Presence Of Viral Antigen Research Articles

Evidence of measles virus antigens and RNA in endometrial cancer

Objectives To look for an association between the measles virus and endometrial carcinoma, the most frequent cancer of the female genital tract in our area. Study design Thirty-six of 49 patients with endometrial carcinoma were studied to detect fingerprints of the measles virus. Immunohistochemistry with the avidin–biotin complex method and in situ hybridization were used to demonstrate the association. The clinicopathological correlations were carried out to support a relationship between the virus and the cancer if any was found. Results Twenty-six of the 36 cases (72%) of endometrial cancer showed the presence of measles virus antigens in the tumor cells. Sixteen of 21 cases were positive for measles virus RNA by in situ hybridization. Although type I endometrial carcinoma was more positive for viral particles than type II, type II cancer, when allied with the measles virus, was more often associated with the depth of myometrial invasion and with death from tumor. Conclusions We demonstrate for the first time a link between endometrial cancer and the presence of viral antigens and RNA of the measles virus, although these findings do not necessarily signify a causal relationship between the cancer and the virus.

Detection and localization of a goose adenovirus in experimentally infected goslings, using indirect immunofluorescence with paraffin-embedded tissue sections

To establish an ideal method for the detailed definition of the tropism of the goose adenovirus new-type gosling viral enteritis virus (NGVEV) in conventional paraformaldehyde-fixed paraffin-embedded gosling tissue sections, an indirect immunofluorescence assay was established and optimized in this study for the first time. Three-day-old goslings orally inoculated with the CN strain of NGVEV were killed from 0.5 h to 30 days post-infection (p.i.) at intervals, and organs were collected and prepared for immunofluorescence assay and ultrastructural observation. NGVEV antigens could be detected in the gastrointestinal tract and lymphoid organs as early as 24 h p.i. The lymphoid organs (bursa of Fabricius, thymus, Harderian gland and spleen), the digestive organs (proventriculus, gizzard, duodenum, jejunum, ileum, caecum, rectum and liver), kidney, myocardium and brain of NGVEV-infected goslings showed extensive evidence of presence of viral antigens. Lymphocytes, macrophages, mesenchymes, endothelial cells, epithelia, superficial and crypt mucosal cells, glandular cells, and fibrocytes served as the principal site for NGVEV localization. The number of positive cells and intensity of fluorescence increased until 15 days p.i. Ultrastructural observation showed that NGVEV particles could be seen from 3 days p.i. onwards.

Efficacy of oral ribavirin treatment in Crimean-Congo haemorrhagic fever: A quasi-experimental study from Turkey

The aim of this study was to evaluate the efficacy of oral ribavirin treatment in patients with Crimean-Congo haemorrhagic fever (CCHF). In 2004, all patients diagnosed with CCHF were treated with oral ribavirin, however in 2003 none of the CCHF patients had been given treatment due to lack of confirmatory diagnostic information at that time in Turkey. In this study, patients treated with ribavirin in 2004 (n=126) were compared with ribavirin-untreated CCHF patients (n=92) in 2003. Patients only with a definitive diagnosis of CCHF (clinical symptoms plus the presence of specific IgM antibodies against CCHF virus and presence of viral antigen) were included in this study. There was no difference in the case-fatality rate between treated and untreated patients (7.1% vs. 11.9%; P>0.05). A Cox Proportional Hazards regression analysis revealed that altered sensorium and prolonged international normalized ratio were independent predictors of mortality. Our results showed that oral ribavirin treatment did not improve the survival rate in CCHF patients. Ribavirin and supportive care are the only available choices for treatment of CCHF patients, but to ascertain the efficacy of ribavirin, more laboratory and observational studies are necessary and ultimately, to elucidate these conflicting results and evaluate the efficacy undoubtedly, a multicenter randomised controlled trial will be needed.

Pathologic Findings Associated with Delayed Death in Nonhuman Primates Experimentally Infected with Zaire Ebola Virus

Zaire Ebola virus infection in macaques causes a fatal disease with a pathogenesis similar to that in humans. During several independent therapy studies, we noted altered tissue tropism in 6 rhesus macaques that survived longer than those with a typical disease course. The mean time to death for these 6 macaques was 21.7 days, which is significantly longer than the average mean time to death of 8.3 days for 20 untreated historical control animals. In addition to living significantly longer, these 6 animals exhibited a variety of deteriorating clinical signs with pathologic findings that were not seen in the untreated control animals, as well as the presence of viral antigen in the brain, eye, pancreas, thyroid, and lung. We suggest that treatment extended the time course of the disease and permitted the virus to infect tissues not usually affected in the typical model.

