Culture Cell Block Controls as a Tool to the Biomolecular Diagnosis of Infectious Diseases

CISH and IHC for the Simultaneous Detection of ZIKV RNA and Antigens in Formalin-Fixed Paraffin-Embedded Cell Blocks and Tissues

Zika virus is an arthropod-borne virus that has recently emerged as a significant public health emergency due to its association with congenital malformations. Serological and molecular tests are typically used to confirm Zika virus infection. These methods, however, have limitations when the interest is in localizing the virus within the tissue and identifying the specific cell types involved in viral dissemination. Chromogenic in situ hybridization (CISH) and immunohistochemistry (IHC) are common histological techniques used for intracellular localization of RNA and protein expression, respectively. The combined use of CISH and IHC is important to obtain information about RNA replication and the location of infected target cells involved in Zika virus neuropathogenesis. There are no reports, however, of detailed procedures for the simultaneous detection of Zika virus RNA and proteins in formalin-fixed paraffin-embedded (FFPE) samples. Furthermore, the chromogenic detection methods for Zika virus RNA published thus far use expensive commercial kits, limiting their widespread use. As an alternative, we describe here a detailed and cost-effective step-by-step procedure for the simultaneous detection of Zika virus RNA and proteins in FFPE samples. First, we describe how to synthesize and purify homemade RNA probes conjugated with digoxygenin. Then, we outline the steps to perform the chromogenic detection of Zika virus RNA using these probes, and how to combine this technique with the immunodetection of viral antigens. To illustrate the entire workflow, we use FFPE samples derived from infected Vero cells as well as from human and mouse brain tissues. These methods are highly adaptable and can be used to study Zika virus or even other viruses of public health relevance, providing an optimal and economical alternative for laboratories with limited resources. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Synthesis of RNA probes conjugated with digoxigenin (DIG) Basic Protocol 2: Simultaneous detection of ZIKV RNA and proteins in FFPE cell blocks and tissues.

Surveillance of hemorrhagic fever and/or neuroinvasive disease: challenges of diagnosis

OBJECTIVE

To evaluate the performance of post mortem laboratory analysis in identifying the causes of hemorrhagic fever and/or neuroinvasive disease in deaths by arbovirus infection.

METHODS

Retrospective cross-sectional study based on the differential analysis and final outcome obtained in patients whose samples underwent laboratory testing for arboviruses at the Pathology Center of the Adolfo Lutz Institute, in São Paulo, Brazil.

RESULTS

Of the 1355 adults clinically diagnosed with hemorrhagic fever and/or neuroinvasive disease, the most commonly attributed cause of death and the most common final outcome was dengue fever. Almost half of the samples tested negative on all laboratory tests conducted.

CONCLUSION

The failure to identify the causative agent in a great number of cases highlights a gap in the diagnosis of deaths of unknown etiology. Additional immunohistochemical and molecular assessments need to be added to the post-mortem protocol if all laboratory evaluations performed fail to identify a causative agent. While part of our findings may be due to technical issues related to sample fixation, better information availability when making the initial diagnosis is crucial. Including molecular approaches might lead to a significant advancement in diagnostic accuracy.

Concurrent yellow fever and pulmonary aspergillosis due to Aspergillus fumigatus in a free-ranging howler monkey (Alouatta sp)

Herein, we describe a unique case of concomitant angioinvasive pulmonary aspergillosis due to Aspergillus fumigatus and yellow fever in a free-ranging howler monkey (Alouatta sp). Lung samples were negative for influenza viruses A and B.