Detection of viral antigens in formalin-fixed specimens by enzyme treatment

Ebola virus - epidemiology, diagnosis, and control: threat to humans, lessons learnt, and preparedness plans - an update on its 40 year's journey

Ebola virus (EBOV) is an extremely contagious pathogen and causes lethal hemorrhagic fever disease in man and animals. The recently occurred Ebola virus disease (EVD) outbreaks in the West African countries have categorized it as an international health concern. For the virus maintenance and transmission, the non-human primates and reservoir hosts like fruit bats have played a vital role. For curbing the disease timely, we need effective therapeutics/prophylactics, however, in the absence of any approved vaccine, timely diagnosis and monitoring of EBOV remains of utmost importance. The technologically advanced vaccines like a viral-vectored vaccine, DNA vaccine and virus-like particles are underway for testing against EBOV. In the absence of any effective control measure, the adaptation of high standards of biosecurity measures, strict sanitary and hygienic practices, strengthening of surveillance and monitoring systems, imposing appropriate quarantine checks and vigilance on trade, transport, and movement of visitors from EVD endemic countries remains the answer of choice for tackling the EBOV spread. Herein, we converse with the current scenario of EBOV giving due emphasis on animal and veterinary perspectives along with advances in diagnosis and control strategies to be adopted, lessons learned from the recent outbreaks and the global preparedness plans. To retrieve the evolutionary information, we have analyzed a total of 56 genome sequences of various EBOV species submitted between 1976 and 2016 in public databases.

Inactivation of infectious virus and serological detection of virus antigen in Rift Valley fever virus-exposed mosquitoes fixed with paraformaldehyde

Formaldehyde is routinely used to fix tissues in preparation for pathology studies, however concerns remain that treatment of tissues with cellular fixatives may not entirely inactivate infectious virus particles. This concern is of particular regulatory importance for research involving viruses that are classified as select agents such as Rift Valley fever virus (RVFV). Therefore, the specific aims of this study were to (1) assay RVFV-exposed Aedes aegypti mosquitoes fixed in 4% paraformaldehyde for the presence of infectious RVFV particles at various time points following infection and (2) demonstrate the utility of immunofluorescence assay (IFA) for the detection of RVFV antigen in various tissues of paraformaldehyde-fixed mosquitoes. Mosquitoes were administered an infectious blood meal containing one of two strains of RVFV, harvested at various time points following infection, intrathoracically inoculated with 4% paraformaldehyde, and fixed overnight at 4°C. The infection status of a subset of mosquitoes was verified by IFA on leg tissues prior to fixation, and infectivity of RVFV in fixed mosquito carcasses was determined by Vero cell plaque assay. Paraformaldehyde-fixed mosquitoes harvested 14 days post infection were also paraffin-embedded and sectioned for detection of RVFV antigen to particular tissues by IFA. None of the RVFV-exposed mosquitoes tested by Vero cell plaque assay contained infectious RVFV after fixation. Furthermore, incubation of mosquito sections with trypsin prior to antibody staining is recommended for optimal visualization of RVFV antigen in infected mosquito tissues by IFA.

Ebola virus infection inversely correlates with the overall expression levels of promyelocytic leukaemia (PML) protein in cultured cells

BACKGROUND

Ebola virus causes severe, often fatal hemorrhagic fever in humans. The mechanism of escape from cellular anti-viral mechanisms is not yet fully understood. The promyelocytic leukaemia (PML) associated nuclear body is part of the interferon inducible cellular defense system. Several RNA viruses have been found to interfere with the anti-viral function of the PML body. The possible interaction between Ebola virus and the PML bodies has not yet been explored.

RESULTS

We found that two cell lines, Vero E6 and MCF7, support virus production at high and low levels respectively. The expression of viral proteins was visualized and quantified using high resolution immunofluorescence microscopy. Ebola encoded NP and VP35 accumulated in cytoplasmic inclusion bodies whereas VP40 was mainly membrane associated but it was also present diffusely in the cytoplasm as well as in the euchromatic areas of the nucleus. The anti-VP40 antibody also allowed the detection of extracellular virions. Interferon-alpha treatment decreased the production of all three viral proteins and delayed the development of cytopathic effects in both cell lines. Virus infection and interferon-alpha treatment induced high levels of PML protein expression in MCF7 but much less in Vero E6 cells. No disruption of PML bodies, a common phenomenon induced by a variety of different viruses, was observed.

