Gladys E. Sather

Viruses Associated with Epidemic Hemorrhagic Fevers of the Philippines and Thailand

Epidemiologic, clinical, and etiologic studies were carried out on a newly recognized, frequently fatal, pediatric disease syndrome which occurred in urban areas infested with Aedes aegypti mosquitoes. Four types of dengue virus (two of which are new), chikungunya virus, and another virus yet to be identified were isolated from the blood of patients. Dengue viruses, types 2 and 3, were isolated from the mosquitoes. Ample serologic confirmation was obtained of concurrent hemorrhagic fever and infection with one or more of these viruses. Thus, it was discovered that viruses of previously recognized types and of closely related new types apparently have etiologic roles in a new and highly dangerous epidemic disease syndrome.

Immunity of Hamsters to West Nile and Murray Valley Viruses Following Immunization with St. Louis and Japanese B.

Summary and Conclusions An available strain of Syrian hamsters was found to be highly susceptible to WN and MVE viruses by peripheral routes of inoculation. Groups of animals of this species were then immunized with JBE and SLE viruses and subsequently challenged subcutaneously with serial dilutions of WN and MVE viruses. Complete protection against these two agents was afforded by JBE immunization, and protection of a lesser degree obtained by SLE immunization. Neutralizing antibody titers of the immunized hamsters to the 2 heterologous challenge viruses paralleled their peripheral resistance in that the JBE virus immunes had higher neutralizing antibody titers to WN and MVE viruses than did the SLE virus immunes. These findings together with previously reported data support the hypothesis that cross immunity to these viruses probably occurs in man and that there might be some practical application of this concept in the field of human immunization. Further work with animals using other virus combinations is in progress.

Protection against St. Louis encephalitis and West Nile arboviruses by previous dengue virus (types 1-4) infection.

Summary Hamsters inoculated with Den-2 virus were shown to survive peripheral challenge with large amounts of WN virus. Dengue types 1, 3, and 4 gave less complete protection than Den-2. Cynomolgus monkeys with probable naturally acquired Den-2 neutralizing antibody were shown to be protected from a persistent viremia following SLE virus inoculation. Serological tests on both hamsters and monkeys were of the expected pattern but did not lead to an understanding of the specific mechanism involved in the cross protection. These results support epidemiological observations of the absence of severe epidemics of JBE, SLE, WN, and other Group B encephalitides in areas with endemic dengue.

A longitudinal study of infection with poliomyelitis viruses in American families on a Philippine military base, during an interepidemic period.

Epidemics of poliomyelitis with exceptionally high morbidity rates have from time to time involved United States and British military personnel and dependents on foreign bases. Natives in the same general area were frequently noted not to have an increased incidence. Americans have experienced a series of such incidents in the Philippine Islands, culminating in an unusually severe outbreak with about 50 cases on a United States Air Force Base in 1952. This outbreak, like many others, occurred a t the same season of the year when epidemics occur in the United States. The Air Force requested advice regarding possible prevention of such episodes. A study to determine certain basic epidemiological facts was recommended, then undertaken. By conducting a longitudinal study, it was hoped than one fact in particular might be difinitely determined, i.e., whether a person possessing antibody to any one type of virus might be reinfected and be a virus carrier. If this did not occur, association with natives, excepting possibly very young children, could be ruled out as one of the increased hazards. This report is preliminary and covers results available to date on only one aspect of the project-the incidence and pattern of infection found during a four-months’ period, August through November 1953, in two samples of dependent families. Each sample contained approximately 100 families. These families included, in many instances, a female Filipino domestic servant. The two samples were selected to represent “old” and “new” residents. During the previous epidemic, it had been noted that a disproportionately high incidence of cases had occurred among the relatively newly arrived, so a higher level of immunity was generally assumed for the older residents. All in (houl.1 1 had been resident on this post during the 1952 epidemic, many for a longer period of time. All in Group 2 had arrived since the termination of that outbreak, and many were very recent arrivals.

Comparative Studies on Patterns of Family Infections with Polioviruses and ECHO Virus Type I on an American Military Base in the Philippines

Many excellent reports have been published on the behavior of polioviruses in family groups. These have contributed greatly to the understanding of the epidemiology of the disease. However, with rare exceptions (the outstanding one being a project of Dr. Fox,1 carried out concurrently with ours), these other studies had certain limitations common to all retrospective studies. Specimens and histories were not taken until a case of poliomyelitis had already been diagnosed in the family; thus only part of the family infection pattern might be revealed. Furthermore, little was learned of what occurred in families where only subclinical infection or undiagnosed disease occurred. The study to be reported here

