EXPERIMENTAL INFECTION WITH INFLUENZA A VIRUS IN MICE

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.

Download Full-text

1343. Prophylactic Dosing of Baloxavir Acid Eliminates Mortality in Mice Lethal Influenza A Virus Infection Model

Open Forum Infectious Diseases ◽

10.1093/ofid/ofy210.1174 ◽

2018 ◽

Vol 5 (suppl_1) ◽

pp. S410-S411

Author(s):

Shinya Shano ◽

Keita Fukao ◽

Takeshi Noshi ◽

Kenji Sato ◽

Masashi Sakuramoto ◽

...

Keyword(s):

Weight Loss ◽

Body Weight ◽

Virus Infection ◽

Influenza A Virus ◽

Influenza A ◽

Lethal Dose ◽

Body Weight Loss ◽

Prophylactic Efficacy ◽

Body Weights ◽

Single Dosing

Abstract Background Baloxavir acid (BXA), an active form of orally available prodrug baloxavir marboxil (BXM, formerly S-033188), is a novel small molecule inhibitor of cap-dependent endonuclease (CEN) of influenza A and B virus, and was recently launched for the treatment of acute and uncomplicated influenza with single dosing of BXM (the trade name XOFLUZA™) in Japan in March 2018. Here, we evaluated the prophylactic efficacy of BXA in mice lethally infected with influenza A virus. Methods T1/2 of BXA in human is more than 10 times longer than that in mice. Therefore, suspension of BXA was subcutaneously administered at 0.8 or 1.6 mg/kg in mice to maintain the plasma concentration of BXA as seen in humans, and then mice were intranasally inoculated with a lethal dose of A/PR/8/34 strain at 48, 72, or 96 hours after the administration of BXA. Survival time and body weight change were then monitored through a 28-day period after virus infection. Mice were euthanized and regarded as dead if their body weights were lower than 70% of the initial body weights according to humane endpoints. Results Single dosing of BXA (1.6 mg/kg) completely eliminated mortality in mice, when the mice were administrated the drug at 48, 72, or 96 hours before virus infection (Figure 1). BXA treatment also significantly prevented body weight loss, consistent with the prolonged survival. Conclusion Prophylactic dosing of BXA exhibited significant protective efficacy against mortality and body weight loss in mice following a lethal infection with influenza A virus. The significant prophylactic efficacy observed in our mouse model suggests the potential utility of BXM for the prophylaxis of influenza in human. Disclosures S. Shano, Shionogi & Co., Ltd.: Employee, Salary. K. Fukao, Shionogi & Co., Ltd.: Employee, Salary. T. Noshi, Shionogi & Co., Ltd.: Employee, Salary. K. Sato, Shionogi & Co., Ltd.: Employee, Salary. M. Sakuramoto, Shionogi & Co., Ltd.: Employee, Salary. K. Baba, Shionogi TechnoAdvance Research & Co., Ltd.: Employee, Salary. T. Shishido, Shionogi & Co., Ltd.: Employee, Salary. A. Naito, Shionogi & Co., Ltd.: Employee, Salary.

Download Full-text

Mutation of Influenza A Virus PA-X Decreases Pathogenicity in Chicken Embryos and Can Increase the Yield of Reassortant Candidate Vaccine Viruses

Journal of Virology ◽

10.1128/jvi.01551-18 ◽

2018 ◽

Vol 93 (2) ◽

Cited By ~ 5

Author(s):

Saira Hussain ◽

Matthew L. Turnbull ◽

Helen M. Wise ◽

Brett W. Jagger ◽

Philippa M. Beard ◽

...

Keyword(s):

