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Abstract Background Although FeHV-1 is a primary feline pathogen, little is known about its interactions with host cells. Its relationship with several cellular pathways has recently been described, whereas its interplay with the apoptotic process, unlike other herpesviruses, has not yet been clarified. The aim of this work was to evaluate whether FeHV-1 induces apoptosis in its permissive cells, as well as the pathway involved and the effects of induction and inhibition of apoptosis on viral replication. Methods Monolayers of CRFK cells were infected at different times with different viral doses. A cytofluorimetric approach allowed the quantification of cells in early and late apoptosis. All infections and related controls were also subjected to Western blot analysis to assess the expression of apoptotic markers (caspase 3-8-9, Bcl-2, Bcl-xL, NF-κB). An inhibitor (Z-VAD-FMK) and an inducer (ionomycin) were used to evaluate the role of apoptosis in viral replication. Finally, the expression of autophagy markers during the apoptosis inhibition/induction and the expression of apoptosis markers during autophagy inhibition/induction were evaluated to highlight any crosstalk between the two pathways. Results FeHV-1 triggered apoptosis in a time- and dose-dependent manner. Caspase 3 cleavage was evident 48 h after infection, indicating the completeness of the process at this stage. While caspase 8 was not involved, caspase 9 cleavage started 24 h post-infection. The expression of other mitochondrial damage markers also changed, suggesting that apoptosis was induced via the intrinsic pathway. NF- κB was up-regulated at 12 h, followed by a gradual decrease in levels up to 72 h. The effects of apoptosis inhibitors and inducers on viral replication and autophagy were also investigated. Inhibition of caspases resulted in an increase in viral glycoprotein expression, higher titers, and enhanced autophagy, whereas induction of apoptosis resulted in a decrease in viral protein expression, lower viral titer, and attenuated autophagy. On the other hand, the induction of autophagy reduced the cleavage of caspase 3. Conclusions In this study, we established how FeHV-1 induces the apoptotic process, contributing to the understanding of the relationship between FeHV-1 and this pathway.

FeHV-1 is a member of the Herpesviridae family that is distributed worldwide and causes feline viral rhinotracheitis (FVR). Since its relationship with the autophagic process has not yet been elucidated, the aim of this work was to evaluate the autophagy mediated by FeHV-1 and to determine its proviral or antiviral role. Our data showed that autophagy is induced by FeHV-1 in a viral dose and time-dependent manner. Phenotypic changes in LC3/p62 axis (increase of LC3-II and degradation of p62) were detected from 12 h post infection using western blot and immuno-fluorescence assays. In a second step, by using late autophagy inhibitors and inducers, the possible proviral role of autophagy during FeHV-1 infection was investigating by assessing the effects of each chemical in terms of viral yield, cytotoxic effects, and expression of viral glycoproteins. Our findings suggest that late-stage autophagy inhibitors (bafilomycin and chloroquine) have a negative impact on viral replication. Interestingly, we observed an accumulation of gB, a viral protein, when cells were pretreated with bafilomycin, whereas the opposite effect was observed when an autophagy inducer was used. The importance of autophagy during FeHV-1 infection was further supported by the results obtained with ATG5 siRNA. In summary, this study demonstrates FeHV-1-mediated autophagy induction, its proviral role, and the negative impact of late autophagy inhibitors on viral replication.

Jacobaea is a small genus of plants belonging to Asteraceae family, formerly joint to Senecio genus, that includes more than 60 species and sub-species. Several taxa of this genus have been extensively studied both for their non-volatile and volatile metabolites. In the present study the chemical composition of the essential oil (EO) from aerial parts of Jacobaea delphiniifolia (Vahl) Pelser & Veldkamp, collected in Sicily, was analyzed by GC–MS. No one report has been previously published on the EO of this species. The result showed the presence of a large quantity of two metabolites, namely 1-undecene (63.57%) and thymol methyl ether (13.65%). Chemotaxonomic considerations were carried out by comparing the other oils of Jacobaea taxa studied so far. [ABSTRACT FROM AUTHOR]

