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THE VIRUS OF INFLUENZA

THE LANCET

LONDON: SATURDAY, JULY 8,1933

MANY attempts have been made in the past totransmit influenza to animals. Most of these have

given entirely negative results, but occasional

findings with some of the lower apes have raisedhopes only to be dashed when the experimentscould not be repeated. There always remainedthe human volunteer, and the experiments ofNICOLLE and LEBAILLY (1918), and the successfulhuman transmissions reported in the followingyear by YAMANOUCHI, SAKAKAMI, and IWASHIMApointed to the possibility of investigating influenzain this way. But there are manifest drawbacksto the use of human volunteers as the experi-mental animal for this disease. Not the least ofthese is the fact that a fatal end to an attack ofinfluenza is not unknown ; and although it maybe perfectly true to say that uncomplicatedinfluenza is devoid of this risk, who is going toguarantee that the transmitted disease will remainuncomplicated ? No one could contemplate thetransmission of influenza to human volunteerswithout misgivings. Meanwhile problems of theutmost importance await solution, of which themost obvious are : the nature of the prime causeof influenza, whether a filtrable virus or theinfluenza bacillus so constantly present in this

disease ; the possibility of more than one virusbeing responsible for clinical influenza ; the

relationship of the causal organism of influenzawith that of the common cold. The desire for a

laboratory animal, inexpensive to buy and to

maintain, which would be susceptible to the virusof influenza must thus have distorted the dreamsof most workers in filtrable viruses, for it has

long been realised that such an acquisition wouldopen up wonderful new ground for investigation.

It is almost impossible -therefore to over-estimatethe importance of the discovery, described else-where in this issue, that the ferret is susceptibleto infection with human influenza. The simpleaccount given by WiLsoN SMITH, C. H. ANDREWES,and P. P. LAIDLAw of their successful attempt totransmit influenza to laboratory animals makesa fascinating story. Taking advantage of the

epidemic of the disease which occurred at the

beginning of this year, they tried to infect manydifferent species of animals, using filtered throat-washings obtained from patients as early as

possible after the onset of symptoms. Negativeresults were obtained until they tried infectingferrets which, two days after the nasal instillationof filtered throat-washings, became ill with feverand nasal catarrh. Transmission from ferret toferret by means of suspensions of nasal mucosawere successful; in fact, with one strain 26 serialpassages have been carried out. Quite early in

this work with ferrets it was found that the diseasepassed from ferret to ferret by contact, so the

investigation was moved from the laboratories ofthe National Institute for Medical Research at

Hampstead to the Institute’s farm laboratoriesat Mill Hill, where the regime of rigid isolationevolved for the previous work with distempercould be applied. In all, throat-washings fromeight human patients have been tested on ferrets,and five of these proved infective. Animalswhich had recovered from the infection were

found to be solidly immune to reinfection and theirserum neutralised the virus.. Of the many interest-

ing side-issues of their work, the comparisonwhich the authors have been able to make betweentheir virus and the swine influenza virus of Shopeis worthy of special notice. This virus was isolated

by Shope from a disease of swine which arose

spontaneously during a time of epidemic influenzain America. By itself Shope’s virus produced amild and transitory illness, but when associatedwith a bacterium, Hcemophilus influenzcu (suis),indistinguishable from Pfeiffer’s bacillus, the

complete picture of swine influenza was obtained,Shope’s virus was shown to be infective for ferrets,but what was more interesting, a quite considerablecross-immunity has been found to exist betweenit and the recently isolated human influenzavirus. This cross-immunity was not quite com-plete, for although recovery from the swine virusgave solid immunity to the human virus, animalsrecovered from infection with the human strainwere not completely immune to the swine virus.These findings, however, indicate clearly enougha close antigenic relationship between Shope’svirus and the human influenza virus, and open upthe interesting possibility of swine contractinginfluenza from man.

Needless to say all this work has been most

carefully controlled. The presence of cultivablebacteria in the infective filtrates has been excluded,and it has been shown that the filtered washingsfrom the throat of four normal individuals andone suffering from a common cold were incapableof producing disease in the ferret. When it isadded that the serum of human convalescentsneutralises the virus the story is complete. Althoughthe authors show great modesty in drawing con-clusions from their work, there seems little doubtthat they have succeeded in transmitting influenzato ferrets, and, if they have not finally settled thelong controversy between the , protagonists ofPfeiffer’s bacillus and those of a filtrable virus,they have offered almost conclusive evidence thatthe primary cause of human influenza is a filter-passing virus.

