Pulmonary and systemic involvement in COVID-19 patients assessed with ultrasound-guided minimally invasive autopsy.

AIMS: Brazil ranks high in the number of coronavirus disease 19 (COVID-19) cases and the COVID-19 mortality rate. In this context, autopsies are important to confirm the disease, determine associated conditions, and study the pathophysiology of this novel disease. The aim of this study was to assess the systemic involvement of COVID-19. In order to follow biosafety recommendations, we used ultrasound-guided minimally invasive autopsy (MIA-US), and we present the results of 10 initial autopsies. METHODS AND RESULTS: We used MIA-US for tissue sampling of the lungs, liver, heart, kidneys, spleen, brain, skin, skeletal muscle and testis for histology, and reverse transcription polymerase chain reaction to detect severe acute respiratory syndrome coronavirus 2 RNA. All patients showed exudative/proliferative diffuse alveolar damage. There were intense pleomorphic cytopathic effects on the respiratory epithelium, including airway and alveolar cells. Fibrinous thrombi in alveolar arterioles were present in eight patients, and all patients showed a high density of alveolar megakaryocytes. Small thrombi were less frequently observed in the glomeruli, spleen, heart, dermis, testis, and liver sinusoids. The main systemic findings were associated with comorbidities, age, and sepsis, in addition to possible tissue damage due to the viral infection, such as myositis, dermatitis, myocarditis, and orchitis. CONCLUSIONS: MIA-US is safe and effective for the study of severe COVID-19. Our findings show that COVID-19 is a systemic disease causing major events in the lungs and with involvement of various organs and tissues. Pulmonary changes result from severe epithelial injury and microthrombotic vascular phenomena. These findings indicate that both epithelial and vascular injury should be addressed in therapeutic approaches.

Metformin arrests the progression of established kidney disease in the subtotal nephrectomy model of chronic kidney disease.

Metformin, an AMP-activated protein kinase (AMPK) activator, has been shown in previous studies to reduce kidney fibrosis in different models of experimental chronic kidney disease (CKD). However, in all of these studies, the administration of metformin was initiated before the establishment of renal disease, which is a condition that does not typically occur in clinical settings. The aim of the present study was to investigate whether the administration of metformin could arrest the progression of established renal disease in a well-recognized model of CKD, the subtotal kidney nephrectomy (Nx) model. Adult male Munich-Wistar rats underwent either Nx or sham operations. After the surgery (30 days), Nx rats that had systolic blood pressures of >170 mmHg and albuminuria levels of >40 mg/24 h were randomized to a no-treatment condition or to a treatment condition with metformin (300 mg·kg-1·day-1) for a period of either 60 or 120 days. After 60 days of treatment, we did not observe any differences in kidney disease parameters between Nx metformin-treated and untreated rats. However, after 120 days, Nx rats that had been treated with metformin displayed significant reductions in albuminuria levels and in markers of renal fibrosis. These effects were independent of any other effects on blood pressure or glycemia. In addition, treatment with metformin was also able to activate kidney AMPK and therefore improve mitochondrial biogenesis. It was concluded that metformin can arrest the progression of established kidney disease in the Nx model, likely via the activation of AMPK.

Mesenchymal Stromal Cells Induce Podocyte Protection in the Puromycin Injury Model.

Podocytes are specialized cells with a limited capacity for cell division that do not regenerate in response to injury and loss. Insults that compromise the integrity of podocytes promote proteinuria and progressive renal disease. The aim of this study was to evaluate the potential renoprotective and regenerative effects of mesenchymal stromal cells (mSC) in a severe form of the podocyte injury model induced by intraperitoneal administration of puromycin, aggravated by unilateral nephrectomy. Bone derived mSC were isolated and characterized according to flow cytometry analyses and to their capacity to differentiate into mesenchymal lineages. Wistar rats were divided into three groups: Control, PAN, and PAN+ mSC, consisting of PAN rats treated with 2 × 105 mSC. PAN rats developed heavy proteinuria, hypertension, glomerulosclerosis and significant effacement of the foot process. After 60 days, PAN rats treated with mSC presented a significant amelioration of all these abnormalities. In addition, mSC treatment recovered WT1 expression, improved nephrin, podocin, synaptopodin, podocalyxin, and VEGF expression, and downregulated proinflammatory Th1 cytokines in the kidney with a shift towards regulatory Th2 cytokines. In conclusion, mSC administration induced protection of podocytes in this experimental PAN model, providing new perspectives for the treatment of renal diseases associated with podocyte damage.

