Correlates of Breakthrough SARS-CoV-2 Infections in People with HIV: Results from the CIHR CTN 328 Study.

COVID-19 breakthrough infection (BTI) can occur despite vaccination. Using a multi-centre, prospective, observational Canadian cohort of people with HIV (PWH) receiving ≥2 COVID-19 vaccines, we compared the SARS-CoV-2 spike (S) and receptor-binding domain (RBD)-specific IgG levels 3 and 6 months post second dose, as well as 1 month post third dose, in PWH with and without BTI. BTI was defined as positivity based on self-report measures (data up to last study visit) or IgG data (up to 1 month post dose 3). The self-report measures were based on their symptoms and either a positive PCR or rapid antigen test. The analysis was restricted to persons without previous COVID-19 infection. Persons without BTI remained COVID-19-naïve until ≥3 months following the third dose. Of 289 participants, 92 developed BTI (31.5 infections per 100 person-years). The median days between last vaccination and BTI was 128 (IQR 67, 176), with the most cases occurring between the third and fourth dose (n = 59), corresponding to the Omicron wave. In analyses adjusted for age, sex, race, multimorbidity, hypertension, chronic kidney disease, diabetes and obesity, a lower IgG S/RBD (log10 BAU/mL) at 1 month post dose 3 was significantly associated with BTI, suggesting that a lower IgG level at this time point may predict BTI in this cohort of PWH.

Antibody neutralization capacity after coronavirus disease 2019 vaccination in people with HIV in Canada.

OBJECTIVES: Many vaccines require higher/additional doses or adjuvants to provide adequate protection for people with HIV (PWH). Here, we compare coronavirus disease 2019 (COVID-19) vaccine-induced antibody neutralization capacity in PWH vs. HIV-negative individuals following two vaccine doses. DESIGN: In Canadian prospective observational cohorts, including a multicentre study of PWH receiving at least two COVID-19 vaccinations (mRNA or ChAdOx1-S), and a parallel study of HIV-negative controls (Stop the Spread Ottawa Cohort), we measured vaccine-induced neutralization capacity 3 months post dose 2 (±1 month). METHODS: COVID-19 neutralization efficiency was measured by calculating the half maximal inhibitory dilution (ID50) using a high-throughput protein-based neutralization assay for Ancestral (Wuhan), Delta and Omicron (BA.1) spike variants. Univariable and multivariable quantile regression were used to compare COVID-19-specific antibody neutralization capacity by HIV status. RESULTS: Neutralization assays were performed on 256 PWH and 256 controls based on specimen availability at the timepoint of interest, having received two vaccines and known date of vaccination. There was a significant interaction between HIV status and previous COVID-19 infection status in median ID50. There were no differences in median ID50 for HIV+ vs. HIV-negative persons without past COVID-19 infection. For participants with past COVID-19 infection, median ICD50 was significantly higher in controls than in PWH for ancestral SARS-CoV-2 and Omicron variants, with a trend for the Delta variant in the same direction. CONCLUSION: Vaccine-induced SARS-CoV-2 neutralization capacity was similar between PWH vs. HIV-negative persons without past COVID-19 infection, demonstrating favourable humoral-mediated immunogenicity. Both HIV+ and HIV-negative persons demonstrated hybrid immunity. TRIAL REGISTRATION: clinicaltrials.gov NCT04894448.

Effects of Oral Cannabinoids on Systemic Inflammation and Viral Reservoir Markers in People with HIV on Antiretroviral Therapy: Results of the CTN PT028 Pilot Clinical Trial.

