Longitudinal Assessment of Cytokine Expression and Plasminogen Activation in Hantavirus Cardiopulmonary Syndrome Reveals Immune Regulatory Dysfunction in End-Stage Disease

Pathogenic New World orthohantaviruses cause hantavirus cardiopulmonary syndrome (HCPS), a severe immunopathogenic disease in humans manifested by pulmonary edema and respiratory distress, with case fatality rates approaching 40%. High levels of inflammatory mediators are present in the lungs and systemic circulation of HCPS patients. Previous studies have provided insights into the pathophysiology of HCPS. However, the longitudinal correlations of innate and adaptive immune responses and disease outcomes remain unresolved. This study analyzed serial immune responses in 13 HCPS cases due to Sin Nombre orthohantavirus (SNV), with 11 severe cases requiring extracorporeal membrane oxygenation (ECMO) treatment and two mild cases. We measured viral load, levels of various cytokines, urokinase plasminogen activator (uPA), and plasminogen activator inhibitor-1 (PAI-1). We found significantly elevated levels of proinflammatory cytokines and PAI-1 in five end-stage cases. There was no difference between the expression of active uPA in survivors' and decedents' cases. However, total uPA in decedents' cases was significantly higher compared to survivors'. In some end-stage cases, uPA was refractory to PAI-1 inhibition as measured by zymography, where uPA and PAI-1 were strongly correlated to lymphocyte counts and IFN-γ. We also found bacterial co-infection influencing the etiology and outcome of immune response in two cases. Unsupervised Principal Component Analysis and hierarchical cluster analyses resolved separate waves of correlated immune mediators expressed in one case patient due to a sequential co-infection of bacteria and SNV. Overall, a robust proinflammatory immune response, characterized by an imbalance in T helper 17 (Th17) and regulatory T-cells (Treg) subsets, was correlated with dysregulated inflammation and mortality. Our sample size is small; however, the core differences correlated to survivors and end-stage HCPS are instructive.

Hemodynamic and Pulmonary Permeability Characterization of Hantavirus Cardiopulmonary Syndrome by Transpulmonary Thermodilution

Hantavirus cardiopulmonary syndrome (HCPS) is characterized by capillary leak, pulmonary edema (PE), and shock, which leads to death in up to 40% of patients. Treatment is supportive, including mechanical ventilation (MV) and extracorporeal membrane oxygenation (ECMO). Hemodynamic monitoring is critical to titrate therapy and to decide ECMO support. Transpulmonary thermodilution (TPTD) provides hemodynamic and PE data that have not been systematically used to understand HCPS pathophysiology. We identified 11 HCPS patients monitored with TPTD: eight on MV, three required ECMO. We analyzed 133 measurements to describe the hemodynamic pattern and its association with PE. The main findings were reduced stroke volume, global ejection fraction (GEF), and preload parameters associated with increased extravascular lung water and pulmonary vascular permeability compatible with hypovolemia, myocardial dysfunction, and increased permeability PE. Lung water correlated positively with heart rate (HR, r = 0.20) and negatively with mean arterial pressure (r = −0.27) and GEF (r = −0.36), suggesting that PE is linked to hemodynamic impairment. Pulmonary vascular permeability correlated positively with HR (r = 0.31) and negatively with cardiac index (r = −0.49), end-diastolic volume (r = −0.48), and GEF (r = −0.40), suggesting that capillary leak contributes to hypovolemia and systolic dysfunction. In conclusion, TPTD data suggest that in HCPS patients, increased permeability leads to PE, hypovolemia, and circulatory impairment.

Dendritic Cells (DCs) as "Fire Accelerants" of Hantaviral Pathogenesis

Hantaviruses are widespread zoonotic pathogens found around the globe. Depending on their geographical location, hantaviruses can cause two human syndromes, haemorrhagic fever with renal syndrome (HFRS) or hantavirus pulmonary syndrome (HPS). HPS and HFRS have many commonalities amongst which excessive activation of immune cells is a prominent feature. Hantaviruses replicate in endothelial cells (ECs), the major battlefield of hantavirus-induced pathogenesis, without causing cytopathic effects. This indicates that a misdirected response of human immune cells to hantaviruses is causing damage. As dendritic cells (DCs) orchestrate antiviral immune responses, they are in the focus of research analysing hantavirus-induced immunopathogenesis. In this review, we discuss the interplay between hantaviruses and DCs and the immunological consequences thereof.