Pathogenic role of angiotensin II and the NF-κB system in a model of malignant hypertensive nephrosclerosis.

We previously reported that rats treated with an NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), during lactation developed hypertension in adult life, without apparent functional or structural damage to kidneys, providing a new model of essential hypertension. Here, we investigated whether uninephrectomy associated with salt overload would unveil a latent renal dysfunction in this model, aggravating arterial hypertension and promoting renal injury. Male Munich-Wistar rat pups received PDTC from maternal milk (PDTCLact) from 0 to 20 days after birth. Another group received no treatment during lactation. All offspring underwent uninephrectomy (UNx) at 10 weeks of age and then were subdivided into NS, receiving a normal salt (0.5% Na+) diet, PDTCLact + NS, HS, receiving a high-salt diet (2% Na+ chow + 0.5% saline to drink), and PDTCLact+HS. Twelve weeks later, HS rats were moderately hypertensive with mild albuminuria and renal injury. In contrast, severe hypertension, glomerulosclerosis, and cortical collagen deposition were prominent in PDTCLact + HS animals, along with "onion-skin" arteriolar lesions, evidence of oxidative stress and intense renal infiltration by macrophages, and lymphocytes and angiotensin II-positive cells, contrasting with low circulating renin. The NF-κB pathway was also activated. In a separate set of PDTCLact+HS rats, Losartan treatment prevented NF-κB activation and strongly attenuated glomerular injury, cortical fibrosis, and renal inflammation. NF-κB activity during late nephrogenesis is essential for the kidneys to properly maintain sodium homeostasis in adult life. Paradoxically, this same system contributed to renal injury resembling that caused by malignant hypertension when renal dysfunction caused by its inhibition during lactation was unmasked by uninephrectomy associated with HS.

Klotho deficiency aggravates sepsis-related multiple organ dysfunction.

Sepsis-induced organ failure is characterized by a massive inflammatory response and oxidative stress. Acute kidney injury (AKI) occurs in approximately half of patients in septic shock, and the mortality associated with sepsis-induced AKI is unacceptably high. Klotho is a protein expressed by renal cells and has anti-senescence properties. Klotho has also been shown to protect the kidneys in ischemia-reperfusion injury and to have antioxidant properties. To analyze the role of Klotho in sepsis-related organ dysfunction and AKI, we used a cecal ligation and puncture (CLP) model of sepsis in heterozygous Klotho-haploinsufficient mice and their wild-type littermates (CLP- Kl/+ and CLP-WT mice, respectively). In comparison with the CLP-WT mice, CLP- Kl/+ mice showed lower survival, impaired renal function, impaired hepatic function, greater oxidative stress, upregulation of inflammatory pathways (at the systemic and kidney tissue levels), and increased NF-κB activation. It is noteworthy that CLP- Kl/+ mice also showed lower heart-rate variability, less sympathetic activity, impaired baroreflex sensitivity to sodium nitroprusside, and a blunted blood pressure response to phenylephrine. We also demonstrated that sepsis creates a state of acute Klotho deficiency. Given that low Klotho expression exacerbates sepsis and multiple organ dysfunction, Klotho might play a protective role in sepsis, especially in elderly individuals in whom Klotho expression is naturally reduced.

Innate And Adaptive Immunity are Progressively Activated in Parallel with Renal Injury in the 5/6 Renal Ablation Model.

The mechanisms triggering renal inflammation in chronic kidney disease (CKD) are unclear. We performed a detailed analysis of the time course of innate and adaptive immunity activation in the 5/6 renal ablation (Nx) model. Munich-Wistar rats undergoing Nx were studied 15, 60 and 120 days after ablation. Hypertension, albuminuria, creatinine retention, interstitial expansion and infiltration by macrophages and T-lymphocytes were already evident 15 days after Nx. PCR-array was used to screen for altered gene expression, whereas gene and protein expressions of TLR4, CASP1, IL-1ß and NLRP3 were individually assessed. Tlr4, Tlr5, Lbp, Nlrp3, Casp1, Irf7 and Il1b were already upregulated 15 days after Nx, while activation of Tlr2, Tlr7, Tlr9, Nod2, Tnf and Il6 was seen after 60 days post-ablation. The number of genes related to innate or adaptive immunity grew steadily with time. These observations indicate that parallel activation of innate and adaptive immunity antecedes glomerular injury and involves a growing number of intricate signaling pathways, helping to explain the difficulty in detaining renal injury in Nx as CKD advances, and, stressing the need for early treatment. Additionally, these findings may contribute to the search of therapeutic targets specific for advanced phases of CKD.

