Double-blinded, randomised, placebo-controlled trial of convalescent plasma for COVID-19: analyses by neutralising antibodies homologous to recipients' variants

INTRODUCTION

Convalescent plasma (CP) emerged as potential treatment for COVID-19 early in the pandemic. While efficacy in hospitalised patients has been lacklustre, CP may be beneficial at the first stages of disease. Despite multiple new variants emerging, no trials have involved analyses on variant-specific antibody titres of CP.

METHODS

We recruited hospitalised COVID-19 patients within 10 days of symptom onset and, employing a double-blinded approach, randomised them to receive 200 ml convalescent plasma with high (HCP) or low (LCP) neutralising antibody (NAb) titre against the ancestral strain (Wuhan-like variant) or placebo in 1:1:1 ratio. Primary endpoints comprised intubation, corticosteroids for symptom aggravation, and safety assessed as serious adverse events. For a preplanned ad hoc analysis, the patients were regrouped by infused CP's NAb titers to variants infecting the recipients i.e. by titres of homologous HCP (hHCP) or LCP (hLCP).

RESULTS

Of the 57 patients, 18 received HCP, 19 LCP and 20 placebo, all groups smaller than planned. No significant differences were found for primary endpoints. In ad hoc analysis, hHCPrecipients needed significantly less respiratory support, and appeared to be given corticosteroids less frequently (1/14; 7.1%) than those receiving hLCP (9/23; 39.1%) or placebo (8/20; 40%), (p = 0.077).

DISCUSSION

Our double-blinded, placebo-controlled CP therapy trial remained underpowered and does not allow any firm conclusions for early-stage hospitalised COVID-19 patients. Interestingly, however, regrouping by homologous - recipients' variant-specific - CP titres suggested benefits for hHCP. We encourage similar re-analysis of ongoing/previous larger CP studies.

TRIAL REGISTRATION

ClinTrials.gov identifier: NCT0473040.

Experimental Reptarenavirus Infection of Boa constrictor and Python regius

Boid inclusion body disease (BIBD) causes losses in captive snake populations globally. BIBD is associated with the formation of cytoplasmic inclusion bodies (IBs), which mainly comprise reptarenavirus nucleoprotein (NP). In 2017, BIBD was reproduced by cardiac injection of boas and pythons with reptarenaviruses, thus demonstrating a causative link between reptarenavirus infection and the disease. Here, we report experimental infections of Python regius (n = 16) and Boa constrictor (n = 16) with three reptarenavirus isolates. First, we used pythons (n = 8) to test two virus delivery routes: intraperitoneal injection and tracheal instillation. Viral RNAs but no IBs were detected in brains and lungs at 2 weeks postinoculation. Next, we inoculated pythons (n = 8) via the trachea. During the 4 months following infection, snakes showed transient central nervous system (CNS) signs but lacked detectable IBs at the time of euthanasia. One of the snakes developed severe CNS signs; we succeeded in reisolating the virus from the brain of this individual and could demonstrate viral antigen in neurons. In a third attempt, we tested cohousing, vaccination, and sequential infection with multiple reptarenavirus isolates on boas (n = 16). At 10 months postinoculation, all but one snake tested positive for viral RNA in lung, brain, and/or blood, but none exhibited the characteristic IBs. Three of the four vaccinated snakes seemed to sustain challenge with the same reptarenavirus; however, neither of the two snakes rechallenged with different reptarenaviruses remained uninfected. Comparison of the antibody responses in experimentally versus naturally reptarenavirus-infected animals indicated differences in the responses.IMPORTANCE In the present study, we experimentally infected pythons and boas with reptarenavirus via either intraperitoneal injection or tracheal instillation. The aims were to experimentally induce boid inclusion body disease (BIBD) and to develop an animal model for studying disease transmission and pathogenesis. Both virus delivery routes resulted in infection, and infection via the trachea could reflect the natural route of infection. In the experimentally infected snakes, we did not find evidence of inclusion body (IB) formation, characteristic of BIBD, in pythons or boas. Most of the boas (11/12) remained reptarenavirus infected after 10 months, which suggests that they developed a persistent infection that could eventually have led to BIBD. We demonstrated that vaccination using recombinant protein or an inactivated virus preparation prevented infection by a homologous virus in three of four snakes. Comparison of the antibody responses of experimentally and naturally reptarenavirus-infected snakes revealed differences that merit further studies.

Evaluation of three rapid lateral flow antigen detection tests for the diagnosis of SARS-CoV-2 infection

INTRODUCTION

The COVID-19 pandemic has led to high demand of diagnostic tools. Rapid antigen detection tests have been developed and many have received regulatory acceptance such as CE IVD or FDA markings. Their performance needs to be carefully assessed.

MATERIALS AND METHODS

158 positive and 40 negative retrospective samples collected in saline and analyzed by a laboratory-developed RT-PCR test were used to evaluate Sofia (Quidel), Standard Q (SD Biosensor), and Panbio™ (Abbott) rapid antigen detection tests (RADTs). A subset of the specimens was subjected to virus culture.