Landscape, Climate and Hantavirus Cardiopulmonary Syndrome Outbreaks

We performed a literature review in order to improve our understanding of how landscape and climate drivers affect HCPS outbreaks. Anthropogenic landscape changes such as forest loss, fragmentation and agricultural land uses are related with a boost in hantavirus reservoir species abundance and hantavirus prevalence in tropical areas, increasing HCPS risk. Additionally, higher precipitation, especially in arid regions, favors an increase in vegetational biomass, which augments the resources for reservoir rodents, also increasing HCPS risk. Although these relationships were observed, few studies described it so far, and the ones that did it are concentrated in few places. To guide future research on this issue, we build a conceptual model relating landscape and climate variables with HCPS outbreaks and identified research opportunities. We point out the need for studies addressing the effects of landscape configuration, temperature and the interaction between climate and landscape variables. Critical landscape thresholds are also highly relevant, once HCPS risk transmission can increase rapidly above a certain degree of landscape degradation. These studies could be relevant to implement preventive measures, creating landscapes that can mitigate disease spread risk.

Endothelial Nitric Oxide Synthase G894T Polymorphism Associates with Disease Severity in Puumala Hantavirus Infection

Introduction

Hantavirus infections are characterized by both activation and dysfunction of the endothelial cells. The underlying mechanisms of the disease pathogenesis are not fully understood. Here we tested the hypothesis whether the polymorphisms of endothelial nitric oxide synthase, eNOS G894T, and inducible nitric oxide synthase, iNOS G2087A, are associated with the severity of acute Puumala hantavirus (PUUV) infection.

Patients and Methods

Hospitalized patients (n = 172) with serologically verified PUUV infection were examined. Clinical and laboratory variables reflecting disease severity were determined. The polymorphisms of eNOS G894T (Glu298Asp, rs1799983) and iNOS G2087A (Ser608Leu, rs2297518) were genotyped.

Results

The rare eNOS G894T genotype was associated with the severity of acute kidney injury (AKI). The non-carriers of G-allele (TT-homozygotes) had higher maximum level of serum creatinine than the carriers of G-allele (GT-heterozygotes and GG-homozygotes; median 326, range 102–1041 vs. median 175, range 51–1499 μmol/l; p = 0.018, respectively). The length of hospital stay was longer in the non-carriers of G-allele than in G-allele carriers (median 8, range 3–14 vs. median 6, range 2–15 days; p = 0.032). The rare A-allele carriers (i.e. AA-homozygotes and GA-heterozygotes) of iNOS G2087A had lower minimum systolic and diastolic blood pressure than the non-carriers of A-allele (median 110, range 74–170 vs.116, range 86–162 mmHg, p = 0.019, and median 68, range 40–90 vs. 72, range 48–100 mmHg; p = 0.003, respectively).

Conclusions

Patients with the TT-homozygous genotype of eNOS G894T had more severe PUUV-induced AKI than the other genotypes. The eNOS G894T polymorphism may play role in the endothelial dysfunction observed during acute PUUV infection.

First detection of Dobrava hantavirus from a patient with severe haemorrhagic fever with renal syndrome by SYBR Green-based real time RT-PCR

Dobrava hantavirus (DOBV) infection was diagnosed in a previously healthy 46-y-old hunter suffering from severe haemorrhagic fever with renal syndrome (HFRS). Specific IgM antibodies against DOBV were identified by an immunofluorescence assay, while viral nucleic acid was detected by the molecular method, confirming the diagnosis. Our results reveal an existing risk of DOBV transmission to humans in Hungary.

