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The precise mechanism leading to profound immunodeficiency of HIV-infected patients is still only partially understood. Here, we show that more than 80% of [CD4.sup.+] T cells from HIV-infected patients have morphological abnormalities. Their membranes exhibited numerous large abnormal membrane microdomains (aMMDs), which trap and inactivate physiological receptors, such as that for IL-7. In patient plasma, we identified phospholipase A2 group IB (PLA2G1B) as the key molecule responsible for the formation of aMMDs. At physiological concentrations, PLA2G1B synergized with the HIV gp41 envelope protein, which appears to be a driver that targets PLA2G1B to the [CD4.sup.+] T cell surface. The PLA2G1B/gp41 pair induced [CD4.sup.+] T cell unresponsiveness (anergy). At high concentrations in vitro, PLA2G1B acted alone, independently of gp41, and inhibited the IL-2, IL-4, and IL-7 responses, as well as TCR-mediated activation and proliferation, of [CD4.sup.+] T cells. PLA2G1B also decreased [CD4.sup.+] T cell survival in vitro, likely playing a role in CD4 lymphopenia in conjunction with its induced IL-7 receptor defects. The effects on [CD4.sup.+] T cell anergy could be blocked by a PLA2G1B- specific neutralizing mAb in vitro and in vivo. The PLA2G1B/gp41 pair constitutes what we believe is a new mechanism of immune dysfunction and a compelling target for boosting immune responses in HIV-infected patients., Introduction [CD4.sup.+] lymphocytes play a critical role in the severe immunodeficiency that characterizes HIV-infected patients. Although fewer than 0.5% of blood [CD4.sup.+] T cells are infected, almost all are dysfunctional. [...]

Secreted phospholipase A2 hydrolyzes surfactant phospholipids and is crucial for the inflammatory cascade; preterm neonates are treated with exogenous surfactant, but the interaction between surfactant and phospholipase is unknown. We hypothesize that this interplay is complex and the enzyme plays a relevant role in neonates needing surfactant replacement. We aimed to: 1) identify phospholipases A2 isoforms expressed in preterm lung; 2) study the enzyme role on surfactant retreatment and function and the effect of exogenous surfactant on the enzyme system; and 3) verify whether phospholipase A2 is linked to respiratory outcomes. In bronchoalveolar lavages of preterm neonates, we measured enzyme activity (alone or with inhibitors), enzyme subtypes, surfactant protein-A, and inflammatory mediators. Surfactant function and phospholipid profile were also tested. Urea ratio was used to obtain epithelial lining fluid concentrations. Follow-up data were prospectively collected. Subtype-IIA is the main phospholipase isoform in preterm lung, although subtype-IB may be significantly expressed. Neonates needing surfactant retreatment have higher enzyme activity (P = 0.021) and inflammatory mediators (P always ≤ 0.001) and lower amounts of phospholipids (P always < 0.05). Enzyme activity was inversely correlated to surfactant adsorption (ρ = −0.6; P = 0.008; adjusted P = 0.009), total phospholipids (ρ = −0.475; P = 0.05), and phosphatidylcholine (ρ = −0.622; P = 0.017). Exogenous surfactant significantly reduced global phospholipase activity (P < 0.001) and subtype-IIA (P = 0.005) and increased dioleoylphosphatidylglycerol (P < 0.001) and surfactant adsorption (P < 0.001). Enzyme activity correlated with duration of ventilation (ρ = 0.679, P = 0.005; adjusted P = 0.04) and respiratory morbidity score at 12 mo postnatal age (τ-b = 0.349, P = 0.037; adjusted P = 0.043) but was not associated with mortality, bronchopulmonary dysplasia, or other long-term respiratory outcomes. [ABSTRACT FROM AUTHOR]