Caloric Restriction Is More Efficient than Physical Exercise to Protect from Cisplatin Nephrotoxicity via PPAR-Alpha Activation.

The antineoplastic drug cisplatin promotes renal injury, which limits its use. Protocols that reduce renal cisplatin toxicity will allow higher doses to be used in cisplatin treatment. Here, we compare physical exercise and caloric restriction (CR) as protocols to reduce cisplatin renal injury in mice. Male C57BL/6 were divided into four groups: Control, cisplatin, exercise + cisplatin, and 30% CR + cisplatin. Animals were injected with a single dose of cisplatin (20 mg/kg i.p.) and sacrificed 96 h after injection. Quantitative real time PCR, histological analyses, immunohistochemistry, and biochemical measurements were performed to investigate renal injury, necrosis, apoptosis, and inflammatory mechanisms. Both protocols protected against cisplatin renal injury, but CR was more effective in reducing uraemia and renal necrosis. The CR + Cisplatin group exhibited reduced serum IL-1ß and TNF-α levels. No differences were noted in the renal mRNA expression of cytokines. Both interventions reduced apoptosis, but only the CR + Cisplatin group decreased TNFR2 protein expression. PPAR-α was activated in mice after CR. An antagonist of PPAR-α blocked the protective effect of CR. Both interventions attenuated the nephrotoxicity caused by cisplatin injection, but CR + Cisplatin showed a better response by modulating TNFR2. Moreover, part of the CR benefit depends on PPAR-α activation.

Catheter-based induction of renal ischemia/reperfusion in swine: description of an experimental model.

Several techniques to induce renal ischemia have been proposed: clamp, PVA particles, and catheter-balloon. We report the development of a controlled, single-insult model of unilateral renal ischemia/reperfusion (I/R) without contralateral nephrectomy, using a suitable model, the pig. This is a balloon-catheter-based model using a percutaneous, interventional radiology procedure. One angioplasty balloon-catheter was placed into the right renal artery and inflated for 120 min and reperfusion over 24 h. Serial serums were sampled from the inferior vena cava and urine was directly sampled from the bladder throughout the experiment, and both kidneys were excised after 24 h of reperfusion. Analyses of renal structure and function were performed by hematoxylin-eosin/periodic Acid-Schiff, serum creatinine (SCr), blood urea nitrogen (BUN), fractional excretion of ions, and glucose, SDS-PAGE analysis of urinary proteins, and serum neutrophil gelatinase-associated lipocalin (NGAL). Total nitrated protein was quantified to characterize oxidative stress. Acute tubular necrosis (ATN) was identified in every animal, but only two animals showed levels of SCr above 150% of baseline values. As expected, I/R increased SCr and BUN. Fractional sodium, potassium, chloride, and bicarbonate excretion were modulated during ischemia. Serum-nitrated proteins and NGAL had two profiles: decreased with ischemia and increased after reperfusion. This decline was associated with increased protein excretion during ischemia and early reperfusion. Altogether, these data show that the renal I/R model can be performed by percutaneous approach in the swine model. This is a suitable translational model to study new early renal ischemic biomarkers and pathophysiological mechanisms in renal ischemia.

Kinin B2 receptor deletion and blockage ameliorates cisplatin-induced acute renal injury.

Cisplatin treatment has been adopted in some chemotherapies; however, this drug can induce acute kidney injury due its ability to negatively affect renal function, augment serum levels of creatinine and urea, increase the acute tubular necrosis score and up-regulate cytokines (e.g., IL-1ß and TNF-α). The kinin B2 receptor has been associated with the inflammation process, as well as the regulation of cytokine expression, and its deletion resulted in an improvement in the diabetic nephropathy status. To examine the role of the kinin B2 receptor in cisplatin-induced acute kidney injury, kinin B2 receptor knockout mice were challenged with cisplatin. Additionally, WT mice were treated with a B2 receptor antagonist after cisplatin administration. B2 receptor-deficient mice were less sensitive to this drug than the WT mice, as shown by reduced weight loss, better preservation of kidney function, down regulation of inflammatory cytokines and less acute tubular necrosis. Moreover, treatment with the kinin B2 receptor antagonist effectively reduced the levels of serum creatinine and blood urea after cisplatin administration. Thus, our data suggest that the kinin B2 receptor is involved in cisplatin-induced acute kidney injury by mediating the necrotic process and the expression of inflammatory cytokines, thus resulting in declined renal function. These results highlight the kinin B2 receptor antagonist treatment in amelioration of nephrotoxicity induced by cisplatin therapy.

