[Development of purified HFRS bivalent vaccine]

AIM

To develop the purified HFRS bivalent vaccine.

METHODS

LR1 (type I) and R22 (type II) of HFRS virus were cultured respectively in Vero cells. The viral suspensions were harvested, inactivated with beta-propiolactone, concentrated by ultra-filtration, purified by zone centrifugation, and desucrosed by column chromatography. The qualified vaccine bulks of type I and type II were mixed equally and absorbed with AI(OH)3 for preparation of 3 lots vaccines.

RESULTS

The 3 lots vaccines all passed examination carried out by ourselves and reexamination performed by National Institute for the Control of Pharmaceutical and Biological Products . One of 3 lots has been used in clinical trial.

CONCLUSION

It is practical to develop the purified HFRS bivalent vaccine by Vero cell culture.

[Identification of oligopeptides mimicking the virus attachment protein of hantaan virus]

OBJECTIVE

To identify and characterize the epitope associated with the virus attachment protein (VAP) of hantaan virus.

METHODS

The monoclonal antibody 3G1 was used as the ligand to biospan from a phage-displayed 12-amino acid peptide library, then the positive phage clones were chosen and sequenced. The amino acid sequences of them were compared with that of hantaan virus G2 in homology. The characteristics of positive phage were studied by IFA and ELISA. A decapeptide combining to cell membrane was observed under laser scanning confocal microscope (LSCM).

RESULTS

The conservative motif PX(1-2) HX(0-2) H displaying on positive clones shared homologous amino acid sequence with G2 96YPWHTAKCHY105.

CONCLUSION

G2 96YPWHTAKCHY105 might play some roles in virus binding to host cell, and might be a possible key epitope of hantaan virus VAP.

[The relationship between cellular infection by Hantaan virus and expression of beta3 integrin]

OBJECTIVE

To investigate the relationship between cellular entry of Hantaan virus (HTNV) and expression of beta3 integrin in beta3-integrin-deficient and HTNV-insusceptible China hamster ovary (CHO) cells.

METHODS

Eukaryotic expression vector encoding human integrin beta3 and eukaryotic expression vector harboring human integrin alphav or alphaIIb subunit cDNA were transfected into HTNV non-permissive CHO cells individually or collectively. Screening for stable transfectant clones was performed using G418 selective (culture medium. The exogenous gene expression was analyzed qualitatively and quantitatively by immunofluorescence assay (IFA) and flow cytometry (FCM). Various modified CHO cells and untransfected CHO cells were infected using HTNV A9. At various time points after infection, HTNV antigens in infected cells were detected qualitatively and quantitatively by IFA, FCM.

RESULTS

Highly-effective surface expression of beta3 integrin was measured in CHO/alphavbeta3 and CHO/alphaIIbbeta3, while weaker surface expression was detected in CHO/beta3 (P < 0.05). Expression of alphav or alphaIIb integrin in the individually transfected group was significantly lower than in the cotransfected group (P < 0.01) and the sites of localization changed. In contrast, effective surface expression was not seen when pcDNA3 was transfected alone. The infection rate of CHO/alphavbeta3 (60.1%) and CHO/alphaIIbbeta3 (55. 9%) cells were significantly higher than that of CHO/beta3 (38.7%) cells, while the infection rate of CHO/beta3 was significantly higher than that of CHO/alphav, CHO/pcDNA3 and CHO cells respectively. There was a close relationship between the positive percentage of HTNV A9-infected cells and expression of beta3 integrin.

CONCLUSION

These results indicated that cellular entry of HTNV was related to the expression of beta3 integrin.

[Complex evaluation of endemicity level of the territory affected by hemorrhagic fever with renal syndorome]

A new formula for the calculation of the endemicity index of the territory affected by hemorrhagic fever with renal syndrome (HFRS) based on empiric data collected in the Volga region near Saratov in 1982-2000 is proposed. As found in this research 21% of the administrative districts of the region have a high endemicity level (with the average index for several years reaching 35 points), 8% of the districts have a medium enemicity level (20 points) and 71% of the districts--a low endemicity level (9 points). It is pointed out that under conditions of financial constraints territories with high and medium endemicity levels should be first examined for HFRS; these territories should also be given priority in prophylactic deratization in the field and human settlements.

[Screening and identification of mimic epitopes of monoclonal antibodies against hantaan virus using phage display technique]

AIM

To obtain mimic epitopes of monoclonal antibody (mAb) against Hantaan virus, and identify preliminarily their immunological characteristics.

METHODS

Group-specific mAbs F3 and B11 were used as selective molecules for biopanning. After biopanning, the positive phages were identified by ELISA and DNA sequencing. Among the positive phages, F3-8, B11-18, B11-20 and B11-24 were selected to immunize BALB/c mice three times, respectively. The antiserum was then titered and confirmed by sandwich ELISA and competition ELISA.

RESULTS

After 3 to 4 rounds of effective screening, the majority of the selected clones were found able to react to mAb F3 or B11 in a dose-dependent manner, but not to BSA, rHBsAg or other unrelated mAbs. The amino acid sequences of the clones binding to mAb F3 contained an identical sequence MHGPTKNQMWHT, which had higher homology to 750-759 amino acids between a pair of cysteines within glycoprotein G2 of HTNV/SEOV, while those of clones binding to mAb B11 had no evident homologous regions within HTNV/SEOV proteins. The specific antibodies increased significantly following immunization with phage peptides, which indicated that the phage-displayed peptides had not only good antigenicity, but also strong immunoreactivity.

CONCLUSION

The phage-displayed peptides could mimic the epitope of HFRSV antigen, which would provide the potential for preparing more effective epitope-based vaccines and specific diagnostic reagents.

A new model of Hantaan virus persistence in mice: the balance between HTNV infection and CD8(+) T-cell responses

We established a viral persistence model that involves the adoptive transfer of spleen cells from immunocompetent mice (H-2(d)) into Hantaan virus (HTNV)-infected severe combined immunodeficient (SCID, H-2(d)) mice. The infection is maintained despite the presence of neutralizing antibodies, without apparent signs of disease, and there is a correlation between HTNV persistence and the lack of HTNV-specific CD8(+) T cells. In addition, disseminated HTNV infection before the initiation of immune responses appears to be important for virus persistence. The suppression of HTNV-specific CD8(+) T cells in the present model appears to occur at the periphery. The present study also demonstrates that CD8(+) T cells contribute to the clearance of HTNV. Thus, it seems that HTNV-specific CD8(+) T cells play a key role in HTNV persistence in mice. This model of viral persistence is useful for studies of immune responses and immunocytotherapy against viral infection.

[The epidemic characteristics and preventive measures of hemorrhagic fever with syndromes in China]

OBJECTIVE

To summarize and analyze the epidemic situation of hantaviruses including geographic distribution, types and prevalent intensity of epidemic areas of hantavirus for the last 30 years in China, and to discuss relative preventive measures.

METHODS

Collecting and analyzing the data of hantaviruses epidemics in China.

RESULTS

The annual number of cases of hantavirus disease rapidly increased from 3295 in 1970 to 115,804 in 1986 then sustained between 40,000 and 60,000 cases annually in the 1990's, and then decreased thereafter. The epidemic areas existed in all provinces except Qinhai and Xinjiang and there were the hospitalized cases of hantavirus disease reported in other provinces. In recent years, the prevalence of hantavirus infection had increased in some cities, and the seasonal distribution of the cases changed as well.

