Macrophage-Derived Factors with the Potential to Contribute to Pathogenicity of HIV-1 and HIV-2: Role of CCL-2/MCP-1.

Human immunodeficiency virus type 2 (HIV-2) is known to be less pathogenic than HIV-1. However, the mechanism(s) underlying the decreased HIV-2 pathogenicity is not fully understood. Herein, we report that ß-chemokine CCL2 expression was increased in HIV-1-infected human monocyte-derived macrophages (MDM) but decreased in HIV-2-infected MDM when compared to uninfected MDM. Inhibition of CCL2 expression following HIV-2 infection occurred at both protein and mRNA levels. By microarray analysis, quantitative PCR, and Western blotting, we identified that Signal Transducer and Activator of Transcription 1 (STAT1), a critical transcription factor for inducing CCL2 gene expression, was also reduced in HIV-2-infected MDM. Blockade of STAT1 in HIV-infected MDM using a STAT1 inhibitor significantly reduced the production of CCL2. In contrast, transduction of STAT1-expressing pseudo-retrovirus restored CCL2 production in HIV-2-infected MDM. These findings support the concept that CCL2 inhibition in HIV-2-infected MDM is meditated by reduction of STAT1. Furthermore, we showed that STAT1 reduction in HIV-2-infected MDM was regulated by the CUL2/RBX1 ubiquitin E3 ligase complex-dependent proteasome pathway. Knockdown of CUL2 or RBX1 restored the expression of STAT1 and CCL2 in HIV-2-infected MDM. Taken together, our findings suggest that differential regulation of the STAT1-CCL2 axis may be one of the mechanisms underlying the different pathogenicity observed for HIV-1 and HIV-2.

The Myeloid-Specific Transcription Factor PU.1 Upregulates Mannose Receptor Expression but Represses Basal Activity of the HIV-LTR Promoter.

Human mannose receptor 1 (MRC1) is a cell surface receptor expressed in macrophages and other myeloid cells that inhibits human immunodeficiency virus type 1 (HIV-1) particle release by tethering virions to producer cell membranes. HIV-1 counteracts MRC1 expression by inhibiting mrc1 transcription. Here, we investigated the mechanism of MRC1 downregulation in HIV-1-infected macrophages. We identified the myeloid cell-specific transcription factor PU.1 as critical for regulating MRC1 expression. In the course of our study, we recognized a complex interplay between HIV-1 Tat and PU.1 transcription factors: Tat upregulated HIV-1 gene expression but inhibited mrc1 transcription, whereas PU.1 inhibited HIV-1 transcription but activated MRC1 expression. Disturbing this equilibrium by silencing PU.1 resulted in increased HIV-1 gene expression and reduced MRC1 promoter activity. Our study identified PU.1 as a central player in transcriptional control, regulating a complex interplay between viral and host gene expression in HIV-infected macrophages. IMPORTANCE HIV-1 replication in primary human cells depends on the activity of virus-encoded proteins but also involves cellular factors that can either promote (viral dependency factors) or inhibit (host restriction factors) virus replication. In previous work, we identified human MRC1 as a macrophage-specific host restriction factor that inhibits the detachment of viral particles from infected cells. Here, we report that HIV-1 counteracts this effect of MRC1 by imposing a transcriptional block on cellular MRC1 gene expression. The transcriptional inhibition of the MRC1 gene is accomplished by Tat, an HIV-1 factor whose best-described function actually is the enhancement of HIV-1 gene expression. Thus, HIV-1 has evolved to use the same protein for (i) activation of its own gene expression while (ii) inhibiting expression of MRC1 and other host factors.

FDA Approval Summary: Margetuximab plus Chemotherapy for Advanced or Metastatic HER2-Positive Breast Cancer.

