Defective Interfering Particles of Negative-Strand RNA Viruses

Viral defective interfering particles (DIPs) were intensely studied several decades ago but research waned leaving open many critical questions. New technologies and other advances led to a resurgence in DIP studies for negative-strand RNA viruses. While DIPs have long been recognized, their exact contribution to the outcome of acute or persistent viral infections has remained elusive. Recent studies have identified defective viral genomes (DVGs) in human infections, including respiratory syncytial virus and influenza, and growing evidence indicates that DVGs influence disease severity and may contribute to viral persistence. Further, several studies have advanced our understanding of key viral and host factors that regulate DIP formation and activity. Here we review these discoveries and highlight key questions moving forward.

NEDD4 family ubiquitin ligases associate with LCMV Z's PPXY domain and are required for virus budding, but not via direct ubiquitination of Z

Viral late domains are used by many viruses to recruit the cellular endosomal sorting complex required for transport (ESCRT) to mediate membrane scission during viral budding. Unlike the P(S/T)AP and YPX_(1–3)L late domains, which interact directly with the ESCRT proteins Tsg101 and ALIX, the molecular linkage connecting the PPXY late domain to ESCRT proteins is unclear. The mammarenavirus lymphocytic choriomeningitis virus (LCMV) matrix protein, Z, contains only one late domain, PPXY. We previously found that this domain in LCMV Z, as well as the ESCRT pathway, are required for the release of defective interfering (DI) particles but not infectious virus. To better understand the molecular mechanism of ESCRT recruitment by the PPXY late domain, affinity purification-mass spectrometry was used to identify host proteins that interact with the Z proteins of the Old World mammarenaviruses LCMV and Lassa virus. Several Nedd4 family E3 ubiquitin ligases interact with these matrix proteins and in the case of LCMV Z, the interaction was PPXY-dependent. We demonstrated that these ligases directly ubiquitinate LCMV Z and mapped the specific lysine residues modified. A recombinant LCMV containing a Z that cannot be ubiquitinated maintained its ability to produce both infectious virus and DI particles, suggesting that direct ubiquitination of LCMV Z alone is insufficient for recruiting ESCRT proteins to mediate virus release. However, Nedd4 ligases appear to be important for DI particle release suggesting that ubiquitination of targets other than the Z protein itself is required for efficient viral ESCRT recruitment.

Enveloped viruses derive their lipid bilayer from either the cellular plasma membrane or an intracellular organelle during the process of viral budding in which a virus particle is formed at a membrane. Many enveloped viruses recruit the cellular endosomal sorting complex required for transport (ESCRT) in order to efficiently cut the membrane that connects a newly budded, but not released, virus particle from its parent membrane. Late domains, which are short protein motifs found in numerous enveloped viruses, specifically recruit ESCRT for this process. Two types of late domains accomplish this by binding directly to ESCRT proteins. A third late domain, PPXY, recruits ESCRT proteins through an unknown, indirect linkage. In this study, we sought to identify proteins that may bridge the PPXY late domain and ESCRT proteins. We found that Nedd4 family ubiquitin ligases interact with the PPXY domain in the mammarenavirus Z protein resulting in ubiquitination of Z at two lysine residues. However, Z ubiquitination was largely dispensable for the virus. Conversely, Nedd4 ubiquitin ligases were critical during infection suggesting that the most important contribution made to virus release by Nedd4 ligases is not direct ubiquitination of the viral matrix protein, but possibly the ubiquitination of cellular proteins or other viral proteins.

The use of novel epitope-tagged arenaviruses reveals that Rab5c-positive endosomal membranes are targeted by the LCMV matrix protein

We report the development of recombinant New World (Junín; JUNV) and Old World (lymphocytic choriomeningitis virus; LCMV) mammarenaviruses that encode an HA-tagged matrix protein (Z). These viruses permit the robust affinity purification of Z from infected cells or virions, as well as the detection of Z by immunofluorescent microscopy. Importantly, the HA-tagged viruses grow with wild-type kinetics in a multi-cycle growth assay. Using these viruses, we report a novel description of JUNV Z localization in infected cells, as well as the first description of colocalization between LCMV Z and the GTPase Rab5c. This latter result, when combined with our previous findings that LCMV genome and glycoprotein also colocalize with Rab5c, suggest that LCMV may target Rab5c-positive membranes for preassembly of virus particles prior to budding. The recombinant viruses reported here will provide the field with new tools to better study Z protein functionality and identify key Z protein interactions with host machinery.