CONCLUSION

Data suggested that the new epidemic characteristics of hantaviruses had emerged in China suggesting that it was necessary to strengthen surveillance programs and to take comprehensive preventive measures for the control and prevention of hantaviruses in China.

[Serological surveillance on vaccine against hemorrhagic fever with renal syndrome]

OBJECTIVE

To observe the serological and epidemiological efficacy of hemorrhagic fever renal syndrome (HFRS) vaccine in Zhejiang province.

METHODS

Immunofluorescent antibody assay and Mcro-CPE method were used to test specific IgG antibody and the titer of neutralizing antibody.

RESULTS

Two weeks after the injection of the third dose, the sero-conversion rates by both immunofluorescent antibody test (IgG) and neutralization test were 100.0% (67/67) (95% CI: 96.3 - 100.0) and 44.4% (8/18)(95% CI: 22.0 - 69.0) with geometric mean titers (GMTs) 72.1 and 4.6 respectively. The rates of seroconversion of immunofluorescent antibody by immunofluorescence antibody assay (IFA) were 28.6%, 83.3%, 75.0%, 53.1%, 22.6%, 10.0% and 55.0% before reinforcement, two weeks, one year, one year and a half years, two years, three years and five years after reinforcement. The rates of neutralizing antibody seroconversion by the Mcro-CPE method were found as 14.8%, 55.6%, 35.0%, 31.3%, 26.0%, 10.0% and 50.0% respectively. We found some antibody dependent immunization enhancement phenomenon among the inoculated population, but further observation was needed.

CONCLUSION

HFRS vaccine was immunologically effective and the duration of serous antibody last long.

Age-dependent hantavirus-specific CD8(+) T-cell responses in mice infected with Hantaan virus

To investigate age-dependent differences in hantavirus-specific CD8(+) T-cell responses, mice were inoculated with 0.1 50% newborn mouse lethal dose of Hantaan virus (HTNV) at 0, 3, 7, 14, or 35 days after birth. HTNV-specific CD8(+) T cells producing gamma interferon (IFN-gamma) were measured on day 30 after HTNV inoculation. Although no IFN-gamma-producing HTNV-specific CD8(+) T cells were detected in most of the mice inoculated with HTNV on day 0 after birth, most mice inoculated at 3, 7, 14, or 35 days had HTNV-specific CD8(+) T cells. The production of tumor necrosis factor alpha (TNF-alpha) by IFN-gamma-producing CD8(+) T cells and the cytotoxic activity against HTNV-infected target cells were similar in immature and adult mice. However, the number of IFN-gamma-producing HTNV-specific CD8(+) T cells was significantly less in mice inoculated with HTNV at 3 days than in older mice. In addition, a strong correlation between HTNV persistence and a lack of HTNV-specific CD8(+) T cells was observed. These results suggest that mice over 7 days old have the ability to induce functional HTNV-specific CD8(+) T-cell responses that are indistinguishable from the responses of adult mice, and that HTNV-specific CD8(+) T cells are important for clearance of HTNV.

[Experimental study on enzyme dot assay for detection of hemorrhagic fever with renal syndrome antigen]

OBJECTIVE

To establish a new and efficient method(IEDA) for detection of hemorrhagic fever with renal syndrome virus (HFRSV) antigen.

METHODS

An immune enzyme dot assay (IEDA) with mixture of three sorts anti-HFRSV-IgG, which was obtained from rabbit vaccinated with EHFV R22, Chen and Hubei strain was employed to detect HFRSV antigen in serum and urine from epidemic hemorrhagic fever (EHF) patients, and compared with indirect immune fluorescence assay (I-IFA), 76 serum samples and 40 urine samples were detected in this study.

RESULTS

The results showed that the total positive rate of HFRSV antigen detected by IEDA was 73.68% in serum and 65.00% in urine, while that detected by I-IFA was 75.00% and 70.00%, respectively. The positive rate in primary phase (within 5 days) of HFRSV antigen detected by IEDA was 94.34% in serum and 83.33% in urine, while that detected by I-IFA was 64.42% and 55.56%, respectively, there was significant difference in both serum and urine detections. Correlation study showed a high correlation in the result of IEDA and I-IFA.

CONCLUSION

The results of this study suggested that the IEDA, as compared with I-IFA, was a more specific, sensitive, rapid and simple method with higher positive rate in primary phase. IEDA could be widely used for early diagnosis of HFRS in hospital at grassroots level.

Quality control measures for the serological diagnosis of hantavirus infections

BACKGROUND

With society's rapidly increasing mobility, patients infected with severe viral infections can become seriously ill at any place in Europe and elsewhere. Improving the diagnostics of these infections is the most important step in detecting the pathogens and dealing with them, and for this purpose, quality control measures are essential tools.

OBJECTIVES

To assess the diagnostic reality for rare hantavirus infections in Europe by (1) running a pre-evaluation panel (four samples, sent out in 1999) to optimise sample preparation and shipping procedure and afterwards (2) starting an External Quality Assurance (EQA) program (20 samples, sent out in 2001).

STUDY DESIGN

All samples sent out had to be tested for the presence of specific IgG and IgM antibodies against hantavirus. For the pre-evaluation panel, four samples were distributed (two samples IgG+/IgM-, one sample IgG-borderline/IgM-, one sample IgG-/IgM-), for the EQA 20 samples (six samples IgG+/IgM+, eight samples IgG+/IgM-, one sample IgG-borderline/IgM-, five samples IgG-/IgM-). Thirteen laboratories took part in the pre-evaluation panel, 18 laboratories participated in the first EQA run.

RESULTS

For the pre-evaluation panel, the participants reported correct results for 64% of the IgG-positive samples (85% excluding borderline-positive sample), and 92% for the IgG-negative sample. IgM testing was correctly negative in all laboratories. For the EQA, the participants reported correct results for 76% of the IgG-positive samples, and 97% correct results for the IgG-negative samples. For the IgM-positive samples, 53% correct results were reported, and 98% correct results for the IgM-negative samples.

CONCLUSIONS

The results presented here prove the importance of quality measures also for viruses only rarely suspected, like hantavirus, and they clearly demonstrate the need for improvement of the existing test systems.

A study on detecting specific antibodies of hemorrhagic fever with renal syndrome and treatment with integrated traditional Chinese and Western medicine

OBJECTIVE

To explore a simple speedy specific and sensitive method to detect specific IgM (sIgM) and IgG (sIgG) antibodies of hemorrhagic fever with renal syndrome (HFRS),and to study the therapeutic effects of integrated traditional Chinese and western medicine on HFRS.

METHODS

The serum of 559 patients with HFRS were tested with colloidal gold immuno-dot assay (CGIDA) for sIgM and sIgG antibodies and compared with enzyme linked immunosorbent assay (ELISA) or indirect fluorescent antibody test (IFAT). One hundred and one patients with HFRS were randomized into treatment group (n=50),treated with Kuhuang Injection, Shenmai Injection and Huangqi Liquid) and control group (n=51),treated with Ribarvirin and Ganlixin Injection).

RESULTS

The positive rate of sIgM detected with CGIDA was 70.8% and the positive rate of sIgG detected with CGIDA was 87.5%. The days for fever decline, symptoms alleviation and sign relief between the treatment group and control group were similar (P>0.05). The days for recovery of kidney function in the control group was less than that in the treatment group (P<0.01). The rate of crossing shock stage in the treatment group was higher than that of the control group (P<0.01).

