Detection and quantification of poliovirus infection using FTIR spectroscopy and cell culture

Abstract

Background: In a globalized word, prevention of infectious diseases is a major challenge. Rapid detection of viable virus particles in water and other environmental samples is essential to public health risk assessment, homeland security and environmental protection. Current virus detection methods, especially assessing viral infectivity, are complex and time-consuming, making point-of-care detection a challenge. Faster, more sensitive, highly specific methods are needed to quantify potentially hazardous viral pathogens and to determine if suspected materials contain viable viral particles. Fourier transform infrared (FTIR) spectroscopy combined with cellular-based sensing, may offer a precise way to detect specific viruses. This approach utilizes infrared light to monitor changes in molecular components of cells by tracking changes in absorbance patterns produced following virus infection. In this work poliovirus (PV1) was used to evaluate the utility of FTIR spectroscopy with cell culture for rapid detection of infective virus particles.

Results: Buffalo green monkey kidney (BGMK) cells infected with different virus titers were studied at 1 - 12 hours post-infection (h.p.i.). A partial least squares (PLS) regression method was used to analyze and model cellular responses to different infection titers and times post-infection. The model performs best at 8 h.p.i., resulting in an estimated root mean square error of cross validation (RMSECV) of 17 plaque forming units (PFU)/ml when using low titers of infection of 10 and 100 PFU/ml. Higher titers, from 103 to 106 PFU/ml, could also be reliably detected.

Conclusions: This approach to poliovirus detection and quantification using FTIR spectroscopy and cell culture could potentially be extended to compare biochemical cell responses to infection with different viruses. This virus detection method could feasibly be adapted to an automated scheme for use in areas such as water safety monitoring and medical diagnostics.

Figure 1

Schematic representation of viral detection method using cell culture and FTIR spectroscopy (not to scale).

Figure 2

Microscopy of BGMK cells attached on ZnSe crystal (actin filaments, vinculin and nuclei) and bright field image of BGMK cells. a) Confocal image of BGMK cells adhered to a ZnSe crystal. Actin (red), Vinculin (green) and cell nuclei (blue) are shown. b) Bright microscopy image of BGMK cells adhered to a ZnSe crystal.

Figure 3

Poliovirus prediction models comparing the estimated PFU and predicted PFU at 1.5 - 8 h.p.i. Each point represent the predicted number of virus by the model for each sample exposed to different viral titers, × axis represent the estimated number of virus used.The green lines indicate a 1:1 regression model.

Figure 4

FTIR spectra showing changes in absorbance when cells are infected with poliovirus. Spectra in the wavelength region of 650 - 3600 cm^-1 show the absorbance of BGMK cells infected with different PV1 titers 10¹ - 10⁴ PFU/ml at 8 h.p.i. Uninfected cells served as a control. Nine regions were chosen by the PLS model as the most informative for detecting changes in cell components following virus infection. The different colors represent the mean spectra of the samples.

Figure 5

Regression analysis for cells infected with PV1 at 8 h.p.i. This model uses 7 latent variables. The regression uses a log scale and 0 - 10³ PFU/ml in the 650 - 1600 cm^-1 wavenumber region.

Figure 6

Average peak absorbance values compared to uninfected control for different virus titers at 8 h.p.i. Error bars show standard error. Note that 1654 cm^-1 was used to normalize the data and therefore shows no change.

Figure 7

Hours Post-Infection vs. Root Mean Square Error of Cross Validation. Graph shows the corresponding RMSECV for the experiments using 1.5, 4, 6 and 8 h.p.i. The lowest RMSECV value was achieved using an infection time of 8 h.p.i.,which corresponds to the best prediction model.