RESULTS

The specificity of all RADTs was 100 % and the sensitivity and percent agreement was 80 % and 85 % for Sofia, 81 % and 85 % for Standard Q, and 83 % and 86 % for Panbio™, respectively. All three RADTs evaluated in this study reached a more than 90 % sensitivity for samples with a high viral load as estimated from the low Ct (Cycle threshold) values in the reference RT-PCR. Virus culture was successful in 80 % of specimens with a Ct value <25.

CONCLUSIONS

As expected, the RADTs were less sensitive than RT-PCR. However, they benefit from the speed and ease of testing, and lower price as compared to RT-PCR. Repeated testing in appropriate settings may improve the overall performance.

Chikungunya virus infections in Finnish travellers 2009-2019

The mosquito-borne chikungunya virus (CHIKV) causes an acute febrile illness with rash, joint and muscle pain.A realtime RT-PCR assay for CHIKV detecting non-structural protein (nsP2; CHIKV nsP2-RT-qPCR) was set up. All the serodiagnosed CHIKV cases detected during 2009-2019 in Finland were screened with the assay, followed by isolations attempts and sequencing using Sanger and next generation sequencing (NGS). To validate the assay external and in-house quality control samples were used and all were correctly identified. Specificity of the assay was 100%. Assay was sensitive to detect CHIKV RNA in dilution of 10^-8.During years 2009-2019 34 patients were diagnosed for acute CHIKV infection. Twelve out of 34 cases were positive by CHIKV nsP2-RT-qPCR.Two CHIKV isolations succeeded from two individuals infected originally in Thailand, 2019. From 12 CHIKV nsP2-RT-qPCR positive samples, five (42%) CHIKVs were successfully sequenced. In this study, CHIKVs from year 2019 clustered with CHIKV ECSA-lineage forming sub-cluster with strains from ones detected in Bangladesh 2017, and the ones from Jamaica (2014) within Asian lineage showing highest similarity to strains detected in Caribbean outbreak 2013-15.  Majority of the CHIKV infections detected in Finland originates from Asia and virus lineages reflect the global circulation of the pathogen.

Performance of six SARS-CoV-2 immunoassays in comparison with microneutralisation

There is an urgent need for reliable high-throughput serological assays for the management of the ongoing COVID-19 pandemic. Preferably, the performance of serological tests for a novel virus should be determined with clinical specimens against a gold standard, i.e. virus neutralisation. We compared the performance of six commercial immunoassays for the detection of SARS-COV-2 IgG, IgA and IgM antibodies, including four automated assays [Abbott SARS-COV-2 IgG (CE marked), Diasorin Liaison® SARS-COV-2 S1/S2 IgG (research use only, RUO), and Euroimmun SARS-COV-2 IgG and IgA (CE marked)], and two rapid lateral flow (immunocromatographic) tests [Acro Biotech 2019-nCoV IgG/IgM (CE marked) and Xiamen Biotime Biotechnology SARS-COV-2 IgG/IgM (CE marked)] with a microneutralisation test (MNT). Two specimen panels from serum samples sent to Helsinki University Hospital Laboratory (HUSLAB) were compiled: the patient panel (N=70) included sera from PCR confirmed COVID-19 patients, and the negative panel (N=81) included sera sent for screening of autoimmune diseases and respiratory virus antibodies in 2018 and 2019. The MNT was carried out for all COVID-19 samples (70 serum samples, 62 individuals) and for 53 samples from the negative panel. Forty-one out of 62 COVID-19 patients showed neutralising antibodies.The specificity and sensitivity values of the commercial tests against MNT, respectively, were as follows: 95.1 %/80.5 % (Abbott Architect SARS-CoV-2 IgG), 94.9 %/43.8 % (Diasorin Liaison SARS-CoV-2 IgG; RUO), 68.3 %/87.8 % (Euroimmun SARS-CoV-2 IgA), 86.6 %/70.7 % (Euroimmun SARS-CoV-2 IgG), 74.4 %/56.1 % (Acro 2019-nCoV IgG), 69.5 %/46.3 % (Acro 2019-nCoV IgM), 97.5 %/71.9 % (Xiamen Biotime SARS-CoV-2 IgG), and 88.8 %/81.3 % (Xiamen Biotime SARS-CoV-2 IgM). This study shows variable performance values. Laboratories should carefully consider their testing process, such as a two-tier approach, in order to optimize the overall performance of SARS- CoV-2 serodiagnostics.

