Adaptive NK Cells Rapidly Expand during Acute HIV Infection and Persist Despite Early Initiation of Antiretroviral Therapy.

HIV is associated with NK cell dysfunction and expansion of adaptive-like NK cells that persist despite antiretroviral therapy (ART). We investigated the timing of NK cell perturbations during acute HIV infection and the impact of early ART initiation. PBMCs and plasma were obtained from people with HIV (PWH; all men who have sex with men; median age, 26.0 y) diagnosed during Fiebig stages I, II, III, or IV/V. Participants initiated ART a median of 3 d after diagnosis, and immunophenotyping was performed at diagnosis and longitudinally after ART. Anti-CMV Abs were assessed by ELISA. Samples from matched HIV-uninfected males were also analyzed. Proportions of adaptive NK cells (A-NKs; defined as Fcε-Receptor-1γ-) were expanded at HIV diagnosis at all Fiebig stages (pooled median 66% versus 25% for controls; p < 0.001) and were not altered by early ART initiation. Abs to CMV immediate early protein were elevated in PWH diagnosed in Fiebig stages III and IV/V (p < 0.03 for both). Proportions of A-NKs defined as either Fcε-Receptor-1γ- or NKG2C+/CD57+ were significantly associated with HIV DNA levels at diagnosis (p = 0.046 and 0.029, respectively) and trended toward an association after 48 wk of ART. Proportions of activated HLA-DR+/CD38+ NK cells remained elevated in PWH despite early ART initiation. NK cell activation and A-NK expansion occur very early after HIV transmission, before T cell activation, and are not altered by ART initiation during acute infection. A-NKs may contribute to HIV control and thus be useful for HIV cure.

Regional Analysis of Intact and Defective HIV Proviruses in the Brain of Viremic and Virally Suppressed People with HIV.

Here, we provide the first regional analysis of intact and defective HIV reservoirs within the brain. Brain tissue from both viremic and virally suppressed people with HIV (PWH) harbored HIV pol DNA in all regions tested, with lower levels present in basal ganglia and cerebellum relative to frontal white matter. Intact proviruses were primarily found in the frontal white matter but also detected in other brain regions of PWH, demonstrating frontal white matter as a major brain reservoir of intact, potentially replication competent HIV DNA that persists despite antiretroviral therapy. ANN NEUROL 2023;94:798-802.

Intact HIV Proviruses Persist in the Brain Despite Viral Suppression with ART.

OBJECTIVE: Human immunodeficiency virus (HIV) persistence in blood and tissue reservoirs, including the brain, is a major barrier to HIV cure and possible cause of comorbid disease. However, the size and replication competent nature of the central nervous system (CNS) reservoir is unclear. Here, we used the intact proviral DNA assay (IPDA) to provide the first quantitative assessment of the intact and defective HIV reservoir in the brain of people with HIV (PWH). METHODS: Total, intact, and defective HIV proviruses were measured in autopsy frontal lobe tissue from viremic (n = 18) or virologically suppressed (n = 12) PWH. Total or intact/defective proviruses were measured by detection of HIV pol or the IPDA, respectively, through use of droplet digital polymerase chain reaction (ddPCR). HIV-seronegative individuals were included as controls (n = 6). RESULTS: Total HIV DNA was present at similar levels in brain tissues from untreated viremic and antiretroviral (ART)-suppressed individuals (median = 22.3 vs 26.2 HIV pol copies/106 cells), reflecting a stable CNS reservoir of HIV that persists despite therapy. Furthermore, 8 of 10 viremic and 6 of 9 virally suppressed PWH also harbored intact proviruses in the CNS (4.63 vs 12.7 intact copies/106 cells). Viral reservoirs in CNS and matched lymphoid tissue were similar in the composition of intact and/or defective proviruses, albeit at lower levels in the brain. Importantly, CNS resident CD68+ myeloid cells in virally suppressed individuals harbored HIV DNA, directly showing the presence of a CNS resident HIV reservoir. INTERPRETATION: Our results demonstrate the first evidence for an intact, potentially replication competent HIV reservoir in the CNS of virally suppressed PWH. ANN NEUROL 2022;92:532-544.

