Table of Contents:

• Taxonomy Information
• Lifecycle Information
• Genome Information
• Biosafety Information
• Culturing Information
• Epidemiology Information
• Diagnostic Tests Information
• Infected Hosts Information
• Phinet: Pathogen-Host Interaction Network
• Lab Animal Pathobiology & Management
• References
• Data Provenance and Curators

1. Species:
   1. Junin virus (Website 2):
      1. Common Name: Junin virus
      2. GenBank Taxonomy No.: 11619
      3. Description: Argentine hemorrhagic fever (AHF), first described in 1955, is characterized by vascular, renal, hematological, neurological, and immunological alterations, with a case fatality rate of 15-30% in untreated individuals. The etiological agent of AHF is Junin virus (JUN), which was initially isolated in 1958 and confirmed in 1959. Subsequently, JUN was serologically assigned to the Tacaribe group of viruses, which belongs for the family Arenaviridae, genus Arenavirus. Arenaviruses are rodent-borne, enveloped, single-stranded, ambisense RNA viruses with a segmented genome(Garcia et al., 2000).

1. Junin Virus Information
   1. Stage Information:
      1. Virion:
         • Size: Morphologically, arenavirus virions consist of enveloped particles that vary in diameter from approximately 60 to more than 300 nm, with a mean particle size of 92 nm as determined by electron microscopy.
         • Shape: The virions are approximately spherical, enveloped particles that range in diameter from 50 to 300 nm.. The surface of the virion is smooth with T-shaped spikes, composed of viral glycoproteins, extending 7-10 nm from the envelope.

1. Genome of Junin virus
   1. Description: The arenavirus genome consists of two single-stranded RNA molecules, designated L and S, that contain essentially nonoverlapping sequence information. There are minor differences in the lengths of the genomic RNA segments for the individual viruses (L approximately 7,200 bases and S approximately 3,400 bases), but the general organization of the viral genomes, based on current sequence information, is well preserved across the virus family(Southern, 1996). The genomic RNA consists of two segments, S (3.4 k) and L (7.2 kb), both of which are arranged in an ambisense orientation. The S segment encodes the nucleocapsid protein (NP) in negative, antimessage sense at the 3'-end and the viral glycoprotein precursor, GP-C in message sense at the 5'-end. The L RNA segment contains the L protein (polymerase) gene at the 3'-end in negative polarity and the zinc-binding (Z) protein at the 5'-end in message polarity. Posttranslational modification of the cell-associated GP-C precursor yields the structural glycoproteins GP-1 (44 kd) and GP-2 (35 kd), which are assembled into a tetrameric virion spike. GP-1 contains determinants that interact with viral receptors and is recognized by neutralizing antibody. GP-2 contains sites that promote acid-dependent membrane fusion necessary for viral entry. The nucleocapsid protein is an internal RNA-binding protein that complexes with genomic RNA(Peters et al., 1996).
   2. S Segment
      1. Size: S RNA molecule of Junin virus. The complete sequence is 3400 bp(Ghiringhelli et al., 1991).
      2. Gene Count: 2 genes in the S segment(Garcia et al., 2000).
      3. Description: The arenavirus genome is composed of two RNA species. The large (L) segment (about 7200 nucleotides in length) encodes the virus polymerase (L protein) and a small zinc binding protein. The small RNA segment (S) (ca. 3400 nucleotides in length) encodes the nucleocapsid (NP) protein and the glycoprotein precursor, GPC, of two viral glycoproteins, GP1 and GP2(Garcia et al., 2000).
   3. L Segment
      1. Size: L RNA molecule of Junin virus is about 7200 nucleotides in length(Garcia et al., 2000).
      2. Gene Count: 2 genes in the L segment(Garcia et al., 2000).
      3. Description: The arenavirus genome is composed of two RNA species. The large (L) segment (about 7200 nucleotides in length) encodes the virus polymerase (L protein) and a small zinc binding protein. The small RNA segment (S) (ca. 3400 nucleotides in length) encodes the nucleocapsid (NP) protein and the glycoprotein precursor, k GPC, of two viral glycoproteins, GP1 and GP2(Garcia et al., 2000).