Abstract The coronavirus disease (COVID‐19), during its course, may involve several organs, including the skin with a petechial skin rash, urticaria and erythematous rash, or varicella‐like eruption, representing an additional effect of the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection, as commonly observed in other viral diseases. Considering that symptomatic patients with COVID‐19 generally undergo multidrug treatments, the occurrence of a possible adverse drug reaction presenting with cutaneous manifestations should be contemplated. Pleomorphic skin eruptions occurred in a 59‐year‐old Caucasian woman, affected by a stable form of chronic lymphocytic leukemia, and symptomatic SARS‐CoV‐2 infection, treated with a combination of hydroxychloroquine sulfate, darunavir, ritonavir, sarilumb, omeprazole, ceftriaxone, high‐flow oxygen therapy devices, filgrastim (Zarzio®) as a single injection, and enoxaparin. The patient stopped all treatment but oxygen and enoxaparin were continued and the patient received a high‐dose Desametasone with complete remission of dermatological impairment in 10 days. It is very important to differentially diagnose COVID‐19 disease‐related cutaneous manifestations, where is justified to continue the multidrug antiviral treatment, from those caused by an adverse drug reaction, where it would be necessary to identify the possible culprit drug and to start appropriate antiallergic treatment.

Category: Sports; Hindfoot Introduction/Purpose: Plantar fasciopathy (PF) is a common orthopaedic condition which often affects athletes and limits their performance. Our aim was to conduct a scoping review of the literature in order to summarise the evidence provided so far in the management of PF in Elite Athletes and identify potential gaps in the current knowledge. Methods: This scoping review followed the six-stage methodological framework of Arksey and O'Malley and was registered in the Open Science Framework (10.17605/OSF.IO/48S3K). Pubmed, Scopus and Web of Science were used to identify elegible papers. After charting of data, studies were pooled into three categories: 1) epidemiological/diagnostic studies, 2) outcome research and 3) studies on the rupture of the plantar fascia. The modified Coleman Methodology Score (mMCS) was used to assess the quality of manuscripts included. Results: Out of 742 initial studies, 10 were selected (109 patients) including 8 Level IV and 2 Level V articles. In four studies (91 athletes), potential risk factors (i.e. pre-existent thickening of the fascia, spike shoes, varus hindfoot/knee alignment) were discussed. In three studies (6 athletes), focusing on plantar fasciitis, the non-surgical treatment led to a satisfactory but poorly- documented outcome. In three studies (12 athletes), the rupture of the fascia was treated conservatively with contrasting results, while surgery was performed only in 2 cases. The mean mCMS was 19 (range, 3 to 42), demonstrating overall poor methodology. Conclusion: The limited number of studies and their poor quality do not allow to define the gold standard treatment of PF in Elite Athletes. Until high-quality studies are provided, clinicians have to rely on the available literature regarding the non- professional or non-athletic population to make the best evidence-based decision.

Category: Other; Basic Sciences/Biologics Introduction/Purpose: Achilles tendon injuries represent one of the most common reasons of referral to orthopaedic surgeons. The purpose of this study was to determine the 50 most-cited articles on Achilles tendon pathologies in order to outline their characteristics, examine trends in publication and evaluate the correlation between citations and the quality of evidence. Methods: We searched Web of Science papers with the single keyword 'Achill*'. We identified and analyzed the top 50 most- cited articles and abstracted their characteristics. The methodological quality was assessed using the modified Coleman Methodology Score (mCMS). The correlation between the number of citations, the citation rate (citations/y), the impact factor of the journal for the year 2020 (JIF), the year of publication, the Level of Evidence (LoE), the type of study (tendon rupture, acute tendinopathy, chronic tendinopathy), the sample size and the mCMS was assessed through multiple bivariate analyses (Pearson or Spearman correlation coefficient). Results: Mean number of citations (+-SD) was 244 +- 88.8 (range, 657 to 157), with a total number of citations of 12.194 and a mean citation rate of 12.6 +- 5.4 (range, 28 to 3). The mean impact factor for the ten journals in which the 50 manuscripts were published was 5.1. The citation rate correlated with the number of citations (R=0.56, p