CONCLUSION

We have established a simple fixation and immunofluorescence staining procedure that allows specific co-detection and precise sub-cellular localization of the PML nuclear bodies and the Ebola virus encoded proteins NP, VP35 and VP40 in formaldehyde treated cells. Interferon-alpha treatment delays virus production in vitro. Intact PML bodies may play an anti-viral role in Ebola infected cells.

Expression of ICAM-1 on the Hantaan virus-infected human umbilical vein endothelial cells

OBJECTIVES

In HFRS, there is a varying degree of disseminated intravascular coagulation which was evident in the early phase of the illness. It is believed also that DIC would be the consequence, at least in part, of functional changes of endothelium resulting in kinin activation and clinical syndrome. This study investigated the role of adhesion molecule in the pathogenesis of Hantaan virus-related disease.

METHODS

The expression of ICAM-1 antigen on the cell membrane of human umbilical vein endothelial cells was assessed by immunohistochemistry, and ICAM-1 mRNA in the endothelial cells was assessed by in situ hybridization after Hantaan virus infection (2.6 x 10(4) PFU/mL) with the time course.

RESULTS

In immunohistochemistry, the number of ICAM-1 positive cells increased with time during the 12 or 24 hours after infection. 5 to 10% of HUVECs had been positive after 12-24 hours and the number of positive cells decreased abruptly after 24 hours. Hantaan antigen had been noticed after 12 hours focally on the HUVECs but continued to proliferate into day 7 post-infection when most of HUVECs were infected by Hantaan virus. In situ hybridization showed identical patterns of ICAM-1 mRNA expression after Hantaan virus infection.

CONCLUSION

It implies that the Hantaan virus infection on HUVECs would express more ICAM-1 on their surface and implicated in the pathogenesis of early clinical syndrome of HFRS.

Distribution of human herpesvirus 6 and varicella-zoster virus in organs of a fatal case with exanthem subitum and varicella

The distribution of human herpesvirus 6 (HHV-6) and varicella-zoster virus (VZV) was examined in autopsy samples from a fatal case with both virus infections. A 9-month-old boy developed convulsive seizures followed by macular skin rashes, rapidly progressed to brain death, and died 15 days after the onset, when signs of varicella were noted. An isolation of HHV-6 from blood and evaluation of antibody activities to various viral agents including HHV-6 were performed before his death. Postmortem examinations included: (i) isolation of HHV-6 and VZV from tissues or organs; (ii) detection of both virus antigens in tissues or organs by an indirect immunofluorescent assay using monoclonal antibodies to both viruses; (iii) amplification of both viruses and human herpesvirus 7 DNA sequences by a nested polymerase chain reaction assay; and (iv) endonuclease digestion of amplified products of HHV-6 DNA for differentation of variants A and B. Human herpesvirus 6 DNA was detected in peripheral blood mononuclear cells (PBMC) and plasma obtained at the eruptive stage but present only in PBMC 15 days after, indicating the primary infection with HHV-6, although the virus was not isolated from the same blood sample and a significant rise in the antibody titers to HHV-6 was not observed. Both virus antigens and DNA were detected in various tissues or organs obtained at autopsy, but only VZV was isolated from these samples, suggesting disseminated infection with both viruses in an infant. All the amplified products of HHV-6 DNA were variant B. Among the findings for the distribution of virus antigens, it was noteworthy that HHV-6 antigen was demonstrated in the endothelial cells of small vessels in the frontal lobe of the brain. There was no evidence of HHV-7 infection. These data indicate that the primary HHV-6 infection closely followed by the primary VZV infection had the potential hazard of an unexpected and apparently life-threatening event, in which disseminated infections with both viruses were noted in multiple tissues or organs including the brain.

The varicella vaccine. Vaccine development

In this article, rationales and method of development of attenuated live varicella (Oka) vaccine are described, with biologic and biophysical characteristics of the vaccine virus. The results of early clinical trials in Japan are also described, along with the results of detection of viremia in vaccinees and a follow-up of incidence of zoster in acute leukemic children, which indicate possible immunopathogenesis of varicella and zoster.

