Combined fluorescent-antibody and electron microscopy study of Marek's disease virus-infected cell culture

Countering Zika Virus: The USAMRIID Response

The United States Army Medical Research Institute of Infectious Diseases (USAMRIID) possesses an array of expertise in diverse capabilities for the characterization of emerging infectious diseases from the pathogen itself to human or animal infection models. The recent Zika virus (ZIKV) outbreak was a challenge and an opportunity to put these capabilities to work as a cohesive unit to quickly respond to a rapidly developing threat. Next-generation sequencing was used to characterize virus stocks and to understand the introduction and spread of ZIKV in the United States. High Content Imaging was used to establish a High Content Screening process to evaluate antiviral therapies. Functional genomics was used to identify critical host factors for ZIKV infection. An animal model using the temporal blockade of IFN-I in immunocompetent laboratory mice was investigated in conjunction with Positron Emission Tomography to study ZIKV. Correlative light and electron microscopy was used to examine ZIKV interaction with host cells in culture and infected animals. A quantitative mass spectrometry approach was used to examine the protein and metabolite type or concentration changes that occur during ZIKV infection in blood, cells, and tissues. Multiplex fluorescence in situ hybridization was used to confirm ZIKV replication in mouse and NHP tissues. The integrated rapid response approach developed at USAMRIID presented in this review was successfully applied and provides a new template pathway to follow if a new biological threat emerges. This streamlined approach will increase the likelihood that novel medical countermeasures could be rapidly developed, evaluated, and translated into the clinic.

Marek's disease virus morphogenesis

Marek's disease virus (MDV) is a highly contagious virus that induces T-lymphoma in chicken. This viral infection still circulates in poultry flocks despite the use of vaccines. With the emergence of new virulent strains in the field over time, MDV remains a serious threat to the poultry industry. More than 40 yr after MDV identification as a herpesvirus, the visualization and purification of fully enveloped infectious particles remain a challenge for biologists. The various strategies used to detect such hidden particles by electron microscopy are reviewed herein. It is now generally accepted that the production of cell-free virions only occurs in the feather follicle epithelium and is associated with viral, cellular, or both molecular determinants expressed in this tissue. This tissue is considered the only source of efficient virus shedding into the environment and therefore the origin of successful transmission in birds. In other avian tissues or permissive cell cultures, MDV replication only leads to a very low number of intracellular enveloped virions. In the absence of detectable extracellular enveloped virions in cell culture, the nature of the transmitted infectious material and its mechanisms of spread from cell to cell remain to be deciphered. An attempt is made to bring together the current knowledge on MDV morphogenesis and spread, and new approaches that could help understand MDV morphogenesis are discussed.

Comparison of blood and feather pulp samples for the diagnosis of Marek's disease and for monitoring Marek's disease vaccination by real time-PCR

Comparison of blood and feather pulp (FP) samples for the diagnosis of Marek's disease (MD) and for monitoring Marek's diseases vaccination in chickens (serotypes 2 and 3 vaccines) by real time-PCR was evaluated. For diagnosis of MD, quantification of serotype 1 Marek's disease virus (MDV) DNA load was evaluated in 21 chickens suffering from MD. For each chicken, samples of blood and FP were collected and MDV DNA load was quantified. Solid tumors are the sample of choice for MD diagnosis by real time-PCR and, hence, 14 solid tumors were included in the study as positive controls. Load of MDV DNA in FP was equivalent to that detected in solid tumors (threshold cycle [Ct] ratio above 1.7). MDV DNA load in blood samples was lower than in solid tumors and FP samples. Nonetheless, there was a statistically significant correlation of the results obtained from FP and blood (r = 0.92). Results of the Pearson correlation test showed that Ct ratio values of 1.7 in FP correspond to Ct ratio values of 1.2 in peripheral blood. For monitoring vaccines, serotypes 2 and 3 MDV DNA load was evaluated in blood and FP samples of vaccinated chickens. Serotype 2 MDV DNA load was evaluated in samples of blood and FP from 34 chickens vaccinated with SB-1 strain. Serotype 3 MDV DNA load was evaluated in blood and FP samples from 53 chickens vaccinated with HVT strain. For both serotypes, frequency of positive samples and load of vaccine DNA was higher in FP than in blood samples. There was not a statistically significant correlation between the load of SB-1 DNA (r = 0.17) or HVT DNA (r = -0.04) in FP and blood. Our results show that the load of serotypes 1, 2, and 3 DNA is higher in FP than in blood. Diagnosis of MD could be done using both FP and blood samples. Monitoring of MD vaccination by real time-PCR required the use of FP samples. There were a high percentage of false negative samples when using blood to detect serotypes 2 and 3 MDV by real time-PCR.

