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A man in his 70s with a complex medical history, including cadaveric renal transplant, presented with recurrent urinary tract infections. Investigation revealed recurrent urinary pathogens, includingEnterobacter cloacaeand persistent BK viruria. Cystoscopy revealed a pedunculated mass in the right posterior–lateral wall, inferior to the transplant urethral orifice, and biopsy of this mass showed invasive small cell carcinoma with a prominent adenocarcinoma component. The tumour was treated with complete transurethral resection followed by carboplatin, etoposide and radiation. Laboratory analysis of biopsied samples showed immunostaining and molecular evidence of BK virus DNA in the cancer cells. Follow-up cystoscopies have shown no recurrence of the cancer.

Summary Background Since August, 2019, US public health officials have been investigating a national outbreak of e-cigarette, or vaping, product use-associated lung injury (EVALI). A spectrum of histological patterns consistent with acute to subacute lung injury has been seen in biopsies; however, autopsy findings have not been systematically characterised. We describe the pathological findings in autopsy and biopsy tissues submitted to the US Centers for Disease Control and Prevention (CDC) for the evaluation of suspected EVALI. Methods Between Aug 1, 2019, and Nov 30, 2019, we examined lung biopsy (n=10 individuals) and autopsy (n=13 individuals) tissue samples received by the CDC, submitted by 16 US states, from individuals with: a history of e-cigarette, or vaping, product use; respiratory, gastrointestinal, or constitutional symptoms; and either pulmonary infiltrates or opacities on chest imaging, or sudden death from an undetermined cause. We also reviewed medical records, evaluated histopathology, and performed infectious disease testing when indicated by histopathology and clinical history. Findings 21 cases met surveillance case definitions for EVALI, with a further two cases of clinically suspected EVALI evaluated. All ten lung biopsies showed histological evidence of acute to subacute lung injury, including diffuse alveolar damage or organising pneumonia. These patterns were also seen in nine of 13 (69%) autopsy cases, most frequently diffuse alveolar damage (eight autopsies), but also acute and organising fibrinous pneumonia (one autopsy). Additional pulmonary pathology not necessarily consistent with EVALI was seen in the remaining autopsies, including bronchopneumonia, bronchoaspiration, and chronic interstitial lung disease. Three of the five autopsy cases with no evidence of, or a plausible alternative cause for acute lung injury, had been classified as confirmed or probable EVALI according to surveillance case definitions. Interpretation Acute to subacute lung injury patterns were seen in all ten biopsies and most autopsy lung tissues from individuals with suspected EVALI. Acute to subacute lung injury can have numerous causes; however, if it is identified in an individual with a history of e-cigarette, or vaping, product use, and no alternative cause is apparent, a diagnosis of EVALI should be strongly considered. A review of autopsy tissue pathology in suspected EVALI deaths can also identify alternative diagnoses, which can enhance the specificity of public health surveillance efforts. Funding US Centers for Disease Control and Prevention.

An ongoing pandemic of coronavirus disease (COVID-19) is caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Characterization of the histopathology and cellular localization of SARS-CoV-2 in the tissues of patients with fatal COVID-19 is critical to further understand its pathogenesis and transmission and for public health prevention measures. We report clinicopathologic, immunohistochemical, and electron microscopic findings in tissues from 8 fatal laboratory-confirmed cases of SARS-CoV-2 infection in the United States. All cases except 1 were in residents of long-term care facilities. In these patients, SARS-CoV-2 infected epithelium of the upper and lower airways with diffuse alveolar damage as the predominant pulmonary pathology. SARS-CoV-2 was detectable by immunohistochemistry and electron microscopy in conducting airways, pneumocytes, alveolar macrophages, and a hilar lymph node but was not identified in other extrapulmonary tissues. Respiratory viral co-infections were identified in 3 cases; 3 cases had evidence of bacterial co-infection.

