An investigation into the structural determinants of cannabinoid receptor ligand efficacy

1. A number of side-chain analogues of delta8-THC were tested in GTPgammaS binding assay in rat cerebellar membranes. O-1125, a saturated side-chain compound stimulated GTPgammaS binding with an Emax of 165.0%, and an EC50 of 17.4 nM. 2. O-1236, O-1237 and O-1238, three-enyl derivatives containing a cis carbon-carbon double bond in the side-chain, stimulated GTPgammaS binding, acting as partial agonists with Emax values ranging from 51.3-87.5% and EC50 values between 4.4 and 29.7 nM. 3. The stimulatory effects of O-1125, O-1236, O-1237 and O-1238 on GTPgammaS binding were antagonized by the CB1 receptor antagonist SR 141716A. The K(B) values obtained ranged from 0.11-0.21 mM, suggesting an action at CB1 receptors. 4. Five-ynyl derivatives (O-584, O-806, O-823, O-1176 and O-1184), each containing a carbon-carbon triple bond in the side-chain, did not stimulate GTPgammaS binding and were tested as potential cannabinoid receptor antagonists. 5. Each -ynyl compound antagonized the stimulatory effects of four cannabinoid receptor agonists on GTPgammaS binding. The K(B) values obtained, all found to be in the nanomolar range, did not differ between agonists or from cerebellar binding affinity. 6. In conclusion, alterations of the side-chain of the classical cannabinoid structure may exert a large influence on affinity and efficacy at the CB1 receptor. 7. Furthermore, this study confirms the ability of the GTPgammaS binding assay to assess discrete differences in ligand efficacies which potentially may not be observed using alternative functional assays, thus providing a unique tool for the assessment of the molecular mechanisms underlying ligand efficacies.

Leishmania donovani infection of a susceptible host results in CD4+ T-cell apoptosis and decreased Th1 cytokine production

The disease visceral leishmaniasis is caused by a protozoan parasite, Leishmania donovani and is characterized by depressed cell-mediated immunity (CMI) and unhindered parasite growth in a susceptible host. The opposite trend is observed in a resistant host. However, the mechanism of this loss of CMI during the progressive disease is unknown as yet. In this report, we demonstrate that more than 40% of CD4+ T cells from a susceptible host undergo apoptosis resulting in a significant decrease in interleukin (IL)-2 and interferon (IFN)-gamma secretion, leaving IL-4 secretion unaffected. These changes are not apparent in the case of CD4+ T cells derived from a resistant host. The data reported here suggest that experimental Leishmania donovani infection leads to selective deletion of the IL-2 and IFN-gamma-secreting cells but not Th2-like cells in a susceptible but not a resistant host.

Apoptosis of Th1-like cells in experimental tuberculosis (TB)

Th1 cell-induced anti-mycobacterial immunity is lost during a progressive Mycobacterium tuberculosis infection in a susceptible host. This study was designed to test the mechanism of the loss of anti-mycobacterial cell-mediated immune response. We demonstrate that M. tuberculosis infection results in increased Fas expression and decreased Bcl-2 expression in CD4+ T cells. When CD4+ T cells are stimulated in vitro, they show increased apoptosis and decreased production of IL-2 and interferon-gamma (IFN-gamma) but not of IL-4. These changes may result in selective apoptosis of Th1-like cells, leading to the loss of cell-mediated immune response against M. tuberculosis.

Leishmania donovani infection of a susceptible host results in apoptosis of Th1-like cells: rescue of anti-leishmanial CMI by providing Th1-specific bystander costimulation

A protective immune response against Leishmania donovani infection is mediated by T-helper type 1 (Th1) cells. Th1 induced cell-mediated immunity (CMI), as assessed by anti-leishmanial DTH response, is lost in a susceptible host such as BALB/c mice. Although the impaired Th1 function eventuates in unhindered parasite growth and in manifestation of the susceptible phenotype, the mechanism of down-regulation of the Th1 function is yet to be elucidated. Here, we provide evidence that the parasite down-regulates the expression of a Th1-specific costimulatory molecule, M150, on the surface of infected BALB/c mice-derived macrophages. Th cells are rendered unresponsive to anti-CD3 Ab-mediated stimulation after interaction with infected macrophages. The anergized T cells produce much less IL-2, IL-4 and IFN-gamma compared to those T cells which were costimulated using normal macrophages. The defect in proliferation, anti-CD3 Ab induced unresponsiveness and IFN-gamma but not IL-4 production can be restored by providing bystander costimulation through M150. These results not only unfold a novel immune evasion strategy used by the parasite but also clarify the mechanism of Th1 cell debilitation during the disease. Recovery of Th1 cytokine production by bystander costimulation through M150 may help in formulating a new strategy for the elimination of intracellular parasites.