THE TREATMENT OF ANÆMIASTHE anaemias most commonly met with in

general practice are those due to a deficiencyof one or more of the essential haemopoieticfactors. Such deficiencies can readily be relievedby appropriate therapy. There is, however, to-day" much wastage both of material and of humanefficiency and life," as was made clear in an

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important series of papers read at the summer

meeting of the Association of Clinical Pathologistsand printed in full on another page. This wastage,which is preventable, is to a large extent dependentupon two factors : (1) failure to appreciate thenecessity of pathological investigation in diagnosisand in controlling subsequent treatment ; (2)failure to prescribe adequate amounts of certainanti-anaemic preparations owing to the absenceof any indication of their therapeutic potency.The differential diagnosis of various forms ofanaemia can in many instances be made onlyafter a somewhat elaborate pathological investiga-tion, as Dr. S. C. DYKE makes clear, and owingto incomplete diagnosis many patients receivetreatment as useless as it is expensive. Sincethe deficiency in most of the anaemias which affectadults is dependent upon some permanentabnormality, treatment must be continued indefi-nitelv. Moreover the personal variability in theresponse to anti-anaemic factors renders the

laboratory control of both initial and maintenancetreatment essential. Dogmatic statements on

dosage of anti-anaemic principles are thus mis-

leading. The satisfactory dose for any patientcan only be determined by controlled treatment.This applies, as Dr. JANET VAUGHAN said, in thecourse of the animated discussion reported onp. 63, to the use of iron in various forms of

hypochromic anaemia as well as to liver or itssubstitutes in hyperchromic megalocytic anaemias.Difficulties as great have been met in the wide-spread development of insulin therapy, wherethe dosage also has to be checked by the responseof individual diabetics. Here, however, it has

proved possible by laboratory control to establishdosage within certain limits, and massive insulin-medication irrespective of response is now almostobsolete.The resolution passed by the Association of

Clinical Pathologists, urging the establishment ofcentres at which laboratory service would beavailable to patients with anaemia under thenational health insurance has our cordial support.And if, as may be hoped, the voluntary hospitalsare entrusted with this work the arrangementsmade for the treatment and investigation ofinsured patients will be available also for others.Centres organised for periodical laboratory servicewould moreover be admirably adapted to under-take the methodical and controlled assessmentof the potency, of various liver and stomachpreparations which is now so badly needed. At

present clinical trial is the only available methodof assaying potency. It is clearly not an idealmethod, but since there is no reliable alternativeit must be employed. Most liver preparationsare now supplied in units said to be equivalentto the amount of liver from which they are prepared.This definition is adopted in the recent issue ofthe British Pharmacopoeia. It is generally agreedthat potency is lost in extraction, but it does notseem to be generally recognised that extractsmade from a certain weight of liver have notthe therapeutic value of that amount of liver

when it is ingested as cooked food. Some patientsare in consequence receiving inadequate amountsof the anti-anaemic principle. The several extractsmade by different firms also vary in potency;this variation is in part dependent upon themethods of extraction used and in part on unknownfactors. It emerged, however, from last week’sdiscussion and from that held some months agoon the same subject at a meeting of the RoyalSociety of Medicine, section of therapeutics andpharmacology, that certain extracts are generallymore potent and more reliable than others on themarket. These are not necessarily the most

expensive ; the price apparently has no relationto the therapeutic efficiency of the product.There is much clinical data scattered in hospitaland private records which should make it possibleto determine with some degree of accuracy thetherapeutic potency of different preparations.Even an approximate indication of the averageoptimum dose of different products would bemore valuable than a knowledge of the amount ofliver from which they were prepared.The time has clearly come for a scientific body,

e.g., the Medical Research Council, to arrange forthe collection and correlation of the information now

possessed which was not yet available when theB.P., 1932, was being prepared. It should be

possible not only to assess, at least approximately,the average therapeutic potency of differentextracts but to determine the most satisfactorymethods of administration. It is, for instance,now generally accepted by workers treating largenumbers of patients suffering from Addisonian

pernicious anaemia that of the universally applicableforms of " maintenance " treatment, weekly oreven monthly administration of certain intra-muscular preparations made from small quantitiesof liver is the cheapest and most efficient. Thismethod has the further advantage that it is knownto reach the patient himself, instead of beingdistributed, as a dish of liver might be, round thefamily dinner table. It is not by any means atall hospitals that " maintenance " out-patientsreceive parenteral therapy ; but the figures workedout by Dr. DYKE supply evidence which is likelyto popularise this form of treatment on groundsof economy as well as of efficiency. In privatepractice the position is less simple unless patientscan be taught to overcome their dislike of periodicalinjections. Moreover, the cost of a weekly visitto a doctor would to some extent cancel the

economy effected, and certain patients do not

readily acquire the habit of self-injection withoutanxiety. Another outcome of a careful attemptat assay might well be an increase in the potencyof extracts designed for oral administration,though failure of absorption within the gastro-intestinal tract must always be a factor to bereckoned with. Manufacturers have always beenalert to profit by expert help in perfecting theirbiological products and have shown remarkablepromptness and adaptability in applying theresults of controlled investigations. They would

1 See THE LANCET, 1933, i., 84.

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undoubtedly welcome any further attempts todetermine and standardise the potency of extracts.As Dr. GREENFIELD points out, the question of therelation of the deficiency causing anaemia to thelesions of subacute combined degeneration isanother question which requires further study.It is still open to doubt whether all anti-anaemicremedies are equally effective in relieving nervoussymptoms. Even approximate information ofthe therapeutic potency of liver and stomachextracts and of the most reliable methods of theiradministration, combined with facilities forcontrolled treatment, should do much to reducethe present unnecessary wastage of life and ofscientific material.