Detection of immunoreactive antigen, with a monoclonal antibody to measles virus, in tissue from a patient with Crohn's disease

Using immunofluorescence (IF), we investigated reactive antigens present in Crohn's disease patients with monoclonal antibodies derived from cells infected with measles virus, but not with the subacute sclerosing panencephalitis virus. During immunoblotting, one monoclonal antibody (mAb 86) reacted with a polypeptide with a molecular weight of 36,000 dalton (M; matrix protein) in measles virus-infected cells. This monoclonal antibody displayed a positive reaction only with tissues from patients with Crohn's disease by the IF test. It did not react with samples from patients with other chronic inflammatory bowel diseases, such as ulcerative colitis. Other monoclonal antibodies to the measles virus protein, and monoclonal antibodies to Herpes simplex virus type 1 did not react with the same tissue samples. The role of measles virus infection and/or a viral antigen (possibly the M protein) as a causative agent in Crohn's disease poses a challenging avenue for further research.

Varicella-zoster virus replication site in internal organs of an otherwise healthy child with varicella and sudden death

Pathological findings of an otherwise healthy 17 month old boy who was exposed to Varicella-zoster virus (VZV) in his family and unexpectedly died 3 days after onset of varicella are reported. They showed a disseminated VZV infection with involvement of skin, lung, liver, spleen, gastrointestinal tract and other organs where VZV antigen was detected by the enzyme-immunoassay with monoclonal antibodies to VZV. Since the subject was the full-term product of an uncomplicated pregnancy, who grew and developed normally, and had no symptoms or laboratory findings suggestive of immunodeficiency until his death, these findings suggest that many organs are involved as major internal sites of viral replication before or during infection of skin with VZV in the immunocompetent host.

Fatal encephalitis/encephalopathy in primary human herpesvirus-6 infection

An encephalitic illness with a fatal outcome occurred in a 9 month old girl with virologically confirmed exanthem subitum. Human herpes-virus-6 (HHV-6) DNA was found in the cerebrospinal fluid at the acute stage of the disease by the polymerase chain reaction, but the virus antigen was not detected in her brain tissue. This suggests that HHV-6-induced encephalitis/encephalopathy may be due to a non-infectious process.

Localization of herpes simplex virus type 1 in sebaceous glands of mice

The distribution of HSV-1 during the development of zosteriform skin lesions in SCID mice was analyzed by immunofluorescence and electron microscopy. The virus initially appeared within certain keratinocytes, sometimes surrounded by keratinocytes whose surfaces were also positive for the antigens, in the lower epidermal layers including the hair follicles, and then extended upward to the entire epidermis and downward to the sebaceous glands 1-2 days later, when no macroscopic skin lesion was seen. The affected epidermal cells subsequently degenerated and lost their viral antigens within a day, when the zosteriform lesion then became evident. This was followed by a degeneration of the dermis. The sebaceous glands eventually degenerated in 10 days, but some glands in the necrotic skin areas preferentially retained HSV-1. The horizontal spread of the virus in the epidermis beyond the first invaded dermatome occurred much later. In mice passively immunized with specific immune serum, viral antigens were observed even 20 days after the infection in sebaceous glands in necrotized areas. Therefore, HSV-1 appears to spread first via the extracellular fluid among the keratinocytes after being shed from nerve endings, and then produces a successive degeneration of the affected keratinocytes which may prevent any further extension of horizontal viral spread. The pilosebaceous apparatus is possibly acting as a site not only for the replication of HSV-1 with a delayed cytopathic effect, but also as an area that is temporarily sheltered from host defense mechanisms.

Current status and prospects of live varicella vaccine

Since its development in 1974 the Oka strain live attenuated varicella vaccine has been tested in healthy and immunocompromised adults and children. Its safety and efficacy have been established and it is now licensed for general use in Japan and Korea, and for immunocompromised patients in several other countries. Possibilities for the future include its use to prevent zoster in the elderly, its incorporation in a multivalent vaccine and its use as a vehicle to express foreign genes in recombinant vaccines.