1. Biosafety information for Junin virus
   1. Level: Like Lassa virus, Junin, Machupo, Guanarito, and Sabia viruses are infectious by aerosol and the human and rodent specimens should be processed with appropriate precautions in BSL 4 laboratories(Buchmeier et al., 2001).
   2. Precautions: Strict isolation and containment measures are not justified, because AHF is not usually contagious, although a few well-documented instances of interhuman transmission have been found. They can be prevented by avoiding intimate contacts with patients and by properly handling, decontaminating, and disposing of blood and secretions(Webb and Maiztegui, 1988). Because of the hazards inherent in working with Class IV viruses, specific diagnosis should ideally be made in laboratories with special containment facilities(Shepherd, 1988).

1. Vero Cell Culturing :
   1. Description: The best method to isolate Marburg, Ebola, and pathogenic arenaviruses is inoculation of Vero cells, then immunofluorescence or other immunologically-specific testing of inoculated cells for specific viruses at intervals(Jahrling, 1989). Historically, Machupo and Junin viruses were isolated by ic inoculation of newborn hamsters and mice, respectively, but Vero cells are as sensitive and much easier than animals to manage in a P-4 containment. Furthermore, Vero cells permit isolation and identification in 1-5 days, a big advantage over animals, which require 7-20 days of incubation for illness to develop(Jahrling, 1989). Co-cultivation of peripheral leukocytes, isolated by hypaque-ficol separation, with susceptible cells (usually Vero) has increased the isolation frequency of Junin virus(Jahrling, 1989). Detection of viremia was attempted by three different methods in 30 cases of Argentine hemorrhagic fever (AHF). Cocultivation of peripheral blood mononuclear cells (PBMC) with Vero cell monolayers was the most sensitive, detecting Junin virus (JV) in 96% of the cases. Inoculation of whole blood into suckling mice and on Vero cells rendered 53 and 46% of positive isolations, respectively. The results presented suggest that PBMC are infected with JV during the acute period of AHF. JV was isolated with decreasing frequency up to 3 days after treatment with immune plasma, but no virus was recovered from PBMC during early convalescence(Ambrosio et al., 1986).
   2. Medium: Vero E6 (monkey kidney fibroblast) and BHK (baby hamster kidney fibroblasts) were grown in Eagle's minimum essential medium (MEM) containing 5% fetal bovine serum and penicillin G 100 U/ml, streptomycin 100 ug/ml and amphotericin B 0.25 ug/ml. Maintenance medium consisted of MEM supplemented with 1.5% fetal bovine serum and antibiotics(Ellenberg et al., 2002).
   3. Note: Isolation in cell culture monolayers (Vero, BHK), in combination with immunohistochemical procedures, such as immunofluorescence (IF) or peroxidase-antiperoxidase (PAP), gives positive results in 1 to 3 days(Webb and Maiztegui, 1988). Virus can be isolated from the blood of viremic patients from 2 to 12 days after onset and most often between 3 and 8. In fatal cases, virus can be isolated from postmortem spleen, kidney, and clotted blood(Shepherd, 1988).

1. Outbreak Locations:
   1. Since the emergence of Argentine hemorrhagic fever (AHF), a progressive geographic expansion of epidemic outbreaks has been observed. In 1958, human cases were limited to an area of 16,000 km(2) in the north of Buenos Aires province. Currently, the endemo-epidemic area covers approximately 150,000 km(2), reaching north of Buenos Aires, south of Santa Fe, southeast of Cordoba, and northeast of La Pampa provinces. At present, the human population at risk is estimated to be around 5 million(Garcia et al., 2000).
2. Transmission Information:
   1. From: Calomys(Salazar-Bravo et al., 2002). , To: Human(Salazar-Bravo et al., 2002). , With Destination:Human(Website 10). (Salazar-Bravo et al., 2002)
      Mechanism: Human infection with arenaviruses is incidental to the natural cycle of the viruses and occurs when an individual comes into contact with the excretions or materials contaminated with the excretions of an infected rodent, such as ingestion of contaminated food, or by direct contact of abraded or broken skin with rodent excrement. Infection can also occur by inhalation of tiny particles soiled with rodent urine or saliva (aerosol transmission). The types of incidental contact depend on the habits of both humans and rodents. For example, where the infected rodent species prefers a field habitat, human infection is associated with agricultural work. In areas where the habitat of rodent species includes human homes or other buildings, infection occurs in domestic settings(Website 10).