Myotropic Avian Leukosis Virus subgroup J Infection in a Chicken

The study describes a highly productive myotropic avian leukosis virus infection (ALV) in a 3-month-old female chicken. At necropsy, ascites, hepatic fibrosis and cardiomegaly were seen. Histologically, the most striking lesion was the presence of cytoplasmic basophilic inclusions in myocardial fibers. Immunostaining for ALV group specific antigen p27 revealed a diffuse presence of virus antigen in cardiac myofibers, in smooth muscle fibers of most of the organs, and in rare, pancreatic and ovarian theca cells. Ultrastructurally, myocardial inclusions consisted of clusters of 50-60 nm round particles with interspersed ribosome-like granules. Numerous C-type particles were found in intercellular spaces of ALV p27 positive tissues. PCR analyses revealed the presence of both ALV-E and ALV-J related sequences. In chicken genome, ALV-E is usually present as endogenous provirus therefore, the pathological findings observed in this case are considered to be related with the ALV-J infection. The results of this report further confirm that ALV-J may be responsible for highly productive myotropic infections.

The Role of B Cells in the Immune Response to Pestivirus (Classical Swine Fever Virus)

Pigs inoculated with the Alfort 187 isolate of classical swine fever (CSF) virus were used to study the immunological mechanisms associated with the humoral immune response in the disease. Quantitative and qualitative changes in the B-cell population (lambda light chain [C-lambda]-positive, immunoglobulins [Ig]-M-positive, and IgG-positive were demonstrated in the spleen, thymus and ileocaecal lymph node. Blood and serum samples were used to examine changes in leucocytes, albumin/globulin ratios and specific antibodies against CSF virus titration. Despite the lymphoid depletion shown by infected animals, an increase in B cells and potentially immunoglobulin-producing C-lambda+ plasma cells was observed in the lymphoid organs from the onset of disease. The increase in C-lambda+ B cells was matched by a parallel increase in IgM+ cells, which attained peak values from 7 days post-inoculation (dpi), while IgG+ cells increased from 11 dpi onwards. The enhanced biosynthetic capacity of these cells may have been linked to the initiation of a humoral response to CSF virus, and to the progressive decline in the albumin/globulin ratios of inoculated animals. Activation, proliferation and differentiation of B cells coincided with the presence of viral antigen, and with an intense phagocytic and biosynthetic activity of monocytes-macrophages and T lymphocytes. The previously reported increase of cytokine (TNFalpha, IL-1alpha and IL-6) production by monocytes-macrophages, and the release of IL-2, IL-4 and IFNgamma by T lymphocytes, may play a role in the initiation of the humoral immune response in CSF. These changes may have influenced the late appearance of virus-specific antibodies in the study, as well as the progressive increase of immunoglobulins.

Systemic Viral Infections and Collateral Damage in the Liver

The liver is involved in infections by hepatotropic viruses that replicate in the liver and for which the liver is the main target. These include hepatitis A, hepatitis B, hepatitis C, and hepatitis E viruses. In all of these infections, hepatitis and liver damage arise as a consequence of the immune response to virus within the liver.1 In addition, the liver can be affected as part of a generalized host infection with viruses that primarily target other tissues, particularly the upper respiratory tract. Examples of this phenomenon include the herpes viruses (Epstein-Barr virus, cytomegalovirus [CMV], and herpes simplex virus), parvovirus, adenovirus,2 and severe acute respiratory syndrome (SARS)-associated coronavirus.3 Liver involvement in nonhepatotropic viral infections can range from mildly deranged liver biochemistry to fulminant liver failure. In most of these infections, hepatitis is thought to be a consequence of an immune response to viral antigens with a close topographic association between the presence of viral antigens and the associated inflammatory infiltrates in the liver. Loss of immune control may be responsible for the development of hepatitis in CMV hepatitis4 and other opportunistic viral infections such as adenovirus.4 Similar activities may also be involved in SARS-associated hepatitis, which is characterized by focal lobular lymphocytic infiltrates.5 The paper by Polakos et al6 in this issue of The American Journal of Pathology broadens the mechanism by which viruses can cause hepatitis by demonstrating that viral-specific CD8+ T cells, generated in response to a viral infection restricted to sites outside the liver, can trigger T-cell-mediated hepatitis in the absence of viral antigens in the liver. They describe the involvement of the liver during pulmonary infection with influenza virus and demonstrate that hepatitis can occur even in the absence of detectable virus in the liver. The authors describe the hepatitis in influenza infection as “collateral damage” and suggest that it occurs as a consequence of the recruitment to the liver of CD8+ effector T cells that expand systemically in response to the viral infection. These observations are of great importance for understanding the involvement of the liver in systemic infections and elucidate some of the clinical syndromes of liver inflammation that cannot be easily explained by invoking antigen-specific T-cell responses in the liver.