Host-Driven Phosphorylation Appears to Regulate the Budding Activity of the Lassa Virus Matrix Protein

Lassa mammarenavirus (LASV) is an enveloped RNA virus that can cause Lassa fever, an acute hemorrhagic fever syndrome associated with significant morbidity and high rates of fatality in endemic regions of western Africa. The arenavirus matrix protein Z has several functions during the virus life cycle, including coordinating viral assembly, driving the release of new virus particles, regulating viral polymerase activity, and antagonizing the host antiviral response. There is limited knowledge regarding how the various functions of Z are regulated. To investigate possible means of regulation, mass spectrometry was used to identify potential sites of phosphorylation in the LASV Z protein. This analysis revealed that two serines (S18, S98) and one tyrosine (Y97) are phosphorylated in the flexible N- and C-terminal regions of the protein. Notably, two of these sites, Y97 and S98, are located in (Y97) or directly adjacent to (S98) the PPXY late domain, an important motif for virus release. Studies with non-phosphorylatable and phosphomimetic Z proteins revealed that these sites are important regulators of the release of LASV particles and that host-driven, reversible phosphorylation may play an important role in the regulation of LASV Z protein function.

Visualization of the lymphocytic choriomeningitis mammarenavirus (LCMV) genome reveals the early endosome as a possible site for genome replication and viral particle  pre-assembly

We report a fluorescence in situ hybridization (FISH) assay that allows the visualization of lymphocytic choriomeningitis mammarenavirus (LCMV) genomic RNAs in individual cells. We show that viral S segment genomic and antigenomic RNA, along with viral nucleoprotein, colocalize in subcellular structures we presume to be viral replication factories. These viral RNA structures are highly dynamic during acute infection, with the many small foci seen early coalescing into larger perinuclear foci later in infection. These late-forming perinuclear viral RNA aggregates are located near the cellular microtubule organizing centre and colocalize with the early endosomal marker Rab5c and the viral glycoprotein in a proportion of infected cells. We propose that the virus is using the surface of a cellular membrane-bound organelle as a site for the pre-assembly of viral components, including genomic RNA and viral glycoprotein, prior to their transport to the plasma membrane, where new particles will bud.

A novel phosphoserine motif in the LCMV matrix protein Z regulates the release of infectious virus and defective interfering particles

We report that the lymphocytic choriomeningitis virus (LCMV) matrix protein, which drives viral budding, is phosphorylated at serine 41 (S41). A recombinant (r)LCMV bearing a phosphomimetic mutation (S41D) was impaired in infectious and defective interfering (DI) particle release, while a non-phosphorylatable mutant (S41A) was not. The S41D mutant was disproportionately impaired in its ability to release DI particles relative to infectious particles. Thus, DI particle production by LCMV may be dynamically regulated via phosphorylation of S41.

Detection of therapeutically relevant diagnoses made by sonography of the upper abdomen: portable versus high-end sonographic units -- a prospective study

AIM

To compare the efficiency of a portable sonographic unit with a high-end unit used for sonographic examinations of the upper abdomen to detect therapeutically relevant diagnoses and to answer clinical questions.

METHODS

Over a period of five years, 575 patients were examined by four examiners as part of the daily routine work. Patients without known diagnoses were examined first with the portable SonoSite 180 system, with documentation of the findings and diagnoses, and immediately thereafter with the high-end Philips HDI 5000 system. Subsequently, any discrepant findings and diagnoses were recorded. The assessment was confined to therapy-demanding diagnoses and to the resolution of the clinical question (major findings) as well as to other therapeutically relevant findings (minor findings).

RESULTS

Of the 575 data sets (duplicated examinations), 574 could be evaluated. The major findings coincided in 447 (78 %) of 574 cases and were discrepant in 121 (22 %) cases in which the major findings were solely detected with the high-end Philips HDI 5000 system and missed with the portable SonoSite 180 system. Findings of the upper abdomen coincided in 252 (85 %) of 297 cases and were undetectable with the portable unit in 44 (15 %) cases. For 166 intestinal examinations, the proportion of coinciding major findings was 58 % (96 of 166 cases), with 42 % (71 of 166 cases) overlooked with the portable unit. For examinations of the pleura, the findings coincided in 99 (89 %) of 111 cases. The findings of emergency examinations coincided in 138 (75 %) of 185 cases, with 47 (25 %) findings exclusively detected with the HDI 5000 system. In emergencies without intestinal involvement, the findings coincided in 105 (89 %) of 118 cases.

