Lactose hydrogen breath test in Giardia lamblia-positive patients

The study was conducted in 54 adult patients with Giardia lamblia infection and 54 adult controls to detect lactose maldigestion employing the noninvasive lactose hydrogen breath test. Forty of 54 (74%) patients with Giardia lamblia and 24 of 54 (44.4%) controls showed lactose maldigestion (P < 0.01). In conclusion, this study shows that the frequency of lactose maldigestion is significantly higher in adult Indians suffering from Giardia lamblia infection compared to healthy individuals.

Cellular and serological markers of disease activity in Indian patients with HIV/AIDS

There has been an exponential rise of HIV positive patients as observed at the surveillance center of Nehru Hospital. Most patients are poor and cannot afford repeated viral load assays. Therefore, there is a need to identify cost effective and reliable surrogate markers of disease activity. In the present study absolute number of CD4 cells, beta2 micro-globulin, circulating nucleosomes were studied in 30 patients of AIDS, 30 seropositives and 30 healthy controls. In addition viral load, P-24 assay, and TNFR-II assays were done in seropositive and AIDS patients. The mean CD4 cells in patients with AIDS were 69.66 +/- 68.25 mm3 while in seropositives values was 370 +/- 201.29 mm3. The mean CD4 cells in healthy controls were however 690 +/- 198 mm3. The differences in all the groups were highly significant (p<0.001). The mean CD4 values in Indians are significantly lower than reported from the west. The lower number of CD4 cells in healthy population is interpreted to be due to immune activation. The CD8 cell number in controls was 650 +/- 207 mm3 this figure is also higher than that observed in the west. P-24 assay failed to delineate between seropositives and patients with AIDS. Although, beta2 microglobulin levels were significantly higher in AIDS than in seropositives and higher in seropositives than in controls yet with the best possible cut off, it had a sensitivity of only 70% in delineating the two conditions. The correlation between CD4 cells and viral load was more significant when the CD4 cells were below 200 mm3. Five out of 30 patients with a CD4 of 300-600 mm3 had a viral load of over 1 x 10(5) cop/ml. The difference in TNF R-II levels between seropositives and AIDS was however more impressive. With a cut off of 550 pg/ml it had a sensitivity of 95% in delineating HIV from AIDS. It is concluded that a combination of absolute number of CD4 cells and TNF R-II assay along with clinical evaluation may be used to monitor therapy in resource poor countries where frequent viral load assay is unaffordable.

Identification and characterization of an excretory-secretory product from Giardia lamblia

A 58 kDa excretory-secretory product (ESP) of Giardia lamblia has been characterized. The ESP was purified over 508-fold by a combination of ammonium sulphate precipitation and sequential chromatography on affinity matrix and a gel filtration column. The homogeneity of the purified protein was established by sodium dodecyl sulphate polyacrylamide gel electrophoresis (Mr, 58 kDa) and analytical isoelectrophoresis (pI 4.75). The purified protein was recognized by the pooled sera of G. lamblia-positive patients as well as an antiserum raised against crude Giardia extract, thus indicating it to be an immunodominant parasite product. The ESP was found to agglutinate rabbit erythrocytes. The haemagglutinating activity of this protein was inhibited strongly by thyroglobulin, fetuin, asialofetuin and monosialoganglioside but not by simple sugars. The purified protein was characterized immunochemically and was found to be heat stable as well as protease sensitive. Lectin-binding studies of the purified ESP and its sensitivity to periodic-acid silver staining as well as to metaperiodate treatment clearly indicated its glycoprotein nature. The major localization site of the ESP was found to be on the surface of the parasite as revealed by flow cytometric analysis. Further, this glycoprotein induced fluid accumulation in ligated rabbit ileal loops and revealed a positive skin permeability reaction in the rabbit.

Effect of Giardia lamblia on duodenal disaccharidase levels in humans

The study was conducted to detect the effect of giardiasis on human disaccharidase levels. Forty patients attending the medical outpatient department of PGIMER, Chandigarh were enrolled. Twenty patients, positive for Giardia lamblia comprised the study group while 20 patients negative for Giardia lamblia were taken as controls. Upper gastrointestinal endoscopy was performed in all patients. Estimation of lactase, sucrase, maltase and trehalase was done in biopsies. Histopathological investigation was carried out in all biopsy specimens after Haematoxylin and Eosin staining. Complaints of pain abdomen and bloating occurred commonly in giardiasis. Four biopsy samples in study group showed mild increase in lymphomononuclear infiltrate. Giardia lamblia was detected in 7 biopsies. Lactase levels were decreased significantly (p < 0.05) in giardiasis. Rest of the enzymes were comparable to the controls. No differences in the enzyme activities were observed between males and females in either group and with the duration of symptoms.

Partial characterization of a 36-kDa antigen of Entamoeba histolytica and its recognition by sera from patients with amoebiasis

A 36-kDa antigen of axenically grown pathogenic Entamoeba histolytica (HM1-IMSS) was eluted from the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)-resolved crude amoebic extract antigens. The immunoreactivity of this partially purified 36-kDa antigen with monoclonal antibody (MoAb) 3D(10) altered significantly (P<0.01) after heat and trypsin treatment but remained unaltered after treatment with sodium metaperiodate (P0.5), thereby indicating the protein nature of the epitope recognized by MoAb 3D(10). The epitope was found to be localized on the surface as well as in the cytoplasm of the E. histolytica trophozoites with the majority of it in the cytoplasm. In addition, this epitope was also found to be present on the cyst form of the parasite. The 36-kDa molecule was recognized by the sera from 29 (85%) of the 34 patients with amoebic liver abscess and five (83%) of the six patients with amoebic colitis. No serum samples from asymptomatic cyst passers, from patients with non-amoebic hepatic or intestinal disorders and apparently healthy subjects had antibodies that reacted with this 36-kDa molecule. The immune responses in man to this 36-kDa amoebic molecule indicate a potential specific role for this molecule in invasive amoebiasis.

A monoclonal antibody-based test system for detection of Entamoeba histolytica-specific coproantigen

BACKGROUND

Diagnosis of amebiasis based on stool microscopy or demonstration of anti-amebic antibodies has limitations. A diagnostic system based on demonstration of the parasite product in clinical specimens holds promise.