Viral haemorrhagic fevers in the Middle East

Viral haemorrhagic fevers (VHFs) are a group of infectious, devastating and severe diseases caused by enveloped single-stranded RNA viruses. The endemicity, emergence or re-emergence of different VHF viruses and lack of vaccines and antiviral therapy for most VHFs result in a significant global threat. Most VHF viruses are restricted to specific parts of the world, and the dramatic expansion of their geographical distribution beyond their original habitats would greatly affect global public health. In the past few decades alone, several outbreaks have affected the Middle East, a part of the world containing arid to semi-arid, hot and water-scarce countries. Political instability, natural and humanitarian crises, direct contact with domesticated animals and climate change are the main factors in the dissemination of different zoonotic diseases, including vector-borne diseases. Some VHF viruses have been introduced into the Middle East (e.g. Alkhurma haemorrhagic fever) and others have been re-introduced and have become endemic in the region. Dengue fever, Crimean Congo haemorrhagic fever, Rift Valley fever and hantavirus haemorrhagic fever with renal syndrome are examples of re-emerging or endemic viruses in the region. The temporal and spatial extension of VHF distribution mandates a particular engagement from all the actors in the fields of animal, human and environmental health. The One Health concept is a multidisciplinary and multisectoral approach for promoting collaboration, coordination and communication among different nations, sectors and disciplines, which is highly relevant to the fight against endemic, emerging and re-emerging infectious agents at the human-animal-environment interface. The adoption of the One Health approach is a promising solution to addressing public health threats in the Middle East.

Human leucocyte antigens B*08, DRB1*03 and DRB1*13 are significantly associated with autoimmune liver and biliary diseases in Finnish children

AIM

The human leucocyte antigen (HLA) allele and haplotype frequencies of the Finnish population are unique because of the restricted and homogenous gene population. There are no published data on HLA genotype associations in paediatric autoimmune liver diseases in Scandinavia. This study characterised the HLA genotypes of children with autoimmune liver or biliary disease in Finland.

METHODS

The study cohort comprised 19 paediatric patients (13 female) aged three years to 15 years treated for autoimmune liver or biliary disease at the Children's Hospital, Helsinki University Hospital, between 2000 and 2011, and followed up for four years and three months to 14.6 years. We genotyped HLA-B and HLA-DRB1 in the children, and the HLA antigen frequencies were compared with 19 807 records from the Finnish Bone Marrow Donor Registry.

RESULTS

All paediatric patients with autoimmune liver or biliary disease had either autoimmune HLA haplotype B*08;DRB1*03 or DRB1*13. These were significantly more common among patients with autoimmune hepatitis, primary sclerosing cholangitis and autoimmune hepatitis/primary sclerosing cholangitis overlap syndrome than the Finnish control population. HLA RB1*04 was not found in the study cohort.

CONCLUSION

Our study found that B*08, DRB1*03 and DRB1*13 were significantly associated with autoimmune liver and biliary diseases in Finnish paediatric patients.

Hepatitis E Virus Antibodies in Finnish Veterinarians

We investigated hepatitis E virus (HEV) infections in Finnish veterinarians engaged in different practice specialties and evaluated the effect of different background factors on HEV exposure by examining total HEV antibodies in samples collected from the participants of the 2009 National Veterinary Congress in Helsinki, Finland. Finnish veterinarians commonly have total HEV antibodies with seroprevalence of 10.2%. Of the non-veterinarians, 5.8% were seropositive. Increasing age was associated with HEV seropositivity, and, surprisingly, the highest HEV seroprevalence (17.8%) among veterinarians was detected among small animal practitioners. Although no positive correlation between swine contacts and HEV seropositivity was found, 22.7% of veterinarians who had had needle stick by a needle that had previously been injected into a pig versus 9.0% of those who had not were seropositive, even though the finding was statistically non-significant (P = 0.07). Our results suggest that, although contact with swine is a known risk factor for HEV infection, the sources of HEV infections are probably numerous, including travelling abroad and possibly also other reservoirs of HEV than pigs.

Incidence and seroprevalence of tularaemia in Finland, 1995 to 2013: regional epidemics with cyclic pattern

We studied the incidence of reported tularaemia by year and region and the prevalence of antibodies against Francisella tularensis in the adult general population in Finland. Moreover, we assessed the correlation between vole population cycles and human tularaemia outbreaks. The seroprevalence study made use of serum samples from a nationwide population-based health survey (Health 2000). The samples of 1,045 randomly selected persons, representative for the Finnish population in each region, were screened with an enzyme-linked immunosorbent assay (ELISA) for the presence of IgG antibodies against F. tularensis, and positive results were further confirmed by immunoblotting. A serological response to F. tularensis was found in 2% (95% confidence interval: 1.1–3.5) of the population. Incidence and seroprevalence were highest in the same areas, and vole population peaks clearly preceded tularaemia outbreaks one year later.