Chronic HIV infection is characterized by persistent inflammation despite antiretroviral therapy (ART). Cannabinoids may help reduce systemic inflammation in people with HIV (PWH). To assess the effects of oral cannabinoids during HIV, ten PWH on ART were randomized (n = 5/group) to increasing doses of oral Δ9-tetrahydrocannabinol (THC): cannabidiol (CBD) combination (2.5:2.5-15:15 mg/day) capsules or CBD-only (200-800 mg/day) capsules for 12 weeks. Blood specimens were collected prospectively 7-21 days prior to treatment initiation and at weeks 0 to 14. Plasma cytokine levels were determined via Luminex and ELISA. Immune cell subsets were characterized by flow cytometry. HIV DNA/RNA were measured in circulating CD4 T-cells and sperm by ultra-sensitive qPCR. Results from both arms were combined for statistical analysis. Plasma levels of IFN-γ, IL-1ß, sTNFRII, and REG-3α were significantly reduced at the end of treatment (p ˂ 0.05). A significant decrease in frequencies of PD1+ memory CD4 T-cells, CD73+ regulatory CD4 T-cells, and M-DC8+ intermediate monocytes was also observed (p ˂ 0.05), along with a transient decrease in CD28-CD57+ senescent CD4 and CD8 T-cells. Ki-67+ CD4 T-cells, CCR2+ non-classical monocytes, and myeloid dendritic cells increased over time (p ˂ 0.05). There were no significant changes in other inflammatory markers or HIV DNA/RNA levels. These findings can guide future large clinical trials investigating cannabinoid anti-inflammatory properties.

SARS-CoV-2 Vaccine-Induced T-Cell Response after Three Doses in People Living with HIV on Antiretroviral Therapy Compared to Seronegative Controls (CTN 328 COVAXHIV Study).

People living with HIV (PLWH) may be at risk for poor immunogenicity to certain vaccines, including the ability to develop immunological memory. Here, we assessed T-cell immunogenicity following three SARS-CoV-2 vaccine doses in PLWH versus uninfected controls. Blood was collected from 38 PLWH on antiretroviral therapy and 24 age-matched HIV-negative controls, pre-vaccination and after 1st/2nd/3rd dose of SARS-CoV-2 vaccines, without prior SARS-CoV-2 infection. Flow cytometry was used to assess ex vivo T-cell immunophenotypes and intracellular Tumor necrosis factor (TNF)-α/interferon(IFN)-γ/interleukin(IL)-2 following SARS-CoV-2-Spike-peptide stimulation. Comparisons were made using Wilcoxon signed-rank test for paired variables and Mann-Whitney for unpaired. In PLWH, Spike-specific CD4 T-cell frequencies plateaued post-2nd dose, with no significant differences in polyfunctional SARS-CoV-2-specific T-cell proportions between PLWH and uninfected controls post-3rd dose. PLWH had higher frequencies of TNFα+CD4 T-cells and lower frequencies of IFNγ+CD8 T-cells than seronegative participants post-3rd dose. Regardless of HIV status, an increase in naive, regulatory, and PD1+ T-cell frequencies was observed post-3rd dose. In summary, two doses of SARS-CoV-2 vaccine induced a robust T-cell immune response in PLWH, which was maintained after the 3rd dose, with no significant differences in polyfunctional SARS-CoV-2-specific T-cell proportions between PLWH and uninfected controls post-3rd dose.

COVID-19 vaccine immunogenicity in people with HIV.

