Lysis of human immunodeficiency virus type 1 by a specific secreted human phospholipase A2

Molecular Cloning and Functional Analysis of Secretory Phospholipase A2 from Apostichopus japonicus

Secretory phospholipase A2 (sPLA2) plays important roles in phospholipid metabolism, skin barrier maintenance, immune response and other processes in organisms. sPLA2 of sea cucumber A. japonicus (AjPLA2) has not yet been reported. This study successfully amplified the AjPLA2 sequence. The total cDNA of AjPLA2 is 931 bp, including a 480 bp ORF that encodes 159 amino acids. The AjPLA2 protein includes a 16-aa signal peptide, a 5-aa precursor peptide and a 138-aa mature peptide. Homologous alignment showed that AjPLA2 and the sPLA2s from starfish have the typical domains of the Group IB sPLA2. And additional amino acid sequences were found around the β-Wing, which is different from the Group IB sPLA2. These results showed that AjPLA2 and sPLA2s from starfish all belong to a new group in the Group I sPLA2 family. AjPLA2 is widely distributed in sea cucumber tissues. The functional analysis also showed that AjPLA2 was upregulated in the intestine by feeding. When the body wall was damaged, it was significantly upregulated around the wound. And the expression levels of AjPLA2 were significantly increased in V. splendens-infected sea cucumbers. The results indicated that AjPLA2 plays roles in the sea cucumber immunologic process. Combined with the upregulation of unsaturated fatty acids (PUFAs) content in A. japonicus, it demonstrated that AjPLA2 could participate in the immune of A. japonicus by hydrolyzing phospholipid and releasing PUFAs. This study had a solid foundation for the further research of AjPLA2 gene function in vivo, development and application of AjPLA2 protein.

A newly identified secretory phospholipase A2 group XIIA homolog (LcPLA2XIIA) in Larimichthys crocea exhibits antimicrobial and antitumor activities

The phospholipase A2 (PLA2) superfamily has attracted increasing attention in recent years due to the multiple physiological and pathological functions exerted by its members. Up to date, the knowledge about the biological role of PLA2XIIA subfamily members remains limited. In this study, a new member of PLA2XIIA subfamily, LcPLA2XIIA, was characterized in large yellow croaker. Different from most members of the PLA2 superfamily with positive charge, LcPLA2XIIA encodes an anionic protein, which is similar to other members of PLA2XIIA subfamily. LcPLA2XIIA is highly expressed in the intestine, and afterwards, it is up-regulated after with Pseudomonas plecoglossicida or Staphylococcus aureus. LcPLA2XIIA exhibits strong inhibitory activity against these two bacteria. The results indicate that LcPLA2XIIA plays an important role in the antimicrobial immune responses of large yellow croaker. LcPLA2XIIA displays strong binding activity to all the tested bacteria. It specifically interacts with LTA, a unique component on the surface of Gram-positive bacteria. It also significantly promotes bacterial agglutination in the presence of Ca2+. These findings reveal that the binding and agglutinating abilities of LcPLA2XIIA to bacteria contribute greatly to its antibacterial activity. In addition, LcPLA2XIIA significantly inhibits the proliferation of infectious hematopoietic necrosis virus instead of recombinant human adenovirus type 5. It also suppresses the growth of human colorectal adenocarcinoma cells by inducing apoptosis, but it has no obvious inhibitory effect on the growth of epithelioma papulosum cyprinid cells. This study provides new insights into the antibacterial activity, and the mechanism of LcPLA2XIIA in large yellow croaker, and antiviral and antitumor functions of PLA2XIIA subfamily members.

An in-depth exploration of snake venom-derived molecules for drug discovery in advancing antiviral therapeutics

Snake venom is a cocktail and rich source of various bioactive compounds that have been extensively studied for their potential as pharmaceutical agents due to their diverse chemical structures and wide range of biological activities. In light of the emergency and the re-emergence of viral infectious diseases that threaten human health and economic systems, exploring new fertile and rich fields such as snake venom is an attractive path for anti-viral drug discovery, especially in the lack of effective vaccines. Although 85 % of reported antiviral molecules belong to the phospholipase A2 (PLA2) family, other protein families including L-amino acid oxidases (LAAO), disintegrins, metalloproteases (SVMPs), and cathelicidins have also shown antiviral activity. Thus, in this review, we have highlighted the antiviral properties of compounds derived from snake venom and their mechanisms of action against virus classes like HIV, Coronaviridae, Flaviviridae, and Paramyxoviridae. Although the initial research emphasis has been on Retroviridae (HIV) and Flaviviridae viruses, it is crucial to extend the exploration of the potential of these compounds to other viruses. The utilization of snake venom-derived compounds as antivirals shows significant promise for the development of novel therapeutics to address viral infections. However, a more in-depth investigation is necessary to fully assess the potential of these compounds against other viruses and unveil the mechanisms underlying their action.