Immunohistochemical study of skin lesions in herpes zoster

Thirty-seven biopsy skin tissues of herpes zoster taken from 27 patients were analysed immunohistochemically using two monoclonal antibodies detecting either nucleocapsid or glycoproteins of varicella-zoster virus (VZV) on paraffin sections of formalin fixed tissues. Skin lesions of herpes zoster were divided clinically into four stages: erythematous, vesicular, pustular and ulcerative. In the erythematous stage, VZV antigens, if detected, were found only within ballooning cells in the lower epidermis or follicular epithelium. In the vesicular stage, antigens were detected in the cells around and within the intraepidermal vesicles and in histiocytes or fibrocytes of the dermis in all cases and in the endothelial or perineural cells in 10 of 14 cases. In the pustular stage, the antigens were observed in degenerated or necrotic keratinocytes and multinucleated giant cells within pustules and some necrotic cells in the dermis. In the ulcerative stage, the viral antigens were detected only at the ulcer margin and around the hair shaft in 2 of 7 cases. These results suggest that VZV initially involves the epidermis in the erythematous stage, subsequently invades the dermis in the vesicular stage, and disappears in the early ulcerative stage.

Necrotizing tubulointerstitial nephritis associated with adenovirus infection

We report 10 autopsy cases of necrotizing tubulointerstitial nephritis induced by adenovirus (ADV). Hemorrhagic, necrotizing tubulitis with intranuclear inclusion bodies was observed in the kidneys of five bone marrow transplant recipients and five patients treated with intensive chemotherapy for malignancies (four cases of leukemia and one case of lung cancer). It was histopathologically demonstrated that necrobiotic tubular cells had inclusion-bearing cells of three types: "smudge cells," Cowdry A intranuclear inclusion cells, and full-type intranuclear-containing cells. Immunofluorescent examination with anti-ADV antibody demonstrated specific fluorescence on the affected tubular cells of all 10 kidneys. Specific antigens for ADV type 11 were also revealed in all but one case by an immunofluorescent test using type-specific antiserum and convalescent serum containing high titer antibody to this serotype. Electron microscopy revealed intranuclear crystalline arrays of viral particles, 75 to 80 nm in diameter, in each of the seven cases examined. Extrarenal involvement, indicated by ADV-induced cytopathologic change, was confined to bladder or prostate. Hemorrhagic cystitis was recorded in all the bone marrow transplant cases as well as in one leukemia case. Adenovirus type 11 was isolated from urine in all five cases tested during these episodes. Renal failure was ascribed to ADV infection in two of five patients who died from renal dysfunction. The presence of hemorrhagic cystitis and localization of invasive infection in urogenital organs suggested that renal infection might occur by ascending route from the bladder. We propose that ADV should be added as a viral agent to the pathogenetic list of tubulointerstitial nephritis.

Disseminated adenovirus (type 19) infection in a neonate. Rapid detection of the infection by immunofluorescence

A case of fatal disseminated adenovirus infection in a neonate who suffered from severe keratoconjunctivitis and pneumonitis is reported. The diagnosis was made seven days after the onset of illness based on the detection of adenovirus antigen in the smears of the tracheal suction and conjunctival swab by immunofluorescence. Viral antigen was detected in the frozen or formalin-fixed autopsy specimens of the lungs, kidneys, spleen, liver and lymph nodes. Typical crystal arrangement of adenovirus virions was observed in the alveolar epithelial cells by electron microscopy. The isolated virus was identified to be of type 19 by a neutralization test. The IF examination using adenovirus group specific immune reagents on the smears of clinical specimens appears to be useful for rapid diagnosis of viral infections.

Experimental labyrinthitis in rats caused by infecting with virus causing hemorrhagic fever with renal syndrome (HFRS)

Acute and persistent viral infection of the inner ear of rats was induced with hemorrhagic fever with renal syndrome (HFRS) virus following intraperitoneal inoculation. Newborn (within 24 h after birth) rats were inoculated intraperitoneally (i.p.) with HFRS virus (B-1 strain), and the cochlea was examined using an immunohistochemical technique for the localization of viral antigens 1 week (acute infection) and 1 year (persistent infection) after infection. Virus-specific antigens were detected in the inner ear structures of the rats suffering from both acute and persistent infection. Morphological changes in the inner ear structures of these rats were observed, with hemorrhage and infiltration of lymphocytes and macrophages. Moreover virus could be isolated from the blood of all infected rats. In the present study, we have proved that HFRS virus can infect the inner ear via the viremia.