OBJECTIVES: Many vaccines require higher/additional doses or adjuvants to provide adequate protection for people with HIV (PWH). Our objective was to compare COVID-19 vaccine immunogenicity in PWH to HIV-negative individuals. DESIGN: In a Canadian multi-center prospective, observational cohort of PWH receiving at least two COVID-19 vaccinations, we measured vaccine-induced immunity at 3 and 6 months post 2nd and 1-month post 3rd doses. METHODS: The primary outcome was the percentage of PWH mounting vaccine-induced immunity [co-positivity for anti-IgG against SARS-CoV2 Spike(S) and receptor-binding domain proteins] 6 months post 2nd dose. Univariable and multivariable logistic regressions were used to compare COVID-19-specific immune responses between groups and within subgroups. RESULTS: Data from 294 PWH and 267 controls were analyzed. Immunogenicity was achieved in over 90% at each time point in both groups. The proportions of participants achieving comparable anti-receptor-binding domain levels were similar between the group at each time point. Anti-S IgG levels were similar by group at month 3 post 2nd dose and 1-month post 3rd dose. A lower proportion of PWH vs. controls maintained vaccine-induced anti-S IgG immunity 6 months post 2nd dose [92% vs. 99%; odds ratio: 0.14 (95% confidence interval: 0.03, 0.80; P = 0.027)]. In multivariable analyses, neither age, immune non-response, multimorbidity, sex, vaccine type, or timing between doses were associated with reduced IgG response. CONCLUSION: Vaccine-induced IgG was elicited in the vast majority of PWH and was overall similar between groups. A slightly lower proportion of PWH vs. controls maintained vaccine-induced anti-S IgG immunity 6 months post 2nd dose demonstrating the importance of timely boosting in this population.

Safety and Tolerability of Oral Cannabinoids in People Living with HIV on Long-Term ART: A Randomized, Open-Label, Interventional Pilot Clinical Trial (CTNPT 028).

BACKGROUND: With anti-inflammatory properties, cannabinoids may be a potential strategy to reduce immune activation in people living with HIV (PLWH) but more information on their safety and tolerability is needed. METHODS: We conducted an open-label interventional pilot study at the McGill University Health Centre in Montreal, Canada. PLWH were randomized to oral Δ9-tetrahydrocannabinol (THC): cannabidiol (CBD) combination (THC 2.5 mg/CBD 2.5 mg) or CBD-only capsules (CBD 200 mg). Individuals titrated doses as tolerated to a maximum daily dose THC 15 mg/CBD 15 mg or 800 mg CBD, respectively, for 12 weeks. The primary outcome was the percentage of participants without any significant toxicity based on the WHO toxicity scale (Grades 0-2 scores). RESULTS: Out of ten individuals, eight completed the study. Two from the CBD-only arm were withdrawn for safety concerns: phlebotomy aggravating pre-existing anemia and severe hepatitis on 800 mg CBD with newly discovered pancreatic adenocarcinoma, respectively. Seven did not have any significant toxicity. Cannabinoids did not alter hematology/biochemistry profiles. CD4 count, CD4/CD8 ratio, and HIV suppression remained stable. Most adverse effects were mild-moderate. CONCLUSIONS: In PLWH, cannabinoids seem generally safe and well-tolerated, though larger studies are needed. Screening for occult liver pathology should be performed and hepatic enzymes monitored, especially with high CBD doses.

Interplay between the Lung Microbiome, Pulmonary Immunity and Viral Reservoirs in People Living with HIV under Antiretroviral Therapy.

Pulmonary dysbiosis may predispose people living with HIV (PLWH) to chronic lung disease. Herein, we assessed whether intrapulmonary HIV reservoir size and immune disruption are associated with reduced bacterial lung diversity in PLWH. Bacterial DNA was extracted and PCR-amplified from cell-free bronchoalveolar lavage (BAL) fluid from 28 PLWH and 9 HIV-negative controls. Amplicon sequence variant (ASV) relative abundances and taxonomic identities were analyzed using joint species distribution modeling. HIV-DNA was quantified from blood and pulmonary CD4+ T-cells using ultra-sensitive qPCR. Immunophenotyping of BAL T-cells was performed using flow cytometry. Lung microbiome diversity was lower in smokers than non-smokers and microbiome composition was more variable in PLWH than HIV-negative individuals. Frequencies of effector memory BAL CD4+ and CD8+ T-cells positively correlated with abundance of several bacterial families while frequencies of BAL activated CD4+ T-cells negatively correlated with abundance of most lung bacterial families. Higher HIV-DNA levels in blood, but not in BAL, as well as frequencies of senescent CD4+ T-cells were associated with reduced bacterial diversity. These findings suggest that HIV infection may weaken the relationship between the lung microbiome and smoking status. Viral reservoir and immune activation levels may impact the lung microbiome, predisposing PLWH to pulmonary comorbidities.