Visualization of Central European Tick-Borne Encephalitis Infection in Fatal Human Cases

Central European tick-borne encephalitis (TBE) is caused by a flavivirus vectored by the Ixodes ricinus tick. In severe infections, TBE presents as (myelo)meningoencephalitis with considerable mortality. Characteristic neuropathologic changes feature a multinodular to patchy polioencephalomyelitis accentuated in spinal cord, brainstem, and cerebellum. Visualization of viral infection by immunohistochemistry has not yet been achieved. We analyzed immunohistochemically the distribution of viral antigens and its correlation with neuropathologic changes, serological data, and disease duration in 28 brains of cases with a clinical diagnosis of TBE and neuropathologically confirmed (meningo)encephalomyelitis. In 20 brains (including 10 seropositives), viral antigens were detectable. These cases were characterized by relatively short clinical duration ranging from 4 to 35 days. Immunoreactivity was most prominent in perikarya and processes of Purkinje cells and large neurons of dentate nucleus, inferior olives, and anterior horns. In addition, immunoreactivity was detected in neurons of other brainstem nuclei, isocortex, and basal ganglia. There was an inverse topographical association of severe inflammatory changes with presence of viral antigens. Some cytotoxic T cells were in direct contact with tick-borne encephalitis virus (TBEV)-infected neurons. We conclude that 1) TBE viral antigens are immunohistochemically detectable in brains of fatal cases with relatively short natural clinical course; 2) TBE virus neurotropism preferentially targets large neurons of anterior horns, medulla oblongata, pons, dentate nucleus, Purkinje cells, and striatum; 3) topographical correlation between inflammatory changes and distribution of viral antigens is poor; and 4) immunologic mechanisms may contribute to nerve cell destruction in human TBE.

68. Development of a Novel Non-Viral DNA Vaccine-Delivering Gene into the Nucleus of Dendritic Cells

DNA vaccine has potential advantages exceeding the conventional vaccine. Recently, dendritic cells (DCs) attract attention as a target of DNA vaccine because DCs have a key role in initiating and controlling immune responses and are the most potent antigen-presenting cells (APCs). Currently, recombinant adenovirus (rAd) is used as the most efficient method for DC transduction. However, it is known that the DC transduction using rAd at a relatively high multiplicity of infection (MOI) interferes DC function and elicit strong immune response by presence of viral antigen. Therefore, the development of efficient non-viral gene vector is required to solve this problem.

Lesions and tissue distribution of viral antigen in severe acute versus subclinical acute infection with BVDV2

Differences in the distribution and spread of viral antigen, development of lesions and correlation between presence of viral antigen and lesions were compared between a low and highly virulent strain of BVDV2. Two groups of two-week- to two-month-old colostrum-deprived calves were inoculated intranasally with the naturally occurring low virulent BVDV2 strain 28508-5 or the highly virulent strain 1373. To study the sequence of virus spread and lesion development, calves were necropsied at days three, six, eight–nine and 12 to 14 post inoculation (pi). Viral antigen was detected by the indirect immunoperoxidase method in cryostat sections and lesions were evaluated in H&E-stained paraffin sections. Clinical signs and changes in lymphocyte and thrombocyte numbers confirmed the difference in virulence between the two strains. Both strains showed comparable initial infection and spread at day three pi. At day six pi, they were found widespread in lymphoid tissues and multifocally in intestinal mucosa. Lesions were very mild despite the large amount of antigen in the lymphoid tissues. After day six pi, differences between the low and highly virulent strains became more prominent. The strain of low virulence was cleared from the tissues, but there was a transient phase of depletion. The highly virulent strain continued to spread to different organs and there was severe depletion of lymphoid tissues without recovery.

