Small size rubella virus antigens and soluble immune complexes: analysis by the platelet aggregation technique

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.

Time course of virus-specific macromolecular synthesis during rubella virus infection in Vero cells

Virus specific macromolecular synthesis was studied in Vero cells infected with plaque-purified rubella virus under one-step multiplication conditions. Under these conditions, the rate of virus production was found to increase rapidly until 24 hr postinfection after which time the rate of virus production rose more slowly, reaching a peak level at 48 hr postinfection. This peak rate of virus production was maintained through 72 hr postinfection. A majority of the cells remained alive through 96 hr postinfection, although a 20 to 30% decrease in the number of living cells occurred between 24 and 48 hr postinfection, the time period at which cytopathic effect was first observed. The virus structural proteins were first detected intracellularly at 16 hr postinfection. The rate of synthesis of these proteins was already maximal at 16 hr postinfection and remained constant through 48 hr postinfection. By immunofluorescence, cells expressing virus proteins were first observed at 12 hr postinfection. At 24 hr postinfection, 35 to 50% of the cells in the infected culture were exhibiting immunofluorescence, at 36 hr postinfection, 65 to 90% of the cells were exhibiting immunofluorescence, and at 48 hr postinfection, all of the cells were exhibiting immunofluorescence. The virus genomic and subgenomic RNA species were first detectable by 12 hr postinfection. The rate of synthesis of both of these species peaked at 26 hr postinfection. Rubella virus infection was found to have no effect on total cell RNA synthesis. However, a modest inhibition of total cell protein synthesis which reached 40% by 48 hr postinfection was observed. When Northern analysis of RNA extracted from infected cells was performed, a negative-polarity, virus-specific RNA probe hybridized only to the virus genomic and subgenomic RNA species. A positive-polarity, virus-specific RNA probe hybridized predominantly to a negative-polarity RNA of genome length indicating that both the genomic and subgenomic RNAs are synthesized from a genome-length negative-polarity template. Defective interfering (DI) RNAs were not detected in infected cells through 96 hr postinfection or in cells onto which virus released through 96 hr postinfection was passaged. Thus, the generation of DI particles by rubella virus appears to play no role in the slow, noncytopathic replication of this virus or in the ability of rubella virus-infected cells to survive for extended periods of time.

Degradation of rubella virus envelope components

Tween-ether treatment of rubella virus, which has no effect on the antigenic and electrophoretic properties of the two envelope glycoproteins, destroys infectivity and enhances haemagglutinating activity. Trypsin treatment alters the electrophoretic pattern of the envelope glycoproteins so that the VPI peak is no longer evident and the VPII peak is reduced. At the same time, both the properties of haemagglutination and infectivity are inactivated but the capacity to combine with neutralizing antibody is retained, which suggests that VPII may be responsible for inducing the production of neutralizing antibody.

Rubella-virus infection in juvenile rheumatoid arthritis

Antibody activity against mumps, measles, polio, and rubella viruses was determined in patients with juvenile rheumatoid arthritis (J.R.A.), rubella-vaccine associated arthritis, adult rheumatoid arthritis, other chronic systemic disorders (e.g., systemic lupus and dermatomyositis), and in a matched population of normal, non-rheumatoid (control) children. The antibody levels against mumps, measles, and poliovirus were similar in all patients. Rubella-antibody levels in rheumatoid arthritis and other systemic disorders were similar to those observed in controls. The mean rubella-antibody levels in rubella-vaccine arthritis were 4 times higher than in controls. The IgM and IgG rubella-antibody levels in J.R.A. were found to be 4-6 times higher when compared to titres observed in the controls. Highest antibody levels were seen in younger children with J.R.A. Detection of rubella-virus antigen was attempted by immunofluorescence in the sediment smears of synovial fluid of patients with J.R.A., adult rheumatoid arthritis, and other non-rheumatoid joint diseases. Specific staining for rubella virus antigen was observed in the synovial fluid of 33 percent of patients with J.R.A. No antigen was detected in the synovial fluid from other patients. These observations suggest a possible role of rubella-virus infection in J.R.A.

Release of rubella virus ribonucleic acid from ribonucleoprotein by polyanions

Rubella virus ribonucleoprotein was accessible to pancreatic ribonuclease, Pronase, and certain polyanions. Most of the ribonucleic acid (RNA) label was made acid-soluble by ribonuclease, whereas Pronase and the polyanions liberated 40S RNA from the ribonucleoprotein.

Structural proteins and subunits of rubella virus

Polyacrylamide gel electrophoresis of purified rubella virus revealed two distinct structural proteins VP1 and VP3, which had molecular weights of 62,500 and 35,000, respectively. In addition, a broad variable peak, designated VP2, with a molecular weight of about 47,500, was seen. Sucrose gradient analysis of virus disrupted by neutral detergents separated a labile 150S ribonucleoprotein, containing 40S ribonucleic acid and VP3, from the envelope fraction containing VP1 and VP2. VP1 and particularly VP2 were labeled with glucosamine and are thus glycoproteins. Labeling the polypeptides with different amino acids indicated that VP3, the "core" protein, is relatively rich in arginine but not in lysine. The size of the two main polypeptides, VP1 and VP3, corresponds to those of group A arboviruses.