Association of vitamin D receptor genotype with leprosy type

Host genetic factors including major histocompatibility complex (MHC) polymorphisms influence both susceptibility to leprosy per se and also to leprosy type. Non-MHC genes may play an important role, but such genes remain undefined. The influence of two non-MHC candidate genes was assessed in a case-control study of Bengali leprosy patients from Calcutta. Recent studies have implicated variation in the vitamin D receptor (VDR) gene in susceptibility to several diseases, including osteoporosis and pulmonary tuberculosis. In this population, homozygotes for the alternate alleles of the VDR polymorphism are associated, respectively, with lepromatous and tuberculoid leprosy. The NRAMP1 (natural resistance associated macrophage protein 1) gene may influence human mycobacterial disease susceptibility based on studies with the murine homologue Nramp1. However, no significant association was found between NRAMP1 and leprosy susceptibility. This study suggests that the VDR polymorphism may influence susceptibility to some diseases by affecting the type and the strength of the host immune response.

CTLA4 (CD152) modulates the Th subset response and alters the course of experimental Leishmania major infection

Since both the nature and the amplitude of an antigen-specific T cell response are dependent on co-stimulatory signals, we have investigated the role of CD28/CD152-mediated T cell co-stimulation in the regulation of experimental cutaneous leishmaniasis. CD28-deficient mice and their wild-type littermates are equally susceptible to Leishmania major infection. Whole anti-CD152 antibody significantly exacerbates the disease while anti-CD152 Fab ameliorates the disease in genetically susceptible BALB/c mice but not in C57BL/6, a resistant strain. The anti-CD152-induced exacerbation of the disease is accompanied by increased IL-4-secreting cell number, diminished parasite-specific delayed-type hypersensitivity (DTH) response and augmented anti-2,4,6-trinitrophenyl (TNP) IgG1 in response to TNP-leishmanial antigen crude soluble antigen (CSA), suggesting an exaggerated Th2 type of response. Anti-CD152 Fab-mediated amelioration of the disease is associated with increased IFN-gamma-secreting cell number, increased parasite-specific DTH response and enhanced IgG2a isotype in response to TNP-CSA suggesting a Th1 type of response. Unlike TNP-CSA, TNP-keyhole limpet hemocyanin does not induce the change in Ig isotype, indicating that the immunomodulatory effect of anti-CD152 is antigen specific. Anti-CD152 antibody-induced early change in Th subsets suggests an important role for CD152 in determining the course of L. major infection, perhaps by alteration of Th subset differentiation.

Comparison of cannabinoid binding sites in guinea-pig forebrain and small intestine

We have investigated the nature of cannabinoid receptors in guinea-pig small intestine by establishing whether this tissue contains cannabinoid receptors with similar binding properties to those of brain CB1 receptors. The cannabinoids used were the CB1-selective antagonist SR141716A, the CB2-selective antagonist SR144528, the novel cannabinoid receptor ligand, 6'-azidohex-2'-yne-delta8-tetrahydrocannabinol (O-1184), and the agonists CP55940, which binds equally well to CB1 and CB2 receptors, and WIN55212-2, which shows marginal CB2 selectivity. [3H]-CP55940 (1 nM) underwent extensive specific binding both to forebrain membranes (76.3%) and to membranes obtained by sucrose density gradient fractionation of homogenates of myenteric plexus-longitudinal muscle of guinea-pig small intestine (65.2%). Its binding capacity (Bmax) was higher in forebrain (4281 fmol mg(-1)) than in intestinal membranes (2092 fmol mg(-1)). However, the corresponding KD values were not significantly different from each other (2.29 and 1.75 nM respectively). Nor did the Ki values for its displacement by CP55940, WIN55212-2, O-1184, SR141716A and SR144528 from forebrain membranes (0.87, 4.15, 2.85, 5.32 and 371.9 respectively) differ significantly from the corresponding Ki values determined in experiments with intestinal membranes (0.99, 5.03, 3.16, 4.95 and 361.5 nM respectively). The Bmax values of [3H]-CP55940 and [3H]-SR141716A in forebrain membranes did not differ significantly from each other (4281 and 5658 fmol mg(-1)) but were both greater than the Bmax of [3H]-WIN55212-2 (2032 fmol mg(-1)). O-1184 (10 or 100 nM) produced parallel dextral shifts in the log concentration-response curves of WIN55212-2 and CP55940 for inhibition of electrically-evoked contractions of the myenteric plexus-longitudinal muscle preparation, its KD values being 0.20 nM (against WIN55212-2) and 0.89 nM (against CP55940). We conclude that cannabinoid binding sites in guinea-pig small intestine closely resemble CB1 binding sites of guinea-pig brain and that 0-1184 behaves as a cannabinoid receptor antagonist in the guinea-pig myenteric plexus-longitudinal muscle preparation.