On December 16, 2020, the FDA granted regular approval to margetuximab-cmkb (MARGENZA), in combination with chemotherapy, for the treatment of adult patients with HER2-positive (HER2+) metastatic breast cancer who have received two or more prior anti-HER2 regimens, at least one of which was for metastatic disease. Approval was based on data from SOPHIA, a multicenter, randomized, open-label, active controlled study comparing margetuximab with trastuzumab, in combination with chemotherapy. The primary efficacy endpoint was progression-free survival (PFS) by blinded independent central review. SOPHIA demonstrated a 0.9-month difference in median PFS between the two treatment arms [5.8 vs. 4.9 months, respectively; stratified HR, 0.76 (95% confidence interval: 0.59-0.98; P = 0.0334)]. Overall survival (OS) was immature at the data cut-off date of September 10, 2019. Infusion-related reactions (IRR) are an important safety signal associated with margetuximab plus chemotherapy. In SOPHIA, 13% of patients treated with margetuximab plus chemotherapy reported IRRs, of which 1.5% were grade 3. The most commonly reported adverse drug reactions (>10%) with margetuximab in combination with chemotherapy were fatigue/asthenia, nausea, diarrhea, vomiting, constipation, headache, pyrexia, alopecia, abdominal pain, peripheral neuropathy, arthralgia/myalgia, cough, decreased appetite, dyspnea, IRR, palmar-plantar erythrodysesthesia, and extremity pain. Overall, the favorable risk-benefit profile for margetuximab when added to chemotherapy supported its approval for the intended indication.

Variable Induction of Pro-Inflammatory Cytokines by Commercial SARS CoV-2 Spike Protein Reagents: Potential Impacts of LPS on In Vitro Modeling and Pathogenic Mechanisms In Vivo.

Proinflammatory cytokine production following infection with severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) is associated with poor clinical outcomes. Like SARS CoV-1, SARS CoV-2 enters host cells via its spike protein, which attaches to angiotensin-converting enzyme 2 (ACE2). As SARS CoV-1 spike protein is reported to induce cytokine production, we hypothesized that this pathway could be a shared mechanism underlying pathogenic immune responses. We herein compared the capabilities of Middle East Respiratory Syndrome (MERS), SARS CoV-1 and SARS CoV-2 spike proteins to induce cytokine expression in human peripheral blood mononuclear cells (PBMC). We observed that only specific commercial lots of SARS CoV-2 induce cytokine production. Surprisingly, recombinant SARS CoV-2 spike proteins from different vendors and batches exhibited different patterns of cytokine induction, and these activities were not inhibited by blockade of spike protein-ACE2 binding using either soluble ACE2 or neutralizing anti-S1 antibody. Moreover, commercial spike protein reagents contained varying levels of lipopolysaccharide (LPS), which correlated directly with their abilities to induce cytokine production. The LPS inhibitor, polymyxin B, blocked this cytokine induction activity. In addition, SARS CoV-2 spike protein avidly bound soluble LPS in vitro, rendering it a cytokine inducer. These results not only suggest caution in monitoring the purity of SARS CoV-2 spike protein reagents, but they indicate the possibility that interactions of SARS CoV-2 spike protein with LPS from commensal bacteria in virally infected mucosal tissues could promote pathogenic inflammatory cytokine production.

Analyzing the Role of Gut Microbiota on the Onset of Autoimmune Diseases Using TNFΔARE Murine Model.

Very little is known about disease transmission via the gut microbiome. We hypothesized that certain inflammatory features could be transmitted via the gut microbiome and tested this hypothesis using an animal model of inflammatory diseases. Twelve-week-old healthy C57 Bl/6 and Germ-Free (GF) female and male mice were fecal matter transplanted (FMT) under anaerobic conditions with TNFΔARE-/+ donors exhibiting spontaneous Rheumatoid Arthritis (RA) and Inflammatory Bowel Disease (IBD) or with conventional healthy mice control donors. The gut microbiome analysis was performed using 16S rRNA sequencing amplification and bioinformatics analysis with the HIVE bioinformatics platform. Histology, immunohistochemistry, ELISA Multiplex analysis, and flow cytometry were conducted to confirm the inflammatory transmission status. We observed RA and IBD features transmitted in the GF mice cohort, with gut tissue disruption, cartilage alteration, elevated inflammatory mediators in the tissues, activation of CD4/CD8+ T cells, and colonization and transmission of the gut microbiome similar to the donors' profile. We did not observe a change or transmission when conventional healthy mice were FMT with TNFΔARE-/+ donors, suggesting that a healthy microbiome might withstand an unhealthy transplant. These findings show the potential involvement of the gut microbiome in inflammatory diseases. We identified a cluster of bacteria playing a role in this mechanism.

Using a Model of Germ-Free Animals to Study the Impact of Gut Microbiome in Research: A Step by Step Sterility Setting and Management.