Host Cell ◽

Influenza A Virus ◽

Influenza A ◽

Control Measure ◽

Virus Titer ◽

Virus Antigen ◽

Economic Consequences ◽

Primary Control ◽

X Protein ◽

X Gene

ABSTRACTThe PA-X protein of influenza A virus has roles in host cell shutoff and viral pathogenesis. While most strains are predicted to encode PA-X, strain-dependent variations in activity have been noted. We found that PA-X protein from the A/PR/8/34 (PR8) strain had significantly lower repressive activity against cellular gene expression than PA-X proteins from the avian strains A/turkey/England/50-92/91 (H5N1) (T/E) and A/chicken/Rostock/34 (H7N1). Loss of normal PA-X expression, either by mutation of the frameshift site or by truncating the X open reading frame (ORF), had little effect on the infectious virus titer of PR8 or PR8 7:1 reassortants with T/E segment 3 grown in embryonated hens’ eggs. However, in both virus backgrounds, mutation of PA-X led to decreased embryo mortality and lower overall pathology, effects that were more pronounced in the PR8 strain than in the T/E reassortant, despite the low shutoff activity of the PR8 PA-X. Purified PA-X mutant virus particles displayed an increased ratio of hemagglutinin (HA) to nucleoprotein (NP) and M1 compared to values for their wild-type (WT) counterparts, suggesting altered virion composition. When the PA-X gene was mutated in the background of poorly growing PR8 6:2 vaccine reassortant analogues containing the HA and neuraminidase (NA) segments from H1N1 2009 pandemic viruses or from an avian H7N3 strain, HA yield increased up to 2-fold. This suggests that the PR8 PA-X protein may harbor a function unrelated to host cell shutoff and that disruption of the PA-X gene has the potential to improve the HA yield of vaccine viruses.IMPORTANCEInfluenza A virus is a widespread pathogen that affects both humans and a variety of animal species, causing regular epidemics and sporadic pandemics, with major public health and economic consequences. A better understanding of virus biology is therefore important. The primary control measure is vaccination, which for humans mostly relies on antigens produced in eggs from PR8-based viruses bearing the glycoprotein genes of interest. However, not all reassortants replicate well enough to supply sufficient virus antigen for demand. The significance of our research lies in identifying that mutation of the PA-X gene in the PR8 strain of virus can improve antigen yield, potentially by decreasing the pathogenicity of the virus in embryonated eggs.

Download Full-text

THE PRODUCTION OF FEVER BY INFLUENZAL VIRUSES

Journal of Experimental Medicine ◽

10.1084/jem.90.4.321 ◽

1949 ◽

Vol 90 (4) ◽

pp. 321-334 ◽

Cited By ~ 25

Author(s):

Robert R. Wagner ◽

Ivan L. Bennett ◽

Virgil S. LeQuire

Keyword(s):

Influenza A Virus ◽

Low Temperatures ◽

Influenza A ◽

Immune Serum ◽

Influenza B ◽

Chick Embryos ◽

Febrile Response ◽

Virus Particles ◽

Chicken Erythrocytes

The intravenous injection of the PR8 strain of influenza A virus, the Lee strain of influenza B, and the "B" strain of Newcastle disease virus produces fever in rabbits. This phenomenon has been studied in relation to certain in vitro properties of these viruses. Saline suspensions of virus prepared by centrifugation or elution from chicken erythrocytes produced fever. Fluids from which most of the virus particles had been removed were non-pyrogenic. Exposure to temperatures which destroyed the infectivity of the virus for chick embryos did not prevent fever. However, heating sufficient to destroy the hemagglutinin also rendered virus non-pyrogenic. The injection of erythrocytes onto which virus had been adsorbed produced fever. Heated virus adsorbed onto erythrocytes, which failed to elute, produced no elevation of temperature, although heated virus alone was pyrogenic. Neutralization of virus with specific immune serum prevented fever. Antipyrine was capable of abolishing the febrile response to virus. Certain differences between the febrile response in rabbits to the injection of viruses and that following bacterial pyrogens were noted. The period between injection and beginning of temperature rise is longer with virus than with bacterial pyrogens. Relatively low temperatures inactivate the fever-producing capacity of viruses, whereas bacterial pyrogens withstand prolonged autoclaving, and the neutralization of viral fever by specific immune serum contrasts sharply with the failure of antibody to affect the response to bacterial pyrogens. Certain previous observations on the lymphopenia produced in rabbits by the injection of influenzal viruses were confirmed. The capacity of virus preparations to induce fever in rabbits closely parallels their capacity to induce lymphopenia. It was concluded that the fever-producing property of influenzal viruses is closely associated with the capacity to agglutinate erythrocytes.

Download Full-text

VirPreNet: A weighted ensemble convolutional neural network for the virulence prediction of influenza A virus using all 8 segments

10.1101/2020.07.31.230904 ◽

2020 ◽

Author(s):

Rui Yin ◽

Zihan Luo ◽

Pei Zhuang ◽

Zhuoyi Lin ◽

Chee Keong Kwoh

Keyword(s):