Potent cyano and carboxamido side-chain analogues of 1', 1'-dimethyl-delta8-tetrahydrocannabinol

The synthesis and pharmacological profile of several cyano (1a-e) and carboxamido (2a-h) side-chain-substituted analogues of 1', 1'-dimethyl-Delta8-THC are described. Commercially available cyano compound 3 was transformed to the resorcinol 6 in a three-step sequence. Condensation of 6 with p-menth-2-ene-1,8-diol formed the THC 7a which, with sodium cyanide/DMSO, gave 1b. Protection of the phenol in 7a as the MOM derivative provided the common intermediate 8 for the synthesis of 1a,c,e. Compound 1d was also synthesized from 7a via the aldehyde 9a. Base hydrolysis of 1b gave the acid 10 which, via its acid chloride and subsequent treatment with the appropriate amine, formed the target compounds 2a-h. The pharmacological profile indicated that the cyano analogues 1a-e had very high CB1 binding affinity (0.36-13 nM) and high in vivo potency as agonists. Two analogues (1a,b) had extremely high potency in the mouse tetrad tests. The dimethylcarboxamido analogue 2a showed a similar profile to 1a,b. The high potency was also retained in analogue 2c. In contrast the sulfonamide analogue 2d was unique as it had greater affinity than Delta9-THC, yet it was practically devoid of agonist effects. This study suggests that the incorporation of a cyano or an amide substituent in the side chain of Delta8-THC-DMH can enhance potency and can also lead to compounds with a unique profile which have high binding affinity and are practically devoid of agonist effects.

Altered membrane permeability as the basis of bactericidal action of methdilazine

The growth inhibition of Escherichia coli and Staphylococcus aureus was accompanied by significant release of K+ and UV-absorbing small molecules upon exposure to methdilazine, an extensively used phenothiazine antihistamine. A severe decrease in [U-14C] glucose uptake and a rapid efflux of hexose from sugar-preloaded bacteria were also observed but without visible cellular lysis. Considerable damage to membrane permeability by methdilazine was proposed to explain the rapid loss in cfu/mL of the bacteria.

Why relapse occurs in PB leprosy patients after adequate MDT despite they are Mitsuda reactive: lessons form Convit's experiment on bacteria-clearing capacity of lepromin-induced granuloma