Anatid herpesvirus 1 CH virulent strain induces syncytium and apoptosis in duck embryo fibroblast cultures

Anatid herpesvirus 1 (AHV-1) CH virulent strain was first isolated from an infected duck and it was found that this virus strain could induce cytopathic effect (CPE) in duck embryo fibroblast (DEF). Following AHV-1 infection, DEF showed morphological changes such as cell rounding, improved refractivity and detachment from the culture surface. However, its pathological characteristics were not adequately known. Related studies were performed and the results showed that syncytium formation could be observed as the other type of CPE in AHV-1 infection. Hematoxylin-eosin staining and 4', 6-diamidino-2-phenylindole (DAPI) staining of infected DEF were each used to visualize the shape and distribution of chromatin within nuclei and nuclear fragmentation was observed. Chromatin condensation and margination, as well as formation of apoptotic bodies were observed by transmission electron microscopy (TEM). DNA ladder formation was detected in AHV-1 infected cells and apoptosis of the infected DEF was also detected by flow cytometry analysis of Annexin V-FITC/PI staining method. Therefore, it was suggested that AHV-1 virulent strain can induce syncytium and apoptosis in DEF. Syncytium formation and apoptosis observed in this study may contribute to the elucidation of AHV-1 pathogenesis.

Transactivation of latent Marek's disease herpesvirus genes in QT35, a quail fibroblast cell line, by herpesvirus of turkeys

The QT35 cell line was established from a methylcholanthrene-induced tumor in Japanese quail (Coturnix coturnix japonica) (C. Moscovici, M. G. Moscovici, H. Jimenez, M. M. Lai, M. J. Hayman, and P. K. Vogt, Cell 11:95-103, 1977). Two independently maintained sublines of QT35 were found to be positive for Marek's disease virus (MDV)-like genes by Southern blotting and PCR assays. Sequence analysis of fragments of the ICP4, ICP22, ICP27, VP16, meq, pp14, pp38, open reading frame (ORF) L1, and glycoprotein B (gB) genes showed a strong homology with the corresponding fragments of MDV genes. Subsequently, a serotype 1 MDV-like herpesvirus, tentatively name QMDV, was rescued from QT35 cells in chicken kidney cell (CKC) cultures established from 6- to 9-day-old chicks inoculated at 8 days of embryonation with QT35 cells. Transmission electron microscopy failed to show herpesvirus particles in QT35 cells, but typical intranuclear herpesvirus particles were detected in CKCs. Reverse transcription-PCR analysis showed that the following QMDV transcripts were present in QT35 cells: sense and antisense meq, ORF L1, ICP4, and latency-associated transcripts, which are antisense to ICP4. A transcript of approximately 4.5 kb was detected by Northern blotting using total RNA from QT35 cells. Inoculation of QT35 cells with herpesvirus of turkeys (HVT)-infected chicken embryo fibroblasts (CEF) but not with uninfected CEF resulted in the activation of ICP22, ICP27, VP16, pp38, and gB. In addition, the level of ICP4 mRNA was increased compared to that in QT35 cells. The activation by HVT resulted in the production of pp38 protein. It was not possible to detect if the other activated genes were translated due to the lack of serotype 1-specific monoclonal antibodies.

Antigenic difference between intracellular and membrane antigens induced by herpesvirus of turkeys

The difference between intracellular antigen (IA) and membrane antigen (MA) induced by herpesvirus of turkeys (HVT) was examined by immunofluorescence analysis. Convalescent sera from chickens infected with HVT (HVT convalescent serum) and hyperimmune sera from chickens immunized with partially pruified virus (anti-HVT particle serum) or with a major HVT soluble precipitin antigen (anti-common Ag serum) were used as the source of antisera to specify both antigens in these experiments. Absorption of a convalescent serum from HVT-inoculated chicken with IA positive cells, resulted in reduction of their reactivity to IA but not to MA. Differential absorption of the hyperimmune sera by IA positive cells and MA positive cells resulted in reduction of their reactivity to homologous cells but not to heterlogous cells which were used in the absorptions. When the relationship between the levels of anti-IA and anti-MA antibodies was examined by a blocking immunofluorescence test using 38 sera from chickens inoculated with HVT, no correlation was observed (p greater than 0.25). These results provide evidence that MA and IA are antigenically different from each other.

