Isoenzymes are different molecular fonns of enzymes with similar enzymatic activity1. Isoenzyme pattern is an arrangement of one or more bands of enzymes. Isoenzyme profile is a series of isoenzymc pattern displayed by a strain or isolate, Zymodeme is an isoenzyme profile shared by one or more strain or isolates. lsoenzymes binding pattern can be used to classify parasite by difference inzymodeme. Different proteins consisting of a set ofisoenzymes have similar but not necessarily identical properties. Hetrogenicity among strains may be due to difference in zyinodeme pattern which distinguishes pathogenesis, virulence or susceptibility to drugs2. Isoenzyme play an important role inparasitic disease3. Variable pathogenicity and virulence has been associated with strains of E. histolytica4,5. Isolates of E. histolytica were clearly differentiated by isoenzyme electrophoresis from patients with clinical amoebiasis and asymptomatic subjects6 and invasive and non-invasive E. histolytica7. Isoenzymes are frequently used to differentiate morphologically similar strains of other human parasitic protozoa8. Other amoeba that inhibit the intestine of man were examined by isoenzyme electrophoresis as morphological identification is difficult. Jsoenzyme pattern of non-pathogenic protozoa Entamoeba coli appear to be entirely different from E. histolytica9. Other non pathogenic protozoa F. hartmani, F. nana, I. butschlii and D. fragilis were compared with E. histolytica by electrophoresis pattern and found to be different10. Isoenzyme electrophoresis has been used to determine genetic interpretation of Trypanosomes11. Isoenzymes are also used to classify Trypanosoma12 and to distinguish different forms of Trypanosoma cmzi involved in sylvatic and domestic cycles13,14. Isoenzymes variation also occurs in Leishmaniasis15,16 Schistosomiasis17 and plasmodial infection18. G. lamblia has been characterized by their isoenzymes pattern. Variation in isoenzyme pattern of G. lamblia correlated with difference in degree of infectivity, clinical pattern and host response to various drugs19. Difference in isoenzyme may distinguish between invasive and non-invasive strains and detection of 0. lamblia strains in symptomatic subjects20. Zymodeme difference occurs between isolates from symptomatic and asymptomatic subjects21. Hetrogenicity of 0. lamblia strains from widely separated areas and within a single region also occurs22. Isolates from single geographical location were genetically homogenous and consistent23. Giardia isolates from animals and humans were homogenous in protein binding pattern and any difference observed showed difference in antigenic reactivity24. Giardia of the same morphologic type and isoenzyme pattern may infect different animal species. Some strains from animal were more virulent25. Giardia antigen showed some minor differences not correlated with geographic location, virulence26, or type of host27. As morphology alone does not always distinguish 0. lamblia from different hosts or different geographic locations, Giarclia isolates may be differentiated by their isoen.zyme profile28. Most commonly isolated isoenzymes are Phosphoglucomutase (PGM), Malic enzyme (ME), Glucose phosphate dehydrogenase (GPI), Hexokinase (HK), Lactate dehydrogenase (LDH) Malic dehydrogenase (MDH), Isocitrate Dehydrogenase (lCD) and Alkaline Phosphatase (AP) enzyme which are used for differentiation of Giardia isolates. As different isoenzymes are presentinG. lamblia, we attempted to see whether Lactate dehydrogenase (LDH) has any relationship with G. lamblia infection. A study was done at PMIRC Research Centre in collaboration with Aga Khan University to determine the relationship of LDH in giardiasis. We collected 12 specimens of duodenal fluid from patients diagnosed positive for 0. lamblia by direct microscopy of stool and G. lamblia antigen detection by ELISA and Immunofluorescence test. A group of 24 apparently healthy adults were also tested. Specific activity of LDH in duodenal fluid was determined by spectrophotometer. LDH isoenzyme was determined by Polyacrylaniide gel electrophoresis (PAGE). Only one patient having active trophozoites in duodenal fluid was positive for LDH. It is possible that LDH might be due to some other disease or secretion of some intestinal metabolite might be providing an environment suitable for trophozoites to flourish in the duodenum. In G. lamblia infection the cellular enzyme LDH remains unaffected29. Giardia strains isolated from faecal samples of rodents were studied by thin layer starch gel electrophoresis at the London School of Hygiene and Tropical Medicine United Kingdom. Isoenzyme detected in Giardia strains from rodents were PGM (Phosphoglucomutase), Nucleoside hydrolase (NH), Alaninc aminotransferase (ALAT), while 6PGD (Phosphoglucose dehydrogenase) was not detected. It is possible that other isoenzymes mightbe present which need to be investigated. What is needed is to determine whether pathogenic or non-pathogenic strains exist in patients with G. lamblia infection or asymptomatic carriers and the role of isoenzymes in G. lamblia resistant strains not responding to drug therapy.
1. Betram, MA., Meyer, E.A., Lile, J.D. et al. A comparison of isoenzyme of five axenic Giardia isolates. J. Parasitol., 1983;69:793-780.
2. Chaudhuri, P.D.A., Bhattachaiya, A., Pal, S.C. et al. Identification ofhetrogenic. ity in human isolates of Giardia lamblia by isoenzyme studies. Int. J. Med. Micro., 1991 ;274:490- 495.
3. Baveja, U.K., Jyoti, AS., Kaur, M et al. Isoenzyme studies of Giardia lamblia isolated from symptomatic cases. J. Exp. Biol. Med., 1986;64 1 19-126.
4. Sargeaunt, PG., Baveja, U. K., Nanda, R. et al. Influence ofgeographical factors in the distribution ofpathogcnic zymodemes XIV in India. Trans. R. Soc. Trop. Med. Hg., 1984;78:96-101.