Public Health ◽

Neural Network ◽

Convolutional Neural Network ◽

Influenza A Virus ◽

Influenza A ◽

Lethal Dose ◽

Influenza Viruses ◽

Numerical Representation ◽

Influenza A Viruses ◽

Linear Layer

AbstractMotivationInfluenza viruses are persistently threatening public health, causing annual epidemics and sporadic pandemics. The evolution of influenza viruses remains to be the main obstacle in the effectiveness of antiviral treatments due to rapid mutations. Previous work has been investigated to reveal the determinants of virulence of the influenza A virus. To further facilitate flu surveillance, explicit detection of influenza virulence is crucial to protect public health from potential future pandemics.ResultsIn this paper, we propose a weighted ensemble convolutional neural network for the virulence prediction of influenza A viruses named VirPreNet that uses all 8 segments. Firstly, mouse lethal dose 50 is exerted to label the virulence of infections into two classes, namely avirulent and virulent. A numerical representation of amino acids named ProtVec is applied to the 8-segments in a distributed manner to encode the biological sequences. After splittings and embeddings of influenza strains, the ensemble convolutional neural network is constructed as the base model on the influenza dataset of each segment, which serves as the VirPreNet’s main part. Followed by a linear layer, the initial predictive outcomes are integrated and assigned with different weights for the final prediction. The experimental results on the collected influenza dataset indicate that VirPreNet achieves state-of-the-art performance combining ProtVec with our proposed architecture. It outperforms baseline methods on the independent testing data. Moreover, our proposed model reveals the importance of PB2 and HA segments on the virulence prediction. We believe that our model may provide new insights into the investigation of influenza [email protected] and ImplementationCodes and data to generate the VirPreNet are publicly available at https://github.com/Rayin-saber/VirPreNet

Download Full-text

Features of immune response against influenza infection in animals vaccinated with recombinant cross-protective vaccine

Russian Journal of Infection and Immunity ◽

10.15789/2220-7619-2019-3-4-485-494 ◽

2019 ◽

Vol 9 (3-4) ◽

pp. 485-494

Author(s):

L. M. Tsybalova ◽

L. A. Stepanova ◽

A. V. Korotkov ◽

M. A. Shuklina ◽

M. V. Zaitseva ◽

...

Keyword(s):

Immune Response ◽

T Cells ◽

Influenza Virus ◽

Influenza A Virus ◽

Cd4 T Cells ◽

Influenza A ◽

Influenza Infection ◽

Sublethal Dose ◽

Universal Vaccine ◽

Toll Like Receptor 5

Generating cross-reactive vaccines aimed at targeting all human influenza A virus subtypes is among high priority tasks in contemporary vaccinology. Such vaccines will be primarily demanded during pre-pandemic period as well as used to prime some population cohorts prior to vaccination with standard vaccines containing area-relevant epidemic virus. Unlike routine approach universal vaccines do not induce a sterilizing immunity, but significantly ameliorate overt infection and probable complications. Our study was aimed at evaluating characteristics of immune response in experimental animals primed with a candidate universal vaccine challenged with sublethal influenza A virus infection. Mice were immunized intranasally with the recombinant protein FlgH2-2-4M2e containing conservative peptides derived from two influenza A virus proteins: M2 protein ectodomain and 76–130 amino acid sequence from the second hemagglutinin (HA2) subunit genetically linked to bacterial flagellin protein, which is a ligand for Toll-like receptor 5 (TLR5). Control mice received saline. Two weeks after immunization, mice from both groups were infected with a sublethal dose of A/Aichi/2/68 AN3N2 influenza virus strain. Level of immunoglobulins G and A in the blood sera and bronchoalveolar lavages (BAL) were determined two weeks after immunization and 1 month post infection. Percentage of lung CD4+ T and CD4+ Tem (CD44+CD62L–) cells secreting cytokines TNFα, IFNγ, IL-2 was determined. Immunized vs. control mice responded to sublethal infection with the influenza virus by insignificant weight loss and more pronounced production of vaccine peptide-specific (M2e and aa76–130 HA2) and pan-influenza A/Aichi/2/68 virus IgG and A in the blood sera and BAL. After challenge the number of CD4+ T cells secreting cytokines TNFα and/or IL-2 in immunized mice significantly exceeded counterpart T cells in unimmunized animals that was true for both CD4+T and CD4+ Tem cells. Memory CD4+ T cells were previously shown to play a key role in the prime-boost event and heterosubtypic immune response. Thus, we were able to demonstrate a priming effect for recombinant cross-protective vaccine used in our experiment.

