Thomas C. O'Brien

Foamy virus serotypes 1 and 2 in rhesus monkey tissues.

The isolation and serologic identification by cross neutralization tests showed the presence of simian foamy virus serotypes 1 and 2 in primary rhesus monkey brain, spleen, and kidney cell cultures. The frequency of isolation of foamy viruses from brain and spleen cell cultures was 86% and from kidney cell cultures it was 36%. In primary spleen cell cultures 50% of the foamy virus isolates were type 2. Of the 14 animals from which foamy virus was isolated, only 4 demonstrated serum neutralizing antibody to the homologous serotype. The cytopathology of foamy viruses in the primary cell cultures is described.

Properties of a measles virus neuropathic for rhesus monkeys

A highly hamster brain adapted strain of measles virus, capable of producing encephalitis in monkeys, inoculated into Vero cell cultures replicated in a suppressed growth cycle. No virus was released into the medium and the infected cells lacked specific virus determinants for hemadsorption. A complete replicative cycle was achieved after six subcultures of Vero cells and was accompanied by a partial drop in neurovirulence. However, hamster neuropathogenicity persisted throughout 26 Vero passages and was markedly higher than in non-brain passaged strains. High neurovirulence was associated with pronounced giant cell cytopathic effect and thermolability. On continuous passage these three properties dissociated at different rates indicating that they are independent properties of measles virus. The importance of their coincidence for the initiation of an encephalitic process in the brain of primates is stressed.

Isolation of Foamy Virus Types 1 and 2 from Primary Rhesus Monkey Brain Cultures

Summary The isolation and serologic identification by cross-neutralization tests showed the presence of both simian foamy virus types 1 and 2 in primary rhesus monkey brain cell cultures.

Concluding Remarks: The Current Status of the National Caries Program

The National Caries Program (NCP) of the National Institute of Dental Research is a special initiative, highly organized research and development effort to develop methods to eliminate caries as a major health problem by preventing the disease. Its rationale rests on the rapidly increasing knowledge about caries etiology, early successes in translating this knowledge into preventive measures, and the growing number of improved preventive measures becoming available for clinical evaluation and cost analysis. The research and development strategy of the NCP has evolved from knowledge of the trifactorial etiology of caries, namely, the complex interaction of the bacterial agents, the dietary environment, and tooth susceptibility. The core strategy of the program is to devise caries-preventive agents for use by specific population groups by modifying one or more of the three etiologic factors necessary for the occurrence of the disease. Four main strategies are used: combat the microbial agents; increase tooth resistance; modify the diet; and improve delivery and acceptance of caries-preventive agents. The NCP conducts and supports research to develop preventive measures based on promising leads for each strategy. The NCP also seeks empirically derived evidence of caries prevention, such as caries control by topical fluoride, and builds programs to evaluate and possibly develop fully tested preventive measures based on such leads. One preventive measure currently has undergone research and development to the extent that it is being evaluated for consumer and community program acceptance. This preventive approach, school-based fluoride mouth rinsing, is intended to benefit the approximately 25 million school-aged children in the United States who lack access to municipally fluoridated water. Less successful avenues of approach are progressively eliminated from the program effort. Aspects of the etiologic processes that remain incompletely defined continue to be high priority research subjects, with the expectation that improved preventive measures will become apparent. Decisions on appropriate levels of investment and priorities given different strategies and their component objectives are made by NCP staff and advisors after consideration of potential public health values of the projected preventive measures, the resources needed for completion of alternative development and testing programs, eventual cost to the user, probable public acceptance, and other factors. In consultation with advisory groupsa via state-of-the-art workshops and conferences, in addition to the official Dental Caries Program Advisory Committee, valuable scientific advice has been obtained about topical fluorides, antimicrobial agents, trace elements, immunization, dietary control of caries, etiologic aspects of caries, and caries mechanisms. The deliberations have led in certain instances to published reviews1-3 and recommendations to the NCP on future research needs. In addition to the

Vaccinia virus: Kinetics of the hemagglutination-inhibition test and preparation of hemagglutinin

The optimum temperature and time of incubation of the vaccinia hemagglutination-inhibition test were 37°C and 16 hours, respectively. A convenient method for preparing vaccinia hemagglutinating antigen consisted of infecting one-day-old primary chick embryo fibroblasts with a high multiplicity of vaccinia virus, employing a maintenance medium devoid of serum, preparing a 20-fold concentration of virus-infected cells, and finally extracting the concentrated antigen homogenate with genetron.

Effect of freezing and lyophilization on the chicken cell agglutination (CCA) activity of inactivated influenza virus vaccines.

The CCA activity of formalin-inactivated influenza vaccine prepared by the conventional Sharples and the newer ether-degraded hemagglutinin processes was reduced by freezing and subsequent storage at −20‡C and −70‡C. Lyophilization also adversely affected their CCA value. Vaccines prepared by the zonal ultra-centrifugation method were relatively unaffected by freezing and storage at freezing temperatures. Lyophilization did result in a decrease in the CCA activity of zonal vaccines. However, this was not as marked as the decreases seen with the other preparations.