5. Mirelman, D., Bracha, R.,Wexler, A. eta!. Changes in isoenzymepattemsofa cloned culture in non.pathogcnic Entamoeba histolytica during axenization. Infect. lmmun., 1986;54:827-832.
6. Sargeaunt, P.G., William, J.E., Kumate, J. et al. Theepidemiology ofEntamoeba histolytica in Mexico city. A pilot survey 1. Trans. R. Soc. Trop. Med. Hyg., 1 980;74:653-656.
7. Sargeaunt, P.O., Williams, I.E. and Greene. J.D. The differentiation of invasive and non-nvasive E. histolytica by isoenzyme electrophoresis. Trans. R. Soc. Trop.Med. Hyg., 1978;72:519-521.
8. Sargeaunt, PG. and Williams, I.E. A comparative study of Entamoeba histolytica (NIH: 200, HK 9) “E. histolytica like” and other morphologically identical amoebae using isoenzyme electrophoresis. Trans. R. Soc. Trop. Med. Hyg., I 980;74:464-474.
9. Sargeaunt, P.O. and Williams, I.E. Electrophoresis isoenzyme pattern of Entamoeba histolytica and Entamoeba coli. Trans. R. Soc. Trop. Med. Hyg., 1978;72:164-l68.
10. Sargeaunt, P.G. and Williams, I.E. Electrophoretic isoenzyme pattern of pathogenic and non-pathogenic intestinal amoeba of man. Trans. R. Soc. Trop. Med. Hyg., 1979;73:225-227.
11. Miles, M.A. The epidemiology of South American tiypanosomiasis, biochemical and immunological approaches and their relevance to controls. Trans. R. Soc. Trop. Med.Hyg., 1983;77:5-23.
12. Miles, MA., Laham, S.M., Souza, A.A. et al. Further enzymatic characters of Trypanosoma cruzi and their evaluation for strain identification. Trans. R. Soc. Trop. Med. Hyg., 1980;74:221-237.
13. Miles, M.A., Toye, P.J., Oswald, J.C. et al. The identification by isoenzyme pattern of two distinct stain groups of Trypanosoma cruzi circulating independently in a rural ares ofBrazil. Trans. R Soc. Trop.Med. Hyg., 1 977;71 :217-224.
14. Andrade, V., Brodo, K. Y.N.C and Andrade, SO. Correlation between isoenzyme pattern and biological behaviour ofdifferent strains of Trypanosoma cruzi. Trans. R. Soc. Trop. Med. Hyg., l983;77:769-799.
15. Kreutzer, R.D. and Christensen, MA. Characterization of Leishmania spp. by isoenzymeelectrophoresis. Am. J. Trop. Med.Hyg., 1980;29:199-208.
16. Kreutzer, R.D., Samko, ME., Hendricks, L.D. et at. Identification of Leishmania spp. by multiple isoenzyme analysis. Am. J. Trop. Med. Hyg., 1983;32:703-715 5.
17. Mahon, R. 3. and Shiff, C.J. Electrophoresis to distinguish haematobium and S. matthcei cerceriae emerging from Bulinus snails. J. Parasitol., 1978;64:372373.
18. Carter, R. Studies on enzyme variation in the murine malaria parasite Plasmodium perghei, P. volelli, P. chabanda by starch gel Electrophoresis. Parasitology, 1 978;76:241 -267.
19. Moss, D.M.. Visvesvara, G.S.,Mathew. N.M. et al. Isoenzyme comparison of axenic Giardia Iamblia strains. J. Protozoal., I 992;39:559-564.
20. Abaza, SM., Sullivan, J.J. and Visvesvara, OS. Isoenzyme profile of four strains of Giardia lamblia and their infectivity tojirds. Am. J. Trop. Med. Hyg., 1991 ;44:63-68.
21. Cediollo-Riveria, R. and Enciso-Moreno, J.A., Martinez-Palemo and Ortega Pierras, 0. Giardia Iamblia isoenzyme analysis of 19 axenic strains isolated from symptomatic and asymptomatic patients in Mexico. Trans. R. Soc. Trap. Med. Hyg., 1989;83:644- 646.
22. Meloni, B.P., Lumbery, A.J. and Thompson, R.C.A. Isoenzyme electrophoresis of 30 isolates of Giardia from human and felines. Am. J. Trop. Med. Hyg., 1 988;38:65-73.
23. Korman, SE., LeBlancq, SM., Spira, D.T. et al. Giardia lamblia identification of different strains from man. Z.Parasitol., 1986;72:173-180.
24. Forrest, M, Isaac-Renton, J. and Bowie, K. Immunoblot patterns of Giardia duodenalis isolates from different hosts and geographical locations. Can. J. Microbiol., 1990;36:42-46.
25. Aggarwal, A.,Bhatia, A., Naik, S.R. et al. Variable virulence of isolates of Giardia lamblia in mice. Ann. Trop. Med. Parasitol., 1 983;77:328-331.
26. Capon, A.G., Upcroft, J.A., Boreham, P.F.L. eta!. Similarities of Giardia antigens derivedfromhumanandanimalsources. Int. J. Parasitol., 1989;19:91-98.
27. Proctor, E.M., Isaac Renton, J.L., Boyd, J. et al. Isoenzyme analysis of human and animal isolates of Giardia duodenalis from British Columbia Canada, Am. J. Trop. Med. Hyg., l989;41 :411-415.
28. Owen, R.L. The immune response in clinical and experimental giardiasis. Trans. R. Soc. Trop. Med. Hyg., 1980;74:433-445.
29. Chawla, L. S., Sehgal, A.K., Broor, S.L. et al. Tryptic activity in the duodenal aspirate following a standard test meal in giardiasis. Scand. 3. Gastroentero!., 1975,10:445-447.