Isolation of integral membrane proteins of Leishmania promastigotes and evaluation of their prophylactic potential in hamsters against experimental visceral leishmaniasis

The integral membrane proteins (IMP's) of promastigotes of two virulent strain of Leishmania (L.) donovani Dd8 and Leishmania (L.) infantum LV9 and one avirulent viscerotropic strain Leishmania tropica UR6 were extracted by phase separation technique using a non-ionic detergent "Triton X-114". This detergent is homogeneous at 0 degrees C but divides in an aqueous phase and a detergent phase at above 20 degrees C. The phase partition resulted in solubilisation of hydrophilic proteins in aqueous phase, and IMP's with an amphiphilic nature were recovered in the detergent phase. The strain wise quantitative recovery rates of IMP's were estimated. These proteins were purified by chill methanol centrifugation and used as vaccinogen, alone or in combination with adjuvant against L. donovani challenge in hamster model. Among all the combinations, hamsters immunised with IMP of L. donovani (Dd8) in combination with CFA resulted in 75% parasite inhibition in spleen (P <0.001), however, 61.14% (P <0.001) and 77.60% (P <0.001) parasitic inhibition was achieved in liver and bone marrow respectively as compared to their unvaccinated counter part. Similar combinations with UR6 and LV9 strain inhibited the parasite establishment up to 65.12% (P <0.001) and 66.87% (P <0.001), respectively on splenic site. The specific IgG level against (Dd8 strain) soluble leishmania promastigote antigen was monitored at different stages by enzyme linked immunosorbent assay (ELISA) corresponds to the level of parasitic establishment. Similar observations were made in cases of LV9 and UR6 strains. However, significant lymphoproliferative response to IMPs of Dd8 strain (SI 3.5-4.9, P <0.001) was noticed in all IMP + CFA vaccinated animals. Thus, this study will provide a lead for more manipulative trials to develop a subunit vaccine against the fatal disease.

Role of 14-bp deletion in theHLA-Ggene in the maintenance of pregnancy

Differential expression of human leukocyte antigens (HLAs) on trophoblast has been the focus of many studies, specially on extravillous cytotrophoblast cells, which migrates into the maternal uterine tissues. These invading cells do not express classical major histocompatibility complex class I (-A and -B) and class II molecules, along with low expression of HLA-C. HLA-G is the predominantly expressed antigen along with HLA-E. Hence, it is believed that expressed antigens may be involved in materno-fetal tolerance. In the present study, we have studied 14-bp deletion polymorphism in the exon-8 of the non-classical HLA-G antigen. There was no difference in the frequency of deletion/insertion polymorphism in fertile normal women and recurrent spontaneous abortion (RSA) women. However, the number of heterozygotes (-14b/+14b) were increased in RSA women. The probable mechanism for the increase of heterozygotes in recurrent fetal loss is discussed in light of soluble HLA-G.

Role of cysteine proteinase of Entamoeba histolytica in target cell death

The bacterial flora of the intestine plays an important role in the virulence caused by Entamoeba histolytica. Cysteine proteinase (CP), an amoebic virulence factor, plays a major role in host cell destruction. The mechanism of increased virulence following bacterial co-association is not understood. We studied CP of E. histolytica HM1:IMSS which was co-associated with Escherichia coli K12 strain pre-incubated with GalNAc or CP specific inhibitor E 64. Co-association of E. histolytica with bacteria enhanced CP activity 3-6-fold as assessed by azocasein assay and substrate gel electrophoresis showed bands at molecular weights of 28, 35 and 56 kDa. Northern and Western blot analysis showed increase in ehcp2 and ehcp5 gene expression. Trophozoites co-associated with E. coli showed greater cytotoxicity of BHK cells by a 51Cr release assay than trophozoites that had not been co-associated; this enhancement was abolished by E-64 treatment. The killing of BHK 21 targets by E. histolytica was characterized by DNA laddering which was not inhibited with E-64. GalNAc pre-incubation of trophozoites reduced cytotoxicity and DNA laddering, while E. coli co-associated E. histolytica showed smearing with faint laddering of BHK implicating both necrosis and apoptosis. Hence, bacterial co-association increases CP activity and CP gene expression and contributes to the necrosis of the target cell.