Sirtuin 1 (SIRT1) is a protein involved in aging, cell protection, and energy metabolism in mammals. Recently, SIRT1 has been intensively studied in medical oncology, but the role of SIRT1 is still controversial, as it has been proposed as both an oncogene and a tumor suppressor. The aim of this study is to investigate the expression of SIRT1 by immunohistochemistry in canine mammary tissues, and by Western blot and immunofluorescence analysis in different canine mammary cell lines. Our results showed a decrease in SIRT1 expression from normal mammary gland tissue, and from benign and well-differentiated malignant tumors (G1) to less differentiated ones (G2–G3). Furthermore, a shift in the subcellular localization of SIRT1 from the nucleus to the cytoplasm was observed in less differentiated malignant tumors. However, further studies are needed to investigate the subcellular localization of SIRT1 in canine cancer cells and the role it may play in oncogenesis in animals.

The genus Capparis is a taxon of difficult delimitation that has several species and ecotypes due to its wide heterogeneity, its extreme phenotypic diversity, and the presence of intermediate forms linked to hybridization phenomena. The Sicilian territory hosts numerous wild and cultivated populations of two spp. Capparis spinosa L. and Capparis orientalis Duhamel, which are ecologically and morphologically distinct. The caper has considerable interest and economic value for its medicinal properties, culinary uses, and cultivation characteristics. It is one of the foods with the highest quercetin content. Quercetin is a flavonol with antioxidant, anti-inflammatory, and immunostimulant properties. Recently, patents and clinical studies have highlighted the inhibitory effect of this compound against several SARS-CoV-2 enzymes (MPro, PLPro, and RdRp). Therefore, the aim of this study was to quantify the amount of quercetin in C. spinosa and C. orientalis by LC-ESI/QTrap/MS/MS and to correlate it with the pedoclimatic features. The results obtained showed that quercetin is more abundant in C. orientalis than in C. spinosa. The highest values of quercetin were recorded in C. orientalis flowers, leaves, and flower buttons of volcanic islands with southwest and east warm exposures. In conclusion, the data acquired can provide a good basis for further scientific investigations to support the identification of possible ecotypes as a source of quercetin for food or pharmaceutical purposes.

Background: Low-level HIV viremia originating from virus reactivation in HIV reservoirs is often present in cART treated individuals and represents a persisting source of immune stimulation associated with sub-optimal recovery of CD4+ T cells. The HIV-1 Tat protein is released in the extracellular milieu and activates immune cells and latent HIV, leading to virus production and release. However, the relation of anti-Tat immunity with residual viremia, persistent immune activation and CD4+ T-cell dynamics has not yet been defined. Methods: Volunteers enrolled in a 3-year longitudinal observational study were stratified by residual viremia, Tat serostatus and frequency of anti-Tat cellular immune responses. The impact of anti-Tat immunity on low-level viremia, persistent immune activation and CD4+ T-cell recovery was investigated by test for partitions, longitudinal regression analysis for repeated measures and generalized estimating equations. Findings: Anti-Tat immunity is significantly associated with higher nadir CD4+ T-cell numbers, control of low-level viremia and long-lasting CD4+ T-cell recovery, but not with decreased immune activation. In adjusted analysis, the extent of CD4+ T-cell restoration reflects the interplay among Tat immunity, residual viremia and immunological determinants including CD8+ T cells and B cells. Anti-Env immunity was not related to CD4+ T-cell recovery. Interpretation: Therapeutic approaches aiming at reinforcing anti-Tat immunity should be investigated to improve immune reconstitution in people living with HIV on long-term cART. Trial registration: ISS OBS T-002 ClinicalTrials.gov identifier: NCT01024556 Funding: Italian Ministry of Health, special project on the Development of a vaccine against HIV based on the Tat protein and Ricerca Corrente 2019/2020.

