NEUTRALIZATION OF EPIDEMIC INFLUENZA VIRUS : THE LINEAR RELATIONSHIP BETWEEN THE QUANTITY OF SERUM AND THE QUANTITY OF VIRUS NEUTRALIZED

THE SYNERGISM OF HUMAN INFLUENZA AND CANINE DISTEMPER VIRUSES IN FERRETS

The infections produced in ferrets by human influenza virus and canine distemper virus were studied. Cross immunity and cross neutralization tests showed that these two viruses were not related antigenically. Ferrets infected with influenza virus alone rapidly produced considerable quantities of neutralizing antibodies, and after the 6th day virus was not demonstrable in their lungs. Ferrets infected with both influenza and distemper viruses simultaneously produced but small amounts of neutralizing antibody, and influenza virus persisted in undiminished concentration in their lungs throughout the course of the infection.

STUDIES ON INFLUENZA VIRUS : THE COMPLEMENT-FIXING ANTIGEN OF INFLUENZA A AND SWINE INFLUENZA VIRUSES

Influenza complement fixation tests designed for use with ferret serum are described. Complement-fixing antigens derived from influenza ferret lungs were unsatisfactory due to their low content of soluble antigen; those prepared from mouse lungs or developing chick embryo membranes proved to be better antigenically and were reliable when the various reagents in the test were properly adjusted to eliminate non-specific fixation of complement. The results of cross complement fixation tests indicated that the soluble antigens of the PR8 and W.S. strains of influenza A virus were closely similar, if not identical. They indicated also that the soluble antigen of swine virus possessed components present in the antigens of the human strains of virus.

NEUTRALIZATION OF INFLUENZA A VIRUS BY HUMAN SERUM

A linear relationship exists between the quantity of human serum used and the quantity of influenza A virus neutralized. By means of this relationship it is possible to determine the maximum quantity of virus which a given human serum can neutralize. This quantity, the neutralizing capacity, is a fixed value and, unlike the serum dilution end point, is independent of the amount of virus used in the neutralization test.

A LATENT VIRUS IN NORMAL MICE CAPABLE OF PRODUCING PNEUMONIA IN ITS NATURAL HOST

1. A virus capable of producing fatal pneumonia in mice has been isolated repeatedly from the lungs of certain apparently healthy mice. Not all mice carry the virus. It was obtained only from mice supplied by three breeders although mice from eight different sources were studied. 2. The virus was avirulent as it occurred in normal mouse lungs and became virulent only after serial mouse lung passage. It was strictly pneumotropic for mice and produced pneumonia when given intranasally but showed no evidence of infection when given by other routes. The virus was non-infectious for ferrets and did not become pathogenic for this species after numerous serial passages. It was also non-pathogenic for rabbits, guinea pigs, rhesus monkeys, voles, deer mice, skunks, wood-chucks, opossums, and Syrian hamsters. 3. All strains of the virus which have been tested have been immunologically identical, as indicated both by cross immunity and cross neutralization tests in mice. 4. The virus was antigenic both in mice and in rabbits and was readily differentiated from viruses of human influenza and of swine influenza by means of either cross immunity or cross neutralization tests. 5. The virus was also neutralized by about 30 per cent of normal human sera tested. 6. The virus was extremely labile, and suspensions prepared in saline or broth became inactivated within a few hours at room temperature. The addition of normal horse serum to the virus suspensions, however, exerted a definite stabilizing effect. 7. Ultrafiltration results indicated that the virus particles have a diameter of about 100 to 150 millimicrons. 8. Evidence is presented which indicates that this virus is different from other viruses which various investigators have found in normal mouse lungs.

ADJUVANTS IN IMMUNIZATION WITH INFLUENZA VIRUS VACCINES

Subcutaneous inoculation, of PR8 allantoic fluid, or watery suspensions of the virus obtained from allantoic fluid by high-speed centrifugation or by elution after adsorption on red cells induced serum antibodies in experimental animals, which reached the highest levels within 2 weeks after inoculation and were gradually lost thereafter. The addition of killed acid-fast bacteria (Myco. tuberculosis or butyricum), paraffin oil, and a proprietary adsorption base (Falba) to form a stable water-in-oil emulsion of influenza virus suspensions greatly enhanced and maintained immunity and antibody response to the virus. These adjuvants provided a much more effective method of increasing antibody production to the virus than the use of concentrated preparations of virus alone. Paraffin oil and Falba without the acid-fast bacilli were less effective as adjuvants, although the antibody levels induced were higher than those produced by watery suspensions of the virus and were maintained at a constant level for at least 6 months. Myco. butyricum appeared to be more effective in producing antibodies against the virus than the tubercle bacilli in the emulsions of paraffin oil and Falba. Immunization with these adjuvants and suspensions of influenza virus obtained from allantoic fluid induced antibodies not only against the virus but against antigenic material contained in normal allantoic fluid, although the latter titers were considerably lower. A suspension of influenza virus (sedimented by high-speed centrifugation) and Myco. butyricum in sesame oil induced about four times as much antibody as when the virus was suspended in saline, in sesame oil alone, or in combination with typhoid bacilli.

QUALITATIVE DIFFERENCES IN THE ANTIGENIC COMPOSITION OF INFLUENZA A VIRUS STRAINS

A study of the PR8, Christie, Talmey, W.S., and swine strains of influenza A virus by means of antibody absorption tests revealed the following findings: 1. Serum antibody could be specifically absorbed with allantoic fluid containing influenza virus or, more effectively, with concentrated suspensions of virus obtained from allantoic fluid by high-speed centrifugation or by the red cell adsorption and elution technique. Normal allantoic fluid, or the centrifugalized sediment therefrom, failed to absorb antibodies. Influenza B virus (Lee) caused no detectable absorption of antibody from antisera directed against influenza A virus strains, but it specifically absorbed antibody from Lee antisera. 2. The neutralizing, agglutination-inhibiting, and complement-fixing anti-bodies in ferret antisera were completely absorbed only by the homologous virus strain, even though 2 absorptions were carried out with large amounts of heterologous virus strains. 3. PR8 virus appeared to have the broadest range of specific antigenic components for it completely absorbed the heterologous antibodies in Christie and W.S. antisera and left only those antibodies which reacted with the respective homologous strains. The other virus strains (Christie, Talmey, W.S., swine) were more specific in the absorption of heterologous antibodies and completely removed only those antibodies which reacted with the absorbing virus. 4. The absorption tests revealed a higher degree of specificity and individuality of the virus strains than the various cross reactions previously reported. The strain specificity of PR8 virus was equally manifest in absorption tests with ferret sera and with human sera following vaccination. 5. The amount of homologous antibody remaining in a PR8 ferret serum after absorption with PR8 virus, obtained by the red cell adsorption and elution method, varied inversely as the concentration of virus used for absorption. A given concentration of virus, however, absorbed a greater percentage of neutralizing antibodies than either agglutination-inhibiting or complement-fixing antibodies.

TITRATION OF INFLUENZA VIRUS IN CHICK EMBRYOS

A study was made to establish the reproducibility of end points obtained in the titration of influenza viruses in chick embryos. Six tests were performed, each composed of five replicate titrations of a purified preparation of the PR8 strain of influenza virus. The data from these titrations were subjected to statistical analysis which revealed that the chances are 19 out of 20 that differences in end points of 0.37 and 0.62 logarithmic units are significant in titrations employing ten embryos and five embryos per dilution, respectively. Additional simultaneous titrations in embryos and in mice showed that chick embryos are sensitive to considerably smaller amounts of virus than are mice, and that the mouse titration is adversely affected by inactive virus under conditions which are without apparent influence on the embryo titration.

THE ENHANCING EFFECT OF CONCURRENT INFECTION WITH PNEUMOTROPIC VIRUSES ON PULMONARY TUBERCULOSIS IN MICE

The course of pulmonary tuberculosis in the mouse appears to be accelerated as a result of concurrent infection of the lung with either of two pneumotropic viruses. This effect is obtained with virus inocula sufficiently small as to induce little or no definite viral pneumonia.

A COMPLEX VACCINE AGAINST INFLUENZA A VIRUS : QUANTITATIVE ANALYSIS OF THE ANTIBODY RESPONSE PRODUCED IN MAN

A quantitative study of the antigenicity of various vaccines containing influenza A virus has been made in human beings. A complex vaccine prepared from chick embryos inoculated with both influenza A virus and the X strain of canine distemper virus was found to be more effective than other vaccines in stimulating the production of neutralizing antibodies against the former virus. The increased antibody levels which resulted from the administration of this vaccine remained almost unaltered for at least 5 months.

THE MODIFYING EFFECTS OF CERTAIN SUBSTANCES OF BACTERIAL ORIGIN ON THE COURSE OF INFECTION WITH PNEUMONIA VIRUS OF MICE (PVM)

Evidence is presented which indicates that certain polysaccharide preparations derived from various bacterial species, as well as similar materials not of bacterial origin, are capable of lessening the severity of infection with pneumonia virus of mice (PVM) and inhibiting multiplication of the virus in mouse lungs infected with this agent. It seems probable that modification with respect to the virus is mediated by a substance which may be polysaccharide in nature.

THE MOUSE INFECTIVITY TITRATION OF INFLUENZA VIRUS

A study has been made to establish the statistical significance of results obtained in mouse infectivity titrations of influenza virus. Five titrations, each composed of five replicas, were carried out and 50 per cent end points were calculated for each titration. Three criteria for evaluating the end points were employed, namely, the presence or absence of pulmonary lesions, the occurrence of death, and a weighted composite taking into account both the extent of lung consolidation and the occurrence of death. Standard deviations of the distribution of end points obtained by each method were computed, and from these data levels of probabilities for significance in the differences between end points were determined. It was found that the chances are 19 out of 20 that differences of 0.99, 0.77, and 0.73 logarithmic units, respectively, for the lesion, the death, and the weighted end points are significant.

EXPERIMENTAL INFECTION WITH INFLUENZA A VIRUS IN MICE : THE INCREASE IN INTRAPULMONARY VIRUS AFTER INOCULATION AND THE INFLUENCE OF VARIOUS FACTORS THEREON

Following intranasal inoculation of influenza A virus (strain PR8) there is a rapid increase of the virus in the lungs which with large doses reaches a maximum within 24 hours. With smaller doses, although the proportional increase is greater, the maximum concentration is not reached until 48 hours following inoculation. If a lethal dose is administered, the ultimate concentration of the virus in the lungs is the same, irrespective of the size of the dose. If a sublethal dose is given, the titer of the virus in the lungs does not achieve the titer reached in mice receiving a lethal dose. Within 48 hours following inoculation of a sublethal dose the lungs of a mouse may contain at least 76,000 M.L.D., yet the mouse survives. The intranasal instillation of sterile fluid (distilled water, varying concentrations of NaCl, broth, or 10 per cent normal serum) into a mouse sublethally infected produces a sharp rise in the virus content of the lung usually followed by death within 3 to 8 days. If, however, the instillate consists of 10 per cent immune serum, there is no rise in the virus titer, and no apparent harm results from the instillation. The implications of these phenomena are discussed and an hypothesis presented to explain their occurrence.

THE QUANTITATIVE DETERMINATION OF INFLUENZA VIRUS AND ANTIBODIES BY MEANS OF RED CELL AGGLUTINATION

1. The agglutination titer for chicken red cells of freshly prepared or carefully stored suspensions of PR8 influenza virus, that is to say virus of maximum pathogenicity, was found to be proportional to the mouse lethal titer of the same preparations. 2. The agglutination titer of infected allantoic fluid procured in a standard way is relatively constant, regardless of the influenza strain used and its pathogenicity for mice. 3. Virus preparations inactivated by heat or storage may retain their agglutinating power. 4. Certain animal sera contain a partially heat-labile factor which, in low dilution, inhibits the agglutination of chicken red cells by influenza A and influenza B viruses. 5. The agglutination inhibition test, using ferret and human sera, gives qualitative data regarding influenza antibodies which are similar to the information obtained on the same sera by means of the virus neutralization test. 6. There is a definite relationship between the agglutination inhibition titer and the virus neutralization titer of a serum. On a logarithmic scale of both variables, this relationship is essentially linear within the range investigated. 7. The agglutination inhibition titer of immune ferret serum is inversely proportional to the amount of virus used in the test.

ENCEPHALOMYELITIS OF MICE : II. A METHOD FOR THE MEASUREMENT OF VIRUS ACTIVITY

In a study of mouse encephalomyelitis the following observations were made:— 1. A definite relationship exists between the amount of virus inoculated intracerebrally and the length of the incubation period. 2. The reciprocal of the incubation period was found to be approximately proportionate to the logarithm of the amount of virus inoculated. The relationship can, therefore, be given a simple mathematical form. 3. This fact provides a basis for a new method for measurement of the activity of mouse encephalomyelitis virus.

The production of a persistent alteration in influenza virus by lanthanum or ultraviolet irradiation

The rates of elution from RBC of the Lee and PR8 strains of influenza virus were studied by means of a step-wise elution technique. By means of a single treatment with lanthanum acetate or irradiation with ultraviolet and subsequent passage in chick embryos, it was possible to alter the elution rate of the Lee strain so that it was similar to that of the PR8 strain. This alteration proved to be persistent on serial passage in the absence of the agent which caused it. As far as was determined, the elution rate of the virus appeared to be the only property which was altered. The phenomenon can be most readily understood on the assumption that the difference in elution rates of the two strains is due to a heterogeneous population of virus particles in the Lee strain with respect to elution rate.

The effect of diet on the susceptibility of the mouse to pneumonia virus of mice; influence of pyridoxine in the period after the inoculation of virus

Young mice fed diets deficient in pyridoxine or fed desoxypyridoxine after the inoculation of the pneumonia virus of mice were more resistant to infection than well nourished controls. The susceptibility of young mice to PVM increased with the duration of pyridoxine administration after inoculation. Dietary protein restriction when pyridoxine was provided did not affect the susceptibility of mice to PVM. The PVM-combining capacity of mouse lung and the titer of humoral antibody against PVM were the same in mice fed a complete or pyridoxine-deficient diet for 6 days. The amount of PVM in mouse lungs 6 days after inoculation was greater by both infectivity and hemagglutination titrations in mice fed pyridoxine than in pyridoxine-deficient controls. This suggests that pyridoxine was essential during the postinoculation period for optimal virus multiplication.

Concurrent infection with influenza virus and mumps virus or pneumonia virus of mice as bearing on the inhibition of virus multiplication by bacterial polysaccharides

Preexisting infection with PVM or mumps virus does not prevent multiplication of the virus of influenza A or B in the same tissue. Similarly, pre-existing infection with one or another of the influenza viruses does not prevent multiplication of either PVM or mumps virus in the same tissue. The failure of these two groups of viruses to interfere with the multiplication of each other is discussed in relation to the mechanism of inhibition of multiplication of mumps virus and PVM by the capsular polysaccharides of Friedländer bacilli, and the ability of influenza A and influenza B viruses to multiply in the presence of large quantities of these carbohydrates. It is suggested that differences in the requirements of the two groups of viruses for host cell metabolic systems may serve to explain both the lack of interference between them and the differing effect of polysaccharides upon their multiplication.

Lack of identity in neutralizing and hemagglutination-inhibiting antibodies against influenza viruses

There is an exponential linear relationship between the quantity of influenza virus neutralized and the quantity of immune serum employed in in ovo neutralization. The slope of the neutralization line is extremely steep. The concentration of neutralizing antibody can be measured with considerable precision in ovo if the constant virus-varying serum technique is utilized. The amounts of hemagglutination-inhibiting and neutralizing antibodies which are absorbed by a given quantity of influenza virus (PR8) were found to be predictable and the degree of reactivity of these two antibodies was shown to be directly related to the extent of immunization. It was demonstrated that there are marked discrepancies in correlation between antibody titers obtained by in vitro hemagglutination-inhibition and in vivo neutralization techniques and that neutralizing antibody is preferentially absorbed by a given quantity of virus. Inasmuch as the results were found not to be attributable to peculiarities of the techniques employed, it appears that the antibodies measured by hemagglutination-inhibition in vitro and by neutralization in vivo are not identical.

Mechanism of production of pulmonary lesions in mice by Newcastle disease virus (NDV)

Infectious NDV particles produce extensive pulmonary consolidation in the mouse in the absence of demonstrable virus multiplication. The lesions are indistinguishable from those of influenza A virus infection. This effect of NDV was blocked by intranasal injection of RDE or immune serum before virus inoculation, but not by immune serum injected 5 minutes or more after NDV. Influenza A virus infection did not diminish fixation of NDV in excised lungs but did interfere with the injurious action of this agent in the living mouse. The analogy between these reactions and those which take place in a progressive virus infection is pointed out, and the mechanism of production of lesions in virus pneumonias discussed.

Immunological reactions of the Coxsackie viruses. I. The neutralization test; technic and application

The neutralization test is a reliable and useful procedure for following immunological reactions of the Coxsackie viruses (C virus). The standard procedure has been an incubation period of 1 hour at room temperature followed by subcutaneous inoculation into newborn mice. However, this time and temperature are not critical, for the virus in neutralized within 10 minutes of mixing with immune serum and remains neutralized for long periods. During the variable incubation periods used, the control virus remained active, even in dilute suspensions. The neutralization test is not affected by the presence or absence of complement. Neutralizing antibody is stable at 65°C. for 30 minutes, and immune serum has to be heated to 80°C. for 30 minutes before the antibody is no longer detectable. As the quantity of virus is increased, the quantity of serum required for neutralization likewise increases, but not in a regular or predictable fashion. Neutralized mixtures of the virus can be made infective again by simple dilution before inoculation. The neutralization test is a satisfactory means for typing Coxsackie viruses. At least seven antigenic types have been identified. Similar antigenic types have been found to be scattered over wide areas. Thus the Conn.-5 type was present in 1948 in Massachusetts, Connecticut, New York, and North Carolina. The Texas-1 type was present in 1943 in Connecticut and in 1948 in North Carolina and Texas. Further information on the specificity of the neutralizing antibody response has been obtained from a study of the occurrence and development of antibodies in 6 patients who contracted infections with one or another of the C viruses while working with them in the laboratory. From each patient a virus was isolated during the illness. No patient had detectable antibodies to his strain before his illness, but each soon thereafter developed antibodies to his own strain and to the prototype strain to which it was related. By means of the neutralization test, it has been shown that a family epidemic may include two different immunological types of virus. Neutralizing antibodies appear at the time of or soon after onset of illness, increase rapidly to titers of about 1:1000 which are maintained during the period of 1 to 3 months following infection, and are still present 2 years later, although at lower levels. Neutralizing antibodies are present in the normal population. In North Carolina, over 80 per cent of the children have antibodies at birth. The level falls rapidly to a minimum of 14 per cent at the age of 1, and then it quickly rises to reach the adult level at the age of 7. Gamma globulin collected in various parts of the United States between 1944 and 1949 and in Denmark in 1949 neutralizes at least four antigenically different Coxsackie viruses.

A new member of the psittacosis-lymphogranuloma group of viruses that causes infection in calves

From portions of intestine and feces of apparently normal calves, a virus that produces elementary bodies was procured in guinea pigs and in embryonated eggs. Morphologically and tinctorially this virus closely resembled members of the psittacosis-lymphogranuloma group of viruses and it shared a common antigen or antigens with them. Comparison of serological, pathogenic, and other properties indicated that this virus from calves is a new member of the psittacosis-lymphogranuloma group and in keeping with classification practices it is provisionally named Miyagawanella bovis. Miyagawanella bovis when fed to experimental calves established an infection in the intestinal tract that resembled the inapparent infection seen in natural cases but failed to produce evident disease. Ability of the virus to infect experimental animals by feeding, and its presence in feces of infected animals indicate its natural mode of spread. This method of dissemination and persistence of virus for long periods of time in infected animals suggested the virus should be widespread and more than 60 per cent of the calves in the vicinity of lthaca were found to be infected.

Quantitative aspects of the multiplication of influenza A virus in the mouse lung; relation between the degree of viral multiplication and the extent of pneumonia

Influenza A virus, PR8 strain, increases in amount in the infected mouse lung at a relatively constant rate. When more than 25 M.S.50 doses of virus is inoculated, the rate of multiplication appears to be independent of the amount of virus introduced; has a value of 1,100-fold increase per day. The rate of increase in the pulmonary lesions induced by infection of the mouse lung with PR8 also appears to be relatively constant and independent of the amount of virus inoculated; has a value of 8.5-fold increase per day. The essential variables in the PR8-mouse lung system appear to be equated satisfactorily by functions which were derived previously (4) during a similar quantitative investigation on pneumonia virus of mice (PVM). Evidence in support of the hypothesis that the processes of multiplication of PR8 and PVM are different in the mouse lung is presented.

The dependence of the pathological lesion upon the multiplication of pneumonia virus of mice (PVM); kinetic relation between the degree of viral multiplication and the extent of pneumonia

The rate of multiplication of PVM in the mouse lung is relatively constant, averaging 7.9-fold per day with but slight variations, irrespective of the amount of virus inoculated. Similarly, the rate of increase in the amount of pneumonia is relatively constant, averaging 4.7-fold per day, even though the quantity of virus inoculated is varied over a wide range. It follows that viral multiplication proceeds 1.7 times more rapidly than does extension of the pathological lesion, both reaching limiting maximal values in periods which are predictable from the amount of virus inoculated. From the concentration of virus determined at any time during the incremental period, the amount of pneumonia present earlier or later in the incremental period can be computed with considerable precision. The results support the postulate that the extent of the pathological lesion is dependent upon the degree of viral multiplication.

Genetic studies of influenza viruses. I. Viral morphology and growth capacity as exchangeable genetic traits. Rapid in ovo adaptation of early passage Asian strain isolates by combination with PR8

The passage of newly isolated, filamentous Asian (A2) influenza viruses in the presence of non-infective PR8 (A) virus results in the rapid emergence of virus of Asian (A2) antigenicity but PRS-like growth capacity and spherical morphology. Evidence is presented that this effect results from genetic interaction of the infective Asian and non-infective PR8 viruses rather than from spontaneous change of the Asian strain. It is concluded that influenza viral morphology, growth rate and growth capacity are associated genetic traits which distinguish unadapted from adapted strains, and which are transferable by recombination. A pragmatic consequence of these experiments is the fact that conditions have been defined for the rapid adaptation of early passage influenza virus isolates to the chick embryo allantoic sac. Such adaptation is attended by an increase in viral yield which has obvious implications for vaccine production during future epidemics with new antigenic types.

INDUCTION OF PARTIAL SPECIFIC HETEROTYPIC IMMUNITY IN MICE BY A SINGLE INFECTION WITH INFLUENZA A VIRUS

Schulman, Jerome L. (Cornell University Medical College, New York, N.Y.), and Edwin D. Kilbourne. Induction of partial specific heterotypic immunity in mice by a single infection with influenza A virus. J. Bacteriol. 89:170-174. 1965.-Mice infected 4 weeks previously with influenza A virus were found to be partially immune when challenged with influenza A2 virus. This partial immunity was demonstrated by reduced titers of pulmonary virus, decreased mortality, and less extensive lung lesions. A specific immunological basis for this protection was suggested by the absence of any protection in animals previously infected with influenza B virus when challenged with A2 virus, or in animals previously infected with influenza A virus when challenged with influenza B virus. Parenteral inoculation with inactivated influenza A virus did not induce partial immunity to A2 virus challenge. An accelerated rise of hemagglutinating-inhibiting antibody after A2 virus challenge was demonstrated in animals previously infected with influenza A virus.

Histopathological changes in the upper respiratory tract of F344 rats following infection with a rat-adapted influenza virus

The present study determined the morphogenesis of upper respiratory tract disease in rats following infection with a rat-adapted influenza virus. Sixty-eight 60-day-old, male F344 rats were infected by intranasal inoculation and necropsied at days 1, 2, 4, 7, 14, and 28 post-inoculation (PI). Responses to infection were studied by routine light microscopy for histopathologic changes and immunocytochemistry for localization of viral antigen. Severe infection-induced changes involved the respiratory epithelium and underlying lamina propria, and the nasal-associated lymphoid tissue, with minimal involvement of the transitional epithelium. The lesions were most severe on the septum and the medial aspect of the nasoturbinates. Viral antigen, located in the respiratory epithelium of affected regions at days 1 and 2 PI, was associated with neutrophilic infiltration and epithelial necrosis and erosion. At day 4 PI, an infiltrate of lymphocytes, macrophages, and fewer neutrophils was present, often accompanied by epithelial regeneration. Changes in the nasal-associated lymphoid tissue were evaluated using morphometric analysis and consisted of hyperplasia (days 4 to 7 PI) followed by progressive involution (days 14 to 28 PI). Mild lesions associated with foci of viral antigen were also observed in the nasal olfactory epithelium on days 1, 2, and 4 PI. The changes observed in the present study indicate the potential value of rat-adapted influenza virus infection as a model of human influenza.

Activity of FCE 20696, a new synthetic immunomodulator, in models of viral and bacterial pathology

The dibenzopyran derivative FCE 20696 is an immunomodulator which protects mice infected with several viral agents and with Mycobacterium tuberculosis. The compound is able to decrease the severity of the lung lesions caused by influenza virus infection. Doses ranging from 12.5 to 100 mg/kg are effective even after a single administration. Activity is demonstrated by intraperitoneal, subcutaneous and oral administration of the drug. In systemic infection with herpes simplex virus type 1, the 100 mg/kg dosage, administered subcutaneously, is able to increase both the percentage and the mean survival time of mice. To have effect by oral administration it is necessary to give the compound twice in the day. Moreover, some activity has also been observed in mice infected by M. tuberculosis, when the compound is administered orally at doses of 1-2.5 mg/kg twice weekly for 5 weeks, during the course of the disease.

The effect of diethylstilbestrol as measured by host resistance and tumor susceptibility assays in mice

As part of a program to develop and validate methodology to measure chemically induced immunotoxicity, the effect of DES on resistance of adult B6C3F1 female mice to various microorganisms and to challenge with syngeneic tumor cells was evaluated. The mice received sc injections of 50 microliter corn oil alone or of corn oil containing the equivalent of 0.2, 1, and 4 mg DES/kg X d for 14 d. Three days later they were challenged with Listeria monocytogenes, Streptococcus sp. influenza virus, herpes virus, Trichinella spiralis, or B16-F10 tumor cells. Host resistance parameters were mortality for the bacterial and viral systems, expulsion of adult parasites from the gut for T. spiralis, and lung weights for the B16-F10 tumor-cell model. Host resistance to L. monocytogenes, herpes virus, and T. spiralis was significantly decreased following DES exposure. Resistance to Streptococcus sp. was decreased, but not at a statistically significant level following these doses of DES. However a dose of DES at 8 mg/kg X d resulted in a highly significant decrease in resistance to the organism. Resistance to influenza virus was unaffected by the DES. In contrast to the above, host resistance to iv-administered B16-F10 tumor cells was significantly increased as a consequence of DES exposure. These model systems for measuring alterations in host resistance have been indicated to hold potential for the routine screening of drugs, chemicals, and environmental agents for their possible immune effects, both adverse and potentiating. The results indicate the importance of selecting the appropriate assay for evaluating a particular agent. They also stress the necessity for including host resistance assays along with assays to measure specific immune aspects, in order to assess in the intact animal the overall effect of complex immune interactions following exposure to a test agent.

Dose-response relationships in a microneutralization test for foot-and-mouth disease viruses

Two-dimensional quantal microneutralization tests on foot-and-mouth disease viruses, in which neutralizing antibody activity was titrated against a serial range of virus doses, demonstrated a variety of dose-response curves some of which were rectilinear, others clearly curvilinear. Moreover, in the case of the non-linear responses obtained with some antisera, the shape of the curve was such that antibody titres recorded with doses of virus ranging from 10(3)-10(5) TCD50 were closely similar. Studies were carried out on the effect of varying the conditions of the test on the shape of the dose-response curve: significant differences were obtained after treatment of the antiserum-virus mixtures with anti-species globulin, and when the test was assayed in cells of differing susceptibility to infection.

Use of recombination in the production of influenza vaccine strains

Recombination between influenza A viruses as a method of producing strains suitable for use in vaccines is discussed with particular reference to a recombination system involving an attentuated laboratory strain A/PR8/34 (HoN1) and a recent isolate of the epidemic strain A/Hong Kong/68 (H3N2). A variety of properties of the viruses were shown to be segregated independently of one another during recombination. These properties included the envelope antigens (haemagglutinin and neuraminidase), growth capacity in the fertile egg and attenuation for man. Some of the recombinants were considered suitable for use in vaccines either inactivated (whole virus particles or subunits) or live. The application of this technique to future requirements for vaccine strains are discussed with particular reference to the safety aspect of using recombinants in live vaccines.

Studies on pneumonia virus of mice (PVM) in cell culture. I. Replication in baby hamster kidney cells and properties of the virus

Pneumonia virus of mice (PVM) has been serially propagated in a line of baby hamster kidney (BHK21) cells. A maximum titer of 6.3 x 10(6) TCID(50) per ml was obtained, and there was little variation in yield on serial passage. PVM grown in BHK21 cells was antigenically similar to virus obtained from the mouse lung, but was somewhat less virulent for the mouse after 10 serial passages in these cells. Virus produced by BHK21 cells agglutinated mouse erythrocytes without prior heating or other treatment. Sedimentation of PVM in the ultracentrifuge or precipitation by ammonium sulfate resulted in a loss in infectivity but an increase in hemagglutinating activity, presumably due to disruption of the virus particle. In a potassium tartrate density gradient, the major portion of infective virus sedimented at a density of approximately 1.15, and noninfective hemagglutinin, at a density of approximately 1.13. Stock virus preparations appear to contain a large amount of noninfective hemagglutinin. The replication of PVM was not inhibited by 5-fluoro-2'-deoxyuridine, 5-bromo-2'-deoxyuridine, or 5-iodo-2'-deoxyuridine. Infected cells contained eosinophilic cytoplasmic inclusions which showed the acridine orange staining characteristic of single-stranded RNA. Foci of viral antigen were observed in the cytoplasm of infected cells by fluorescent antibody staining. The results suggest that PVM is an RNA virus that replicates in the cytoplasm.

Experimental transmission of influenza virus infection in mice. 3. Differing effects of immunity induced by infection and by inactivated influenza virus vaccine on transmission of infection

Immunization of mice by infection or intraperitoneal injection with homotypic A(2), heterotypic A(0), or recombinant A(0)A(2) virus have differing effects on transmission of influenza A(2) virus infection. Immunization by infection with A(2) virus resulted in refractoriness to reinfection either by artificial aerosols or by exposure to infected cage-mates. Immunization by inoculation with inactivated A(2) virus vaccine resulted in a decreased susceptibility to transmitted infection in immunized contacts, but following A(2) virus challenge, transmission of infection by immunized infectors was not altered. Immunization by infection with influenza A(0) virus or recombinant A(0)A(2) virus resulted in a decreased susceptibility to transmitted A(2) virus infection in immunized contacts, and to decreased transmission after A(2) virus infection in immunized infector mice. These differing effects on transmission of infection are attributed to differences in specific local immunologic responses following the various immunization procedures.