The cookie settings on this website are set to 'allow all cookies' to give you the very best experience. Please click Accept Cookies to continue to use the site.

Mechanisms of HIV persistence during HAART

Mechanisms of HIV persistence during HAART

A calculated balance between Virus Replication, Cell Proliferation and Host Immune System

HIV Virus: Replication Cycle and Pathogenesis in absence of HAART

Human immunodeficiency virus (HIV) is transmitted through body fluids (blood, sexual fluids, and breast milk) and causes acquired immunodeficiency syndrome (AIDS). Current highly active antiretroviral therapy (HAART) effectively suppresses virus replication preventing disease progression and mortality. Virus eradication has still to be achieved and current efforts are working to design functional cures.

HIV infects T-cellmacrophages, dendritic cells, hematopoetic stem cells, and astrocytes (Iordanskiy et al., 2013). The contact between the viral and host membrane triggers the formation of a fusion pore responsible for the delivery of viral content into the cellular cytoplasm (Jiao et al., 2015), where the genomic HIV RNA is reverse transcribed into DNA, translocated into the nucleous and integrated into the host genome (Melikyan et al., 2000). Upon cells activation, viral genes are expressed and translocated into the cytoplasm where viral proteins are synthesized and assembled together to compose the immature viral particle (Freed, 2015). During and after release of the virus from the cells (budding), the viral protease enzyme promotes the maturation of the viral particle to become an infectious virion (Fig.1). Figure 1 HIV-1 cell cycle adapted from Pasternak AO et al 2013.

The course of HIV infection develops in three phases (Fig.2) and it is highly variable from patient to patient reflecting a complex interplay between virus replication and host immune responses. A first symptomatic acute phase is characterized by high plasma virus load, a sharp drop in CD4 T-cell counts, establishment of virus reservoirs, and the development of the anti HIV specific immune response (Douek et al., 2003). This is followed by a drop in viral load and a partial and temporary increase in CD4 T-cell numbers that marks the beginning of a long asymptomatic chronic phase during which the virus production and the CD4 T-cell number decline is slow. When CD4 T-cell count is less than 200 cells/L the last phase AIDS begins. Over the course of infection different HIV forms can be detected: plasma HIV RNA, total-integrated-unintegrated HIV DNA and HIV RNA in mononuclear peripheral cells (PBMC).

Figure 2; Natural course of HIV-1 infection and markers for HIV-1 detection. Red indicates markers used to detect HIV-1. Image adapted from https://www.slideshare.net/Positive_Force/life-cy... Nature Reviews Immunology.

HIV persistence during HAART: a terrifying reality

The introduction of HAART encouraged HIV cure hopes. In 1997, Perelson and colleagues demonstrated that HIV RNA concentration in plasma dropped by 99% in the first two weeks of HAART (Perelson et al., 1997) (Fig.3) and they estimated that 3.1 years of suppressive HAART would eliminate HIV.

Figure 3: Impact of HAART on HIV-1 reservoirs. Taken and adapted from The International AIDS society scientifc working group on HIV cure.

Sadly, in the same year, Chun TW (Chun et al., 1997) demonstrated the presence of a latent HIV reservoir in resting memory CD4 T-cells. Further studies generated a model by which a stable reservoir is established during the acute phase when infected activated CD4 T-cells rather than die as a result of HIV infection return to a resting state, maintaining HIV DNA integrated in their genome (Finzi et al., 1999). This cell population creates a favourable environment for viral persistence, including a pattern of gene expression that enables long-term survival, and the ability to respond to antigenic stimulation (Siliciano and Greene, 2011). Under these conditions, HIV can persist for long periods in a transcriptionally silent state that protects it from both immune responses and HAART. HIV persistence can be detected as RNA and cellular HIV DNA in blood even after long period of effective and suppressive HAART (Palmer et al., 2008).

Mechanisms of persistence

Cell Proliferation vs Ongoing Virus Replication

Plasma HIV RNA, intracellular HIV RNA and DNA forms can be measured in subjects receiving effective HAART (Ruggiero A. et al. 2017 https://www.futuremedicine.com/doi/abs/10.2217/fv... Whether detection equals ongoing virus replication is not still understood. Memory T-cells carry integrated HIV DNA and their proliferation provide effective expansion of the viral reservoir without replication (Bosque et al., 2011). Infected cells that undergo antigen-stimulation become activated and their proliferation can produce new viruses. When drugs are efficient, HIV replication should be immediately suppressed. Interestingly, two recent studies described that a subset of HAART-patients has virus production in lymphoid tissue where drug penetration or activity are suboptimal (Fletcher et al., 2014, Lorenzo-Redondo et al., 2016). In these body compartments, HIV proliferation is abundant in the absence of HAART and induces severe disruption of the lymphoid architecture which may favour the formation of sanctuary sites of viral reservoir (Schacker et al., 2006). HIV also invades the central nervous system (CNS) and HIV RNA levels remain detectable in the cerebrospinal fluid (CSF) despite HAART. Moreover, in studies where integrase inhibitor drugs were introduced in HAART, an increase of intracellular unintegrated HIV DNA in peripheral blood was observed (Buzon et al., 2010). These drugs block HIV integration following infection and the detection of unintegrated HIV DNA is an indirectly evidence of rounds of virus replication.