The Janus-like role of neuraminidase isoenzymes in inflammation.

The processes of activation, extravasation, and migration of immune cells to a site are early and essential steps in the induction of an acute inflammatory response. These events are an essential part of the inflammatory cascade, which involves multiple regulatory steps. Using a murine air pouch model of inflammation with LPS as an inflammation inducer, we demonstrate that isoenzymes of the neuraminidase family (NEU1, 3, and 4) play essential roles in these processes by acting as positive or negative regulators of leukocyte infiltration. In genetically knocked-out (KO) mice for different NEU genes (Neu1 KO, Neu3 KO, Neu4 KO, and Neu3/4 double KO mice) with LPS-induced air pouch inflammation, leukocytes at the site of inflammation were counted, and the inflamed tissue was analyzed using immunohistochemistry. Our data show that leukocyte recruitment was decreased in NEU1- and NEU3-deficient mice, while it was increased in NEU4-deficient animals. Consistent with these results, systemic as well as pouch exudate levels of pro-inflammatory cytokines were reduced in Neu1 and increased in Neu4 KO mice. Pharmacological inhibitors specific for NEU1, NEU3, and NEU4 isoforms also affected leukocyte recruitment. Together our data demonstrate that NEU isoenzymes have distinct-and even opposing-effects on leukocyte recruitment, and therefore warrant further investigation to determine their mechanisms and importance as regulators of the inflammatory cascade.

CpG Methylation in TGFß1 and IL-6 Genes as Surrogate Biomarkers for Diagnosis of IBD in Children.

BACKGROUND: Diagnostic markers for distinguishing between Crohn disease (CD) and ulcerative colitis (UC) remain elusive. We studied whether methylation marks across the promoters of the transforming growth factor beta 1 (TGFß1) and interleukin-6 genes have diagnostic utility. METHODS: A case-control study was carried out. Cases were treatment-naïve, diagnosed before age 20, and recruited from 3 pediatric gastroenterology clinics across Canada. Control patients did not have inflammatory bowel disease and were recruited from orthopedic clinics within the same hospitals as the gastroenterology clinics. Patient DNA from peripheral blood was processed to identify methylation sites (CpG) across the promoter regions of the TGFß1 and interleukin-6 genes. After initial nonparametric univariate analyses, multivariate logistic regression models were fit. Models with the best fit (Akaike information criteria) and strongest discriminatory capabilities (area under the curve [AUC]) were identified, and P values were adjusted for multiple comparisons using the false discovery rate method. RESULTS: A total of 67 CD, 31 UC, and 43 control patients were included. The age distribution of the 3 groups was similar. Most CD patients had ileocolonic disease (44.8%) and inflammatory disease (88.1%). Most UC patients had extensive (71%) and moderate disease (51.6%). Logistic regression analysis revealed the following: 14 TGFß1 CpG sites discriminated between CD and control patients (AUC = 0.94), 9 TGFß1 CpG sites discriminated between UC and control patients (AUC = 0.99), 3 TGFß1 CpG sites discriminated between CD and UC (AUC = 0.81), and 6 TGFß1 CpG sites distinguished colonic CD from UC (AUC = 0.91). CONCLUSIONS: We found that CpG methylation in the promoter of the TGFß1 gene has high discriminative power for identifying CD and UC and could serve as an important diagnostic marker.

Phenotypic and Functional Changes in Peripheral Blood Natural Killer Cells in Crohn Disease Patients.

