, some individuals retain potent HIV-specific cellular immune responsiveness that is suggestive of delayed progression. Although complete virus eradication appears out of reach at present, more attention is being directed toward the prospect of boosting HIV-specific immune responses to effect another type of "clinical cure": immune-mediated virus suppression in the absence of therapy.

HIV-specific effector cytotoxic T lymphocytes and HIV-producing cells colocalize in white pulps and germinal centers from infected patients

Human immunodeficiency virus (HIV) infection is characterized by the massive infiltration of secondary lymphoid organs with activated CD8(+) T lymphocytes. While converging data indicated that these cells were HIV-specific cytotoxic T lymphocytes (CTLs) responsible for HIV spread limitation, direct evidence was lacking. Here, the presence of HIV-specific effector CTLs was demonstrated directly ex vivo in 15 of 24 microdissected splenic white pulps from an untreated patient and in 1 of 24 tonsil germinal centers from a second patient with incomplete viral suppression following bitherapy. These patients had plasma HIV RNA loads of 5900 and 820 copies per milliliter. The frequencies of HIV-1 DNA(+) cells in their lymphoid organs were more than 1 in 50 and 1 in 175, respectively. Spliced viral messenger RNA (a marker for ongoing viral replication) was present in most immunocompetent structures tested. Conversely, CTL activity was not found in spleens from 2 patients under highly active antiretroviral therapy, with undetectable plasma viral load. These patients had much lower spleen DNA(+) cell frequencies (1 in 2700 and 1 in 3800) and no white pulps containing spliced RNA. CTL effector activity as well as spliced viral messenger RNA were both concentrated in the white pulps and germinal centers. This colocalization indicates that viral replication in immunocompetent structures of secondary lymphoid organs triggers anti-HIV effector CTLs to these particular locations, providing clues to target therapeutic intervention.

Release of virus from lymphoid tissue affects human immunodeficiency virus type 1 and hepatitis C virus kinetics in the blood

Kinetic parameters of human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) infections have been estimated from plasma virus levels following perturbation of the chronically infected (quasi-) steady state. We extend previous models by also considering the large pool of virus localized in the lymphoid tissue (LT) compartment. The results indicate that the fastest time scale of HIV-1 plasma load decay during therapy probably reflects the clearance rate of LT virus and not, as previously supposed, the clearance rate of virus in plasma. This resolves the discrepancy between the clearance rate estimates during therapy and those based on plasma apheresis experiments. In the extended models plasma apheresis measurements are indeed expected to reflect the plasma decay rate. We can reconcile all current HIV-1 estimates with this model when, on average, the clearance rate of virus in plasma is approximately 20 day(-1), that of LT virus is approximately 3 day(-1), and the death rate of virus-producing cells is approximately 0.5 day(-1). The fast clearance in the LT compartment increases current estimates for total daily virus production. Because HCV is produced in the liver, we let virus be produced into the blood compartment of our model. The results suggest that extending current HCV models with an LT compartment is not likely to affect current estimates for kinetic parameters and virus production. Estimates for treatment efficacy might be affected, however.

In vitro evolution of the human immunodeficiency virus type 1 gag-protease region and maintenance of reverse transcriptase resistance following prolonged drug exposure

We studied the human immunodeficiency virus type 1 phenotypic and genotypic profiles of a dual drug-resistant isolate (isolate 14aPost-DR) selected for zidovudine (ZDV) and lamivudine (3TC) resistance and then cultured in the presence of 3TC and a protease inhibitor: indinavir (IDV), ritonavir, or KNI-272. The IDV-treated virus was highly resistant to 3TC, ZDV, and IDV and accumulated protease mutations at positions M46I and V82F. A change from alanine to valine was observed in 4 of 10 clones in the P2 position of the p7-p1 Gag-protease cleavage site, linked to position M46I in the dominant viral quasispecies. Previous 3TC resistance did not impair the development of additional mutations in the protease and Gag-protease cleavage regions.

Lymph nodes during antiretroviral therapy

Highly active antiretroviral therapy rapidly reduces virus replication in the lymphoid tissue. Production of viral RNA, however, may still be detected in the lymphoid tissue despite negative plasma viremia. Continuing virus production and latent infection in resting cells seem to be important factors for viral rebound following treatment interruption. In parallel with viral suppression, immune activation is decreased and CD4+ T cell counts in the lymphoid tissue increase. It is still not known if there is a potential for complete viral suppression and immune reconstitution. Analyses of the lymphoid tissue during therapy may be helpful in addressing these issues.