CONCLUSION

CGIDA was more simple, speedy, specific and sensitive than ELISA or IFAT in detecting the sIgM or sIgG antibodies in serum of patients with HFRS. Although the sensitivity of CGIDA was lower than that of ELISA the CGIDA had no false positive reaction the sensitivity of CGIDA was higher than that of IFAT on detecting IgG. The effect of the treatment group was similar to that of the control group. But the crossing shock stage rate in the treatment group was higher than that of the control group while the control group was better than the treatment group in recovering the kidney function.

Relationship between the clinical features and the viral antigen in the extremity blood of the patients with hemorrhagic fever with renal syndrome

The direct immunogold silver staining (D-IGSS) method was used to detect the viral antigen in the extremity blood of 67 cases of hemorrhagic fever with renal syndrome. The positive rate of viral antigen was the highest during the fever, hypotension and oligouria phrase; and the rate dropped gradually during the polyuria and convalescent phase. It is suggested that clinical staging was positively related with the percentage of the viral antigen positive cells (P < 0.001). It is concluded that the positive rate was related to the extent of the injuries by direct viral attack and immune reaction. The D-IGSS was proved to be fast, simple, economical, with high sensitivity and specificity.

[Surveillance on hemorrhagic fever with renal syndrome in Guizhou during 1984-2000]

OBJECTIVE

To explore the relations between different areas on hemorrhagic fever with renal syndrome (HFRS) in Guizhou.

METHODS

Various forms of infectious areas were surveyed continuously through epidemiologic surveillance system.

RESULTS

In fixed areas under surveillance system, the mean positive rate of HFRSV among Apodemus agrarius was 3.39%, comparing with Rattus norvegicus 1.61% in Apodemus infectious areas of Zunyi county, 3.19% in Rattus norvegicus, but no HFRSV of Apodemus agrarius was identified in Rattus infectious area of Shiqian county. Both Apodemus and Rattus infectious areas were relatively stabilized. In both banks of Luowang river, Kaiyang county, which had been identified as areas of infections for Apodemus in the eastern part, Rattus infectious area in the west, slow change was noticed. In 1983 - 1984 was not found in Apodemus agrarius HFRSV, however the infectious rate of HFRSV in Apodemus agrarius was 13.85% (Ag 1/65, Ab 8/65) in the western part of the province in 1995 - 1998.

CONCLUSION

Both Apodemus and Rattus infectious areas were stabilized but changed slowly. Mixed type and the result of mutual penetration were noticed.

Hantavirus-specific CD8(+)-T-cell responses in newborn mice persistently infected with Hantaan virus

The relationship between virus-specific CD8(+)-T-cell responses and viral persistence was studied in mice by using Hantaan virus (HTNV). We first established a simple method for measuring levels of virus-specific CD8(+) T cells by flow cytometry. Next, to produce a mouse model of persistent HTNV infection, newborn mice were inoculated subcutaneously within 24 h of birth with 1 or 0.1 50% newborn mouse lethal dose of HTNV. All mice that escaped lethal infection were persistently infected with HTNV until at least 30 days after virus inoculation and had no virus-specific CD8(+) T cells producing gamma interferon (IFN-gamma). Subsequently, the virus was eliminated from some of the mice, depending on the appearance of functional virus-specific CD8(+) T cells, which have the ability to produce IFN-gamma and tumor necrosis factor alpha (TNF-alpha) and have cytotoxic activity. Neutralizing antibodies were detected in all mice, regardless of the presence or absence of virus. In the acute phase, which occurs within 30 days of infection, IFN-gamma-producing HTNV-specific CD8(+) T cells were detected on day 15 after virus inoculation. However, TNF-alpha production and the cytotoxic activity of these specific CD8(+) T cells were impaired and HTNV was not removed. Almost all of these specific CD8(+) T cells disappeared by day 18. These results suggest that functional HTNV-specific CD8(+) T cells are important for clearance of HTNV.

[Construction and stable expression of intracellular antibodies to glycoprotein of hantavirus]

OBJECTIVE

To understand the molecular mechanisms of hantavirus assembly and maturation by stably expressing the intracellular antibodies to hantavirus glycoprotein G1 and G2 in endoplasmic reticulum (ER) and cytoplasm (Cyto) of Vero E6 cell.

METHODS

The genes of VH and VL of antibodies against glycoprotein of hantavirus were amplified by PCR and cloned into pOPE 101-215 (Yol) vector. The G1 and G2 proteins specific ScFv genes were first expressed in E.coli and the function and binding properties were identified. The gene of ScFv were further inserted into intracellular expression vectyrs pEF/ myc/ ER and pEF/ myc/ CYTO vector and transfected Vero E6 cell. The clonal cell line which stabl expresses ScFv were isolated under the pressure of G418.

RESULTS

The ScFv genes of hantavirus G1 and G2 specific antibodies were successfully expressed in subcellular compartment ER and Cyto of Vero E6 cells and specifically targeted G1 and G2 protein after virus infection of the cells.

CONCLUSIONS

The recombination of intrabody to Hantann virus glycoprotein was constructed successfully, and it may provide basic material for the studying antiviral gene therapy and the molecular mechanism of viral replication and infection.

[Serum antibody response and Hantavirus RNA sequencing in patients with hemorrhagic fever renal syndrome in Yantai areas]

OBJECTIVE

To understand antibody responses to and RNA sequences of Hantavirus in patients with hemorrhagic fever renal syndrome (HFRS) in Yantai areas and to demonstrate the type of the prevalent viruses caused HFRS.

METHODS

Serum specimens collected at acute and convalescent stages from 90 patients with HFRS and IgM and IgG antibodies against Hantavirus were detected with ELISA, and cross plaque reduction neutralizing tests were performed to detect neutralizing antibody. Viral RNA was extracted from the patients? sera by using Trizol method and nested PCR was utilized to amplify the specific segments of the viral cDNA and the products of the PCR were TA cloned and then the nucleotide sequences were determined.

RESULTS

The IgM antibody was positive in 82.2% (88/107) of the patients while the IgG antibody was positive in 85.7% (66/77) of the patients. Both the serologic and sequence analyses demonstrated that the epidemic of HFRS in Yantai areas was caused by mixed types of Hantavirus. The prevalent strains of Hantavirus had higher homology with the strains isolated in Korea than with those isolated previously in China.

CONCLUSIONS

The serologic and sequencing analyses indicated that the epidemic of HFRS in Yantai areas was caused by mixed types of Hantavirus dominated by type SEO.

[Passage adaptability of candidate strains for hemorrhagic fever with renal syndrome purified vaccine in Vero cells and their immunogenicity]

OBJECTIVE

To adapt the candidate strains of hemorrhagic fever with renal syndrome (HFRS) purified vaccine to Vero cells and to study their antigenicity and immunogenicity.

METHODS

The viral strains H8207 (Hantaan virus, HTN) and Y86013 (Seoul virus, SEO) were continuously propagated in Vero cell by the terminal dilution method and studied the characteristics of virus multiplication, viral titers and the amounts of virus antigen after serial passages. Three batches of crude monovalent inactivated vaccine were developed using the different passages of these 2 viral strains.

RESULTS

The strains H8207 and Y86013 adapted to Vero cells and stably grew on the cells with high titers. Rabbits immunized with the crude vaccines of H8207 and Y86013 showed 100% sero-conversion and the neutralizing antibody titers of the rabbit immune sera reached 1?10 at 4 weeks after 2 times of immunization.

CONCLUSIONS

The results suggest that these 2 candidate strains had adapted to Vero cells, possessed high titers and good immunogenicity and be feasible to prepare the HFRS purified vaccine in Vero cells.