Immune responses in normal Indian langur monkeys (Presbytis entellus)--a primate model for visceral leishmaniasis

The Indian langur monkey (Presbytis entellus) is an experimental host for a range of human diseases and for the assessment of vaccine candidate antigens to some common parasitic infections. This experimental host is particularly suitable for the follow-up of immunological responses. To understand some of the mechanism that underlies the defense against experimental pathogens there is a need of the basic knowledge on antibody and cell mediated immune responses. In the present study 25 naïve monkeys were subjected to for assessment of their antibody responses to various human parasitic antigens as well as mitogen induced cellular responses. Only few monkeys were found to have low titer of antiparasitic antibodies. There was compressive dose dependent proliferative response of peripheral blood mononuclear cells. Unlike humans, the blastogenic as well as cytokine responses (IFN-gamma, IL-2 and IL-4) to Con A was considerably higher as compared to PHA. These findings are similar to what have been reported in other non-human primates, confirming the appropriateness of Indian langurs for pre-clinical trials.

A serological study of intrafamilial spread from patients with sporadic hepatitis E virus infection

Intrafamilial transmission is rare in epidemic hepatitis E; its frequency in sporadic hepatitis E is not known. We followed up 86 household contacts (age range 4-75 years, mean +/- SD 32.4 +/- 15.8; 49 males), who were family members of patients with acute sporadic hepatitis E. Of the 86 contacts, 68 (79%) tested negative for IgG anti-hepatitis E virus antibodies. Four (4.7%) had IgM anti-hepatitis E virus antibodies at the time of diagnosis of hepatitis E in the index case; two of these contacts possibly had hepatitis E virus infection acquired simultaneously with that in the index case, and two could have had intrafamilial transmission. None developed serological evidence of hepatitis E virus infection over a period of 49 +/- 18 days after the diagnosis of index case, although a majority lacked IgG antibodies to hepatitis E virus and were likely to be susceptible. This suggests that person-to-person transmission is uncommon in sporadic hepatitis E.

Prophylactic potential of autoclaved Leishmania donovani with BCG against experimental visceral leishmaniasis

The prophylactic efficacy of autoclaved Leishmania donovani (ALD) and autoclaved L. major (ALM)--a heterologous vaccine developed against cutaneous leishmaniasis (used as a reference vaccine), along with BCG--was evaluated against L. donovani in hamsters (Mesocricetus auratus). Animals were immunized with triple doses (21 days apart) of either ALD or ALM (1.0 mg) with or without BCG (0.1 mg) and challenged 21 days later with 1 x 10(6) L. donovani amastigotes intracardially. Animals immunized with ALM + BCG and ALD + BCG yielded 94.3% and 86.1% parasite inhibition respectively in comparison to the BCG only and unvaccinated controls. Fifty and 33.3% of the vaccinated animals (ALM + BCG and ALD + BCG respectively) were completely devoid of parasites when tested on day 45 post-challenge (p.c.) and survived till the experiment was terminated. The mean survival of ALM + BCG and ALD + BCG groups (animals harbouring parasites) was longest (168 and 139 days respectively). No significant increase in anti-leishmanial antibody level (ELISA) was noticed in ALD + BCG and ALM + BCG groups whereas it increased progressively in the rest of the experimental groups. The lymphoproliferative responses to PHA and Con A, of the 2 vaccinated groups were comparable to that of normal controls on day 45 p.c. The study suggests that ALD along with BCG can offer substantial protection against visceral leishmaniasis in hamsters.