Effect of Y2O3 Addition on Microstructure and Properties of Laser Cladded Al-Si Coatings on AZ91D Magnesium Alloy.

The effect of Y2O3 addition on the microstructure and properties of the laser cladded Al-Si alloy coating on the surface of AZ91D magnesium alloy was investigated in this study. The experimental results showed that the Al-Si + Y2O3 cladding layers contained α-Mg, Mg2Si, Al4MgY and a small amount of Al12Mg17 phases. The coarse dendrites, reticulated eutectic structures and massive phases in the coatings tended to be refined and gradually uniformly distributed with the increased amount of Y2O3. The introduction of Y2O3 into the cladding layer favored the improvement of microhardness and wear resistance due to the grain refinement strengthening and dispersion strengthening. The addition of Y2O3 also promoted the reduction of localized corrosion sites and made the corrosion surface smoother, implying that the corrosion resistance of the Y2O3-modified coatings was better than that of the unmodified cladding layer.

Longitudinal analysis of subtype C envelope tropism for memory CD4+ T cell subsets over the first 3 years of untreated HIV-1 infection.

BACKGROUND: HIV-1 infects a wide range of CD4+ T cells with different phenotypic properties and differing expression levels of entry coreceptors. We sought to determine the viral tropism of subtype C (C-HIV) Envelope (Env) clones for different CD4+ T cell subsets and whether tropism changes during acute to chronic disease progression. HIV-1 envs were amplified from the plasma of five C-HIV infected women from three untreated time points; less than 2 months, 1-year and 3-years post-infection. Pseudoviruses were generated from Env clones, phenotyped for coreceptor usage and CD4+ T cell subset tropism was measured by flow cytometry. RESULTS: A total of 50 C-HIV envs were cloned and screened for functionality in pseudovirus infection assays. Phylogenetic and variable region characteristic analysis demonstrated evolution in envs between time points. We found 45 pseudoviruses were functional and all used CCR5 to mediate entry into NP2/CD4/CCR5 cells. In vitro infection assays showed transitional memory (TM) and effector memory (EM) CD4+ T cells were more frequently infected (median: 46% and 25% of total infected CD4+ T cells respectively) than naïve, stem cell memory, central memory and terminally differentiated cells. This was not due to these subsets contributing a higher proportion of the CD4+ T cell pool, rather these subsets were more susceptible to infection (median: 5.38% EM and 2.15% TM cells infected), consistent with heightened CCR5 expression on EM and TM cells. No inter- or intra-participant changes in CD4+ T cell subset tropism were observed across the three-time points. CONCLUSIONS: CD4+ T cell subsets that express more CCR5 were more susceptible to infection with C-HIV Envs, suggesting that these may be the major cellular targets during the first 3 years of infection. Moreover, we found that viral tropism for different CD4+ T cell subsets in vitro did not change between Envs cloned from acute to chronic disease stages. Finally, central memory, naïve and stem cell memory CD4+ T cell subsets were susceptible to infection, albeit inefficiently by Envs from all time-points, suggesting that direct infection of these cells may help establish the latent reservoir early in infection.

Metabolically active CD4+ T cells expressing Glut1 and OX40 preferentially harbor HIV during in vitro infection.

High glucose transporter 1 (Glut1) surface expression is associated with increased glycolytic activity in activated CD4+ T cells. Phosphatidylinositide 3-kinases (PI3K) activation measured by p-Akt and OX40 is elevated in CD4+Glut1+ T cells from HIV+ subjects. TCR engagement of CD4+Glut1+ T cells from HIV+ subjects demonstrates hyperresponsive PI3K-mammalian target of rapamycin signaling. High basal Glut1 and OX40 on CD4+ T cells from combination antiretroviral therapy (cART)-treated HIV+ patients represent a sufficiently metabolically active state permissive for HIV infection in vitro without external stimuli. The majority of CD4+OX40+ T cells express Glut1, thus OX40 rather than Glut1 itself may facilitate HIV infection. Furthermore, infection of CD4+ T cells is limited by p110γ PI3K inhibition. Modulating glucose metabolism may limit cellular activation and prevent residual HIV replication in 'virologically suppressed' cART-treated HIV+ persons.