SERUM IN PNEUMONIAAs long ago as 1891 G. and F. Klemperer

prepared an "

antipneumotoxin " by injectingfiltered sputum into rabbits. The immune serumthey obtained was found to protect a rabbit

against subsequent inoculation with pneumococciand was tried in a few cases of pneumonia. Bythe beginning of this century Foa and Scabia,Jansson (1892), Washbourn (1897), Parr, Biggs,Pane (1897), Tizzoni and Panichi, Romer (1902),and Lambert had independently made effortsto prepare sera from different animals, such asthe horse and the ass, immunised against the

pneumococcus. Pane’s antiserum seems to haveundergone the most extensive tests, but the resultswith all of them were uncertain. Among othersNeisser, Marchoux, and Weissbecker attemptedto combat pneumonia with the serum of con-

valescents, but here again the results were doubtfuland the treatment of the infection with immunesera remained a tantalising problem for the

immunologist. Between 1909 and 1912, however,the pioneer work of Neufeld and Handel laid thefoundation of the subsequent American investiga-tion of the different pneumococcal types, whoseexistence is now well established.The use of the polyvalent sera hitherto employed

now gave place to more accurate attempts to

produce immunisation against one or other of

types 1., II., and III. Most of the first advancesin this direction were made at the RockefellerInstitute for Medical Research in New York,where it was soon discovered that an antiserumto type I. strain offered the best prospect of success.The early results were summarised in a monographon acute lobar pneumonia written from theInstitute by Avery, Chickering, Cole, and Dochezin 1917 with a view to placing the knowledge, thusavailable, at the disposal of army medical officerswho were faced with large numbers of susceptiblerecruits brought together in camps during thewinter months. From that time onwards investiga-tions have been almost continuous. The methodof preparing the serum, as described in 1917, wasby immunisation of horses with a strain of pneumo-coccus virulent enough to kill a mouse in a dose of0.000001 c.cm. For purposes of standardisationnew means had to be devised because no pneumo-coccal toxin had been demonstrated and the

method used for. diphtheria and tetanus antitoxinwas therefore inapplicable. The investigators fellback on the plan-followed by Eyre and Wash-bourn and others many years previously-of usingthe bacteria themselves instead of their toxin,and ultimately a standard of potency was adoptedin which only those sera were selected for thera-peutic use which, in doses of 0’2 c.cm., protectedmice against 0’1 c.cm. of a standard culture.On this basis a dose varying from 80 to 100 c.cm.was employed for therapeutic use.Meanwhile attempts were being made to obtain

concentrated sera. Huntoon, in 1921, had deviseda method of absorbing antibody from antipneumo-coccus serum with homologous living pneumococci,and recovering the antibody by washing the cocciwith weak alkaline saline, and later, in 1925,Felton prepared the concentrated serum which hastaken such an important place in modern serumtherapy. He precipitated his immune substancefrom antipneumococcus serum by diluting withwater or weak acid solution and redissolving insalt solution. Other concentrated sera have followed,though Felton’s has been tried most widely, andsufficient data have been accumulated to encourageimmunologists to persevere in the improvementof methods of production. Dr. Cruickshank inthe Milroy lectures, lately published in our columns,produced figures for the mortality of cases treatedwith and without serum in the United States andGreat Britain. In type I. a mortality of 17’3 percent. is given for 547 serum-treated patients as

against 31’0 per cent. for 477 untreated ; in

type II. a mortality of 33’4 per cent. is foundin 415 treated as compared with 43’3 per cent. in367 untreated. But, as Cruickshank points out,too much stress must not be laid on mortality-rates.Amelioration of symptoms and shortening of theperiod of infection have also to be considered,and it is noteworthy that his temperature chartsof a consecutive series of serum-treated patientsshow a definite shortening of the infection in

type I. and a less definite in type II. cases. Broadlyspeaking, future progress is impeded by three setsof obstacles-clinical, commercial, and immuno-logical. On the clinical side it is often difficultto get cases early enough for serum treatment,and it is not yet generally appreciated that timeis as important here as in many surgical emergencies.There are also anaphylactic difficulties to beovercome and the lesser difficulties attendant

upon all intravenous medication, whilst usefulimmune sera are only available for types I. and II.pneumococcus infections. Added to these draw-backs is the necessity for bacteriological typingwhich requires time and skill, and sputum is notalways available for the purpose. To use type I.serum, for instance, in a type III. or group IV.infection is tantamount to administering normalhorse serum, and nothing more ; and as Dr. G. L.LANGLEY points out on another page, to giveserum where it is fundamentally unsuitable willdo the patient no good and will bring the pre-paration into disrepute. On the commercialside these sera are costly to produce, and