[Structure and function of virus-induced antigens in cultured cells infected with Merek's disease and turkey herpes viruses. II. Isolation of intracellular antigens from infected cells (author's transl)]

Virus-induced antigens were isolated from MDV and HVT-infected cells by salt extraction with 3M KCl and purified by Con.A chromatography and isoelectric focusing. Electrophoretic analysis of 35S-methionine, 3H-fucose and 32P-orthophosphate labeled antigens revealed 7 different polypeptides, two of them containing labeled carbohydrates, and one phospholipid component. The isolated virus-induced antigens from infected cells were identified as serologically active membrane complexes carrying common antigenic determinants of MDV and HVT. They were able to bind to virus-neutralizing immunglobulins as shown by antibody binding tests. Summarizing the presented analytic and serologic findings it was proposed to classify MDV and HVT as different serotypes of a common Marek's disease virus group.

Marek's disease in Japanese quail -- a pathological, virological and serological study

Experimental studies were performed to see whether Japanese quail (Coturnix coturnix japonica) are susceptible to JM strain of Marek's disease virus (MDV). In three identical trials, a total of 120, one-day-old quail were inoculated intra-abdominally with 0.2 ml. of chicken blood infected with MDV (JM strain) and raised in FAPP isolators. Uninfected controls were inoculated with normal saline only and raised separately. During the 18-week post infection observation period, 65-80% of the infected quail died within six weeks, while the highest mortality in control groups was only 0-5%. In each trial, ocular lesions with or without unilateral or bilateral blindness and signs of torticollis were evident in a few quail after 10-14 weeks. Gross and microscopic lesions suggestive of MD were observed 14 days on. The most pronounced lesions were observed in lungs. Neural tissues were least affected. In general, females were more susceptible than males. MD-specific fluorescent and precipitating antigens were detected in different visceral tissues, buffy coat and cultured macrophages of infected quail. Fluorescent antigen appeared at 6-7 days after infection, whereas precipitating antigen appeared after 12-15 days. Viral (MDV) infectivity tests in cell cultures and bioassay in one-day-old chicks and quail demonstrated that infected quail become viremic around the seventh day post infection. A cytopathic agent similar to MDV was also isolated from quail. Neither Newcastle disease virus nor a bacterial agent was isolated from the quail. MD-specific fluorescent precipitating antibodies were present in the egg yolk and plasma of both infected sick and infected symptomless quail. The earliest detectable plasma MD antibody appeared in 14-21 days. Such findings were not observed in quail from parent stock and controls. Our studies demonstrated that Japanese quail are susceptible to JM strain of MDV.

Isolation and characterization of a herpesvirus from leukemic guinea pigs

A guinea pig herpesvirus (GPHV) has consistently been isolated from leukemic lymphoblasts of strain-2 guinea pigs. GPHV is serologically related to the guinea pig herpes-like virus isolated by Hsiung and Kaplow. The virions of GPHV consist of an icosahedral capsid containing a dense nucleoprotein core enclosed in a double-layered membrane. The average diameters of GPHV virion and capsid were 166 and 101 nm, respectively. Studies on the morphogenesis of GPHV revealed that, as in other herpesvirus infections, only the naked capsids with or without the nucleoprotein core were found in the infected cell nuclei; it was also learned that the virion acquired its envelope by budding from the nuclear membrane of the infected cells. However, GPHV-infected cell nuclei also contained dense fibrous rods, resembling nucleo-protein core outside the capsids, and tubules resembling viral core protein. The capsids were often embedded in dense granular antigen. GPHV deoxyribonucleic acid (DNA) has a density of 1.716 g/ml in cesium chloride compared to herpes simplex virus DNA (rho = 1.728 g/ml) and cellular DNA (rho = 1.700 g/ml).