Secreted phospholipase PLA2G2E contributes to regulation of T cell immune response against influenza virus infection

The involvement of secreted phospholipase A2s in respiratory diseases, such as asthma and respiratory viral infections, is well-established. However, the specific role of secreted phospholipase A2 group IIE (PLA2G2E) during influenza virus infection remains unexplored. Here, we investigated the role of PLA2G2E during H1N1 influenza virus infection using a targeted mouse model lacking Pla2g2e gene (Pla2g2e-/-). Our findings demonstrated that Pla2g2e-/- mice had significantly lower survival rates and higher viral loads in lungs compared to wild-type mice following influenza virus infection. While Pla2g2e-/- mice displayed comparable innate and humoral immune responses to influenza virus challenge, the animals showed impaired influenza-specific cellular immunity and reduced T cell-mediated cytotoxicity. This indicates that PLA2G2E is involved in regulating specific T cell responses during influenza virus infection. Furthermore, transgenic mice expressing the human PLA2G2E gene exhibited resistance to influenza virus infection along with enhanced influenza-specific cellular immunity and T cell-mediated cytotoxicity. Pla2g2e deficiency resulted in perturbation of lipid mediators in the lung and T cells, potentially contributing to its impact on the anti-influenza immune response. Taken together, these findings suggest that targeting PLA2G2E could hold potential as a therapeutic strategy for managing influenza virus infections.IMPORTANCEThe influenza virus is a highly transmissible respiratory pathogen that continues to pose a significant public health concern. It effectively evades humoral immune protection conferred by vaccines and natural infection due to its continuous viral evolution through the genetic processes of antigenic drift and shift. Recognition of conserved non-mutable viral epitopes by T cells may provide broad immunity against influenza virus. In this study, we have demonstrated that phospholipase A2 group IIE (PLA2G2E) plays a crucial role in protecting against influenza virus infection through the regulation of T cell responses, while not affecting innate and humoral immune responses. Targeting PLA2G2E could therefore represent a potential therapeutic strategy for managing influenza virus infection.

Plasma proteomic profiling identifies CD33 as a marker of HIV control in natural infection and after therapeutic vaccination

BACKGROUND

Biomarkers predicting the outcome of HIV-1 virus control in natural infection and after therapeutic interventions in HIV-1 cure trials remain poorly defined. The BCN02 trial (NCT02616874), combined a T-cell vaccine with romidepsin (RMD), a cancer-drug that was used to promote HIV-1 latency reversal and which has also been shown to have beneficial effects on neurofunction. We conducted longitudinal plasma proteomics analyses in trial participants to define biomarkers associated with virus control during monitored antiretroviral pause (MAP) and to identify novel therapeutic targets that can improve future cure strategies.

METHODS

BCN02 was a phase I, open-label, single-arm clinical trial in early-treated, HIV infected individuals. Longitudinal plasma proteomes were analyzed in 11 BCN02 participants, including 8 participants that showed a rapid HIV-1 plasma rebound during a monitored antiretroviral pause (MAP-NC, 'non-controllers') and 3 that remained off ART with sustained plasma viremia <2000 copies/ml (MAP-C, 'controllers'). Inflammatory and neurological proteomes in plasma were evaluated and integration data analysis (viral and neurocognitive parameters) was performed. Validation studies were conducted in a cohort of untreated HIV-1+ individuals (n = 96) and in vitro viral replication assays using an anti-CD33 antibody were used for functional validation.

FINDINGS

Inflammatory plasma proteomes in BCN02 participants showed marked longitudinal alterations. Strong proteome differences were also observed between MAP-C and MAP-NC, including in baseline timepoints. CD33/Siglec-3 was the unique plasma marker with the ability to discriminate between MAPC-C and MAP-NC at all study timepoints and showed positive correlations with viral parameters. Analyses in an untreated cohort of PLWH confirmed the positive correlation between viral parameters and CD33 plasma levels, as well as PBMC gene expression. Finally, adding an anti-CD33 antibody to in vitro virus cultures significantly reduced HIV-1 replication and proviral levels in T cells and macrophages.

INTERPRETATION

This study indicates that CD33/Siglec-3 may serve as a predictor of HIV-1 control and as potential therapeutic tool to improve future cure strategies.

FUNDING

Spanish Science and Innovation Ministry (SAF2017-89726-R and PID2020-119710RB-I00), NIH (P01-AI131568), European Commission (GA101057548) and a Grifols research agreement.

Lipases secreted by a gut bacterium inhibit arbovirus transmission in mosquitoes

Arboviruses are etiological agents of various severe human diseases that place a tremendous burden on global public health and the economy; compounding this issue is the fact that effective prophylactics and therapeutics are lacking for most arboviruses. Herein, we identified 2 bacterial lipases secreted by a Chromobacterium bacterium isolated from Aedes aegypti midgut, Chromobacterium antiviral effector-1 (CbAE-1) and CbAE-2, with broad-spectrum virucidal activity against mosquito-borne viruses, such as dengue virus (DENV), Zika virus (ZIKV), Japanese encephalitis virus (JEV), yellow fever virus (YFV) and Sindbis virus (SINV). The CbAEs potently blocked viral infection in the extracellular milieu through their lipase activity. Mechanistic studies showed that this lipase activity directly disrupted the viral envelope structure, thus inactivating infectivity. A mutation in the lipase motif of CbAE-1 fully abrogated the virucidal ability. Furthermore, CbAEs also exert lipase-dependent entomopathogenic activity in mosquitoes. The anti-arboviral and entomopathogenic properties of CbAEs render them potential candidates for the development of novel transmission control strategies against vector-borne diseases.

