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marrow transplantation may cost as much as 1000.Attention has therefore turned to alternative means of

preventing acute GVHD.The notion of removing immunocompetent lympho-

cytes from the donor marrow is far from new. As longago as 1968 Dicke and co-workers" reported successwith the technique for preventing GVHD in rodents.These results were amply confirmed in other animals,including primates. Within the past few years pilotstudies in man have suggested that when donor marrowis incubated with suitably absorbed rabbit anti-human-T-cell sera before transplantation, the incidence andseverity of subsequent GVHD are reduced Now theavailability of a whole battery of monoclonal antibodiesthat specifically bind to mononuclear cells of theimmune system (with or without complement) hasopened up the possibility of specific cell populationsbeing purged from the marrow before transplantation.The two papers at the front of this issue describedifferent ways of removing such immunocompetentcells, so that immunosuppression may not be requiredin the recipient. The group from Minnesota reportresults with specific monoclonal antibodies linked to apowerful toxin. In two patients, a cocktail of three anti-T-cell antibodies bound to intact ricin eliminated func-tional T cells without affecting myeloid precursors.Engraftment in both patients was good. And DrPrentice and his co-workers from the Royal FreeHospital, London, treated eleven patients with marrowdepleted of virtually all identifable donor marrow Tlymphocytes by means of two specific anti-T-cellmonoclonal antibodies, one a pan-peripheral T-cellantibody and the other reacting with T8+ lympho-cytes of the suppressor cytotoxic type. Nine of theeleven patients escaped GVHD and the remaining twohad mild grade I disease affecting only the skin. All butone of the patients survive (although follow-up is

short). What are the implications of these findings?On existing evidence, patients treated with

immunodepleted marrow have a high rate of

engraftment, a low incidence of GVHD, and nolong-term complications associated with the

immunodepletion. However, in terms of GVHD theadvantages may not be great because, although GVHDdevelops in up to 70% of cyclosporin-treated patients,the morbidity is slight and all but 5% recover. Otherregimens will not easily improve on these results.

Although cyclosporin is expensive, time in hospitalmust be considered and there are indications of slower

engraftment in patients receiving marrow depleted ofT cells. One difficulty with the bone-marrow-purgingtechnique stems from the vast array of antibodiesavailable. New antibodies are offered almost daily, andcocktails expand the permutations exponentially.

11. Dicke KA, Van Hooft J, Van Bekkum DW. The selective elimination of

immunologically competent cells from bone marrow and lymphatic cell mixtures.Transplantation 1968; 6: 562-70.

12. Rodt H, Kolb HJ, Netzel B, et al. Effect ofanti-T cell globulin on GVHD in leukaemicpatients treated with BMT. Transplant Proc 1981; 13: 257-61.

Another is the proliferation of new centres startingsmall pilot studies on bone marrow transplantation,reducing the numbers referred to major centres that aretrying to assess new regimens in large homogeneousgroups of patients. The need today is for controlledstudies, in matched patients with the same disease, ofT cell purging versus, say, a standard cyclosporinprotocol. Such investigations should examine not onlythe obvious indices such as rate of GVHD and overallsurvival, but also logistic factors that may be importantif bone marrow transplantation is to win a place instandard management of diseases such as acute

leukaemia.

CRYPTOSPORIDIOSIS

INTEREST in diagnosing particular infectious diseaseswaxes and wanes, and a fashionable agent at the moment isthe coccidian parasite Cryptosporidium, discovered in 1907. IThe stimuli for this interest are probably twofold-therecognition of cryptosporidiosis as a disease of veterinaryimportance, particularly in calves;2-4 and the severe

symptoms produced by cryptosporidiosis in

immunocompromised patients, particularly those with

acquired immunodeficiency syndrome (AIDS).5The parasite’s life-cycle is direct, through faecal-oral

transmission, and is typical of Eimeriidae with asexual andsexual stages of reproduction. Characteristically the

endogenous stages (2-6 m in diameter) are enclosed in aparasitophorous vacuole in the microvillous border of

enterocytes in small and large intestine.6 However, otherepithelial surfaces have on occasion been infected,particularly bile and pancreatic ducts, gallbladder, andrespiratory tract. 5,7,8 ,