Of note, HIV itself can promote cell proliferation with consequent maintenance of the virus pool. Two independent studies demonstrated that HIV integration preferentially occurs within oncogenic genes that regulate cell proliferation (Maldarelli et al., 2014, Wagner et al., 2014).

Immune activation and HIV persistence: Friends or Foes?

HIV infection promotes chronic immune activation and inflammation, which improve but rarely resolve with HAART (Klatt et al., 2013). During this process, gut tissues are damaged enabling the translocation of gastrointestinal microbial products into the systemic circulation that in turn induce immune activation, establishing a self-perpetuating cycle (Shan and Siliciano, 2014).

How markers of immune activation correlate with parameters of HIV persistence during long-term suppressive therapy is poorly defined. Existing data is inconsistent reflecting complex bilateral interactions (Hatano et al., 2013, Chun et al., 2011, Cockerham et al., 2014, Ruggiero et al., 2015). Some studies in macaques showed that HIV-specific responses could reduce the size of the viral reservoir (Miller et al., 2005, Paiardini et al., 2005, Ploquin et al., 2016) providing a rational for a functional cure. Other data indicated that increased levels of immune activation are positively associated with levels of intracellular HIV DNA in peripheral blood (Ruggiero et al., 2015, Hatano et al., 2013, Cockerham et al., 2014) suggesting that T-cell activation in eradication strategies should be used with care. Furthermore, recent evidence showed lack of association between immune activation/inflammation and HIV persistence load (Gandhi et al., 2017) indicating the presence of other crucial players acting in this context.

Figure 4: HIV infection and chronic immune activation. adapted from Klatt et al 2013.

Conclusion and future direction

Current HAART is unable to eradicate HIV that persists in lymphoid organs, nervous system as well as in peripheral blood (Sturdevant et al., 2015, Palmer et al., 2008, Chun et al., 2008). The mechanisms that support virus persistence are still in debate and include both cell proliferation, and low levels of ongoing virus replication (Kiselinova et al., 2015, Fourati et al., 2014, Fletcher et al., 2014, Lorenzo-Redondo et al., 2016). Different factors may support virus persistence including the immune system, even though current studies are controversial. Current studies aims to expand our knowledge about HIV persistence in support of future eradication strategies design.

By Alessandra Ruggiero PhD candidate, University of Liverpool


References

BOSQUE, A., FAMIGLIETTI, M., WEYRICH, A. S., GOULSTON, C. & PLANELLES, V. 2011. Homeostatic proliferation fails to efficiently reactivate HIV-1 latently infected central memory CD4+ T cells. PLoS Pathog, 7, e1002288.

BUZON, M. J., MASSANELLA, M., LLIBRE, J. M., ESTEVE, A., DAHL, V., PUERTAS, M. C., GATELL, J. M., DOMINGO, P., PAREDES, R., SHARKEY, M., PALMER, S., STEVENSON, M., CLOTET, B., BLANCO, J. & MARTINEZ-PICADO, J. 2010. HIV-1 replication and immune dynamics are affected by raltegravir intensification of HAART-suppressed subjects. Nat Med, 16, 460-5.

CHUN, T. W., MURRAY, D., JUSTEMENT, J. S., HALLAHAN, C. W., MOIR, S., KOVACS, C. & FAUCI, A. S. 2011. Relationship between residual plasma viremia and the size of HIV proviral DNA reservoirs in infected individuals receiving effective antiretroviral therapy. J Infect Dis, 204, 135-8.

CHUN, T. W., NICKLE, D. C., JUSTEMENT, J. S., MEYERS, J. H., ROBY, G., HALLAHAN, C. W., KOTTILIL, S., MOIR, S., MICAN, J. M., MULLINS, J. I., WARD, D. J., KOVACS, J. A., MANNON, P. J. & FAUCI, A. S. 2008. Persistence of HIV in gut-associated lymphoid tissue despite long-term antiretroviral therapy. J Infect Dis, 197, 714-20.

CHUN, T. W., STUYVER, L., MIZELL, S. B., EHLER, L. A., MICAN, J. A., BASELER, M., LLOYD, A. L., NOWAK, M. A. & FAUCI, A. S. 1997. Presence of an inducible HIV-1 latent reservoir during highly active antiretroviral therapy. Proc Natl Acad Sci U S A, 94, 13193-7.