Analysis of Clinical HIV-1 Strains with Resistance to Maraviroc Reveals Strain-Specific Resistance Mutations, Variable Degrees of Resistance, and Minimal Cross-Resistance to Other CCR5 Antagonists.

Maraviroc (MVC) is an allosteric inhibitor of human immunodeficiency virus type 1 (HIV-1) entry, and is the only CCR5 antagonist licensed for use as an anti-HIV-1 therapeutic. It acts by altering the conformation of the CCR5 extracellular loops, rendering CCR5 unrecognizable by the HIV-1 envelope (Env) glycoproteins. This study aimed to understand the mechanisms underlying the development of MVC resistance in HIV-1-infected patients. To do this, we obtained longitudinal plasma samples from eight subjects who experienced treatment failure with phenotypically verified, CCR5-tropic MVC resistance. We then cloned and characterized HIV-1 Envs (n = 77) from plasma of pretreatment (n = 36) and treatment failure (n = 41) samples. Our results showed variation in the magnitude of MVC resistance as measured by reductions in maximal percent inhibition of Env-pseudotyped viruses, which was more pronounced in 293-Affinofile cells compared to other cells with similar levels of CCR5 expression. Amino acid determinants of MVC resistance localized to the V3 Env region and were strain specific. We also observed minimal cross-resistance to other CCR5 antagonists by MVC-resistant strains. We conclude that 293-Affinofile cells are highly sensitive for detecting and measuring MVC resistance through a mechanism that is CCR5-dependent yet independent of CCR5 expression levels. The strain-specific nature of resistance mutations suggests that sequence-based diagnostics and prognostics will need to be more sophisticated than simple position scoring to be useful for managing resistance in subjects taking MVC. Finally, the minimal levels of cross-resistance suggests that recognition of the MVC-modified form of CCR5 does not necessarily lead to recognition of other antagonist-modified forms of CCR5.

Persistence of Activated and Adaptive-Like NK Cells in HIV+ Individuals despite 2 Years of Suppressive Combination Antiretroviral Therapy.

Innate immune dysfunction persists in HIV+ individuals despite effective combination antiretroviral therapy (cART). We recently demonstrated that an adaptive-like CD56dim NK cell population lacking the signal transducing protein FcRγ is expanded in HIV+ individuals. Here, we analyzed a cohort of HIV+ men who have sex with men (MSM, n = 20) at baseline and following 6, 12, and 24 months of cART and compared them with uninfected MSM (n = 15) to investigate the impact of cART on NK cell dysfunction. Proportions of NK cells expressing markers of early (CD69+) and late (HLA-DR+/CD38+) activation were elevated in cART-naïve HIV+ MSM (p = 0.004 and 0.015, respectively), as were FcRγ- NK cells (p = 0.003). Using latent growth curve modeling, we show that cART did not reduce levels of FcRγ- NK cells (p = 0.115) or activated HLA-DR+/CD38+ NK cells (p = 0.129) but did reduce T cell and monocyte activation (p < 0.001 for all). Proportions of FcRγ- NK cells were not associated with NK cell, T cell, or monocyte activation, suggesting different factors drive CD56dim FcRγ- NK cell expansion and immune activation in HIV+ individuals. While proportions of activated CD69+ NK cells declined significantly on cART (p = 0.003), the rate was significantly slower than the decline of T cell and monocyte activation, indicating a reduced potency of cART against NK cell activation. Our findings indicate that 2 years of suppressive cART have no impact on CD56dim FcRγ- NK cell expansion and that NK cell activation persists after normalization of other immune parameters. This may have implications for the development of malignancies and co-morbidities in HIV+ individuals on cART.

HIV integration and the establishment of latency in CCL19-treated resting CD4(+) T cells require activation of NF-κB.

