Micromorphological aspects of the development of rubella virus in BHK-21 cells

Molecular biology of rubella virus

This chapter summarizes the present medical significance of rubella virus. Rubella virus infection is systemic in nature and the accompanying symptoms are generally benign, the most pronounced being a mild rash of short duration. The most common complication of rubella virus infection is transient joint involvement such as polyarthralgia and arthritis. The primary health impact of rubella virus is that it is a teratogenic agent. The vaccination strategy is aimed at elimination of rubella and includes both universal vaccination of infants at 15 months of age with the trivalent measles, mumps, rubella (MMR) vaccine and specific targeting with the rubella vaccine of seronegative women planning pregnancy and seronegative adults who could come in contact with women of childbearing age, although it is recommended that any individual over the age of 12 months without evidence of natural infection or vaccination be vaccinated. Medically, the current challenge posed by rubella virus is to achieve complete vaccination coverage to prevent resurgences.

Structural gene products and morphogenesis of a hybrid between rubella virus and a hamster latent retrovirus

We studied the structural gene products and morphogenesis of the hybrid between rubella virus (RV) and a latent retrovirus (R-type virus or R virus) of a baby hamster kidney cell line, BHK21/WI-2. In electron microscopic analysis, the rubella virion measures 80 nm in diameter and has a round nucleoid form with an electron-lucid centre, while R-type virus is 110 nm in diameter and has a round nucleoid with radial spokes. The type 2 hybrid (H2) virion is pleomorphic, ranging from 85 to 110 nm in diameter, and has a nucleoid structure similar to R virus, with short spokes. Indirect immunofluorescence staining of H2-infected cells with polyclonal and monoclonal antibodies (mAb) against the RV structural proteins demonstrated expression of the homologous RV gene products. SDS-PAGE of 35S-methionine-labelled proteins in RV- and H2-infected cells revealed that they both produce four major immunoprecipitable proteins, three of which (E2a, E2b and C) are products of the two genetic homologous loci (e2 and c). In nonhomologous regions, RV-infected cells exhibited E1 protein, while H2-infected cells produced the Env protein of R virus. Western immunoblotting analysis of RV and H2 viral proteins with mAb confirmed that H2 virions carry rubella viral E2 and C proteins and that E1 protein is carried by RV but not H2 virion. These results explained the absence of serological cross-neutralization of haemagglutination and plaque-forming ability of RV and H2 viruses.

Rubella-associated arthritis: rescue of rubella virus from peripheral blood lymphocytes two years postvaccination

Rubella virus was isolated from the peripheral lymphocytes of a patient with rubella-associated arthritis 2 years after rubella vaccination. The rescue of the virus was carried out by stimulating the lymphocytes with mitogens for several days in cultures and then cocultivating them with RK13 cells at 35 degrees C. Rubella virus was detected by a variety of techniques, including electron microscopy, indirect immunofluorescence, polyacrylamide gel analysis of labeled viral proteins, and microfocus assay for infectious virus particles. Assessment of the immune status of the patient did not indicate any impairment of immune function associated with long-term persistence of the virus.

Comparison of fluorescent antibody induced by rubella virus in vaccinee and convalescent individuals

Specific rubella antibody detectable by indirect immunofluorescence developed in response to immunization with attenuated rubella vaccine, HPV-77, DK-12. Fluorescent antibody (FA) was found when vaccinee sera were reacted with antigens synthesized in three different acutely infected continuous cell lines: BHK-21, LLCMK-2, and RK-13. FA titers were high, and they correlated with antibody titers obtained by hemagglutination-inhibition tests. Levels of FA in vaccinated individuals were slightly lower than those found in persons recovered from natural rubella infections. Rubella FA persists a long time in convalescent individuals and appears to be maintained for at least 19 months in vaccinees.

Nucleic acid of rubella virus and its replication in hamster kidney cells

Ribonucleic acid (RNA) has been isolated from partially purified rubella virus preparations and fractionated by rate zonal centrifugation in sucrose density gradients. The bulk of the RNA sedimented as a sharp band with a sedimentation coefficient of 38S. Rubella virus RNA appears to be single-stranded on the basis of its sensitivity to the degrading action of ribonuclease. Fractionation by precipitation with 1 m NaCl, followed by chromatography on cellulose columns, and by rate zonal centrifugation in sucrose density gradients of labeled RNA isolated from actinomycin D-treated and infected baby hamster kidney cells revealed the presence of the following virus-specific types of RNA: (i) single-stranded RNA with a heterogeneous sedimentation pattern, the 38S viral RNA becoming the predominant species only after long periods of labeling late after infection; (ii) double-stranded RNA with a sedimentation coefficient of 20S; (iii) RNA apparently composed of 20S double-stranded RNA and single-stranded branches. On the basis of their properties, the last two species were tentatively identified as the replicative form and the replicative intermediate of rubella virus RNA. Rubella virus RNA was infectious.