Ocorrência de apoptose em leucócitos no esfregaço de sangue periférico e em sincícios na infecção in vivo pelo vírus da cinomose canina

The aim of this paper is to report the occurrence of apoptosis in peripheral blood leukocytes and in syncytia induced by experimental infection of dogs with canine distemper virus. Blood was collected from nine puppies that were inoculated with the Snyder Hill strain of CDV, and stained with May Grunwaldt-Giemsa. Dogs were necropsied and retropharyngeal lymph nodes were collected and processed for paraffin embedding. Five micrometers thick sections were stained with hematoxylin-eosin and methyl green pyronin. Other sections were submitted to TUNEL reaction for in situ detection of apoptosis, and immunohistochemistry to detect CDV antigen. Immunohistochemistry confirmed the presence of viral antigen. Syncytia were present in all retropharyngeal lymph nodes. Several syncytia contained apoptotic nuclei as detected by hematoxylin-eosin and methyl green pyronin stains. Apoptotic nuclei were labeled inside syncytia by the TUNEL reaction. Blood smear analyses indicated higher proportion of apoptotic leukocytes in the peripheral blood of infected dogs.

Interactions of poult enteritis and mortality syndrome-associated reovirus with various cell types in vitro

An avian reovirus, ARV-CU98, has recently been isolated from poults experiencing poult enteritis and mortality syndrome (PEMS). To further understand ARV-CU98 and its role in PEMS, the current study investigates interactions of ARV-CU98 with various cell types in vitro. When macrophages, B cells, T cells, and liver cells of chicken or turkey origin were co-incubated with ARV-CU98, only cells of liver origin demonstrated cytopathic effects, the presence of viral antigen, and reduced metabolic activity over time. Furthermore, distinctive pockets of viral particles were evident in electron microscopic examination of a chicken hepatocellular carcinoma (LMH) cell line, but not in a chicken macrophage cell line (MQ-NCSU) co-incubated with virus. Additional evidence of viral replication in LMH, cells but not MQ-NCSU cells was demonstrated by the presence of two viral bands (43 and 145 kD size) in cell lysates from LMH cells exposed to ARV-CU98. Although not capable of being infected by ARV-CU98, MQ-NCSU cells do appear to be activated by the virus since IL-1 mRNA expression is increased in MQ-NCSU cells 2 h after addition of the virus. LMH cells exposed to the virus demonstrate a decrease in IL-1 mRNA expression by 8 to 10 h after addition of the virus, perhaps corresponding to the initiation of infection by the virus. In conclusion, this study demonstrates that ARV-CU98 actively infects and replicates in LMH cells, but not in lymphocytes or macrophages, suggesting that the liver may be a target and site of replication of ARV-CU98 in poults experiencing PEMS.

Experimental Nipah Virus Infection in Pigs and Cats

A human isolate of Nipah virus from an outbreak of febrile encephalitis in Malaysia that coincided with a field outbreak of disease in pigs was used to infect eight 6-week-old pigs orally or subcutaneously and two cats oronasally. In pigs, the virus induced a respiratory and neurological syndrome consistent with that observed in the Malaysian pigs. Not all the pigs showed clinical signs, but Nipah virus was recovered from the nose and oropharynx of both clinically and sub-clinically infected animals. Natural infection of in-contact pigs, which was readily demonstrated, appeared to be acute and self-limiting. Subclinical infections occurred in both inoculated and in-contact pigs. Respiratory and neurological disease was also produced in the cats, with recovery of virus from urine as well as from the oropharynx. The clinical and pathological syndrome induced by Nipah virus in cats was comparable with that associated with Hendra virus infection in this species, except that in fatal infection with Nipah virus there was extensive inflammation of the respiratory epithelium, associated with the presence of viral antigen. Viral shedding via the nasopharynx, as observed in pigs and cats in the present study, was not a regular feature of earlier reports of experimental Hendra virus infection in cats and horses. The findings indicate the possibility of field transmission of Nipah virus between pigs via respiratory and oropharyngeal secretions.

Expression of Heme Oxygenase-1 Mediated by A Protein Transduction Domain Protects Insulin Producing Cells from Cytokine- Induced Cytotoxicity.