We investigated activation status, cytotoxic potential, and gut homing ability of the peripheral blood Natural Killer (NK) cells in Crohn disease (CD) patients. For this purpose, we compared the expression of different activating and inhibitory receptors (KIR and non-KIR) and integrins on NK cells as well as their recent degranulation history between the patients and age-matched healthy controls. The study was conducted using freshly obtained peripheral blood samples from the study participants. Multiple color flow cytometry was used for these determinations. Our results show that NK cells from treatment-naïve CD patients expressed higher levels of activating KIR as well as other non-KIR activating receptors vis-à-vis healthy controls. They also showed increased frequencies of the cells expressing these receptors. The expression of several KIR and non-KIR inhibitory receptors tended to decrease compared with the cells from healthy donors. NK cells from the patients also expressed increased levels of different gut-homing integrin molecules and showed a history of increased recent degranulation events both constitutively and in response to their in vitro stimulation. Furthermore, treatment of the patients tended to reverse these NK cell changes. Our results demonstrate unequivocally, for the first time, that peripheral blood NK cells in treatment-naïve CD patients are more activated and are more poised to migrate to the gut compared to their counterpart cells from healthy individuals. Moreover, they show that treatment of the patients tends to normalize their NK cells. The results suggest that NK cells are very likely to play a role in the immunopathogenesis of Crohn disease.

Activating Killer-cell Immunoglobulin-like Receptor genes confer risk for Crohn's disease in children and adults of the Western European descent: Findings based on case-control studies.

BACKGROUND: Killer-cell Immunoglobulin-like Receptor (KIR) genes encode receptors, which are mainly expressed on, and control functional activities of, Natural Killer (NK) cells. There exist six distinct activating KIR genes in humans, who differ from one another with respect to the repertoire of these genes. Because activated NK cells can potentially cause tissue destruction, we hypothesized that variation in the inherited activating KIR genes in humans is associated with their innate susceptibility/resistance to developing Crohn disease (CD). METHODS: We performed case control studies on three independent Canadian CD patient cohorts (all of the Western European descent): two comprising children (Montreal having 193 cases and 245 controls, and Ottawa having 93 cases and 120 controls) and the third one comprising predominantly adults (Winnipeg having 164 cases and 200 controls). We genotyped cases and controls for activating KIR genes by PCR with gene-specific primers and investigated associations between the genes and cases using unconditional logistic regression. RESULTS: We observed strong associations between all the six KIR genes and CD in Ottawa children, with the strongest risk observed for the KIR2DS1 (p = 1.7 x10-10). Associations between all but the KIR2DS2 were replicated in the Montreal cohort with the strongest association evident for the KIR2DS5 (8.0 x 10-10). Similarly associations between five genes were observed in the adult Winnipeg cohort. In this cohort, strongest associations were evident with the KIR2DS5 (8.75 x 10-8). An overall analysis for all cohorts showed strong associations with four of the genes, with the strongest association evident for the KIR2DS5 (p = 1.35 x 10-17). In the combined analysis for four KIR genes, individuals carrying one or more of the KIR genes were at significantly higher risks for acquiring CD (p = 3.5 x 10-34). CONCLUSIONS: Activating KIR genes are associated with risk for developing CD in both children and adults.

The anti-inflammatory IL-37/SIGIRR axis is functionally compromised in HIV infection.