A genotypic analysis of patients receiving Zidovudine with either Lamivudine, Didanosine or Zalcitabine dual therapy using the LiPA point mutation assay to detect genotypic variation at codons 41, 69, 70, 74, 184 and 215

BACKGROUND

The Murex-Innogenetics LiPA HIV-1 RT assay can be used to identify the presence of mutations of the reverse transcriptase gene at codons 41, 69, 70, 74, 184 and 215 of HIV-1, which have been shown to confer resistance to the nucleoside analogs Zidovudine (ZDV), Lamivudine (3TC), Didanosine (ddI) and Zalcitabine (ddC). The M184V mutation of the reverse transcriptase gene of HIV-1 has been associated with resistance to 3TC, ddC and ddI. This mutation has also been observed in patients receiving ZDV+ddC and ZDV+ddI. We used LiPA HIV-1 RT assay to identify the presence of either consensus methionine 184 or the mutant valine 184 with three groups of patients who were treated with ZDV/3TC, ZDV/ddI or ZDV/ddC combination therapy.

OBJECTIVES

The aim of our study was to determine the viral genotype of patients who were considered to be failing therapy, by two ways: using sequencing and LiPA assays. In particular we were interested in establishing a possible correlation between these methods.

STUDY DESIGN

The study group consisted of a consecutive series of 33 patients with a treatment failure, 18 of whom received ZDV+3TC therapy, seven received ZDV+ddI and eight received ZDV+ddC therapy. We also examined a small cohort of seven seroconverters.

RESULTS

The M184V mutation was observed in 47.0% of patients receiving ZDV+3TC combination therapy but was not observed in either patient group receiving either ddI or ddC as co-therapy with ZDV. There was no evidence of the L74V mutation in our study group in either the ZDV/ddI or ZDV/ddC combination therapy group. We found the frequency of the K70R mutation to be higher in patients treated with ZDV/ddI (P=0.033) or ZDV/ddC (P=0.3) when compared with patients treated with ZDV/3TC.

CONCLUSION

The LiPA assay allowed for the rapid detection of wild type and amino acid variations at key positions conferring resistance to the most used antiviral RT inhibitors. This represented a rapid, quite sensitive, and simple genotyping test. For these reasons the LiPA assay proved to be useful in studying genetic resistance in large screenings, when key RT mutations could be useful in guiding an effective HIV-1 suppressing regimen.

Influence of follicular dendritic cells on decay of HIV during antiretroviral therapy

Drug treatment of HIV type 1 (HIV-1) infection leads to a rapid initial decay of plasma virus followed by a slower second phase of decay. To investigate the role of HIV-1 retained on follicular dendritic cells (FDCs) in this process, we have developed and analyzed a mathematical model for HIV-1 dynamics in lymphoid tissue (LT) that includes FDCs. Analysis of clinical data using this model indicates that decay of HIV-1 during therapy may be influenced by release of FDC-associated virus. The biphasic character of viral decay can be explained by reversible multivalent binding of HIV-1 to receptors on FDCs, indicating that the second phase of decay is not necessarily caused by long-lived or latently infected cells. Furthermore, viral clearance and death of short-lived productively infected cells may be faster than previously estimated. The model, with reasonable parameter values, is consistent with kinetic measurements of viral RNA in plasma, viral RNA on FDCs, productively infected cells in LT, and CD4(+) T cells in LT during therapy.

Highly active antiretroviral therapy results in HIV type 1 suppression in lymph nodes, increased pools of naive T cells, decreased pools of activated T cells, and diminished frequencies of peripheral activated HIV type 1-specific CD8+ T cells

This study examines sequential lymph nodes from 13 drug-naive patients before and after 24 weeks of highly active antiretroviral therapy (HAART). A multipronged approach was used to study changes in HIV-1 RNA in each paired lymph node in relation to tissue architecture and frequency of naive T cells. After 24 weeks, all patients showed significant suppression of plasma viral load and 12 of 13 showed concordant viral suppression in the lymph node (p = 0.001). Using in situ hybridization and quantitative image analysis, we showed that HIV-1 RNA was reduced to below detectable levels (two copies per cell) in follicular dendritic cell (FDC) and mononuclear cell pools. Independent immunohistochemical analysis of lymph node sections revealed that 5 of 13 patients displayed increased FDC networks and 6 of 13 showed no change and all patients showed increases in tissue-resident CD4+ cells. All lymph node biopsies at 24 weeks showed increased proportions of CD4+ and CD8+ cells coexpressing the naive markers CD45RA and CD62L when compared with baseline values. Significant correlations existed between viral load suppression and loss of activated CD8+ T cells after 24 weeks in both lymph node and blood, which was mirrored by significantly lowered frequencies of activated peripheral Gag peptide/MHC tetramer+ CD8+ cells. Overall, these data show that a potent and successful treatment strategy that significantly suppresses and removes FDC-resident HIV-1 results in improvements in lymphoid architecture and by so doing provides the structures available for increased numbers of naive cells to interact with cognate antigen. In addition, our article shows that suppression of HIV-1 replication results in diminished frequencies of peripherally activated antigen-specific CD8+ cells.