Background Death in patients with chikungunya is rare and has been associated with encephalitis, hemorrhage, and septic shock. We describe clinical, histologic, and immunohistochemical findings in individuals who died following chikungunya virus (CHIKV) infection. Methods We identified individuals who died in Puerto Rico during 2014 following an acute illness and had CHIKV RNA detected by reverse transcriptase–polymerase chain reaction in a pre- or postmortem blood or tissue specimen. We performed histopathology and immunohistochemistry (IHC) for CHIKV antigen on tissue specimens and collected medical data via record review and family interviews. Results Thirty CHIKV-infected fatal cases were identified (0.8/100 000 population). The median age was 61 years (range: 6 days–86 years), and 19 (63%) were male. Death occurred a median of 4 days (range: 1–29) after illness onset. Nearly all (93%) had at least 1 comorbidity, most frequently hypertension, diabetes, or obesity. Nine had severe comorbidities (eg, chronic heart or kidney disease, sickle cell anemia) or coinfection (eg, leptospirosis). Among 24 fatal cases with tissue specimens, 11 (46%) were positive by IHC. CHIKV antigen was most frequently detected in mesenchymal tissues and mononuclear cells including tissue macrophages, blood mononuclear cells, splenic follicular dendritic cells, and Kupffer cells. Common histopathologic findings were intra-alveolar hemorrhage and edema in the lung, chronic or acute tenosynovitis, and increased immunoblasts in the spleen. CHIKV infection likely caused fatal septic shock in 2 patients. Conclusions Evaluation of tissue specimens provided insights into the pathogenesis of CHIKV, which may rarely result in septic shock and other severe manifestations.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes respiratory disease in mink similar to human COVID-19. We characterized the pathological findings in 72 mink from US farms with SARS-CoV-2 outbreaks, localized SARS-CoV-2 and its host cellular receptor angiotensin-converting enzyme 2 (ACE2) in mink respiratory tissues, and evaluated the utility of various test methods and specimens for SARS-CoV-2 detection in necropsy tissues. Of SARS-CoV-2-positive animals found dead, 74% had bronchiolitis and diffuse alveolar damage (DAD). Of euthanized SARS-CoV-2-positive animals, 72% had only mild interstitial pneumonia or minimal nonspecific lung changes (congestion, edema, macrophages); similar findings were seen in SARS-CoV-2-negative animals. Suppurative rhinitis, lymphocytic perivascular inflammation in the lungs, and lymphocytic infiltrates in other tissues were common in both SARS-CoV-2-positive and SARS-CoV-2-negative animals. In formalin-fixed paraffin-embedded (FFPE) upper respiratory tract (URT) specimens, conventional reverse transcription-polymerase chain reaction (cRT-PCR) was more sensitive than in situ hybridization (ISH) or immunohistochemistry (IHC) for detection of SARS-CoV-2. FFPE lung specimens yielded less detection of virus than FFPE URT specimens by all test methods. By IHC and ISH, virus localized extensively to epithelial cells in the nasal turbinates, and prominently within intact epithelium; olfactory mucosa was mostly spared. The SARS-CoV-2 receptor ACE2 was extensively detected by IHC within turbinate epithelium, with decreased detection in lower respiratory tract epithelium and alveolar macrophages. This study expands on the knowledge of the pathology and pathogenesis of natural SARS-CoV-2 infection in mink and supports their further investigation as a potential animal model of SARS-CoV-2 infection in humans.

Lassa virus (LASV), a hemorrhagic fever virus endemic to West Africa, causes conjunctivitis in patients with acute disease. To examine ocular manifestations of LASV, we histologically examined eyes from infected guinea pigs. In fatal disease, LASV immunostaining was most prominent in the anterior uvea, especially in the filtration angle, ciliary body, and iris and in and around vessels in the bulbar conjunctiva and peripheral cornea, where it co-localized with an endothelial marker (platelet endothelial cell adhesion molecule). Antigen was primarily associated with infiltration of T-lymphocytes around vessels in the anterior uvea and with new vessel formation at the peripheral cornea. In animals that exhibited clinical signs but survived infection, eyes had little to no inflammation and no LASV immunostaining 6 weeks after infection. Overall, in this model, LASV antigen was restricted to the anterior uvea and was associated with mild chronic inflammation in animals with severe disease but was not detected in survivors.

The need for high-affinity, SARS-CoV-2-specific monoclonal antibodies (mAbs) is critical in the face of the global COVID-19 pandemic, as such reagents can have important diagnostic, research, and therapeutic applications. Of greatest interest is the ~300 amino acid receptor binding domain (RBD) within the S1 subunit of the spike protein because of its key interaction with the human angiotensin converting enzyme 2 (hACE2) receptor present on many cell types, especially lung epithelial cells. We report here the development and functional characterization of 29 nanomolar-affinity mouse SARS-CoV-2 mAbs created by an accelerated immunization and hybridoma screening process. Differing functions, including binding of diverse protein epitopes, viral neutralization, impact on RBD-hACE2 binding, and immunohistochemical staining of infected lung tissue, were correlated with variable gene usage and sequence.