BACKGROUND: Eradication of HIV cannot be achieved with combination antiretroviral therapy (cART) because of the persistence of long-lived latently infected resting memory CD4(+) T cells. We previously reported that HIV latency could be established in resting CD4(+) T cells in the presence of the chemokine CCL19. To define how CCL19 facilitated the establishment of latent HIV infection, the role of chemokine receptor signalling was explored. RESULTS: In resting CD4(+) T cells, CCL19 induced phosphorylation of RAC-alpha serine/threonine-protein kinase (Akt), nuclear factor kappa B (NF-κB), extracellular-signal-regulated kinase (ERK) and p38. Inhibition of the phosphoinositol-3-kinase (PI3K) and Ras/Raf/Mitogen-activated protein kinase/ERK kinase (MEK)/ERK signalling pathways inhibited HIV integration, without significant reduction in HIV nuclear entry (measured by Alu-LTR and 2-LTR circle qPCR respectively). Inhibiting activation of MEK1/ERK1/2, c-Jun N-terminal kinase (JNK), activating protein-1 (AP-1) and NF-κB, but not p38, also inhibited HIV integration. We also show that HIV integrases interact with Pin1 in CCL19-treated CD4(+) T cells and inhibition of JNK markedly reduced this interaction, suggesting that CCL19 treatment provided sufficient signals to protect HIV integrase from degradation via the proteasome pathway. Infection of CCL19-treated resting CD4(+) T cells with mutant strains of HIV, lacking NF-κB binding sites in the HIV long terminal repeat (LTR) compared to infection with wild type virus, led to a significant reduction in integration by up to 40-fold (range 1-115.4, p = 0.03). This was in contrast to only a modest reduction of 5-fold (range 1.7-11, p > 0.05) in fully activated CD4(+) T cells infected with the same mutants. Finally, we demonstrated significant differences in integration sites following HIV infection of unactivated, CCL19-treated, and fully activated CD4(+) T cells. CONCLUSIONS: HIV integration in CCL19-treated resting CD4(+) T cells depends on NF-κB signalling and increases the stability of HIV integrase, which allow subsequent integration and establishment of latency. These findings have implications for strategies needed to prevent the establishment, and potentially reverse, latent infection.

Ex vivo foam cell formation is enhanced in monocytes from older individuals by both extrinsic and intrinsic mechanisms.

Aging is the strongest predictor of cardiovascular diseases such as atherosclerosis, which are the leading causes of morbidity and mortality in elderly men. Monocytes play an important role in atherosclerosis by differentiating into foam cells (lipid-laden macrophages) and producing atherogenic proinflammatory cytokines. Monocytes from the elderly have an inflammatory phenotype that may promote atherosclerotic plaque development; here we examined whether they are more atherogenic than those from younger individuals. Using an in vitro model of monocyte transmigration and foam cell formation, monocytes from older men (median age [range]: 75 [58-85] years, n=20) formed foam cells more readily than those of younger men (32 [23-46] years, n=20) (P<0.003) following transmigration across a TNF-activated endothelial monolayer. Compared to young men, monocytes from the elderly had impaired cholesterol efflux and lower expression of regulators of cholesterol transport and metabolism. Foam cell formation was enhanced by soluble factors in serum from older men, but did not correlate with plasma lipid levels. Of the three subsets, intermediate monocytes formed the most foam cells. Therefore, both cellular changes to monocytes and soluble plasma factors in older men primes monocytes for foam cell formation following transendothelial migration, which may contribute to enhanced atherosclerosis in this population.

Monocytes from HIV-infected individuals show impaired cholesterol efflux and increased foam cell formation after transendothelial migration.