METHODS

Murine monoclonal antibodies were developed against an Entamoeba histolytica-specific coproantigen. A monoclonal antibody (MoAb) 3D10 was employed in a double-antibody sandwich microELISA system for the detection of amebic coproantigen in fecal specimens. The system was evaluated in three groups of subjects: 63 patients with intestinal amebae, 27 with non-amebic parasitosis, and 57 apparently healthy controls.

RESULTS

The MoAb 3D10 belonged to IgG1 isotype and recognized three antigens, with mol. wt. 36, 25 and 17 kDa in the crude extract of E. histolytica (HM1-IMSS), and an amebic coproantigen with MW 36 kDa in the stool supernatant from patients with intestinal amebae. The coproantigen was detected in the stool eluates of 56 (89%) patients with intestinal amebae and in none of the stool eluates from other subjects, thereby giving this system a sensitivity of 89% and specificity of 100% for the detection of intestinal amebae.

CONCLUSIONS

This monoclonal antibody recognizes as intact epitope on the E. histolytica-specific coproantigen. The validity of the MoAb-based microELISA system needs to be established.

Immune effector responses to an excretory-secretory product of Giardia lamblia

The prior immunisation of mice with purified excretory-secretory product (ESP) led to a complete failure of Giardia lamblia colonisation following challenge inoculation of these animals with trophozoites. The prior immunisation of mice with ESP resulted in a significant stimulation of local immunity as evidenced by a significant enhancement of T helper/inducer activity along with a significant increase in immunoglobulin A-bearing cells. Further, the presence of anti-ESP antibodies in the serum of immunised as well as immunised-challenged animals indicated the stimulation of the systemic lymphoid system. This suggests that the ESP is highly immunogenic and it could be one of the major antigens of G. lamblia responsible for protection against the infection.

Differential tropism of EB rotavirus (serotype 3) to small intestine of homologous murine model

The 4-5 days-old NMRI strain infant mice were orally inoculated with EB rotavirus (serotype 3). The intestinal disaccharidases activity was studied separately in three segments of the small intestine i.e. duodenum, jejunum and ileum on day 1 to 7 post inoculation (p.i.). The severity of EB rotavirus infection correlated with a significant decrease of small intestinal lactase, maltase and sucrase on day 3 p.i. The level of maltase after the initial decline increased in all the three segments of small intestine of infected mice. However, the lactase activity remained suppressed for a relatively longer period in ileum of infected mice than in controls. These enzymes began to approach to normal value by day 5 p.i., but in ileum, lactase activity continued to be severely depressed even on day 7 p.i. Rotavirus was consistently detected in intestinal contents by ELISA on days 1 to 7 p.i. The infected mice showed a significant increase in rotavirus (serotype 3)-specific serum IgG and IgM antibody level during the declining (days 5-7 p.i.) phase of infection. Diarrhoea was noted up to day 6 p.i. The protracted suppression of the lactase activity in ileum in comparison to duodenum and jejunum showed a differential tropism of EB rotavirus (serotype 3) strain to the small intestine of homologous murine model.

Significance of detection of immune-complexed 8 kDa hydatid-specific antigen for immunodiagnosis of hydatidosis

Three micro-enzyme-linked immunosorbent assay (micro-ELISA) systems were developed and evaluated for detection of specific free circulating antigen and circulating immune-complexes (CICs) of 8 kDa antigen in the sera of patients with hydatidosis. All (100%) the sera of 30 confirmed positive cases of hydatidosis had detectable levels of antigen in the acid-treated sera. However, 23 (77%) and 26 (87%) sera of 30 confirmed cases had free as well as CICs of 8 kDa antigen in the untreated and in the polyethylene glycol (PEG) precipitated sera, respectively. None of the sera from other patients with parasitic infections or viral hepatitis had any detectable levels of 8 kDa antigen in the untreated, acid-treated or PEG-precipitated serum samples. The investigations, therefore, suggested that the demonstration of circulating antigen employing monospecific antibodies to affinity purified 8 kDa antigen in acid-treated sera is more efficient as compared to detection of free circulating antigen or CICs in the untreated or in the PEG-precipitated sera which could provide a specific immunodiagnostic tool for ongoing hydatid infection.

Leishmania donovani flagellum-specific epitopes mediating host-parasite interactions

Monoclonal antibodies were developed against flagellar components of promastigotes of Leishmania donovani. The monoclonal antibody produced by clone A11 (mAb A11) recognised epitopes in the polypeptides with molecular weights of 86, 66 and weakly 53 kDa. These epitopes were found to be distributed along the flagellum and at the anterior end of promastigotes. The mAb A11 of IgG1 isotype strongly agglutinated the promastigotes of L. donovani. The prior treatment of promastigotes of L. donovani with mAb A11 resulted in a significant (P < 0.001) reduction in the attachment of promastigotes to cultured mouse peritoneal macrophages of line J774G8. The affinity-purified epitopes identified by mAb A11 were recognised by human sera of cases of visceral leishmaniasis. The present study suggest that flagellar-specific epitopes mediate host-parasite interactions and, therefore, the role of these epitopes in the disease process is speculated.

Anti-66 kDa antileishmanial antibodies as specific immunodiagnostic probe for visceral leishmaniasis

A 66 kDa plasma membrane associated molecule of promastigotes of Leishmania donovani (MHOM/IN/1978/UR6) was affinity purified under acidic conditions. Employing purified 66 kDa antigen in micro ELISA, 36 (97.3%) of the 37 patients of visceral leishmaniasis (bone marrow aspirates positive for Leishman Donovan bodies) had detectable levels of anti 66 kDa anti leishmanial antibodies. The sera of the patients confirmed to have visceral leishmaniasis had significantly (P < 0.001) higher optical density values (0.636 +/- 0.230) as compared to sera (OD 0.185 +/- 0.131) from patients clinically suspected to have visceral leishmaniasis (bone marrow aspirates negative for Leishman Donovan bodies). None of the 35 sera from apparently healthy subjects from non endemic area had anti 66 kDa antibodies. However, sera from one (8.3%) of the 12 healthy subjects, who was a first degree relative of a patient of visceral leishmaniasis and residing in an area endemic for visceral leishmaniasis, had anti 66 kDa antibodies. It is felt that detection of anti 66 kDa antibodies in a micro ELISA assay provides a highly sensitive and specific tool for confirming ongoing visceral leishmaniasis.

