Intracellular bacterial infection and invariant NKT cells

Evaluation of the clinical diagnostic value of traditional inflammatory markers and novel biomarkers in intracellular bacterial bloodstream infections

OBJECTIVES

The clinical symptoms of the patients with intracellular bacterial bloodstream infections (Intra-bac BSIs) are atypical, and no early and accurate diagnostic biomarkers exist, which can easily lead to misdiagnosis, inappropriate and delayed treatment. Therefore, it is imperative to find novel biomarkers to help clinical diagnosis of Intra-bac BSIs. The present study was initiated to evaluate the diagnostic values of traditional inflammatory biomarkers (PCT, WBC and NEU% in identifying the patients with Intra-bac BSIs, and to further explore into the possibility of using suPAR and sCD14-ST as novel biomarkers for Intra-bac BSIs.

METHODS

A multi-center retrospective study was conducted in three teaching hospitals in Chongqing. A total of 146 cases with BSIs, including 73 cases with Intra-bac BSIs and 73 cases with extracellular bacterial BSIs (Extra-bac BSIs) were enrolled in the retrospective study. We then prospectively enrolled 34 patients with Intra-bac BSIs, 34 patients with Extra-bac BSIs, 34 patients with viral infection and with normal medical examination results as a control group for further detection of sCD14-ST and suPAR by ELISA.

RESULTS

PCT levels, WBC counts and NEU% in patients with Intra-bac BSIs were not increased or minimally increased, they were significantly lower than that with Extra-bac BSIs (P < 0.05), especially those with the Brucella bacterial BSIs, demonstrated a respective negative rate of 84% and 92% for PCT and WBC counts. In the prospective study, the levels of suPAR and sCD14-ST in both the Intra-bac BSIs and the Extra-bac BSIs groups were significantly higher than those in the viral infection group and normal control group (P < 0.05). The areas under the curve (AUC) of Intra-bac BSIs were 0.830 for suPAR, and 0.855 for sCD14-ST. The sensitivity, specificity, Youden's index for suPAR and sCD14-ST were respectively 76.5%, 88.2%, 0.647 and 94.1%, 64.7%, 0.588.

CONCLUSIONS

Our multi-center study demonstrated that while the traditional inflammatory markers such as PCT, WBC counts, NEU% could not be served as promising diagnostic markers for Intra-bac BSIs; CRP can help guide the diagnosis of Intra-bac BSIs; Both suPAR and sCD14-ST could be considered as novel diagnostic biomarkers for Intra-bac BSIs as they showed good diagnostic accuracies in Intra-bac BSIs, especially suPAR.

Co-immunization of plasmid DNA encoding IL-12 and IL-18 with Bacillus Calmette-Guérin vaccine against progressive tuberculosis

PURPOSE

Bacillus Calmette-Guérin (BCG) vaccine has widely been used to immunize against tuberculosis, but its protective efficacy is variable in adult pulmonary tuberculosis, while it is not efficiently protective against progressive infection of virulent Mycobacterium tuberculosis strains. In this study, the protective effects of plasmid DNA vaccine constructs encoding IL-12 or IL-18 with the BCG vaccine were evaluated against progressive infection of M. tuberculosis, using mouse aerosol challenge model.

MATERIALS AND METHODS

Plasmid DNA vaccine constructs encoding IL-12 or IL-18 were constructed and mice were immunized with the BCG vaccine or with IL-12 DNA or IL-18 DNA vaccine constructs together with the BCG vaccine.

RESULTS

The BCG vaccine induced high level of interferon gamma (IFN-γ) but co-immunization of IL-12 or IL-18 DNA vaccine constructs with the BCG vaccine induced significantly higher level of IFN-γ than a single BCG vaccine. The BCG vaccine was highly protective at early stage of M. tuberculosis infection, but its protective efficacy was reduced at later stage of infection. The co-immunization of IL-12 DNA vaccine constructs with the BCG vaccine was slightly more protective at early stage of infection and was significantly more protective at later stage infection than a single BCG vaccine.

CONCLUSION

Co-immunization of IL-12 DNA vaccine with the BCG vaccine induced more protective immunity and was more effective for protection against progressive infection of M. tuberculosis.