High frequency of hepatitis B virus infection in patients with beta-thalassemia receiving multiple transfusions

BACKGROUND AND OBJECTIVES

Hepatitis B virus (HBV) may occasionally be transmitted through transfusion of blood units that are hepatitis B surface antigen (HBsAg) negative but HBV DNA positive. Children with beta-thalassemia are particularly susceptible to HBV because they receive multiple blood transfusions. These children have high infection rates despite vaccination against HBV. Post-vaccination infections may be a result of viruses harbouring surface (S)-gene mutations (e.g. G587A) in a region critical for reactivity to antibody to hepatitis B surface antigen (anti-HBs). The true prevalence of HBV in individuals with beta-thalassemia has not been studied previously.

PATIENTS AND METHODS

Seventy patients with beta-thalassemia (median age 6 years; range 8 months to 22 years; 49 male), who had received seven to 623 (median 61) units of blood each and three doses (10/20 micro g) of HBV vaccine (Engerix B) before presentation to us, were included in the study; 50 of the 70 patients had received transfusions prior to vaccination. Enzyme-linked immunoassay for serological markers [HBsAg, antibody to hepatitis B core antigen (anti-HBc) and quantitative anti-HBs] and polymerase chain reaction (PCR) followed by Southern hybridization for molecular detection of hepatitis B, was performed on all samples. The PCR-amplified product was cloned, sequenced and the nucleotide and deduced amino acid sequences for the HBV S and polymerase (P) genes were analysed for mutations.

RESULTS

Four of 70 (5.7%) individuals with beta-thalassemia were HBsAg positive and 14 (20%) were anti-HBc positive. The prevalence of serological markers increased with number of transfusions (P < 0.01). Of 70 patients, 53 (75.7%) had an anti-HBs titre of > 10 IU/l following vaccination and 17 (24.3%) were non-responders (< 10 IU/l); 22 (31.4%) of the 70 were DNA positive. The frequency of HBV infection in beta-thalassemia was similar in vaccine responders and non-responders. The virus was of subtype ayw (genotype D) in the five DNA-positive samples in which a 388-nucleotide region of the S gene was sequenced. Mutations occurred at 13 positions in the S gene and at 10 positions in the P gene. Hydrophobicity plots revealed differences in amino acid regions 117-165 and 195-211. Some of these amino acid substitutions coincided with the putative cytotoxic T-lymphocyte epitopes of both S and P proteins.

CONCLUSIONS

A high frequency of HBV infection was seen using molecular methods in thalassemic patients. The frequency of infection was similar in vaccine responders and non-responders. A number of mutations were observed in the S gene, which could have implications for viral replication as well as virus-host cell interaction.

Establishment of asymptomatic Leishmania donovani infection in Indian langurs (Presbytis entellus) through intradermal route

Indian langurs, which were previously reported to be highly susceptible, were infected intradermally using variable numbers of promastigotes along with different doses, 1/2 pair, 5 pairs and 10 pairs respectively of salivary gland lysate (SGL). Although, all the monkeys developed mild infection and remained subclinically infected throughout the observation period, which later resolved, none of them could develop the classical disease. No marked antigen specific antibody or lymphoproliferative response was noticed throughout the experimental period. However, a late IFN-gamma response (by day 90 pi.) was demonstrated in monkeys infected with 2 x 10(6) promastigotes +10 pairs SGL. It seems that a single intradermal dose of promastigotes with or without SGLs had a vaccines like effect. Perhaps, multiple frequent inoculations, as happens in the natural situation, may be necessary for the development of full-blown disease.

