Infrared spectral changes identified during different stages of herpes viruses infection in vitro

Microscopic Fourier transform infrared spectroscopy (FTIR) which is based on the characteristic molecular vibrational spectra of cells was previously applied for the identification of various biological samples. In the present study, FTIR spectroscopy was used for the characterization of different stages during the development of herpes viruses infection. Vero cells in culture were infected with high and low doses of different herpes viruses [herpes simplex virus types 1 and 2 (HSV-1, -2) or varicella-zoster virus (VZV)], and cellular changes were observed by optical and electron microscopy and analyzed by FTIR microscopy at different periods of time post-infection. Specific different spectral changes were observed at various stages of the viral infection development. The spectral intensity in the 1220-1260 cm(-1) region (mainly attributed to phosphate levels) was considerably increased in all infected cells compared to normal uninfected cells during the early stages of the viral infection development. However, at the late stages of the viral infection development (when all the cells in the infected culture lost their spindle shape and became circular) the spectral intensities in this region significantly decreased in the infected compared to the control cells. In addition, the peak at 1023 cm(-1), attributed to carbohydrates, almost fully disappeared at early stages of the viral infection development, whereas at late stages of the infection it raised to an equivalent or higher level than that of the uninfected control cells. These results support the potential of developing FTIR microspectroscopy as a simple, reagent free method for the early detection and accurate differentiation of different stages during the development of herpes virus infection.