The etiology of spontaneous cranial cruciate ligament rupture in dogs is unknown despite being one of the most impacting orthopedic diseases in dogs. Numerous studies have contributed to the understanding of a multifactorial pathogenesis, this, however, without identifying a pivotal link to explain progressive collagen degeneration and osteoarthritic changes. In human medicine, recent reports have identified relaxin as a triggering factor in ligament ruptures in knee and metacarpal joints. We thus hypothesized that relaxin might also play a role in canine cruciate ligament rupture. Relaxin’s primarily known property is connective tissue remodeling through collagenolysis. We therefore investigated relaxin and its cognate receptors LGR7/LGR8 in 18 dogs with cranial cruciate ligament disease (CCLD) and compared them to a group of dogs with normal stifle joints. Applying immunohistochemistry (IHC), double immunofluorescence (dIF), and western blot analysis (WB), we found strong and significantly increased expression of both relaxin and its receptors in ruptured cruciate ligaments, and in synovial membranes. Pattern of immuno-staining on dIF strongly suggests relaxin binding to primed receptors and activation of signaling properties, which in turn may have affected collagen matrix metabolism. Thus, in canine cranial cruciate ligament disease, relaxin/receptor signaling may be a primary trigger for collagen fiber degradation and collagen lysis, eventually followed by ligament rupture.

Com base na premissa de que o núcleo central de uma representação social é uma narrativa, recorremos aos estudos de Jerome Bruner e de Serge Moscovici para pensar alternativas que favoreçam mudanças de representações sociais na formação docente. Propomos uma reflexão sobre as imagens do fractal e da fita de Möbius como metáforas para ilustrar como entendemos as narrativas enquanto uma unidade no núcleo de uma representação social, admitindo que elas são a um só tempo constitutivas de representações sociais e constituídas por elas. Nesse sentido, o recurso às narrativas como modalidade de intervenção na formação docente permitiria, simultaneamente, operar mudanças de representações sociais e promover a ressignificação de práticas pedagógicas.

Introduction: In spite of its success at suppressing HIV replication, combination antiretroviral therapy (cART) only partially reduces immune dysregulation and loss of immune functions. These cART-unmet needs appear to be due to persistent virus replication and cell-to-cell transmission in reservoirs, and are causes of increased patients’ morbidity and mortality. Up to now, therapeutic interventions aimed at cART-intensification by attacking the virus reservoir have failed. Areas covered: We briefly review the rationale and clinical development of Tat therapeutic vaccine in cART-treated subjects in Italy and South Africa (SA). Vaccination with clade-B Tat induced cross-clade neutralizing antibodies, immune restoration, including CD4+ T cell increase particularly in low immunological responders, and reduction of proviral DNA. Phase III efficacy trials in SA are planned both in adult and pediatric populations. Expert commentary: We propose the Tat therapeutic vaccine as a pathogenesis-driven intervention that effectively intensifies cART and may lead to a functional cure and provide new perspectives for prevention and virus eradication strategies.

Deregulation of fatty acid catabolism provides an alternative energy source to glycolysis for cancer cell survival and proliferation. The regulator enzymes of the carnitine system (CS), responsible for the transport of fatty acids across mitochondrial membranes for β-oxidation are deregulated in tumorigenesis. Recently, we found that Carnitine Palmitoyl Transferase 1 (CPT1), a crucial regulator of CS components, is expressed and dysregulated in canine mammary tumor (CMT) tissues and cells. In this study, we examined the protein expression of the three remaining enzymes of CS (Carnitine Acylcarnitine Translocase (CACT), Carnitine Palmitoyl Transferase 2 (CPT2), Carnitine O-acetyltransferase (CrAT), in canine mammary cells and tissues by Western blot and immunohistochemistry. Protein expression of the components of CS was found in normal mammary glands and a concomitant deregulation of expression in CMT tissues that inversely correlated with the degree of tumor differentiation. Moreover, the expression and a different deregulation of CS-related proteins was also observed in CF33, CMT-U27, CMT-U309, and P114 cell lines used as in vitro model. These results demonstrate for the first time the expression of CS components in CMT tissues and cancer cells; however, further studies are needed to elucidate their roles in dogs as well.