The particularly unique composition of the gut microbiota has the potential to influence the health or disease status of animal and human hosts. Altering the homeostasis of the host-bacteria could lead to changes in gut flora that result in disease or activation of a specific immunological response, which could explain the variations observed in patient responses to current therapies. A standardized model is crucial for studying the influence of the gut microbiota on therapeutic modalities. A step by step mouse model and sterility management system that compares a control strain of C57BL/6 mice to the established C57BL/6 germ-free (GF) strain has been developed. The GF BL/6 mouse phenotype is well established, and the anatomical differences between the GF and control mice were evident in this model. This method could be applied to research studies investigating the microbiome impact, the response to various therapies, or disease transfer via fecal transplants. A standardized sterility maintenance method is crucial in this context.

Cytokine Effects on the Entry of Filovirus Envelope Pseudotyped Virus-Like Particles into Primary Human Macrophages.

Macrophages are one of the first and also a major site of filovirus replication and, in addition, are a source of multiple cytokines, presumed to play a critical role in the pathogenesis of the viral infection. Some of these cytokines are known to induce macrophage phenotypic changes in vitro, but how macrophage polarization may affect the cell susceptibility to filovirus entry remains largely unstudied. We generated different macrophage subsets using cytokine pre-treatment and subsequently tested their ability to fuse with beta-lactamase containing virus-like particles (VLP), pseudotyped with the surface glycoprotein of Ebola virus (EBOV) or the glycoproteins of other clinically relevant filovirus species. We found that pre-incubation of primary human monocyte-derived macrophages (MDM) with interleukin-10 (IL-10) significantly enhanced filovirus entry into cells obtained from multiple healthy donors, and the IL-10 effect was preserved in the presence of pro-inflammatory cytokines found to be elevated during EBOV disease. In contrast, fusion of IL-10-treated macrophages with influenza hemagglutinin/neuraminidase pseudotyped VLPs was unchanged or slightly reduced. Importantly, our in vitro data showing enhanced virus entry are consistent with the correlation established between elevated serum IL-10 and increased mortality in filovirus infected patients and also reveal a novel mechanism that may account for the IL-10-mediated increase in filovirus pathogenicity.

Electron-Beam-Lithographed Nanostructures as Reference Materials for Label-Free Scattered-Light Biosensing of Single Filoviruses.

Optical biosensors based on scattered-light measurements are being developed for rapid and label-free detection of single virions captured from body fluids. Highly controlled, stable, and non-biohazardous reference materials producing virus-like signals are valuable tools to calibrate, evaluate, and refine the performance of these new optical biosensing methods. To date, spherical polymer nanoparticles have been the only non-biological reference materials employed with scattered-light biosensing techniques. However, pathogens like filoviruses, including the Ebola virus, are far from spherical and their shape strongly affects scattered-light signals. Using electron beam lithography, we fabricated nanostructures resembling individual filamentous virions attached to a biosensing substrate (silicon wafer overlaid with silicon oxide film) and characterized their dimensions with scanning electron and atomic force microscopes. To assess the relevance of these nanostructures, we compared their signals across the visible spectrum to signals recorded from Ebola virus-like particles which exhibit characteristic filamentous morphology. We demonstrate the highly stable nature of our nanostructures and use them to obtain new insights into the relationship between virion dimensions and scattered-light signal.

Epigenetics of cartilage diseases.

Osteoarticular diseases, such as arthritis or osteoarthritis, are multifactorial diseases with an underlying genetic etiology that are challenging to study. Genome-Wide Association studies (GWAS) have identified several genetic loci associated with these diseases. Epigenetics is a complex mechanism of chromatin and gene modulation through DNA methylation, histone deacetylation or microRNA, which might contribute to the inheritability of disease. Some of these mechanisms have been studied for decades in other diseases or as part of the aging process, where epigenetic changes seem to play an important role. With the implementation of better technological tools, such as the Illumina next generation sequencing, altered methylation of DNA has been linked to articular diseases and these mechanisms have been shown to regulate metalloprotease (MMP) expression and cartilage matrix integrity. Some miRNA have also been identified and more extensively characterized, such as delineation of the role played by miR-140 in chondrogenesis, followed by the discovery of numerous miRNA potentially involved in the epigenetic regulation of osteoarthritic disease. Histone deacetylases have long been linked to aging, particularly with respect to the Sirtuin family with Sirt1 as the major player. Because aging is the major risk factor for osteoarthritis, the involvement of Sirtuins in the etiology of osteoarthritis has been suggested and investigated. All of these fine regulations together shed new light on cartilage disease pathophysiology. We present in this short review an update of the role of these pathways in articular diseases.

FDA approval: ado-trastuzumab emtansine for the treatment of patients with HER2-positive metastatic breast cancer.