Inhibition of hepatic extramedullary haemopoiesis by nucleoprotein of heterologous rotavirus strain in infant mice

Infant mice (NMRI strain) showed the inhibition of hepatic extramedullary haemopoiesis by oral inoculation of a 100 ID50 dose of EB rotavirus and nucleoprotein of SA-11 rotavirus (serotype 3). The extramedullary haemopoiesis was observed by oral inoculation of surface protein VP7 of SA-11 rotavirus and in control (placebo administered) mice.

Evaluation of commercially available antacid tablets

Antacids are commonly used for the treatment of acid peptic disease. There is a need to study the relative merits of various brands of antacids available commercially. Twenty three brands of antacid tablet preparations were evaluated with regard to their composition, cost, dispersion time, pH, neutralising capacity and time taken for neutralisation. The cost of various tablets ranged from Rs 0.13 to Rs. 1.48 per tablet and the dispersion time from 20 to 90 minutes. The pH of the dispersed tablet solution ranged from 5.7 to 9.5. The neutralising capacity varied between 8 to 169 meq/tablet and the neutralizing time between 20 and 45 minutes. The cost: neutralizing ratio was calculated and ranged from 102 to 9867 x 10(-3) Rs/meq. A scoring system with a maximum score of 12 has been devised. The study provides a guide for choosing a more potent, quick neutralising and low cost antacid preparation.

Host response to Mycobacterial cell wall subunit during experimental tuberculosis in mice

The cell-wall protein-peptidoglycan complex (CW-PPC) of Mycobacterium tuberculosis, an immunologically potent component, was used to study the correlation between immune response and in vivo bacterial multiplication in the course of experimental tuberculosis infection in mice. Antibodies to CW-PPC were detected only after seven weeks of infection with M. tuberculosis H37Rv and afterwards no significant change was seen throughout the experiment. Delayed type hypersensitivity (DTH) to CW-PPC showed a gradual increase from the fifth week onward with a maximum during the 12th week after infection (p.in.) which did not change significantly afterward. The increased immune response in the course of infection correlated well with the multiplication rate of bacilli in the lungs. These results indicate a role of CW-PPC in antituberculous immunity.

Detection of Entamoeba histolytica antigens in stool in amebiasis

BACKGROUND

Stool microscopy, the conventional method of diagnosing intestinal amebiasis, fails to detect Entamoeba histolytica in more than 30-40% of clinically suspected cases. Demonstration of parasite products in clinical specimens has been suggested as an alternative. However, the usefulness of demonstrating amebic antigen in the stools of clinical cases needs to be assessed.

METHODS

A double-antibody sandwich enzyme linked immunosorbent assay (ELISA) using anti-trophozoite antibodies to capture E histolytica specific coproantigen(s) was carried out on stools obtained from 31 patients with microscopically confirmed non-dysenteric amebic colitis, 18 patients with intestinal parasites other than E histolytica and 41 apparently healthy subjects.

RESULTS

The assay detected E histolytica specific coproantigen(s) in stools of 23 (74.2%) of 31 subjects with non-dysenteric amebic colitis, none of 18 with other parasitic infections and 1 (2.4%) of 41 apparently healthy subjects.

CONCLUSION

Our results provide evidence for the presence of E histolytica specific coproantigen(s) in stool eluates from patients with amebic infection; this finding can be exploited for confirming ongoing amebic infection. However, the sensitivity of the assay needs to be improved by the use of relevant monospecific/monoclonal antibodies.

Evaluation of the direct agglutination test as an immunodiagnostic tool for kala-azar in India

The direct agglutination test (DAT) has been assessed as a diagnostic procedure for visceral leishmaniasis. Fifty-six of 58 sera (96.5%) from confirmed cases of visceral leishmaniasis, whose bone marrow aspirates contained Leishmania donovani amastigotes, had agglutinating antibodies above the cut-off titre of 1:800. None of the sera from healthy control subjects from non-endemic or endemic areas had anti-leishmanial antibodies. Similarly, none of the sera obtained from cases of malaria or tuberculosis had agglutinating antibodies above the cut-off titre. A significant decline in agglutinating antibody titre in 3 cases following antileishmanial chemotherapy appeared to correlate with regression of clinical symptoms and the absence of amastigotes from bone marrow aspirates. One of 3 cases developed post-kala-azar dermal lesions and sera from this subject had an elevated agglutinating antibody titre. It is concluded that the DAT is a sensitive and specific test to confirm visceral leishmaniasis. As the formalin-fixed promastigotes, stained with Coomassie blue, which are used as antigen could be stored at 4 degrees C for 6 months without any loss of ability to detect anti-leishmanial antibodies, the DAT is recommended for use under field conditions.

Isolation & immunochemical characterization of diagnostically relevant antigens of Echinococcus granulosus

Two hydatid specific polypeptides with molecular masses of 8 kDa and 116 kDa have been successfully isolated from E. granulosus hydatid cyst fluid using affinity chromatography. Sodium dodecyl sulphate polyacrylamide gel electrophoresis and western immunoblot analysis under reducing and denaturing conditions indicated the 116 kDa purified antigen to be a hetero-tetramer consisting of 45 kDa, 66 kDa, 75 kDa and 116 kDa subunits linked by disulphide bonds while the 8 kDa purified antigen was found to be a monomer polypeptide. Affinity purified 116 kDa molecule was heat-labile, sensitive to treatment with pronase, trypsin and pepsin and its immunoreactivity as assessed in enzyme linked immunosorbent assay remained unaltered on treatment with sodium metaperiodate. The affinity purified 8 kDa molecule was heat-stable, sensitive to proteolytic enzymes and also sodium metaperiodate oxidation. Lectin binding studies revealed that the 8 kDa molecule specifically bound Concanavalin A and Triticum vulgaris, and thus had varies; is directly proportional to-D-glucose and N-acetyl D-glucosamine sugar moieties. The immunoreactivity of both the antigens remained unaltered on treatment with lipase. However, biochemical estimation of total lipid content revealed the affinity purified 116 kDa antigen to contain 6.25 per cent total lipids suggesting it to be lipoproteinic in nature. The 8 kDa antigen had no detectable total lipids biochemically. All sera from patients confirmed to have hydatidosis recognised the 8 kDa and 116 kDa polypeptides. However, sera from seven subjects with other parasitic infections also recognised the 116 kDa antigen though not the 8 kDa antigen. The data suggested that the recognition of 8 kDa antigen of E. granulosus has potential for specific immunodiagnosis of hydatidosis.