Cytomegalovirus oophoritis with cortical necrosis during remission of acute lymphocytic leukemia

Ovarian involvement of cytomegalovirus (CMV) is rarely observed in autopsy and biopsy materials. Cortical necrosis of the ovaries was found in an autopsy case with generalized CMV infection. The patient was an 11-year-old girl in a remission state of acute lymphocytic leukemia. Autopsy revealed several areas showing necrotic change up to 2 mm in size in the cortex of both ovaries. Many cytomegalic cells were found in both the necrotic and intact areas of the cortex. CMV had infected the granulosa, thecal and stromal cells as well as vascular endothelial cells. Oocytes of neither primary nor graafian follicles showed cytomegalic changes, although they were destroyed due to the necrosis. CMV antigen was immunohistologically detected in these cytomegalic cells. Ultrastructurally, herpesvirus-type particles were revealed in the nuclei and cytoplasm of the cytomegalic cells. This case demonstrated that ovarian infection with CMV can potentially induce cortical necrosis and decrease the number of oocytes.

Experimental herpes simplex virus and cytomegalovirus labyrinthitis

Herpes simplex virus (HSV) and guinea pig cytomegalovirus (GPCMV) were inoculated into the middle ear of guinea pigs. The routes of passage of middle ear infection to the inner ear are hematogenous and/or via the cochlear windows. The presence of GPCMV inclusion body-bearing cells within the cochlea strongly suggests the hematogenous route, as in some animals the inner ear does not show cell infiltration and precipitate. When viral infection approaches the cochlear windows, the first morphological changes observed are the presence of precipitate in the inner ear fluids and the appearance of macrophages. These changes are particularly marked near the windows. Direct invasion of the infection into the inner ear after rupture of the round window membrane results in hemorrhage and marked cell infiltration. Inclusion body-bearing cells are found scattered within the exudate. Possible emperipolesis is frequently observed. No cells or tissues can escape involvement in viral labyrinthitis. Fibrosis and ossification eventually occur. Anomaly of the cochlea, the mirror image of the organ of Corti, was observed in the offspring of a guinea pig in whom cytomegalovirus was inoculated into the inner ear.

Acute pancreatitis with cytomegalovirus infection

An autopsy case of necrotizing pancreatitis with cytomegalovirus (CMV) infection is reported. A 50-year-old housewife was admitted because of malignant choroid plexus papilloma of the fourth ventricle. Serum amylase transiently elevated during irradiation and chemotherapy for brain tumor, one month before death. The patient died of a respiratory failure. At autopsy focal necrosis was mainly observed in the peripancreatic adipose tissue and occasionally in the parenchyma of the tail. Fibrosis and inflammatory infiltration was found around the necrosis and interstitium. Cytomegalic cells with intranuclear inclusions and/or cytoplasmic granules were observed frequently in the acini near the necrosis. Immunohistological study revealed CMV antigen in the cytomegalic cells. Herpesvirus-type particles were observed in the nucleus and cytoplasm of the cytomegalic cells. CMV infection of the acini are thought to cause necrotic changes in the pancreas.

Alimentary tract lesions in cytomegalovirus infection

Ten autopsy and 2 biopsy cases of cytomegalovirus (CMV) infection of the alimentary tract were studied. CMV infection was microscopically determined by the presence of cytomegalic inclusion as well as by the immunofluorescent method. Clinical manifestations such as abdominal pain, diarrhea, hematemesis, bloody stool, perforation, and/or abdominal distension with paralytic ileus were observed in 8 autopsy cases and 1 biopsy case. Disappearance of cytomegalic cells was confirmed by the follow-up study in the biopsy cases. Macroscopically, mucosal hemorrhage or ulceration was found in the gastrointestinal tract from the esophagus to the colon. Ulceration showed a characteristic well-defined punched-out appearance. The esophagus was the most frequently involved organ. However, no cytomegalic cells were found in the squamous epithelium. In the stomach, regenerated epithelial cells were frequently involved in the deeper part of glands. Numerous endothelial cells transformed into cytomegalic cells in the mucosa surrounding the ulcer in the esophagus, stomach, and intestine. Ischemia caused by cytomegalic changes of vascular endothelial cells is thought to play an important role in the pathogenesis of the ulcer of the gastrointestinal tract.