DESIGN: HIV-infected (HIV+) individuals have an increased risk of atherosclerosis and cardiovascular disease which is independent of antiretroviral therapy and traditional risk factors. Monocytes play a central role in the development of atherosclerosis, and HIV-related chronic inflammation and monocyte activation may contribute to increased atherosclerosis, but the mechanisms are unknown. METHODS: Using an in-vitro model of atherosclerotic plaque formation, we measured the transendothelial migration of purified monocytes from age-matched HIV+ and uninfected donors and examined their differentiation into foam cells. Cholesterol efflux and the expression of cholesterol metabolism genes were also assessed. RESULTS: Monocytes from HIV+ individuals showed increased foam cell formation compared with controls (18.9 vs. 0%, respectively, P = 0.004) and serum from virologically suppressed HIV+ individuals potentiated foam cell formation by monocytes from both uninfected and HIV+ donors. Plasma tumour necrosis factor (TNF) levels were increased in HIV+ vs. control donors (5.9 vs. 3.5 pg/ml, P = 0.02) and foam cell formation was inhibited by blocking antibodies to TNF receptors, suggesting a direct effect on monocyte differentiation to foam cells. Monocytes from virologically suppressed HIV+ donors showed impaired cholesterol efflux and decreased expression of key genes regulating cholesterol metabolism, including the cholesterol transporter ABCA1 (P = 0.02). CONCLUSION: Monocytes from HIV+ individuals show impaired cholesterol efflux and are primed for foam cell formation following transendothelial migration. Factors present in HIV+ serum, including elevated TNF levels, further enhance foam cell formation. The proatherogenic phenotype of monocytes persists in virologically suppressed HIV+ individuals and may contribute mechanistically to increased atherosclerosis in this population.

CD14(hi)CD16+ monocytes phagocytose antibody-opsonised Plasmodium falciparum infected erythrocytes more efficiently than other monocyte subsets, and require CD16 and complement to do so.

BACKGROUND: With more than 600,000 deaths from malaria, mainly of children under five years old and caused by infection with Plasmodium falciparum, comes an urgent need for an effective anti-malaria vaccine. Limited details on the mechanisms of protective immunity are a barrier to vaccine development. Antibodies play an important role in immunity to malaria and monocytes are key effectors in antibody-mediated protection by phagocytosing antibody-opsonised infected erythrocytes (IE). Eliciting antibodies that enhance phagocytosis of IE is therefore an important potential component of an effective vaccine, requiring robust assays to determine the ability of elicited antibodies to stimulate this in vivo. The mechanisms by which monocytes ingest IE and the nature of the monocytes which do so are unknown. METHODS: Purified trophozoite-stage P. falciparum IE were stained with ethidium bromide, opsonised with anti-erythrocyte antibodies and incubated with fresh whole blood. Phagocytosis of IE and TNF production by individual monocyte subsets was measured by flow cytometry. Ingestion of IE was confirmed by imaging flow cytometry. RESULTS: CD14(hi)CD16+ monocytes phagocytosed antibody-opsonised IE and produced TNF more efficiently than CD14(hi)CD16- and CD14(lo)CD16+ monocytes. Blocking experiments showed that Fcγ receptor IIIa (CD16) but not Fcγ receptor IIa (CD32a) or Fcγ receptor I (CD64) was necessary for phagocytosis. CD14(hi)CD16+ monocytes ingested antibody-opsonised IE when peripheral blood mononuclear cells were reconstituted with autologous serum but not heat-inactivated autologous serum. Antibody-opsonised IE were rapidly opsonised with complement component C3 in serum (t1/2 = 2-3 minutes) and phagocytosis of antibody-opsonised IE was inhibited in a dose-dependent manner by an inhibitor of C3 activation, compstatin. Compared to other monocyte subsets, CD14(hi)CD16+ monocytes expressed the highest levels of complement receptor 4 (CD11c) and activated complement receptor 3 (CD11b) subunits. CONCLUSIONS: We show a special role for CD14(hi)CD16+ monocytes in phagocytosing opsonised P. falciparum IE and production of TNF. While ingestion was mediated by Fcγ receptor IIIa, this receptor was not sufficient to allow phagocytosis; despite opsonisation with antibody, phagocytosis of IE also required complement opsonisation. Assays which measure the ability of vaccines to elicit a protective antibody response to P. falciparum should consider their ability to promote phagocytosis and fix complement.

An NK Cell Population Lacking FcRγ Is Expanded in Chronically Infected HIV Patients.