Human recombinant neutralizing antibodies against hantaan virus G2 protein

Old world hantaviruses, causing hemorrhagic fever with renal syndrome (HFRS), still present a public health problem in Asia and Eastern Europe. The majority of cases has been recorded in China. The aim of our study was to generate human recombinant neutralizing antibodies to a hantavirus by phage display technology. To preserve the structural identity of viral protein, the panning procedure was performed on native Hantaan (HTN) (76-118) virus propagated in Vero-E6 cells. In total, five complete human recombinant IgG antibodies were produced in a baculovirus expression system. All of them were able to completely neutralize HTN, and Seoul (SEO) virus in a plaque reduction neutralization test (PRNT). Three of these antibodies could also completely neutralize Dobrava (DOB) virus but not Puumala (PUU) virus. All antibodies bind to Hantaan virus G2 protein localized in the virus envelope. The sequence areas within the HTN (76-118)-G2 protein detected by five selected antibodies were mapped using peptide scans. Two partial epitopes, 916-KVMATIDSF-924 and 954-LVTKDIDFD-963, were recognized, which presumably are of paramount importance for docking of the virus to host cell receptors. A consensus motif 916-KVXATIXSF-924 could be identified by mutational analysis. The neutralizing antibodies to the most widely distributed hantaviruses causing HFRS might be promising candidates for the development of an agent for prevention and treatment of HFRS in patients.

Diagnostic rapid tests for acute hantavirus infections: specific tests for Hantaan, Dobrava and Puumala viruses versus a hantavirus combination test

Hantaviruses infecting humans in Eurasia include Hantaan, Seoul, Puumala and the closely related Dobrava and Saaremaa viruses. These viruses are causative agents of hemorrhagic fever with renal syndrome (HFRS), which is recognized as a severe health care problem in several countries. Diagnostics of hantavirus infections relies on serology, performed principally with enzyme immunoassay (EIA) or immunofluorescence assay (IFA). We developed four 5-min immunochromatographic IgM-antibody tests for diagnostics of acute Puumala, Dobrava and Hantaan virus infections and a similar combination test to detect all Eurasian pathogenic hantavirus infections. We evaluated the assays using 100 fingertip blood samples collected randomly from Finnish volunteers, 28 confirmed hantavirus IgM-negative sera, and 77 sera from patients with acute infections of various hantaviruses. The specificities and sensitivities of the Puumala-, Dobrava- and Hantaan virus -specific tests varied from 96 to 100%, whereas, the combination test showed 96% specificity and 80 to 93% sensitivity. Cross-reactions were observed commonly between the Dobrava and the Hantaan virus tests, but only rarely between the Puumala and the Hantaan virus, or the Puumala and the Dobrava virus, tests. Altogether, the rapid tests showed less cross-reactivity than the respective EIA tests. According to the results, the performance of these tests meets well the requirements for diagnostic use. Nevertheless, the specific one-antigen tests were markedly more sensitive than the combination test. However, if optimized, a combination test would be suitable for regions where several hantaviruses circulate.

Generation of an HFRS patient-derived neutralizing recombinant antibody to Hantaan virus G1 protein and definition of the neutralizing domain

Hantaan virus (HTNV) in the Hantavirus genus, family Bunyaviridae, is the major cause of severe hemorrhagic fever with renal syndrome (HFRS). We prepared a combinatorial phage display library of human Fabs to HTNV from RNA extracted from the blood lymphocytes of a convalescent HFRS patient. We selected two G1 glycoprotein-specific clones and one nucleocapsid protein (N)-specific clone from the Fab library for further studies. The human Fab antibodies were converted to IgG form in baculovirus/insect cells system by using cassette vectors that we developed earlier. Characterization of the recombinant antibodies revealed that the two G1-specific IgGs, could bind to and neutralize HTNV but not Seoul virus (SEOV). The N-specific IgG did not neutralize either HTNV or SEOV. Sequence analysis revealed that the two G1-specific clones differed by only one predicted amino acid in their complementarity determining regions, CDR3. Epitope mapping studies were carried out with one of the two G1-specific clones and synthetic peptides representing portions of HTNV G1. Results indicated that the recombinant antibody recognizes the core amino acid sequence LTKTLVIGQ, which is found near the C-terminus of HTNV G1. These results are the first to define a neutralizing epitope on the G1 protein of HTNV using an antibody derived from an HFRS patient.

Use of vesicular stomatitis virus pseudotypes bearing hantaan or seoul virus envelope proteins in a rapid and safe neutralization test

A vesicular stomatitis virus (VSV) pseudotype bearing hantavirus envelope glycoproteins was produced and used in a neutralization test as a substitute for native hantavirus. The recombinant VSV, in which the enveloped protein gene (G) was replaced by the green fluorescent protein gene and complemented with G protein expressed in trans (VSVDeltaG*G), was kindly provided by M. A. Whitt. 293T cells were transfected with plasmids for the expression of envelope glycoproteins (G1 and G2) of HTNV or SEOV and were then infected with VSVDeltaG*G. Pseudotype VSV with the Hantaan (VSVDeltaG*-HTN) or Seoul (VSVDeltaG*-SEO) envelope glycoproteins were harvested from the culture supernatant. The number of infectious units (IU) of the pseudotype VSVs ranged from 10(5) to 10(6)/ml. The infectivity of VSVDeltaG*-HTN and VSVDeltaG*-SEO was neutralized with monoclonal antibodies, immune rabbit sera, and sera from patients with hemorrhagic fever with renal syndrome, and the neutralizing titers were similar to those obtained with native hantaviruses. These results show that VSVDeltaG*-HTN and -SEO can be used as a rapid, specific, and safe neutralization test for detecting hantavirus-neutralizing antibodies as an effective substitute for the use of native hantaviruses. Furthermore, the IU of VSVDeltaG*-HTN and -SEO did not decrease by more than 10-fold when stored at 4 degrees C for up to 30 days. The stability of the pseudotype viruses allows distribution of the material to remote areas by using conventional cooling boxes for use as a diagnostic reagent.

The in vitro and in vivo protective activity of monoclonal antibodies directed against Hantaan virus: potential application for immunotherapy and passive immunization

Hantaan virus (HTNV), a member of the genus Hantavirus, family Bunyaviridae, is an etiologic agent causing a serious human disease, hemorrhagic fever with renal syndrome (HFRS), with a mortality as high as 15% and is also a potential bioterrorism agent. It is urgently needed to develop anti-HTNV-neutralizing monoclonal antibodies (MAbs) for treatment and prevention of HTNV infection. In the present study, 18 murine MAbs directed against HTNV strain Chen were generated and characterized. Among these MAbs, 13 were directed against viral nucleocapsid protein (NP), four recognized the viral envelope glycoprotein G2 and one reacted with both NP and G2. Only those MAbs that recognize the epitopes on G2 were positive in hemagglutination inhibition (HI) test and had in vitro virus-neutralizing activity and in vivo protective activity against HTNV infection of susceptible mice. Since all the mice were protected by administration of the virus-neutralizing MAbs one day before and two days after HTNV challenge, these neutralizing MAbs are potentially useful for pre- and post-exposure prophylaxis and for immunotherapy of HTNV infection. Phase II clinical trials of these neutralizing MAbs for emergent treatment of patients with HTNV infection in early stages of HRFS are carried out in endemic areas in China.

