Antigenic Analysis of Entamoeba Histolytica by Means of Fluorescent Antibody

V. Comparison of 15 Strains of Entamoeba with Information on their Pathogenicity to Guinea Pigs

Morris GoldmanU. S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Laboratory of Parasitic Diseases, Bethesda, Maryland 20014

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Louis T. CannonU. S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Laboratory of Parasitic Diseases, Bethesda, Maryland 20014

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Summary

The antigenicity of five strains of E. histolytica capable of multiplying at 25°C or lower, as well as at 35°C, was compared with that of eight strains of classic E. histolytica. All strains were grown at 35°C and were exposed to the same dilution of a single fluorescent anti-E. histolytica serum mixed with nonfluorescent normal or anti-E. histolytica sera. Fluorescence was measured with a microfluorimeter. Both groups showed a spectrum of fluorescent brightnesses for their component strains, but the average was 36.2 for body-temperature strains and only 21.2 for the reduced-temperature group. Clear distinction, without overlap between the two groups, occurred in inhibition reactions with a single unlabeled antiserum.

Three lines from a single strain of body-temperature amebae, cultured separately for several years under different conditions and tested after 1½ to 9 months under the same cultural conditions, showed significant differences in brightness. However, the inhibition pattern for all three strains was comparable to that of the other body-temperature amebae.

Reactions of a single strain of E. moshkovskii were indistinguishable from those of reduced-temperature E. histolytica. On the other hand, a strain of E. coli was clearly different from any of the E. histolytica strains on the basis of its inhibition pattern.

None of the reduced-temperature E. histolytica and neither E. moshkovskii nor E. coli were infective to guinea pigs. Six out of nine cultures of body-temperature E. histolytica infected guinea pigs, causing mild to extensive pathologic changes in the cecum. The other three strains were noninfective.

Author Notes

Present address: Bionetics Research Laboratories, Kensington, Maryland 20795.

Present address: Walter Reed Army Institute of Research, Washington, D. C. 20012.

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