Dhori virus (Orthomyxoviridae: Thogotovirus) infection of mice produces a disease and cytokine response pattern similar to that of highly virulent influenza A (H5N1) virus infection in humans

Mice infected with Dhori virus (DHOV) develop a fulminant, systemic, and uniformly fatal illness that has many of the clinical and pathologic findings seen in H5N1 influenza A virus infection. However, the role of host's immune response in DHOV infection remains unclear. In this study, the concentrations of 23 inflammatory cytokines and chemokines were measured in the liver, lungs, and sera of mice during the course of DHOV infection. Liver function, level of viremia, and hematologic response were also monitored. Infected animals exhibited significant leucopenia and lymphopenia, which directly correlated with the disease progression. High yields of infectious virus along with strikingly elevated expression of various inflammatory mediators, including tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, IL-6, IL-10, macrophage inflammatory protein (MIP)-1alpha, manocyte chemoattractant protein (MCP)-1, and interferon (IFN)-alpha, indicate that these responses play an important role in the observed disease and pathology. The overall clinical, pathologic, and immunologic responses of ICR mice to DHOV infection closely resemble those described for highly virulent influenza A virus infection in humans, thereby offering a realistic, safe, and alternative animal model for studying the pathogenesis and treatment of highly pathogenic avian influenza virus.

Elevated testosterone and reduced 5-HIAA concentrations are associated with wounding and hantavirus infection in male Norway rats

Among rodents that carry hantaviruses, males are more likely to engage in aggression and to be infected than females. One mode of hantavirus transmission is via the passage of virus in saliva during wounding. The extent to which hantaviruses cause physiological changes in their rodent host that increase aggression and, therefore, virus transmission has not been fully documented. To assess whether steroid hormones and neurotransmitters contribute to the correlation between aggression and Seoul virus infection, Norway rats were trapped in Baltimore, Maryland and wounding, infection status, steroid hormones, and concentrations of neurotransmitters, including norepinephrine (NE), dopamine (DA), 3,4-dihydroxyphenol acetic acid (DOPAC), serotonin (5-HT), and 5-hydroxyindole-3-acetic acid (5-HIAA) in select brain regions were examined. Older males and males with high-grade wounds were more likely to have anti-Seoul virus IgG and viral RNA in organs than either juveniles or adult males with less severe wounds. Wounded males had higher circulating testosterone, lower hypothalamic 5-HIAA, and lower NE in the amygdala than males with no wounds. Infected males had higher concentrations of testosterone, corticosterone, NE in the hypothalamus, and DOPAC in the amygdala than uninfected males, regardless of wounding status. In the present study, wounded males that were infected with Seoul virus had elevated testosterone and reduced 5-HIAA concentrations, suggesting that these neuroendocrine mechanisms may contribute to aggression and the likelihood of transmission of hantavirus in natural populations of male Norway rats.

Temporal analysis of Andes virus and Sin Nombre virus infections of Syrian hamsters

Andes virus (ANDV) and Sin Nombre virus (SNV) are rodent-borne hantaviruses that cause a highly lethal hemorrhagic fever in humans known as hantavirus pulmonary syndrome (HPS). There are no vaccines or specific drugs to prevent or treat HPS, and the pathogenesis is not understood. Syrian hamsters infected with ANDV, but not SNV, develop a highly lethal disease that closely resembles HPS in humans. Here, we performed a temporal pathogenesis study comparing ANDV and SNV infections in hamsters. SNV was nonpathogenic and viremia was not detected despite the fact that all animals were infected. ANDV was uniformly lethal with a mean time to death of 11 days. The first pathology detected was lymphocyte apoptosis starting on day 4. Animals were viremic and viral antigen was first observed in multiple organs by days 6 and 8, respectively. Levels of infectious virus in the blood increased 4 to 5 logs between days 6 and 8. Pulmonary edema was first detected ultrastructurally on day 6. Ultrastructural analysis of lung tissues revealed the presence of large inclusion bodies and substantial numbers of vacuoles within infected endothelial cells. Paraendothelial gaps were not observed, suggesting that fluid leakage was transcellular and directly attributable to infecting virus. Taken together, these data imply that HPS treatment strategies aimed at preventing virus replication and dissemination will have the greatest probability of success if administered before the viremic phase; however, because vascular leakage is associated with infected endothelial cells, a therapeutic strategy targeting viral replication might be effective even at later times (e.g., after disease onset).