On February 22, 2013, the FDA licensed ado-trastuzumab emtansine (Kadcyla; Genentech, Inc.) for use as a single agent for the treatment of patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) who previously received trastuzumab and a taxane, separately or in combination. The clinical basis for licensure was a phase III trial in 991 patients with HER2-positive MBC that randomly allocated patients to receive ado-trastuzumab emtansine (n=495) or lapatinib in combination with capecitabine (n=496). The coprimary endpoints were progression-free survival (PFS) based on tumor assessments by an independent review committee and overall survival (OS). Statistically significant improvements in PFS and OS were observed in patients receiving ado-trastuzumab emtansine compared with patients receiving lapatinib plus capecitabine [difference in PFS medians of 3.2 months, HR, 0.65 (95% confidence interval, CI, 0.55-0.77), P<0.0001 and difference in OS medians of 5.8 months, HR, 0.68 (95% CI, 0.55-0.85), P=0.0006]. The most common adverse reactions in patients receiving ado-trastuzumab emtansine were fatigue, nausea, musculoskeletal pain, thrombocytopenia, headache, increased aminotransferase levels, and constipation. Other significant adverse reactions included hepatobiliary disorders and left ventricular dysfunction. Given the PFS and OS results, the benefit-risk profile was considered favorable.

Heme oxygenase-1 induction alters chemokine regulation and ameliorates human immunodeficiency virus-type-1 infection in lipopolysaccharide-stimulated macrophages.

We have elucidated a putative mechanism for the host resistance against HIV-1 infection of primary human monocyte-derived macrophages (MDM) stimulated with lipopolysaccharide (LPS). We show that LPS-activated MDM both inhibited HIV-1 entry into the cells and were refractory to post-entry productive viral replication. LPS-treated cells were virtually negative for mature virions as revealed by transmission electron microscopy. LPS activation of MDM markedly enhanced the expression of heme oxygenase-1 (HO-1), a potent inducible cytoprotective enzyme. Increased HO-1 expression was accompanied by elevated production of macrophage inflammatory chemokines (MIP1α and MIP1ß) by LPS-activated MDM, significantly decreased surface chemokine receptor-5 (CCR-5) expression, and substantially reduced virus replication. Treatment of cells with HO-1 inhibitor SnPP IX (tin protoporphyrin IX) attenuated the LPS-mediated responses, HIV-1 replication and secretion of MIP1α, MIP1ß, and LD78ß chemokines with little change in surface CCR-5 expression. These results identify a novel role for HO-1 in the modulation of host immune response against HIV infection of MDM.

Cell-type specific requirements for thiol/disulfide exchange during HIV-1 entry and infection.

BACKGROUND: The role of disulfide bond remodeling in HIV-1 infection is well described, but the process still remains incompletely characterized. At present, the data have been predominantly obtained using established cell lines and/or CXCR4-tropic laboratory-adapted virus strains. There is also ambiguity about which disulfide isomerases/reductases play a major role in HIV-1 entry, as protein disulfide isomerase (PDI) and/or thioredoxin (Trx) have emerged as the two enzymes most often implicated in this process. RESULTS: We have extended our previous findings and those of others by focusing on CCR5-using HIV-1 strains and their natural targets--primary human macrophages and CD4+ T lymphocytes. We found that the nonspecific thiol/disulfide exchange inhibitor, 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), significantly reduced HIV-1 entry and infection in cell lines, human monocyte-derived macrophages (MDM), and also phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMC). Subsequent studies were performed using specific anti-PDI or Trx monoclonal antibodies (mAb) in HIV-1 envelope pseudotyped and wild type (wt) virus infection systems. Although human donor-to-donor variability was observed as expected, Trx appeared to play a greater role than PDI in HIV-1 infection of MDM. In contrast, PDI, but not Trx, was predominantly involved in HIV-1 entry and infection of the CD4+/CCR5+ T cell line, PM-1, and PHA-stimulated primary human T lymphocytes. Intriguingly, both PDI and Trx were present on the surface of MDM, PM-1 and PHA-stimulated CD4+ T cells. However, considerably lower levels of Trx were detected on freshly isolated CD4+ lymphocytes, compared to PHA-stimulated cells. CONCLUSIONS: Our findings clearly demonstrate the role of thiol/disulfide exchange in HIV-1 entry in primary T lymphocytes and MDM. They also establish a cell-type specificity regarding the involvement of particular disulfide isomerases/reductases in this process and may provide an explanation for differences among previously published studies. More importantly, from an in vivo perspective, the preferential utilization of PDI may be relevant to the HIV-1 entry and establishment of virus reservoirs in resting CD4+ cells, while the elevated levels of Trx reported in the chronic stages of HIV-1 infection may facilitate the virus entry in macrophages and help to sustain high viremia during the decline of T lymphocytes.

