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TRANSMISSION AND PATHOGENESIS OF HANTAVIRUS
Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
HANTAVIRUS ÖVERFÖRING OCH PATOGENES (Swedish)
Abstract [en]

Hantaviruses are the causative agents of hemorrhagic fever with renal syndrome (HFRS) in Eurasia, and of hantavirus cardiopulmonary syndrome (HCPS) in the Americas. Transmission to humans usually occurs by inhalation of aerosolized virus-contaminated rodent excreta. To date, human-to-human transmission has only been described for the Andes hantavirus. The mode of transmission of Andes hantavirus is not yet known, but transmission through saliva has been suggested. In Sweden, we have one hantavirus that is pathogenic to humans, Puumala virus (PUUV), which is endemic in Central and Northern Europe. It induces a relatively mild form of HFRS, also called nephropathia epidemica (NE). The rodent reservoir is the bank vole (Myodes glareolus). The mechanism behind the pathogenesis of hantavirus is complex and probably involves both virus-mediated and host-mediated mechanisms. The aim of this project was to investigate the transmission mechanisms and pathogenesis of hantavirus disease in humans.

In our first study, we described the largest outbreak of PUUV so far in Sweden. We investigated factors that might be important for causing the outbreak, and suggested that a peak in the bank vole population together with concurrent extreme weather conditions most probably contributed to the outbreak.

Our next studies concentrated on human-to-human transmission of hantaviruses. We found PUUV RNA in saliva from PUUV-infected patients, suggesting that there is PUUV in the saliva of infected humans, although no person-to person transmission appears to occur with PUUV.  In the studies that followed, we showed that human saliva and human salivary components could inhibit hantavirus replication. We also found PUUV-specific IgA in the saliva of PUUV-infected patients, which might prevent person-to-person transmission of the virus. 

In the final study, we focused on the pathogenesis of NE. One hundred five patients were included in a prospective study.  They were divided into a group with mild disease and a group with moderate or severe disease. We found that the immune response had a dual role in disease development. It was partly responsible for development of severe disease, with significantly higher amounts of neutrophils in severely ill patients, but it was also protective against severe disease, because patients with mild disease had higher levels of PUUV-specific IgG.

In conclusion, a peak in the bank vole population in combination with extreme weather will increase the risk of human infection, PUUV RNA is present in saliva, PUUV-specific IgA and salivary components inhibit person-to-person transmission of PUUV, and the immune response is important for the pathogenesis of PUUV and the severity of the disease.

Abstract [sv]

Hantavirus är en grupp av virus som finns hos gnagare som bär på viruset utan att själva bli märkbart sjuka. Varje hantavirus har anpassat sig till sin egen art av gnagare som de infekterar (kallas virusets reservoar). Hantaviruset kan överföras till människor från gnagare och kallas då för en zoonos eftersom detsprids från djur till människa. I människa orsakar hantavirus blödarfeber med njurpåverkan i Eurasien och blödarfeber med med hjärt och lungpåverkan i Nord- och Sydamerika.

I Sverige har vi bara ett hantavirus som är sjukdomsframkallande hos människor, Puumala-viruset som även finns i delar av övriga Europa. Det framkallar en relativt mild form av blödarfeber, som kallas sorkfeber eller Nephropathia epidemica. Puumala-virusets reservoar är skogssorken (Myodes glareolus).

Människor smittas oftast av hantavirus när de andas in infekterat damm som innehåller utsöndringar (avföring, urin eller saliv) från gnagare som har torkat in och sedan blivit luftburet. Vad man vet hittills så finns det bara ett hantavirus som smittar från person till person, för övriga hantavirus är människan en ”dead end”. Det virus som kan smitta från person till person heter Andes hantavirus och finns i Sydamerika. Andes hantavirus har en mus som reservoar från vilken människor kan smittas, sedan har smittan i vissa fall förts vidare från människa till människa, som tur är har dessa utbrott gått att stoppa. Fastän utbrotten har varit små har många personer dött, eftersom dödligheten är så hög, ungefär 30-40% av de diagnostiserade fallen dör. Hur Andes hantavirus överförs från människa till människa är inte känt men överföring genom saliv har föreslagits.