Mosquito-borne viruses are the etiological agents of severe human diseases and annually lead to a great number of deaths. These viruses have spread widely and raised major public health concerns throughout the world. Although effective vaccines have been developed for a few mosquito-borne viruses, such as JEV and yellow fever virus (YFV), vaccines or antiviral therapeutics against most mosquito-borne viruses are currently unavailable. In this study, we identified two virucidal and entomopathogenic effectors with lipase activity, CbAE-1 and CbAE-2, from a mosquito midgut derived bacterium Chromobacterium sp. Beijing. Both CbAEs showed potent virucidal activity against a variety of mosquito-borne viruses, including DENV, ZIKV, JEV, YFV, and SINV, as well as other enveloped viruses. Since CbAEs inactivate viruses through their lipase activity by directly disrupting the viral envelope structure, they may provide a novel option for genetically engineering microbiota symbiotic with mosquitoes for arboviral control. Overall, the anti-arboviral and entomopathogenic properties of Csp_BJ and CbAEs render them particularly interesting candidates for the development of novel transmission control strategies against vector-borne diseases.

Anti-HIV Activity of Snake Venom Phospholipase A2s: Updates for New Enzymes and Different Virus Strains

Since the beginning of the HIV epidemic, lasting more than 30 years, the main goal of scientists was to develop effective methods for the prevention and treatment of HIV infection. Modern medicines have reduced the death rate from AIDS by 80%. However, they still have side effects and are very expensive, dictating the need to search for new drugs. Earlier, it was shown that phospholipases A2 (PLA2s) from bee and snake venoms block HIV replication, the effect being independent on catalytic PLA2 activity. However, the antiviral activity of human PLA2s against Lentiviruses depended on catalytic function and was mediated through the destruction of the viral membrane. To clarify the role of phospholipolytic activity in antiviral effects, we analyzed the anti-HIV activity of several snake PLA2s and found that the mechanisms of their antiviral activity were similar to that of mammalian PLA2. Our results indicate that snake PLA2s are capable of inhibiting syncytium formation between chronically HIV-infected cells and healthy CD4-positive cells and block HIV binding to cells. However, only dimeric PLA2s had pronounced virucidal and anti-HIV activity, which depended on their catalytic activity. The ability of snake PLA2s to inactivate the virus may provide an additional barrier to HIV infection. Thus, snake PLA2s might be considered as candidates for lead molecules in anti-HIV drug development.

What do secreted phospholipases A2 have to offer in combat against different viruses up to SARS-CoV-2?

Secreted phospholipases A2 (sPLA2s) form a widespread group of structurally-related enzymes that catalyse the hydrolysis of the sn-2 ester bond of glycerophospholipids to produce free fatty acids and lysophospholipids. In humans, nine catalytically active and two inactive sPLA2 proteins have been identified. These enzymes play diverse biological roles, including host defence against bacteria, parasites and viruses. Several of these endogenous sPLA2s may play a defensive role in viral infections, as they display in vitro antiviral activity by both direct and indirect mechanisms. However, endogenous sPLA2s may also exert an offensive and negative role, dampening the antiviral response or promoting inflammation in animal models of viral infection. Similarly, several exogenous sPLA2s, most of them from snake venoms and other animal venoms, possess in vitro antiviral activities. Thus, both endogenous and exogenous sPLA2s may be exploited for the development of new antiviral substances or as therapeutic targets for antagonistic drugs that may promote a more robust antiviral response. In this review, the antiviral versus proviral role of both endogenous and exogenous sPLA2s against various viruses including coronaviruses is presented. Based on the highlighted developments in this area of research, possible directions of future investigation are envisaged. One of them is also a possibility of exploiting sPLA2s as biological markers of the severity of the Covid-19 pandemic caused by SARS-CoV-2 infection.

Role of human group IIA secreted phospholipase A2 in malaria pathophysiology: Insights from a transgenic mouse model

We previously showed that injection of recombinant human group IIA secreted phospholipase A₂ (hGIIA sPLA₂) to Plasmodium chabaudi-infected mice lowers parasitaemia by 20%. Here, we show that transgenic (TG) mice overexpressing hGIIA sPLA₂ have a peak of parasitaemia about 30% lower than WT littermates. During infection, levels of circulating sPLA₂, enzymatic activity and plasma lipid peroxidation were maximal at day-14, the peak of parasitaemia. Levels of hGIIA mRNA increased in liver but not in spleen and blood cells, suggesting that liver may contribute as a source of circulating hGIIA sPLA₂. Before infection, baseline levels of leukocytes and pro-inflammatory cytokines were higher in TG mice than WT littermates. Upon infection, the number of neutrophils, lymphocytes and monocytes increased and were maximal at the peak of parasitaemia in both WT and TG mice, but were higher in TG mice. Similarly, levels of the Th1 cytokines IFN-γ and IL-2 increased in WT and TG mice, but were 7.7- and 1.7-fold higher in TG mice. The characteristic shift towards Th2 cytokines was observed during infection in both WT and TG mice, with increased levels of IL-10 and IL-4 at day-14. The current data are in accordance with our previous in vitro findings showing that hGIIA kills parasites by releasing toxic lipids from oxidized lipoproteins. They further show that hGIIA sPLA₂ is induced during mouse experimental malaria and has a protective in vivo role, lowering parasitaemia by likely releasing toxic lipids from oxidized lipoproteins but also indirectly by promoting a more sustained innate immune response.