Cryptosporidiosis in man manifests as two clinicallydistinct conditions-either a self-limiting gastroenteritis innormal patients, or a chronic life-threatening diarrhoea inimmunologically compromised individuals. The cases ofinfection in immunologically normal patients that have so farbeen reported in detail number thirty-two.9-1’ Ages ranged

1. Tyzzer EE. A sporozoan found in the peptic glands of the common mouse. Proc Soc ExpBiol Med 1907; 5: 12-13.

2. Pohlenz J, Moon HW, Cheville NF, Bemrick WJ. Cryptosporidiosis as a probablefactor in neonatal diarrhoea of calves. J Am Vet Med Assoc 1978; 172: 452-57.

3. Angus KW. Cryptosporidiosis in man, domestic animals and birds: a review. J Roy SocMed 1983; 76: 62-70.

4. Tzipori S. Cryptosporidiosis in animals and humans. Micro Rev 1983; 47: 84-96.5. Pitlik SD, Faunstein V, Garza D, Guarda L, Bolivar R, Rios A, Hopfer RL, Mansell

PA. Human cryptosporidiosis: spectrum of disease. Arch Intern Med 1983; 143:2269-75

6. Bird RG, Smith MD. Cryptosporidiosis in man: Parasite life cycle and fine structuralpathology. J Pathol 1980; 132: 217-33.

7. Kovatch RM, White JD. Cryptosporidiosis in two juvenile rhesus monkeys. Vet Pathol1972; 9: 426-40.

8. Mason RW, Hartley WJ. Respiratory cryptosporidiosis in a peacock chick. Avian Dis1980; 24: 771-76.

9 Nime FA, Burek JD, Page DL, Hoescher MA, Yardley JH. Acute enterocolitis in ahuman being infected with the protozoan Cryptosporidium. Gastroenterology 1976;70: 592-98.

10. Tzipori S, Angus KW, Gray EW, Campbell I. Vomiting and diarrhoea associated withcryptosporidial infection. N Engl J Med 1980; 303: 818.

11. Anderson BC, Donndelinger T, Wilkins RM, Smith J. Cryptosporidiosis in a

veterinary student. J Am Vet Med Assoc 1982; 180: 408-09.12. Reese NC, Current WL, Ernst JV, Bailey WS. Cryptosporidiosis of man and calf: a case

report and results of experimental infections in mice and rats. Am J Trop Med Hyg1982; 31: 226-29.

13. Centers for Disease Control. Human cryptosporidiosis. Morbid Mortal Weekly Rep1982; 31: 252-53.

493

from 2 months to 35 years, and all but two cases were

symptomatic, with a self-limiting influenza-like

gastrointestinal illness. Diarrhoea was the outstandingsymptom, but most patients also had fever, abdominal pain,and nausea, and constipation was occasionally reported.Duration of diarrhoea ranged from 3 to 10 days, and allpatients recovered. In addition to these cases there isinformation from three surveys of patients with

gastrointestinal symptoms in the UK, Australia, and

Finland. 18-° Of nearly 3000 stool samples examined, slightlyover 2% contained cryptosporidial oocysts. Infection wasmore common in children than in adults.There are published records of forty-nine immuno-

compromised patients with cryptosporidiosis.5,17,21-31 Mostof these patients had AIDS, but others had immunoglobulindeficiencies or were under immunosuppressive therapy. Allpatients had severe protracted watery diarrhoea (up to

12 litres/day), often with fever, substantial weight loss (up to50% of initial weight), abdominal pain, and lymph-adenopathy. Diarrhoea commonly continued intermittentlyor continuously for many months. Infection in such patientswas usually fatal, although most had other conditionsassociated with their immunodeficiencies. One patientrecovered after discontinuation of immunosuppressivetherapy.21 1No therapeutic agent has been found effective in treating

natural cases of cryptosporidiosis in man or animals,although a wide range ofantiprotozoals and antibacterials hasbeen tried.27 In experimental infections in calves and micemany drugs have been used both prophylactically andtherapeutically, but no satisfactory treatment has so far been

14. Fletcher A, Sims TA, Talbot IC. Cryptosporidial enteritis without general or selectiveimmune deficiency. Br Med J 1982; 285: 22-23.