Anticancer compound ABT-263 accelerates apoptosis in virus-infected cells and imbalances cytokine production and lowers survival rates of infected mice

ABT-263 and its structural analogues ABT-199 and ABT-737 inhibit B-cell lymphoma 2 (Bcl-2), BCL2L1 long isoform (Bcl-xL) and BCL2L2 (Bcl-w) proteins and promote cancer cell death. Here, we show that at non-cytotoxic concentrations, these small molecules accelerate the deaths of non-cancerous cells infected with influenza A virus (IAV) or other viruses. In particular, we demonstrate that ABT-263 altered Bcl-xL interactions with Bcl-2 antagonist of cell death (Bad), Bcl-2-associated X protein (Bax), uveal autoantigen with coiled-coil domains and ankyrin repeats protein (UACA). ABT-263 thereby activated the caspase-9-mediated mitochondria-initiated apoptosis pathway, which, together with the IAV-initiated caspase-8-mediated apoptosis pathway, triggered the deaths of IAV-infected cells. Our results also indicate that Bcl-xL, Bcl-2 and Bcl-w interact with pattern recognition receptors (PRRs) that sense virus constituents to regulate cellular apoptosis. Importantly, premature killing of IAV-infected cells by ABT-263 attenuated the production of key pro-inflammatory and antiviral cytokines. The imbalance in cytokine production was also observed in ABT-263-treated IAV-infected mice, which resulted in an inability of the immune system to clear the virus and eventually lowered the survival rates of infected animals. Thus, the results suggest that the chemical inhibition of Bcl-xL, Bcl-2 and Bcl-w could potentially be hazardous for cancer patients with viral infections.

Imported dengue virus serotype 1 from Madeira to Finland 2012

Imported dengue cases originating from the Madeiran outbreak are increasingly reported. In 2012 five Finnish travellers returning from Madeira were diagnosed with dengue fever.

Imported dengue virus serotype 1 from Madeira to Finland 2012

Imported dengue cases originating from the Madeiran outbreak are increasingly reported. In 2012 five Finnish travellers returning from Madeira were diagnosed with dengue fever. Viral sequence data was obtained from two patients. The partial C-preM sequences (399 and 396 bp respectively) were found similar to that of an autochthonous case from Madeira. The partial E-gene sequence (933 bp) which was identical among the two patients grouped phylogenetically with South American strains of dengue virus serotype 1.

Japanese encephalitis virus RNA detected in Culex pipiens mosquitoes in Italy

Mosquitoes collected in northern Italy were screened for flavivirus RNA. Positive amplicons were sequenced and found most similar to insect flavivirus (ISF), Usutu virus (USUV) and surprisingly also to Japanese encephalitis virus (JEV). The sequence (167 bp), obtained from one pool of Culex pipiens, was found identical to JEV strains from bats in China. Unfortunately additional sequence data or virus isolations were not obtained in this study. Confirmation of potential introduction of JEV to Italy and other European countries is urgently needed.

Cytoplasmic tails of hantavirus glycoproteins interact with the nucleocapsid protein

Here we characterize the interaction between the glycoproteins (Gn and Gc) and the ribonucleoprotein (RNP) of Puumala virus (PUUV; genus Hantavirus, family Bunyaviridae). The interaction was initially established with native proteins by co-immunoprecipitating PUUV nucleocapsid (N) protein with the glycoprotein complex. Mapping of the interaction sites revealed that the N protein has multiple binding sites in the cytoplasmic tail (CT) of Gn and is also able to bind to the predicted CT of Gc. The importance of Gn- and Gc-CTs to the recognition of RNP was further verified in pull-down assays using soluble peptides with binding capacity to both recombinant N protein and the RNPs of PUUV and Tula virus. Additionally, the N protein of PUUV was demonstrated to interact with peptides of Gn and Gc from a variety of hantavirus species, suggesting a conserved RNP-recognition mechanism within the genus. Based on these and our previous results, we suggest that the complete hetero-oligomeric (Gn-Gc)(4) spike complex of hantaviruses mediates the packaging of RNP into virions.

Recent expansion of dengue virus serotype 3 in West Africa

Due to non-existing or limited surveillance in Africa, little is known about the epidemiology of dengue illness in the continent. Serological and virological data obtained from returning European travellers is a key complement to this often flawed information. In the past years, dengue 3 virus has emerged in West Africa and has been detected in travellers returning to Europe. The first dengue epidemic in Cape Verde with more than 17,000 cases from September to December 2009 demonstrated that dengue virus is still expanding worldwide to new territories.

Recent expansion of dengue virus serotype 3 in West Africa

Due to non-existing or limited surveillance in Africa, little is known about the epidemiology of dengue illness in the continent. Serological and virological data obtained from returning European travellers is a key complement to this often flawed information. In the past years, dengue 3 virus has emerged in West Africa and has been detected in travellers returning to Europe. The first dengue epidemic in Cape Verde with more than 17,000 cases from September to December 2009 demonstrated that dengue virus is still expanding worldwide to new territories.

Epidemiological analysis of mosquito-borne Pogosta disease in Finland, 2009

Pogosta disease is a viral disease caused by a mosquito-borne alphavirus, Sindbis virus (SINV), and large human outbreaks of SINV infection have emerged in Finland every seven years. After a major outbreak in 2002 an epidemic was expected to take place in 2009. Data from the National Infectious Disease Registry showed a small outbreak in humans in 2009 with a total of 105 reported cases but the seven-year cycle did not recur as anticipated.