Hantavirus infection of dendritic cells

Dendritic cells (DCs) play a pivotal role as antigen-presenting cells in the antiviral immune response. Here we show that Hantaan virus (HTNV), which belongs to the Bunyaviridae family (genus Hantavirus) and causes hemorrhagic fever with renal syndrome, productively infects human DCs in vitro. In the course of HTNV infection, DCs did not show any cytopathic effect and viral replication did not induce cell lysis or apoptosis. Furthermore, HTNV did not affect apoptosis-inducing signals that are important for the homeostatic control of mature DCs. In contrast to immunosuppressive viruses, e.g., human cytomegalovirus, HTNV activated immature DCs, resulting in upregulation of major histocompatibility complex (MHC), costimulatory, and adhesion molecules. Intriguingly, strong upregulation of MHC class I molecules and an increased intercellular cell adhesion molecule type 1 expression was also detected on HTNV-infected endothelial cells. In addition, antigen uptake by HTNV-infected DCs was reduced, another characteristic feature of DC maturation. Consistent with these findings, we observed that HTNV-infected DCs stimulated T cells as efficiently as did mature DCs. Finally, infection of DCs with HTNV induced the release of the proinflammatory cytokines tumor necrosis factor alpha and alpha interferon. Taken together, our findings indicate that hantavirus-infected DCs may significantly contribute to hantavirus-associated pathogenesis.

Serological study of hantavirus in man in the Autonomous Community of Madrid, Spain

Data relating to hantavirus infection in Spain are scarce and limited to rural areas. The aim of this work was to study the seroprevalence of hantavirus infection in the Autonomous Community of Madrid (ACM), a region containing both rural and urban populations in different ecological settings. Sera from 3852 individuals (1849 male, 2003 female) were screened by indirect inmunofluorescence, with Vero E6 cells infected with Puumala, Hantaan and Seoul viruses as antigens. Screen-positive results were confirmed by Western blot with recombinant Seoul virus nucleocapsid protein as antigen. Antibodies against hantavirus were detected in 12 sera (0.31%). No statistical differences were found according to sex and age. The highest prevalence was found in the southeastern area, significantly higher than the central and north-western areas. The most frequent serological pattern was reactivity against all three viruses used (33.3% of all positive sera). Therefore, this study confirms the presence of hantavirus infection in the ACM, including for the first time an urban area of Spain, but with the highest prevalence in a rural area. Serological evidence suggests that there is more than one circulating serotype.

Hantaan virus antibody prevalence in rodent populations of several provinces of northeastern Thailand

We conducted a serological survey of 632 rodents from the northeast region of Thailand in order to assess the presence of Hantaan-like viruses that may be a risk to the human population. Rodents were collected from rice fields, houses and domestic gardens in five northeastern provinces and tested for IgG reacting sera to Hantaan antigen using enzyme-linked immunoassays. The overall prevalence of Hantavirus infection in rodents was 2.1% (13/632). Species that tested positive included Bandicota indica (4.3% positive within species), Rattus exulans (2.1%), R. losea (1.6%) and R. rattus (0.9%). Species such as R. exulans and R. losea are candidate hosts of unidentified Hantaan-like viruses in Thailand.

[Analysis of HFRS vaccination against hemorrhagic fever with renal syndrome during 1999-2000 in Laiwu City]

OBJECTIVE

To evaluate the effect the vaccine of hemorrhagic fever with renal syndrome (HFRS).

METHODS

Data of totally, 1095 individuals who were immunized with HFRS vaccine type produced by Shenyang Baiao Biotechnology, Ltd were analyzed. 1999-2000 in Laiwu City.

RESULTS

Most of the individuals belonged to rural population. In most cases the vaccination was done in spring and autumn. Persons between ages 18-40 years dominated the series. The side effects of the vaccination were seen in 1.71% in which local reaction was 1.35%, general reaction 0.30%, abnormal reaction 0.06% and the lowest reaction rate was seen in the group between ages 7-17.

CONCLUSIONS

The vaccine was quite effective. Both antibody positive ratio and GMT level of antibody were high.

[Clinical study on intrauterine hemorrhagic fever with renal syndrome virus infection]

OBJECTIVE

To find out the status of intrauterine infection with hemorrhagic fever with renal syndrome virus (HFRSV).

METHODS

The blood of mothers and the umbilical cords were examined by using anti-HFRSV-IgG at labor of mothers infected with HFRSV. The venous blood of naturally delivered babies were examined for anti-HFRSV-Ig M, HI test was used to type the HFRSV.

RESULTS

Mothers blood showed positive reaction for anti-HFRSV-IgG. Twenty-three of 27 cases of the fetal death were umbilical cords blood positive two out of twelve of umbilical cord blood that the babies were born naturally after their mothers recovered showed positive for anti-HFRSV -IgG but negative for anti-HFRSV-IgM, 14 babies born naturally normally.

CONCLUSIONS

HFRSV can cause intrauterine infection, and lead to fetal death, but no post natal deformity was observed in the babies born naturally.

[Laboratory diagnosis of hemorrhagic fever with renal syndrome in the Ulianovsk region]

Specific laboratory diagnosis is of great importance for the diagnosis of hemorrhagic fever with renal syndrome (HFRS). The results of the investigation confirm the persistence of the specific antibodies in blood sera of the patients with HFRS. The indices of the serologic confirmation of the diagnosis of HFNS are proven to elevate if the optimal intervals of sampling the pair blood sera is observed.

Characterization of HLA-A2.1-restricted epitopes, conserved in both Hantaan and Sin Nombre viruses, in Hantaan virus-infected patients

Nine different CTL epitopes, conserved in both Hantaan virus (HTNV) and Sin Nombre virus (SNV), were selected for study. The binding affinity of each peptide with HLA-A2.1 molecules in vitro was determined and antigen-specific responses from seven donors who had a previous field infection with HTNV were examined. Although the strength or frequency of CTL activity showed different patterns in the seven patients, five of seven patients showed significant activity against at least one or more epitope peptides. In particular, the peptide ILQDMRNTI (HTNV, aa 334-342; SNV, aa 333-341), which elicited CTL activity in five patients, was shown to be specifically HLA-A2.1-restricted in partially cloned CD8+ T cells and also induced activated and effector CD8+ T cell-producing T cytotoxic (Tc) type 1 cytokines, such as IL-2 and IFN-gamma. The results suggest that this epitope would serve as a useful component for the intervention of both HTNV and SNV infection.

[Comparative study on antibody levels of vaccination group and control group after 4 years of immunized with type B inactivated vaccine against hemorrhagic fever with renal syndrome]

OBJECTIVE

To compare the antibody level of vaccine group and control group in a randomized, controlled trial of type B inactivated vaccine against hemorrhagic fever with renal syndrome(HFRS) in Jiande County of Zhejiang Province and to find out if there is enhancement of subclinical infection about type B inactivated vaccine against HFRS.

METHODS

The number of sera collected (July 1994-July 1998) in vaccine group immunized type B inactivated vaccine against HFRS and control group were 305 and 283 persons in Jiande County respectively, and indirect immunofluorescent antibody method(IFAT) was used for testing the titer of HFRS IgG in sera. The cut-off values were determined on IFA titer of the second sera in control group with positive and negative IFA before vaccine was given respectively, and the subclinical infection of positive and negative IFA of the first sera in vaccine group was evaluated.

RESULTS

When taking different cut-off values of subclinical infection, there were no statistical differences in HFRS IFA positive rates between vaccine group and control group of positive IFA in the first sera. In vaccine group and control group of negative IFA before vaccine given, also the IFA positive rates were not statistically different in these groups. There were no statistical differences of IFA GMT and IFA sero-negative rate between vaccine group and control group.