Hur viruset ger upphov till sjukdom hos människa är inte klarlagt. Studier talar för att mekanismen bakom sjukdomsutvecklingen (den så kallade patogenesen) hos hantavirusorsakade blödarfebrar är komplex. Sannolikt beror patogenesen både på egenskaper hos viruset och värden d.v.s. människan som är smittad av viruset. Vårt mål med detta projekt var att undersöka vad som hindrar överföring av Puumala hantavirus från människa till människa och att undersöka hur virusinfektionen påverkar sjukdomsutvecklingen hos människan.

I vår första studie beskrev vi det största utbrottet av sorkfeber hittills i Sverige och vi undersökte faktorer som kan ha orsakat utbrottet. Vi föreslog att en topp i skogssorkpopulationen samtidigt med extremt varmt väder troligen bidrog till utbrottet. Utbrottet skedde i december och det extremt varma vädret medförde att snön smälte bort. Sorkarna bor vanligtvis under snön på vintern, vi tror att frånvaro av snötäcke fick sorkarna att söka sig till byggnader för att söka skydd och där kom i kontakt med människor.

Våra efterföljande studier fokuserade på överföring av hantavirus från människa till människa. Vi hittade Puumala-virusets arvsmassa (RNA) i saliv från sorkfeberpatienter, vilket tyder på att det finns Puumala-virus i saliven hos infekterade människor, även om ingen överföring från person till person verkar inträffa. I efterföljande studier visade vi att mänsklig saliv och mänskliga salivkomponenter minskar hantavirus smittsamhet. Vi fann också Puumala-virusspecifika IgA-antikroppar i saliven från sorkfeberpatienter, vilket kan förhindra överföring från person till person.

I den sista studien fokuserade vi på patogenesen hos människor efter hantavirusinfektion. 105 patienter ingick i en prospektiv studie och delades in i en grupp med mild sjukdom och en grupp med måttlig/svår sjukdom. Vi hittade en dubbel roll hos immunsvaret för sjukdomsutvecklingen. Immunsvaret var delvis ansvarig för utveckling av svår sjukdom med betydligt högre mängd neutrofiler hos svårt sjuka patienter, men det var också skyddande mot allvarlig sjukdom, eftersom patienter med en mild sjukdom hade högre nivåer av Puumalavirusspecifika IgG-antikroppar. Detta talar för att behandling med IgG-antikroppar specifikt riktade mot hantavirus skulle kunna vara effektiv hos hantavirusinfekterade patienter.

Sammanfattningsvis; en topp i skogssorkspopulationen i kombination med extremt väder ökar risken för infektion hos människor; Puumala-virus arvsmassa (RNA) finns i saliv; Puumala-virusspecifika IgA-antikroppar och salivkomponenter hämmar överföring av Puumalavirus från person till person; immunsvaret är viktigt för Puumala-virus patogenes och sjukdomens svårighetsgrad.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet , 2015. , 43 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1701
Keyword [en]
Puumala virus, Hantavirus, human-to-human transmission, saliva, nephropathia epidemica, NE, IgA, IgG, IgM, neutrophils, neutrophil, viremia, treatment, climate, snow cover, temperature.
National Category
Medical and Health Sciences
Research subject
Medical Virology
Identifiers
URN: urn:nbn:se:umu:diva-99687ISBN: 978-91-7601-225-3 (print)OAI: oai:DiVA.org:umu-99687DiVA: diva2:787748
Public defence
2015-03-06, Betula, byggnad 6M, Umeå Universitet, Norrlands Universitetssjukhus, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2015-02-13 Created: 2015-02-11 Last updated: 2015-02-16Bibliographically approved
List of papers
1. Outbreak of Puumala virus infection, Sweden.
Open this publication in new window or tab >>Outbreak of Puumala virus infection, Sweden.
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2008 (English)In: Emerging infectious diseases, ISSN 1080-6059, Vol. 14, no 5, 808-10 p.Article in journal (Refereed) Published
Abstract [en]

An unexpected and large outbreak of Puumala virus infection in Sweden resulted in 313 nephropathia epidemica patients/100,000 persons in Västerbotten County during 2007. An increase in the rodent population, milder weather, and less snow cover probably contributed to the outbreak.