Gadolinium enhancement of cauda equina: a new MR imaging finding in the radiculitic form of tick-borne encephalitis

Tick-borne encephalitis virus is an important human pathogen in Europe. The infection usually presents as meningitis, meningoencephalitis, or meningoencephalomyelitis and only rarely as symptoms of isolated myeloradiculitis. We describe the lumbar MR imaging finding in a 48-year-old man with serologically confirmed tick-borne encephalitis in which there was enhancement of the ventral surface of the conus and the anterior nerve roots from the T12 level extending along the length of the ventral cauda.

Hantavirus and arenavirus antibody prevalence in rodents and humans in Trentino, Northern Italy

The spatial and temporal distribution of hantavirus and arenavirus antibody-positive wild rodents in Trentino, Italy, was studied using immunofluorescence assays (IFA) in two long-term sites trapped in 2000-2003, and six other sites trapped in 2002. The overall hantavirus seroprevalence in the bank voles, Clethrionomys glareolus (n=229) screened for Puumala virus (PUUV) antibodies was 0.4%, and that for Apodemus flavicollis mice (n=1416) screened for Dobrava virus (DOBV) antibodies was 0.2%. Antibodies against lymphocytic choriomeningitis virus (LCMV) were found in 82 (5.6%) of the 1472 tested rodents; the seroprevalence being 6.1% in A. flavicollis (n=1181), 3.3% in C. glareolus (n=276), and 14.3% in Microtus arvalis (n=7). Of the serum samples of 488 forestry workers studied by IFA, 12 were LCMV-IgG positive (2.5%) and one DOBV-IgG positive (0.2%), however, the latter could not be confirmed DOBV-specific with a neutralization assay. Our results show a widespread distribution but low prevalence of DOBV in Trentino, and demonstrate that the arenavirus antibodies are a common finding in several other rodent species besides the house mouse.

Is there an association ofPneumocystisinfection with the presence of arena-, hanta-, and poxvirus antibodies in wild mice and shrews in Finland?

As part of studies on the nature of the endemic virus infections in natural rodent hosts, the possible association of cyst forms ofPneumocystisspp. with the presence of hanta-, cowpox-, and arenavirus antibodies in wild mice (Apodemus flavicollis,N=105;Apodemus agrarius,N=63;Micromys minutus,N=50) and the common shrew (Sorex araneus,N=101) was studied in south-central Finland. One hantavirus (Saaremaa virus, SAAV) seropositiveA. agrarius, and 2 cowpoxvirus (CPXV) seropositiveS. araneuswere detected, and antibodies against an arenavirus (Lymphocytic choriomeningitis virus, LCMV) were found in all 3 mouse species but not in shrews. Cyst forms ofPneumocystisspp. were detected in all species exceptA. agrarius. There was no significant association between virus antibodies (LCMV in mice, and CPXV in shrews) and cyst forms ofPneumocystisin any of the species. Concurrent presence of virus antibodies (LCMV) and cyst forms ofPneumocystiswere detected only in 1M. minutus. In conclusion, we found no evidence of any association betweenPneumocystisand antibodies to any of the viruses tested.

Rapid field test for detection of hantavirus antibodies in rodents

Puumala virus (PUUV) is the causative agent of nephropathia epidemica, a mild form of haemorrhagic fever with renal syndrome. PUUV is transmitted to humans via aerosolized excreta of the infected bank vole (Clethrionomys glareolus). Current methods for screening of the PUUV prevalence among bank vole populations are laborious, combining sampling in the field and subsequent analyses in the laboratory. In order to facilitate animal testing, a new serological immunochromatographic rapid test was developed. The test uses PUUV nucleocapsid protein as antigen, and it detects anti-PUUV IgG antibodies in rodents. With fresh and undiluted bank-vole blood samples (n = 105) the efficacy of the test was 100%, and with frozen and diluted samples (n = 78) the efficacy was 91%. The test was also shown to detect related hantavirus infections in Norway lemmings and sibling voles (n = 31) with 99% efficacy. The test provides an applicable tool for studying PUUV and related hantavirus infections in arvicoline rodents.

Patterns of Puumala virus infection in Finland

Puumala hantavirus infection is prevalent throughout most of Europe, and in endemic areas it may be the most common cause of acute renal failure. To evaluate trends in incidence of Puumala virus infections in Finland, we analysed national surveillance data in 12-month periods from March 1995 to February 2002. During this time, 8184 laboratory-confirmed cases were notified to the National Infectious Disease Register. Three epidemic periods were identified, for which the number of cases was more than 1400 (there were approximately 600-900 cases per non-epidemic period). The incidence of Puumala hantavirus infection varied by geographic region during the study period, and the overall number of cases may be increasing.