Successful vaccination against Leishmania donovani infection in Indian langur using alum-precipitated autoclaved Leishmania major with BCG

Autoclaved Leishmania major (ALM) along with BCG, presently undergoing phase II clinical trial by WHO for its vaccine potential against cutaneous leishmaniasis, has been successfully evaluated in single and triple dose schedules against L. donovani in Indian langurs (Presbytis entellus). Encouraged with the results, another formulation alum-precipitated ALM (provided by WHO) along with BCG has been evaluated in this system. Eight monkeys were vaccinated with alum-precipitated ALM + BCG (1 mg of each per animal) while four were kept as unvaccinated controls. All were challenged with 100 x 10(6) amastigotes i.v. on day 60 post vaccination. Parasitic assessment in splenic tissue was performed on day 45, 90 and 180 p.c. Initially, seven of the eight vaccinated monkeys developed infection (two to six amastigotes per 1000 cell nuclei), which resolved by day 180 p.c., while the eighth monkey had a parasite burden of 14 amastigotes per 1000 cell nuclei on day 45 p.c. and died on day 130 p.c. On the other hand, there was progressive infection in unvaccinated control animals and three out of four died between days 110 and 120 p.c., and one monkey, which had low parasite burden, died on day 178 p.c. Prior to challenge, there was an initial rise in antileishmanaial antibodies in the vaccinated group compared to the unvaccinated control group, which later came down to normal level, while it remained higher in the unvaccinated control group. An increasing pattern of antigen-specific proliferative responses and interferon-gamma level to the two antigens--autoclaved L. donovani (ALD) and ALM--was observed in vaccinated monkeys throughout the experiment. There was a good correlation between parasite burden and IFN-gamma level on days 90 and 180 p.c., indicating IFN-gamma response as a sensitive parameter of immune status. The findings suggest alum-precipitated ALM+BCG as a potential vaccine against visceral leishmaniasis and warrants clinical trials.

Recombinant hemagglutinin protein of rinderpest virus expressed in insect cells induces humoral and cell mediated immune responses in cattle

Rinderpest virus causes a highly contagious and often fatal disease in domestic and wild ruminants. The surface glycoproteins, hemagglutinin (H) and fusion (F) proteins of this enveloped virus are known to confer protective immunity in cattle. We have reported the generation of a recombinant baculovirus expressing H protein and studied its protective properties in cattle. In this report, we demonstrate that the recombinant baculovirus encoded H protein expressed in insect cells gets incorporated into extracellular baculovirus. Single administration of low doses of purified recombinant extracellular virus with or without adjuvant induces virus neutralizing antibody responses and bovine leukocyte antigen (BoLA) class II restricted helper T cell responses in cattle.

Mechanism of action of disease modifying anti-rheumatic agent, gold sodium thiomalate (GSTM)

GSTM has been used for long in the treatment of rheumatoid arthritis (RA). However, its mechanism of action is still poorly understood. In the last decade, tumor necrosis factor-alpha (TNF-alpha) has emerged as the major pro-inflammatory cytokine in the pathogenesis of RA. We studied the effect of GSTM on spontaneous and LPS-stimulated TNF-alpha production by human peripheral blood mononuclear cells (PBMCs) of normal volunteers. PBMCs were isolated from 20 normal volunteers and cultured in the presence of absence of lipopolysaccharide (LPS 10 ng/ml) and GSTM (1 microgram/ml). TNF-alpha level was measured using commercial enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR). The TNF-alpha response to LPS was heterogeneous. PBMCs of 24 subjects showed high LPS-stimulated TNF-alpha production (LPS-responsive group), whereas that of six individuals had low LPS-stimulated TNF-alpha production (LPS-non-responsive group). GSTM-stimulated spontaneous TNF-alpha production and inhibited LPS-stimulated TNF-alpha production in 16 of 24 (75%) individuals of LPS-responsive group and one of six individuals (17%) of LPS-non-responsive group. The suppression of TNF-alpha by GSTM was also demonstrated at the mRNA level. We conclude that there is a heterogeneity among normal population for TNF-alpha production in response to LPS, and GSTM inhibits LPS-stimulated TNF-alpha production, primarily in LPS responders. Further study is needed to establish the relationship between LPS responsiveness and GSTM suppression.