We previously demonstrated that NK cells from HIV-infected individuals have elevated expression of activation markers, spontaneously degranulate ex vivo, and decrease expression of a signal-transducing protein for NK-activating receptors, FcRγ. Importantly, these changes were maintained in virologically suppressed (VS) individuals receiving combination antiretroviral therapy (cART). In this study, we show that loss of FcRγ is caused by the expansion of a novel subset of FcRγ(-)CD56(dim) NK cells with an altered activation receptor repertoire and biological properties. In a cross-sectional study, FcRγ(-) NK cells as a proportion of total CD56(dim) NK cells increased in cART-naive viremic HIV-infected individuals (median [interquartile range] = 25.9 [12.6-56.1] compared with 3.80 [1.15-11.5] for HIV(-) controls, p < 0.0001) and in VS HIV-infected individuals (22.7 [13.1-56.2] compared with 3.80 [1.15-11.5], p = 0.0004), with no difference between cART-naive and VS patients (p = 0.93). FcRγ(-) NK cells expressed no NKp30 or NKp46. They showed greater Ab-dependent cellular cytotoxicity activity against rituximab-opsonized Raji cells and in a whole-blood assay measuring NK responses to overlapping HIV peptides, despite having reduced CD16 expression compared with conventional NK cells. Their prevalence correlated with CMV Ab titers in HIV(-) subjects but not in HIV(+) individuals, and with the inflammatory marker CXCL10 in both groups. The expansion of a subset of NK cells that lacks NKp30 and NKp46 to ∼90% of CD56(dim) NK cells in some VS HIV(+) individuals may influence NK-mediated immunosurveillance in patients receiving cART.

Glucose transporter 1-expressing proinflammatory monocytes are elevated in combination antiretroviral therapy-treated and untreated HIV+ subjects.

Monocyte activation during HIV-1 infection is associated with increased plasma levels of inflammatory markers and increased risk for premature development of age-related diseases. Because activated monocytes primarily use glucose to support cellular metabolism, we hypothesized that chronic monocyte activation during HIV-1 infection induces a hypermetabolic response with increased glucose uptake. To test this hypothesis, we evaluated glucose transporter 1 (Glut1) expression and glucose uptake by monocyte subpopulations in HIV-seropositive (HIV(+)) treatment-naive individuals (n = 17), HIV(+) individuals on combination antiretroviral therapy with viral loads below detection (n = 11), and HIV-seronegative (HIV(-)) individuals (n = 16). Surface expression of Glut1 and cellular uptake of the fluorescent glucose analog 2-(N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl) amino)-2 deoxyglucose were analyzed by flow cytometry on monocyte subpopulations. Irrespective of treatment status, monocytes from HIV(+) persons had significantly increased surface expression of Glut1 compared with those from HIV(-) controls. Nonclassical (CD14(+)CD16(++)) and intermediate (CD14(++)CD16(+)) monocyte subpopulations showed higher Glut1 expression than did classical (CD14(++)CD16(-)) monocytes. Intermediate monocytes from treatment-naive HIV(+) individuals also showed increased uptake of 2-(N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl) amino)-2 deoxyglucose compared with those from HIV(-) controls. Our results show that HIV infection is associated with increased glucose metabolism in monocytes and that Glut1 expression by proinflammatory monocytes is a potential marker of inflammation in HIV-infected subjects. However, the possibility exists whereby other Gluts such as Glut3 and Glut4 may also support the influx of glucose into activated and inflammatory monocyte populations.

[Variation characteristics and removal rate of fluorescence organic matter in the petrochemical wastewater treatment process].