Snake venom phospholipase A2s exhibit strong virucidal activity against SARS-CoV-2 and inhibit the viral spike glycoprotein interaction with ACE2

The COVID-19 pandemic caused by SARS-CoV-2 requires new treatments both to alleviate the symptoms and to prevent the spread of this disease. Previous studies demonstrated good antiviral and virucidal activity of phospholipase A₂s (PLA₂s) from snake venoms against viruses from different families but there was no data for coronaviruses. Here we show that PLA₂s from snake venoms protect Vero E6 cells against SARS-CoV-2 cytopathic effects. PLA₂s showed low cytotoxicity to Vero E6 cells with some activity at micromolar concentrations, but strong antiviral activity at nanomolar concentrations. Dimeric PLA₂ from the viper Vipera nikolskii and its subunits manifested especially potent virucidal effects, which were related to their phospholipolytic activity, and inhibited cell-cell fusion mediated by the SARS-CoV-2 spike glycoprotein. Moreover, PLA₂s interfered with binding both of an antibody against ACE2 and of the receptor-binding domain of the glycoprotein S to 293T/ACE2 cells. This is the first demonstration of a detrimental effect of PLA₂s on β-coronaviruses. Thus, snake PLA₂s are promising for the development of antiviral drugs that target the viral envelope, and could also prove to be useful tools to study the interaction of viruses with host cells.

Ten-Year Research Update Review: Antiviral Activities from Marine Organisms

Oceans cover more than 70 percent of the surface of our planet and are characterized by huge taxonomic and chemical diversity of marine organisms. Several studies have shown that marine organisms produce a variety of compounds, derived from primary or secondary metabolism, which may have antiviral activities. In particular, certain marine metabolites are active towards a plethora of viruses. Multiple mechanisms of action have been found, as well as different targets. This review gives an overview of the marine-derived compounds discovered in the last 10 years. Even if marine organisms produce a wide variety of different compounds, there is only one compound available on the market, Ara-A, and only another one is in phase I clinical trials, named Griffithsin. The recent pandemic emergency caused by SARS-CoV-2, also known as COVID-19, highlights the need to further invest in this field, in order to shed light on marine compound potentiality and discover new drugs from the sea.

Characterization of novel monoclonal antibodies against MERS-coronavirus spike protein

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Identification of neutralizing mAbs using MERS-CoV spike-pseudotyped virus.

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Transmembrane domain-deleted spike subunit protein induced neutralizing antibodies.

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Neutralizing antibodies could bind to RBD of MERS-CoV spike, but not vice versa.

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Mutation in residue 506–509 or 529 of S elicits neutralization escape of MERS-CoV.

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Our mAbs can be utilized for identification of specific mutation of MERS-CoV.

Middle East Respiratory Syndrome coronavirus (MERS-CoV) causes severe pulmonary infection, with ∼35 % mortality. Spike glycoprotein (S) of MERS-CoV is a key target for vaccines and therapeutics because S mediates viral entry and membrane-fusion to host cells. Here, four different S subunit proteins, receptor-binding domain (RBD; 358–606 aa), S1 (1–751 aa), S2 (752–1296 aa), and SΔTM (1–1296 aa), were generated using the baculoviral system and immunized in mice to develop neutralizing antibodies. We developed 77 hybridomas and selected five neutralizing mAbs by immunization with SΔTM against MERS-CoV EMC/2012 strain S-pseudotyped lentivirus. However, all five monoclonal antibodies (mAb) did not neutralize the pseudotyped V534A mutation. Additionally, one mAb RBD-14F8 did not show neutralizing activity against pseudoviruses with amino acid substitution of L506 F or D509 G (England1 strain, EMC/2012 L506 F, and EMC/2012 D509 G), and RBD-43E4 mAb could not neutralize the pseudotyped I529 T mutation, while three other neutralizing mAbs showed broad neutralizing activity. This implies that the mutation in residue 506–509, 529, and 534 of S is critical to generate neutralization escape variants of MERS-CoV. Interestingly, all five neutralizing mAbs have binding affinity to RBD, although most mAbs generated by RBD did not have neutralizing activity. Additionally, chimeric antibodies of RBD-14F8 and RBD-43E4 with human Fc and light chain showed neutralizing effect against wild type MERS-CoV KOR/KNIH/002, similar to the original mouse mAbs. Thus, our mAbs can be utilized for the identification of specific mutations of MERS-CoV.

A nanoparticle pseudo pathogen for rapid detection and diagnosis of virus infection

We herein report a new rapid blood test for virus infection detection and diagnosis. A citrate gold nanoparticle is first coated with a virus lysate to form a gold nanoparticle pseudo pathogen. The gold nanoparticle pseudo virus is then mixed with a blood plasma or serum samples. If the blood sample is from a positive patient, the activated immune molecules in the blood such as antibodies, complement proteins and others will react with the nanoparticle pseudo virus, leading to nanoparticle aggregate formation. The nanoparticle aggregate formation is detected and measured using a particle sizing technique called dynamic light scattering. In this study, we applied this test for Zika virus infection detection. We tested blood plasma samples from 85 Zika positive patients, 40 Dengue positive patients, 10 Chikungunya positive patients, and 78 non-patient control samples collected from both endemic and non-endemic locations. The study shows that the new test has a higher sensitivity compared to some existing commercial tests in the market, while maintaining a similar specificity. Within 7 days from the symptom onset, the new test can detect 43% of the infected patients while a commercial anti-Zika IgM test detects only 26% of the infected patients. Within 14 days from the symptom onset, our new test detects 73% of the infected patients while the same commercial anti-Zika IgM test detects 53% of the infected patients. The test is extremely simple, easy to develop, with test results obtained within minutes. This new test platform may be potentially adapted for the detection and diagnosis of a wide range of viral infectious diseases, for example, the currently ongoing COVID-19.

