HIV replication is associated to inflammasomes activation, IL-1ß, IL-18 and caspase-1 expression in GALT and peripheral blood.

BACKGROUND: Human immunodeficiency virus (HIV) promotes an inflammatory process, leading to the progressive loss of the functional capacity of the immune system. The HIV infection induces alterations in several tissues, but mainly in the gut-associated lymphoid tissue (GALT). However, the degree of GALT deterioration varies among infected individuals. In fact, it has been shown that HIV-controllers, who spontaneously control viral replication, exhibit a lower inflammatory response, and a relative normal frequency and function of most of the immune cells. Inflammasomes are molecular complexes involved in the inflammatory response, being NLRP1, NLRP3, NLRC4, AIM2 and Pyrin inflammasomes, the best characterized so far. These complexes regulate the maturation of cytokines of the IL-1 family, including IL-1ß and IL-18. These cytokines have been associated with immune activation and expansion of HIV target cells, promoting viral replication. Interesting, some reports indicate that HIV induces the activation of the NLRP3 inflammasome, but the role of this, and other inflammasomes during HIV infection, especially in GALT, remains unclear. OBJECTIVE: To compare the relative expression of inflammasome components and the proinflammatory response related to their activity, between HIV-progressors and HIV-controllers. METHODS: GALT biopsies and peripheral blood mononuclear cells (PBMCs) from 15 HIV-controllers and 15 HIV-progressors were obtained. The relative expression of the following inflammasome components were evaluated by RT-PCR: NLRP3, NLRC4, NLRP1, AIM2, ASC, Caspase-1, IL-1ß and IL-18. In addition, plasma concentration of IL-18 was evaluated as an indicator of baseline proinflammatory status. Finally, in supernatants of PBMCs in vitro stimulated with inflammasome agonists, the concentrations of IL-1ß and IL-18 were quantified by ELISA. RESULTS: HIV-progressors exhibited higher expression of IL-1ß, IL-18 and caspase-1 genes in GALT and PBMCs compared with HIV-controllers. In addition, HIV-progressors had also increased expression of ASC in PBMCs. When plasma levels were evaluated, IL-18 was increased in HIV-progressors. Interesting, these patients also showed an increased production of IL-1ß in supernatants of PBMCs stimulated in vitro with the agonists of AIM2, NLRP1 and NLRC4 inflammasomes. Finally, the expression of caspase-1, NLRP1, IL-1ß and IL-18 in GALT or peripheral blood was correlated with CD4+ T-cell count and viral load. CONCLUSION: Our results suggest that during HIV-infection, the required signals to induce the expression of different components of the inflammasomes are produced, both in GALT and in periphery. The activation of these molecular complexes could increase the number of target cells, favoring HIV replication and cell death, promoting the disease progression.

Inflamación y respuesta inmune innata: participación de las lipoproteínas de alta densidad / Inflammation and innate immune response: role of high-density lipoprotein / Inflamação e resposta imune inata: participação das lipoproteínas de altadensidade

RESUMEN Las lipoproteínas de alta densidad (HDL) tienen como función transportar el exceso de colesterol desde los tejidos hacia el hígado, para ser excretado; y de este modo contribuyen al control de las enfermedades cardiovasculares. Además, las HDL pueden modular la respuesta inmune, por sus propiedades anti-inflamatorias, antioxidantes y anti-apoptóticas, entre otras. A nivel celular, las HDL pueden modificar las balsas lipídicas, las cuales son determinantes en la activación de la respuesta inmune frente a patógenos o agentes extraños. En algunas patologías como la sepsis, las HDL participan mediando la eliminación del lipopolisacárido (LPS) a través de su captura y posterior eliminación en el hígado; esto conlleva a una modulación negativa de la expresión del TLR4, principal receptor del LPS. También se ha reportado que las HDL modulan la respuesta inflamatoria a través de la regulación de la activación de la cascada del complemento y la expresión de pentraxina 3. Finalmente, la función y los niveles de las HDL se han encontrado particularmente alterados en algunas patologías infecciosas, ateroesclerosis y sepsis, lo que se ha asociado con el progreso o la severidad de la enfermedad.

SUMMARY The main function of high-density lipoproteins (HDL) is to transport the excess of cholesterol from tissues to the liver, where it is excreted, thus decreasing the risk of atherosclerotic plaques development and cardiovascular diseases establishment. Besides, HDL participates in different processes of the immune response, as its components have anti-inflammatory, anti-oxidative and antiapoptotic activities, among others. At cellular level, these lipoproteins have the ability to modify lipid rafts, critical micro-domains that participate in signaling pathways in response to pathogens. Likewise, it has been reported that HDL have a great impact in sepsis, as they eliminate the excess of LPS in blood and transport it to the liver for its elimination, and downregulate the expression of TLR4, main receptor of this molecule. Also, HDL can modulate humoral innate immune responses through regulating the activation of the complement pathway and the expression of pentraxin 3, resulting in the modulation of inflammatory processes. In fact, it has been reported that in several infectious diseases, atherosclerosis and sepsis, the level and function of HDL are altered, which associates with the progress of the diseases.