Abstract Physical activity has been demonstrated to be effective in the prevention and treatment of different chronic conditions, including type 2 diabetes (T2D). In particular, several studies highlighted how the beneficial effects of physical activity may be related to the stability of the DNA molecule, such as longer telomeric ends. Here we analyze the effect of exercise training on telomere length, spontaneous and H2O2-induced DNA damage, as well as the apoptosis level in leukocytes from untrained or trained T2D patients vs. age-matched control subjects (CS) (57–66 years). Moreover, expression analysis of selected genes belonging to DNA repair systems, cell cycle control, antioxidant and defence systems was performed. Subjects that participated in a regular exercise program showed a longer telomere sequence than untrained counterparts. Moreover, ex vivo treatment of leukocytes with H2O2 highlighted that: (1) oxidative DNA damage induced similar telomere attrition in all groups; (2) in T2D subjects, physical activity seemed to prevent a significant increase of genomic oxidative DNA damage induced by chronic exposure to pro-oxidant stimulus, and (3) decreased the sensitivity of leukocytes to apoptosis. Finally, the gene expression analysis in T2D subjects suggested an adaptive response to prolonged exercise training that improved the response of specific genes.

Introduction: Tat, a key HIV virulence protein, has been targeted for the development of a therapeutic vaccine aimed at cART intensification. Results from phase II clinical trials in Italy (ISS T-002) and South Africa (ISS T-003) indicated that Tat vaccination promotes increases of CD4+ T-cells and return to immune homeostasis while reducing the virus reservoir in chronically cART-treated patients. Here we present data of 92 vaccinees (59% of total vaccinees) enrolled in the ISS T-002 8-year extended follow-up study (ISS T-002 EF-UP, ClinicalTrials.gov NCT02118168).Results: Anti-Tat antibodies (Abs) induced upon vaccination persisted for the entire follow-up in 34/92 (37%) vaccinees, particularly when all 3 Ab classes (A/G/M) were present (66% of vaccinees), as most frequently observed with Tat 30 μg regimens. CD4+ T cells increased above study-entry levels reaching a stable plateau at year 5 post-vaccination, with the highest increase (165 cells/μL) in the Tat 30 μg, 3 × regimen. CD4+ T-cell increase occurred even in subjects with CD4+ nadir ≤ 250 cells/uL and in poor immunological responders and was associated with a concomitant increase of the CD4+/CD8+ T-cell ratio, a prognostic marker of morbidity/mortality inversely related to HIV reservoir size. Proviral DNA load decreased over time, with a half-life of 2 years and an estimated 90% reduction at year 8 in the Tat 30 μg, 3 × group. In multivariate analysis the kinetic and amplitude of both CD4+ T-cell increase and proviral DNA reduction were fastest and highest in subjects with all 3 anti-Tat Ab classes and in the 30 μg, 3 × group, irrespective of drug regimens (NNRTI/NRTI vs. PI). HIV proviral DNA changes from baseline were inversely related to CD4+/CD8+ T-cell ratio and CD4+ T-cell changes, and directly related to the changes of CD8+ T cells. Further, HIV DNA decay kinetics were inversely related to the frequency and levels of intermittent viremia. Finally, Tat vaccination was similarly effective irrespective of the individual immunological status or HIV reservoir size at study entry.Conclusions: Tat immunization induces progressive immune restoration and reduction of virus reservoirs above levels reached with long-term cART, and may represent an optimal vaccine candidate for cART intensification toward HIV reservoirs depletion, functional cure, and eradication strategies.