U.S. Food and Drug Administration approval summary: brentuximab vedotin for the treatment of relapsed Hodgkin lymphoma or relapsed systemic anaplastic large-cell lymphoma.

The U.S. Food and Drug Administration (FDA) describes the accelerated approval of brentuximab vedotin for patients with relapsed Hodgkin lymphoma and relapsed systemic anaplastic large-cell lymphoma (sALCL). FDA analyzed the results of two single-arm trials, enrolling 102 patients with Hodgkin lymphoma and 58 patients with sALCL. Both trials had primary endpoints of objective response rate (ORR) and key secondary endpoints of response duration and complete response (CR) rate. For patients with Hodgkin lymphoma, ORR was 73% (95% CI, 65-83%); median response duration was 6.7 months, and CR was 32% (95% CI, 23-42%). For patients with sALCL, ORR was 86% (95% CI, 77-95%), median response duration was 12.6 months, and CR was 57% (95% CI, 44-70%). The most common adverse reactions were neutropenia, peripheral sensory neuropathy, fatigue, nausea, anemia, upper respiratory infection, diarrhea, pyrexia, rash, thrombocytopenia, cough, and vomiting. FDA granted accelerated approval of brentuximab vedotin for the treatment of patients with Hodgkin lymphoma after failure of autologous stem cell transplantation (ASCT) or after failure of at least two prior multiagent chemotherapy regimens in patients who are not ASCT candidates, and for the treatment of patients with sALCL after failure of at least one prior multiagent chemotherapy regimen.

Risk mitigation strategies for viral contamination of biotechnology products: consideration of best practices.

CONFERENCE PROCEEDING Proceedings of the PDA/FDA Adventitious Viruses in Biologics: Detection and Mitigation Strategies Workshop in Bethesda, MD, USA; December 1-3, 2010 Guest Editors: Arifa Khan (Bethesda, MD), Patricia Hughes (Bethesda, MD) and Michael Wiebe (San Francisco, CA) Viral contamination of biotech product facilities is a potentially devastating manufacturing risk and, unfortunately, is more common than is generally reported or previously appreciated. Although viral contaminants of biotech products are thought to originate principally from biological raw materials, all potential process risks merit evaluation. Limitations to existing methods for virus detection are becoming evident as emerging viruses have contaminated facilities and disrupted supplies of critical products. New technologies, such as broad-based polymerase chain reaction screens for multiple virus types, are increasingly becoming available to detect adventitious viral contamination and thus, mitigate risks to biotech products and processes. Further, the industry embrace of quality risk management that promotes improvements in testing stratagems, enhanced viral inactivation methods for raw materials, implementation and standardization of robust viral clearance procedures, and efforts to learn from both epidemiologic screening of raw material sources and from the experience of other manufacturers with regard to this problem will serve to enhance the safety of biotech products available to patients. Based on this evolving landscape, we propose a set of principles for manufacturers of biotech products: Pillars of Risk Mitigation for Viral Contamination of Biotech Products.

Cell adhesion-dependent membrane trafficking of a binding partner for the ebolavirus glycoprotein is a determinant of viral entry.

Ebolavirus is a hemorrhagic fever virus associated with high mortality. Although much has been learned about the viral lifecycle and pathogenesis, many questions remain about virus entry. We recently showed that binding of the receptor binding region (RBR) of the ebolavirus glycoprotein (GP) and infection by GP pseudovirions increase on cell adhesion independently of mRNA or protein synthesis. One model to explain these observations is that, on cell adhesion, an RBR binding partner translocates from an intracellular vesicle to the cell surface. Here, we provide evidence for this model by showing that suspension 293F cells contain an RBR binding site within a membrane-bound compartment associated with the trans-Golgi network and microtubule-organizing center. Consistently, trafficking of the RBR binding partner to the cell surface depends on microtubules, and the RBR binding partner is internalized when adherent cells are placed in suspension. Based on these observations, we reexamined the claim that lymphocytes, which are critical for ebolavirus pathogenesis, are refractory to infection because they lack an RBR binding partner. We found that both cultured and primary human lymphocytes (in suspension) contain an intracellular pool of an RBR binding partner. Moreover, we identified two adherent primate lymphocytic cell lines that bind RBR at their surface and strikingly, support GP-mediated entry and infection. In summary, our results reveal a mode of determining viral entry by a membrane-trafficking event that translocates an RBR binding partner to the cell surface, and they suggest that this process may be operative in cells important for ebolavirus pathogenesis (e.g., lymphocytes and macrophages).