Influence of follicular dendritic cells on HIV dynamics

In patients infected with human immunodeficiency virus type 1 (HIV-1), a large amount of virus is associated with follicular dendritic cells (FDCs) in lymphoid tissue. To assess the influence of FDCs on viral dynamics during antiretroviral therapy we have developed a mathematical model for treatment of HIV-1 infection that includes FDCs. Here, we use this model to analyse measurements of HIV-1 dynamics in the blood and lymphoid tissue of a representative patient, who was treated with a combination of HIV-1 reverse transcriptase and protease inhibitors. We show that loss of virus from FDCs during therapy can make a much larger contribution to plasma virus than production of virus by infected cells. This result challenges the notion that long-lived infected cells are a significant source of HIV-1 during drug therapy. Due to release of FDC-associated virus, we find that it is necessary to revise upward previous estimates of c, the rate at which free virus is cleared, and delta, the rate at which productively infected cells die. Furthermore, we find that potentially infectious virus, present before treatment, is released from FDCs during therapy and that the persistence of this virus can be affected by whether therapy includes reverse transcriptase inhibitors.

Rapid activation of lymph nodes and mononuclear cell HIV expression upon interrupting highly active antiretroviral therapy in patients after prolonged viral suppression

OBJECTIVE

To compare the architecture and HIV-1 RNA and Gag p24 protein expression in lymph nodes (LN) excised from individuals during chronic highly active antiretroviral therapy (HAART) with LN removed from the same patient after plasma virus rebound following the interruption of HAART.

MATERIALS AND METHODS

Six HIV-1-infected patients on HAART, with CD4 cell counts greater than 350 cells/microl, and plasma HIV-1 RNA less than 50 copies/ml, underwent inguinal LN excision upon discontinuation of HAART, and again after rebound of plasma virus. Lymph nodes were evaluated by immunohistochemical staining for Gag p24 antigen and Ki67, in-situ hybridization for HIV-1 RNA and H3-histone, and transmission electron microscopy (TEM).

RESULTS

LN at baseline were quiescent to mildly hyperplastic and generally contained more primary than secondary follicles. Only one LN had detectable follicular dendritic cell (FDC)-associated p24 antigen, none had HIV RNA. Few mononuclear cells (MNC) expressed RNA or p24 antigen. Plasma virus at the second biopsy ranged from 329 to 3.2 x 10(6) copies/ml. CD4 cell count decline ranged from 5 to 51% during drug hiatus, and was greatest in patients with highest viral rebound. Four of six of the second LN were more hyperplastic than the initial LN, two showed paracortical hyperplasia. MNC expression of HIV RNA in the second LN paralleled the level of plasma viremia. Increased Ki67 and H3-histone signal occurred in the second LN.

CONCLUSION

Quiescent LN from individuals on HAART rapidly become hyperplastic and activated within 1-2 months after treatment interruption. As in acute HIV infection, virus expression by LN MNC parallels the rebound in plasma viremia and fall in CD4 cell count.

Treatment-induced decline of human immunodeficiency virus-1 p24 and HIV-1 RNA in lymphoid tissue of patients with early human immunodeficiency virus-1 infection

We report detailed quantitative analysis of human immunodeficiency virus-1 (HIV-1) p24 and HIV-1 RNA in tonsil biopsies from 13 patients with early, asymptomatic HIV infection before and during combination antiretroviral therapy. Using fluorescent microscopy in conjunction with reverse transcriptase-polymerase chain reaction of frozen tissue sections, we show that plasma and tissue viral loads decreased by approximately 3 logs during the 1-year treatment period, with good correlation between the HIV-1 p24 and HIV-1 RNA response in tissue. The decrease of tissue viral load was delayed compared to plasma viral load, possibly explained by the observation that the amount of follicular dendritic cell-associated virus correlated best with the area under the curve of plasma HIV-1 RNA throughout the last 12 weeks. Before and during treatment, the relative proportions of HIV-1 on follicular dendritic cells and within mononuclear cells remained constant, suggesting similar decay characteristics in these two lymphoid tissue compartments. However, viral p24 or RNA remained almost always detectable in tissue despite full suppression of HIV-1 RNA in plasma, and increased even after short-term rebounds in plasma viral load. Thus, full and sustained suppression of viral replication was required to efficiently decrease viral load in lymphoid tissue, but complete abolition of residual viral replication was not achieved.

The case for more cautious, patient-focused antiretroviral therapy

Many clinicians who care for patients with HIV infection are dissatisfied with the existing recommendations on antiretroviral therapy. Current practice focuses on the early suppression of viremia, yet the outcome of that approach may not be in the best interest of individual patients or populations. The major goal of HIV therapy is to maintain the long-term health of the patient while avoiding drug-related toxicity and preserving viable future treatment options. Recent studies have challenged the principles on which recommendations for early, aggressive treatment were based. Key studies that lead to licensure of antiretroviral medications usually involve short-term results in treatment-naive patients; it is difficult to apply these results to long-term management of therapy-experienced patients. Early, aggressive therapy often prematurely exposes patients to risks for medication-related side effects and resistance. A more cautious, patient-focused, long-term approach to therapy would help foster studies of alternate strategies, such as delayed initiation of therapy, protease-sparing therapy, class-sparing therapy, planned drug interruptions, switches in therapy, and immune-based therapy. It is time for clinicians to rethink their approach to the treatment of HIV infection.