Determination of viremia and concentration of circulating nonstructural protein 1 in patients infected with dengue virus in Mexico

Abstract

Higher levels of viremia and circulating nonstructural protein 1 (NS1) have been associated with dengue disease severity. In this study, viremia and circulating NS1 levels were determined in 225 serum samples collected from patients in Mexico infected with dengue virus serotypes 1 and 2 (DENV-1 and DENV-2). Patients with dengue hemorrhagic fever (DHF) who were infected with DENV-1 showed higher levels of circulating NS1 than patients with dengue fever (DF) (P = 0.0175). Moreover, NS1 levels were higher in patients with primary infections with DENV-1 than in patient infected with DENV-2 (P < 0.0001) and in patients with primary infections with DENV-2 than in patients with secondary infections with DENV-2 (P = 0.0051). Unexpectedly, viremia levels were higher in patients with DF than in those with DHF infected with either DENV-1 or DENV-2 (P = 0.0019 and P = 0.001, respectively) and in patients with primary infections than those with secondary DENV-2 infections (P < 0.0001). Results indicate that levels of circulating NS1 vary according to the infecting serotype, immunologic status (primary or secondary infection), and dengue disease severity.

Figure 1.

Viremia levels in dengue infected patients according to clinical condition. Viremia (PFU eq/mL) in serum samples from patients with dengue fever (DF) or dengue hemorrhagic fever (DHF) infected with dengue virus 1 (DENV-1) or dengue 2 (DENV-2) were determined by using a singleplex real time reverse transcription–polymerase chain reaction. Box-and-whisker plots show median values (horizontal line in the box), 25–75% interquartile range (upper–lower limits of the box), 95% range of data (error bars), and outliers (black circles). P values were calculated by using the Mann-Whitney U test. Statistical significance was P ≤ 0.05. n = number of patients in each condition.

Figure 2.

Viremia levels in dengue-infected patients by days after fever onset. Viremia (PFU eq/mL) in serum samples from patients infected with dengue virus 1 (DENV-1) or dengue 2 (DENV-2) collected 0–2 days or 3–5 days after fever onset were determined by using a singleplex real time reverse transcription–polymerase chain reaction. Box-and-whisker plots show median values (horizontal line in the box), 25–75% interquartile range (upper–lower limits of the box), 95% range of data (error bars), and outliers (black circles). Statistical significance was P ≤ 0.05.

Figure 3.

Viremia levels in dengue virus serotype 2 (DENV-2) infected patients with primary or secondary infections. Viremia (plaque-forming units [PFU eq/mL]) in serum samples were determined by using a singleplex real time real time reverse transcription–polymerase chain reaction. Box-and-whisker plots show median values (horizontal line in the box), 25–75% interquartile range (upper–lower limits of the box), 95% range of data (error bars), and outliers (black circles). Statistical significance was P ≤ 0.05.

Figure 4.

Levels of circulating nonstructural protein 1 (NS1) in serum samples of dengue-infected patients according to clinical condition. Concentrations (ng/mL) of circulating NS1 in serum samples from patients with dengue fever (DF) or dengue hemorrhagic fever (DHF) infected with dengue virus 1 (DENV-1) or DENV-2 were determined by using a commercial enzyme-linked immunosorbent assay with modifications. Box-and-whisker plots show median values (horizontal line in the box), 25–75% interquartile range (upper–lower limits of the box), 95% range of data (error bars), and outliers (black circles). Statistical significance was P ≤ 0.05.

Figure 5.

Levels of circulating nonstructural protein 1 (NS1) in serum samples of dengue-infected patients by days after fever onset. Concentrations (ng/mL) of circulating NS1 in serum samples from patients infected with dengue 1 virus (DENV-1) or dengue 2 (DENV-2) collected 0–2 days or 3–5 days after fever onset were determined by using a commercial enzyme-linked immunosorbent assay with modifications. Box-and-whisker plots show median values (horizontal line in the box), 25–75% interquartile range (upper–lower limits of the box), 95% range of data (error bars), and outliers (black circles). Statistical significance was P ≤ 0.05.

Figure 6.

Levels of circulating nonstructural protein 1 (NS1) in serum samples of dengue virus serotype 2–infected patients with primary or secondary infections. Concentrations of circulating NS1 in serum samples were determined by using a commercial enzyme-linked immunosorbent assay with modifications. Box-and-whisker plots show median values (horizontal line in the box), 25–75% interquartile range (upper–lower limits of the box), 95% range of data (error bars), and outliers (black circles). Statistical significance was P ≤ 0.05.