Uses and limitations of monoclonal antibodies to Giardia lamblia-specific 66-kDa copro-antigen in copro-immunodiagnosis of giardiasis

Antigen-capture enzyme-linked immunosorbent assay for the detection of Giardia lamblia-specific antigen in stool eluates from clinical subjects employing monoclonal antibody directed at 66-kDa G. lamblia copro-antigen has been evaluated. The G. lamblia copro-antigen was detected in 67% (31 of the 46 cases) of stool eluates from clinical cases, while none of the stool eluates from subjects with other intestinal parasites or from apparently healthy individuals, had detectable levels of G. lamblia copro-antigen. Monoclonal antibodies secreted by clones B4C5 and D3F4 recognised the periodate-sensitive and -insensitive epitopes of 66-kDa G. lamblia specific copro-antigen, respectively. Eight (73%) of the 11 symptomatic cases of giardiasis had trypsin-/periodate-sensitive epitopes of 66-kDa copro-antigen while 9 (92%) of 11 of the symptomatic cases and asymptomatic G. lamblia cyst carriers had trypsin-sensitive periodate-insensitive G. lamblia specific copro-antigen. The data tend to suggest that detection of periodate-insensitive epitopes of G. lamblia copro-antigen would indicate the presence of the parasite while the detection of periodate sensitive epitopes of G. lamblia copro-antigen would suggest symptomatic active giardial infection.

The significance of free and immune-complexed hydatid-specific antigen(s) as an immunodiagnostic tool for human hydatidosis

Micro-enzyme-linked immunosorbent assay (Micro-ELISA) systems were developed and evaluated for the detection of circulating (free or immune-complexed) hydatid antigens in the sera of patients with hydatidosis, by employing monospecific antibodies to hydatid-specific antigens of 8-kDa and 116-kDa. Fifteen (75%) of 20 sera from patients with hydatidosis had both 8-kDa and 116-kDa antigens freely circulating in their sera while three and two samples, respectively, had only 8-kDa or 116-kDa antigen. All the surgically confirmed cases of hydatidosis had detectable levels of both 8-kDa and 116-kDa circulating immune complexes in glycine HCl-treated sera. However, none of the sera from control subjects (patients with cysticercosis, ascariasis, ancylostomiasis, hymenolepiasis, amoebic liver abscess or viral hepatitis) had any detectable level of either type of circulating specific antigen. These results suggest that the demonstration of either 8- or 116-kDa antigen(s) in free or immune-complex form could confirm the diagnosis of hydatidosis.

Protective efficacy of different cell-wall fractions of Mycobacterium tuberculosis

Immunization with various cell-wall fractions of M. tuberculosis H37Ra, progressively depleted of lipids (cell-wall-insoluble fraction; CWIF), soluble proteins (cell-wall core; CWC), mycolic acids and arabinogalactans (cell-wall-protein-peptidoglycan complex; CW-PPC) elicited significant levels of both humoral and cell-mediated immune response. Mice immunized with these fractions, when challenged with an LD50 dose of M. tuberculosis H37Rv, exhibited significant protection as revealed by high survival rates and decreased bacterial load in lungs, liver and spleen, as compared to nonimmunized animals.

Acid phosphatase activity of promastigotes of Leishmania donovani: a marker of virulence

Seven cloned lines of promastigotes of Leishmania donovani (UR 6) were isolated by limiting dilution. One clone, UR6-C25, failed to multiply inside the macrophages of line J774G8 and thus was labelled as avirulent. Another, UR6-C24, multiplied inside macrophages, had a virulence index as high as 93 +/- 9.8 and was thus labelled as highly virulent. The other five clones had variable degree of virulence indices ranging from 46.4 +/- 5.8 to 67.6 +/- 3.5. No significant difference in the degrees of attachment of virulent and avirulent populations of promastigotes to macrophages was observed, suggesting no difference in the ligand utilised by these populations for attachment to the macrophages. Acid phosphatase activity of cloned promastigotes correlated with the degree of virulence. These data suggest that acid phosphatase activity could be used as a marker to differentiate avirulent from virulent populations of promastigotes of L. donovani.

Evaluation of antacid gel preparations available commercially in the Indian market

A scoring system based on the neutralising capacity, cost efficiency and time of buffering of twenty four commercially available antacid gels was analysed. A gel scoring eight out of the ten points was considered as the best antacid. The study provides a practical guide in choosing a quick neutralizing and low cost antacid gel.

Variations in isoenzymes of cloned & uncloned axenic Entamoeba histolytica without bacterial association

Five clones of axenic E. histolytica (HMI) grown as discrete colonies in semisolid agar medium were adapted in liquid medium and labelled as HMI-C121, HMI-C131, HMI-C143, HMI-C144 and HMI-C145. Isoenzymes of these 5 clones of E. histolytica (HMI) were investigated in starch gel electrophoresis. There were no differences in the electromobility of maleate NADP oxidoreductase and glucosephosphoisomerase amongst the five clones and uncloned cultures of axenic E. histolytica. The relative electromobility (rf) of a single phosphoglucomutase (PGM) band of uncloned Mexican E. histolytica (HMI) and Indian axenic E. histolytica (KCG: 0986: 11) cultures and cloned E. histolytica HMI-C121, HMI-C145 was 0.087 while a single PGM band of uncloned E. histolytica (NIH: 200) and cloned E. histolytica HMI-C131, HMI-C143 and HMI-C144 cultures had rf of 0.075. Isoenzyme characterization of four cloned HMI-C121, HMI-C131, HMI-C143, HMI-C144 cultures of axenic E. histolytica (HMI) revealed existence of three bands of hexokinase (HK). The additional third band of HK was located close to the place of application of lysate and had rf ranging from 0.11-0.14. The data indicated that parent axenic E. histolytica (HMI) consisted of several populations and each population expressed different isoenzyme pattern without an association of amoebic cultures with any bacterial species.

Immunochemical characterisation of a 29-Kda surface-associated molecule of Entamoeba histolytica and its recognition by serum from patients with amoebiasis

A 29-Kda cytotoxic molecule of axenically-grown pathogenic Entamoeba histolytica (strain HM1) was purified from an amoebic extract by immuno-affinity chromatography with monoclonal antibodies. Immunoreactivity of the purified 29-Kda molecule altered significantly (p less than 0.01) after exposure to heat or trypsin, but remained unaltered after treatment with sodium metaperiodate. The 29-Kda molecule was recognised by serum from each of 13 patients with amoebic liver abscess. In an ELISA system, the molecule produced significantly higher (p less than 0.01) OD readings with these serum samples than with samples from asymptomatic cyst passers. No serum from healthy subjects or from patients with idiopathic ulcerative colitis or giardiasis had antibodies that reacted with the 29-Kda molecule. The immune response to the 29-Kda amoebic protein in man may indicate a specific role for this molecule in invasive amoebiasis.

