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Abstract
Purpose: Radiosensitivity in relation to the human immunodeficiency virus (HIV) status is important in South Africa as the prevalence of HIV infections is high. In this study the in vitro chromosomal radiosensitivity of HIV positive individuals was investigated and compared with that of HIV negative individuals.
Materials and methods: Blood samples from 59 HIV positive and 39 HIV negative individuals were exposed in vitro to doses of 6MV X-rays ranging from 1–4 Gy. Chromosomal radiosensitivity was assessed with the micronucleus assay. Micronuclei are a measure of chromosomal damage and were quantified in at least 500 binucleated lymphoblasts (BN) per sample. Un-irradiated control samples from each donor were also analysed.
Results: In 47% of HIV positive individuals difficulties with cell stimulation by adding phytohaemagglutinin (PHA) to blood cultures were noticed which resulted in insufficient yield of BN for microscopic analysis. Micronuclei frequencies were consistently higher in irradiated lymphocytes obtained from HIV positive individuals compared to that observed in cells from HIV negative donors. Data for both groups were fitted to the linear-quadratic equation Y = αD + βD2 where Y is the number of micronuclei in 500 binucleated cells and D is the dose in Gy. The fitted parameters for respectively HIV positive and HIV negative lymphocytes are α = 80.17 Gy−1, β = 14 Gy−2 and α = 54.5 Gy−1, β = 16.2 Gy−2. The confidence ellipses of these parameters are separated indicating that the increase in radiosensitivity is statistically significant.
Conclusion: T-lymphocytes of HIV infected individuals were considerably more sensitive to X-rays compared to that of HIV negative donors. This may have implications for normal tissue tolerance during radiotherapy as well as for the radiological health of radiation workers.
Acknowledgements
The work was supported by National Research Foundation - iThemba LABS (Laboratory for Accelerator Based Sciences), South Africa, a grant of the Research Foundation Flanders (FWO, No 1.5.080.08) and a ‘VLIR Own Initiative Programme’ between Belgium and South Africa (ZEIN2005PR309). Ethical clearance was received from WITS University, South Africa (M060220). The authors wish to thank all donors who participated in this study. We also thank Dr MacPhail for the assistance in sample collection and D. Lawrie and L. Moreira for the technical assistance with the Flow Cytometer.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.