Persistence of Sendai virus in a mouse breeder colony and possibility to re-establish the virus free colonies.

An epizootic of Sendai virus infection occurred in a mouse breeder colony with respiratory signs, mortality, retarded growth in young and prolonged gestation period in adults. Thereafter, the infection persisted in this colony without any clinical signs and with 90 to 100% antibody positivity in adults. Weanlings had maternal antibodies and no pneumonic lesions. Antibodies were hardly detected in 6-week-old mice with high incidence of red hepatization or congestion in their lungs, but mice over 8 weeks of age had antibody without the lesions. After isolating weanlings and pregnant mice with antibodies from the infected colony, the isolated weanlings and offspring from the isolated dams became negative for Sendai virus antibodies.     

A naturally occurring epizootic caused by Sendai virus in breeding and aging rodent colonies. II. Infection in the rat.

Sendai virus infected a hysterectomy derived, barrier maintained breeding colony and a conventional aging rat colony. The virus produced seroconversion in the colonies followed by a 7-month period of decreasing titers. Clinical signs were absent during the months when titers were highest, and there was no increase in mortality, but multifocal interstitial pneumonia with perivascular and peribronchial cuffing by lymphocytes and plasma cells was present in rat lungs examined histologically. Such lesions were absent before the period of seroconversion. During the months of declining titers, the interstitial and perivascular lesions decreased in frequency and severity. The peribronchial lesions did not decrease, however, and were still present in many rats 7 months after the acute infection. Attempts to isolate the virus from weanling rats were unsuccessful.     

A naturally occurring epizootic caused by Sendai virus in breeding and aging rodent colonies. I. Infection in the mouse.

An acute Sendai virus epizootic occurred simultaneously in a breeding colony, in experimental and stock animal rooms, and in a colony of aging mice. During the 2-month period that the infection was at its maximum, death rates were approximately doubled. In some strains, the preweanling death rate reached 100%. RFM and BALB/c mice were most susceptible and NZB mice least susceptible. The mortality during the period of Sendai virus infection was increased for most strains and age groups except for the oldest female RFM and NZB mice. Death rates during the epizootic were lowest in young adult mice (greater than 10 weeks of age) and highest in the very young mice (less than 10 weeks of age) and in the oldest male and the moderately aged female mice. Although a substantial number of older mice died during the epizootic, examination of the age-specific death rates indicated that the increase in deaths remained relatively constant for all ages over 10 weeks. This showed that the older mice were not more susceptible to Sendai virus infection. As a sequela of the epizootic, focal chronic pneumonia was found in 10-40% of the mice coming to necropsy even 1 year later.     

Identification of Sendai virus mRNA species.

Cell-free translation of separated Sendai virus mRNA species identified the message for polypeptide M and suggested the identity of the message for polypeptide NP.     

Sendai virus stimulates chemiluminescence in mouse spleen cells.

Sendai virus stimulates chemiluminescence within a few seconds after it is added to a suspension of mouse spleen cells. Virus rendered non infectious by irradiation with ultraviolet light induces a similar burst of chemiluminescence. Heating or pronase treatment of the virus abrogate this reaction, as does sonication of the cells before the addition of the virus. The ability of the virus to stimulate chemiluminescence is correlated with its hemagglutination, neuraminidase, cell fusion and hemolytic properties. It is suggested that Sendai virus-induced chemiluminescence is initiated by the interaction of the virus envelope spike glycoproteins with the cell membrane.     

Isolation and characterization of Sendai virus DI-RNAs.

When passaged at high multiplicity, four strains of Sendai virus all showed evidence that they contained defective interfering (DI) particles. RNA isolated from nucleocapsids of cells infected with the high multiplicity passage stocks was found to consist of only minor amounts of nondefective genome length RNA and major amounts of smaller RNAs, the DI-RNAs. These DI-RNAs were found to have unusual and variable sedimentation properties in sucrose gradients, but were found to represent unique segments of the viral genome by length measurements in the electron microscope and by hybridization. A striking feature of the DI-RNAs is their ability to form circular structures, indicating that the ends of the DI-RNA are complementary. The implications of this finding in terms of the mechanism of genome replication is discussed.     

Gene delivery systems using the Sendai virus.

Fusogenic liposome (FL) is a delivery system that can transfer encapsulated materials into living cells directly through membrane fusion. FL is a promising approach for gene therapy because it can deliver various genetic materials much more efficiently than other non-viral vectors without damaging the cell. FL-mediated gene transfer consists of two independent membrane fusion phenomena; generation of a FL by fusing a Sendai virus (SV) particle with a simple liposome encapsulating DNA, and successive fusion of the FL with cell membrane. The former requires viral F protein but no other special molecule on the liposomal membrane, whereas the latter may require the receptor (sialic acid) and unidentified assistant molecule(s) on the cell membrane. Further analysis suggests that these assistant molecule(s), not the receptor, may control the fusion and govern the cell specificity of FL-mediated delivery. This review has described a detailed analysis of these fusion phenomena and discussed possible applications of FL-mediated gene delivery to human gene therapy.     

High-titer replication of nondefective Sendai virus in MDBK cells.

Egg-grown Sendai virus was adapted to growth in a bovine kidney cell line (MDBK cells) by serial passage under defined conditions. The adapted virus contained only 50S RNA and was highly infectious for MDBK cells. Infection of these cells with a high multiplicity of adapted virus resulted in a yield of 10(8) MDBK-infectious units/ml by 18 h, accompanied by severe cytopathic changes in the host. Cell fusion did not occur. Examination of the proteins of the adapted virus revealed that despite the high infectivity of this virus for MDBK cells the virions contained considerable quantities of Fo, the precursor to the F glycoprotein that is responsible for cell fusion and high infectivity in other systems.     

Sendai virus infection of mice with protein malnutrition.

Sendai virus pneumonia was produced in BALB/c mice fed protein-deficient diets in an effort to understand the severity of viral pneumonia in infants in developing countries. Animals on the deficient diet became clinically malnourished, and some aspects of cellular immunity were altered. In protein-deprived animals, the 50% lethal dose of intranasally administered Sendai virus was over 1,000-fold lower, pulmonary virus titers were higher, the infection was prolonged, and lung infection was established at a lower inoculum than in normal animals.     

Cytotoxic T-lymphocyte reactivity with individual Sendai virus glycoproteins.

Liposomes were constituted with affinity-purified Sendai virus glycoproteins HN and F and phosphatidylcholine (PC) or phosphatidylethanolamine: phosphatidylserine (PEPS). The glycoprotein-bearing recombinant vesicles (RV) were used to modify the surface of P815 mastocytoma cells (H-2d) or EL4 lymphoma cells (H-2b). The cells treated with HN-F-PCRV, HN-PEPSRV, or F-PEPSRV were shown by surface immunofluorescence to retain antigen for at least 2 h at 37 degrees C after treatment. The modified cells were used in cytotoxicity assays with effector spleen cells from either DBA/2 (H-2d) or C57BL/6 (H-2b) immunized by inoculation of active Sendai virus. Cells modified by treatment with HN/F-PCRV showed susceptibility to cytolysis similar to that in actively infected cells. Cells modified with HN-PEPSRV or with F-PEPSRV were also susceptible. The sum of reactivities of the anti-HN component and the anti-F components was close to that seen with HN- and F-bearing targets. Syngeneic but not allogeneic target cells expressing Sendai virus glycoproteins were bound and lysed by the effector cells, which was expected if the interactions were major histocompatibility complex restricted. The activity was attributed to cytotoxic T lymphocytes, since it was depleted by treatment with anti-Thy 1.2 antibody and complement.