Specific antibodies in serum of patients with hydatidosis recognised by immunoblotting

Hydatid fluids from sheep, goat, pig and man, after resolution by sodium dodecyl sulphate-polyacrylamide gel electrophoresis under reducing conditions, revealed at least 15 discrete polypeptide bands of 8-116 Kda. By ELISA, sera from all 20 cases of hydatidosis showed anti-hydatid antibody, but so did 11 (73%) of 15 sera samples from cysticercosis patients, eight (67%) of 12 sera from patients with other parasitic infections (amoebic liver abscess or hymenolepiasis) and one (4%) of 25 sera from healthy controls. Antibody to cysticercus antigen was found in 14 (93%) of 15 sera from cysticercosis patients, 17 (85%) of 20 sera from hydatid patients, six (50%) of 12 sera from patients with other parasitic infections and one (4%) of 25 sera from healthy controls. Sera from 17 (85%) of 20 hydatid patients, 11 (73%) of 15 cysticercosis patients and five (42%) of 12 patients with other parasitic infections had antibodies to both hydatid and cysticercus antigens. Sera from 20 surgically confirmed cases of hydatidosis reacted with 12 polypeptides of 8-116 Kda in Western immunoblot with hydatid antigens. Polypeptides of 16, 24, 38, 45 and 58 Kda were recognised by all hydatidosis sera but also by many sera from patients with other infections. However, polypeptides of 8 and 116 Kda were recognised by all hydatidosis sera but not by any sera from patients with cysticercosis, other parasitic infections or viral hepatitis, or from healthy controls. Thus, recognition of 8- and 116-Kda hydatid antigens by a patient's serum appears to be a specific test confirming a clinical diagnosis in an individual case of hydatidosis.

Systemic-oral immunization with 56 kDa molecule of Giardia lamblia affords protection in experimental mice

Prior systemic-oral immunization of inbred mice with Giardia lamblia surface-associated antigen of molecular mass 56 kDa not only significantly blocked colonization but also resulted in elimination of G. lamblia trophozoites by 9-11 days following challenge. The colonization and multiplication of the trophozoites in unprotected animals were accompanied by a pronounced influx of suppressor T cells in intraepithelial or lamina propria of the small intestine and a significant decline in IgA-bearing plasma cells in the lamina propria. An induction of helper/inducer T cells in the intraepithelial and lamina propria and significant enhancement of IgA and IgG-bearing cells in the lamina propria of the small gut resulted in a decline, and eventual elimination, of the trophozoites from the gut. The completion of the immunization of animals with 56 kDa G. lamblia antigen resulted in: significant enhancement of helper/inducer T lymphocytes with no effect on suppressor T cells in the intraepithelial and lamina propria of the small gut; significant enhancement of IgA- and IgG-bearing plasma cells in lamina propria; and significant elevation of antibodies to 56 kDa G. lamblia antigen in the systemic circulation. The stimulation of such effector mechanisms in 56 kDa-immunized animals appears to result in failure of the trophozoites to get established, prevention of multiplication and earlier elimination from the gut. The data suggest that the 56 kDa molecule of G. lamblia immunoregulates the giardial infection.

Dietary modulation of malaria infection in rats

Feeding of wistar albino rats on low protein and energy diet (4% protein) caused suppression of parasitaemia when infected with Plasmodium berghei besides causing a depressed immune response. The refeeding of protein energy deficient rats on normal protein and energy diet (18% protein) for four weeks resulted in the normal course of parasitaemia after P. berghei infection. The present study was carried out to find the cause of suppression of malaria in protein energy deficient rats. The experiments revealed re-elevation of malaria parasitaemia when rats were fed on low protein diets supplemented with p-amino-benzoic acid (PABA). Moreover, the parasite persisted at subpatent levels in tissues in protein energy deficient rats and resulted in the development of antimalarial antibodies. Low protein energy diet could cause deficiency of certain essential nutrients required for the parasite, PABA being one of them, and hence suppresses the parasitaemia to subpatent levels. As a result, sufficient antigenic stimulus is provided to the host so that the host develops an immune response which might in turn help in further suppression of parasitaemia to subpatent levels.

Alterations in enzymatic activities of the intestinal mucosa during the course of Giardia lamblia infection in mice

Decline in the specific activities of intestinal cytosolic glucose-6-phosphate dehydrogenase (G6PD) and isocitrate dehydrogenase (ICDH); brush border glucoamylase, and isomaltase; and basolateral (Na+, K+)-ATPase activities were observed during the establishment, acute phase and decline phase of infection in Giardia lamblia-infected mice. The degree of decline in the activities of various enzymes correlated well with the number of trophozoites counted in the jejunum. There appeared to be a gradual recovery of enzymatic activities during the decline phase of infection, when the number of trophozoites also declined. The decline in activities of these enzymes may contribute to malabsorption of nutrients during giardiasis.

Monoclonal antibodies which inhibit in vitro cytotoxicity of axenic Entamoeba histolytica

A panel of 12 independent hybridoma cell lines secreting monoclonal antibodies to axenic E. histolytica (HM1) have been developed. A hybridoma cell line P4 C4 P2 F8 C8 (clone C8) produced monoclonal antibodies (MoAb C8) of IgG1 isotype which recognised a 29 KD surface associated antigen of amoebic trophozoites in Western immunoblot. Immunofluorescent probing with MoAb C8 employing live and acetone fixed amoebic trophozoites indicated 29 KD molecule on the surface plasma membrane of E. histolytica trophozoites. The MoAb C8 also agglutinated the live amoebic trophozoites. Pretreatment of amoebic trophozoites with anti 29 KD monoclonal antibody significantly (P less than 0.01) inhibited in vitro cytotoxicity of amoebic trophozoites to the cultured baby hamster kidney (BHK-21) cells. MoAb recognised a 29 KD molecule of E. histolytica trophozoites which mediated cytotoxic potentials of the parasite. The absence or variable degree of expression of cytotoxic 29 KD molecule may possibly serve as a marker to differentiate virulent/avirulent populations or strains of E. histolytica.