BACKGROUND: IL-37 is a member of the IL-1 family with potent anti-inflammatory effects. Little is known about regulation of the cytokine and of its signaling co-receptor SIGIRR in HIV infection. OBJECTIVES: Our main objective was to investigate how production of the cytokine and expression of SIGIRR on immune cells is regulated in HIV infection. METHODS: The study was conducted using biological samples from a cross section of HIV-infected individuals. Concentrations of IL-37, TNF-α and soluble form of SIGIRR in serum samples were determined by ELISA. The expression of SIGIRR on immune cells was determined by flow cytometry. IL-37 isoform-specific transcripts were determined in PBMC by RT-PCR using isoform-specific primers. The effects of exogenous IL-37 on HIV replication in human phytohaemagglutinin (PHA) blasts were determined in in-vitro assays. RESULTS: The cytokine concentrations tended to decrease in treatment-naive HIV-infected individuals. They were higher in treated HIV-infected individuals compared with those from treatment-naive ones. Higher concentrations of the cytokine were observed in sera from LTNP. The expression of SIGIRR on immune cells was decreased in HIV-infected individuals. On the other hand, its soluble form increased in the sera in these individuals. The trend was reversed in the patients undergoing antiretroviral treatment. Soluble SIGIRR attenuated anti-inflammatory effects of the cytokine. Serum IL-37 and soluble SIGIRR concentrations correlated with certain clinical parameters of the patients. Furthermore, recombinant human IL-37 inhibited HIV replication in human PHA blasts. CONCLUSION: The IL-37/SIGIRR axis is functionally compromised in HIV-infected individuals. Targeting the axis may alleviate inflammation and decrease HIV replication in this viral infection.

HIV induces production of IL-18 from intestinal epithelial cells that increases intestinal permeability and microbial translocation.

Interleukin-18 (IL-18) is a pleiotropic cytokine of the IL-1 family with multiple context dependent functions. We and others have shown that HIV infection is accompanied by increased circulating levels of IL-18 along with decreased levels of its antagonist, Interleukin-18 Binding Protein (IL-18BP). The infection is also accompanied by intestinal inflammation and decreased intestinal integrity as measured by intestinal permeability, regeneration and repair. However, little is known concerning the relation between high level of IL-18 associated with the viral infection and intestinal permeability. Here we demonstrate that HIV treatment increases production of IL-18 and decreases that of IL-18BP production in human intestinal epithelial cell (IEC) lines. IL-18 causes apoptosis of the IEC by activating caspase-1 and caspase-3. It induces epithelial barrier hyperpermeability by decreasing and disrupting both tight and adherens junction proteins, occludin, claudin 2 and beta-catenin. Disorganization of F-actin was also observed in the IEC that were exposed to the cytokine. Moreover IL-18 decreases transepithelial electrical resistance (TEER) in Caco-2 and increases permeability in HT29 monolayers. The cells' treatment with IL-18 causes an increase in the expression of phosphorylated myosin II regulatory light-chain (p-MLC) and myosin light-chain kinase (MLCK), and a decrease in phosphorylated Signal Transducer and Activator of Transcription (p-STAT)-5. This increase in p-MLC is suppressed by a Rho-kinase (ROCK)-specific inhibitor. Interestingly, the levels of the cytokine correlate with those of LPS in the circulation in three different categories of HIV infected patients (HAART-naïve and HAART-treated HIV-infected individuals, and Elite controls) as well as in healthy controls. Collectively, these results suggest that the HIV-induced IL-18 plays a role in increased intestinal permeability and microbial translocation observed in HIV-infected individuals.

Differential synthesis and release of IL-18 and IL-18 Binding Protein from human platelets and their implications for HIV infection.

IL-18 is a pro-inflammatory cytokine belonging to the IL-1 family and is produced in the body from macrophages, epithelial and dendritic cells, keratinocytes, adrenal cortex etc. The cytokine is produced as an inactive precursor that is cleaved inside cells into its mature form by activated caspase 1, which exists as an inactive precursor in human cells and requires assembly of an inflammasomes for its activation. We show here for the first time that human platelets contain transcripts for the IL-18 gene. They synthesize the cytokine de novo, process and release it upon activation. The activation also results in the assembly of an inflammasome and activation of caspase-1. Platelets also contain the IL-18 antagonist, the IL-18-Binding Protein (IL-18BP); however, it is not synthesized in them de novo, is present in pre-made form and is released irrespective of platelet activation. IL-18 and IL-18BP co-localize to α granules inside platelets and are secreted out with different kinetics. Platelet activation contributes to plasma concentrations in healthy individuals, as their plasma samples contain abundant IL-18, while their platelet-poor plasma samples contain very little amounts of the cytokine. The plasma and PPP samples from these donors, however, contain comparable amounts of IL-18BP. Unlike healthy individuals, the platelet-poor plasma from HIV-infected individuals contains significant amounts of IL-18. Our findings have important implications for viral infections and other human diseases that are accompanied by platelet activation.