Petrochemical wastewater is of huge quantity released during the production and complicated contaminants of petrochemical wastewater will have immense negative impact on ecology environment. Three-dimensional excitation-emission matrix fluorescence(3D-EEM) was used to investigate the characteristic fluorescence of influent and effluent from each processing unit of Hydrolysis-acidification +A/O+ Contact-oxidation Process in a typical petrochemical wastewater treatment plant . The results showed that there were 4 fluorescence peaks named Peak A, Peak B, Peak D, Peak E in the spectrum chart of influent, they are around lambda(ex/lambda(em) = 220/300, 225/340, 270/300, 275/340 nm, the primary source of fluorescence organic matter(FOM) is industrial wastewater. The fluorescence intensity of each fluorescence peak was decreased, while location was unchanged in the effluent of Hydrolysis-acidification. Peak C appeared from the effluent of anaerobic tank at lambda(ex)/lambda(em) = 250/425 nm, then the fluorescence intensity of Peak C was enhanced in the effluent of aerobic tank. Peak A disappeared from the effluent of secondary sedimentation tank. The spectrum chart of the wastewater had no obvious variation after secondary sedimentation tank. The removal rate of FOM was expressed with the degradation percentage of the fluorescence intensity, the total FOM was reduced by 92.0% after processing, and the removal rate of the FOM fluoresce around Peak A, Peak B, Peak D, Peak E were 100.0%, 91.2%, 80.3%, 92.0% respectively. A volatile I(Peak B)/I(Peak E) value of influent but a relatively stable value of effluent demonstrated that the wastewater treatment plant operated steadily and the process has higher capacity in resistance to shock loading.

Opsonic phagocytosis of Plasmodium falciparum merozoites: mechanism in human immunity and a correlate of protection against malaria.

BACKGROUND: An understanding of the mechanisms mediating protective immunity against malaria in humans is currently lacking, but critically important to advance the development of highly efficacious vaccines. Antibodies play a key role in acquired immunity, but the functional basis for their protective effect remains unclear. Furthermore, there is a strong need for immune correlates of protection against malaria to guide vaccine development. METHODS: Using a validated assay to measure opsonic phagocytosis of Plasmodium falciparum merozoites, we investigated the potential role of this functional activity in human immunity against clinical episodes of malaria in two independent cohorts (n = 109 and n = 287) experiencing differing levels of malaria transmission and evaluated its potential as a correlate of protection. RESULTS: Antibodies promoting opsonic phagocytosis of merozoites were cytophilic immunoglobulins (IgG1 and IgG3), induced monocyte activation and production of pro-inflammatory cytokines, and were directed against major merozoite surface proteins (MSPs). Consistent with protective immunity in humans, opsonizing antibodies were acquired with increasing age and malaria exposure, were boosted on re-infection, and levels were related to malaria transmission intensity. Opsonic phagocytosis was strongly associated with a reduced risk of clinical malaria in longitudinal studies in children with current or recent infections. In contrast, antibodies to the merozoite surface in standard immunoassays, or growth-inhibitory antibodies, were not significantly associated with protection. In multivariate analyses including several antibody responses, opsonic phagocytosis remained significantly associated with protection against malaria, highlighting its potential as a correlate of immunity. Furthermore, we demonstrate that human antibodies against MSP2 and MSP3 that are strongly associated with protection in this population are effective in opsonic phagocytosis of merozoites, providing a functional link between these antigen-specific responses and protection for the first time. CONCLUSIONS: Opsonic phagocytosis of merozoites appears to be an important mechanism contributing to protective immunity in humans. The opsonic phagocytosis assay appears to be a strong correlate of protection against malaria, a valuable biomarker of immunity, and provides a much-needed new tool for assessing responses to blood-stage malaria vaccines and measuring immunity in populations.

Increased glucose metabolic activity is associated with CD4+ T-cell activation and depletion during chronic HIV infection.

OBJECTIVES: Glucose metabolism plays a fundamental role in supporting the growth, proliferation and effector functions of T cells. We investigated the impact of HIV infection on key processes that regulate glucose uptake and metabolism in primary CD4 and CD8 T cells. DESIGN AND METHODS: Thirty-eight HIV-infected treatment-naive, 35 HIV+/combination antiretroviral therapy, seven HIV+ long-term nonprogressors and 25 HIV control individuals were studied. Basal markers of glycolysis [e.g. glucose transporter-1 (Glut1) expression, glucose uptake, intracellular glucose-6-phosphate, and L-lactate] were measured in T cells. The cellular markers of immune activation, CD38 and HLA-DR, were measured by flow cytometry. RESULTS: The surface expression of the Glut1 is up-regulated in CD4 T cells in HIV-infected patients compared with uninfected controls. The percentage of circulating CD4Glut1 T cells was significantly increased in HIV-infected patients and was not restored to normal levels following combination antiretroviral therapy. Basal markers of glycolysis were significantly higher in CD4Glut1 T cells compared to CD4Glut1 T cells. The proportion of CD4Glut1 T cells correlated positively with the expression of the cellular activation marker, HLA-DR, on total CD4 T cells, but inversely with the absolute CD4 T-cell count irrespective of HIV treatment status. CONCLUSION: Our data suggest that Glut1 is a potentially novel and functional marker of CD4 T-cell activation during HIV infection. In addition, Glut1 expression on CD4 T cells may be exploited as a prognostic marker for CD4 T-cell loss during HIV disease progression.

