Illuminating Host-Parasite Interaction at the Cellular and Subcellular Levels with Infrared Microspectroscopy.

Hany M Elsheikha,Francesca Winterton,Carl W Stevenson,Paul W Denny,Alaa T Al-Sandaqchi,John G M Mina,Ka Lung Andrew Chan,Mohammad S R Harun,Gianfelice Cinque,Nashwa A Elsaied,Ali Altharawi,William Macnaughtan

doi:10.3390/cells11050811

Abstract

Toxoplasma gondii (T. gondii) is an opportunistic protozoan that can cause brain infection and other serious health consequences in immuno-compromised individuals. This parasite has a remarkable ability to cross biological barriers and exploit the host cell microenvironment to support its own survival and growth. Recent advances in label-free spectroscopic imaging techniques have made it possible to study biological systems at a high spatial resolution. In this study, we used conventional Fourier-transform infrared (FTIR) microspectroscopy and synchrotron-based FTIR microspectroscopy to analyze the chemical changes that are associated with infection of human brain microvascular endothelial cells (hBMECs) by T. gondii (RH) tachyzoites. Both FTIR microspectroscopic methods showed utility in revealing the chemical alterations in the infected hBMECs. Using a ZnS hemisphere device, to increase the numerical aperture, and the synchrotron source to increase the brightness, we obtained spatially resolved spectra from within a single cell. The spectra extracted from the nucleus and cytosol containing the tachyzoites were clearly distinguished. RNA sequencing analysis of T. gondii-infected and uninfected hBMECs revealed significant changes in the expression of host cell genes and pathways in response to T. gondii infection. These FTIR spectroscopic and transcriptomic findings provide significant insight into the molecular changes that occur in hBMECs during T. gondii infection.

Highlights

One-third of the world’s human population are chronically infected by the intracellular protozoan parasite Toxoplasma gondii [1]
These results are based on the averaged Fourier-transform infrared (FTIR) absorbance from the individual human brain microvascular endothelial cells (hBMECs) and it was not possible to reveal subcellular differences between the infected and the control cells
We investigated the general dynamics of chemical changes that accompany T. gondii infection of hBMECs using conventional FTIR micro spectroscopic analysis, which revealed no significant differences between infected and control cells at 24 hpi or 48 hpi in PC1

Summary

Introduction

One-third of the world’s human population are chronically infected by the intracellular protozoan parasite Toxoplasma gondii [1]. This protozoan can cause serious illness, especially in immunocompromised patients and in pregnant women [2,3]. How a cell responds to T. gondii infection and, in turn, how T. gondii attempts to moderate that response have been a topic of increasing interest. One such response of the parasite is to alter the host cell metabolism [4]. Various analytical approaches have been used to characterize the metabolic changes that occur in host cells and tissues in response to T. gondii infection. Nuclear magnetic resonance (NMR) was used to study the metabolic changes in human cerebrovascular endothelial cells during T. gondii infection [7]

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