CONCLUSIONS

The investigation showed there was no statistical difference in antibody level between vaccine group and control group, so there could not be enhancement of subclinical infection of vaccine group receiving type B inactivated vaccine against HFRS.

DNA vaccination with the Hantaan virus M gene protects Hamsters against three of four HFRS hantaviruses and elicits a high-titer neutralizing antibody response in Rhesus monkeys

Four hantaviruses-Hantaan virus (HTNV), Seoul virus (SEOV), Dobrava virus (DOBV) and Puumala virus-are known to cause hemorrhagic fever with renal syndrome (HFRS) in Europe and Asia. HTNV causes the most severe form of HFRS (5 to 15% case-fatality rate) and afflicts tens of thousands of people annually. Previously, we demonstrated that DNA vaccination with a plasmid expressing the SEOV M gene elicited neutralizing antibodies and protected hamsters against infection with SEOV and HTNV. Here, we report the construction and evaluation of a DNA vaccine that expresses the HTNV M gene products, G1 and G2. DNA vaccination of hamsters with the HTNV M gene conferred sterile protection against infection with HTNV, SEOV, and DOBV. DNA vaccination of rhesus monkeys with either the SEOV or HTNV M gene elicited high levels of neutralizing antibodies. These are the first immunogenicity data for hantavirus DNA vaccines in nonhuman primates. Because a neutralizing antibody response is considered a surrogate marker for protective immunity in humans, our protection data in hamsters combined with the immunogenicity data in monkeys suggest that hantavirus M gene-based DNA vaccines could protect humans against the most severe forms of HFRS.

[Seroepidemiologic study on hemorrhagic fever with renal syndrome virus in the migration areas of the Three-Gorges Reservoir Chongqing, Region, Yangtze River]

OBJECTIVE

To ascertain both the immune level and latent infection status among the migrants from the Three-Gorge Reservoir, Chongqing Region.

METHODS

Epidemiological survey and seroepidemiologic study were performed on the spots. Sera HFRSV-IgG antibody of migrations was detected with the indirect immunofluorescent assay technique(IIFAT).

RESULTS

Three in 5 migration areas were seral HFRSV-antibody-positive, i.e. Baitao Town of Fuling Section, Wansheng Village of Fengjie County and Dachang Town of Wushan County, which not only will be evacuated, but also be taken for relocation. However the antibody titer was not high, with positive rates of HFRSV-IgG Ab 0.9%, 3.3% and 3.5% respectively. The other two areas attributed to relocation, HFRSV-IgG-antibody were negative.

CONCLUSIONS

This article confirmed that covert infection rate of HFRS in 5 migration areas was not high. The immune level remained low. Hence, it is very necessary to enhance the immunity of the immigrants.

[Study on using colloidal gold immuno-dot assay to detect special antibody of hemorrhagic fever renal syndrome]

OBJECTIVE

To seek for a simple, sensitive and rapid assay to detect specific antibody of patients suffering from hemorrhagic fever renal syndrome (HFRS).

METHODS

Serum anti-HFRS IgM (sIgM) and IgG (sIgG) antibody were detected in 186 patients with HFRS using colloidal gold immuno-dot assay (CGIDA), and compared with those detected with enzyme linked immunosorbant assay (ELISA) and indirect fluorescent antibody test (IFAT). Kuhuang Shenmai injection (KHSM) combined Astragalus decoction (AD) treatment was applied to 101 HFRS patients in a treated group (n = 50), and the effect of therapy was compared with that in a control group (n = 51) treated with ribarvirin and ganlixin injection.

RESULTS

CGIDA showed positive sIgM antibody in 132 cases (70.9%) and positive sIgG antibody in 163 (87.1%) of the 186 HFRS patients. As compared the two groups in crossing stage, the rate of crossing shock stage in the treated group was higher than that in the control (P < 0.05). As for rate of crossing oliguria stage and from febrile stage directly developed into diuretic stage, the difference between the two groups was insignificant (P < 0.05).

CONCLUSION

CGIDA shows the merits of quick, simple and convenient in detecting sIgM and sIgG antibody in HFRS patients. The effect of KHSM combined AD treatment was not significantly different from that of ribarvirin and ganlixin injection.

Primary humoral immune responses to formalin inactivated hemorrhagic fever with renal syndrome vaccine (Hantavax): consideration of active immunization in South Korea

The efficacy of a formalin-inactivated hemorrhagic fever with renal syndrome (HFRS) vaccine and the effectiveness of a related vaccination program have not been previously evaluated. We measured the primary immune responses to Hantavax by plaque reduction neutralizing antibody test (PRNT), hemagglutination inhibition test (HAI), ELISA and high density particle agglutination test (HDPA) in order to confirm a possible biological efficacy through independent substantiation of experimental results and to compare the results with previous studies. Following two doses of primary vaccination, the seroconversion rate of PRNT and HAI antibody was 33.3% (10/30) [95% C.I. 17.3-52.5%] and 26.7% (8/30) [95% C.I. 12.3-45.9%], respectively. The correlation between PRNT and HAI antibody showed a statistical significance (r=0.58, p<0.01). The seroconversion rate of HDPA and ELISA were both 76.7% (23/30) [95% C.I. 57.7-90.1%], which correlated well with each other (r=0.58, p<0.01). In our study, Hantavax elicited low neutralizing antibody responses, at least in the volunteers samples that we tested. The vaccination program, including the vaccine itself, that has been adopted by the national immunization program to protect against HFRS in Korea should be re-evaluated and re-formulated to produce a higher protective immune response rate.

Clinical characterization of Dobrava hantavirus infections in Germany

There is increasing evidence that Dobrava (DOBV) but not Hantaan (HTNV) hantavirus is a hemorrhagic fever with renal syndrome (HFRS) causing agent in Central Europe. However, only single clinical cases of HFRS due to acute DOBV infection have been described so far. We report on three male patients from a non-endemic hantavirus focus in Northern Germany who suffered from mild to moderate HFRS strongly resembling nephropathia epidemica. Serotyping by detection of hantavirus species-specific neutralizing antibodies revealed acute infections by the HTNV-related hantavirus DOBV in all three cases. Since DOBV infections in the Balkans frequently present as severe HFRS, our cases suggest that Central-European DOBV infections have a different, less severe clinical outcome. These differences in DOBV virulence towards humans might be due to the existence of different genetic lineages of DOBV.

Evaluation of a pan-reactive hantavirus enzyme immunoassay and of a hantavirus immunoblot for the diagnosis of nephropathia epidemica

BACKGROUND

Nephropathia epidemica (NE) caused by the hantavirus serotype Puumala (PUUV) is endemic in large parts of Europe. The prognosis of this disease is usually good. However, a rapid serological diagnosis is important to differentiate NE from potentially more severe renal conditions.

OBJECTIVE

To evaluate the diagnostic usefulness of a novel pan-reactive hantavirus enzyme immunoassay (EIA) and of a novel hantavirus immunoblot (IB).

STUDY DESIGN

Three groups of serum samples were tested with both assays: 79 samples from 43 patients with acute NE, 27 samples from healthy adults, and 29 tricky samples from patients with autoantibodies, with acute Epstein-Barr virus (EBV) or cytomegalovirus (CMV) infections, and from pregnant women.