Cytopathogenicity of Entamoeba histolytica to human intestinal epithelial cells: inhibition by monoclonal antibodies and sera from amoebic patients

Interactions of pathogenic Entamoeba histolytica (HM 1) with human intestinal epithelial cells (Henle-407) were investigated. The E. histolytica trophozoites adhered and cytolysed 87% of cultured epithelial cell monolayers. A significant (P less than 0.001) inhibition of cytopathic effect of amoebic trophozoites pretreated with monoclonal antibodies to a 29 kDa surface associated protein suggested utilization of the 29 kDa surface protein in recognition and cytolysis of epithelial target cells. The polyclonal sera from treated patients of amoebic liver abscess and anti-amoebic hyperimmune serum inhibited cytopathogenicity to a greater degree (P less than 0.001) than did the monoclonal antibodies. The data thus suggest involvement of several amoebic molecules in exercising cytopathogenicity to epithelial cells.

A comparative efficacy of plate ELISA and dot ELISA to detect antiamoebic antibodies in clinical patients

The dot enzyme-linked immunosorbent assay (dot ELISA) has been developed and compared with plate ELISA for detecting antiamoebic antibodies in serum samples from amoebic patients and healthy controls. Both dot and plate ELISA detected antiamoebic antibodies in all 17 confirmed amoebic liver abscess cases and 15 (68%) of 22 suspected amoebic liver abscess cases while none of 21 non-amoebic hepatic disorders, 25 non-amoebic intestinal disorders and 28 apparently healthy subjects had antiamoebic antibodies as assessed by either of the tests. All the 15 suspected amoebic liver abscess patients who had antiamoebic antibodies responded favourably to antiamoebic treatment. As the dot ELISA is simpler, rapid, inexpensive, equally sensitive and specific as compared to plate ELISA, its use in detecting antiamoebic antibodies is recommended especially under field conditions.

Isolation of the 66-kilodalton polypeptide from promastigotes of Leishmania donovani as a ligand molecule for binding to macrophages

A 66-kDa major plasma membrane-associated molecule of promastigotes of Leishmania donovani (UR6) was purified by affinity chromatography. The immunoreactivity of the 66-kDa molecule was lost upon exposure to heat or treatment with trypsin. The metaperiodate oxidation significantly reduced its immunoreactivity. The 66-kDa molecule is, therefore, glycoprotein in nature. With a fluorescent probe, the 66-kDa molecule was found to be located on the tip of flagellum and on the kinetoplast. The exposure of promastigotes of L. donovani to monospecific anti-66-kDa antibodies significantly reduced the percentage of macrophages with attached promastigotes in the cultured cell line (J774G8). The data suggested that promastigotes of L. donovani utilize the 66-kDa molecule in recognizing and as ligand for binding to macrophages.

Enzyme-linked immunosorbent assay for copro-diagnosis of giardiasis and characterisation of a specific Giardia lamblia antigen in stools

An enzyme-linked immunosorbent assay (ELISA) has been evaluated for copro-diagnosis of giardiasis with anti-trophozoite antibody to capture specific Giardia lamblia stool antigen (GLSA), which was then detected by specific antibody conjugated with horseradish peroxidase. GLSA was demonstrated in stool eluates from all the 24 confirmed cases of giardiasis. None of the stool eluates from apparently healthy subjects or from patients carrying intestinal parasites other than G. lamblia had GLSA. Of the 25 microscopy-negative clinically suspected cases of giardiasis, 17 (68%) patients had GLSA in their stool eluates; these patients responded to anti-giardial therapy. The specific antigen was isolated and affinity-purified by the use of specific antibody; it had a Mr of 66 Kda, and its immunoreactivity was lost after treatment with heat or trypsin but unaltered by metaperiodate. ELISA seems to be a sensitive and specific method for copro-diagnosis of giardiasis, especially in highly suspected cases.

Kinetics of intraepithelium and lamina propria lymphocyte responses during Giardia lamblia infection in mice

The responses of intestinal T-cell subsets and immunoglobulin containing cells were assessed during the course of experimental Giardia lamblia infection in inbred NMRI mice. Quantitation of T-cell subsets in intraepithelium (IEL) and lamina propria (LPL) revealed increased influx of Lyt 2.2+ (suppressor/cytotoxic) T cells and Thy 1.2+ T cells during the establishment (3-5 days post-inoculation) and peak (9-11 days post-inoculation) phases of infection. The influx of these cells reduced as the parasite load declined. In contrast, no significant change was noticed in lamina propria and intraepithelial L3 T4+ (helper/inducer) T cells during the establishment or acute phases. However, these cells increased significantly in the decline phase (17-21 days post-inoculation) of infection. The lamina propria IgA-containing cells significantly declined during the establishment and acute phases of infection, and increased significantly as the parasite load in the jejunum declined. Helper/inducer ratios of 0.4 for IEL and 2.0 for LPL accompanied the decline of G. lamblia trophozoites in the gut. Our data thus suggest that induction of helper/inducer T cells during the decline phase of infection concomitant with an increase in lamina propria IgA-containing cells resulted in elimination of G. lamblia trophozoites from the gut.

Variations in cytotoxicity and isoenzyme patterns of uncloned and cloned cultures of axenic Entamoeba histolytica

Five clones of axenic Entamoeba histolytica (HMI) grown as discrete colonies in semisolid agar medium were adapted in liquid medium and labelled as HMI-C121, HMI-C131, HMI-C143, HMI-C144 and HMI-C145. The clone HMI-C121 was more cytotoxic to the cultured Baby Hamster Kidney (BHK) cells while all other clones were significantly (P less than 0.001) less cytotoxic as compared to the cloned HMI-C121 and uncloned E. histolytica (HMI). The uncloned Indian axenic E. histolytica (KCG:0986:11) as well as E. histolytica (NIH:200) cultures were significantly (P less than 0.001) less cytotoxic to cultured BHK cells. No difference in the electromobility of maleate NADP oxidoreductase (ME) or glucophosphate isomerase (GPI) isoenzyme in the lysates of all the cloned and uncloned cultures of E. histolytica was observed. The clones HMI-C121, HMI-C131, HMI-G143 and HMI-C144 had three bands of hexokinase (HK) while all uncloned cultures and one of clones, HMI-C145 had only two bands. Though cloned and uncloned cultures had a single PGM band, the relative electromobility (rf) of phosphoglucomutase (PGM) for clone HMI-C131, HMI-C143 HMI-C144 was relatively less (rf 0.075) and these were also significantly (P less than 0.001) less cytotoxic to BHK cells as compared to clone HMI-C121. It is felt that axenic E. histolytica culture consists of several populations (clones) and expression of isoenzymes pattern or cytotoxic potentials would depend upon the population which predominantly multiples and outgrows other populations in the culture system.