[Hantavirus infections]

Hantaviruses are cosmopolite anthropozoonosis considered as an emerging disease. Four pathogenic types for humans and part of the Bunyaviridae species are hosted by rodents and have been isolated: the Sin nombre virus responsible for the severe American respiratory form; the Hantaan and Seoul viruses responsible for hemorrhagic fevers with renal syndrome (HFRS) of severe to moderate expression in Asia and also in the Balkans; the Puumala virus responsible for HFRS of moderate expression or the socalled nephropathia epidemica in Europe. The Puumala virus is responsible for a minor form of the disease that is observed in areas of the Occidental sector of the ex-URSS, in Scandinavia and in the rest of Europe, notably in the North-East of France. The epidemic episodes occur every three years. They follow the proliferation of rodents, notably russet voles, the reservoir hosts, and their degree of infection. The concept of an occupation at risk in 20 to 49 year-old men (working in forests, agriculture, living near a forest, contact with wood) in an endemic area has not always been found. Its clinical form can vary greatly in its presentation. Basically it is a severe algic influenza syndrome accompanied by acute myopia in 38% of cases, but is nearly pathognomonic in the context. Respiratory involvement is frequent but benign. The initial syndrome can suggest an abdominal or urological surgical emergency, which is source of diagnostic and therapeutic errors. Early biological examination reveals thrombopenia and proteinuria. Then more or less severe acute kidney failure appears in slightly more than 50% of cases. Although it usually regresses with symptomatic treatment, after effects remain in some patients. The environmental changes, the geographical distribution depending on the biotope, the dynamics and behaviour of rodents and the viral circulation between them and its transmission to human beings and its risk factors must continue to be studied in order to gain further knowledge on the epidemiology of this anthropozoonosis.

[The renal failure and capillary leak during the acute stage of (Dobrava) DOB and PUU (Puumala) infection]

The target organ for Puumala (PUU) and Dobrava (DOB) viruses is the kidney, but the impact on renal function seems far more important in DOB infection than in PUU infections. Aim of study was to estimate the renal failure and capillary leak during the acute stage of DOB-infection and PUU-infection. 50 patients with serological conformed diagnosis of acute hantavirus infection were included in the study. Diuresis, serum urea and creatinine were measured. Size of kidneys and presence of ascites was followed by ultrasonography. Enlargement of both kidneys were found in all (100%) patients. Ascites was present in 8/25 (32%) DOB patients; in 1/25 (4%) PUU patient and pleural effusion in four 4/25 (16%) DOB patients. The statistically significant difference in the mean urinary output was during 5th, 6th and 7th day of hospitalization (P<0,05). Serum creatinine and urea levels were at significantly higher levels for DOB than for PUU patients (P<0,05). Acute haemodialysis was needed in 7/25 (28 %) of the DOB patients. One DOB patient died. DOB virus infection is associated with a more severe kidney function disorders than PUU virus infection. Capillary leak, which caused swollen of kidney and ascites is probably the pathogenesis key factor.

Hantaviruses: a tale of two hemispheres

Infectious febrile nephropathies, initially described as epidemics during military campaigns in Europe and Asia at the turn of the 20(th) century, were eventually all unified under the rubric of hemorrhagic fever with renal syndrome (HFRS) and ascribed to infection from rodent-borne hantaviruses. At the end of the century, hantavirus pulmonary syndrome (HPS) was described throughout the Americas as a consequence of infection with the New World hantaviruses. The epidemiology and clinical manifestations of these diseases are linked to the ecology of their associated rodent hosts. Murine rodents (Old World mice and rats) are associated with the severe forms of HFRS in Asia and the Balkans due to Hantaan, Dobrava, and Seoul viruses. Hantaan virus causes an estimated 50-100,000 infections a year in China alone. Arvicoline rodents (voles) are associated with a mild form of HFRS in Europe called nephropathia epidemica due to Puumala virus. Sigmodontine rodents (New World rats and mice) are associated with approximately 200 HPS cases per year throughout the Americas caused by over a dozen viruses. The viruses are mainly transmitted as small-particle aerosols of rodent excreta, and the subsequent infections share cardiovascular shock as a prominent feature, although HFRS causes predominantly renal disease, while HPS causes a predominantly non-cardiogenic pulmonary edema - hemorrhage involvement varies in the syndromes on the basis of virus subtypes. Efforts are underway to refine prevention strategies, understand the pathogenesis of the shock, and identify therapeutic modalities.

