Isolation of measles virus polypeptides from infected brain tissue by affinity chromatography

Mass spectrometry-based investigation of measles and mumps virus proteome

Background

Measles (MEV) and mumps virus (MUV) are enveloped, non-segmented, negative single stranded RNA viruses of the family Paramyxoviridae, and are the cause of measles and mumps, respectively, both preventable by vaccination. Aside from proteins coded by the viral genome, viruses are considered to contain host cell proteins (HCPs). The presence of extracellular vesicles (ECVs), which are often co-purified with viruses due to their similarity in size, density and composition, also contributes to HCPs detected in virus preparations, and this has often been neglected. The aim was to identify which virus-coded proteins are present in MEV and MUV virions, and to try to detect which HCPs, if any, are incorporated inside the virions or adsorbed on their outer surface, and which are more likely to be a contamination from co-purified ECVs.

Methods

MUV, MEV and ECVs were purified by ultracentrifugation, hydrophobic interaction chromatography and immunoaffinity chromatography, proteins in the samples were resolved by SDS-PAGE and subjected to identification by MALDI-TOF/TOF-MS. A comparative analysis of HCPs present in all samples was carried out.

Results

By proteomics approach, it was verified that almost all virus-coded proteins are present in MEV and MUV particles. Protein C in MEV which was until now considered to be non-structural viral protein, was found to be present inside the MeV virions. Results on the presence of HCPs in differently purified virus preparations imply that actin, annexins, cyclophilin A, moesin and integrin β1 are part of the virions.

Conclusions

All HCPs detected in the viruses are present in ECVs as well, indicating their possible function in vesicle formation, or that most of them are only present in ECVs. Only five HCPs were constantly present in purified virus preparations, regardless of the purification method used, implying they are likely the integral part of the virions. The approach described here is helpful for further investigation of HCPs in other virus preparations.

Electronic supplementary material

The online version of this article (10.1186/s12985-018-1073-9) contains supplementary material, which is available to authorized users.

Identification of mumps virus protein and lipid composition by mass spectrometry

Background

Mumps virus is a negative-sense, single stranded RNA virus consisting of a ribonucleocapsid core enveloped by a lipid membrane derived from host cell, which causes mumps disease preventable by vaccination. Since virus lipid envelope and glycosylation pattern are not encoded by the virus but dependent on the host cell at least to some extent, the aim of this work was to analyse L-Zagreb (L-Zg) mumps virus lipids and proteins derived from two cell types; Vero and chicken embryo fibroblasts (CEF). Jeryl Lynn 5 (JL5) mumps strain lipids were also analysed.

Methods

Virus lipids were isolated by organic phase extraction and subjected to 2D-high performance thin layer chromatography followed by lipid extraction and identification by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Virus samples were also subjected to gel electrophoresis under denaturating conditions and protein bands were excised, in-gel trypsinized and identified by MS as well as tandem MS.

Results

Results showed that lipids of both mumps virus strains derived from Vero cells contained complex glycolipids with up to five monosaccharide units whereas the lipid pattern of mumps virus derived from CEF was less complex. Mumps virus was found to contain expected structural proteins with exception of fusion (F) protein which was not detected but on the other hand, V protein was detected. Most interesting finding related to the mumps proteins is the detection of several forms of nucleoprotein (NP), some of which appear to be C-terminally truncated.

Conclusions

Differences found in lipid and protein content of mumps virus demonstrated the importance of detailed biochemical characterization of mumps virus and the methodology described here could provide a means for a more comprehensive quality control in vaccine production.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0463-0) contains supplementary material, which is available to authorized users.

Eye pathology associated with measles encephalitis in hamsters

Measles encephalitis was produced in 41 hamsters by intracerebral injection of the hamster-neuroadapted Mantooth HBS viral strain. Group I (n = 10) included 2-day old (newborn) hamsters, each inoculated with 0.02 ml of 1:20 diluted virus. This group was sacrificed 4 days postinoculation (DPI). Group II (n = 31) included 25-day old hamsters, each inoculated with 0.03 ml of 1:10 diluted virus. This group was sacrificed 6, 13, 17, and 31 DPI. Clinical and histological evidence of measles encephalitis was present in all infected hamsters. Retinal lesions varied with the age of the animals at the time of inoculation. Retinal folds were observed in the 2-day old group and represented one form of retinal dysplasia. In the 25-day old group, however, earliest retinal involvement was in the form of hemorrhages, followed by focal retinitis in animals sacrificed 6-17 DPI. Measles keratitis was noted only in animals sacrificed 6 DPI. In 25-day old hamsters, measles keratitis and retinal hemorrhages represented the acute manifestations, whereas retinitis occurred later. However, ocular involvement did not correlate with the degree of severity of measles encephalitis.

Host age and cell type influence measles virus protein expression in the central nervous system

Measles virus infection of the central nervous system (CNS) of children can result in a slow, progressive fatal disease, subacute sclerosing panencephalitis (SSPE). The pathogenesis of persistent measles virus infection of the CNS has been studied by comparing viral protein expression in suckling or weanling hamsters infected with the HBS strain of measles virus. Suckling animals develop a rapidly progressive fatal encephalitis while weanling animals survive and are persistently infected. Viral nucleocapsid (NP) and hemagglutinin (H) proteins have been examined during acute infection in suckling and weanling animals. Viral H protein expression is selectively inhibited in infected neurons of weanling animals, while infected ependymal cells retain the capability to express H protein at the cell surface; suckling animals express high levels of both proteins. Anti-measles antibodies are not responsible for the inhibition of H protein since immunosuppression does not restore protein expression. The cell-associated virus which is recovered late in infection by co-cultivation with Vero cells expresses all viral proteins. These results suggest that intact viral genome is present in persistent infections, and cell type or state of differentiation of infected cells may be instrumental in expression of viral proteins which can influence lytic or persistent outcome of infection.