John T. Riordan

Isolation from Human Sera in Egypt of a Virus Apparently Identical to West Nile Virus.

Summary 1. Three strains of a filterable virus closely related to West Nile have been isolated from the blood of children living on the outskirts of Cairo, Egypt. 2. The 3 strains of virus appear to be immunologically identical. 3. In addition to a strong relationship and apparent identity with West Nile virus, the Egyptian virus crosses, although to a lesser degree, with both Japanese B and St. Louis encephalitis viruses. This was found by both neutralization and complement fixation tests. 4. The virus produces a marked encephalomyelitis in monkeys inoculated intracerebrally. Lesions are found throughout the spinal cord and brain including the cerebellum. 5. Chimpanzees develop a silent infection following intracutaneous infection of the virus. This is characterized by a viremia lasting 3 days followed by the appearance of both neutralizing and complement fixing antibodies. 6. The Egyptian virus was not neutralized by human gamma globulin collected in the United States, nor by 24 different hyperimmune sera, each containing antibodies to an antigenically distinct virus type. 7. Infection with this virus has been widespread in the local Egyptian population in 1950, with more than 70% of the inhabitants aged 4 years and over having both neutralizing and complement fixing antibodies.

Poliomyelitis Viruses in Tissue Culture. IV. Protein-Free Nutrient Media in Stationary and Roller Tube Cultures.

Summary Poliomyelitis virus may be propagated in test tube, plasma-clot cultures of monkey testicular tissue in the absence of protein in the fluid phase of the nutrient medium. The tubes may be held stationary with the fragments submerged under a thin layer of medium, or they may be turned in a roller drum. The medium used contained lactalbumin enzymatic hydrolysate, serum ultrafiltrate, and balanced salt solution. With such a medium, fibroblasts grow out within 4 days after the cultures are made, and are then suitable for use in virus titrations and neutralization tests in which the presence of virus is indicated by its cytopathogenic effect on the fibroblasts. Also such cultures continue to produce virus for a period of about four weeks, long after the degeneration of the fibroblasts.

Replication of Rubella Virus in a Continuous Line of African Green Monkey Kidney Cells (Vero).

Summary Rubella virus has been found to grow to high titer in a continuous line of green monkey kidney cells (Vero), with the production of CPE and plaques. Infectivity titrations can be read within 2 weeks and are somewhat higher than comparable titers measured by echovirus 11 interference in pGMK. Primary isolation rates of 56% were obtained in Vero cultures as compared to 12% with the same specimens tested in pGMK cultures. Complement fixing antigen can be produced in satisfactory titer in Vero cultures, and the system is suitable for the direct measurement of neutralizing antibody.

A NATURAL EPIDEMIC OF RUBELLA IN A CLOSED POPULATION: VIROLOGICAL AND EPIDEMIOLOGICAL OBSERVATIONS.

We have recently had the opportuni ty of fo l lo~ng the course of a rubella epidemic in a closed population, using virus isolations and serologic tests to determine the spread of infection among susceptibles. The epidemic occurred in an institution for retarded children in which the residents are housed in cottages, each with a population of approximately 30 to 40. The clinical a t tack rates in the four cottages in which the majori ty of cases occurred are shown in Table 1. The average ages of the children ranged from abont 12 to 18, and the a t tack rates for clinical rubella were 19 to 37% in the different units. Fig. 1 indicates the t ime sequence of cases in the four cottages. The pat tern in each was remarkably regular. At first, several cases occurred over a two to three day period; then, sixteen days after the first case, a second wave began. An exception was cottage 20 in which the interval was only thirteen days between the first case and the beginning of the second group of cases. Throat swabs and blood specimens were collected from all children in each cottage several days after the first case was recognized, and again approximately two to three months later, when the epidemic was over. During the interim, all the children were examined regularly, particular at tention being paid to post-auricular lymph node enlargement and rash. Specimens were collected repeatedly from all children with suspicious findings and from those who developed frank rubella. In addition to throat swabs and blood samples, a few urine specimens were obtained from children seen on the first day of rash.

Growth of high titered rubella virus in roller bottle cultures of Vero cells.

Summary Roller bottle cultures of Vero cells yield rubella virus fluids with infectivity titers in excess of 109 TCID50/ml. The cells, after having produced maximal virus yields contain large quantities of HA and CF antigen which can be extracted by pH 9.0 glycine buffer.

Differences in cellular pathogenicity of two immunologically related poliomyelitis viruses as revealed in tissue culture.

Summary The Y-SK strain of poliomyelitis virus may be titrated in roller tube cultures by observation of the degeneration of monkey testicular fibroblasts within 4 days following the addition of virus to the tissue culture. The extent of fibroblastic degeneration is inversely related to the metabolic activity of the tissue, as measured by the amount of acid production. The 2 immunologically related Y-SK and Lansing strains of poliomyelitis virus differ in the degree to which they cause fibroblastic degeneration, and alter the amount of acid production by the tissue. In contrast to the Lansing strain, the Y-SK strain produces more extensive degeneration in fibroblasts of monkey testicles and also in those of human embryonic skin-muscle.

Thermal Sensitivity of Polioviruses Isolated during Oral Vaccine Field Trial Comparison with Monkey Neurovirulence

Summary 1. Virulent and attenuated strains of the 3 types of poliovirus have been shown to have different patterns of growth at high (39°C) temperatures when tested by means of agar overlay tissue culture technic. Attenuated strains (T marker) are inhibited and have a low EOP at this temperature, while virulent strains (T+) grow equally well at 35°, 37°, and 39°C. Some strains give an intermediate (I) pattern. 2. The thermal marker T-T+ was used to screen poliovirus strains isolated during a type I oral vaccine field trial, in an effort to determine: a) whether reversion to greater virulence had occurred as a result of human passage; and b) whether strains isolated from local flies were the vaccine virus which had been orally administered; or were naturally occurring wild strains. The results indicated that virus excreted by 2 of the 3 infected children consistently had thermal markers identical with that of the vaccine virus; one child, on the other hand, excreted virus which over a period of 29 days showed a shift to the thermal marker pattern of more virulent strains. Neurovirulence for monkeys was low for all strains isolated from children. One T strain isolated from flies had an EOP at 39°C in the same range as the LSc vaccine strain, while the 14 other fly strains tested all fell between this range and that of virulent strains. It was concluded that most of the fly strains recovered in the course of the field trial probably represented naturally occurring wild strains. 3. Comparison was made between the thermal (T-T+) marker, the EOP at low and high bicarbonate concentrations (d-d+ marker), and neurovirulence as tested by intracerebral inoculation of monkeys. The thermal marker correlated better with monkey virulence than did the d-d+ marker. 4. Use of the thermal in vitro marker should be of some practical value in determining degree of spread of attenuated poliovirus strains introduced into a community, and in assessing degree of stability of vaccine strains on human passage.

Collodion-Particle Agglutinative Tests in Detection of Antigen Derived from Tubercle Bacilli.∗:

Summary 1. With a single lot of antiserum which has been artificially produced by injecting defatted tubercle bacilli into horses, a series of comparative immunological tests have been carried out. Results indicate that collodion-particle agglutination-tests are not only satisfactory for this type of immunological determination but are more delicate than precipitin-tests, particularly for the detection of antibody.

Detection of Tubercle Bacillus Polysaccharides in Infected Material from Animals and Patients.

Conclusion The polysaccharide fraction of the tubercle bacillus may be liberated in the course of infection produced by this organism, but such fractions are not readily demonstrated by the delicate immunologie methods used in these experiments. The positive results herein recorded have been obtained only in material treated by artificial agents which may have disintegrated the tubercle bacilli present.