Hantavirus

When hantaviruses hit the headlines with the advent in May 1993 of a new disease in the USA, and later in the New World from Canada to south Argentina, called "hantavirus pulmonary syndrome" (HPS), speculations in the lay press rose from the very beginning around the possibilities of a biological warfare (BW) weapon. Indeed, the responsible agent of HPS, hantavirus, was almost unknown at that moment in the New World, was airborne, seemed to target preferentially young adults, and induced a devastating cardio-pulmonary collapse with a high case-fatality rate (50%), often within hours. It quickly became clear, however, that the same scourge had been known for many years in the Old World under different and mostly milder presentations. With the rapidly increasing knowledge about hantaviruses, it also became clear that they lack many of the potentials of an "ideal" BW weapon, as will be explained in this paper.

Maporal viral infection in the Syrian golden hamster: a model of hantavirus pulmonary syndrome

Hantavirus pulmonary syndrome (HPS) is a severe and often fatal rodent-borne zoonosis. Maporal (MAP) virus is a newly discovered hantavirus that originally was isolated from an arboreal rice rat captured in central Venezuela. The results of this study indicate that MAP virus in the Syrian golden hamster (Mesocricetus auratus) can cause a disease that is clinically and pathologically remarkably similar to HPS. The similarities include the time course of clinical disease, presence of virus-specific IgG at the onset of clinical disease, subacute pneumonitis, rapid onset of diffuse alveolar edema in the absence of necrosis, hepatic-portal triaditis, mononuclear-cellular infiltrate in lung and liver, widespread distribution of hantaviral antigen in endothelial cells of the microvasculature of lung and other tissues, and variable lethality. These similarities suggest that the MAP virus-hamster system is a useful model for studies of the pathogenesis of HPS and for the evaluation of potential therapeutic agents.

Complete nucleotide sequence of a Chilean hantavirus

We have determined the genomic sequence of an Andes virus (ANDV) strain isolated from an infected Oligoryzomys longicaudatus rodent trapped in Chile in 1997. This strain, for which we propose the designation Chile R123, reproduces essential attributes of hantavirus pulmonary syndrome (HPS) when injected intramuscularly into laboratory hamsters (Hooper et al., Virology 289 (2001) 6-14). The L, M, and S segment sequences of Chile R123 are 6562, 3671, and 1871 nt long, respectively, with an overall G+C content of 38.5%. These respective genome segments could encode a 247 kd RNA-dependent RNA polymerase (RdRP), 126 kd glycoprotein precursor (GPC), and 48 kd nucleocapsid (N) protein, in line with other Sigmodontine rodent-associated hantaviruses. Among hantaviruses for which complete genomic sequences are available, Chile R123 is most closely related to Sin Nombre virus (SNV) strain NM R11, with greater than 85% amino acid identity between translated L and S segments and 78% amino acid identity between translated M segments. Because Chile R123 shares essentially 100% amino acid identity in regions of overlap with partially sequenced Argentinian and Chilean ANDV strains, Syrian hamster pathogenicity and the potential for interhuman transmission are features likely common to all ANDV strains.

Experimental infection of the Sigmodon alstoni cotton rat with Caño Delgadito virus, a South American hantavirus

Forty-eight Sigmodon alstoni (Alston's cotton rat) were inoculated with Caño Delgadito (CDG) virus to extend our knowledge and understanding of the natural host relationships of the hantaviruses indigenous to the Americas. Infectious CDG virus was recovered from oropharyngeal secretions, urine, or solid tissues of nine of 12 animals killed on day 9 post-inoculation (PI), 14 of 24 animals killed on day 18 or 27 PI, and none of 12 animals killed on day 54 PI. In addition, virus-specific RNA was detected in the kidneys of six of the 12 animals killed on day 54 PI, and adult cotton rats inoculated with the kidneys of four animals killed on day 54 PI developed antibody to CDG virus. Collectively, the results indicate that CDG virus can establish lengthy (perhaps lifelong) infections in Alston's cotton rat and thus support the concept that S. alstoni is the principal host of CDG virus.