Activation of platelet-activating factor receptor exacerbates renal inflammation and promotes fibrosis.

Platelet-activating factor (PAF) is a lipid mediator with important pro-inflammatory effects, being synthesized by several cell types including kidney cells. Although there is evidence of its involvement in acute renal dysfunction, its role in progressive kidney injury is not completely known. In the present study, we investigated the role of PAF receptor (PAFR) in an experimental model of chronic renal disease. Wild-type (WT) and PAFR knockout (KO) mice underwent unilateral ureter obstruction (UUO), and at kill time, urine and kidney tissue was collected. PAFR KO animals compared with WT mice present: (a) less renal dysfunction, evaluated by urine protein/creatinine ratio; (b) less fibrosis evaluated by collagen deposition, type I collagen, Lysyl Oxidase-1 (LOX-1) and transforming growth factor ß (TGF-ß) gene expression, and higher expression of bone morphogenetic protein 7 (BMP-7) (3.3-fold lower TGF-ß/BMP-7 ratio); (c) downregulation of extracellular matrix (ECM) and adhesion molecule-related machinery genes; and (d) lower levels of pro-inflammatory cytokines. These indicate that PAFR engagement by PAF or PAF-like molecules generated during UUO potentiates renal dysfunction and fibrosis and might promote epithelial-to-mesenchymal transition (EMT). Also, early blockade of PAFR after UUO leads to a protective effect, with less fibrosis deposition. In conclusion, PAFR signaling contributes to a pro-inflammatory environment in the model of obstructive nephropathy, favoring the fibrotic process, which lately will generate renal dysfunction and progressive organ failure.

Effects of Schizolobium parahyba extract on experimental Bothrops venom-induced acute kidney injury.

BACKGROUND: Venom-induced acute kidney injury (AKI) is a frequent complication of Bothrops snakebite with relevant morbidity and mortality. The aim of this study was to assess the effects of Schizolobium parahyba (SP) extract, a natural medicine with presumed anti-Bothrops venom effects, in an experimental model of Bothrops jararaca venom (BV)-induced AKI. METHODOLOGY: Groups of 8 to 10 rats received infusions of 0.9% saline (control, C), SP 2 mg/kg, BV 0.25 mg/kg and BV immediately followed by SP (treatment, T) in the doses already described. After the respective infusions, animals were assessed for their glomerular filtration rate (GFR, inulin clearance), renal blood flow (RBF, Doppler), blood pressure (BP, intra-arterial transducer), renal vascular resistance (RVR), urinary osmolality (UO, freezing point), urinary neutrophil gelatinase-associated lipocalin (NGAL, enzyme-linked immunosorbent assay [ELISA]), lactate dehydrogenase (LDH, kinetic method), hematocrit (Hct, microhematocrit), fibrinogen (Fi, Klauss modified) and blinded renal histology (acute tubular necrosis score). PRINCIPAL FINDINGS: BV caused significant decreases in GFR, RBF, UO, HcT and Fi; significant increases in RVR, NGAL and LDH; and acute tubular necrosis. SP did not prevent these changes; instead, it caused a significant decrease in GFR when used alone. CONCLUSION: SP administered simultaneously with BV, in an approximate 10∶1 concentration, did not prevent BV-induced AKI, hemolysis and fibrinogen consumption. SP used alone caused a decrease in GFR.

Kinin B1 receptor deficiency attenuates cisplatin-induced acute kidney injury by modulating immune cell migration.