Identifiers
urn:nbn:se:umu:diva-21112 (URN)18439368 (PubMedID)
Available from: 2009-04-02 Created: 2009-04-02 Last updated: 2015-02-12
2. Hantavirus RNA in saliva from patients with hemorrhagic fever with renal syndrome.
Open this publication in new window or tab >>Hantavirus RNA in saliva from patients with hemorrhagic fever with renal syndrome.
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2008 (English)In: Emerging infectious diseases, ISSN 1080-6059, Vol. 14, no 3, 406-11 p.Article in journal (Refereed) Published
Abstract [en]

Hantaviruses cause 2 zoonotic diseases, hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome. Infection is usually initiated after inhalation of virus-contaminated rodent excreta. In addition to the zoonotic infection route, growing evidence suggests person-to-person transmission of Andes virus. For this reason, we studied whether saliva from HFRS patients contained hantavirus. During an outbreak in northern Sweden of nephropathia epidemica (NE), a milder form of hemorrhagic fever with renal syndrome, we collected saliva and plasma from 14 hospitalized NE patients with verified Puumala virus (PUUV) infection. PUUV RNA was detected in saliva from 10 patients (range 1,530-121,323 PUUV RNA copies/mL) by quantitative reverse transcription-PCR. The PUUV S-segment sequences from saliva and plasma of the same patients were identical. Our data show that hantavirus RNA could be detected in human saliva several days after onset of disease symptoms and raise the question whether interhuman transmission of hantavirus may occur through saliva.

Identifiers
urn:nbn:se:umu:diva-21113 (URN)18325254 (PubMedID)
Available from: 2009-04-02 Created: 2009-04-02 Last updated: 2015-02-12
3. Antiviral effect of human saliva against hantavirus.
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2008 (English)In: Journal of medical virology, ISSN 1096-9071, Vol. 80, no 12, 2122-6 p.Article in journal (Refereed) Published
Abstract [en]

Hemorrhagic fever with renal syndrome (HFRS) and Hantavirus pulmonary syndrome are zoonotic diseases caused by rodent borne hantaviruses. Transmission to humans occurs usually by inhalation of aerozolized virus-contaminated rodent excreta. Although human-to-human transmission of Andes hantavirus has been observed, the mode of transmission is currently not known. Saliva from Puumala hantavirus (PUUV)-infected patients was shown recently to contain viral RNA. To test if human saliva interferes with hantavirus replication, the effect of saliva and salivary proteins on hantavirus replication was studied. It was observed that saliva from healthy individuals reduced Hantaan hantavirus (HTNV) infectivity, although not completely. Furthermore, HTNV was resistant against the antiviral capacity of histatin 5, lysozyme, lactoferrin, and SLPI, but was inhibited by mucin. Inoculation of bank voles (Myodes glareolus) with HFRS-patient saliva, positive for PUUV-RNA, did not induce sero-conversion. In conclusion, no evidence of infectious virus in patient saliva was found. However, the in vitro experiments showed that HTNV, the prototype hantavirus, is insensitive to several antiviral salivary proteins, and is partly resistant to the antiviral effect of saliva. It therefore remains to be shown if human saliva might contain infectious virions early during infection, that is, before seroconversion.

Identifiers
urn:nbn:se:umu:diva-21106 (URN)10.1002/jmv.21332 (DOI)19040288 (PubMedID)
Available from: 2009-04-02 Created: 2009-04-02 Last updated: 2015-02-12
4. Hantavirus-specific IgA in saliva and viral antigen in the parotid gland in patients with hemorrhagic fever with renal syndrome
Open this publication in new window or tab >>Hantavirus-specific IgA in saliva and viral antigen in the parotid gland in patients with hemorrhagic fever with renal syndrome
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2011 (English)In: Journal of Medical Virology, ISSN 0146-6615, E-ISSN 1096-9071, Vol. 83, no 5, 864-870 p.Article in journal (Refereed) Published
Abstract [en]