Download Full-text

Rule-based meta-analysis reveals the major role of PB2 in influencing influenza A virus virulence in mice

BMC Genomics ◽

10.1186/s12864-019-6295-8 ◽

2019 ◽

Vol 20 (S9) ◽

Cited By ~ 2

Author(s):

Fransiskus Xaverius Ivan ◽

Chee Keong Kwoh

Keyword(s):

Random Forest ◽

Influenza A Virus ◽

Survival Data ◽

Influenza A ◽

Meta Analysis ◽

Lethal Dose ◽

Viral Proteins ◽

Learning Approaches ◽

Rule Based ◽

Better Than

Abstract Background Influenza A virus (IAV) poses threats to human health and life. Many individual studies have been carried out in mice to uncover the viral factors responsible for the virulence of IAV infections. Nonetheless, a single study may not provide enough confident about virulence factors, hence combining several studies for a meta-analysis is desired to provide better views. For this, we documented more than 500 records of IAV infections in mice, whose viral proteins could be retrieved and the mouse lethal dose 50 or alternatively, weight loss and/or survival data, was/were available for virulence classification. Results IAV virulence models were learned from various datasets containing aligned IAV proteins and the corresponding two virulence classes (avirulent and virulent) or three virulence classes (low, intermediate and high virulence). Three proven rule-based learning approaches, i.e., OneR, JRip and PART, and additionally random forest were used for modelling. PART models achieved the best performance, with moderate average model accuracies ranged from 65.0 to 84.4% and from 54.0 to 66.6% for the two-class and three-class problems, respectively. PART models were comparable to or even better than random forest models and should be preferred based on the Occam’s razor principle. Interestingly, the average accuracy of the models was improved when host information was taken into account. For model interpretation, we observed that although many sites in HA were highly correlated with virulence, PART models based on sites in PB2 could compete against and were often better than PART models based on sites in HA. Moreover, PART had a high preference to include sites in PB2 when models were learned from datasets containing the concatenated alignments of all IAV proteins. Several sites with a known contribution to virulence were found as the top protein sites, and site pairs that may synergistically influence virulence were also uncovered. Conclusion Modelling IAV virulence is a challenging problem. Rule-based models generated using viral proteins are useful for its advantage in interpretation, but only achieve moderate performance. Development of more advanced approaches that learn models from features extracted from both viral and host proteins shall be considered for future works.

Download Full-text

DNA-Epitope Vaccine Provided Efficient Protection to Mice Against Lethal Dose of Influenza A Virus H1N1

Viral Immunology ◽

10.1089/vim.2013.0080 ◽

2014 ◽

Vol 27 (1) ◽

pp. 14-19 ◽

Cited By ~ 6

Author(s):

Huiling Wei ◽

Stephen D. Lenz ◽

David H. Thompson ◽

Roman M. Pogranichniy

Keyword(s):

Influenza A Virus ◽

Influenza A ◽

Lethal Dose ◽

Virus H1n1 ◽

Epitope Vaccine ◽

Efficient Protection

Download Full-text

1350. Therapeutic Effects of Baloxavir Marboxil against Influenza A Virus Infection in Ferrets

Open Forum Infectious Diseases ◽

10.1093/ofid/ofy210.1181 ◽

2018 ◽

Vol 5 (suppl_1) ◽

pp. S413-S413

Author(s):

Mitsutaka Kitano ◽

Takanobu Matsuzaki ◽

Ryoko Oka ◽

Kaoru Baba ◽

Takahiro Noda ◽

...

Keyword(s):