The origin of the impaired CD4 T-cell response and immunodeficiency of HIV-infected patients is still only partially understood. We recently demonstrated that PLA2G1B phospholipase synergizes with the HIV gp41 envelope protein in HIV viremic plasma to induce large abnormal membrane microdomains (aMMDs) that trap and inactivate physiological receptors, such as those for IL-7. However, the mechanism of regulation of PLA2G1B activity by the cofactor gp41 is not known. Here, we developed an assay to directly follow PLA2G1B enzymatic activity on CD4 T-cell membranes. We demonstrated that gp41 directly binds to PLA2G1B and increases PLA2G1B enzymatic activity on CD4 membrane. Furthermore, we show that the conserved 3S sequence of gp41, known to bind to the innate sensor gC1qR, increases PLA2G1B activity in a gC1qR-dependent manner using gC1qR KO cells. The critical role of the 3S motif and gC1qR in the inhibition of CD4 T-cell function by the PLA2G1B/cofactor system in HIV-infected patients led us to screen additional microbial proteins for 3S-like motifs and to study other proteins known to bind to the gC1qR to further investigate the role of the PLA2G1B/cofactor system in other infectious diseases and carcinogenesis. We have thus extended the PLA2G1B/cofactor system to HCV and Staphylococcus aureus infections and additional pathologies where microbial proteins with 3S-like motifs also increase PLA2G1B enzymatic activity. Notably, the bacteria Porphyromonas gingivalis , which is associated with pancreatic ductal adenocarcinoma (PDAC), encodes such a cofactor protein and increased PLA2G1B activity in PDAC patient plasma inhibits the CD4 response to IL-7. Our findings identify PLA2G1B/cofactor system as a CD4 T-cell inhibitor. It involves the gC1qR and disease-specific cofactors which are gC1qR-binding proteins that can contain 3S-like motifs. This mechanism involved in HIV-1 immunodeficiency could play a role in pancreatic cancer and several other diseases. These observations suggest that the PLA2G1B/cofactor system is a general CD4 T-cell inhibitor and pave the way for further studies to better understand the role of CD4 T-cell anergy in infectious diseases and tumor escape., Competing Interests: JT is cofounder and CSO of DIACCURATE, a spin-off of the Institut Pasteur. JP, AM, FB, and LJ are, or were, employees of DIACCURATE. PP was employed by company Truffle Capital. BG receives royalties from the sale of anti-gC1qR antibodies and gC1qR detection assay kit. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Pothlichet, Meola, Bugault, Jeammet, Savitt, Ghebrehiwet, Touqui, Pouletty, Fiore, Sauvanet and Thèze.)

Secreted phospholipase A 2 hydrolyzes surfactant phospholipids and is crucial for the inflammatory cascade; preterm neonates are treated with exogenous surfactant, but the interaction between surfactant and phospholipase is unknown. We hypothesize that this interplay is complex and the enzyme plays a relevant role in neonates needing surfactant replacement. We aimed to: 1 ) identify phospholipases A 2 isoforms expressed in preterm lung; 2 ) study the enzyme role on surfactant retreatment and function and the effect of exogenous surfactant on the enzyme system; and 3 ) verify whether phospholipase A 2 is linked to respiratory outcomes. In bronchoalveolar lavages of preterm neonates, we measured enzyme activity (alone or with inhibitors), enzyme subtypes, surfactant protein-A, and inflammatory mediators. Surfactant function and phospholipid profile were also tested. Urea ratio was used to obtain epithelial lining fluid concentrations. Follow-up data were prospectively collected. Subtype-IIA is the main phospholipase isoform in preterm lung, although subtype-IB may be significantly expressed. Neonates needing surfactant retreatment have higher enzyme activity ( P = 0.021) and inflammatory mediators ( P always ≤ 0.001) and lower amounts of phospholipids ( P always < 0.05). Enzyme activity was inversely correlated to surfactant adsorption (ρ = -0.6; P = 0.008; adjusted P = 0.009), total phospholipids (ρ = -0.475; P = 0.05), and phosphatidylcholine (ρ = -0.622; P = 0.017). Exogenous surfactant significantly reduced global phospholipase activity ( P < 0.001) and subtype-IIA ( P = 0.005) and increased dioleoylphosphatidylglycerol ( P < 0.001) and surfactant adsorption ( P < 0.001). Enzyme activity correlated with duration of ventilation (ρ = 0.679, P = 0.005; adjusted P = 0.04) and respiratory morbidity score at 12 mo postnatal age (τ -b  = 0.349, P = 0.037; adjusted P = 0.043) but was not associated with mortality, bronchopulmonary dysplasia, or other long-term respiratory outcomes.

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., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)