Joseph P. Lowenthal

The effect of adding iron to mucin on the enhancement of virulence for mice of Salmonella typhi strain TY 2

Addition of iron to ‘sub-standard’ lots of 5% gastric mucin resulted in an enhancement of the virulence of typhoid strain Ty 2 suspended in the mucin preparations. Because each lot of mucin differs with respect to iron content, different concentrations of added iron are required to reduce the LD 50 value to an acceptable level. Iron compounds alone, although effectively increasing the virulence of strain Ty 2, could not be substituted completely for mucin in typhoid virulence enhancement. The results indicate that certain mucin lots, found to be ‘sub-standard’ in preliminary tests, may become acceptable with the addition of appropriate concentrations of iron.

Distribution of Mucinolytic Activity in Strains of Shigella

Summary A survey was made to determine the incidence of mucinase production among representative strains of the genus Shigella. With the culture conditions employed, 24 out of 27 strains of Sh. flexneri 2a, 1 of 4 cultures of Sh. flexneri X and 2 of 9 strains of Sh. flexneri Y demonstrated mucino-lytic activity while none of the 214 strains of other serological types of dysentery bacilli were found to be active. Immunization of rabbits with a crude enzyme preparation from a strain of Sh. flexneri 2a yielded an antiserum which neutralized its mucinolytic activity.

Eastern equine encephalomyelitis vaccine prepared in cell cultures.

Protection tests in guinea pigs indicate that vaccines prepared from virus propagated in chick embryo cell cultures are as effective as the purified whole chick embryo vaccines which are currently used for human immunization against eastern equine encephalomyelitis.

Biological assay of proteolytic enzymes capable of debriding third degree burn eschars.

Summary A semi-quantitative bioassay has been described for determining the ability of proteolytic enzymes to debride third degree burn eschars on guinea pigs. With the aid of statistical designs, body weight and site of application were established as the 2 most important experimental variables. Trypsin, a highly purified mold enzyme, and 2 proteinase preparations from C. histolyticum have been compared for their ability to debride contact burns. pHisoHex was found to inhibit the 0-22% proteinases.

Production of high titer eastern equine encephalomyelitis virus and viral antigens in chick embryo suspension cultures.

The growth of eastern equine encephalomyelitis virus in concentrated chick embryo suspension cultures was studied. It was shown that chick embryo cells in serum-free medium, infected at the time of planting, produced up to 1011.5 plaque forming units per ml of virus. This material contained hemagglutinating and complement fixing antigens with titers of 1/10240 and 1/16, respectively. Infectious virus was inactivated at 41 °C and then lyophilized without altering the antigen titers. Hemagglutinating and complement fixing antigens were stable in the liquid state for at least 10 months at 4–6°C.

Freeze-drying various attenuated strains of Pasteurella pestis.

A method is described for the preparation of freeze-dried living attenuated Pasteurella pestis organisms in a medium suitable for the development of a vaccine for human use. Viability recovery rates of 50% or greater were obtained with the attenuated strains of P. pestis when concentrates prepared from organisms harvested after 28-hr incubation were suspended in a sucrose-phosphate-glutamate solution containing 2.5% human serum albumin and freeze-dried. The freeze-dried organisms demonstrated no loss in viability after storage for 1 year at −20 °C.

Biological properties of freeze-dried attenuated Shigella vaccines.

Summary Two Shigella flexneri 2 a strains of reduced virulence were lyophilized and their biological properties determined. When tested 19 to 23 months after drying for their ability to cause intestinal inflammation or death in starved guinea pigs, to produce keratoconjunctivitis, and to invade HeLa cells, reconstituted freeze-dried material acted in a manner similar to that of freshly grown bacteria. Reconstituted freeze-dried cells, used as oral vaccines, protected monkeys against experimental challenge with virulent S. flexneri 2a. There was no correlation between the ability to produce rises in circulating antibody and the capacity to protect against illness.

Stability of a fluid cholera mucinase preparation when combined with a commercially prepared cholera vaccine.

Summary 1. A method is described for the preparation from cholera culture filtrates of a mucinase solution which retains its in vitro mucinolytic activity for periods in excess of 2 years. 2. This preparation has been combined with a commercially prepared fluid cholera vaccine without affecting the in vitro activity of the enzyme, the antigenicity of the mucinase, or the antigenicity of the vibrio somatic substances. 3. The advantages of employing such a preparation as an immunizing agent for Asiatic cholera are discussed. The technical assistance of Mr. Gerald A. Cole is trratefullv acknowledged.

Cultivation of dengue virus type 2 in candidate substrates for vaccine production.

Dengue virus type 2 from infected human serum has been adapted to DBS-FRhL-2 and WI-38 cells which are candidate substrates for virus vaccine production. Initially, the infected DBS-FRhL-2 monolayers were refed with maintenance medium and were reharvested after prolonged incubation. With WI-38 cells, virus could be recovered only if previously passaged in DBS-FRhL-2 or primary African Green monkey kidney cells. Peak titers of 10 6 per 0·2 ml were obtained with DBS-FRhL-2 cells whereas maximum titers of 10 5 per 0·2 ml were obtained with WI-38 cells. After six passages in the two cell strains there appeared to be no attenuation of the virus in terms of mouse neurovirulence.