RESULTS

With the EIA, all but two of the early samples of the NE patients and all of the follow-up samples were positive for hantavirus IgG. All control samples were negative. The IgM EIA was positive in 42 of the 43 primary NE samples. Weak IgM EIA reactions were observed for some of the serum samples from patients with acute EBV and CMV infections. Optimal sensitivity and specificity values for the EIA were achieved when both the IgG and the IgM results were considered for the diagnosis of acute NE. All of the early NE samples reacted with the hantavirus nucleocapsid proteins in the IgG IB and all but one of these samples in the IgM IB. Cross reactions between the PUUV and the Hantaan antigens were very common. Several of the control samples did show borderline or positive bands, but these were mostly bands against only one hantavirus antigen in either the IgG or the IgM IB. The presence of at least three hantavirus bands (PUUV or HTNV) in the IgG and IgM assays was highly predictive of acute NE.

CONCLUSION

Both assays were highly sensitive for the diagnosis of acute NE. However, the specificity of the IB IgM was only 76%. The specificity of both the IB and the EIA can be increased by modifications of the result interpretation.

[Report on epidemic hemorrhagic fever (EHF) surveillance in 1999]

OBJECTIVE

To understand the epidemic tread of epidemic hemorrhagic fever (EHF) in 1999 and to develop programs for its control and prevention.

METHODS

Epidemiological, zoo-epidemiologic, serologic and viral diagnostics were used to analyse the information of monthly and annual reports from surveillance spots.

RESULTS

Twelve thousand nine hundred and thirty cases of EHF in all surveillance spots were reported with 135 cases of death in 1999. The morbidity and mortality were 5.37/100,000, and 1.04% respectively, which had a 1.47% decrease and 9.47% increase, comparing to that of 1998. The accordance of serological and clinical diagnosis was 67.25%, with rate of misreporting 1.28%. In animal surveillance, the density of mouse was 7.46% with predominant species Apodemus agrarius. In residential areas, the density of mouse was 6.21%, with predominant species Rattus norvegicus. For Apodemus agrarius in fields and Rattus norvegicus in residential areas, the indexes of HV carrier were 0.032 and 0.031 respectively in 1999. In spring and autumn, the indexes of HV carrier in Rattus norvegicus were apparently higher than that of Apodemus agrarius as the indexes of HV carrier in Rattus norvegicus were 0.028 and 0.036 comparing with 0.026 and 0.020 in Apodemus agrarius.

CONCLUSION

It is suggested that more attention should be paid to the surveillance in low and medium-sized epidemic areas because northern China is dry with short rainy season while the epidemic situation in the serious epidemic areas had been under control to some degree.

[Safety and immunogenicity of inactivated bivalent EHF vaccine in humans]

OBJECTIVE

Safety and immunogenicity of inactivated bivalent EHF vaccine in humans were evaluated in the epidemic area of Zhejiang province, China.

METHODS

Susceptible persons with negative anti-EHF were selected in Jiande county, Zhejiang province to receive 3 doses of inactivated bivalent EHF vaccine at 0, 7, 28 days. A booster injection was given one year after the primary immunization. Antibody responses were measured in human volunteers by IFA and MCPENT. Local and general reactions were recorded within 72 hours after each vaccination by physicians.

RESULTS

Two weeks after the primary vaccination, 99.04% of the subjects developed significant hantavirus antibody titre measured by IFA which had a 37.34% drop one year after the primary vaccination. Seroconversion rate increased to 100% two weeks after the booster dose. Neutralising antibody titres paralleled this trend with 100% of vaccine recipients producing neutralising antibody two weeks after the primary doses. However, it dropped to 80% one year after the primary vaccination. One hundred percent of the vaccine recipients started to respond two weeks after boosting. The geometric mean titre (GMT) of neutralising antibody against 76 - 118 and UR were 18.27 +/- 2.21 and 12.47 +/- 2.16 respectively after the primary injections, but it increased to 37.09 +/- 2.24 and 32.61 +/- 2.05 respectively after the secondary immunization. General and local reaction rates were 0.46% and 1.98%, with no severe side effects observed in the vaccinees.

CONCLUSION

The vaccine was well tolerated and could induce good humoral immune response.

[Preventive effects of three kinds of inactive vaccines against epidemic hemorrhagic fever (EHF) after 5 years of vaccination]

OBJECTIVE

To observe the safety and the preventive effects of three kinds of vaccines as Mongolian gerbils kidney vaccine, mouse brains vaccine and hamster kidney vaccine inoculated 5 years ago.

METHODS

Field study and laboratory tests were carried out by random grouping and IFAT, MCPENT, ELISA, HI tests.

RESULTS

The antibody-dependent enhancement did not appear in all individuals who received vaccines after four or five years. The seroconversion rates of MCPENT were 8.97%, 11.76% and 18.75% while the seroconversion rates of IFAT were 20.73%, 30.22% and 23.40% respectively for Mongolian gerbils kidney vaccine, mouse brains vaccine and hamster kidney vaccine. The protection rates were 100% for all three kinds of inactive vaccines which showed good epidemiological efficacy.

CONCLUSION

The vaccines can protect clinical infection of EHF effectively after four or five years of the initial vaccination.

Genetic diversity, distribution, and serological features of hantavirus infection in five countries in South America

Since 1995 when the first case of hantavirus pulmonary syndrome (HPS) was reported in Patagonia, there have been more than 400 cases of HPS reported in five countries in South America. The first case of HPS was associated with Andes (AND) virus. In this study, we report on the genetic diversity, geographical distribution, and serological features of hantavirus infection in six countries in South America based on 87 HPS cases from Argentina, Bolivia, Chile, Paraguay, and Uruguay. An early immunoglobulin M (IgM), IgA, and IgG humoral response was observed in almost all HPS cases. The IgM response appears to peak 1 or 2 days after the onset of symptoms. Peak IgG antibody titers occur mostly after the first week. Low IgG titers or the absence of IgG was associated with higher mortality rates. The IgA response peaks around day 15 and then rapidly decreases. The results of phylogenetic analysis based on partial M-fragment G1- and G2-encoding sequences showed that HPS cases from the five countries were infected with viruses related to AND or Laguna Negra (LN) virus. Within AND virus-infected persons, at least five major genetic lineages were found; one lineage was detected in Uruguayan and Argentinean cases from both sides of the Rio de la Plata river. Two Paraguayan patients were infected with a virus different from LN virus. According to the results of phylogenetic analyses, this virus probably belongs to a distinct lineage related more closely to the AND virus than to the LN virus, suggesting that there is probably an Oligoryzomys-borne viral variant circulating in Paraguay. These studies may contribute to a better understanding of hantavirus human infection in South America.

[Isolation, identification and certain characteristics of a Hantaan virus proposed as candidate virus for killed vaccine]

OBJECTIVE

Isolation and identification of a Hantaan virus from HFRS patient's serum for killed vaccine development.

METHODS

This virus temporally called FT14 detected by IFAT, RT-PCR. Partial sequence of M segment was determined by Sanger' a dideoxy chain termination method.

RESULTS

The antigenicity and PCR amplification of the newly isolated virus FT14 proved that it belongs to virus of HTN type. Antiserum to the virus can neutralize many strains of Hantaan virus from different areas. The partial sequence of M segment of FT14, as compared with other HTN strains, showed great differences among nucleotide sequences, while the deduced amino acid sequence is comparatively conservative. The titer of the virus reached its peak at 9 days post inoculation in vitro, then the peak titer could last for a long time.

CONCLUSIONS

This virus strain FT14 would be a good candidate virus for killed vaccine development.