Platelet factor 4 (CXCL4) facilitates human macrophage infection with HIV-1 and potentiates virus replication.

Platelet factor 4 (CXCL4), a member of the CXC chemokine subfamily released in high amounts by activated platelets, has been identified as a monocyte survival factor that induces monocyte differentiation into macrophages. Although CXCL4 has been shown to have biological effects unique to chemokines, nothing is known about the role of CXCL4-derived human macrophages or CXCL4 in human immunodeficiency virus (HIV) disease. In this study, CXCL4-derived macrophages are compared with macrophage-colony stimulating factor (M-CSF)-derived macrophages for their ability to support HIV-1 replication. We show that CXCL4-derived macrophages can be infected with macrophage-tropic HIV-1 that uses either CC-chemokine receptor 5 (CCR5) or CXC-chemokine receptor 4 (CXCR4) as a co-receptor for viral entry. We also find that M-CSF and the chemokines, monocyte chemoattractant protein 1 (MCP-1; CCL2) and macrophage-inflammatory-protein-1-alpha (MIP-1alpha; CCL3) are produced upon R5- and X4-tropic HIV-1 replication in both M-CSF- and CXCL4-derived human macrophages. In addition, CXCL4 added to M-CSF-derived macrophages after virus adsorption and maintained throughout the infection enhances HIV-1 replication. We thus propose a novel role for CXCL4 in HIV disease.

beta-Estradiol attenuates the anti-HIV-1 efficacy of Stavudine (D4T) in primary PBL.

BACKGROUND: Female hormones are known to play an important role in predisposition for many infectious diseases. Recent work suggests there are gender effects in HIV/AIDS progression. Here we ask whether the sex steroid hormone beta-estradiol affects the replication of HIV-1 or the efficacy of a common anti-retroviral drug, Stavudine (D4T). RESULTS: Human PBL were infected with HIV-1 in the presence or absence of combinations of sex steroid hormones and the anti-retroviral drug, D4T. After seven days in culture, viral supernatants were assayed for HIV-1 p24 protein. beta-estradiol resulted in a modest inhibition of HIV-1 replication of approximately 26%. However, 2 nM beta-estradiol increased the amount of HIV-1 replication in the presence of 50 nM D4T from a baseline of 33% (+/- SE = 5.4) to 74% (+/- SE = 5.4) of control virus levels in the absence of drug. Both results were statistically highly significant (p < 0.001). beta-estradiol did not increase the replication of a D4T-resistant strain of HIV in the presence of D4T. The effects were unlikely to be due to general cell inhibition or toxicity because these concentrations of drug and hormone cause no cytotoxicity in PBL as measured by trypan blue exclusion. CONCLUSION: beta-estradiol inhibited both HIV-1 replication in primary human PBL and the antiretroviral efficacy of D4T in PBL cultures. To optimize antiretroviral drug therapy, it may be necessary to monitor patient hormonal status.

APOBEC3G-independent reduction in virion infectivity during long-term HIV-1 replication in terminally differentiated macrophages.

APOBEC3G (APO3G) is a cellular cytidine deaminase with potent antiviral activity. In the case of HIV, the antiviral activity of APO3G is counteracted by the viral Vif protein. Monocyte-derived macrophages (MDM) are terminally differentiated, non-dividing cells susceptible to HIV infection. Human MDM are known to express APO3G and HIV replication in these cells is dependent on Vif. Here we analyzed the correlation between HIV-1 replication and APO3G expression in MDM. Replication of wild type HIV-1 induced a gradual 4-5-fold reduction in APO3G expression. The efficiency of APO3G downregulation correlated with the efficiency of virus replication. Interestingly, despite downregulation of APO3G, the relative infectivity of viruses rapidly declined during the course of infection and was already reduced approximately 90% prior to peak virus production. Cell-free virus preparations showed increased levels of a 41 kDa MA-CA processing intermediate. Sequence analysis around the MA-CA cleavage site and the protease and LTR regions did not reveal deaminase-induced hypermutation of the viral genome, suggesting that APO3G activity is not responsible for the incomplete Gag processing. Thus, the loss of infectivity of HIV-1 viruses produced from long-term infected primary macrophages is due to an APO3G-independent mechanism.