Sudden-onset sensorineuronal hearing loss (SNHL) is reported in approximately one-third of survivors of Lassa fever (LF) and remains the most prominent cause of Lassa virus (LASV)-associated morbidity in convalescence. Using a guinea pig model of LF, and incorporating animals from LASV vaccine trials, we investigated viral antigen distribution and histopathology in the ear of infected animals to elucidate the pathogenesis of hearing loss associated with LASV infection. Antigen was detected only in animals that succumbed to disease and was found within structures of the inner ear that are intimately associated with neural detection and/or translation of auditory stimuli and in adjacent vasculature. No inflammation or viral cytopathic changes were observed in the inner ear or surrounding structures in these animals. In contrast, no viral antigen was detected in the ear of surviving animals. However, all survivors that exhibited clinical signs of disease during the course of infection developed perivascular mononuclear inflammation within and adjacent to the ear, indicating an ongoing inflammatory response in these animals that may contribute to hearing loss. These data contribute to the knowledge of LASV pathogenesis in the auditory system, support an immune-mediated process resulting in LASV-associated hearing loss, and demonstrate that vaccination protecting animals from clinical disease can also prevent infection-associated auditory pathology.

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Zika virus (ZIKV) invades and persists in the central nervous system (CNS), causing severe neurological diseases. However the virus journey, from the bloodstream to tissues through a mature endothelium, remains unclear. Here, we show that ZIKV-infected monocytes represent suitable carriers for viral dissemination to the CNS using human primary monocytes, cerebral organoids derived from embryonic stem cells, organotypic mouse cerebellar slices, a xenotypic human-zebrafish model, and human fetus brain samples. We find that ZIKV-exposed monocytes exhibit higher expression of adhesion molecules, and higher abilities to attach onto the vessel wall and transmigrate across endothelia. This phenotype is associated to enhanced monocyte-mediated ZIKV dissemination to neural cells. Together, our data show that ZIKV manipulates the monocyte adhesive properties and enhances monocyte transmigration and viral dissemination to neural cells. Monocyte transmigration may represent an important mechanism required for viral tissue invasion and persistence that could be specifically targeted for therapeutic intervention., Zika virus (ZIKV) can infect the central nervous system, but it is not clear how it reaches the brain. Here, Ayala-Nunez et al. show in ex vivo and in vivo models that ZIKV can hitch a ride in monocytes in a Trojan Horse manner to cross the endothelium and disseminate the virus.

Fatal Lyme carditis caused by the spirochete Borrelia burgdorferi rarely is identified. Here, we describe the pathologic, immunohistochemical, and molecular findings of five case patients. These sudden cardiac deaths associated with Lyme carditis occurred from late summer to fall, ages ranged from young adult to late 40s, and four patients were men. Autopsy tissue samples were evaluated by light microscopy, Warthin-Starry stain, immunohistochemistry, and PCR for B. burgdorferi, and immunohistochemistry for complement components C4d and C9, CD3, CD79a, and decorin. Post-mortem blood was tested by serology. Interstitial lymphocytic pancarditis in a relatively characteristic road map distribution was present in all cases. Cardiomyocyte necrosis was minimal, T cells outnumbered B cells, plasma cells were prominent, and mild fibrosis was present. Spirochetes in the cardiac interstitium associated with collagen fibers and co-localized with decorin. Rare spirochetes were seen in the leptomeninges of two cases by immunohistochemistry. Spirochetes were not seen in other organs examined, and joint tissue was not available for evaluation. Although rare, sudden cardiac death caused by Lyme disease might be an under-recognized entity and is characterized by pancarditis and marked tropism of spirochetes for cardiac tissues.

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral hemorrhagic disease seen exclusively in humans. Central nervous system (CNS) infection and neurological involvement have also been reported in CCHF. In the current study, we inoculated NSG-SGM3 mice engrafted with human hematopoietic CD34+ stem cells with low-passage CCHF virus strains isolated from human patients. In humanized mice, lethal disease develops, characterized by histopathological change in the liver and brain. To date, targets of neurological infection and disease have not been investigated in CCHF. CNS disease in humanized mice was characterized by gliosis, meningitis, and meningoencephalitis, and glial cells were identified as principal targets of infection. Humanized mice represent a novel lethal model for studies of CCHF countermeasures, and CCHF-associated CNS disease. Our data suggest a role for astrocyte dysfunction in neurological disease and identify key regions of infection in the CNS for future investigations of CCHF.

Here we describe clinicopathologic features of Ebola virus disease in pregnancy. One woman infected with Sudan virus in Gulu, Uganda, in 2000 had a stillbirth and survived, and another woman infected with Bundibugyo virus had a live birth with maternal and infant death in Isiro, the Democratic Republic of the Congo in 2012. Ebolavirus antigen was seen in the syncytiotrophoblast and placental maternal mononuclear cells by immunohistochemical analysis, and no antigen was seen in fetal placental stromal cells or fetal organs. In the Gulu case, ebolavirus antigen localized to malarial parasite pigment-laden macrophages. These data suggest that trophoblast infection may be a mechanism of transplacental ebolavirus transmission.