Body Temperature ◽

Oral Administration ◽

Influenza A Virus ◽

Influenza A ◽

Virus Titer ◽

Therapeutic Effects ◽

Single Oral Administration ◽

Influenza A Virus Infection ◽

Oseltamivir Phosphate ◽

Over Time

Abstract Background Baloxavir marboxil (BXM) is a novel small molecule inhibitor of cap-dependent endonuclease that is essential for influenza virus transcription and replication. In this study, pharmacokinetic profiles of BXM and baloxavir acid (BXA), an active form of BXM, were first examined in ferrets, and then the therapeutic effects of BXM against influenza A virus infection were compared with that of oseltamivir phosphate in ferrets. Methods The plasma exposure of BXA and BXM was examined after a single oral administration of BXM at doses of 10 and 30 mg/kg. The concentrations in plasma were determined by liquid chromatography-tandem mass spectrometry(LC/MS/MS). For efficacy study, ferrets infected intranasally with A/Kadoma/2006 (H1N1) were administrated 10 or 30 mg/kg of BXM orally twice daily for 1 day, starting at 1 day post-infection (p.i.) or administrated 10 mg/kg of BXM orally twice daily for 1 day, starting at 2 days p.i.. Oseltamivir phosphate was administered at doses of 5 mg/kg orally twice daily for 2 days as a comparison. The virus titer in the nasal washes and body temperature change were monitored during infection. Results BXA was detected in ferret plasma after a single oral administration of BXM at 10 and 30 mg/kg, in more than a dose-proportional manner. When the treatment was initiated at 1 day p.i., BXM at 10 and 30 mg/kg showed reduction of virus titer to an undetectable level on day 2 p.i. and statistically significant reduction in virus titer over time from day 2 to 3 p.i. compared with vehicle and oseltamivir phosphate. Moreover, the change of body temperature over time from 8 hours after the first administration to 3 days p.i. was significantly lower in BXM at 10 and 30 mg/kg than vehicle and oseltamivir phosphate. These effects were also observed in ferrets treated with BXM at 10 mg/kg even when administered at 2 day p.i. where ferret exhibit fever that is more than 1 degree higher than on 1 day p.i.. Conclusion Single-day oral administration of BXM had beneficial effects on viral titer and symptoms in ferrets infected with influenza A virus, which were superior to those observed with oseltamivir phosphate and vehicle. Disclosures M. Kitano, Shionogi & Co., Ltd.: Employee, Salary. T. Matsuzaki, Shionogi & Co., Ltd.: Employee, Salary. R. Oka, Shionogi & Co., Ltd.: Employee, Salary. K. Baba, Shionogi TechnoAdvance Research & Co., Ltd.: Employee, Salary. T. Noda, Shionogi TechnoAdvance Research & Co., Ltd.: Employee, Salary. Y. Yoshida, Shionogi & Co., Ltd.: Employee, Salary. K. Sato, Shionogi & Co., Ltd.: Employee, Salary. R. Yoshida, Shionogi & Co., Ltd.: Employee, Salary. A. Sato, Shionogi & Co., Ltd.: Employee, Salary. H. Kamimori, Shionogi & Co., Ltd.: Employee, Salary. T. Shishido, Shionogi & Co., Ltd.: Employee, Salary. A. Naito, Shionogi & Co., Ltd.: Employee, Salary.

Download Full-text

Greater Efficacy of Black Ginseng (CJ EnerG) over Red Ginseng against Lethal Influenza A Virus Infection

Nutrients ◽

10.3390/nu11081879 ◽

2019 ◽

Vol 11 (8) ◽

pp. 1879 ◽

Cited By ~ 7

Author(s):

Eun-Ha Kim ◽

Son-Woo Kim ◽

Su-Jin Park ◽

Semi Kim ◽

Kwang-Min Yu ◽

...

Keyword(s):

Survival Rate ◽

Influenza A Virus ◽

Influenza A ◽

Respiratory Infections ◽

Virus Titer ◽

Inflammatory Cells ◽

Lavage Fluid ◽

Negative Control ◽

Red Ginseng ◽

Black Ginseng

Black ginseng (BG, CJ EnerG), prepared via nine repeated cycles of steaming and drying of fresh ginseng, contains more accessible acid polysaccharides and smaller and less polar ginsenosides than red ginseng (RG) processed only once. Because RG exhibits the ability to increase host protection against viral respiratory infections, we investigated the antiviral effects of BG. Mice were orally administered either BG or RG extract at 10 mg/kg bw daily for two weeks. Mice were then infected with a A(H1N1) pdm09 (A/California/04/2009) virus and fed extracts for an additional week. Untreated, infected mice were assigned to either the negative control, without treatments, or the positive control, treated with Tamiflu. Infected mice were monitored for 14 days to determine the survival rate. Lung tissues were evaluated for virus titer and by histological analyses. Cytokine levels were measured in bronchoalveolar lavage fluid. Mice treated with BG displayed a 100% survival rate against infection, while mice treated with RG had a 50% survival rate. Further, mice treated with BG had fewer accumulated inflammatory cells in bronchioles following viral infection than did mice treated with RG. BG also enhanced the levels of GM-CSF and IL-10 during the early and late stages of infection, respectively, compared to RG. Thus, BG may be useful as an alternative antiviral adjuvant to modulate immune responses to influenza A virus.