   2. From: Akodon azarae(Salazar-Bravo et al., 2002). , To: Human(Salazar-Bravo et al., 2002). , With Destination:Human(Website 10). (Salazar-Bravo et al., 2002)
      Mechanism: Human infection with arenaviruses is incidental to the natural cycle of the viruses and occurs when an individual comes into contact with the excretions or materials contaminated with the excretions of an infected rodent, such as ingestion of contaminated food, or by direct contact of abraded or broken skin with rodent excrement. Infection can also occur by inhalation of tiny particles soiled with rodent urine or saliva (aerosol transmission). The types of incidental contact depend on the habits of both humans and rodents. For example, where the infected rodent species prefers a field habitat, human infection is associated with agricultural work. In areas where the habitat of rodent species includes human homes or other buildings, infection occurs in domestic settings(Website 10).
   3. From: Mus musculus(Salazar-Bravo et al., 2002). , To: Human(Salazar-Bravo et al., 2002). , With Destination:Human(Website 10). (Salazar-Bravo et al., 2002)
      Mechanism: Human infection with arenaviruses is incidental to the natural cycle of the viruses and occurs when an individual comes into contact with the excretions or materials contaminated with the excretions of an infected rodent, such as ingestion of contaminated food, or by direct contact of abraded or broken skin with rodent excrement. Infection can also occur by inhalation of tiny particles soiled with rodent urine or saliva (aerosol transmission). The types of incidental contact depend on the habits of both humans and rodents. For example, where the infected rodent species prefers a field habitat, human infection is associated with agricultural work. In areas where the habitat of the rodent species includes human homes or other buildings, infection occurs in domestic settings(Website 10).
3. Environmental Reservoir:
   1. Rodent(Salazar-Bravo et al., 2002, Vitullo et al., 1987):
      1. Description: Junin virus, the etiological agent of Argentine hemorrhagic fever (AHF), has most commonly been isolated from the organs and body fluids of three species of rodents, Calomys musculinus, C. laucha, and Akodon azarae. In addition, the virus has been isolated from other rodent species such as Mus musculus and Oligoryzomys flavescens. The vesper mouse, Calomys musculinus, is considered the primary reservoir because it was the most commonly trapped rodent in the endemic area, and because persistent viremia and virus shedding via saliva was found both in naturally and laboratory-infected animals(Salazar-Bravo et al., 2002).
      2. Survival: The effect of infection with Junin virus on growth and reproduction of its natural reservoir, Calomys musculinus, was studied. Eighty-five C. musculinus were inoculated intranasally at birth with 100 TCID50 of Cba An 9446 strain of Junin virus and observed for 480 days. No clinical signs of neurologic illness were registered. Infected animals showed an increased mortality rate of up to 70% between days 24-40 post-infection. This period of high mortality was preceded by low weight gain during lactation and registered until 60 days. From day 14 post-infection until day 480, Junin virus was recovered from blood, urine, and oral swab in all animals checked at any time. By day 480 post-infection, 100% of survivors showed widespread viral dissemination in brain, spleen, kidneys, and salivary glands. There was marked reduction in reproductive efficiency among infected animals. Out of 15 mating pairs, 2 (13.3%) littered at least once compared to 60% in the control group. The reduction of fertility and the altered survival rate of Junin virus-infected C. musculinus indicate that vertical transmission mechanisms per se are insufficient to maintain the infection in successive generations in the absence of horizontal transmission(Vitullo et al., 1987).
