Research ArticleEPIDEMIOLOGY

Rapid, noninvasive detection of Zika virus in Aedes aegypti mosquitoes by near-infrared spectroscopy

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Science Advances  23 May 2018:
Vol. 4, no. 5, eaat0496
DOI: 10.1126/sciadv.aat0496

Figures

  • Fig. 1 NIRS differentiation of ZIKV-infected and uninfected A. aegypti mosquitoes using leave-one-out cross-validation analysis.

    Shown are the predictions of the leave-one-out cross-validation analysis carried out on a subset of mosquitoes in cohort 1 (n = 120) at 4 and 7 dpi. Each circle represents an individual mosquito; infection status confirmed by RT-qPCR is indicated by solid (infected) or empty (uninfected) circles. Red lines indicate the mean prediction value for each group. The vertical axis indicates infection status as predicted by NIRS, with the dotted line indicating the classification cutoff point. Infected mosquitoes shown below the dotted line and uninfected mosquitoes shown above the dotted line were falsely predicted.

  • Fig. 2 NIRS predictions of ZIKV infection in heads/thoraces and abdomens of A. aegypti mosquitoes on a blind data set.

    (A) Predicted infections at 4, 7, and 10 dpi in heads/thoraces for the subset of cohort 1 (n = 155) that were excluded from the model and all cohort 2 samples (n = 412). (B) Predictions for abdomens from cohort 2 samples (n = 412). Each circle represents an individual mosquito; infection status confirmed by RT-qPCR is indicated by solid (infected) or empty (uninfected) circles. Red lines indicate the mean prediction value for each group. The vertical axis indicates infection status as predicted by NIRS, with the dotted line indicating the classification cutoff point. Infected mosquitoes shown below the dotted line and uninfected mosquitoes shown above the dotted line were falsely predicted.

  • Fig. 3 Average NIR spectra in the 350- to 2500-nm region from heads/thoraces of ZIKV-infected (red) and uninfected (blue) A. aegypti mosquitoes.
  • Fig. 4 Regression coefficients using eight factors in the PLS model based on the NIR spectra in the 700- to 2350-nm region for differentiating ZIKV-infected from uninfected A. aegypti.
  • Fig. 5 ZIKV load in A. aegypti cohorts at 4, 7, and 10 dpi with a Brazilian ZIKV isolate (BRPE243/2015) provided at a titer of 1.9 × 106 PFU/ml.

    Viral copies were determined by RT-qPCR in individual mosquito homogenates with a standard curve of a seven-point dilution series (102 to 108 copies/ml) of in vitro transcribed ZIKV RNA. The number of infected mosquitoes followed by the infection rate (in parentheses) is shown for each condition.

Tables

  • Table 1 Sensitivities and specificities of the ZIKV training model.

    Predicted sensitivity [true positive rate (TPR)] and specificity (SPC) of NIRS are shown for cohort 1 samples used in the training set at 4 dpi (n = 61) and 7 dpi (n = 59) and cohort 1 samples that were excluded from the training set (prevalidation) at 4 dpi (n = 65) and 7 dpi (n = 90). Predicted sensitivity and specificity of NIRS are shown for heads/thoraces of cohort 2 samples at 4 dpi (n = 136), 7 dpi (n = 138), and 10 dpi (n = 138) and for abdomens at 4 dpi (n = 136), 7 dpi (n = 138), and 10 dpi (n = 138).

    Experiment set4 dpi7 dpi10 dpi
    %TPR%SPC%TPR%SPC%TPR%SPC
    Cohort 1. Training set83.396.893.596.4
    Cohort 1. Prevalidation set100.094.1100.0100.0
    Cohort 2. Test set
    (heads/thoraces)
    98.798.3100.098.3100.086.7
    Cohort 2. Test set (abdomens)98.785.096.280.097.468.3