Fatal Lyme carditis caused by the spirochete Borrelia burgdorferi rarely is identified. Here, we describe the pathologic, immunohistochemical, and molecular findings of five case patients. These sudden cardiac deaths associated with Lyme carditis occurred from late summer to fall, ages ranged from young adult to late 40s, and four patients were men. Autopsy tissue samples were evaluated by light microscopy, Warthin-Starry stain, immunohistochemistry, and PCR for B. burgdorferi, and immunohistochemistry for complement components C4d and C9, CD3, CD79a, and decorin. Post-mortem blood was tested by serology. Interstitial lymphocytic pancarditis in a relatively characteristic road map distribution was present in all cases. Cardiomyocyte necrosis was minimal, T cells outnumbered B cells, plasma cells were prominent, and mild fibrosis was present. Spirochetes in the cardiac interstitium associated with collagen fibers and co-localized with decorin. Rare spirochetes were seen in the leptomeninges of two cases by immunohistochemistry. Spirochetes were not seen in other organs examined, and joint tissue was not available for evaluation. Although rare, sudden cardiac death caused by Lyme disease might be an under-recognized entity and is characterized by pancarditis and marked tropism of spirochetes for cardiac tissues.

Chlamydia trachomatis genital infection in women causes serious adverse reproductive complications, and is a strong co-factor for human papilloma virus (HPV)-associated cervical epithelial carcinoma. We tested the hypothesis that Chlamydia induces epithelial-mesenchyme transition (EMT) involving T cell-derived TNF-alpha signaling, caspase activation, cleavage inactivation of dicer and dysregulation of micro-RNA (miRNA) in the reproductive epithelium; the pathologic process of EMT causes fibrosis and fertility-related epithelial dysfunction, and also provides the co-factor function for HPV-related cervical epithelial carcinoma. Using a combination of microarrays, immunohistochemistry and proteomics, we showed that chlamydia altered the expression of crucial miRNAs that control EMT, fibrosis and tumorigenesis; specifically, miR-15a, miR-29b, miR-382 and MiR-429 that maintain epithelial integrity were down-regulated, while miR-9, mi-R-19a, miR-22 and miR-205 that promote EMT, fibrosis and tumorigenesis were up-regulated. Chlamydia induced EMT in vitro and in vivo, marked by the suppression of normal epithelial cell markers especially E-cadherin but up-regulation of mesenchymal markers of pathological EMT, including T-cadherin, MMP9, and fibronectin. Also, Chlamydia upregulated pro-EMT regulators, including the zinc finger E-box binding homeobox protein, ZEB1, Snail1/2, and thrombospondin1 (Thbs1), but down-regulated anti-EMT and fertility promoting proteins (i.e., the major gap junction protein connexin 43 (Cx43), Mets1, Add1Scarb1 and MARCKSL1). T cell-derived TNF-alpha signaling was required for chlamydial-induced infertility and caspase inhibitors prevented both infertility and EMT. Thus, chlamydial-induced T cell-derived TNF-alpha activated caspases that inactivated dicer, causing alteration in the expression of reproductive epithelial miRNAs and induction of EMT. EMT causes epithelial malfunction, fibrosis, infertility, and the enhancement of tumorigenesis of HPV oncogene-transformed epithelial cells. These findings provide a novel understanding of the molecular pathogenesis of chlamydia-associated diseases, which may guide a rational prevention strategy.

Rocky Mountain spotted fever (RMSF), a tick-borne zoonosis caused by Rickettsia rickettsii, is among the deadliest of all infectious diseases. To identify the distribution of various genotypes of R. rickettsii associated with fatal RMSF, we applied molecular typing methods to samples of DNA extracted from formalin-fixed, paraffin-embedded tissue specimens obtained at autopsy from 103 case-patients from seven countries who died of RMSF. Complete sequences of one or more intergenic regions were amplified from tissues of 30 (29%) case-patients and revealed a distribution of genotypes consisting of four distinct clades, including the Hlp clade, regarded previously as a non-pathogenic strain of R. rickettsii. Distinct phylogeographic patterns were identified when composite case-patient and reference strain data were mapped to the state and country of origin. The phylogeography of R. rickettsii is likely determined by ecological and environmental factors that exist independently of the distribution of a particular tick vector.