Download Full-text

Some Fundamental Experiments on Immunity, Illustrated

Journal of Hygiene ◽

10.1017/s0022172400002059 ◽

1904 ◽

Vol 4 (1) ◽

pp. 31-72 ◽

Cited By ~ 1

Author(s):

E. F. Bashford

Keyword(s):

Lethal Dose ◽

Test Tube ◽

Immune Serum ◽

Normal Serum ◽

Weight Of Evidence ◽

Passive Immunity ◽

Artificial Immunity ◽

The Difference

By means of the graphic records given on Plates II–VI and VIII the following facts have been illustrated.Immunity to Erythrocytes.Normal rabbit's serum is relatively innocuous for bullock's erythrocytes. The serum of an immunised rabbit acquires the power to dissolve bullock's erythrocytes.Besides acquiring the power to dissolve bullock's erythrocytes, an immune serum may also acquire power to clump them, and it has been shown that the phenomena of haemolysis and of agglutination are independent.The powers acquired by the immune serum can be artificially modified. The serum may be deprived of its powers by heat. Serum cautiously so deprived of its haemolytic power can have it restored by the addition of normal serum. The haemolytic power of the un-heated serum is augmented if normal serum be superadded.It has been shown that an immune serum only differs from a normal serum by its containing antitoxic bodies which are endowed with powers of specific reaction with the bullock's erythrocytes.The mechanism by which erythrocytes are laked by an immune serum has been analysed, and it has been shown that the solution of the erythrocytes is effected through the intervention of an anti-erythrocytic body called forth by immunisation. The erythrocytes which have been subjected to the action of this product of immunity give indication of their reaction with it if they are subsequently or concomitantly placed under the influence of normal serum. The erythrocytes and normal serum together, therefore, form a combined indicator of the presence of the anti-eiythrocytic body. The part played by normal serum has nothing to do with the acquisition of immunity.The only conclusion drawn from the above observations is that in the production of immunity to erythrocytes the serum of the immunised animal acquires certain powers which are concomitant with, but are not necessarily the cause of the immunity. This special case of immunity to erythrocytes is therefore probably parallel to induced immunity to those bacterial toxines for which antitoxines are known to exist.The course and progressive augmentation of artificial immunity to erythrocytes has also been illustrated, and it has been shown that erythrocytes saturated with anti-erythrocytic body retain the power to augment the immunity of an already immune animal.The serum of an animal actively immunised has power to confer passive immunity upon other animals, and the course of this passive immunity differs in the two cases when it is induced in the same species and in a species alien to that providing the immune serum.The experiments with bullock's erythrocytes have been repeated in parallel observations with ricin in order to permit of the observations on haemolysis being utilised in drawing conclusions on the behaviour of bacterial toxines.By adjusting the conditions of experiment in such a way that the minimal lethal dose for an animal was also the minimal agglutinating dose in test-tube experiments, it has been possible to give graphic records showing the parallelism between the processes when erythrocytes or living animals are used as indicators of the presence of free ricin. In this way it has been possible to illustrate the determination of the minimal lethal and minimal agglutinating doses of ricin and that quantity of antitoxine (antiricin) which is necessary to abolish the corresponding actions in the animal and in the test-tube, and to show that the mixture of toxine and antitoxine which is physiologically neutral in vitro is also physiologically neutral in vivo within the limitations imposed by the preliminary determinations.The consequences of conferring passive immunity upon the guinea-pig by means of active immune serum of the rabbit have also been illustrated, and it has been shown that the alien antiricin serum leads to the production of agencies directed against itself.Ricin neutralised by antiricin retains its power to produce immunity when injected into the species of animal which has yielded the antiricin.In connection with the conference of immunity to erythrocytes and to ricin, the nature of the difference between normal and immune sera has been studied. Attention has been directed to the possession by normal sera of properties which simulate those possessed in more marked degree by the immune sera. In the case of haemolysis, it has not been possible to clearly demonstrate that the actions manifested by the normal and immune sera are distinct, although the weight of evidence is in favour of this view. In the case of ricin, however, it has been possible to demonstrate that the immune serum possesses properties which are quite distinct from those possessed by normal serum, and that the latter does not interfere with the action of ricin because of the natural presence of a trace of antiricin. In the case of immunity to ricin, the antitoxine is certainly something which has been super-added to the serum in consequence of the process of immunisation.The facts ascertained in regard to artificial immunity to erythrocytes and to ricin completely agree. Only in oue point is it impossible to be quite sure that the phenomena are identical, viz., in the simulation by normal serum of the powers characteristic of the immune serum; for the demonstration that the two are distinct has been possible for ricin, but open to doubt in the case of erythrocytes. My investigations have been extended to diphtheria and tetanus toxines and to cobra venom, kindly placed at my disposal by Sir Thomas R. Fraser. They have however been interrupted, but so far as they go they support fully the observations made on ricin and erythrocytes.

Download Full-text