Martha López-Osuna

Inhibition of human monocyte locomotion by products of axenically grown E. histolytica

Summary The supernatant fluid of axenically grown E. histolytica inhibits chemotaxis, chemokinesis and random mobility of human mononuclear phagocytes (MP) as measured in Boyden chambers. Human polymorphonuclear phagocytes (PMN) locomotion is apparently unaffected. The factor was found in comparable amounts in the supernatant fluid of axenic cultures of four E. histolytica strains that differed in their human pathogenicity and virulence, as well as in two entamoebas non‐pathogenic for man. This dialysable and thermolabile MP‐locomotion inhibiting entamoeba product (EP) can be absorbed out by incubation with MP, but not with lymphocytes, while partial absorption was observed using PMN. The MP‐locomotion inhibitory effect of this EP was cancelled by inhibiting protein synthesis in the MP by means of cycloheximide. In vivo, this EP caused a delay in MP migration in Rebuck skin windows. The molecular weight of this EP lies between 478 and 765 by gel‐sieve chromatography. Our results suggest a direct effect upon the cytoskeletal and locomotive apparatus of the MP. This MP‐locomotion inhibiting EP could contribute to the paucity of the inflammatory reaction observed in the advanced stages of invasive amoebiasis and consequently also to the lack of scar tissue formation upon healing of amoebic lesions.

Immunization with a tetramer derivative of an anti‐inflammatory pentapeptide produced by Entamoeba histolytica protects gerbils (Meriones unguiculatus) against experimental amoebic abscess of the liver

Axenically grown Entamoeba histolytica produces a pentapeptide (Met‐Gln‐Cys‐Asn‐Ser) with several anti‐inflammatory properties, including the inhibition of human monocyte locomotion (Monocyte Locomotion Inhibitory Factor (MLIF)). A construct displays the same effects as the native material. It remains to be seen if MLIF is used, or even produced in vivo by the tissue‐invading parasite. If MLIF were to be relevant in invasive amoebiasis, immunizing against it could diminish this parasite advantage and prevent lesions. KLH‐linked MLIF mixed with Freunds adjuvant was too aggressive an immunizing material to answer this question. However, immunization with a tetramer of MLIF (but not a scrambled version of MLIF) around a lysine core (MLIF–MAPS), that displays increased antigenicity, yet lacks excessive innate immunity activation, completely protects gerbils against amoebic abscess of the liver caused by the intraportal injection of virulent E. histolytica. Liver abscesses caused by Listeria monocytogenes were not prevented. Invasive E. histolytica may produce the parent protein of MLIF in vivo, and if appropriately cleaved, it may play a role in invasive amoebiasis. MLIF may join new vaccination strategies against amoebiasis.

Does the eosinophil have a protective role in amebiasis

While normal human eosinophils are destroyed in vitro by virulent Entamoeba histolytica, notwithstanding the presence of antibodies and complement, activated eosinophils promptly destroy the parasite although dying also at the end of the process. To study the possible in vivo participation of eosinophils in invasive amebiasis, we compared the induction of experimental amebic abscess of the liver (AAL) in gerbils (Meriones unguiculatus) previously made eosinophilic through Toxocara canis antigen injection and in normal control gerbils. After intraportal inoculation of 10(5) ameba trophozoites (6 and 24 hr), the ratio of gerbils with AAL, as well as the number and size of the microabscesses was comparable in eosinophilic and control gerbils. However, at 96 hr the number and size of the microabscesses were significantly smaller (p < 0.05) in eosinophilic gerbils. On the other hand the actuarial AAL survival curve up to 45 days post-amebic inoculation was significantly (p < 0.05) shifted to the right in controls. These results suggest that antigen-induced eosinophilia may exert a protective effect against AAL in gerbils.

Destruction of normal human eosinophils by Entamoeba histolytica

Summary We evaluated the in‐vitro interaction of normal human eosinophil leucocytes and a virulent strain of Entamoeba histolytica (HM1‐IMSS) in the presence of immune serum. At a 10:1 (eosinophil:amoeba) ratio a significant time‐dependent destruction of eosinophils was found from the first hour onward, and a similar, albeit weaker, cytopathic effect was found in the 200:1 ratio mixtures, with some delay in the microscopic evidence of such effect. Results were unaffected by serum factors, and amoebae emerged virtually unharmed throughout these experiments, again regardless of the presence of serum factors. These results indicate that, as with neutrophil leucocytes, virulent E. histolytica is capable of destroying normal human eosinophils in vitro.

Increased susceptibility to experimental amebic abscess of the liver (EAAL) in gerbils (Meriones unguiculatus) with induced eosinopenia.

Normal human eosinophils—the same as neutrophils and mononuclear phagocytes—are killed in vitro by trophozoites of virulent Entamoeba histolytica , the parasite emerging unscathed from the event (1). However, if eosinophils are activated beforehand, the amebas are destroyed even if the leukocytes themselves eventually succumb in the process as well (2). Eosinophils, regularly present in the early inflammatory reaction of experimental amebic abscess of the liver (EAAL), are in strikingly close contact with the invading parasite (3), and because gerbils (Meriones unguiculatus) with induced eosinophilia are more resistant to EAAL than their normal counterparts (4), we explored further the role played by the eosinophil in invasive amebiasis by studying the course of EAAL in gerbils with induced eosinopenia.

Immunoglobulins and beta-1-C globulin in hydatidiform mole vesicles.

Qualitative and quantitative determinations of immunoglobulins (Igs) and beta-1-C globulin were carried out in fluid vesicles of hydatidiform moles and carrier mothers. The mean concentration of IgG was 9.9 per cent, IgA had 14.3 per cent, in relation to maternal values. No IgM concentrations were detected in molar fluid. Beta-1-C globulin showed 60.5 per cent concentration in relation to mothers serum. It is suggested that in trophoblast of molar vesicles a selective transudate migration of Igs by a mechanism of pinocytosis takes place to the vesicular fluid.

Induction of protective immunity against experimental amebic abscess of the liver (EAAL) using the monocyte locomotion inhibitory factor (MLIF) produced by Entamoeba histolytica: a preliminary report.

MLIF is an anti-inflammatory oligopeptide produced by Entamoeba histolytica in axenic cultures that among other effects inhibits the locomotion of human peripheral blood monocytes [hence, its name, monocyte locomotion inhibitory factor (MLIF)]. This factor may contribute to the paucity of the late inflammatory reaction found in invasive amebiasis, but this, in turn, may allow for the perfect regeneration of the affected organs (liver, skin) observed upon successful treatment (1). In any event, however, we do not yet know whether E. histolytica actually uses—or even produces—MLIF in vivo. If it does, MLIF may be an evasion factor of the ameba against the inflammatory defenses of the host. We, therefore, attemped to induce protective immunity against experimental amebic abscess of the liver (EAAL) by using a MLIF-KLH complex as an immunogen (2).