Simple Summary: Sirtuin family proteins (SIRTs) are intra-cellular enzymes that are found in mammals. They have a regulatory function in genomic transcription and are involved in a variety of physiologic mechanisms, such as aging and genome stability. Of these enzymes, SIRT1, the most investigated, may also be involved in cancerogenesis, although its possible dual role as an onco-suppressor and/or tumor promoter under a variety of biological conditions in humans and animals is still controversial. In normal or neoplastic canine mammary tissues, SIRT1 has not yet been investigated. We examined the cellular and subcellular distribution of SIRT1 in non-neoplastic (n = 5) and neoplastic (n = 45) mammary tissue samples of dogs using immunohistochemistry. In addition, we examined the expression and subcellular localization of SIRT1 in cultured canine mammary cancer cells by Western blot and immunofluorescence analyses. We found abundant and mainly nuclear expression in normal glandular cells; expression progressively weakened in mammary cancer cells in correlation with histologic features of increasing malignancy. In addition to weakening expression, a shift in the subcellular SIRT1 expression from predominantly nuclear to largely cytoplasmatic was also observable. In cultured canine cancer cells, subcellular localization was cytoplasmatic throughout. Our results suggest that SIRT1 may play a tumor0protecting role in canine mammary tumors, as deductible from the shifts in subcellular localization. Sirtuin 1 (SIRT1) is a protein involved in aging, cell protection, and energy metabolism in mammals. Recently, SIRT1 has been intensively studied in medical oncology, but the role of SIRT1 is still controversial, as it has been proposed as both an oncogene and a tumor suppressor. The aim of this study is to investigate the expression of SIRT1 by immunohistochemistry in canine mammary tissues, and by Western blot and immunofluorescence analysis in different canine mammary cell lines. Our results showed a decrease in SIRT1 expression from normal mammary gland tissue, and from benign and well-differentiated malignant tumors (G1) to less differentiated ones (G2–G3). Furthermore, a shift in the subcellular localization of SIRT1 from the nucleus to the cytoplasm was observed in less differentiated malignant tumors. However, further studies are needed to investigate the subcellular localization of SIRT1 in canine cancer cells and the role it may play in oncogenesis in animals. [ABSTRACT FROM AUTHOR]

Viscum album L., (Common Mistletoe), is a hemiparasitic shrub that lives on a wide range of woody plant species, known since Neolithic period for its ritual and for pharmacological properties. Up to now, no investigation has been reported on the chemical composition of the essential oils of V. album aerial parts in relation with the diverse host trees. Consequently, the essential oils compositions of three Sicilian accession of V. album, growing on Quercus suber L., Crataegus monogyna Jacq. and Olea europaea L. var. europaea cv. 'Santagatese', respectively, were evaluated by GC-MS. The three populations showed quite different profiles indicating that the nature of the host considerably influences the chemical composition of the guest plant, V. album. [ABSTRACT FROM AUTHOR]

HIV-1 Tat is an essential protein in the virus life cycle, which is required for virus gene expression and replication. Most Tat that is produced during infection is released extracellularly and it plays a key role in HIV pathogenesis, including residual disease upon combination antiretroviral therapy (cART). Here, we review epidemiological and experimental evidence showing that antibodies against HIV-1 Tat, infrequently occurring in natural infection, play a protective role against disease progression, and that vaccine targeting Tat can intensify cART. In fact, Tat vaccination of subjects on suppressive cART in Italy and South Africa promoted immune restoration, including CD4+ T-cell increase in low immunological responders, and a reduction of proviral DNA even after six years of cART, when both CD4+ T-cell gain and DNA decay have reached a plateau. Of note, DNA decay was predicted by the neutralization of Tat-mediated entry of Env into dendritic cells by anti-Tat antibodies, which were cross-clade binding and neutralizing. Anti-Tat cellular immunity also contributed to the DNA decay. Based on these data, we propose the Tat therapeutic vaccine as a pathogenesis-driven intervention that effectively intensifies cART and it may lead to a functional cure, providing new perspectives and opportunities also for prevention and virus eradication strategies.