Hantaviruses: an overview

Hantaviruses are a newly emerging group of rodent-borne viruses that have significant zoonotic potential. Human infection by hantaviruses can result in profound morbidity and mortality, with death rates as high as 50%, and potentially long-term cardiovascular consequences. Hantaviruses are carried by peridomestic and wild rodents worldwide and have occasionally been linked to infections in laboratory rodents. Because these viruses have been associated with significant human disease, they have become the subject of intense scientific investigation. In this review the reader is introduced to the hantaviruses, including hantavirus diseases and their pathogenesis. A review of the biology, morphology, and molecular biology of the hantaviruses with a brief overview of the ecology and biology of hantavirus-rodent pairs is also included. The risks of occupational exposure to hantaviruses, diagnosis of hantavirus infections, and methods for handling potentially infected rodents and tissues are discussed as well.

Renal function and blood pressure five years after puumala virus-induced nephropathy

BACKGROUND

Nephropathia epidemica (NE) is a mild form of hemorrhagic fever with renal syndrome caused by Puumala hantavirus. Its long-term prognosis is considered favorable. Some reports suggest, however, that a previous hantavirus infection increases the risk of hypertension.

METHODS

We studied 46 previously healthy subjects (26 males and 20 females, mean age of 44 years) who had serologically confirmed NE three to seven years previously, and 38 healthy, seronegative controls (22 males and 16 females, mean age of 44 years). Ambulatory blood pressure (ABP) was monitored. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined by 51CrEDTA and 131I-hippurate clearances, respectively. The filtration fraction (FF) was calculated. Quantitative 24-hour urinary protein excretion (UprotE) and timed overnight urinary excretion of alpha1-microglobulin were measured.

RESULTS

The NE patients had a higher mean ambulatory systolic BP than the controls (123 +/- 13 vs. 117 +/- 9 mm Hg, P = 0. 008). GFR and FF were increased in patients compared with controls (GFR, 120 +/- 20 vs. 109 +/- 14 mL/min/1.73 m2, P = 0.006; FF, 19 +/- 3 vs. 18 +/- 3%, P = 0.030), but ERPF did not differ between the groups. The patients also had higher UPE than the controls (median 0. 18 g/day, range 0.12 to 0.38 vs. median 0.14 g/day, range 0.09 to 0. 24, P < 0.001, respectively). The overnight urinary excretion rate of alpha1-microglobulin exceeded 7 microg/min in nine patients.

CONCLUSION

Three to seven years after NE, the patients had higher GFR and FF, more proteinuria, and higher ambulatory systolic BP compared with the healthy controls. NE may thus cause mild renal lesions and alterations in BP in some patients.

Outbreak of hantavirus infection in the Four Corners region of the United States in the wake of the 1997-1998 El Nino-southern oscillation

Hantavirus cardiopulmonary syndrome (HCPS), a rodent-borne zoonosis, has been endemic in the Americas for at least several decades. It is hypothesized that the 1991-1992 El Niño-southern oscillation (ENSO) caused increased precipitation that allowed an increase in rodent population densities, thereby increasing the possibility of transmission to humans. The result was a 1993-1994 outbreak of the disease in the Four Corners states of the southwestern United States. A second strong ENSO occurred in 1997-1998, after a period of considerable public education about the risks of hantavirus infection that began during the 1993-1994 outbreak. The caseload of HCPS increased 5-fold above baseline in the Four Corners states in 1998-1999. Regions that had received increased rainfall in 1998 were especially affected. A large majority of the 1998-1999 case patients reported indoor exposure to deer mice. Hantavirus outbreaks can occur in response to abiotic events, even in the face of extensive public education and awareness.

Acute Sin Nombre hantavirus infection without pulmonary syndrome, United States

Hantavirus pulmonary syndrome (HPS) occurs in most infections with Sin Nombre virus and other North American hantaviruses. We report five cases of acute hantavirus infection that did not fit the HPS case definition. The patients had characteristic prodromal symptoms without severe pulmonary involvement. These cases suggest that surveillance for HPS may need to be expanded.

