Mumps virus matrix, fusion, and nucleocapsid proteins cooperate for efficient production of virus-like particles.

Paramyxovirus particles, like other enveloped virus particles, are formed by budding from membranes of infected cells. To define mumps virus (MuV) proteins important for this process, viral proteins were expressed either singly or in combination in mammalian cells to produce virus-like particles (VLPs). Only the MuV matrix (M) protein when expressed by itself was capable of inducing particle release, but the quantity of these M-alone particles was very small. Efficient production of mumps VLPs occurred only when the M protein was coexpressed together with other viral proteins, with maximum production achieved upon coexpression of the viral M, nucleocapsid (NP), and fusion (F) proteins together. Electron microscopy analysis confirmed that VLPs were morphologically similar to MuV virions. The two MuV glycoproteins were not equal contributors to particle formation. The F protein was a major contributor to VLP production, while the hemagglutinin-neuraminidase protein made a smaller contribution. Evidence for the involvement of class E protein machinery in VLP budding was obtained, with mumps VLP production inhibited upon expression of dominant-negative versions of the class E proteins Vps4A and Chmp4b. Disruption of the sequence 24-FPVI-27 within the MuV M protein led to poor VLP production, consistent with findings of earlier studies of a related sequence, FPIV, important for the budding of parainfluenza virus 5. Together, these results demonstrate that different MuV structural proteins cooperate together for efficient particle production and that particle budding likely involves host class E protein machinery.

A search for evidence of viral infection in pancreases of newly diagnosed patients with IDDM.

Techniques were developed to look for evidence of viral infection in formalin-fixed paraffin-embedded autopsy pancreatic tissues from patients who had died of recent-onset insulin-dependent diabetes mellitus. DNA extracted from 47 pancreases in which good DNA preservation was confirmed was analysed by a polymerase chain reaction for Epstein-Barr virus and by a nested polymerase chain reaction for cytomegalovirus. Histological sections from 29 pancreases in which there was good RNA preservation were tested for the presence of enterovirus and Epstein-Barr virus using in situ hybridization techniques. Seventy-five pancreases were analysed immunohistochemically for the presence of mumps virus. None of these viruses could be detected in any of the diabetic pancreases studied. Control studies suggested that the techniques employed were as sensitive as culture done at the time of autopsy. Pancreas was available for study in 9 infants who had died of myocarditis; enterovirus was demonstrable in islets in 5 of these cases. An acute or persisting infection in the pancreas at the time of clinical onset of insulin-dependent diabetes by any of the 4 virus included in this study seems unlikely.

[Physicochemical characteristics of a vaccinal strain of the Leningrad-3 mumps virus (L-3)]. / Fiziko-khimicheskaia kharakteristika vaktsinnogo shtamma virusa parotita Leningrada-3 (L-3).

Purified virions of the vaccine strain Leningrad-3 of mumps virus propagated in Japanese quail embryo cell cultures had a buoyant density 1.18-1.19 g/ml in sucrose gradient, contained 50 S RNA and showed variable sizes in electron microscopy as manifested by heterogeneity of the virus zone in sedimentation analysis. Purified L-3 virus contained 5 major polypeptides with molecular weights of 74,000, 68,000, 58,000, 45,000, and 39,000 daltons. Each polypeptide had an individual oligopeptide composition.

Intrinsic fluorescence of some myxo- and paramyxoviruses and of their subviral fractions.

Fluorescence spectra of Sendai and influenza A(H1N1) viruses have different emission maxima; their quantum yield is much lower than that of tobacco mosaic virus. Solubilized envelopes and nucleoproteins of Sendai, influenza and mumps virus have different half-bandwidth and relative quantum yield values of emission, according to the agent used for disruption. Thus emission (as well as excitation and absorption) spectra of Triton X-100-solubilized envelopes show a marked hypsochromic shift as compared with the envelopes obtained by Tween20-disruption. The results are correlated with the different disruption extent achieved with the two agents.

Polypeptide composition of mumps virus.

The Enders strain of mumps virus grown in ovo was purified by differential and equilibrium sucrose gradient sedimentation. Purified virus contained seven polypeptides of mol. wts 68,000, 66,000, 61,000, 54,000, 52,000, 49,000, 47,000. Nucleocapsids isolated from DOC-treated virus contained two polypeptides of mol. wts 66,000 and 61,000.