An immunoenzymatic dot-ELISA for the detection of Giardia lamblia antigen in stool eluates of clinical cases of giardiasis

A dot-ELISA technique for the detection of G. lamblia specific antigen in stool eluates of clinical cases of giardiasis was developed and evaluated employing monospecific antibodies to a G. lamblia specific coproantigen with a molecular mass of 66 kDa. The assay detected 22 (91.7%) of the 24 microscopically confirmed cases of giardiasis while none of the stool eluates from 20 patients with gastrointestinal parasites other than G. lamblia and 20 apparently healthy subjects had any detectable levels of G. lamblia-specific coproantigen. Of the 25 stool eluates from clinically suspected cases of giardiasis, 13 (52%) were found to contain G. lamblia-specific coproantigen. A 3-month-follow up of five of such cases where stool eluates has antigen detected by dot-ELISA assay, revealed the presence of G. lamblia cysts on repeated stool examinations. All the clinically suspected cases with detectable levels of G. lamblia-specific coproantigen by dot-ELISA were relieved of their clinical symptoms following metronidazole therapy. Single stool eluate examination by dot-ELISA was found to be sufficient to confirm the diagnosis. The dot-ELISA is an easy, rapid, sensitive and specific procedure for confirming the diagnosis of suspected cases of giardiasis. It should be a valuable diagnostic aid under field conditions as well as in the laboratory.

Characterization of surface associated antigens of axenic Giardia lamblia trophozoites & their recognition by human sera

Two surface associated antigens (GLSA-82 and GLSA-56) of axenically grown G. lamblia trophozoites (PI strain) were affinity purified from its sonic extract. Both GLSA-82 and GLSA-56 were heat labile, sensitive to treatment with pronase, trypsin and were also sodium metaperiodate modifiable as assessed by micro ELISA. Lectin binding studies revealed that GLSA-82 specifically bound concanavalin A and pokeweed mitogen, and had alpha-methyl mannoside and n-acetyl-B-d-glucosamine sugar moieties. However, GLSA-56 selectively bound Ricinus communis agglutinin and phytohaemagglutinin, and had B-d-galactose and n-acetyl-B-d-galastosamine as sugar moieties. Human sera obtained during acute G. lamblia infection recognised GLSA-82 and GLSA-56 antigens. However, the antibody levels to GLSA-82 were significantly lower (P less than 0.05) during active giardiasis infection. Such surface associated antigens may be target of antiparasitic immune responses and thus, may modulate disease processes.

Immunoreactivity of Entamoeba histolytica antigens with sera from amoebic patients

Immune sera from 15 patients with cured amoebic liver abscess were used to recognise the antigens of Entamoeba histolytica (HMI) by immunoblotting. The amoebic proteins most frequently recognised by sera from patients with cured amoebic liver abscess had molecular masses of 8, 13, 18, 22, 29, 38, 45, 67 and 94 kDa. Six plasma membrane-associated amoebic proteins of molecular mass 29, 38, 45-67 complex, 85 and 94 kDa were strongly recognised by such sera. Two plasma membrane-associated antigens of 108 and 129 kDa were not recognised by any sera. None of the crude or plasma membrane-associated antigens were recognised by sera from five patients of idiopathic ulcerative colitis, five patients of persistent giardiasis and five normal healthy subjects. Identification of such antigens, especially plasma membrane-associated antigens may pave a way to develop specific diagnostic and immunoprotective agents.

Evaluation of ELISA for detection of Giardia lamblia-specific copro-antigen employing monospecific antibodies

An enzyme linked immunosorbent assay (ELISA) system, using monospecific antibodies for the detection of Giardia lamblia specific 66 kDa copro-antigen has been developed and evaluated. The assay detected the antigen in stool eluates of all the 24 microscopically confirmed cases of giardiasis and in 17 (68%) of the 25 microscopy-negative clinically suspected cases of giardiasis. None of stool eluates from 20 subjects infected with other protozoal/helminthic intestinal parasites or from 20 apparently healthy subjects had G. lamblia-specific copro-antigen. The ELISA employing monospecific antibodies is a sensitive and specific tool for the diagnosis of giardiasis and is especially useful for confirming microscopy-negative suspected cases of giardiasis.

Recognition of 29 kDa surface-associated adhesive molecule of Entamoeba histolytica by monoclonal antibodies

Monoclonal antibodies have been developed and used as specific probe to locate and identify a 29-kDa molecule of axenic Entamoeba histolytica trophozoites. Monoclonal antibody produced by clone C8 (MoAb C8) strongly agglutinated the amoebic trophozoites. The immunofluorescence of live E. histolytica trophozoites and surface fluorescence of acetone-fixed trophozoites by MoAb C8 indicated existence of a 29-kDa molecule on surface-associated plasma membrane of E. histolytica. The monoclonal antibody belonged to IgG1 isotype. The prior treatment of E. histolytica trophozoites with MoAb C8 resulted in significant (P less than 0.01) reduction in adherence of amoebic trophozoites to cultured Chinese Hamster Ovary cells and significant (P less than 0.01) reduction in cytotoxicity to cultured Baby Hamster Kidney cells. Pretreatment of amoebic trophozoites with MoAb C8 prior to cultivation in TPS-1 medium resulted in significant (P less than 0.01) reduction in growth of the parasite. Thus, the data suggested that the surface-exposed 29-kDa molecule may be one of the receptors involved in E. histolytica host cell interactions and may possibly modulate amoebic disease processes.

An ultrastructural analysis of changes in surface architecture of intestinal mucosa following Giardia lamblia infection in mice

The oral inoculation of Giardia lamblia trophozoites (Portland 1 strain) resulted in the establishment of infection by day 3-5 in NMRI mice. By 9-11 days postinfection, the trophozoites load reached maximum (acute phase) and later declined by day 17-21. The tissue sections from infected animals during the establishment phase of infection indicated limited changes in surface epithelium with normal villous length. Although trophozoites of G. lamblia were seen in all sections lying free in the lumen as discrete parasite, the active invasion by the parasite could not be demonstrated. During the acute phase of infection, fuzzy appearance of brush border, marked reduction in villous height and infiltration of intraepithelial lymphocytes were commonly seen in all tissues. Electron microscopic observation demonstrated large numbers of trophozoites of G. lamblia preferentially aggregated at the base of the villi. At some sites, adhesive marks indicating attachment of Giardia trophozoites were also seen by scanning electron microscopy. In addition, severe flattening and blunting of microvilli and occasional loss of basic morphology of intracellular organelles of columnar cells were noticed at the site of parasite colonization under electron microscopy. The brush border microvilli were noted to be damaged in areas where parasites were attached to surface epithelium with the help of suction discs. The morphological changes associated with Giardia infection tended to reverse as the parasite load declined by day 17-21. Thus we feel that malabsorption in giardiasis with total or varying degrees of morphological alterations of surface mucosa can be explained on the basis of reduced absorptive surface area.