It is amazing how after years of scientific research and therapeutic progress many simple and basic questions about protective immunity against Mycobacterium leprae remain unanswered. Although the World Health Organization (WHO) has recommended short-term multidrug therapy (WHO/MDT) for the treatment of paucibacillary (PB) leprosy patients, from time to time several workers from different parts of the globe have reported inadequate clinical responses in a few tuberculoid and indeterminate leprosy patients following adequate WHO/MDT despite the fact that they are Mitsuda responsive. A few borderline tuberculoid patients harbor acid-fast bacilli (AFB) in their nerves for many years even though they become clinically inactive following MDT, a fact which has been ignored by many leprosy field workers. Keeping these patients in mind, we have attempted to investigate the cause of the persistence of AFB in PB cases and have looked into the question of why Mitsuda positivity in tuberculoid and indeterminate leprosy patients, as well as in healthy contacts, is not invariably a guarantee for protectivity against the leprosy bacilli. We have: a) analyzed the histological features of lepromin-induced granulomas, b) studied the bacteria-clearing capacity of the macrophages within such granulomas, and c) studied the in vitro leukocyte migration inhibition factor released by the blood leukocytes of these subjects when M. leprae sonicates have been used as an elicitor. The results of these three tests in the three groups of subjects have been compared and led us to conclude that the bacteria-clearing capacity of the macrophages within lepromin-induced granuloma (positive CCB test) may be taken as an indicator of the capability of elimination of leprosy bacilli and protective immunity against the disease. This important macrophage function is not invariably present in all tuberculoid and indeterminate leprosy patients or in all contacts even though they are Mitsuda responsive and are able to show a positive leukocyte migration inhibition (LMI) test. It is likely but not certain that this deficit of the macrophage is genetically predetermined and persists after completion of short-term WHO/MDT. Thus, after discontinuation of treatment slow-growing, persisting M. leprae multiply within macrophages leading to relapse.

Tumor necrosis factor promoter polymorphism and susceptibility to lepromatous leprosy

Genetically determined differences in immune responses to environmental agents may underlie susceptibility to many autoimmune and infectious diseases. Leprosy provides an example of a polarity in the type of immune response made to an infectious agent, and there is evidence that the major histocompatibility complex is genetically linked to leprosy type. It was found that HLA-DR2 is associated with both tuberculoid and lepromatous types of leprosy; however, a variant at position -308 of the promoter of the neighboring tumor necrosis factor (TNF) gene was increased in frequency in lepromatous (odds ratio = 3.0, P = .02) but not tuberculoid leprosy. Some studies have found higher serum levels of TNF in lepromatous than tuberculoid leprosy, and high TNF levels are found in malaria and leishmaniasis, which are also associated with this TNF allele. It is speculated that this association reflects genetic variability in cytokine production, which influences the immune response to and clinical outcome of leprosy.

Immunotherapy of lepromin-negative borderline leprosy patients with low-dose Convit vaccine as an adjunct to multidrug therapy; a six-year follow-up study in Calcutta

The present report, which describes management of lepromin-negative borderline leprosy patients with low-dose Convit vaccine, is an extension of our earlier study on the treatment of lepromatous leprosy patients with low-dose Convit vaccine as an adjunct to multidrug therapy (MDT). The test Group I, consisting of 50 lepromin-negative, borderline leprosy patients, were given low-dose Convit vaccine plus MDT. The control group II consisted of 25 lepromin-negative, borderline leprosy patients given BCG vaccination plus MDT and 25 lepromin-negative, borderline leprosy patients given killed Mycobacterium leprae (human) vaccine plus MDT. The control group III consisted of 50 lepromin-positive, borderline leprosy patients not given any immunostimulation but given only MDT. Depending upon the lepromin unresponsiveness, the patients were given one to four inoculations of the various antileprosy vaccines and were followed up every 3 months for 2 years for clinical, bacteriological and immunological outcome. All patients belonging to the test and control groups showed clinical cure and bacteriological negativity within 2 years. However, immunologic potentiation, assessed by lepromin testing and the leukocyte migration inhibition test (LMIT), was better in the test patients receiving low-dose Convit vaccine plus MDT than in the control patients receiving BCG vaccine plus MDT or killed M. leprae vaccine plus MDT or MDT alone. But the capacity of clearance bacteria (CCB) test from the lepromin granuloma showed poor bacterial clearance in the test patients. However, there was no relapse during 6 years of follow up. Two mid-borderline (BB) patients had severe reversal reactions with lagophthalmos and wrist drop during immunotherapy despite being given low-dose Convit vaccine.