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A rapid blood test for point-of-care virus infectious disease detection and diagnosis.

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The test uses a gold nanoparticle pseudo virus particle to detect active immune response from patient’s blood.

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The test is a single-step process with results obtained within 20 min.

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The test shows significantly better sensitivity than a commercially available serology test.

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The test platform may be adapted to develop diagnostic tests for different virus infections.

Antimalarial Activity of Human Group IIA Secreted Phospholipase A2 in Relation to Enzymatic Hydrolysis of Oxidized Lipoproteins

The level of human group IIA secreted phospholipase A₂ (hGIIA sPLA₂) is increased in the plasma of malaria patients, but its role is unknown. In parasite culture with normal plasma, hGIIA is inactive against Plasmodium falciparum, contrasting with hGIIF, hGV, and hGX sPLA₂s, which readily hydrolyze plasma lipoproteins, release nonesterified fatty acids (NEFAs), and inhibit parasite growth. Here, we revisited the anti-Plasmodium activity of hGIIA under conditions closer to those of malaria physiopathology where lipoproteins are oxidized. In parasite culture containing oxidized lipoproteins, hGIIA sPLA₂ was inhibitory, with a 50% inhibitory concentration value of 150.0 ± 40.8 nM, in accordance with its capacity to release NEFAs from oxidized particles. With oxidized lipoproteins, hGIIF, hGV, and hGX sPLA₂s were also more potent, by 4.6-, 2.1-, and 1.9-fold, respectively. Using specific immunoassays, we found that hGIIA sPLA₂ is increased in plasma from 41 patients with malaria over levels for healthy donors (median [interquartile range], 1.6 [0.7 to 3.4] nM versus 0.0 [0.0 to 0.1] nM, respectively; P < 0.0001). Other sPLA₂s were not detected. Malaria plasma, but not normal plasma, contains oxidized lipoproteins and was inhibitory to P. falciparum when spiked with hGIIA sPLA₂ Injection of recombinant hGIIA into mice infected with P. chabaudi reduced the peak of parasitemia, and this was effective only when the level of plasma peroxidation was increased during infection. In conclusion, we propose that malaria-induced oxidation of lipoproteins converts these into a preferential substrate for hGIIA sPLA₂, promoting its parasite-killing effect. This mechanism may contribute to host defense against P. falciparum in malaria where high levels of hGIIA are observed.

Antiretroviral activity of Pterois volitans (red lionfish) venom in the early development of human immunodeficiency virus/acquired immunodeficiency syndrome antiretroviral alternative source

Aim

This study aimed to investigate the antiviral activity of Pterois volitans phospholipase A2 (PV-PLA2) from Indonesia to human immunodeficiency virus (HIV).

Materials and Methods

Fresh venomous fin parts of wild PV specimens were collected from Java Sea waters. Then, it washed using phosphate buffer pH 7.0 and immersed in phosphate buffer pH 7.0 0.01 m containing CaCl₂ 0.001 m for 24 h. The immersed fin then allowed for extraction process by sonicating for 2×8 min with 80% pulse and 20 kHz output with temperature controlling to avoid denaturation. The crude venom (CV) extracted from the fin is allowed for purification by 80% ethanol (ET) precipitation and ammonium sulfate fractionation method. The purified PV-PLA2 then analyzed using Lowry's method, Marinette's method, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and 3-(4, 5-dimethyl thiazol-2yl)-2, 5-diphenyl tetrazolium bromide assay. After determining the purest and safest sample of six samples analyzed, the chosen sample then tested into simian retrovirus-2 (SRV2)-A549 culture (48×10⁴ cells/mL at 1-4 ppm), and compared to the CV sample (1-4 ppm) and lamivudine (100 ppm). The culture then is analyzed using a quantitative real time-polymerase chain reaction to find out the copy number of SRV-2 virus in each culture.

Results

The protein's activity, concentration, and purity analysis revealed that the PV-PLA2 purified using ammonium sulfate fractionation has the highest activity (1.81 times higher than the CV at 80% fractionation) and has higher purity than the sample from ET fractionation. The testing of the sample purified using ammonium sulfate fractionation at 80% saturation level shown that it has a 97.78% inhibition level toward SRV2-A549 culture at 4 ppm. However, in comparison to lamivudine which has 99.55% inhibition level at 100 ppm, it needs much lower concentration to achieve the same result.

Conclusion

The significant inhibition of SRV2-A549 culture shown that the PV-PLA2 extracted from PV venom has the potential to become anti-HIV substances. It would be worthwhile to further evaluate the antiretroviral activity of PV-PLA2 in the in vivo studies.

Antiviral activity of Acanthaster planci phospholipase A2 against human immunodeficiency virus

AIM

Investigation of antiviral activity of Acanthaster planci phospholipase A2 (AP-PLA2) from moluccas to human immunodeficiency virus (HIV).