RESUMO As lipoproteínas de alta densidade (HDL) têm a fun- ção de transportar o excesso de colesterol desde os tecidos até ofígado para aqui ser excretado e dessa forma contribuem no controlo das doenças cardiovasculares. Além disso, as HDL podemmodular a resposta imune devido as suas propriedades anti-inflamatórias, antioxidantes e antiapopticas, entreoutras. Anívelcelular, asHDLpodemmodificar os rafts lipídicos, que são essências para a ativa- ção da resposta imune contra patógenos ouagentes estranhos. Nalgumas patologias como a septicemia, as HDL participam mediando a eliminação do lipopolissacarídeo (LPS) através da sua captura e posterior eliminação no fígado. Isto leva a uma modulação negativa da expressão de TLR4, orecetor principal do LPS. Também foi reportado que as HDL modulam a resposta inflamatória através da regulação da ativaçãoda cascata do sistema do complemento e a expressão de pentraxina 3. Por último, a função e os níveis das HDL têm sido especialmente encontrados alterados nalgumas doenças infeciosas, em aterosclerose e em septicemia, o qual esta associado aevolução ou a gravidade da doença.

Follicular CD8+ T Cells: Origin, Function and Importance during HIV Infection.

The lymphoid follicle is critical for the development of humoral immune responses. Cell circulation to this site is highly regulated by the differential expression of chemokine receptors. This feature contributes to the establishment of viral reservoirs in lymphoid follicles and the development of some types of malignancies that are able to evade immune surveillance, especially conventional CD8+ T cells. Interestingly, a subtype of CD8+ T cells located within the lymphoid follicle (follicular CD8+ T cells) was recently described; these cells have been proposed to play an important role in viral and tumor control, as well as to modulate humoral and T follicular helper cell responses. In this review, we summarize the knowledge on this novel CD8+ T cell population, its origin, function, and potential role in health and disease, in particular, in the context of the infection by the human immunodeficiency virus.

Role of Different Subpopulations of CD8+ T Cells during HIV Exposure and Infection.

During HIV infection, specific responses exhibited by CD8+ T cells are crucial to establish an early, effective, and sustained viral control, preventing severe immune alterations and organ dysfunction. Several CD8+ T cells subsets have been identified, exhibiting differences in terms of activation, functional profile, and ability to limit HIV replication. Some of the most important CD8+ T cells subsets associated with viral control, production of potent antiviral molecules, and strong polyfunctional responses include Th1-like cytokine pattern and Tc17 cells. In addition, the expression of specific activation markers has been also associated with a more effective response of CD8+ T cells, as evidenced in HLA-DR+ CD38- cells. CD8+ T cells in both, peripheral blood and gut mucosa, are particularly important in individuals with a resistant phenotype, including HIV-exposed seronegative individuals (HESNs), long-term non-progressors (LTNPs) and HIV-controllers. Although the role of CD8+ T cells has been extensively explored in the context of an established HIV-1 infection, the presence of HIV-specific cells with effector abilities and a defined functional profile in HESNs, remain poorly understood. Here, we reviewed studies carried out on different subpopulations of CD8+ T cells in relation with natural resistance to HIV infection and progression.

Higher Frequency of NK and CD4+ T-Cells in Mucosa and Potent Cytotoxic Response in HIV Controllers.

HIV infection induces immune alterations, mainly in gut mucosa, where the main target cells reside. However, the evolution of the infection is variable among infected individuals, as evidenced by HIV controllers who exhibit low or undetectable viral load in the absence of treatment. The aim of this study was to evaluate the frequency, phenotype and activity of T and NK cells in peripheral blood and gut mucosa in a cohort of Colombian HIV controllers. Blood and gut biopsies were included. The frequency and the activation status of T and NK cells were performed by flow cytometry. In addition, Gag-stimulated CD8+ T-cells and cytokine-stimulated NK cells were tested for cytotoxic activity. Finally, microbial translocation was measured by plasma lipopolysaccharide quantification. Compared with HIV-progressors, HIV controllers exhibited higher frequency of CD4+ T and NK cells, and lower expression of activation molecules in blood and mucosal immune cells, as well as lower microbial translocation. An increased production of molecules associated with cytotoxic activity of CD8+ T-cells in blood and mucosa and a higher percentage of polyfunctional CD8+ T cells in blood were also observed in HIV controllers. In addition, an increased activity of NK cells was observed in blood. These findings suggest that HIV controllers have a potent immune response, mainly mediated by cytotoxic cells that control HIV replication, which contribute to reducing alterations at the gut mucosa.

High Expression of Antiviral Proteins in Mucosa from Individuals Exhibiting Resistance to Human Immunodeficiency Virus.

BACKGROUND: Several soluble factors have been reported to have the capacity of inhibiting HIV replication at different steps of the virus life cycle, without eliminating infected cells and through enhancement of specific cellular mechanisms. Yet, it is unclear if these antiviral factors play a role in the protection from HIV infection or in the control of viral replication. Here we evaluated two cohorts: i) one of 58 HIV-exposed seronegative individuals (HESNs) who were compared with 59 healthy controls (HCs), and ii) another of 13 HIV-controllers who were compared with 20 HIV-progressors. Peripheral blood, oral and genital mucosa and gut-associated lymphoid tissue (GALT) samples were obtained to analyze the mRNA expression of ELAFIN, APOBEC3G, SAMHD1, TRIM5α, RNase 7 and SerpinA1 using real-time PCR. RESULTS: HESNs exhibited higher expression of all antiviral factors in peripheral blood mononuclear cells (PBMCs), oral or genital mucosa when compared with HCs. Furthermore, HIV-controllers exhibited higher levels of SerpinA1 in GALT. CONCLUSIONS: These findings suggest that the activity of these factors is compartmentalized and that these proteins have a predominant role depending on the tissue to avoid the infection, reduce the viral load and modulate the susceptibility to HIV infection.