An animal model of type-1 herpes simplex virus infection of facial nerve

As the pathogenesis of Bell's palsy, herpes simplex virus (HSV) infection has been suggested on the basis of several serological studies. To clarify and analyse the pathogenic mechanisms of this disease, guinea pigs were inoculated with type-1 HSV through natural infection routes into the peripheral areas innervated by facial nerve, and nervous tissues were examined by histopathological and immunohistochemical methods. HSV-I infection in the nasal mucosa, tongue, oral muscles and auricles brought about neither clinical facial palsy nor disturbed Preyer or corneal reflexes, but viral antigens in the inoculated peripheral areas, facial and trigeminal ganglia and pons with inflammatory cell response, hemorrhages and degeneration and necrosis. Cyclophosphamide treatment resulted in disturbed Preyer and corneal reflexes and enhanced the incidence of antigen appearance and histopathological changes.

Analysis of viral antigens in giant cells of measles pneumonia by immunoperoxidase method

The localization of measles virus proteins was analyzed by immunoperoxidase method using both monospecific and monoclonal antibodies. In Vero cells infected with the Edmonston or EB-L strain, the former being a laboratory strain and the latter a fresh isolate from a measles patient, nucleocapsid protein was located in the nuclei, and matrix protein, phosphoprotein, haemagglutinin and fusion protein were located in the cytoplasm. In the lung tissues of eight cases with measles giant cell pneumonia, the similar findings were obtained. The presence of haemagglutinin on the surface of giant cells at the luminal side was also noticed. Histopathologically, measles giant cells had nuclear and cytoplasmic eosinophilic inclusion bodies with some differences in appearance. The significance of localization of viral proteins is discussed in comparison with histopathological findings in measles giant cells.

Activation of cytomegalovirus infection in immunosuppressed cynomolgus monkeys inoculated with varicella-zoster virus

A systemic activated cytomegalovirus (CMV) infection was fortuitously detected in almost all monkeys which had been immunosuppressed with antithymocyte globulin (ATG), cyclophosphamide (CY), and cortisone acetate (CS) before and after experimental inoculation with varicella-zoster virus (VZV). They developed exudative pneumonia, and the lesions in visceral organs and tissues contained cytomegalic cells with intranuclear inclusion bodies, in which viral antigens, specific for CMV, but not inoculated VZV, were detected by immunofluorescence. Serological study of paired sera from these monkeys ascertained preexisting CMV infection. Under the present experimental conditions, this infection was highly reproducible and always occurred within three, but not two, weeks of immunosuppression in monkeys inoculated with VZV. We therefore examined the host factors involved in activation of latent CMV. The immunocompetence of the host was destroyed almost completely with treatment of ATG, CY, and CS, but not with combinations of two of these agents, revealing the systemic depletion of lymphoid cells in tissues including the thymus medulla. Although the role of VZV in the induction of CMV remains uncertain, the heterologous VZV inoculum may have produced some effects equivalent to the allogeneic reaction to release latent CMV. These monkeys may represent an animal model of "opportunistic" CMV infection in immunocompromised and/or allografted humans.

A genetic determinant required for continuous reinfection of adjacent cells on large plasmid in S. flexneri 2a

We have identified a region (virG) on the 230 kb virulence plasmid of S. flexneri that is required for cell-to-cell spread of the bacterium. Tn5 insertions into this region result in avirulent mutants that can initially invade and multiply in epithelial cells, but tend to lose active movement and tend to localize within the cytoplasm, where they are gradually extinguished without infecting adjacent cells. The virG region was localized to within 4 kb and may contain a single cistron. Sequences hybridizing to this region were found in all intact virulence plasmids of Shigellae and enteroinvasive E. coli.

Immunocytochemical methods for demonstrating canine distemper virus antigen in aldehyde-fixed paraffin-embedded tissue

The effects of enzymatic digestion, sodium borohydride reduction, acids used in decalcification procedures and techniques for inactivation of endogenous peroxidase were sequentially evaluated for their effect on the immunoreactivity of canine distemper virus in aldehyde-fixed paraffin-embedded tissue. Enzyme digestion improved immunoreactivity while sodium borohydride reduced background staining. Paraformaldehyde-glutaraldehyde-fixed tissues required thioglycolic acid treatment prior to enzyme digestion and sodium borohydride reduction to obtain results comparable to results obtained in formalin-fixed tissues. Detailed protocols for indirect immunofluorescence and the avidin-biotin-peroxidase complex procedure are provided.