MATERIALS AND METHODS

Crude venom (CV) and F20 (PLA2 with 20% fractioned by ammonium sulfate) as a sample of PLA 2 obtained from A. planci's extract were used. Enzymatic activity of PLA2 was determined using the degradation of phosphatidylcholine (PC). Activity test was performed using in vitro method using coculture of phytohemagglutinin-stimulated peripheral blood mononuclear cell (PBMC) from a blood donor and PBMC from HIV patient. Toxicity test of AP-PLA2 was done using lethal concentration required to kill 50% of the population (LC50).

RESULTS

AP-PLA2 F20 had activity and purity by 15.66 times bigger than CV. The test showed that the LC50 of AP-PLA2 is 1.638 mg/ml. Antiviral analysis of AP-PLA2 in vitro showed the inhibition of HIV infection to PBMC. HIV culture with AP-PLA2 and without AP-PLA2 has shown the number of infected PBMC (0.299±0.212% and 9.718±0.802%). Subsequently, RNA amplification of HIV using reverse transcriptase-polymerase chain reaction resulted in the decrease of band intensity in gag gene of HIV.

CONCLUSION

This research suggests that AP-PLA2 has the potential to develop as an antiviral agent because in vitro experiment showed its ability to decrease HIV infection in PBMC and the number of HIV ribonucleic acid in culture.

Broad-spectrum antiviral agents: secreted phospholipase A2 targets viral envelope lipid bilayers derived from the endoplasmic reticulum membrane

Hepatitis C virus (HCV), dengue virus (DENV) and Japanese encephalitis virus (JEV) belong to the family Flaviviridae. Their viral particles have the envelope composed of viral proteins and a lipid bilayer acquired from budding through the endoplasmic reticulum (ER). The phospholipid content of the ER membrane differs from that of the plasma membrane (PM). The phospholipase A2 (PLA2) superfamily consists of a large number of members that specifically catalyse the hydrolysis of phospholipids at a particular position. Here we show that the CM-II isoform of secreted PLA2 obtained from Naja mossambica mossambica snake venom (CM-II-sPLA2) possesses potent virucidal (neutralising) activity against HCV, DENV and JEV, with 50% inhibitory concentrations (IC50) of 0.036, 0.31 and 1.34 ng/ml, respectively. In contrast, the IC50 values of CM-II-sPLA2 against viruses that bud through the PM (Sindbis virus, influenza virus and Sendai virus) or trans-Golgi network (TGN) (herpes simplex virus) were >10,000 ng/ml. Moreover, the 50% cytotoxic (CC50) and haemolytic (HC50) concentrations of CM-II-sPLA2 were >10,000 ng/ml, implying that CM-II-sPLA2 did not significantly damage the PM. These results suggest that CM-II-sPLA2 and its derivatives are good candidates for the development of broad-spectrum antiviral drugs that target viral envelope lipid bilayers derived from the ER membrane.

In vitro anti-Plasmodium falciparum properties of the full set of human secreted phospholipases A2

We have previously shown that secreted phospholipases A2 (sPLA2s) from animal venoms inhibit the in vitro development of Plasmodium falciparum, the agent of malaria. In addition, the inflammatory-type human group IIA (hGIIA) sPLA2 circulates at high levels in the serum of malaria patients. However, the role of the different human sPLA2s in host defense against P. falciparum has not been investigated. We show here that 4 out of 10 human sPLA2s, namely, hGX, hGIIF, hGIII, and hGV, exhibit potent in vitro anti-Plasmodium properties with half-maximal inhibitory concentrations (IC50s) of 2.9 ± 2.4, 10.7 ± 2.1, 16.5 ± 9.7, and 94.2 ± 41.9 nM, respectively. Other human sPLA2s, including hGIIA, are inactive. The inhibition is dependent on sPLA2 catalytic activity and primarily due to hydrolysis of plasma lipoproteins from the parasite culture. Accordingly, purified lipoproteins that have been prehydrolyzed by hGX, hGIIF, hGIII, and hGV are more toxic to P. falciparum than native lipoproteins. However, the total enzymatic activities of human sPLA2s on purified lipoproteins or plasma did not reflect their inhibitory activities on P. falciparum. For instance, hGIIF is 9-fold more toxic than hGV but releases a lower quantity of nonesterified fatty acids (NEFAs). Lipidomic analyses of released NEFAs from lipoproteins demonstrate that sPLA2s with anti-Plasmodium properties are those that release polyunsaturated fatty acids (PUFAs), with hGIIF being the most selective enzyme. NEFAs purified from lipoproteins hydrolyzed by hGIIF were more potent at inhibiting P. falciparum than those from hGV, and PUFA-enriched liposomes hydrolyzed by sPLA2s were highly toxic, demonstrating the critical role of PUFAs. The selectivity of sPLA2s toward low- and high-density (LDL and HDL, respectively) lipoproteins and their ability to directly attack parasitized erythrocytes further explain their anti-Plasmodium activity. Together, our findings indicate that 4 human sPLA2s are active against P. falciparum in vitro and pave the way to future investigations on their in vivo contribution in malaria pathophysiology.