EFFECT OF POLY I: C IN MICE INJECTED WITH JAPANESE B ENCEPHALITIS VIRUS *

The p rophy lac t i c e f f e c t i v e n e s s of i n t e r f e r o n inducers given t o animals p r ior t o i n f e c t i o n wi th a v i r u s is now w e l l known1. Severa l workers r epor t ed t h a t such inducers , when adminis te red s h o r t l y a f t e r i n f e c t i o n , mediated p a r t i a l p r o t e c t i o n from systemic and l e t h a l v i r a l d i seases . 2-4 These i n v e s t i g a t o r s used v i r a l , fungal , and more r e c e n t l y a s y n t h e t i c inducer of i n t e r f e r o n , the mul t i s t randed polyr ibonucleo t ide comple o n s i s t i n g of i n o s i n i c and c y t i d y l i c a c i d s (poly 1 : C ) . ‘ t g However, v i r u s e s n o t pathogenic f o r man and i n most i n s t ances introduced by an unnatura l , i n t r a p e r i t o n e a l r o u t e w e r e u t i l i z e d . This r e p o r t desc r ibes the p r o t e c t i v e e f f e c t of po ly I : C adminis tered t o 4-5 week o ld m i c e be fo re and a f t e r i n j e c t i o n w i t h an important human pathogen, Japanese B e n c e p h a l i t i s v i r u s ( J B E ) . The r o u t e of v i r u s inocu l a t i o n was subcutaneous, s imula t ing

California group arboviruses in Florida and report of a new strain, Keystone virus.

,he n a t u r a l l y occurr i n g t ransmiss ion by a mosquito b i te . Varying dosages of JBE v i r u s w e r e i n j e c t e d r e s u l t i n g i n e i t h e r f a t a l o r t r a n s i e n t i n f e c t i o n .

ECHO virus type 13. I. Isolation and characteristics.

Dr. Bond is director, Dr. Lewis is chief virologist, and Mr. Taylor is chief entomologist, Encephalitis Research Center, Florida State Board of Health, Tampa. Dr. Hammon is professor of epidemiology, and Miss Sather is a research associate, department of epidemiology and microbiology, University of Pittsburgh Graduate School of Public Health, Pitts¬ burgh, Pa. Epidemiologic studies were directed in part by Dr. Emily H. Gates, biological studies by Dr. Wil¬ liam L. Jennings, entomological identification by Karen Meadows, serologic work by Florence Y. Lewis, and statistical analyses by Ingrid Baugh-

PROBLEMS RAISED BY CERTAIN ECHO VIRUSES IN THE ATTEMPTED LABORATORY DETECTION OF POLIOMYELITIS VIRUS INFECTION

Summary 1) The originally distributed ECHO-13 prototype virus, Hamphill 2–188–20 passage 7, is a mixture of ECHO virus types 1 and 13. ECHO-1 was found in higher titer than ECHO-13 during passage and only the former was isolated at terminal dilution. It was necessary to neutralize ECHO-1 virus with antiserum to demonstrate the presence of ECHO-13 in this mixture and this apparently did not alter its antigenic properties. ECHO-13 virus was successfully reisolated in pure form from the original rectal swab eluate after 4 years storage. 2) Plaque purified strains of reisolated 2–188–20 virus and a Del Carmen 11–4–1 virus isolate were examined as possible ECHO-13 prototypes. The plaque purified 11–4–1 strain produced a broader spectrum antiserum in monkeys in early test bleedings and produced a higher infectivity titer in MKCC. It has been accepted as prototype ECHO-13 by the Committee on Enteroviruses. 3) The biologic properties of ECHO-13 virus in certain animals, chick embryos, cell culture and cell culture fluids are described. A clinically inapparent meningoencephalitis occurred in inoculated monkeys.

Gamma Globulin Passive Protection Tests in Mice Injected Intraperi-toneally with MEF1 Poliomyelitis Virus.

The Committee on the ECHO Viruses of the National Foundation for Infantile Paralysis, Inc., New York, N. Y., did not attempt to present an exact definition for the ECHO viruses, although it enumerated the properties possessed in common by the originally described 13 agents comprising this new group.’ The name ECHO viruses stands for Enteric Cytopathogenic Human Orphan viruses. The common properties listed are: “(1) they are cytopathogenic for human and monkey cells in culture; (2) they are not neutralized by pools of the three types of poliomyelitis antiserum; (3) they are not neutralized by antisera for Coxsackie viruses that are known to be cytopathogenic in tissue culture, and they fail to induce disease in infant mice; (4) they are not related to other groups of viruses recoverable from the alimentary tract (throat or intestine) by inoculation of primate tissue culture . . . ; ( 5 ) they are neutralized by human gamma globulin and by individual human serums”; and (6) it is stated that “if and when any one of the established types is identified as the etiologic agent of a clinically distinct disease, it will be removed from the ECHO group of v i r~ses .”~ This part of this monograph was planned to deal with agents expected to fall within this group. The emphasis in this first paper wiil be on the problems that these agents present when one attempts to detect or exclude poliovirus infection through laboratory methods that utilize tissue culture. These problems became most acute for us in the fall of 1953 when we began to process 33,000 frozen specimens of serum, rectal swabs, and throat swabs obtained during a 4-month study of several population samples on or near a United States Air Force base in the Republic of the Philippines. The purpose of testing these specimens was to detect, as nearly as possible, every unapparent or clinical infection with poliovirus that occurred in any person included in our population samples during this 4-month period. In general, blood sera were gathered every 4 weeks, and rectal and throat swabs were collected every 2 weeks during 9 clinic visits. Swabs were tested for virus in monolayer cultures of trypsinized monkey-kidney tissue and observed for cytopathogenic effects. When a cytopathogenic agent was obtained and could be passed serially, an attempt was made in the usual way, utilizing the 3 types of poliovirus antiserum, to determine whether it was a poliovirus. Serological