4. Intentional Releases:
   1. Intentional Release Information:
      1. Emergency Contact: If clinicians feel that VHF is a likely diagnosis, they should take two immediate steps: 1) isolate the patient, and 2) notify local and state health departments and CDC(MMWR, 1988). Report incidents to state health departments and the CDC (telephone {404} 639-1511; from 4:30 p.m. to 8 a.m., telephone {404} 639-2888). Information on investigating and managing patients with suspected viral hemorrhagic fever, collecting and shipping diagnostic specimens, and instituting control measures is available on request from the following persons at Centers for Disease Control (CDC) in Atlanta, Georgia; for all telephone numbers, dial 404-639 + extension: Epidemic Intelligence Service (EIS) Officer, Special Pathogens Branch, Division of Viral Diseases, Center for Infectious Diseases (ext. 1344); Chief, Special Pathogens Branch, Division of Viral Diseases, Center for Infectious Diseases: Joseph B. McCormick, M.D. (ext. 3308); Senior Medical Officer, Special Pathogens Branch, Division of Viral Diseases, Center for Infectious Diseases: Susan P. Fisher-Hoch, M.D. (ext. 3308); Director, Division of Viral Diseases, Center for Infectious Diseases (ext. 3574). After regular office hours and on weekends, the persons named above may be contacted through the CDC duty officer (ext. 2888)(MMWR, 1988).
      2. Delivery Mechanism: The VHF agents are all highly infectious via the aerosol route, and most are quite stable as respirable aerosols. This means that they satisfy at least one criterion for being weaponized, and some clearly have the potential to be biological warfare threats. Most of these agents replicate in cell culture to concentrations sufficiently high to produce a small terrorist weapon, one suitable for introducing lethal doses of virus into the air intake of an airplane or office building. Some replicate to even higher concentrations, with obvious potential ramifications. Since the VHF agents cause serious diseases with high morbidity and mortality, their existence as endemic disease threats and as potential biological warfare weapons suggests a formidable potential impact on unit readiness. Further, returning troops may well be carrying exotic viral diseases to which the civilian population is not immune, a major public health concern(Website 8).
      3. Containment: Patients with VHF syndrome generally have significant quantities of virus in their blood, and perhaps in other secretions as well (with the exceptions of dengue and classic hantaviral disease). Well-documented secondary infections among contacts and medical personnel not parenterally exposed have occurred. Thus, caution should be exercised in evaluating and treating patients with suspected VHF syndrome. Over-reaction on the part of medical personnel is inappropriate and detrimental to both patient and staff, but it is prudent to provide isolation measures as rigorous as feasible. At a minimum, these should include the following: stringent barrier nursing; mask, gown, glove, and needle precautions; hazard-labeling of specimens submitted to the clinical laboratory; restricted access to the patient; and autoclaving or liberal disinfection of contaminated materials, using hypochlorite or phenolic disinfectants. For more intensive care, however, increased precautions are advisable. Members of the patient care team should be limited to a small number of selected, trained individuals, and special care should be directed toward eliminating all parenteral exposures. Use of endoscopy, respirators, arterial catheters, routine blood sampling, and extensive laboratory analysis increase opportunities for aerosol dissemination of infectious blood and body fluids. For medical personnel, the wearing of flexible plastic hoods equipped with battery-powered blowers provides excellent protection of the mucous membranes and airways(Website 8).

1. Organism Detection Test:
   1. Electron Microscopy :
      1. Description: When the identity of a VHF agent is totally unknown, isolation in cell culture and direct visualization by electron microscopy, followed by immunological identification by immunohistochemical techniques is often successful(Website 8).
   2. IFA test :
      1. Description: The IFA test is the preferred method for serological diagnosis of Argentinean hemorrhagic fever (AHF). Antibodies are detected earlier by IFA than by CF and, in addition, the number of seroconversion detected is greater by the former test. Even so, seroconversion occurs relatively late, and it may be necessary to test specimens up to 30 or 60 days after onset to obtain serological diagnosis(Shepherd, 1988).
   3. Intracerebral inoculation :
      1. Description: Isolation is made by intracerebral inoculation of 1- to 3-day-old mice or by intracerebral or intraperitoneal inoculation of guinea pigs. Mice appear sick 8 to 10 days after inoculation(Shepherd, 1988).
2. Immunoassay Test:
   1. Complement fixation :
      1. Description: The complement fixation (CF) test is rarely used now, although historically it was the method of choice for detection and presumptive identification of the arenaviruses. The CF test was supplanted by immunofluorescence procedures which became generally accepted.