UNLABELLED: Cisplatin is a chemotherapeutic agent that causes severe renal dysfunction. The kinin B1 receptor has been associated with the migration of immune cells to injured tissue as well as with renal inflammation. To examine the role of the kinin B1 receptor in cisplatin-induced acute kidney injury, we used kinin B1 receptor knockout mice and treatment with a receptor antagonist before and after cisplatin administration. Cisplatin injection caused exacerbation of renal macrophage and neutrophil migration, higher levels of serum creatinine and blood urea, upregulation of B1 receptor mRNA and an increase in pro-inflammatory cytokines expression. B1 receptor knockout mice exhibited a reduction in serum creatinine and blood urea levels, diminished apoptosis, and decreased cisplatin-induced upregulation of inflammatory components. Moreover, treatment with the B1 receptor antagonist prior to cisplatin administration normalized serum creatinine, blood urea levels, protected from acute tubular necrosis, apoptosis-related genes, and prevented upregulation of pro-inflammatory cytokines. Thus, we propose that kinins have an important role in cisplatin-induced acute kidney injury by impairing immune cells migration to renal tissue during cisplatin nephrotoxicity. KEY MESSAGE: Kinin B1 receptor is upregulated after cisplatin exposure. Kinin B1 receptor deficiency diminishes the nephrotoxicity caused by cisplatin. Kinin B1 receptor deficiency ameliorates the inflammatory response. Kinin B1 receptor deficiency diminishes apoptosis caused by cisplatin. Kinin B1 receptor antagonism ameliorates renal function after cisplatin injection.

Chronic VEGF blockade worsens glomerular injury in the remnant kidney model.

VEGF inhibition can promote renal vascular and parenchymal injury, causing proteinuria, hypertension and thrombotic microangiopathy. The mechanisms underlying these side effects are unclear. We investigated the renal effects of the administration, during 45 days, of sunitinib (Su), a VEGF receptor inhibitor, to rats with 5/6 renal ablation (Nx). Adult male Munich-Wistar rats were distributed among groups S+V, sham-operated rats receiving vehicle only; S+Su, S rats given Su, 4 mg/kg/day; Nx+V, Nx rats receiving V; and Nx+Su, Nx rats receiving Su. Su caused no change in Group S. Seven and 45 days after renal ablation, renal cortical interstitium was expanded, in association with rarefaction of peritubular capillaries. Su did not worsen hypertension, proteinuria or interstitial expansion, nor did it affect capillary rarefaction, suggesting little angiogenic activity in this model. Nx animals exhibited glomerulosclerosis (GS), which was aggravated by Su. This effect could not be explained by podocyte damage, nor could it be ascribed to tuft hypertrophy or hyperplasia. GS may have derived from organization of capillary microthrombi, frequently observed in Group Nx+Su. Treatment with Su did not reduce the fractional glomerular endothelial area, suggesting functional rather than structural cell injury. Chronic VEGF inhibition has little effect on normal rats, but can affect glomerular endothelium when renal damage is already present.

Antifibrotic effect of tamoxifen in a model of progressive renal disease.

Tamoxifen, a selective estrogen receptor modulator, has antifibrotic properties; however, whether it can attenuate renal fibrosis is unknown. In this study, we tested the effects of tamoxifen in a model of hypertensive nephrosclerosis (chronic inhibition of nitric oxide synthesis with L-NAME). After 30 days, treated rats had significantly lower levels of albuminuria as well as lower histologic scores for glomerulosclerosis and interstitial fibrosis than untreated controls. Tamoxifen was renoprotective despite having no effect on the sustained, severe hypertension induced by L-NAME. Tamoxifen prevented the accumulation of extracellular matrix by decreasing the expression of collagen I, collagen III, and fibronectin mRNA and protein. These renoprotective effects associated with inhibition of TGF-ß1 and plasminogen activator inhibitor-1, and with a significant reduction in α-smooth muscle actin-positive cells in the renal interstitium. Furthermore, tamoxifen abrogated IL-1ß- and angiotensin-II-induced proliferation of fibroblasts from both kidney explants and from the NRK-49F cell line. Tamoxifen also inhibited the expression of extracellular matrix components and the production and release of TGF-ß1 into the supernatant of these cells. In summary, tamoxifen exhibits antifibrotic effects in the L-NAME model of hypertensive nephrosclerosis, likely through the inhibition of TGF-ß1, suggesting that it may have therapeutic use in CKD treatment.

Bradykinin receptor 1 activation exacerbates experimental focal and segmental glomerulosclerosis.

Focal and segmental glomerulosclerosis (FSGS) is one of the most important causes of end-stage renal failure. The bradykinin B1 receptor has been associated with tissue inflammation and renal fibrosis. To test for a role of the bradykinin B1 receptor in podocyte injury, we pharmacologically modulated its activity at different time points in an adriamycin-induced mouse model of FSGS. Estimated albuminuria and urinary protein to creatinine ratios correlated with podocytopathy. Adriamycin injection led to loss of body weight, proteinuria, and upregulation of B1 receptor mRNA. Early treatment with a B1 antagonist reduced albuminuria and glomerulosclerosis, and inhibited the adriamycin-induced downregulation of podocin, nephrin, and α-actinin-4 expression. Moreover, delayed treatment with antagonist also induced podocyte protection. Conversely, a B1 agonist aggravated renal dysfunction and even further suppressed the levels of podocyte-related molecules. Thus, we propose that kinin has a crucial role in the pathogenesis of FSGS operating through bradykinin B1 receptor signaling.