COCKERHAM, L. R., SILICIANO, J. D., SINCLAIR, E., O’DOHERTY, U., PALMER, S., YUKL, S. A., STRAIN, M. C., CHOMONT, N., HECHT, F. M., SILICIANO, R. F., RICHMAN, D. D. & DEEKS, S. G. 2014. CD4+ and CD8+ T cell activation are associated with HIV DNA in resting CD4+ T cells. PLoS One, 9, e110731.

DOUEK, D. C., PICKER, L. J. & KOUP, R. A. 2003. T cell dynamics in HIV-1 infection. Annu Rev Immunol, 21, 265-304.

FINZI, D., BLANKSON, J., SILICIANO, J. D., MARGOLICK, J. B., CHADWICK, K., PIERSON, T., SMITH, K., LISZIEWICZ, J., LORI, F., FLEXNER, C., QUINN, T. C., CHAISSON, R. E., ROSENBERG, E., WALKER, B., GANGE, S., GALLANT, J. & SILICIANO, R. F. 1999. Latent infection of CD4+ T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective combination therapy. Nat Med, 5, 512-7.

FLETCHER, C. V., STASKUS, K., WIETGREFE, S. W., ROTHENBERGER, M., REILLY, C., CHIPMAN, J. G., BEILMAN, G. J., KHORUTS, A., THORKELSON, A., SCHMIDT, T. E., ANDERSON, J., PERKEY, K., STEVENSON, M., PERELSON, A. S., DOUEK, D. C., HAASE, A. T. & SCHACKER, T. W. 2014. Persistent HIV-1 replication is associated with lower antiretroviral drug concentrations in lymphatic tissues. Proc Natl Acad Sci U S A, 111, 2307-12.

FOURATI, S., FLANDRE, P., CALIN, R., CARCELAIN, G., SOULIE, C., LAMBERT-NICLOT, S., MAIGA, A., AIT-ARKOUB, Z., TUBIANA, R., VALANTIN, M. A., AUTRAN, B., KATLAMA, C., CALVEZ, V. & MARCELIN, A. G. 2014. Factors associated with a low HIV reservoir in patients with prolonged suppressive antiretroviral therapy. J Antimicrob Chemother, 69, 753-6.

FREED, E. O. 2015. HIV-1 assembly, release and maturation. Nat Rev Microbiol, 13, 484-96.

GANDHI, R. T., MCMAHON, D. K., BOSCH, R. J., LALAMA, C. M., CYKTOR, J. C., MACATANGAY, B. J., RINALDO, C. R., RIDDLER, S. A., HOGG, E., GODFREY, C., COLLIER, A. C., ERON, J. J., MELLORS, J. W. & TEAM, A. A. 2017. Levels of HIV-1 persistence on antiretroviral therapy are not associated with markers of inflammation or activation. PLoS Pathog, 13, e1006285.

HATANO, H., JAIN, V., HUNT, P. W., LEE, T. H., SINCLAIR, E., DO, T. D., HOH, R., MARTIN, J. N., MCCUNE, J. M., HECHT, F., BUSCH, M. P. & DEEKS, S. G. 2013. Cell-based measures of viral persistence are associated with immune activation and programmed cell death protein 1 (PD-1)-expressing CD4+ T cells. J Infect Dis, 208, 50-6.

IORDANSKIY, S., SANTOS, S. & BUKRINSKY, M. 2013. Nature, nurture and HIV: The effect of producer cell on viral physiology. Virology, 443, 208-13.

JIAO, J., REBANE, A. A., MA, L., GAO, Y. & ZHANG, Y. 2015. Kinetically coupled folding of a single HIV-1 glycoprotein 41 complex in viral membrane fusion and inhibition. Proc Natl Acad Sci U S A, 112, E2855-64.

KISELINOVA, M., GERETTI, A. M., MALATINKOVA, E., VERVISCH, K., BELOUKAS, A., MESSIAEN, P., BONCZKOWSKI, P., TRYPSTEEN, W., CALLENS, S., VERHOFSTEDE, C., DE SPIEGELAERE, W. & VANDEKERCKHOVE, L. 2015. HIV-1 RNA and HIV-1 DNA persistence during suppressive ART with PI-based or nevirapine-based regimens. J Antimicrob Chemother, 70, 3311-6.

KLATT, N. R., CHOMONT, N., DOUEK, D. C. & DEEKS, S. G. 2013. Immune activation and HIV persistence: implications for curative approaches to HIV infection. Immunol Rev, 254, 326-42.

LORENZO-REDONDO, R., FRYER, H. R., BEDFORD, T., KIM, E. Y., ARCHER, J., POND, S. L. K., CHUNG, Y. S., PENUGONDA, S., CHIPMAN, J., FLETCHER, C. V., SCHACKER, T. W., MALIM, M. H., RAMBAUT, A., HAASE, A. T., MCLEAN, A. R. & WOLINSKY, S. M. 2016. Persistent HIV-1 replication maintains the tissue reservoir during therapy. Nature, 530, 51-56.