   2. Complement-Enhanced, Plaque-Reduction Neutralization Test :
      1. Description: A refined, complement-enhanced, plaque-reduction neutralization test was developed for measuring neutralizing antibodies against Junin (Argentine hemorrhagic fever) virus. The assay measured neutralizing antibodies after natural as well as vaccine-induced Junin virus infections. Among vaccinated individuals, titers were 2-4-fold higher than those obtained with conventional assays, without loss of specificity. Enhanced sensitivity was achieved by using a standardized complement source (vs human or animal serum) for virus dilution, incubation of virus-serum mixtures at 36 degrees C for 2 h (vs overnight at 4 degrees C) prior to plaque assay, control of age and density of cell monolayers, and variation in overlay conditions(Barrera Oro et al., 1990).
   3. Antigen capture ELISA :
      1. Description: Antigen capture ELISA allowed detection of viral antigen in blood, serum, or tissue homogenates. These tests could be used in acute diagnosis of patients suspected of Junin, Machupo. Sabia, and Guanarito and are often the first available diagnostic result in rapidly fatal cases when patients died before antibody appearance(Peters et al., 1996).
   4. ELISA :
      1. Description: The ELISA test is the most useful and practical for rapid detection of IgM or IgG antibodies in a clinical setting and in seroepidemiologic surveys. The antibodies detected by ELISA persist more than 30 years in some cases(Peters et al., 1996). To elaborate a set of serological tests for the diagnosis of Argentine haemorrhagic fever (AHF), an enzyme-linked immunosorbent assay (ELISA) for detection of specific anti-Junin virus (JV) IgG is described, and its performance is compared with that of the plaque reduction neutralization test (PRNT). The reproducibility, sensitivity, specificity, and confidence limits for positive and negative results for ELISA were statistically analyzed. The value of 800 was demonstrated as the lowest positive titer. Titers greater than or equal to 800 varied within one (two-fold) dilution in 95.6% of the tests, while the sensitivity and specificity were 99.2% and 98.8%, respectively. The assay yielded 1% of false positives and 0.05% of false negatives. A comparison of ELISA to PRNT in detecting the seroconversion for JV was studied by the chi square test (comparison of proportions in paired samples) and the K parameter for agreement proportion. Comparison of ELISA to PRNT showed no significant difference in the proportions of positive and negative results of these assays (P less than 0.01), demonstrating an equivalent performance (K = 0.98) in the diagnosis of AHF. In addition, the simplicity and safety of the procedures involved make this ELISA the most suitable test to detect natural human JV infections(Riera et al., 1997).
      2. False Positive: The assay yielded 1% of false positives(Riera et al., 1997).
      3. False Negative: The assay yielded 0.05% of false negatives(Riera et al., 1997).
   5. Plaque Reduction Neutralization :
      1. Description: Neutralization tests (Nt) for these viruses vary in efficacy; depending on the virus. Neurtralization tests range from very sensitive and reliable (e.g. Junin and Machupo), through moderately insensitive but reliable (Lassa and LCM), to totally unreliable (Marburg and Ebola). The common denominator in all Nt tests is measurement of inhibition of viral replication by reaction with immune serum(Jahrling, 1989). For New World arenaviruses (Junin and Machupo), the usual test is a plaque reduction Nt using Vero cells and the serum dilution-constant virus format. The serum dilution calculated by (probit analysis) to reduce the control number of plaques by 50% (PRN-50) is usually taken as the endpoint, although some laboratories use 80% reduction (PRN-80). The PRN-80 is used to distinguish Junin virus from Machupo virus(Jahrling, 1989).
   6. Indirect Immunofluorescence Antibody (IIF) Test :
      1. Description: The IIF test is clearly the method of choice in most laboratories for detecting recent infections with Marburg, Ebola, and the arenaviruses. Antibodies measured by the IFA test are usually the first to appear, often becoming detectable within the first few days of hospitalization for Lassa virus, within 10 days of onset for Marburg and Ebola viruses, and somewhat later for Junin and Machupo viruses. Presence of specific IgM antibodies or a rising IFA titer is a presumptive diagnosis of acute infection. IgM antibodies measure by IIF decline to undetectable titers within several months, while IgG antibodies persist at least several years(Jahrling, 1989).
3. Nucleic Acid Detection Test: