Lee Virus Research Articles

Effects of insulin-like growth factor-type 1 on weight gain and hepatic glycogen during early development in a surfactant/virus mouse model of acute liver failure: correlation with mortality.

Acute liver failure (ALF) was reproduced in young mice exposed daily for 12 days to the industrial surfactant, Toximul 3409F (Tox), and infected on postnatal day (P) 14 with sublethal doses of mouse-adapted human influenza B (Lee) virus (FluB). Combined Tox + FluB treatment potentiated mortality due to non-necrotic ALF. This study tested the hypothesis that mortality would decline if the known losses in energy production due to compromised fatty-acid beta-oxidation were compensated by pharmacological manipulation of hepatic glycogen stores. Glycogen levels, body weights, and mortality were determined without and with injections of insulin-like growth factor-1 (IGF-1). On P25, 13 days after Tox exposure ceased, glycogen levels (mg/100mg) were: 4.0 (control), 1.7 (Tox), 4.3 (FluB), and 2.9 (Tox + FluB). Corresponding cumulative mortalities were 0, 14, 2, and 38%. Following daily IGF-1 injections from P12 to P17, liver glycogen levels on P25 were: 3.5 (IGF-1), 3.9 (IGF-1 + Tox), 12.3 (IGF-1 + FluB), and 5.6 (IGF-1 + Tox + FluB). Unexpectedly, IGF-1 treatment increased mortality to 67% (IGF-1), 89% (IGF-1 + Tox), 63% (IGF-1 + FluB), and 81% (IGF-1 + Tox + FluB). For all groups there was a significant correlation between mortality and poor weight gain. This is the first report of persistent glycogen reductions after surfactant exposure and withdrawal. Their role in potentiating FluB-induced mortality remains to be established.

Surfactant-potentiated increases in intracranial pressure in a mouse model of Reye's syndrome

Severe encephalopathy, the usual cause of death in Reye's syndrome (RS), is characterized by cerebral edema with associated increases in intracranial pressure (ICP). In previous studies, we have shown that exposure of neonatal mice to nontoxic doses of an industrial surfactant and subsequent infection with mouse-adapted influenza B (Lee) virus result in a significant increase in mortality rate and that this is associated with several of the characteristic features of human RS. In the present study we have measured ICP in the young mice undergoing their version of the disease, and we now report that the animals treated with surfactant plus virus experience increases in intracranial pressure that are significantly in excess of those in any of the three control groups. These findings support our hypothesis that this and the other abnormal biochemical and morphological responses in RS are related in some manner to a chemically compromised host.

Serum lipid abnormalities in a chemical/viral mouse model for Reye's syndrome.

Neonatal mice given nontoxic dermal applications of an industrial surfactant, Toximul MP8 (Tox), and subsequently infected with sublethal doses of mouse-adapted human Influenza B (Lee) virus (FluB) develop many of the biochemical features of Reye's Syndrome (RS). To determine whether these also include abnormal circulating lipid, we examined serum lipid profiles in the mouse model throughout the treatment course using Iatroscan-TH10. Following 10 days of exposure to surfactant, serum phospholipid and cholesterol levels were significantly reduced relative to control animals. These reductions were transient; however, four days following virus administration, significant differences in serum lipid were again evident. These abnormalities coincided and correlated with increased animal mortality. Animals that received combined Tox + virus treatment had significant decreases in serum total lipids relative to control animals, a reflection of a reduction in all lipid classes, including phospholipid, cholesterol, neutral glycerides (triglycerides plus diglycerides) and free fatty acids. Phospholipid (specifically phosphatidylcholine and lysophosphatidylcholine) and free fatty acid levels in the Tox + virus group were also significantly lower than those in animals that received virus alone. This study has demonstrated that suckling mice given chemical/viral treatment have the serum hypopanlipidemia but not the freefattyacidemia that are characteristic of RS.

Blocking of the Virus-Enhancing Activity of 5-Methyl-2-d-ribobenzimidazole (MRB)

SummaryDibutyryl-cyclic AMP (db-cAMP, 1 mM) limits the yield of influenza B (Lee) virus in the chorioallantoic membrane from 13-day-old embryonated chicken eggs. In membranes treated with 5-methyl-2-D-ribobenzimidazole (MRB, 3.5 mM), db-cAMP partially or completely blocks enhancement of virus yield by MRB. Eagle's spinner medium does not by itself affect virus yield compared to the yield in a simpler control medium, but it reduces the enhancing effect of MRB by more than 75%.The author thanks Miss Huguette Viguet for excellent technical assistance.

Kinetics and quantitative aspects of enhancement of influenza virus multiplication by 5-methyl-2- d-ribobenzimidazole (MRB)

In multiple cycle infection after a small inoculum, chorioallantoic membranes from 13-day-old chicken embryos produce one-tenth as much influenza B (Lee) virus per unit area as those from 7-day-old embryos. 5-Methyl-2- d-ribobenzimidazole, 3.5 m M, added at the time of infection, increases the yield from the older membranes by 650%, on the average, but has no effect or little effect in the younger membranes. After a large inoculum, membranes from 13-day-old eggs produce high yields, which can only be slightly increased by MRB. Treatment of 13-day-old chorioallantoic membranes with MRB either before or after infection increases Lee virus yield. Maximal enhancement is obtained when treatment is begun before infection and continued for a prolonged period after infection. Detailed examination of the kinetics of enhancement of virus production by MRB has shown that MRB requires several hours to act. However, once an effect has been established, MRB may be removed by washing, and an increased virus yield still obtained many hours later, although there is a decay in the effect with time. MRB is capable of increasing Lee virus yield in membranes in which it is restricted by treatment with reovirus RNA, poly I: C, cycloheximide, 5,6-dichloro-1-β- d-ribofuranosylbenzimidazole, or by dextrose deprivation. MRB also increases Lee virus yield in membranes from COFAL-negative eggs in which influenza virus multiplication is depressed. MRB causes moderate enhancement and virus, of the yield of influenza A/swine/15 slight enhancement of influenza A 1/FM1 and A 2/RI/2 viruses. No enhancement was observed with influenza A 0/WS, A 0/NWS, A 2/RI/1, and A 2/RI/3 viruses.

The chemical reactions of the haemagglutinins and neuraminidases of different strains of influenza viruses: III. Effects of proteolytic enzymes

The action of trypsin and pronase on the haemagglutinins and neuraminidases of eight strains of influenza virus has been examined.The haemagglutinins of all the strains were highly susceptible to digestion by pronase but there were great variations in resistance to trypsin.The neuraminidases of the eight strains were of three types. The neuraminidases of the A 1 strains and the DSP strain of virus A were highly susceptible to destruction by both enzymes. The neuraminidases of the PR 8 and Swine strains showed partial resistance especially to trypsin, while the A 2 strains and the LEE strains of virus B possessed neuraminidases that were completely resistant to both trypsin and pronase.Proteolytic enzymes released free neuraminidases from the A 2 and LEE viruses the morphology of which was different from that of neuraminidases released by detergent treatment.

The chemical reactions of the haemagglutinins and neuraminidases of different strains of influenza viruses. II. Effects of reagents modifying the higher order structure of the protein molecule.

SUMMARYThe results of treatment of influenza virus strains with chemical reagents acting on the higher-order structure of protein molecules shows that both the haemagglutinating and enzymic activities are susceptible to these agents but there are considerable differences between the different strains and the neuraminidase activity is more sensitive than the haemagglutinating activity.The neuraminidase activity of A and A1strains is destroyed by urea, guanidine, urea+dithiothreitol and mercuric chloride. The haemagglutinin of the PR 8 and SWINE strains is resistant to urea and mercuric chloride but destroyed by guanidine and by urea+dithiothreitol. The haemagglutinin of the DSP strain of virus A and the A1strains is resistant to urea, guanidine and mercuric chloride but is destroyed by urea+dithiothreitol.The neuraminidase activity of the A2strains is more resistant than that of the A and A1strains. It is resistant to mercuric chloride and partially resistant to urea but is destroyed by guanidine and by urea+dithiothreitol. The A2haemagglutinin is resistant to urea, urea+dithiothreitol, and mercuric chloride but is destroyed by guanidine.The LEE virus neuraminidase is resistant to urea and partially resistant to guanidine but is destroyed by urea+dithiothreitol and mercuric chloride. The LEE haemagglutinin is resistant to urea, guanidine and mercuric chloride but is destroyed by urea+dithiothreitol.It is suggested that the surface projections of the virus particle are protein polymers each made up of three or four monomers which are the components of the V antigen complex. Antigenic activity is a function of the primary or secondary structure of the monomers, haemagglutinin activity is a function of the tertiary structure of the monomers, while neuraminidase activity is a function of the quaternary structure of the polymer.From studies of the chemical reactions of their haemagglutinins and neuraminidases strains of influenza virus A can be classified into groups. These groups are very similar to but not precisely identical with groupings made by serological methods.

Enhancement of Influenza Virus Multiplication by Chicken Serum

Summary Chicken serum increases the yield of influenza B (Lee) virus several-fold in suspension cultures of chorioallantoic membrane (CAM) in vitro. The mean increase in virus yield at a serum concentration of 23% is 550%. Serum allows the production of an additional amount of 300 to 450 hemagglutinating units (HAU) of virus per 3.8 cm2 of CAM in membranes whose yield in the absence of serum varies from 25 to 160 HAU/3.8 cm2. The percent increase in yield in the presence of serum is inversely related to the yield of virus in untreated controls. The extent of enhancement of virus yield is similar in CAM from 7- and 10-day-old embryonated eggs, but in CAM from 13-day-old eggs and older, chicken serum inhibits viral multiplication. The enhancing activity is approximately 50% dialyzable, and is inactivated to the extent of 40% by heating at 65°C for 30 min. The activity is not inactivated by treatment with trypsin, chymotrypsin, papain, pronase, or deoxyribonuclease I. In some chicken sera there is present a heat labile inhibitor of Lee virus multiplication. Inhibition of virus multiplication by such sera may be slight or marked. After heating at 65°C for 30 min, such sera enhance the multiplication of virus.

The influence of cortisone on experimental viral infection. VII. Kinetics of interferon formation and its inhibition with hydrocortisone in relation to viral strain and virulence.

A comparative study was undertaken of the pathogenesis of infection of the allantoic sac of the chick embryo with three influenza viruses of differing virulence, and of the influence of hydrocortisone on the course of infection. Judged on the basis of earlier onset and greater degree of inflammatory response and diminished survival time of infected embryos, Mel. and Lee viruses were markedly more virulent than PR8, despite the earlier appearance of virus in PR8-infected embryos. Interferon appeared first and in greater quantity in the allantoic fluid of Lee-infected embryos and latest with PR8 infection. Thus, there was no correlation of avirulence and better interferon production with the viruses under study in the present system. Furthermore, evidence obtained suggested that Lee virus ("virulent") was most susceptible to interferon action, and also that viral synthesis in the chorioallantoic membrane with PR8 ("avirulent") persisted after the appearance of interferon. The injection of hydrocortisone within 2 hr of the initiation of infection delayed the synthesis of all three viruses; had no significant effect upon the inflammatory response; and transiently inhibited the synthesis of interferon, while prolonging the survival of Lee- and Mel.-infected embryos. Late administration of hydrocortisone suppresses both the inflammatory response and the production of interferon. Only in the case of Lee virus infection did hydrocortisone administration lead to augmentation of final yields of virus with the low infection multiplicity employed in the present experiments. It is postulated that Lee virus is a better inducer of interferon because its infectivity in vivo is more rapidly inactivated. As a consequence synthesis of Lee virus is more under the control of endogenous interferon than is the case with PR8 or Mel. virus. Therefore, inhibition of interferon synthesis with hydrocortisone has a greater influence on final yields of Lee virus.

The influence of cortisone on experimental viral infection. VI. Inhibition by hydrocortisone of interferon synthesis in the chick embryo.

The initial observations that cortisone may act as an inhibitor of viral interference (11, 4) are now explicable as an inhibitory effect on interferon synthesis. The suggestion that the action of interferon is also inhibited by cortisone or its analogues (6) has not been confirmed in a plaque reduction type of interferon assay system in which autointerference by the challenge inoculum is a lesser problem. In this respect, the present results are in accord with those obtained by DeMaeyer and DeMaeyer (8) with hydrocortisone in a system in which a low multiplicity (0.1) Sindbis virus infection in monolayer culture was employed with cytopathic effect (CPE) as an end-point. It has been shown that hydrocortisone is restrictive to the synthesis of interferon induced by inoculation of either infective or inactivated virus into the chick embryo, and that this inhibitory effect is temporary. However, in another study in the chick embryo, three spaced injections of hydrocortisone (0.25 mg/dose) prevented the appearance of detectable interferon during the entire 64 hr observation period following inoculation of 10(3.3) EID(50) of Lee virus (12). The importance of explicit definition of experimental conditions in assessing hormonal effects on infection is illustrated by the capacity of hydrocortisone either to inhibit or increase interferon synthesis in vitro, depending on the proportion of inactivated and infective virus in the inoculum employed, and the time at which interferon is measured. As suggested previously, it is not unlikely that similar shifts in hormone-virus-interferon balance may operate in vivo to influence the outcome of infection.

Studies on glycoproteins X. Equilibrium measurements on influenza virus-glycoproteins systems

Measurements in systems of enzymically inactive influenza viruses and sialoglycoproteins disclosed an equilibrium between the free reactants and the virus-glycoprotein complex. Equilibrium constants were determined by two methods: equilibrium filtration and ultracentrifugal separation. The glycoproteins tested were influenza virus haemagglutinin inhibitors of high potency (ovine submaxially glycoprotein) and low potency (fetuin, orosomucoid and trypsin-treated OSM). The equilibrium constants (in molar terms) were found to be 1·10 −8 for OSM, 9·10 −7 for fetuin, 2·10 −5 for orosomucoid and 4·10 −6 for the glycopeptides (assumed mol. wt. 50000) obtained by controlled trypsin treatment of OSM. Weight for weight OSM was 17 times more firmly bound to enzymically inactive Lee virus than were its constituent glycopeptides as formed on trypsin treatment. The number of negatively charged terminal sialic acid residues attached simultaneously to complementary groupings at the virus surface, appears to determine primarily the inhibitory potency of the glycoproteins. This determinant is a compound of the number of sialic acid residues available per glycoprotein molecule and of the complementariness of the contacting areas on the surface of virus and glycoprotein.

AN IMMUNOLOGICAL STUDY OF AVIAN, VIRAL AND BACTERIAL NEURAMINIDASE BASED ON SPECIFIC INHIBITION OF ENZYME BY ANTIBODY.

SUMMARY: Antisera were prepared to several strains of influenza virus (grown in the chick embryo), to purified Vibrio cholerae neuraminidase and to partially purified neuraminidase from chick chorioallantois. The ability of the antisera to inhibit the action of each enzyme on substrates of different molecular weight was tested. The substrates used and their molecular weights were sialyl lactose (640), fetuin (48,000) and ovine submaxillary gland mucin, OSM (1 × 106). Antiserum to V. cholerae and avian neuraminidase inhibited strongly the action of the homologous enzyme on each substrate. Antiserum to viral neuraminidase inhibited almost completely homologous action on fetuin and OSM but only partially the action on sialyl lactose. LEE influenza virus was grown in embryonated eggs and in cultures of calf kidney cells and from each preparation a soluble neuraminidase was isolated. Antiserum to the egg-grown virus inhibited the enzyme of both viruses not only in the intact virus particle, but also after separation in the form of a soluble, low molecular weight product. There was little or no serological cross-reaction between any enzyme and heterologous antisera, with one exception. Antiserum to avian neuraminidase partially inhibited (fetuin, but not sialyl lactose, as substrate) the soluble enzyme derived from egg-grown LEE virus, but not from virus grown in cultures of calf kidney cells. It was concluded that the soluble enzyme prepared from LEE virus is a virus specific product but also carries some antigenic determinants characteristic of host specificity.

The structure of influenza viruses: II. C-terminal amino acid analyses

Reaction of influenza B virus (LEE strain) with carboxypeptidase resulted in the rapid and simultaneous release of leucine and tyrosine in the approximate molar ratio of 1.5:1, followed by smaller amounts of other, unidentified amino acids. This result was obtained only when the virus was denatured with formamide or cuprammonium sulphite; practically no amino acids were released from native virus under similar conditions of digestion. Leucine and tyrosine were released only from the fraction of cuprammonium sulphite-treated LEE virus previously shown to be lacking N-terminal aspartic acid. The protein which possessed an N-terminal aspartic acid residue was much less susceptible to the action of carboxypeptidase, and its C-terminal residue was not identified. Fractions obtained by electrophoresis of dodecyl sulphate-disrupted LEE virus were reacted with carboxypeptidase. Equimolar amounts of leucine and tyrosine were split off from the fastest fraction, but from the slowest, the ratio of leucine to tyrosine released was 7.5:1. These results suggest that particles of LEE virus contain at least three different kinds of polypeptide chains. Reaction with carboxypeptidase of the MEL, BEL, and PR8 strains of influenza A virus (denatured by cuprammonium sulphite), resulted in the slow and simultaneous release of about five amino acids from each strain. None of these could be unequivocally identified as C-terminal.

The structure of influenza viruses: I. N-terminal amino acid analyses

Four strains of influenza A virus, PR8, MEL, BEL, and FM1, the LEE strain of influenza B, and the virus of swine influenza have all been found to possess aspartic acid as an N-terminal amino acid. Treatment of the defatted viruses with cuprammonium sulfite yielded a soluble fraction and an insoluble residue. The former was enriched with respect to N-terminal aspartic acid, and the latter was depleted. Complete solubilization of the residue by further treatment with cuprammonium sulfite was achieved in the case of LEE (B) virus only. The extensive purification of LEE (B) virus by adsorption of impurities onto cellulose phosphate is described.

Reactive sites of reovirus type 3 and their interaction with receptor substances

Reactions of reovirus type 3 with erythrocytes, serum components, ovomucin, and L cells were investigated. In most of the experiments, a variant of the Dearing strain was used which differs from the original only in a few properties. The variant, as well as the original Dearing strain, agglutinated ox erythrocytes. Treatment of erythrocytes with Vibrio cholerae filtrate rendered them inagglutinable by these viruses. One hemagglutinating unit of the variant strain corresponded to 6.2 × 10 6 PFU. Normal mouse, rabbit, rat, and calf sera, in order of decreasing activity, inhibited agglutination of ox erythrocytes by reovirus 3. Fetal calf serum showed no inhibitory activity. Treatment of normal mouse, rabbit, and rat sera with V. cholerae filtrate destroyed hemagglutination-inhibiting activity. Ovomucin also possessed hemagglutination-inhibiting activity which was eliminated by V. cholerae filtrate and Lee virus, but not by reovirus 3. Reovirus type 2, Amy strain, did not agglutinate ox erythrocytes, and agglutination of human O cells by the Amy strain was not inhibited by ovomucin. The inhibitory activity of normal animal sera on agglutination of human O cells by this virus was not affected by V. cholerae filtrate. Trypsin and p-chloromercuribenzoate (PCMB) reduced the hemagglutinating activity and infectivity of reovirus 3. PCMB did not disrupt virus particles as shown by negative staining. Clearly, reovirus 3-receptor interaction possesses characteristics which distinguish it from the interactions between receptors and reovirus 2, myxo, entero, and polyoma viruses.

インフルエンザ・ウイルスのマウス感染症 (第7報)

Antibody level in the serum of mice infected with influenza virus via three different routes has been already described. In discussing the participation of immune mechanism on the growth of virus as well as on the fate of experimental animals, rather the series of events accompanied to the establishing process of immune status was thought to be a matter of interest. Having this kind of consideration in mind, antibody titers in various organs of infected mice have been pursued by means of hemagglutination inhibition test.Prior to the experiment, the procedure to remove all of the non-specific hemagglutinin inhibitors from various organ extracts was examined. This was easily done by treating the specimen with cholera filtrate, even when the heated Lee virus was used as an indicator. Then the antibody titer against the PR8 virus, the strain which had been known to be most insensitive to various α-inhibitors has been examined.Main results obtained along the study will be summarized as follows:1) The amount of α-inhibitor both in lung and bronchial washings after intranasal or intraperitoneal infection has been pursued. Inhibitor titer curve obtained against the day was just a mirrorimage to that of virus growth.2) After the inhalation of sublethal amount of PR8 virus or after the intraperitoneal injection of large dosis of alive or formaline-inactivated PR8 virus, the antibody titers of serum, bronchial washing, lung, liver and spleen were examined at appropriate intervals. To visualize the production curve of antibody in any organs concerned, a value “antibody index” was calculated. When antibody titer in some organs at some stage was taken as a numerator, and antibody titer in the sera at the same stage was taken as a denominator, this value was obtained.Only in spleen, the value of antibody index was higher than 1 at an early stage of infection or immunization. This kind of early antibody rise in spleen was never observed at the time of passive immunization when rabbit serum prepared against PR8 virsu was injected intravenously.3) Consolidation parts of the lung found at late stage of infection was also believed to be responsible for the antibody production. The value of antibody index obtained with consolidation parts was apparently higher than that of healthy parts of the same lung, and was almost 2.4) However the antibody found in bronchial washing was thought to be of different nature when compared to that in lung. With the former, the increase in titer was demonstrated by nonspecific stimuli, whereas the fact did not hold true with the latter.

インフルエンザウイルスの種々なるinhibitorに関する研究 (第6報)

Sera obtained from normal guinea pigs, rabbits, chickens and monkeys were examined to characterize the non-specific hemaggultinin inhibitors contained in each. Although preliminary results on this p problem were previously described, reexamination was thought to be necessary after a discovery of the avid Asian virus. High sensitivity of this virus to various inhibitors, again made this problem as an unsettled one.In the study, both heated Lee and Asian P viruses were used to see the different distribution of a and a inhibitors in these sera. Mumps, Sendai and Newcastle disease viruses were also used to characterize each inhibitor, because these hemolytic viruses were known to form irreversible union with red cells, like Asian P virus.Obtained results will be summarized as follows:1) a-inhibitor noticed in guinea pig sera by Shimizu and Ishida using FMI strain of influenza A virus as an indicator, was shown to be the same principle active against Asian set of P virus. This principle was different from a-inhibitor active against heated Lee.2) An inhibitor specifically active against mumps virus was found in monkey sera of both rhesus and cynomologous. Furthermore, with serum specimens obtained from animals other than monkey, inhibitor titer against heated Lee virus.3) Newcastle disease virus was found to be more sensitive to serum specimens received pretreatment of either RDE or KIO4 than that without any treatment. This kind of change was particularly the case with monkey and guinea pig sera, and was assumed to be the same phenomenon as reported as the heat activation phenomenon.

インフルエンザ・ウイルスのマウス感染症 (第6報)

Antibody level in the serum of mice infected with influenza virus via three different routes has been already described. In discussing the participation of immune mechanism on the growth of virus as well as on the fate of experimental animals, rather the series of events accompanied to the establishing process of immune status was thought to be a matter of interest. Having this kind of consideration in mind, antibody titers in various organs of infected mice have been pursued by means of hemagglutination inhibition test.Prior to the experiment, the procedure to remove all of the non-specific hemagglutinin inhibitors from various organ extracts was examined. This was easily done by treating the specimen with cholera filtrate, even when the heated Lee virus was used as an indicator. Then the antibody titer against the PR8 virus, the strain which had been known to be most insensitive to various α-inhibitors has been examined.Main results obtained along the study will be summarized as follows:1) The amount of α-inhibitor both in lung and bronchial washings after intranasal or intraperitoneal infection has been pursued. Inhibitor titer curve obtained against the day was just a mirrorimage to that of virus growth.2) After the inhalation of sublethal amount of PR8 virus or after the intraperitoneal injection of large dosis of alive or formaline-inactivated PR8 virus, the antibody titers of serum, bronchial washing, lung, liver and spleen were examined at appropriate intervals. To visualize the production curve of antibody in any organs concerned, a value “antibody index” was calculated. When antibody titer in some organs at some stage was taken as a numerator, and antibody titer in the sera at the same stage was taken as a denominator, this value was obtained.Only in spleen, the value of antibody index was higher than 1 at an early stage of infection or immunization. This kind of early antibody rise in spleen was never observed at the time of passive immunization when rabbit serum prepared against PR8 virsu was injected intravenously.3) Consolidation parts of the lung found at late stage of infection was also believed to be responsible for the antibody production. The value of antibody index obtained with consolidation parts was apparently higher than that of healthy parts of the same lung, and was almost 2.4) However the antibody found in bronchial washing was thought to be of different nature when compared to that in lung. With the former, the increase in titer was demonstrated by nonspecific stimuli, whereas the fact did not hold true with the latter.

Studies on Cytotropism in Animal Viruses

Summary Infection of tissue cultures derived from hatched chicks and chick embryo lung tissue with the PR8, WS and NWS strains of influenza type A virus and the Lee strain of influenza type B virus showed both tissue culture systems able to support the growth of these viruses at 37°C. At 41°C Lee virus was unable to multiply, and the WS strain was partially inhibited. A similar pattern of results was obtained in vivo, suggesting that a body temperature of 41°C of the hatched chick is the mechanism responsible for the failure of the Lee and WS strains to grow in the lungs of such birds. The PRS and NWS strains were able to grow in both tissue culture systems at 41°C; however, only the PR8 strain was able to persist and perhaps replicate at 41°C in the lungs of hatched chicks. All strains were able to grow in chick embryo lungs in vivo, hence a mechanism other than elevated temperature or absence of cells capable of supporting virus growth is required to explain the failure of the NWS strain to infect hatched chicks.

The reaction of influenza viruses with guinea pig polymorphonuclear leucocytes. III. Studies on the mechanism by which influenza viruses inhibit phagocytosis

The degree of phagocytosis of heat-killed yeast cells by guinea pig polymorphonuclear leucocytes was shown to depend on the presence in the reaction mixture of guinea pig serum and an added substrate such as glucose, glucose-6-phosphate, or fructose-6-phosphate. The concentration of carbohydrate was important in order to obtain maximum phagocytosis. Phagocytosis by polymorphonuclear leucocytes was reduced when the cells had reacted with partially purified Lee virus and were incubated in the presence of serum and glucose or glucose-6-phosphate. When fructose-6-phosphate served as the added substrate, there was no inhibition of phagocytosis. The observed inhibition of phagocytosis by leucocytes to which influenza virus had been adsorbed was postulated to be due to the block in the energy yielding mechanisms of virus-treated cells.