INTRODUCTION. Microsomal Heme Oxygenase-1 (HO-1) has been identified as a ubiquitous stress protein induced in many cell types by various stimulants such as hemolysis, inflammatory agents, oxidative stress, heat shock, and growth factors[1]. HO-1 is the enzyme that controls the degradation pathway of heme by catalyzing its oxidation into biliverdin, carbon monoxide, and iron. Although the role of HO-1 induction in oxidative stress is not completely understood, it has been shown that induction of HO-1 expression results in protection from cytokine-induced apoptosis and oxidative stress in in vitro cell culture and in various animal models, including pancreatic islet transplantation[2]. Thus, expression of HO-1 through gene therapy protocols might prove useful to reduce the deleterious effects of oxidative stress in islet isolation as well as to prevent damage in the peri-transplant period. However, viral vectors or other transfection methods available for transduction of genes into islets have limited efficacy and the presence of viral antigens (especially adenovirus) may potentially induce immunological responses against the transfected islets. Moreover, the long-term effects of genetic manipulations of islets, in particular those affecting apoptosis, may have undesirable long-term effects such as impaired mitochondrial signals regulating insulin secretion. Proteins can be directly transferred to cells when they are linked to protein transduction domains (PTDs), small peptide domains that can freely cross cell membranes[3]. In particular, proteins fused to an 11-amino acid protein transduction domain (PTD) from the human immunodeficiency virus transactivator of transcription (TAT) protein, readily transduce many cell types including pancreatic islets[4]. In this study we have characterized a functional HO-1 protein fused to a PTD METHODS. Cloning and Related Techniques. The recombinant TAT antiapoptotic fusion proteins were generated by subcloning the coding region of the murine HO-1 gene in frame with the TAT leader peptide (amino acids 47-58 YGRKKRRQRRR) in a bacterial expression generously provided by Steven Dowdy from Washington University School of Medicine, St Louis. A 6xHis-affinity tag allowed the purification of the fusion protein through affinity chromatography.

Germinal centre localization of bovine viral diarrhoea virus in persistently infected animals.

Immunohistochemical analysis of peripheral lymph nodes from gnotobiotic calves persistently infected with bovine viral diarrhoea virus (BVDV) revealed extensive deposition of E(rns) and localization of the viral genome in the light zone of germinal centres. Viral antigen co-localized with immunoglobulin in the germinal centres and was shown to be extracellular. Despite the presence of viral antigen in germinal centres, circulating anti-BVDV antibody was not detected. These findings provide evidence that calves persistently infected with BVDV, in the absence of adventitious infection, can generate a B cell response to the persisting virus. The nature of the tolerance in calves persistently infected with BVDV is discussed in light of these findings.

Characterization of Lesions Caused by a South American Virulent Isolate ('Quillota') of the Hog Cholera Virus

In this study, macroscopic and histopathological lesions produced by a virulent South American isolate ('Quillota') of hog cholera virus were studied. The virus was inoculated in doses of 10(5)TCID50 in each of 35 pigs of 20 kg live weight. The animals were slaughtered from 4 to 18 days post-inoculation. The presence of virus antigens in lymphatic tissue was confirmed by both direct immunofluorescence and Avidin-Biotin-Peroxidase techniques in formalin-embedded tissue samples. Histological sections were stained with haematoxylin-eosin and Mallory's phosphotungstic acid haematoxylin methods. The 'Quillota' isolate used in this study caused a disease characterized by vascular lesions (splenic infarcts, haemorrhages in the lymph nodes and the urinary system and disseminated microthrombosis), and necrosis of lymphocytes, particularly in the B-areas of the lymphoid organs, lesions that are characteristic of the acute form of the disease. Other lesions observed were a non-purulent meningoencephalitis, the necrosis of the epithelial cells of tonsils, the presence of fibrin nets in the red pulp and a marked thickening of the alveolar septa.

Immunoglobulin A responses to Puumala hantavirus.