Epidemiology of Sindbis virus infections in Finland 1981-96: possible factors explaining a peculiar disease pattern

Pogosta disease (PD), an epidemic rash-arthritis occurring in late summer is caused by Sindbis virus (SINV) and is transmitted to humans by mosquitoes. Altogether 2183 PD cases were serologically confirmed 1981-96 in Finland, with an annual incidence of 2.7/100000 (18 in the most endemic area of Northern Karelia). The annual average was 136 (varying from 1 to 1282) with epidemics occurring in August-September with a 7-year interval. Studies on 6320 patients with suspected rubella (1973-89) revealed 107 PD cases. The depth of snow cover and the temperature in May-July seemed to predict the number of cases. The morbidity was highest in 45- to 65-year-old females and lowest in children. Subclinical SINV infections were 17 times more common than the clinical ones. The SINV-antibody prevalence in fertile-age females was 0.6% in 1992; the estimated seroprevalence in Finland is about 2%. Among game animals the tetraonids (black grouse and capercaillie) had the highest seroprevalence (65%) in the epidemic year of 1981.

Comparison of a new immunochromatographic rapid test with a commercial EIA for the detection of Puumala virus specific IgM antibodies

BACKGROUND

Hantaviruses are associated with two human diseases: haemorrhagic fever with renal syndrome (HFRS) and Hantavirus pulmonary syndrome (HPS). Puumala virus (PUUV), which is one of the Hantaviruses, is a causative agent of nephropathia epidemica (NE), a mild form of HFRS.

OBJECTIVE

a new 5 min rapid test, POC PUUMALA (Erilab Ltd, Finland), for detecting IgM antibodies to PUUV was evaluated and compared with the commercially available Hantavirus (Puumala) IgM ELISA test (Progen, Germany). Discrepant test results between the two tests were confirmed by a mu-capture reference EIA.

STUDY DESIGN

Two hundred and thirty five serum samples, which had earlier been analyzed with the Progen IgM ELISA, were assayed with the POC PUUMALA rapid test. Five persons, without knowing the Progen IgM ELISA test results, interpreted independently the rapid test results. In addition, a panel of 48 serum samples was analyzed in parallel with the rapid test and the Progen IgM ELISA by one technician in daily routine diagnostics in a clinical microbiology laboratory.

RESULTS

the agreement between the results of the five interpreters was 95%, and the congruence of the results between individual readers and commercial ELISA test varied from 93 to 96%. Diagnostic efficacy of the rapid test varied between 98 and 99% compared with 96% of the Progen IgM ELISA. The POC PUUMALA rapid test showed higher or similar sensitivity compared with the Progen IgM ELISA, whereas both the tests had similar levels of specificity.

CONCLUSIONS

the analytical performance of the POC PUUMALA rapid test was found to be as good or even slightly better than the analytical performance of the Progen IgM ELISA. In addition, the rapid and straightforward procedure makes the POC PUUMALA a feasible tool for the diagnosis of the acute PUUV infection.

Human immune response to Puumala virus glycoproteins and nucleocapsid protein expressed in mammalian cells

Puumala hantavirus (PUUV) glycoproteins G1 and G2 and nucleocapsid protein (N) were expressed in BHK-21 cells by transfection of a plasmid producing a recombinant alphavirus replicon. Coexpression of G1 and G2 from separate constructs seemed to be important for the optimal folding of the glycoproteins, as evaluated by a panel of MAbs detecting conformational epitopes. To evaluate the human antibody response against recombinant G1, G2 and N, several panels of sera were tested by immunofluorescence assay (IFA). Also human sera showed the best reactivity towards G1 and G2 coexpressed from separate transcripts (G1 + G2). Notably, only 2% of the acute sera (total number = 133) contained IgG antibodies against G1 + G2, whereas of old-immunity sera (total number = 100) 87% were G1 + G2 positive. Analysis of a panel of serial patient sera showed that as the immunity matured, IgG antibodies against the recombinant glycoproteins appeared and the titers increased in the course of time, while antibodies against the recombinant N were present already in the acute phase in high titers. The granular fluorescence pattern in PUUV IgG-IFA, associated with the acute phase of immunity, was linked to the presence of antibodies against N, whereas the diffuse fluorescence pattern associated with old-immunity, was linked to the development of antibodies against G1 + G2. The granular fluorescence pattern in PUUV IgG-IFA had a predictive value of 100% for acute PUUV infection. Weak cross-reaction with PUUV glycoproteins was observed in 36% of old-immunity DOBV-specific human sera.