15. Baxby D, Hart CA, Taylor C. Human cryptosporidiosis: a possible case of hospitalcross infection. Br Med J 1983; 287: 1760-61.

16. Blagburn BL, Current WL. Accidental infection of a researcher with human

cryptosporidium. J Inf Dis 1983; 148: 772-73.17. Current WL, Reese NC, Ernst JV, Bailey WS, Heyman MB, Weinstein WM. Human

cryptosporidiosis in immunocompetent and immunodeficient persons. N Engl JMed 1983; 308: 1252-57.

18. Casemore DP, Jackson B. Sporadic cryptosporidiosis in children. Lancet 1983; ii: 679.19. Tzipori S, Smith M, Birch C, Barnes G, Bishop R. Cryptosporidiosis in hospital

patients with gastroenteritis. Am J Trop Med Hyg 1983; 32: 931-34. 20. Jokipii L, Pohjola S, Jokipii AMM. Cryptosporidium: a frequent finding in patients

with gastrointestinal symptoms. Lancet 1983; ii: 358-6121 Meisel JL, Perera DR, Meligro C, Rubin CE. Overwhelming watery diarrhoea

associated with a cryptosporidium in an immunosuppressed patient.Gastroenterology 1976; 70: 1156-60.

22. Lasser KH, Lewin KJ, Ryning FW. Cryptosporidial enteritis in a patient withcongenital hypogammaglobulinaemia. Hum Pathol 1979; 10: 234-40.

23 Weisburger WR, Hutcheon DF, Yardley JH, Roche JC, Hillis WD, Charoche P.Cryptosporidiosis in an immunosuppressed renal transplant recipient with IgAdeficiency. Am J Clin Pathol 1979; 72: 473-78.

24. Stemmermann GN, Hayashi T, Glober GA, Oishi N, Frankel RI. Cryptosporidiosis,report of a fatal case complicated by disseminated toxoplasmosis. Am J Med 1980;69: 637-42.

25. Weinstein L, Edelstein SM, Madara JL, Falchuk KR, McMannus BM, Trier JR.Intestinal cryptosporidiosis complicated by disseminated cytomegalovirusinfection. Gastroenterology 1981; 81: 584-91.

26. Sloper KS, Dourmashkm RR, Bird RB, Slavin G, Webster ADB. Chronic

malabsorption due to cryptosporidiosis in a child with immunoglobulin deficiency.Gut 1982; 23: 80-82.

27. Centers for Disease Control. Cryptosporidiosis: Assessment of chemotherapy of maleswith acquired immune deficiency syndrome (AIDS). Morbid Mortal Weekly Rep1982; 31: 589-92.

28. Andreani T, Modiguani R, Le Charpentier Y, Galian A, Brouet J, Liance M, LachanceJ, Messing B, Vernisse B. Acquired immunodeficiency with intestinal

cryptosporidiosis: possible transmission by Haitian whole blood. Lancet 1983; i:1187-91.

29. Jonas C, Deprez C, De Maubeuge J, Taelman H, Panzer JM, Deltenre M.

Cryptosporidium in patients with acquired immunodeficiency syndrome. Lancet1983; ii: 964.

30. Malebranche R, Arnous E, Guerin JM, Pierre GD, Laroche AC, Pean-Guichard C,Elie R, Morisset PH, Spira T, Mandeville R, Drotman P, Seemayer T, Dupoy JM.Acquired immunodeficiency syndrome with severe gastrointestinal manifestationsin Haiti. Lancet 1983; i: 873-78.