A protective role of IL-37 in cancer: a new hope for cancer patients.

IL-37 is a cytokine belonging to the IL-1 family. Although discovered in silico in 2000, significant advances in the understanding of its biology were made only in recent years. It is a member of the family with potent anti-inflammatory and immunosuppressive properties. It is produced as a precursor without a classic signal peptide. The precursor is cleaved into mature form in the cytoplasm by caspase-1. A small fraction of the cleaved IL-37 binds SMAD-3, translocates to the nucleus, and suppresses transcription of several proinflammatory genes. Both precursor and cleaved forms of IL-37 are secreted. They bind IL-18Rα chain (also used by IL-18 as a receptor subunit) and recruit Toll/IL-1R (TIR)-8 for transducing intracellular signaling. TIR-8 is a member of the IL-1 receptor family (IL-1RF) and was previously known as an orphan receptor. IL-37 suppresses activation of NF-κB and MAPK and activates Mer-PTEN-DOK pathway. It negatively regulates signaling mediated by TLR agonists, proinflammatory cytokines, and IL-1RF ligands. It also affects cell metabolism by inhibiting mTOR, GSK-3α/ß, and activating AMPK. Despite having the ability to dampen host's immune responses, the cytokine has been shown to exert antitumor effects, and it has been suggested that it may act as a prognostic marker in a variety of human cancers. Recent studies have suggested that IL-37 may represent a novel therapeutic tool in patients with cancer. In this review, we provide an overview of the cytokine biology, discuss recent advances made in unraveling its anti-cancer effects, and suggest guidelines for future research.

A potentially protective role of IL-18 Binding Protein in HIV-infected Long-Term Non-Progressors.

An imbalance between IL-18 and its antagonist, IL-18 Binding Protein, occurs in the circulation of HIV-infected individuals. We show here for the first time that HIV-infected Long Term Non-Progressors (LTNPs) do not develop this imbalance, and maintain normal levels of IL-18BP in the circulation. Their circulating levels of the antagonist correlate negatively with viral loads and show a positive trend with CD4+ T cells counts. The maintenance of normal production of IL-18BP may contribute, at least in part, to the ability of LTNPs to delay AIDS progression.

Lymphocytic Microparticles Modulate Angiogenic Properties of Macrophages in Laser-induced Choroidal Neovascularization.

Pathological choroidal neovascularization (CNV) is the common cause of vision loss in patients with age-related macular degeneration (AMD). Macrophages possess potential angiogenic function in CNV. We have demonstrated that human T lymphocyte-derived microparticles (LMPs) exert a potent antiangiogenic effect in several pathological neovascularization models. In this study, we investigated the alteration of proangiogenic properties of macrophages by LMPs treatment in vitro and in vivo models. LMPs regulated the expression of several angiogenesis-related factors in macrophages and consequently stimulated their antiangiogenic effects evidenced by the suppression of the proliferation of human retinal endothelial cells in co-culture experiments. The involvement of CD36 receptor in LMPs uptake by macrophages was demonstrated by in vitro assays and by immunostaining of choroidal flat mounts. In addition, ex vivo experiments showed that CD36 mediates the antiangiogenic effect of LMPs in murine and human choroidal explants. Furthermore, intravitreal injection of LMPs in the mouse model of laser-induced CNV significantly suppressed CNV in CD36 dependent manner. The results of this study suggested an ability of LMPs to alter the gene expression pattern of angiogenesis-related factors in macrophages, which provide important information for a new therapeutic approach for efficiently interfering with both vascular and extravascular components of CNV.