CONCLUSION

As expected, the high-end unit is markedly superior to the portable sonographic unit, especially for clinical questions requiring a high physical resolution, as needed for gastrointestinal structures, biliary system and pancreas. The portable unit provided its best results for examinations of the pleura and for emergency examinations as long as the gastrointestinal tract is excluded. For the routine use of portable sonographic units, it is important to know the limitation of the particular unit.

Endoscopy: a minimally invasive procedure for diagnosis and treatment of diseases of the salivary glands

During a 6-year period we did a total of 72 videoendoscopies of the salivary glands and their associated ductal systems. This minimally invasive procedure is associated with little morbidity and discomfort. The main indication was sialolithiasis of the submandibular and parotid glands. Sialoendoscopy was used not only for diagnosis of radiolucent calculi but also for simultaneous removal of calculi. Sialoendoscopy was also of benefit in the diagnosis and treatment of other diseases of the salivary glands. Even patients with chronic sialadenitis could be helped with endoscopic dilatation of the causative sialostenosis, thereby enabling us to conserve the gland.

Clinical indications for digital volume tomography in oral and maxillofacial surgery

Digital volume tomography (DVT, NewTom, NewTom AG, Marburg, Germany) is a novel technique for maxillofacial imaging at a lower radiation dose and lower cost than CT. We describe four clinical cases to illustrate its potential advantages.

Clinical indications for digital volume tomography in oral and maxillofacial surgery

Digital volume tomography (DVT, NewTom, NewTom AG, Marburg, Germany) is a novel technique for maxillofacial imaging at a lower radiation dose and lower cost than CT. We describe four clinical cases to illustrate its potential advantages.

[Orbital floor reconstruction. Comparison of a new perforated 0.15 mm thick PDS layer with established titanium dynamic mesh]

INTRODUCTION

For surgical reconstruction of the orbital floor after blow-out fractures, a new perforated PDS (poly-p-dioxanon) foil (0.15 mm thickness) has recently become available. The main target of this prospective and randomized interdisciplinary clinical study was to compare this new PDS foil with the proven titanium dynamic mesh (0.3 mm thickness).

PATIENTS/METHODS

Aside from the common diagnostic procedures, an extensive ophthalmologic examination was performed and documented preoperatively (U1), 4 days (U3), 1 month (U4), and 6 months (U5) postoperatively.

RESULTS

In both groups the surgical procedure was tolerated well. The new perforated PDS foil turned out to be easier to handle intraoperatively because of smooth and clean cutting edges. The surgical treatment was well tolerated in all randomized groups. In contrast to the control group, the PDS and TD groups showed postoperatively a slight increase of the preoperative exophthalmos (mean 0.5 mm).

CONCLUSION

The new perforated PDS foil is comparable concerning cosmetic and functional aspects. Especially with regard to stability after blow-out fractures, the new perforated PDS foil is equal to titanium dynamic mesh up to 20 mm in diameter. PDS foil is felt to be superior regarding bioresorption and due to the more convenient handling.

Prototype of a novel autonomous perfusion chamber for long-term culturing and in situ investigation of various cell types

In the context of a neurobionic approach to chemical analysis and sensorics, this article depicts the development of a miniaturized autonomous perfusion chamber setup for the growth and the electrical as well as optical investigation of (neural) cell cultures in vitro. We suggest an autonomous, modular, temperature-controlled, transparent, and sealed perfusion cell culture housing adaptable to various mounts, sizes and different needs. The design includes the electronics of a temperature and medium supply control unit. The setup combines the possibility of uninterrupted cell culturing with simultaneous microscopic and analytical investigation of variable amounts of cells or organs of human, animal, or plant origin under sterile conditions on different substrates without the need of an external incubator or a sterile working environment. Its use is demonstrated exemplarily with neuronal cultures from embryonic chicken that were cultured in a prototype system for 3 weeks. It turned out that cell survival in such a chamber was prolonged with timed medium flow rather than continuous perfusion.