31. Miller RA, Holmberg RE, Clausen CR. Life-threatening diarrhea caused bycryptosporidium in a child undergoing therapy for acute lymphocytic leukemia. JPediatr 1983; 103: 256-59.

found.32-34 However, in immunologically normal humansand animals, disease is self-limiting; patients make a

spontaneous clinical recovery and parasite excretion in stoolbecomes undetectable. In immunocompromised patients, onthe other hand, the outlook is grave. Fluid and electrolytetherapy and parenteral nutrition have been successful insustaining patients for several months, but in these casescryptosporidiosis has persisted until death.Although there are clear differences in biological behaviour

between different strains,4 many strains from animals andman can be shown to infect and cause disease in species otherthan the original host. 12, 17,35 Cryptosporidiosis thus haspotential to be a zoonosis, and many of the sporadic cases inman have been in individuals in contact with

animals-notably calves, which were in some cases known tobe infected.11,12,17 However, these animal-associated casesmay have assumed an undue importance owing to the greaterinterest of the veterinarian in diagnosing the condition.Certainly in most of the immunocompromised patients therewas no history of animal contact,5 and direct human-to-human transmission can occur.’ 5,16Diagnosis depends on demonstration of the parasite, either

of endogenous stages in situ on intestinal mucosa obtained bybiopsy or at necropsy, or more commonly of oocysts in stool.Oocysts can be identified by flotation and examination byphase-contrast microscopy,36 or by staining with Giemsa,Ziehl-Neelsen, or various other methods and examination bylight microscopy. "-31 With practice the oocysts can bereadily recognised as 4 jum diameter spherical structures,typically with an unstained peripheral halo, and up to foursporozoite nuclei and the residual body may be visible withinthe oocyst. Despite the interest in cryptosporidiosis as adisease, studies on Cryptosporidium as a parasite are in theirinfancy. At the Animal Diseases Research Association’sMoredun Institute in Edinburgh, techniques have beendeveloped for oocyst purification and enumeration, for

excystation of sporozoites, and for infection in cell cultureand embryonated eggs. These should allow much-neededprogress to be made in biological and antigenic strain

comparison, in immunological studies, and in in-vitro

screening of potential therapeutic agents.Cryptosporidium is thus not an exotic parasite of marginal

clinical interest, but one that will take its place as a recognisedhuman pathogen. What that place is, remains to be defined:the dramatic symptoms of cryptosporidiosis in AIDS cases,while instrumental in bringing the condition to the forefront,may turn out to be of no more overall importance than thewidespread but much milder cases of gastroenteritis innormal children or adults. Cryptosporidiosis as a possiblepathogen in the much greater problem of diarrhoea in thedeveloping countries also remains to be assessed.

32. Angus KW, Hutchison G, Campbell I, Snodgrass DR. The prophylactic effects of anti-coccidial drugs in experimental murine cryptosporidiosis. Vet Rec 1984; 114:166-68.

33. Tzipori S, Campbell I, Angus KW. The therapeutic effect of 16 antimicrobial agents onCryptosporidium infection in mice. Aust J Exp Biol Med Sci 1982; 60: 187-90.

34. Moon HW, Woode GN, Ahrens FA. Attempted chemoprophylaxis of

cryptosporidiosis in calves. Vet Rec 1982; 110: 181.35. Tzipori S, Angus KW, Campbell I, Gray EW. Cryptosporidium: Evidence for a single

species genus. Infect Immun 1980; 30: 884-86.36. Anderson B. Patterns of shedding of cryptosporidial oocysts in Idaho calves. J Am Vet

Med Assoc 1981; 178: 982-84.37. Snodgrass DR, Angus KW, Gray EW, Keir WA. Cryptosporidia associated with

rotavirus and an Escherichia coli in an outbreak of calf scour. Vet Rec 1980; 106:458-59.

38. Garcia LS, Bruckner DA, Brewer TC, Shimuzu RY. Techniques for the recovery andidentification of Cryptosporidium oocysts from stool specimens. J Clin Microbiol1983; 18: 185-90.

39. Baxby D, Blundell N. Sensitive, rapid simple methods for detecting cryptosporidiumin faeces. Lancet 1983; ii: 1149.