MALDARELLI, F., WU, X., SU, L., SIMONETTI, F. R., SHAO, W., HILL, S., SPINDLER, J., FERRIS, A. L., MELLORS, J. W., KEARNEY, M. F., COFFIN, J. M. & HUGHES, S. H. 2014. HIV latency. Specific HIV integration sites are linked to clonal expansion and persistence of infected cells. Science, 345, 179-83.

MELIKYAN, G. B., MARKOSYAN, R. M., HEMMATI, H., DELMEDICO, M. K., LAMBERT, D. M. & COHEN, F. S. 2000. Evidence that the transition of HIV-1 gp41 into a six-helix bundle, not the bundle configuration, induces membrane fusion. J Cell Biol, 151, 413-23.

MILLER, J. D., MASOPUST, D., WHERRY, E. J., KAECH, S., SILVESTRI, G. & AHMED, R. 2005. Differentiation of CD8 T cells in response to acute and chronic viral infections: implications for HIV vaccine development. Curr Drug Targets Infect Disord, 5, 121-9.

PAIARDINI, M., CERVASI, B., ALBRECHT, H., MUTHUKUMAR, A., DUNHAM, R., GORDON, S., RADZIEWICZ, H., PIEDIMONTE, G., MAGNANI, M., MONTRONI, M., KAECH, S. M., WEINTROB, A., ALTMAN, J. D., SODORA, D. L., FEINBERG, M. B. & SILVESTRI, G. 2005. Loss of CD127 expression defines an expansion of effector CD8+ T cells in HIV-infected individuals. J Immunol, 174, 2900-9.

PALMER, S., MALDARELLI, F., WIEGAND, A., BERNSTEIN, B., HANNA, G. J., BRUN, S. C., KEMPF, D. J., MELLORS, J. W., COFFIN, J. M. & KING, M. S. 2008. Low-level viremia persists for at least 7 years in patients on suppressive antiretroviral therapy. Proc Natl Acad Sci U S A, 105, 3879-84.

PERELSON, A. S., ESSUNGER, P., CAO, Y., VESANEN, M., HURLEY, A., SAKSELA, K., MARKOWITZ, M. & HO, D. D. 1997. Decay characteristics of HIV-1-infected compartments during combination therapy. Nature, 387, 188-91.

PLOQUIN, M. J., SILVESTRI, G. & MULLER-TRUTWIN, M. 2016. Immune activation in HIV infection: what can the natural hosts of simian immunodeficiency virus teach us? Curr Opin HIV AIDS, 11, 201-8.

RUGGIERO, A., DE SPIEGELAERE, W., COZZI-LEPRI, A., KISELINOVA, M., POLLAKIS, G., BELOUKAS, A., VANDEKERCKHOVE, L., STRAIN, M., RICHMAN, D., PHILLIPS, A., GERETTI, A. M. & GROUP, E. S. 2015. During Stably Suppressive Antiretroviral Therapy Integrated HIV-1 DNA Load in Peripheral Blood is Associated with the Frequency of CD8 Cells Expressing HLA-DR/DP/DQ. EBioMedicine, 2, 1153-9.

SCHACKER, T. W., BRENCHLEY, J. M., BEILMAN, G. J., REILLY, C., PAMBUCCIAN, S. E., TAYLOR, J., SKARDA, D., LARSON, M., DOUEK, D. C. & HAASE, A. T. 2006. Lymphatic tissue fibrosis is associated with reduced numbers of naive CD4+ T cells in human immunodeficiency virus type 1 infection. Clin Vaccine Immunol, 13, 556-60.

SHAN, L. & SILICIANO, R. F. 2014. Unraveling the relationship between microbial translocation and systemic immune activation in HIV infection. J Clin Invest, 124, 2368-71.

SILICIANO, R. F. & GREENE, W. C. 2011. HIV latency. Cold Spring Harb Perspect Med, 1, a007096.

STURDEVANT, C. B., JOSEPH, S. B., SCHNELL, G., PRICE, R. W., SWANSTROM, R. & SPUDICH, S. 2015. Compartmentalized replication of R5 T cell-tropic HIV-1 in the central nervous system early in the course of infection. PLoS Pathog, 11, e1004720.

WAGNER, T. A., MCLAUGHLIN, S., GARG, K., CHEUNG, C. Y., LARSEN, B. B., STYRCHAK, S., HUANG, H. C., EDLEFSEN, P. T., MULLINS, J. I. & FRENKEL, L. M. 2014. HIV latency. Proliferation of cells with HIV integrated into cancer genes contributes to persistent infection. Science, 345, 570-3.

6th Nov 2018 Alessandra Ruggiero PhD candidate, University of Liverpool

Recent Posts