The genus Capparis is a taxon of difficult delimitation that has several species and ecotypes due to its wide heterogeneity, its extreme phenotypic diversity, and the presence of intermediate forms linked to hybridization phenomena. The Sicilian territory hosts numerous wild and cultivated populations of two spp. Capparis spinosa L. and Capparis orientalis Duhamel, which are ecologically and morphologically distinct. The caper has considerable interest and economic value for its medicinal properties, culinary uses, and cultivation characteristics. It is one of the foods with the highest quercetin content. Quercetin is a flavonol with antioxidant, anti-inflammatory, and immunostimulant properties. Recently, patents and clinical studies have highlighted the inhibitory effect of this compound against several SARS-CoV-2 enzymes (MPro, PLPro, and RdRp). Therefore, the aim of this study was to quantify the amount of quercetin in C. spinosa and C. orientalis by LC-ESI/QTrap/MS/MS and to correlate it with the pedoclimatic features. The results obtained showed that quercetin is more abundant in C. orientalis than in C. spinosa. The highest values of quercetin were recorded in C. orientalis flowers, leaves, and flower buttons of volcanic islands with southwest and east warm exposures. In conclusion, the data acquired can provide a good basis for further scientific investigations to support the identification of possible ecotypes as a source of quercetin for food or pharmaceutical purposes. [ABSTRACT FROM AUTHOR]

Use of Env in HIV vaccine development has been disappointing. Here we show that, in the presence of a biologically active Tat subunit vaccine, a trimeric Env protein prevents in monkeys virus spread from the portal of entry to regional lymph nodes. This appears to be due to specific interactions between Tat and Env spikes that form a novel virus entry complex favoring R5 or X4 virus entry and productive infection of dendritic cells (DCs) via an integrin-mediated pathway. These Tat effects do not require Tat-transactivation activity and are blocked by anti-integrin antibodies (Abs). Productive DC infection promoted by Tat is associated with a highly efficient virus transmission to T cells. In the Tat/Env complex the cysteine-rich region of Tat engages the Env V3 loop, whereas the Tat RGD sequence remains free and directs the virus to integrins present on DCs. V2 loop deletion, which unshields the CCR5 binding region of Env, increases Tat/Env complex stability. Of note, binding of Tat to Env abolishes neutralization of Env entry or infection of DCs by anti-HIV sera lacking anti-Tat Abs, which are seldom present in natural infection. This is reversed, and neutralization further enhanced, by HIV sera containing anti-Tat Abs such as those from asymptomatic or Tat-vaccinated patients, or by sera from the Tat/Env vaccinated monkeys. Thus, both anti-Tat and anti-Env Abs are required for efficient HIV neutralization. These data suggest that the Tat/Env interaction increases HIV acquisition and spreading, as a mechanism evolved by the virus to escape anti-Env neutralizing Abs. This may explain the low effectiveness of Env-based vaccines, which are also unlikely to elicit Abs against new Env epitopes exposed by the Tat/Env interaction. As Tat also binds Envs from different clades, new vaccine strategies should exploit the Tat/Env interaction for both preventative and therapeutic interventions.

Kaposi's sarcoma (KS) is a vascular tumor frequently occurring in Human Immunodeficiency Virus- (HIV-) 1-infected individuals. Our previous work indicated that the angiogenic fibroblast growth factor (FGF)-2 and the Tat protein of HIV-1, both expressed in KS lesions of HIV-infected patients, synergize at inducing angioproliferative, KS-like lesions in mice. Here we show that the development of angioproliferative lesions promoted in mice by combined Tat and FGF-2 associates with an increase in the levels of expression of the antiapoptotic Bcl-2 protein. Upregulation of Bcl-2 expression by combined FGF-2 and Tat occurs also in vitro, and this protects human primary endothelial cells from programmed cell death. As Bcl-2 is expressed in human KS lesions in a fashion paralleling the progression of the disease, these findings suggest a molecular mechanism by which Tat and FGF-2 cooperate in KS maintenance and progression in HIV-infected individuals.