New immunochromatographic rapid test for diagnosis of acute Puumala virus infection

A new immunochromatographic rapid test, POC PUUMALA (Erilab Ltd., Kuopio, Finland), for detection of acute-phase Puumala virus (PUUV) infection was developed based on a highly purified baculovirus-expressed PUUV nucleocapsid protein antigen and lateral immunodiffusion techniques. After addition of sample (5 microl of serum, plasma, or fingertip blood) and buffer, PUUV-specific immunoglobulin M (IgM) antibodies, if present, together with the gold-conjugated anti-human IgM, formed a specific colored line in 5 min. The sensitivity and specificity of the test were evaluated with 200 serum samples and 30 fingertip blood samples. The reference method for the serum samples was a micro-capture enzyme immunoassay (EIA) for IgM and an immunofluorescence assay (IFA) for IgG antibodies. The analytical sensitivity and specificity of the rapid test were 100 and 99%, respectively, for unfrozen serum samples (n = 103; 12 PUUV IgM-positive samples). When freeze-thawed serum samples were used, the sensitivity and specificity were each 97.1% (n = 70; 35 PUUV IgM-positive samples). The specificity of the test was 96.2% for 27 serum samples with nonspecific IgM antibodies or rheumatoid factor (RF). The fingertip blood samples (n = 30) were negative, but they gave clear positive results when spiked with IgM-positive sera (n = 20). The results were in good agreement with the standard diagnostic methods. The rapid performance, the lack of need for refined laboratory equipment, and the high specificity with fresh serum and fingertip blood samples indicate that the developed POC PUUMALA rapid test is a useful tool for fast diagnosis of acute PUUV infection.

Isolation of Dobrava virus from Apodemus flavicollis in Greece

Dobrava virus (DOBV) carried by Apodemus flavicollis is the causative agent of severe hemorrhagic fever with renal syndrome (HFRS). DOBV was isolated from an A. flavicollis mouse trapped in northeastern Greece. This is the third DOBV cell culture isolate in the world, clustering together with other Greek DOBV sequences from HFRS patients and rodents.

Polymorphism of the cytokine genes in hospitalized patients with Puumala hantavirus infection

BACKGROUND

Nephropathia epidemica (NE) is a mild type of haemorrhagic fever with renal syndrome caused by Puumala (PUU) hantavirus. The clinical course of NE varies from asymptomatic to fatal. The aim of this study was to establish whether polymorphisms in the cytokine genes are associated with susceptibility to and outcome of NE.

METHODS

The genotypes of the genes of tumour necrosis factor alpha (TNFalpha), interleukin-1alpha (IL-1alpha), IL-1beta and IL-1 receptor antagonist (IL-1RA) were analysed by polymerase chain reaction in 87 subjects, all hospital-treated for serologically confirmed acute NE. The control group comprised 400 healthy blood donors. Nineteen out of these 400 (5%) controls were PUU virus-seropositive.

RESULTS

IL-1RA allele 2 and IL-1beta (base exchange polymorphism at position -511) allele 2 were strongly associated with each other in both groups. NE patients were more often IL-1RA-2 negative/IL-1beta-2 negative than PUU-seronegative blood donors (38 vs 27%, odds ratio 1.65, 95% confidence interval 1.0-2.7). However, there were no differences in the clinical severity of NE between the IL-1RA-2 negative/IL-1beta-2 negative and the other patients. The other allele frequencies studied evinced no statistically significant differences between the groups. Thirty-three out of 87 (38%) patients and 121 out of 381 (32%) seronegative controls were carriers of the high-producer genotype TNF2 allele. Several parameters showed the clinical course of NE to be more severe in TNF2 carriers than in non-carriers.

CONCLUSIONS

These data suggest that non-carriage of the IL-1RA allele 2 and IL-1beta (-511) allele 2 may contribute to susceptibility to NE. Furthermore, TNFalpha polymorphism seems to be associated with the outcome of NE.

Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in Finland

Approximately 20 cases of tick-borne encephalitis (TBE) occur annually in Finland. The known endemic areas are situated mainly in the archipelago and coastal regions of Finland, with highest incidence in Aland islands. Ixodes ricinus panels collected in 1996-1997 from two endemic areas were screened for the presence of RNA. Two distinct RT-PCR methods were applied, and were shown to have an approximate detection limit of 10 focus forming doses (FFD)/100 microl. One out of 20 pools (a total of 139 ticks) from Helsinki Isosaari Island and one out of 48 pools (a total of 450 ticks) from Aland were positive with both methods, whereas the remaining pools were negative. The observed overall frequency (0.34%) in ticks in endemic areas of Finland, was similar to the low incidence found by virus isolation in mice in the 1960s (0.5%). Viral RNA was detectable in a diluted sample representing 0.005% of a positive pool of ten nymphs suggesting that the viral RNA load within an infected tick pool was approximately equivalent to 20,000-200,000 FFD. Sequence analysis did not show geographical clustering of the Finnish strains, suggesting an independent emergence of different TBE foci from the south. TBE virus RNA positive ticks were not found in I. ricinus panels consisting of 130 pools (726 ticks) from Helsinki city parks or 41 pools (197 ticks) from Võrmsi Island in Estonia.

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.