Puumala hantavirus (PUUV) causes nephropathia epidemica (NE), a form of haemorrhagic fever with renal syndrome that occurs in northern and central Europe. The immunoglobulin A (IgA) response in NE patients was studied. The levels of total serum IgA in acute-phase samples from NE patients were found to be significantly elevated when compared with the levels in healthy controls. ELISAs for detection of the IgA1 and IgA2 responses against each PUUV structural protein (N, G1 and G2) were developed and evaluated. Sequential sera from NE patients (acute, convalescent, 2-year) and 10-20 year NE-convalescent sera were examined. Most patients developed detectable levels of IgA1 against N and G2, while the G1 responses were low or undetectable. Seven of nine 10-20 year sera contained virus-specific IgA1, which may indicate the prolonged presence of viral antigens after the initial infection. PEPSCAN analysis revealed several IgA-reactive antigenic regions in the N protein. Serum IgA and IgG was purified by affinity chromatography and examined by a virus-neutralization assay. Three of five sera from acute-phase NE patients contained neutralizing IgA1. The diagnostic potential of the PUUV-specific IgA1 response was evaluated. The N and G2 assays showed specificities of 100% with sensitivities of 91 and 84%, respectively, compared with an IgM mu-capture ELISA. Several NE patients, clinically diagnosed for acute PUUV infection, with borderline or undetectable levels of PUUV-specific IgM, were found to be highly positive for the presence of PUUV N-specific serum IgA1, proving the diagnostic value of IgA analysis as a complement to detection of IgM.

Effect of parainfluenza-3 virus challenge on cell-mediated immune function in parainfluenza-3 vaccinated and non-vaccinated calves

A group of four conventional, colostrum-fed calves was vaccinated with live parainfluenza type 3 (PI-3) virus vaccine at 1 and 5 weeks of age. A group of four control calves was treated with cell culture medium at the same time. Two weeks after the second vaccination, both groups of calves were challenged with PI-3 virus by a combined respiratory route. Blood and nasal mucus samples were collected at intervals, and alveolar macrophages were recovered before and after challenge by bronchoalveolar lavage. The results demonstrated that clearance of virus, as indicated by presence of virus antigen was more rapid in previously vaccinated calves. Several alveolar macrophage functions were markedly reduced in all calves 5 to 7 days following virus challenge, although microbicidal activity was unaffected, compared to the controls. The production of neutrophil chemotactic factors by alveolar macrophages occurred more rapidly after virus challenge in the previously vaccinated calves and this correlated with a more rapid neutrophil influx into the lungs in these animals.

Effect of desferrioxamine (DFO) and calcium trinatrium diethylenetriaminepentaacetic acid (DTPA) on rat cytomegalovirus replication in vitro and in vivo

Cytomegalovirus (CMV) infection is a major problem in the immunosuppressed patient. It is thought that besides direct CMV induced cell lysis, immunological damage is part of CMV pathogenesis. New antiviral drugs, which combine immunomodulating and antiviral qualities, could be beneficial. Recently, it has been described that desferrioxamine (DFO) and calcium trinatrium diethylenetriaminepentaacetic acid (DTPA) exhibit both properties. In this report the antiviral effects of both compounds against rat CMV (RCMV) are described in vitro and in vivo using a generalised and local infection model. In vitro , both compounds exhibited a significant antiviral effect, DTPA being more potent than DFO. However, in the generalised infection model no effect was seen on mortality, morbidity or presence of virus in internal organs. In rats infected subcutaneously in the hind paw, no effect was seen locally on paw thickness, presence of viral antigens and inflammatory response. In addition, these rats suffered from a generalised infection of low magnitude at 15 days post infection, although both DFO and DTPA were able to lower the level of viral replication. In conclusion, our data indicate that despite in vitro activity, in vivo usage of DFO or DTPA for acute CMV infection is not warranted.

Effectiveness of a vaccine against red sea bream iridoviral disease in a field trial test.

Since 1990, red sea bream iridovirus (RSIV) has caused high mortalities in the summertime in cultured red sea bream Pagrus major in southwest Japan. To establish control measures for red sea bream iridoviral disease (RSIVD), the effectiveness of a formalin-killed viral vaccine was evaluated in a field trial. Two groups each consisting of 1000 juvenile red sea bream were either intraperitoneally inoculated with vaccine (vaccinated group) or were not vaccinated (non-vaccinated group). After vaccination, the fish were held for 1 wk, then transferred to a marine net pen and observed for 12 wk. The cumulative mortalities caused by RSIVD in the vaccinated group or control group were 19.2 and 68.5%, respectively. Additionally, the presence of virus antigen in the spleen was investigated and body weight was measured 6 and 12 wk post vaccination. In the vaccinated group, viral antigen was not detected. The increase in body weight of vaccinated fish was significantly (p < 0.05) greater than that of control fish. These results suggest that the vaccine against RSIVD was effective in 1 field trial.