Simultaneous amplification of DNA and RNA virus using multiplex PCR system

A large number of disease-causing bacteria and viruses are being sequenced and PCR is increasingly used for the diagnosis of the diseases. We have designed a multiplex PCR system for hepatitis B virus (HBV), a DNA virus, and hepatitis E virus (HEV), an RNA virus. A modified technique has been standardized for simultaneous extraction of DNA and RNA, followed by a one-step RT-PCR/PCR.

Absence of Toll-like receptor 4 explains endotoxin hyporesponsiveness in human intestinal epithelium

BACKGROUND

The Toll protein in Drosophila regulates dorsal ventral patterning during embryogenesis, and participates in antibacterial and antifungal host defense. Mammalian homologues are termed Toll-like receptors and, to date, nine have been cloned (TLRI-9) in humans. They are characterized by extracellular leucine-rich repeats and a cytoplasmic domain similar to the interleukin 1 receptor. Both TLR2 and TLR4 recognize various bacterial cell wall components including lipopolysaccharide (LPS). This results in the activation of the NFkappaB pathway. Peripheral blood mononuclear cells (PBMCs) express both TLR2 and TLR4. The authors hypothesized that the expression of TLR 2 and TLR4 in human intestinal epithelial cells differs from PBMCs because of the abundance of LPS in the intestinal lumen.

METHODS

Epithelial cells were isolated from Caco-2 cells, fetal gut explants, and small bowel resection specimens using Hanks/ethylenediamine tetraacetic acid solution. PBMCs were used as positive controls. Ribonucleic acid (RNA) was isolated using the TRIzol method. Standard reverse transcription-polymerase chain reaction examined TLR2 and TLR4 messenger RNA (mRNA) expression. NFkappaB expression was determined using a luciferase reporter assay.

RESULTS

TLR2 mRNA was highly expressed in PBMCs and was present in all human intestinal epithelial cells. TLR4 mRNA was detected only in PBMCs. TLR4 is not present in epithelium from children with inflammatory bowel disease. In Caco-2 cells, significant NFkappaB activation in response to LPS occurred only in the presence of TLR4 introduced by complementary deoxyribonucleic acid transfection.

CONCLUSION

Absence of TLR4 is associated with endotoxin hyporesponsiveness of intestinal epithelial cells. TLR4 is not directly involved in inflammation of the intestinal epithelium. Although TLR2 is normally present in the epithelial cell, it plays a limited role in inflammation. It may be activated during conditions in which bacterial cell wall concentrations within the intestine are pathologically high.

Dietary regulation of intestinal gene expression

We are becoming increasingly aware of inherited genetic abnormalities as causes of disease. However, alterations in gene expression can also contribute to other disease processes. Recently it has been suggested that our environment may alter such genes and thus be a direct influence on disease. Diet is a potent mechanism for altering the environment of cells of most organs, particularly the gastrointestinal tract. This review addresses the influence of nutritional factors on intestinal gene regulation. These influences include insulin, which is not a dietary component but responds to dietary changes, and butyrate, a short chain fatty acid produced by normal intestinal flora. Manipulation of diet may be a means of treating intestinal disorders. Nutritional treatment therefore is also discussed in the light of its effect on gene expression.

Is immunoproliferative small intestinal disease uncommon in India?

Till date only three series of immunoproliferative small intestinal disease (IPSID) describing 22 patients have been reported from India. Seven patients with IPSID in two tertiary referral centers in India are included in the study. Diagnosis was based on typical clinical features [diarrhoea (7/7), weight loss (7/7), clubbing (6/7), fever (3/7), abdominal pain and lump (3/7)], biochemical evidence of malabsorption and duodenal biopsy findings. All patients were young males (mean age 29.8 +/- 11.8 years, range 17-53). Atypical features included gastric involvement (1/7), colonic involvement (1/7) and appearance of pigmented nails following anti-cancer chemotherapy (1/7) which disappeared six months after omitting doxorubin from chemotherapy regimen. Parasitic infestation was common. Ascaris lumbricoides (1/7), Giardia lamblia and hookworm (1/7), Strongyloides stercoralis and Trichuris trichura (1/7). In the latter patient S. stercoralis became disseminated after anti-malignant chemotherapy. One patient had gastric H. pylori infection. Four of the seven patients who were misdiagnosed as tropical sprue were treated with tetracycline. This raises doubt on efficacy of tetracycline alone in treatment of IPSID. One other patient was misdiagnosed and treated as intestinal tuberculosis. Early diagnosis and administration of chemotherapy may improve survival in this disease.