Phospholipase A2 isolated from the venom of Crotalus durissus terrificus inactivates dengue virus and other enveloped viruses by disrupting the viral envelope

The Flaviviridae family includes several virus pathogens associated with human diseases worldwide. Within this family, Dengue virus is the most serious threat to public health, especially in tropical and sub-tropical regions of the world. Currently, there are no vaccines or specific antiviral drugs against Dengue virus or against most of the viruses of this family. Therefore, the development of vaccines and the discovery of therapeutic compounds against the medically most important flaviviruses remain a global public health priority. We previously showed that phospholipase A₂ isolated from the venom of Crotalus durissus terrificus was able to inhibit Dengue virus and Yellow fever virus infection in Vero cells. Here, we present evidence that phospholipase A₂ has a direct effect on Dengue virus particles, inducing a partial exposure of genomic RNA, which strongly suggests inhibition via the cleavage of glycerophospholipids at the virus lipid bilayer envelope. This cleavage might induce a disruption of the lipid bilayer that causes a destabilization of the E proteins on the virus surface, resulting in inactivation. We show by computational analysis that phospholipase A₂ might gain access to the Dengue virus lipid bilayer through the pores found on each of the twenty 3-fold vertices of the E protein shell on the virus surface. In addition, phospholipase A₂ is able to inactivate other enveloped viruses, highlighting its potential as a natural product lead for developing broad-spectrum antiviral drugs.

Lack of group X secreted phospholipase A₂ increases survival following pandemic H1N1 influenza infection

The role of Group X secreted phospholipase A2 (GX-sPLA2) during influenza infection has not been previously investigated. We examined the role of GX-sPLA2 during H1N1 pandemic influenza infection in a GX-sPLA2 gene targeted mouse (GX(-/-)) model and found that survival after infection was significantly greater in GX(-/-) mice than in GX(+/+) mice. Downstream products of GX-sPLA2 activity, PGD2, PGE2, LTB4, cysteinyl leukotrienes and Lipoxin A4 were significantly lower in GX(-/-) mice BAL fluid. Lung microarray analysis identified an earlier and more robust induction of T and B cell associated genes in GX(-/-) mice. Based on the central role of sPLA2 enzymes as key initiators of inflammatory processes, we propose that activation of GX-sPLA2 during H1N1pdm infection is an early step of pulmonary inflammation and its inhibition increases adaptive immunity and improves survival. Our findings suggest that GX-sPLA2 may be a potential therapeutic target during influenza.

Secreted phospholipase A2 is increased in meconium-stained amniotic fluid of term gestations: potential implications for the genesis of meconium aspiration syndrome

BACKGROUND

Meconium-stained amniotic fluid (MSAF) represents the passage of fetal colonic content into the amniotic cavity. Meconium aspiration syndrome (MAS) is a complication that occurs in a subset of infants with MSAF. Secreted phospholipase A2 (sPLA2) is detected in meconium and is implicated in the development of MAS. The purpose of this study was to determine if sPLA2 concentrations are increased in the amniotic fluid of women in spontaneous labor at term with MSAF.

MATERIALS AND METHODS

This was a cross-sectional study of patients in spontaneous term labor who underwent amniocentesis (n = 101). The patients were divided into two study groups: (1) MSAF (n = 61) and (2) clear fluid (n = 40). The presence of bacteria and endotoxin as well as interleukin-6 (IL-6) and sPLA2 concentrations in the amniotic fluid were determined. Statistical analyses were performed to test for normality and bivariate analysis. The Spearman correlation coefficient was used to study the relationship between sPLA2 and IL-6 concentrations in the amniotic fluid.

RESULTS

Patients with MSAF have a higher median sPLA2 concentration (ng/mL) in amniotic fluid than those with clear fluid [1.7 (0.98-2.89) versus 0.3 (0-0.6), p < 0.001]. Among patients with MSAF, those with either microbial invasion of the amniotic cavity (MIAC, defined as presence of bacteria in the amniotic cavity), or bacterial endotoxin had a significantly higher median sPLA2 concentration (ng/mL) in amniotic fluid than those without MIAC or endotoxin [2.4 (1.7-6.0) versus 1.7 (1.3-2.5), p < 0.05]. There was a positive correlation between sPLA2 and IL-6 concentrations in the amniotic fluid (Spearman Rho = 0.3, p < 0.05).

CONCLUSION

MSAF that contains bacteria or endotoxin has a higher concentration of sPLA2, and this may contribute to induce lung inflammation when meconium is aspirated before birth.

Crotoxin and phospholipases A₂ from Crotalus durissus terrificus showed antiviral activity against dengue and yellow fever viruses

Dengue is the most important arbovirus in the world with an estimated of 50 million dengue infections occurring annually and approximately 2.5 billion people living in dengue endemic countries. Yellow fever is a viral hemorrhagic fever with high mortality that is transmitted by mosquitoes. Effective vaccines against yellow fever have been available for almost 70 years and are responsible for a significant reduction of occurrences of the disease worldwide; however, approximately 200,000 cases of yellow fever still occur annually, principally in Africa. Therefore, it is a public health priority to develop antiviral agents for treatment of these virus infections. Crotalus durissus terrificus snake, a South American rattlesnake, presents venom with several biologically actives molecules. In this study, we evaluated the antiviral activity of crude venom and isolated toxins from Crotalus durissus terrificus and found that phospholipases A₂ showed a high inhibition of Yellow fever and dengue viruses in VERO E6 cells.

