Monocytes in chronic HIV-1 infection : changes in phenotypic marker expression and their relationship with immune activation

Poovan, Karmistha (2014-12)

Thesis (MScMedSc) –Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: HIV-infection is characterized by depletion of CD4+ T-cells from the gut-associated lymphoid tissue (GALT) which causes irreparable gastrointestinal tract damage and subsequent microbial translocation of bacterial products such as lipopolysaccharide (LPS), a component of Gram-negative bacteria, into systemic circulation. HIV infection also affects the functions and relative population sizes of various immune cells, such as monocytes. Monocytes are important innate immune cells as they are often the first cells recruited to sites of infection and inflammation. They then either promote inflammatory processes; elicit adaptive immune responses, through their antigen presenting ability; aid in pathogen and debris clearance or aid in damage repair. This cross-sectional study investigated functional changes to monocytes and monocyte subsets (CD14+CD16- and CD14+CD16+) in HIV+, treatment naïve individuals and healthy uninfected controls, using whole blood assays and isolated monocytes. A number of chemokine receptors associated with function and homing, and specific gut-homing receptors, were investigated. Monocyte activation, apoptotic potential and intracellular monocyte cytokine production were also investigated. All markers were evaluated using multi-parameter flow cytometry. Monocyte responsiveness to in vitro LPS stimulation and expression of the afore-mentioned chemokine receptors to viral load, CD4+ count and CD38/8 T-cell expression was also assessed. During HIV-infection monocytes appeared primed to exit systemic circulation and migrate towards the gut, as seen through elevated CD62-L (p < 0.005) and CCR7 (p < 0.005), whereas the CD14+CD16+ subset was increased (p = 0.0461) and exhibited a higher activation status through increased CD69 expression (p < 0.005) compared to the CD14+CD16- subset. An interesting observation was the significantly increased IL-10 production by the CD14+CD16+ subset (p < 0.005). An elevated CCR5 expression in total monocytes (p < 0.005) was also seen. After LPS stimulation, the HIV+ group displayed unique and significant percentage increases in the total monocyte population. The findings of the current study suggest that monocyte functionality may be retained during HIV-infection and that CD14+CD16+ monocytes play a vital role during HIV-infection evidenced by their preferential expansion and priming for GALT migration. The production of IL-10 by this subset further highlights their importance and emphasizes the need for future studies on the role of these cells in chronic stable HIV-1 infection and whilst disease progresses.

AFRIKAANSE OPSOMMING: MIV-infeksie word gekenmerk deur die uitputting van CD4+ T-selle, veral uit die derm-verwante limfweefsel (GALT). Dit veroorsaak onherstelbare skade aan die spysverteringskanaal en die daaropvolgende mikrobiese translokasie van bakteriële produkte soos LPS, „n komponent van Gram-negatiewe bakterieë, wat gaan binne sistemiese sirkulasie. MIV-infeksie beinvloed die funksies en relatiewe bevolkingsgrootte van verskeie immuun selle, insluitend monosiete. Monosiete is belangrike ingebore immuun selle en is dikwels die eerste selle wat gewerf word na areas van infeksie en inflammasie. Monosiete kan inflammatoriese prosesse bevorder of aanpabare immuunstelsel reaksies ontlok deur middel van hul antigeen aanbiedings vermoë of help met patogeen en puin klaring en skade herstel. In hierdie deursnee-studie het ons veranderinge aan monosiete (CD14+CD16+ en CD14+CD16-) ondersoek in MIV+ behandelde naïef individue en gesonde onbesmette kontroles, deur die gebruik van hele bloed toetse en geïsoleerde monosiete. 'n Aantal chemokine reseptore, wat verband hou met homing en funksie was ondersoek in toevoeging tot spesifieke derm-homing reseptore. Monosiet aktivering, apoptese potensiaal en intrasellulêre monosiet sitokien produksie was ook ondersoek. Alle merkers is ondersoek deur multi-parameter vloeisitometrie. Die beoordeel reaksies van monosiete na in vitro LPS stimulasie en die uitdrukking van die merkers met merkers van algemene immuun aktivering en MIV-siekte patogenese was ook ondersoek. CD14+CD16+ monosiete was gedurende MIV-infeksie verhoog (p-waarde = 0.0461). Daar was 'n hoër algehele monosiet uitdrukking van verskeie chemokine merkers soos CD69 (p-waarde < 0.005) uitdrukking; CD62-L (p-waarde < 0.005), en CCR7 (p-waarde < 0.005) uitdrukking in die CD14+CD16+ subgroep. Daar was ook „n toename in IL-10 produksie, veral in die CD14+CD16+ subgroep (p-waarde < 0.005). Hoewel baie funksionele merker reaksies dieselfde was, het die MIV+ groep „n unieke en beduidende persentasie verhooging in die totale monosiet bevolking getoon. Ons algehele bevindinge dui op 'n voorkeur uitbreiding van CD14+CD16+ monosiete tydens MIV-infeksie. Die CD14+CD16+ monosiet subgroep blyk ook bevoordeel word met betrekking tot voorbereiding vir migrasie na limfknope en die GALT. Die toename in geaktiveer de CD14+CD16+ monosiete op siekte webwerwe is waarskynlik 'n groot bydraende faktor tot aanhoudende immuun aktivering wat op sy beurt virale replikasie bevorder. Hierdie resultate beklemtoon die behoefte om die rol van hierdie selle en in veral die CD14+CD16+ subgroep, in kroniese stabiele MIV-1 infeksie verder te studeer en terwyl siekte bevorder.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/95914
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