The Hantavirus genus comprises rodent borne, zoonotic viruses of the Bunyaviridae family that cause hemorrhagic fever with renal syndrome (HFRS) in Eurasia and hantavirus cardiopulmonary syndrome (HCPS) in the Americas. Rodent saliva contains infectious hantavirus and evidence suggests that hantavirus is also shed in human saliva, but person-to-person transmission is rare. In saliva, immunoglobulin (Ig) A is the predominant immunoglobulin class. Secretory IgA serves as an important first line of defence on epithelial surfaces and the binding of secretory IgA to pathogens can inhibit adherence of microorganisms to mucosal cells and neutralize viruses. This study investigated the presence and importance of salivary IgA in relation to viral antigen in the saliva by testing Puumala hantavirus (PUUV) specific IgA, and RNA in saliva in acutely ill patients with HFRS. In saliva samples, PUUV specific IgA was detected in 12 of 33 (36%) patients with HFRS and 20 (61%) were PUUV RNA positive. There was a statistically significant inverse association between the presence of salivary IgA antibodies and PUUV RNA in the saliva. PUUV-specific IgA in saliva was not found in a long-term follow-up, while PUUV IgA in serum was detected in three patients, 28-32 months after the initial study. Notably, both PUUV RNA and PUUV nucleocapsid antigen were detected in endothelial cells within the parotid gland of a deceased patient with HFRS. J. Med. Virol. 83:864-870, 2011. © 2011 Wiley-Liss, Inc.

Keyword
puumalavirus;HFRS;HCPS;antibody;zoonosis;transmission
National Category
Infectious Medicine
Identifiers
urn:nbn:se:umu:diva-41725 (URN)10.1002/jmv.22040 (DOI)21360546 (PubMedID)
Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2017-12-11Bibliographically approved
5. Viral load and humoral immune response in association with disease severity in Puumala hantavirus-infected patients-implications for treatment
Open this publication in new window or tab >>Viral load and humoral immune response in association with disease severity in Puumala hantavirus-infected patients-implications for treatment
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2014 (English)In: Clinical Microbiology and Infection, ISSN 1198-743X, E-ISSN 1469-0691, Vol. 20, no 3, 235-241 p.Article in journal (Refereed) Published
Abstract [en]

Hantaviruses are the causative agents of haemorrhagic fever with renal syndrome (HFRS) in Eurasia and of hantavirus cardiopulmonary syndrome (HCPS) in the Americas. The case fatality rate varies between different hantaviruses and can be up to 40%. At present, there is no specific treatment available. The hantavirus pathogenesis is not well understood, but most likely, both virus-mediated and host-mediated mechanisms are involved. The aim of the present study was to investigate the association among Puumala hantavirus (PUUV) viral RNA load, humoral immune response and disease severity in patients with HFRS. We performed a study of 105 PUUV-infected patients that were followed during the acute phase of disease and for up to 1-3 months later. Fifteen of the 105 patients (14%) were classified as having moderate/severe disease. A low PUUV-specific IgG response (p <0.05) and also a higher white blood cell count (p <0.001) were significantly associated with more severe disease. The PUUV RNA was detected in a majority of patient plasma samples up to 9 days after disease onset; however, PUUV RNA load or longevity of viraemia were not significantly associated with disease severity. We conclude that a low specific IgG response was associated with disease severity in patients with HFRS, whereas PUUV RNA load did not seem to affect the severity of HFRS. Our results raise the possibility of passive immunotherapy as a useful treatment for hantavirus-infected patients.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2014
Keyword
age, disease severity, hantavirus, haemorrhagic fever with renal syndrome, humoral immune response, immunoglobulins, neutrophil, Puumala virus, viral load, white blood cell count
National Category
Microbiology in the medical area Infectious Medicine
Research subject
Microbiology
Identifiers
urn:nbn:se:umu:diva-74938 (URN)10.1111/1469-0691.12259 (DOI)000331024400018 ()23742660 (PubMedID)
Available from: 2013-07-02 Created: 2013-07-02 Last updated: 2017-12-06Bibliographically approved

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