Emerging roles of secreted phospholipase A2 enzymes: Lessons from transgenic and knockout mice

Among the emerging phospholipase A(2) (PLA(2)) superfamily, the secreted PLA(2) (sPLA(2)) family consists of low-molecular-mass, Ca(2+)-requiring extracellular enzymes with a His-Asp catalytic dyad. To date, more than 10 sPLA(2) enzymes have been identified in mammals. Individual sPLA(2)s exhibit unique tissue and cellular localizations and enzymatic properties, suggesting their distinct pathophysiological roles. Despite numerous enzymatic and cell biological studies on this enzyme family in the past two decades, their precise in vivo functions still remain largely obscure. Recent studies using transgenic and knockout mice for several sPLA(2) enzymes, in combination with lipidomics approaches, have opened new insights into their distinct contributions to various biological events such as food digestion, host defense, inflammation, asthma and atherosclerosis. In this article, we overview the latest understanding of the pathophysiological functions of individual sPLA(2) isoforms fueled by studies employing transgenic and knockout mice for several sPLA(2)s.

Hypothesis of snake and insect venoms against Human Immunodeficiency Virus: a review

Background

Snake and insect venoms have been demonstrated to have beneficial effects in the treatment of certain diseases including drug resistant human immunodeficiency virus (HIV) infection. We evaluated and hypothesized the probable mechanisms of venoms against HIV.

Methods

Previous literatures published over a period of 30 years (1979-2009) were searched using the key words snake venom, insect venom, mechanisms and HIV. Mechanisms were identified and discussed.

Results & Conclusion

With reference to mechanisms of action, properties and components of snake venom such as sequence homology and enzymes (protease or L- amino acid oxidase) may have an effect on membrane protein and/or act against HIV at multiple levels or cells carrying HIV virus resulting in enhanced effect of anti-retroviral therapy (ART). This may cause a decrease in viral load and improvement in clinical as well as immunological status. Insect venom and human Phospholipase A₂ (PLA₂) have potential anti-viral activity through inhibition of virion entry into the cells. However, all these require further evaluation in order to establish its role against HIV as an independent one or as a supplement.

Biology of secretory phospholipase A2

Introduction

The secretory phospholipase A₂ (sPLA₂) family provides a seemingly endless array of potential biological functions that is only beginning to be appreciated. In humans, this family comprises 9 different members that vary in their tissue distribution, hydrolytic activity, and phospholipid substrate specificity. Through their lipase activity, these enzymes trigger various cell-signaling events to regulate cellular functions, directly kill bacteria, or modulate inflammatory responses. In addition, some sPLA₂’s are high affinity ligands for cellular receptors.

Objective

This review merely scratches the surface of some of the actions of sPLA₂s in innate immunity, inflammation, and atherosclerosis. The goal is to provide an overview of recent findings involving sPLA₂s and to point to potential pathophysiologic mechanisms that may become targets for therapy.

Biochemistry and physiology of mammalian secreted phospholipases A2

Phospholipases A(2) (PLA2s) are esterases that hydrolyze the sn-2 ester of glycerophospholipids and constitute one of the largest families of lipid hydrolyzing enzymes. The mammalian genome contains 10 enzymatically active secreted PLA2s (sPLA2s) and two sPLA2-related proteins devoid of lipolytic enzymatic activity. In addition to the well-established functions of one of these enzymes in digestion of dietary phospholipids and another in host defense against bacterial infections, accumulating evidence shows that some of these sPLA2s are involved in arachidonic acid release from cellular phospholipids for the biosynthesis of eicosanoids, especially during inflammation. More speculative results suggest the involvement of one or more sPLA2s in promoting atherosclerosis and cancer. In addition, the mammalian genome encodes several types of sPLA2-binding proteins, and mounting evidence shows that sPLA2s may have functions related to binding to cellular target proteins in a manner independent of their lipolytic enzymatic activity.

TLR3-dependent induction of nitric oxide synthase in RAW 264.7 macrophage-like cells via a cytosolic phospholipase A2/cyclooxygenase-2 pathway

dsRNA is a by-product of viral replication capable of inducing an inflammatory response when recognized by phagocyte cells. In this study, we identify group IVA cytosolic phospholipase A2 (cPLA2alpha) as an effector of the antiviral response. Treatment of RAW 264.7 murine macrophage-like cells with the dsRNA analog polyinosinic:polycytidylic acid (poly-IC) promotes the release of free arachidonic acid that is subsequently converted into PGE2 by the de novo-synthesized cyclooxygenase-2 (COX-2) enzyme. These processes are blocked by the selective cPLA2alpha inhibitor pyrrophenone, pointing out to cPLA2alpha as the effector involved. In keeping with this observation, the cPLA2alpha phosphorylation state increases after cellular treatment with poly-IC. Inhibition of cPLA2alpha expression and activity by either small interfering RNA (siRNA) or pyrrophenone leads to inhibition of the expression of the inducible NO synthase (iNOS) gene. Moreover, COX-2-derived PGE2 production appears to participate in iNOS expression, because siRNA inhibition of COX-2 also leads to inhibition of iNOS, the latter of which is restored by exogenous addition of PGE2. Finally, cellular depletion of TLR3 by siRNA inhibits COX-2 expression, PGE2 generation, and iNOS induction by poly-IC. Collectively, these findings suggest a model for macrophage activation in response to dsRNA, whereby engagement of TLR3 leads to cPLA2alpha-mediated arachidonic acid mobilization and COX-2-mediated PGE2 production, which cooperate to induce the expression of iNOS.