Identification of H-2K(b)-restricted T-cell epitopes within the nucleocapsid protein of Hantaan virus and establishment of cytotoxic T-cell clones

Although neutralizing antibodies against Hantaan virus (HTV) can protect hosts from viral infection, T-cell responses to HTV are also important in host defense against HTV. However, much less is known about cytotoxic T lymphocyte (CTL) responses to HTV. To identify CTL epitopes in the HTV nucleocapsid protein (NP), we selected 7 H-2K(b)-motif-fitting peptides. Of these peptides, 3 peptides (NP3, NP4, and NP7) were recognized by CTL responses derived from HTV-immunized mouse splenocytes. NP3 and NP4 peptides were also recognized by HTV-immunized splenocytes after secondary in vitro stimulation with the relevant peptide, but NP7 could not be recognized after in vitro stimulation. These results agree well with peptide immunization studies showing that peptide-specific CTL responses could be induced with NP3 and NP4 but not with NP7 peptide. Furthermore, CTL activity assay using targets, prepared to express the antigen (NP) endogenously, demonstrated that NP3 and NP4 peptides could be presented endogenously. CTL elicited with NP4 peptide retained some cross-reactivity and was difficult to long-term culture. However, NP3-elicited CTL was very specific for NP3 peptide and was stable enough to be cloned. Among many CTL lines elicited with HTV or HTV NP peptides, 6 NP3-specific CTL clones were established and have been maintained more than 2 years. All 6 CTL clones were characterized to be CD3+, CD4-, CD8+, CD25+, CD62L-, and NK1.1-, and to use TCR Vbeta6. This preferential usage of TCR Vbeta6 indicates that TCR Vbeta6 regions are important for recognition of the HTV NP3 epitope (NP221-228, SVIGFLAL) on H-2K(b) molecule. Our data demonstrate the definition of mouse CTL epitopes in HTV and the generation of HTV-specific mouse CTL clones.

[A study on the epidemiology and preventive measure on epidemic haemorrhage fever in army barrack area in Shandong]

OBJECTIVE

In order to guide the army and civilians to carry out the prevention on epidemic haemorrhage fever (EHF), it's necessary to elucidate the epidemic feature of natural epidemic foci and the risk factors of EHF in the army - stationed areas.

METHODS

Samples were tested by pathogenic and serologic means before data was collected and analyzed by case - control or family - control studies.

RESULTS

Cases belong to house - mouse type (91.48%), field - mouse type (7.21%) and unclassified (1.31%) coexist in the stationed area. In the two types of noticed cases, no significant difference in distributions of sex, profession and ages. Most house - mouse type cases occurred in the peak time from March to June and field - mouse type in November to next February. The type of EHF virus antigen of mice and the type of serum were both accordant with their host types. Dwelling in border area, living rooms with mice, dogs raising, injury of mouth tissue, eating food contaminated by mice, and household with mice living around were more frequently seen in cases themselves and in families of the cases than in controls of both groups (P < 0.05). The mice intensity could be under control to 1.0%, if comprehensive measure on mice control can be implemented.

CONCLUSIONS

The stationed area is an epidemic area mixed with both house - mouse and field - mouse types, with majority of house - mouse type. It was house - mouse type virus infection that caused the epidemic area expanded and the number of cases increased radically these years. EHF was epidemic in spring and summer season in the stationed area mainly because the infections were among family members. Food contaminated by mice or close contact with mice played an important role. Mice eradication and prevention were the leading measures to prevent EHF, from our more than ten years of experiences.

Clinical evaluation of a vaccinia-vectored Hantaan virus vaccine

We evaluated a vaccinia-vectored vaccine for hemorrhagic fever with renal syndrome in clinical trials. A Phase I dose-escalation study in 16 volunteers divided into four groups demonstrated that subcutaneous inoculation of approximately 10(7) plaque-forming units of the recombinant virus was safe and immunogenic. Vaccination of a fifth group of 12 volunteers indicated that neutralizing antibody titers to both vaccinia virus and Hantaan virus were enhanced after a second inoculation. Comparing two routes of vaccination showed that scarification effectively induced neutralizing antibodies in vaccinia virus-naive volunteers but that subcutaneous inoculation was superior to scarification in vaccinia virus-immune individuals. A Phase II, double-blinded, placebo-controlled clinical trial was conducted among 142 volunteers. Two subcutaneous vaccinations were administered at 4-week intervals. Neutralizing antibodies to Hantaan virus or to vaccinia virus were detected in 72% or 98% of vaccinia virus-naive volunteers, respectively. In contrast, only 26% of the vaccinia virus-immune volunteers developed neutralizing antibody responses to Hantaan virus. J. Med. Virol. 60:77-85, 2000. Published 2000 Wiley-Liss, Inc.

Seroprevalence study of Hantavirus infection in the community based population

The genus Hantavirus, family Bunyaviridae, comprise at least 20 distinct viruses. Ten of these have been linked to specific human diseases. Hemorrhagic fever with renal syndrome has been recognized since the 1950s. Hantavirus pulmonary syndrome was recognized in the United States in 1993. Epizootiologic studies of Norway rats in the Baltimore area have shown that rodent infections with hantaviruses are common and geographically widespread with prevalence reaching 44% in tested rat populations. These viruses are antigenically related to the Seoul virus. Hantavirus infections in humans occur through transmission from a rodent reservoir, primarily by inhalation of virus laden rodent excreta. There is no evidence to support person-to-person transmission of any known Hantavirus. To establish the prevalence of Hantavirus infections in humans in the Baltimore area we collected sera from 1,212 persons attending a community based health care system. These were tested for antibodies against three reference Hantavirus strains: Hantaan (HTN), Seoul (SEO), and Convict Creek (HN017). HN017 was chosen to represent the SinNombre (SN-like) strains of Hantavirus. Sera from nine patients were positive to Hantavirus specific antibodies, HTN, and SEO by Enzyme Linked Imuno Sorbent Assay (ELISA). No sera were positive for HN017 antigen. All sera that were positive for HTN and SEO were tested by western blot for HTN. All nine sera were confirmed positive by western blot. This suggests that unrecognized infections with Hantaan or Seoul-like viruses occur in the Baltimore area in humans, although the prevalence rate in humans is low (0.74%). Epidemiologic monitoring may be warranted to establish the health implications of these infections.

[A study on immunogenicity and safety of bivalent inactivated vaccine against hemorrhagic fever with renal syndrome]

OBJECTIVE

To study side effects and effectiveness of bivalent inactivated vaccine against hemorrhagic fever with renal syndrome in population of a randomized controlled field trial.

METHODS

Serum indirect immunofluorescent antibody in 167 persons and neutralization antibody (types I and II) in 69 persons, who received three-dose vaccine, were determined two weeks after immunization, and side effects in 657 vaccinees were observed within 72 houses after immunization.

RESULTS

Serum positive conversion rate of indirect immunofluorescent antibody was 99.04% (166/167) with GMT of 24.51 +/- 2.06. Serum positive conversion rate of neutralization antibody was 100% (69/69), 91.30% (63/69) for types I and 88.41% (61/69) for type II, respectively. GMTs for type I and II neutralization antibody were 18.27 +/- 2.21 and 12.47 +/- 2.16, respectively. Side effects at local site vaccinated of the body and temperature rising could be seen in 1.48% and 0.36% of the vaccinees, respectively. No severe side effect and abnormal reaction was found in vaccinees on the field.

CONCLUSION

Immune response to bivalent inactivated vaccine against hemorrhagic fever with renal syndrome was satisfactory with slight side effect.