Cutting edge: C-C chemokine receptor 6 is essential for arrest of a subset of memory T cells on activated dermal microvascular endothelial cells under physiologic flow conditions in vitro

Memory T cells (mTC) express multiple chemokine receptors (including CCR4 and CCR6) that may potentially be involved in their arrest on inflamed endothelia. Herein, we specifically addressed whether CCR6 is required for mTC to arrest on TNF-alpha-activated human dermal microvascular endothelial cells (HDMEC) in vitro under shear stress conditions. Recombinant liver and activation-regulated chemokine (LARC)/CCL20 (a CCR6 ligand) induced firm arrest of cutaneous lymphocyte Ag(+) mTC in a flow chamber system using purified substrates. Strikingly, desensitization of CCR6 with LARC, but not thymus and activation-regulated chemokine/CCL17 or secondary lymphoid tissue chemokine/CCL21, caused a 50-75% decrease (p < 0. 001) in arrest of mTC on HDMEC, which was indistinguishable from the reduction observed when total mTC were treated with pertussis toxin (p > 0.5). CCR6-depleted mTC also had a markedly reduced ability to arrest on HDMEC. Our results suggest that LARC production by activated endothelial cells and CCR6 expression by mTC may be critical components in the pertussis toxin-sensitive arrest of mTC on activated HDMEC.

Phosphorothioate backbone modification modulates macrophage activation by CpG DNA

Macrophages respond to unmethylated CpG motifs present in nonmammalian DNA. Stabilized phosphorothioate-modified oligodeoxynucleotides (PS-ODN) containing CpG motifs form the basis of immunotherapeutic agents. In this study, we show that PS-ODN do not perfectly mimic native DNA in activation of macrophages. CpG-containing PS-ODN were active at 10- to 100-fold lower concentrations than corresponding phosphodiester ODN in maintenance of cell viability in the absence of CSF-1, in induction of NO production, and in activation of the IL-12 promoter. These enhancing effects are attributable to both increased stability and rate of uptake of the PS-ODN. By contrast, PS-ODN were almost inactive in down-modulation of the CSF-1R from primary macrophages and activation of the HIV-1 LTR. Delayed or poor activation of signaling components may contribute to this, as PS-ODN were slower and less effective at inducing phosphorylation of the extracellular signal-related kinases 1 and 2. In addition, at high concentrations, non-CpG PS-ODN specifically inhibited responses to CpG DNA, whereas nonstimulatory phosphodiester ODN had no such effect. Although nonstimulatory PS-ODN caused some inhibition of ODN uptake, this did not adequately explain the levels of inhibition of activity. The results demonstrate that the phosphorothioate backbone has both enhancing and inhibitory effects on macrophage responses to CpG DNA.