Implications of the analogy between recombinant cytokine toxicities and manifestations of hantavirus infections

The etiologic hantavirus of the 1993 emergence of an acute pulmonary failure syndrome in the area around northwestern New Mexico was quickly recognized as related to the Hantaan virus responsible for the outbreak of Korean epidemic hemorrhagic fever (EHF) among UN troops in 1951. Discovery of the new disease which was named the hantavirus pulmonary syndrome (HPS) and its causative agent the Sine Nombre virus (SNV) inspired detailed comparisons between the two disorders. Major damage to the epithelial cells of the capillaries and arterioles throughout the body leading to extensive capillary leak and subsequent hypotension and shock was the common denominator. The lung capillaries and arterioles were the focus of attack that could lead to rapid pulmonary failure in HPS and the corresponding renal and retroperitoneal vessels that caused a more protracted illness in EHF, but both displayed remarkably similar peripheral blood abnormalities including abnormal mononuclear cells, immature neutrophilia, thrombocytopenia, and hemoconcentration characteristic enough to make blood smear examination a useful tool in early diagnosis. There are evidences that a heavy virus presence in the involved endothelial cells is accompanied by various mononuclear cells capable of generating potent immune response in these areas. Relevant toxic effects of systemically-administered high-dose interleukin-2 for resistant cancers include fever, chills, diarrhea, renal dysfunction, capillary leak syndrome accompanied by hypotension requiring aggressive pressor support, and occasional pleural effusions with diffuse pulmonary infiltrates and hypoxia severe enough to require ventilatory assistance. Peripheral blood mononuclear cells cultured in vitro with IL-2 secrete secondary cytokines such as IL-1, TNF-alpha, and interferon-gamma (IFN-gamma). TNF-alpha, implicated in the pathophysiology of septic shock, is capable of inducing adult respiratory distress syndrome (ARDS) in experimental animals and humans. The strong similarity of these effects to the manifestations noted in the hantavirus diseases justifies the conviction that these and other cytokines involved in potent immune responses would constitute the pathogenic toxic substances predicted by perceptive early investigators of EHF. This concept is favored by clear indications that in both diseases active virus infection disappears the first few days and the ages of involvement correlate with periods of immunocompetence. The paradox of systemic injections of IL-2 that risk hantavirus-type toxicities for treating renal cell carcinoma and melanoma might be avoided by giving potentially more efficacious plant mitogens like PHA as previously reported. The expanded disclosure of a collaborator's method suggesting superior potential for cancer cure involves a unique application of pokeweed mitogen that delivers various cellular and cytokine responses directly to the tumor.

Fatal illness associated with a new hantavirus in Louisiana

A fatal case of hantaviral illness occurred in Louisiana, outside of the range of P. maniculatus, the rodent reservoir for Sin Nombre virus. Hantavirus RNA and antigens were detected in patient autopsy tissues, and nucleotide sequence analysis of amplified polymerase chain reaction (PCR) products identified a newly recognized unique hantavirus, provisionally named Bayou virus. Prominent features of the clinical illness are compatible with hantavirus pulmonary syndrome (HPS), but several features such as renal insufficiency and intraalveolar hemorrhage are more compatible with hemorrhagic fever with renal syndrome (HFRS), a disease associated with Eurasian hantaviruses.

A macaque model for hantavirus infection

Cynomolgus macaques (Macaca fascicularis) were experimentally infected with Puumala virus (strain Hällnäs), which causes nephropathia epidemica in humans in western Europe. During the first week after intratracheal inoculation, the monkeys exhibited signs of lethargy followed by mild proteinuria and microhematuria. Histopathologic changes during the first 7 weeks after infection were largely confined to abnormalities in medullary tubular cells of the kidneys, which coincided with the demonstration of viral antigen and viral RNA. The development of different classes of virus-specific plasma antibodies to the respective viral antigens were similar to those observed in humans with nephropathia epidemica. This first description of a nonhuman primate model for hantavirus infection shows that the cynomolgus macaque provides a suitable model with which to study the pathogenesis of Puumala virus infections and to evaluate new diagnostic methods, immunization strategies, and therapies.