Programmed hypertension in rats treated with a NF-κB inhibitor during nephrogenesis: renal mechanisms.

Suppression of the renin-angiotensin system (RAS) during murine lactation causes progressive renal injury, indicating a physiological action of angiotensin II on nephrogenesis. The nuclear factor NF-κB system is one of the main intracellular mediators of angiotensin II. We investigated whether inhibition of this system with pyrrolidine dithiocarbamate (PDTC) during rat nephrogenesis would lead to similar hypertension and renal injury as observed with RAS suppressors. Immediately after delivery, 32 Munich-Wistar dams, each nursing 6 male pups, were divided into 2 groups: C, untreated, and PDTC, receiving PDTC, 280 mg kg(-1) day(-1) orally, during 21 days. After weaning, the offspring were followed until 10 months of age without treatment. Adult rats that received neonatal PDTC exhibited stable hypertension and myocardial injury, without albuminuria. To gain additional insight into this process, the renal expression of RAS components and sodium transporters were determined by quantitative real-time PCR (qRT-PCR) at 3 and 10 months of life. Renal renin and angiotensinogen were upregulated at 3 and downregulated at 10 months of age, suggesting a role for early local RAS activation. Likewise, there was early upregulation of the proximal sodium/glucose and sodium/bicarbonate transporters, which abated later in life, suggesting that additional factors sustained hypertension in the long run. The conclusions drawn from the findings were as follows: (1) an intact NF-κB system during nephrogenesis may be essential to normal renal and cardiovascular function in adult life; (2) neonatal PDTC represents a new model of hypertension, lacking overt structural injury or functional impairment of the kidneys; and (3) hypertension in this model seems associated with early temporary activation of renal RAS and sodium transporters.

Tuberculosis-associated collapsing glomerulopathy: remission after treatment.

Collapsing glomerulopathy (CG) is a severe form of nephrotic syndrome and has been mostly associated with human immunodeficiency virus (HIV) infection. Treatment response is poor, and the disease frequently leads to end-stage renal disease. More recently, CG has been described in association with other conditions, such as drug exposure and other infections, but renal prognosis remains unfavorable. This paper reports an interesting case of an HIV-negative patient with tuberculosis-related CG who needed dialysis for five months but presented full renal recovery after tuberculosis (TB) treatment and corticotherapy.

Lung pathology in fatal novel human influenza A (H1N1) infection.

RATIONALE: There are no reports of the systemic human pathology of the novel swine H1N1 influenza (S-OIV) infection. OBJECTIVES: The autopsy findings of 21 Brazilian patients with confirmed S-OIV infection are presented. These patients died in the winter of the southern hemisphere 2009 pandemic, with acute respiratory failure. METHODS: Lung tissue was submitted to virologic and bacteriologic analysis with real-time reverse transcriptase polymerase chain reaction and electron microscopy. Expression of toll-like receptor (TLR)-3, IFN-gamma, tumor necrosis factor-alpha, CD8(+) T cells and granzyme B(+) cells in the lungs was investigated by immunohistochemistry. MEASUREMENTS AND MAIN RESULTS: Patients were aged from 1 to 68 years (72% between 30 and 59 yr) and 12 were male. Sixteen patients had preexisting medical conditions. Diffuse alveolar damage was present in 20 individuals. In six patients, diffuse alveolar damage was associated with necrotizing bronchiolitis and in five with extensive hemorrhage. There was also a cytopathic effect in the bronchial and alveolar epithelial cells, as well as necrosis, epithelial hyperplasia, and squamous metaplasia of the large airways. There was marked expression of TLR-3 and IFN-gamma and a large number of CD8(+) T cells and granzyme B(+) cells within the lung tissue. Changes in other organs were mainly secondary to multiple organ failure. CONCLUSIONS: Autopsies have shown that the main pathological changes associated with S-OIV infection are localized to the lungs, where three distinct histological patterns can be identified. We also show evidence of ongoing pulmonary aberrant immune response. Our results reinforce the usefulness of autopsy in increasing the understanding of the novel human influenza A (H1N1) infection.