Metastatic extragonadal seminoma associated with cardiac transplantation

A 37-year-old man who had successfully undergone cardiac transplantation for dilated cardiomyopathy presented with a history of severe pain over his left shoulder, rib cage and thoracic spine. Clinical examination revealed the presence of bony tenderness over these sites, but there was no other clinical evidence of malignancy. Further investigations suggested the presence of multiple bony metastases. Bone biopsy revealed extensive bone marrow infiltration by large undifferentiated cells showing pronounced cytoplasmic vacuolation with a striking granulomatous reaction. Immunocytochemistry revealed these anaplastic cells to be cytokeratin and placenta-like alkaline phosphatase positive but S100, CD30 and lymphoid marker negative. Analyses by in situ hybridisation of these cells revealed no evidence of Epstein-Barr virus infection. Overall the pathology suggested a diagnosis of metastatic seminoma. Confirmation of this diagnosis was obtained by the analysis of serum human chorionic gonadotrophin which was elevated at 90 IU/l. In the absence of testicular or retroperitoneal disease, it is very likely that this unusual case of metastatic seminoma was related to the patient's immunosuppressive therapy, which at diagnosis included cyclosporin and prednisolone. The patient was successfully treated with cisplatin based chemotherapy and decreased immunosuppression and remains in complete remission one year after completion of chemotherapy. Seminoma is an uncommon complication of prolonged immunosuppression with very few cases being described in the literature post-organ transplantation. This case shows that the clinical presentation of this treatable tumour in this patient population can be unusual and difficult to diagnose.

Complement degradation product C3d in urine: marker of lupus nephritis

OBJECTIVE

To examine whether serum and urine C3d, a degradation product of C3, correlate with renal and extrarenal lupus activity.

METHODS

Serum and urinary C3d levels were measured by ELISA in 15 healthy individuals and 24 patients with systemic lupus erythematosus (SLE) (8 with inactive disease, 7 with active but nonrenal disease, 9 with active lupus nephritis). Disease activity variables like serum C3, C4, and anti-dsDNA antibodies were also measured.

RESULTS

The median serum C3d levels were significantly higher (p < 0.01) in patients with active (26 arbitrary units/ml; AU/ml) and inactive SLE (27 AU/ml) compared to healthy controls (11.25 AU/ml); levels were comparable in patients with active renal and extrarenal SLE. On the other hand, urine C3d was elevated only in patients with active SLE; its level was highest in patients with active lupus nephritis (0.87 AU/ml) compared to patients with active extrarenal diseases (0.31 AU/ml; p < 0.05), to patients with inactive lupus nephritis (0.06 AU/ml; p < 0.001), or to levels in healthy individuals (0.06; p < 0.001). Urine C3d showed stronger correlation with disease activity score (SLE Disease Activity Index) than serum C3, C4, anti-dsDNA antibodies, and serum C3d.

CONCLUSION

Urine C3d is a good index of active lupus, particularly lupus nephritis.

Leishmania donovani: cellular and humoral immune responses in Indian langur monkeys, Presbytis entellus

We have previously reported that disease mimicking human visceral leishmaniasis can be established in Presbytis entellus, the Indian langur monkey, following a single intravenous challenge of 10(8) Leishmania donovani amastigotes. In the present report, infection was assessed in monkeys infected intravenously with a single dose of 10(8) amastigotes (HDA group), three weekly doses of 10(7) amastigotes (LDA group) and three weekly doses of 5 x 10(7) promastigotes (HDP group). Typical clinical infection was established in all three groups with significant parasite load. There was a gradual and sustained rise in anti-leishmania specific immunoglobulin G response, and a severe fall in the lymphoproliferative response to the T cell mitogens PHA and Con A by day 80 post infection (p.i.). The antibody level remained elevated until death in monkeys of the HDA and HDP groups; the T-cell responses showed a recovery prior to death. T-cell responses to leishmania antigen, however, could not be demonstrated in any of these monkeys prior to death. One monkey of the LDA group survived for 155 days and two monkeys spontaneously eradicated the infection. Surprisingly, one monkey of the HDA group also achieved spontaneous cure. In the three monkeys which eradicated infection spontaneously, the antibody level declined to baseline levels on day 180 p.i. with a well demonstrable antigen specific lymphoproliferative response; no parasites could be demonstrated in splenic aspirates by direct examination of culture. These data demonstrate that disease severity may be the function of the total inoculum dose rather than the stage of the parasite and that the immunological responses in the Indian langur model parallel the reported changes in human visceral leishmaniasis. This makes the langur a potentially useful model for the evaluation of candidate anti-leishmanial drugs and vaccines.