Gut-associated immune effector responses in immunocompetent and immunocompromised mice with Giardia lamblia

Significantly higher Giardia lamblia trophozoites load in the intestine of infected mice accompanied pronounced influx of suppressor/cytotoxic T cells (Lyt 2.2+), T cells (Thy 1.2+) and significant reduction in IgA-containing cells in the gut during the establishment and peak phases of infection. The induction of helper/inducer T cells (Lyt 1.1+) and significant enhancement of IgA-containing cells in gut resulted in the decline of the trophozoite loads. However, the prior treatment of animals with dexamethasone alone resulted in significant reduction in helper/inducer T cells (Lyt 1.1+) and the IgA-containing cells in the gut; the percents of suppressor/cytotoxic T cells (Lyt 2.2+) and IgM-containing cells remained unaltered. Although the G. lamblia infection in such animals further significantly increased the influx of suppressor/cytotoxic T cells, the late response of helper/inducer T cells and IgA-containing cells was abrogated during the decline phase of infection. The significant reduction in the trophozoite load - despite immuno-suppressive therapy - appeared to be due to unaltered IgM response in such animals which probably took over the function of IgA in defense against G. lamblia. The data of the investigation thus suggested a role of helper/inducer T cells and antibodies producing cells in gut as important effector cells resulting in the termination of primary G. lamblia infection.

Prevention of malaria-induced foetal abnormalities following immunization of mice with Plasmodium berghei merozoite antigen

Pre-pregnancy immunization of Swiss albino mice with merozoite antigen of P. berghei entrapped in multilamellar phosphatidyl choline liposomes resulted in (i) increased prepatent period, (ii) either no or low parasitaemic levels, (iii) reduced mortality, and (iv) normal foetal and placental development, upon challenge with P. berghei on 13th gestational day. The unimmunized animals which received either phosphate buffered saline or empty multilamellar phosphatidyl choline liposomes before pregnancy developed high parasitaemic and 30-40 per cent animals died before parturition while 60-70 per cent unimmunized animals revealed foetal abnormalities such as low body weight and larger spleen size. Placentae of unprotected animals had hyperplasia of trophoblastic membrane and plugging of placental sinusoids with parasitized erythrocytes and malarial pigments. The data suggest that prior immunization of animals with merozoite antigen entrapped in multilamellar phosphatidyl choline liposomes could abrogate the ill effects induced by malaria infection under the stress of pregnancy.

Uses and limitations in the demonstration of specific circulating immune complexes in patients with amoebiasis

A micro-enzyme linked immunosorbent assay (micro-ELISA) has been evaluated as a diagnostic test to detect amoebic antigen in polyethylene glycol (PEG) precipitated circulating immune complexes (CIC) in sera from patients with amoebiasis. The immune complexes were captured on rabbit anti-amoebic IgG-coated wells of microtitration plates and the complexed antigen was detected by enzyme linked antihuman immunoglobulins. A titre of greater than 160 for the immune complexes was considered to be of clinical significance. The immunoassay detected amoebic, antigen-specific CIC in 35 (94.5%) of 37 patients with confirmed amoebic liver abscess. Twenty (55.5%) of 36 clinically suspected cases of amoebic liver abscess had amoebic antigen-specific CIC and responded favourably to anti-amoebic chemotherapy. Only two (20%) of 10 cases of non-dysenteric symptomatic intestinal amoebic infection had amoebic antigen-specific CIC. One (10%) of 10 patients with non-amoebic intestinal disorders also had amoebic antigen in CIC. However, none of 15 cases of non-amoebic hepatic disorders that included hydatid disease, metastatic adenocarcinoma, hepatocellular carcinoma, cholecystitis and choledocal cyst, 13 cases of rheumatoid arthritis and 25 apparently healthy subjects had amoebic antigen in CIC. The levels of the amoebic antigen-specific CIC did not correlate (p greater than 0.05) with either the number of abscess(es) or lobe(s) of the liver involved. However, the levels of antigen-specific CIC were higher (p less than 0.01) in patients with a liver size of more than 5 cm below the right costal margin. Antigen-specific CIC levels tended to decline or disappear during 3-6 months following completion of therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunobiological studies with mycobacterial ribonucleic acid-protein complex: Part I--Immune responses and protective role against experimental tuberculosis

Ribonucleic acid (RNA) isolated from M. tuberculosis H37Ra was found to be native in nature as determined by hyperchromicity studies using ribonuclease. Mycobacterial RNA-protein (Myc. RNA-P) when injected as RNA-P-FIA complexes induced weak humoral immune responses and strong cell-mediated immune (CMI) responses which were directed against Myc. RNA. Protection comparable to BCG was induced in mice immunized with RNA-FIA complexes against LD50 dose of M. tuberculosis as monitored by increased survival rates, decreased lung density, root specific lung weight (RSLW) and by decreased viable counts of M. tuberculosis in lung, liver and spleen of immunized mice. Enzymatic degradation studies revealed Myc. RNA component to specifically mediate protection while the protein component was found ineffective.

Immunobiological studies with mycobacterial ribonucleic acid-protein complex: Part II--Mechanism of protective immunity against experimental tuberculosis

Passive transfer of protective antituberculous immunity against LD50 dose of M. tuberculosis H37Rv was found to be mainly mediated by immune T-cells harvested from spleens of donor mice immunized with Myc. RNA-P-FIA complexes as monitored by indices of percent survival, root specific lung weight, lung density and by bacterial enumeration from different organs. Treatment of immune T-cells with anti-Thy 1.2. monoclonal antibodies plus complement prior to passive transfer, completely abrogated its protective effect thereby confirming their protective nature. Passive transfer of immune sera as well as immune T + B cells did not induce any enhancement in protective immunity.