Antigenic properties and diagnostic potential of recombinant dobrava virus nucleocapsid protein

Dobrava hantavirus (DOBV) causes severe hemorrhagic fever with renal syndrome in the Balkan region and has been detected recently also in Russia, Estonia, and Germany. DOBV nucleocapsid protein (N) was produced in insect cells, using the baculovirus expression system (bac-DOBV-N), and in E. coli as a truncated (aa 1-165) glutathione-S transferase fusion protein (DOBV-dN-GST). The antigenic properties of bac-DOBV-N were found identical to native DOBV-N when examined by a panel of hantavirus-specific monoclonal antibodies. Enzyme immunoassays for detection of IgM and IgG antibodies were set up using DOBV recombinant N proteins and compared with those based on recombinant Hantaan and Puumala virus N, using panels of sera collected from DOBV, Hantaan and Puumala virus-infected patients. Full-length N protein (bac-DOBV-N) was found to be a more sensitive antigen than DOBV-dN-GST. The sensitivity values for sera from DOBV-infected patients were 100% for bac-DOBV-N and 86% for DOBV-dN-GST by IgM assays, and 98% for bac-DOBV-N and 88% for DOBV-dN-GST by IgG assays. The specificity values were 100% for bac-DOBV-N and 99% for DOBV-dN-GST by IgM assays, and 100% for both antigens by IgG assays.

Systemic inflammation in hemorrhagic fever with renal syndrome correlates with hypotension and thrombocytopenia but not with renal injury

Systemic inflammation is common in patients with nephropathia epidemica (NE), a European form of hemorrhagic fever. Markers of inflammation were studied in a patient with NE with respiratory insufficiency (patient 1), 18 other patients with NE, and 13 patients with a viral infectious disease other than NE. Neutrophil and monocyte CD11b expression levels, determined by flow cytometry; soluble interleukin (IL)-2 receptor (sIL-2R), IL-6, and IL-8 concentrations, determined by means of Immulite; and soluble E-selectin, determined by ELISA, were higher in patients with NE than in healthy subjects. The findings were not specific for NE and did not correlate with serum creatinine levels, but the findings correlated inversely with mean arterial pressure (sIL-2R and monocyte CD11b expression) and minimum platelet count (sIL-2R, IL-6, neutrophil, and monocyte CD11b expression). Monocyte CD11b expression in patient 1 was extremely high, suggesting that monocytes may contribute to development of lung injury. Severity of inflammation in patients with NE is related to hypotension and platelet consumption but not to renal injury.

Epidemiological study of nephropathia epidemica in Finland 1989-96

This study presents data on 33,000 serum samples studied from July 1989 to June 1996 in Finland, with 6,701 serologically confirmed Puumala virus (PUU) infections. In addition, a PUU serosurvey of 8,000 sera from Finland is presented. On average, 957 PUU infections were detected annually, resulting in an incidence of 19/100,000; mortality was less than 0.1%. The infection was most common in the district of Ita-Savo with an incidence of 90/100,000. The seasonal peak was in November-December; however, the urban population had its incidence peak in August. Local epidemics mirrored bank vole densities, with 3-4-y cycles. Males contracted the disease at a mean age of 40 y, females at 44 y (male:female ratio 2:1). The disease was relatively rare in children and elderly people. The nationwide PUU antibody prevalence for women entering Finnish maternity clinics was 3%, suggesting 5% for the total population. The highest prevalences (7% for young women) were encountered in eastern Finland. In the district with the highest clinical alert, approximately 30% of all PUU infections were estimated to lead to clinical disease with serological confirmation.

Isolation and characterization of a hantavirus from Lemmus sibiricus: evidence for host switch during hantavirus evolution

A novel hantavirus, first detected in Siberian lemmings (Lemmus sibiricus) collected near the Topografov River in the Taymyr Peninsula, Siberia (A. Plyusnin et al., Lancet 347:1835-1836, 1996), was isolated in Vero E6 cells and in laboratory-bred Norwegian lemmings (Lemmus lemmus). The virus, named Topografov virus (TOP), was most closely related to Khabarovsk virus (KBR) and Puumala viruses (PUU). In a cross focus reduction neutralization test, anti-TOP Lemmus antisera showed titers at least fourfold higher with TOP than with other hantaviruses; however, a rabbit anti-KBR antiserum neutralized TOP and KBR at the same titer. The TOP M segment showed 77% nucleotide and 88% amino acid identity with KBR and 76% nucleotide and 82% amino acid identity with PUU. However, the homology between TOP and the KBR S segment was disproportionately higher: 88% at the nucleotide level and 96% at the amino acid level. The 3' noncoding regions of KBR and the TOP S and M segments were alignable except for 113- and 58-nucleotide deletions in KBR. The phylogenetic relationships of TOP, KBR, and PUU and their respective rodent carriers suggest that an exceptional host switch took place during the evolution of these viruses; while TOP and KBR are monophyletic, the respective rodent host species are only distantly related.