The use of mice in the Sereny test as a virulence assay of shigellae and enteroinvasive Escherichia coli

We examined the possibility that mice could be used in the Sereny test instead of guinea pigs or rabbits. Although the reactions in mice were more transient and not as pronounced as those in guinea pigs, mice indeed could be used to distinguish even macroscopically between virulent and avirulent shigellae. Virulent enteroinvasive Escherichia coli strains were also positive for the mouse Sereny test. We described the macroscopic and microscopic appearance of the mouse eyes. Thus, mice are recommended for use in the Sereny test, particularly when a large number of samples are to be tested.

Cochlear changes after herpes simplex virus infection

After direct inoculation of herpes simplex virus (HSV) into the scala tympani of the guinea pig, the tectorial membrane showed various morphological changes: atrophy, roll-up and dot formation. Immunofluorescent and electronmicroscopic studies revealed that the changes were due to HSV infection. The findings were compared with those observed in the temporal bones of a 77-year-old patient who suffered from sudden deafness. The tectorial membranes of both temporal bones showed various changes identical with those observed in experimental viral labyrinthitis. This supports the view that sudden deafness in this particular patient was of viral origin. In the animal experiment, HSV antigen could be detected from the cochlea of the non-inoculated side, which was morphologically normal. Further study is required to reactivate HSV in the cochlea with latent infection. This animal can probably be used as an animal model for sudden deafness.

Myocardial lesions by Coxsackie virus B3 and cytomegalovirus infection in infants

Immunofluorescent and electron-microscopic studies were performed to determine the distribution of viral antigens and particles and to clarify the relationship to myocardial lesions in two autopsy cases with generalized infection of Coxsackie virus B3 (CVB3) or cytomegalovirus (CMV). Case 1 was a full-term newborn female infant, without any congenital anomalies, who died of cardiac failure 10 days after birth. CVB3 was isolated from the blood before death. Necrosis of the muscle fibers was observed, frequently accompanying calcification. Numerous histiocytes and a few lymphocytes and neutrophils had infiltrated in and around the necrotic areas. Immunofluorescent study (IF) revealed CVB3 antigen in the muscle fibers and vascular endothelial cells. Case 2 was a female infant, born at 28 weeks of gestation, who died of fatal arrhythmia 50 days after birth. The infant had hemocephalus and a history of idiopathic respiratory distress and underwent an operation for patent ductus arteriosus. Cytomegalic cells were frequently found in the vascular endothelial cells in the myocardium and occasionally in muscle fibers. IF showed the presence of CMV antigen in both endothelial cells and muscle fibers. CVB3 and CMV antigens were detected predominantly in vascular endothelial cells rather than in the muscle fibers. Blood flow disturbance due to endothelial damage is a cause of the myocardial lesion in addition to the direct invasion of the muscle fibers by the virus.

Experimental infection in newborn mice and rats by hemorrhagic fever with renal syndrome (HFRS) virus

Newborn mice and rats were inoculated intracerebrally (ic) or intraperitoneally (ip) with Hantaan virus (76-118 strain) or HFRS-related virus (B-1 strain). The mortality and the influence on the increase of body weight in newborn mice were higher in the groups infected with the 76-118 strain than in the groups infected with the B-1 strain, while the B-1 strain was more virulent in rats than the 76-118 strain. Virus isolation from rats inoculated with either strain was attempted 7 and 11 weeks after inoculation. Virus could be isolated from various organs of rats infected with the B-1 strain, while it was recovered from only the brain and lungs of rats infected with the 76-118 strain. Viral antigen was readily detected in various organs of rats infected with the B-1 strain, but the amount and distribution of antigens were less in rats infected with the 76-118 strain. Our results suggest that the virulence of HFRS-related virus is variable, depending on the species of infected animals as well as on the virus strains. The virus also persists in the injected animals with high titers of antibodies for at least 11 weeks.