HIV and co-infections.

Despite significant reductions in morbidity and mortality secondary to availability of effective combination anti-retroviral therapy (cART), human immunodeficiency virus (HIV) infection still accounts for 1.5 million deaths annually. The majority of deaths occur in sub-Saharan Africa where rates of opportunistic co-infections are disproportionately high. In this review, we discuss the immunopathogenesis of five common infections that cause significant morbidity in HIV-infected patients globally. These include co-infection with Mycobacterium tuberculosis, Cryptococcus neoformans, hepatitis B virus, hepatitis C virus, and Plasmodium falciparum. Specifically, we review the natural history of each co-infection in the setting of HIV, the specific immune defects induced by HIV, the effects of cART on the immune response to the co-infection, the pathogenesis of immune restoration disease (IRD) associated with each infection, and advances in the areas of prevention of each co-infection via vaccination. Finally, we discuss the opportunities and gaps in knowledge for future research.

Opsonization of malaria-infected erythrocytes activates the inflammasome and enhances inflammatory cytokine secretion by human macrophages.

BACKGROUND: Antibody opsonization of Plasmodium falciparum-infected erythrocytes (IE) plays a crucial role in anti-malarial immunity by promoting clearance of blood-stage infection by monocytes and macrophages. The effects of phagocytosis of opsonized IE on macrophage pro-inflammatory cytokine responses are poorly understood. METHODS: Phagocytic clearance, cytokine response and intracellular signalling were measured using IFN-γ-primed human monocyte-derived macrophages (MDM) incubated with opsonized and unopsonized trophozoite-stage CS2 IE, a chondroitin sulphate-binding malaria strain. Cytokine secretion was measured by bead array or ELISA, mRNA using quantitative PCR, and activation of NF-κB by Western blot and electrophoretic mobility shift assay. Data were analysed using the Mann-Whitney U test or the Wilcoxon signed rank test as appropriate. RESULTS: Unopsonized CS2 IE were not phagocytosed whereas IE opsonized with pooled patient immune serum (PPS) were (Phagocytic index (PI)=18.4, [SE 0.38] n=3). Unopsonized and opsonized IE induced expression of TNF, IL-1ß and IL-6 mRNA by MDM and activated NF-κB to a similar extent. Unopsonized IE induced secretion of IL-6 (median= 622 pg/ml [IQR=1,250-240], n=9) but no IL-1ß or TNF, whereas PPS-opsonized IE induced secretion of IL-1ß (18.6 pg/mL [34.2-14.4]) and TNF (113 pg/ml [421-17.0]) and increased IL-6 secretion (2,195 pg/ml [4,658-1,095]). Opsonized, but not unopsonized, CS2 IE activated caspase-1 cleavage and enzymatic activity in MDM showing that Fc receptor-mediated phagocytosis activates the inflammasome. MDM attached to IgG-coated surfaces however secreted IL-1ß in response to unopsonized IE, suggesting that internalization of IE is not absolutely required to activate the inflammasome and stimulate IL-1ß secretion. CONCLUSIONS: It is concluded that IL-6 secretion from MDM in response to CS2 IE does not require phagocytosis, whereas secretion of TNF and IL-1ß is dependent on Fcγ receptor-mediated phagocytosis; for IL-1ß, this occurs by activation of the inflammasome. The data presented in this paper show that generating antibody responses to blood-stage malaria parasites is potentially beneficial both in reducing parasitaemia via Fcγ receptor-dependent macrophage phagocytosis and in generating a robust pro-inflammatory response.