Transformation of monocytes to adherent cells by combination antiretroviral treatment

C. Mafuva, W. A. Morgan. Medicines Research Group, University of East London, London, UNITED KINGDOM.

Introduction: The increased use of highly active antiretroviral therapy (HAART) has resulted in a dramatic increased survival of HIV-infected individuals. A downside of the success of antiretroviral therapy (ART) is the premature onset and increased risk of certain inflammatory age-related diseases associated with low levels of chronic immune activation. Such activation is thought to contribute to what is described as serious non-AIDS events (SNAEs) [1]. HAART entails combining two nucleoside reverse transcriptase inhibitors (NRTIs) with either one or two protease inhibitors (PIs) or non-nucleoside reverse transcriptase inhibitors (NNRTIs), in this study usually nevirapine (NVP) [2].

Method: In an attempt to better understand the impact of HAART on the immune system, U937 cells (a histolytic lymphoma monocyte line) were exposed to a range of drugs used for HAART therapy and differentiation to macrophage morphology assessed. In 24 well plates, cells were treated with single and combination drugs at a final concentration of 50µg/ml of each drug and incubated at 37oC and 5% CO2 for 72hrs (n=3 in all treatments). Single drug antiretroviral treatment was with abacavir sulfate (ABC), zidovudine (ZDV), lamivudine (3TC), stavudine (dT4) and nevirapine (NVP). The following antiretroviral combinations were considered: ABC+3TC, ZDV+3TC, ABC+ZDV+3TC, ZDV+3TC+NVP and d4T+3TC+NVP. Following 72 hours of exposure to the antiretroviral drugs, the percentage of adherent cells as a fraction of total live cell count was assessed.

Results: Adherence of single drug treatment was as follows: 3.25% for ABC, 86.03% for ZDV, 21.05% for 3TC, 47.22% for stavudine dT4 and 12.50% for nevirapine NVP. The effect of treatment with combination antiretroviral drugs was as follows: 13.51% for ABC+3TC, 7.89% for ZDV+3TC, 40.11% for ABC+ZDV+3TC, 42.07% for ZDV+3TC+NVP and 39.89% d4T+3TC+NVP. Distinct morphological changes including armourphous and granular structure coupled with increased cell size and adherence were predominantly observed for ZDV and triple antiretroviral drug combination treated cells.

Conclusion: These initial observations indicate that HAART is capable of stimulating the differention of monocyte (pre-macrophage) into cells with “macrophages-like” morphological characteristics. If replicated in vivo this could go some way to explaining the SNAEs observed with long term highly active antiretroviral treatment.

References

1. Hsu et al. (2013). AIDS Research and Therapy: 10:29 Availble from: http://aidsrestherapy.biomedcentral.com/articles/10.1186/1742-6405-10-29

2. http://www.who.int/topics/antiretroviral_therapy/en/