Effectiveness of a new perforated 0.15 mm poly-p-dioxanon-foil versus titanium-dynamic mesh in reconstruction of the orbital floor

INTRODUCTION

In recent years a new perforated PDS (poly-p-dioxanon) foil (0.15 mm) has become available and has not yet been proven to be successful in reconstruction of the orbital floor after blow-out-fractures in randomized studies. The main aim of this clinical trial is to compare this new PDS foil with titanium dynamic mesh (0.3 mm) (TD), which is well established in reconstruction of the orbital floor.

PATIENTS AND METHODS

In a prospective multicentre randomized trial, conducted between 1997 and 1998, out of 42 patients with fractures of the orbital floor, 28 patients needing material for reconstruction were randomized to receive either PDS foil or TD. In a comprehensive preoperative and postoperative protocol patients were monitored by the surgeon, radiologist and ophthalmologist with a postoperative follow-up of least 6 months.

RESULTS

Maximum defects of the orbital floor were comparable in both groups (PDS group: 13.3 mm, TD group: 13.9 mm). In both groups the surgical procedure was well tolerated, and functional and cosmetic results were evaluated as satisfactory by all patients. Ophthalmological evaluation, performed up to 6 months postoperatively, revealed double vision or vertical strabismus in nine patients (five PDS group, four titanium group). This was not confirmed subjectively in each single patient. Also ex- or enophthalmos, registered in seven patients of the PDS and four of the TD group (mainly + /- 1 mm) were not considered as relevant by the patients.

CONCLUSION

The new 0.15 mm perforated PDS foil was comparable to 0.3 mm titanium mesh concerning functional and cosmetic outcome. Obviously, persisting ophthalmometric disorders were compensated very well in both groups. PDS foil is felt to be the preferred material since it is bioresorbable and more convenient to handle.

[Video-endoscopy of the major salivary glands]

Videoendoscopy is a minimally invasive procedure for the diagnosis and therapy of sialopathies of the major salivary glands. The main indication is sialolithiasis of the submandibular and parotid glands. Sialoendoscopy offers, on the one hand, a diagnostic method for radiolucent calculi in particular and, on the other, can be used to simultaneously remove calculi. Furthermore, endoscopy is of high value for the diagnosis and treatment of other salivary gland diseases in which there are pathological changes of the ductal system. For example, regeneration of the gland is now possible in cases of chronic sialadenitis, due to the removal of a sialostenosis. Sialadenectomy can thereby be avoided.

[Odontogenic focus as the etiology of cerebral ischemia]

Recent studies have shown that acute infections, especially of the respiratory tract, are an important risk factor for cerebral ischemia. Additionally we know that chronic dental infections may be a risk for myocardial infarction and artherosclerosis. However, the connection between stroke and dental infections has hardly been examined so far. Therefore we performed a case-control study using a standardized questionaire and examination. We investigated 66 patients consecutive to a acute cerebral ischemia/stroke and 60 age- and sex-matched nonstroke neurological patients as a control group. Dental status was determined by a so called total dental index (TDI) which reflects primarily caries, periodontitis, periapical lesions, devital and missing teeth as well as by a panoramic index (PI). Specifically, older patients with cerebrovascular ischemia tended to have a significantly worse dental status and had more severe periodontitis and periapical lesions than control subjects. A predefined poor dental status was associated with cerebrovascular ischemia independent from other vascular risk factors and social status. In conclusion, poor dental health, mainly resulting from chronic dental infections, may be associated with an increased risk for cerebrovascular ischemia. The results must now be verified in larger studies. As chronic dental infections are a common and also easily treatable factor, their identification as a risk factor for stroke would be quite important in the field of preventive medicine.

[Multi-local angiosarcoma of the oral mucosa]

A 64-year-old man presented with a bluish, livid swelling in the region of the lateral alveolar processes of all four quadrants. Evaluation and histopathological findings resulted in the diagnosis of an angiosarcoma at multiple sites. A survey of the literature and an epidemiologic review of our own patients prove this to be an extremely rare occurrence. A partial resection of the maxilla and the mandible on both sides was performed in sano. After discharge, however, a sarcoma was detected in the region of the right scapula 5 months after surgery. Therefore radiation treatment was initiated. The patient died 4 weeks later. The course confirms the poor prognosis of this tumor.