Prevalence of herpesviridae and hepatitis B virus DNA in the liver of patients with non-A, non-B fulminant hepatic failure

Members of the herpes virus family and hepatitis B virus (HBV) have been implicated as etiologic agents in non-A, non-B (NANB) fulminant hepatic failure (FHF), but the frequency of infection with these agents has not been established using appropriate controls. To examine this issue, we studied 50 NANB FHF patients and 104 liver transplant recipients from North America and Europe. Hepatic DNA was analyzed by polymerase chain reaction (PCR) for evidence of Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpes simplex virus I (HSV I) and II (HSV II), varicella-zoster virus (VZV), and human herpes virus-6 (HHV-6) nucleic acid sequences. The prevalence of HBV was assessed in North American subjects only. HSV I, HSV II, VZV, and HHV-6 viral sequences were not observed in any samples. Three of 50 FHF (6%) and 14 of 104 control patients (13%) were positive for CMV DNA. Two of 50 FHF (4%) and 10 of 104 control patients (10%) had EBV DNA, and HBV DNA was observed in 3 of 10 North American FHF patients (30%) and 3 of 59 controls (5%) without serum markers for HBV infection. The finding of HBV DNA in the liver of seronegative controls from North America but not Europe suggests that occult hepatitis B sequences in patients with NANB FHF may simply reflect geographic differences. The majority of cryptogenic FHF cases cannot be attributed to infection with herpes viruses or HBV.

Toxic shock syndrome toxin-1-induced death is prevented by CTLA4Ig

Lethal toxic shock syndrome (TSS) results from the MHC class II presentation of bacterial superantigens, most commonly toxic shock syndrome-1 (TSST-1), to specific TCR Vbeta-bearing T cells. This superantigen-induced stimulation of whole T cell subsets leads to the exuberant cytokine production that in turn causes the shock syndrome. Since T cell activation and cytokine production are known to be dependent upon costimulatory signals, we reasoned that interfering with costimulation could effect TSS outcome. To test that hypothesis, we evaluated the effect of CTLA4Ig, a fusion protein known to block costimulatory signaling, on TSST-1-induced responses. CTLA4Ig not only blocked TSST-1-stimulated T cell proliferation by 90% in vitro, it also strikingly ameliorated TSST-1 induced TSS in vivo. While all mice co-administered TSST-1 and control Ig died, 75% of the CTLA4Ig plus TSST-1-treated mice survived. This salutary CTLA4Ig effect correlated with markedly diminished TSST-1 induced serum levels of TNF-alpha and IFN-gamma, but TSST-1-triggered IL-2 release was not affected. Surprisingly, while CTLA4Ig treatment group survivors remained sensitive to TSS induced by an unrelated superantigen (staphylococcal enterotoxin B), they were completely resistant to a second TSST-1 challenge. Furthermore, this TSST-1 resistance could be transferred to naive C57BL/6 mice using CD8+ T cells from CTLA4Ig plus TSST-1-primed mice. These data suggest several novel interpretations: 1) that the release of TNF-alpha and IL-2 have a different costimulatory signal dependence in vivo, 2) that the TSS resistance conferred by CTLA4Ig was superantigen specific, and 3) that the delayed and transferable resistance to TSST-1 was due, at least in part, to CD8+ T cells with suppressor function.

Toxic shock syndrome toxin-1-induced death is prevented by CTLA4Ig

Lethal toxic shock syndrome (TSS) results from the MHC class II presentation of bacterial superantigens, most commonly toxic shock syndrome-1 (TSST-1), to specific TCR Vbeta-bearing T cells. This superantigen-induced stimulation of whole T cell subsets leads to the exuberant cytokine production that in turn causes the shock syndrome. Since T cell activation and cytokine production are known to be dependent upon costimulatory signals, we reasoned that interfering with costimulation could effect TSS outcome. To test that hypothesis, we evaluated the effect of CTLA4Ig, a fusion protein known to block costimulatory signaling, on TSST-1-induced responses. CTLA4Ig not only blocked TSST-1-stimulated T cell proliferation by 90% in vitro, it also strikingly ameliorated TSST-1 induced TSS in vivo. While all mice co-administered TSST-1 and control Ig died, 75% of the CTLA4Ig plus TSST-1-treated mice survived. This salutary CTLA4Ig effect correlated with markedly diminished TSST-1 induced serum levels of TNF-alpha and IFN-gamma, but TSST-1-triggered IL-2 release was not affected. Surprisingly, while CTLA4Ig treatment group survivors remained sensitive to TSS induced by an unrelated superantigen (staphylococcal enterotoxin B), they were completely resistant to a second TSST-1 challenge. Furthermore, this TSST-1 resistance could be transferred to naive C57BL/6 mice using CD8+ T cells from CTLA4Ig plus TSST-1-primed mice. These data suggest several novel interpretations: 1) that the release of TNF-alpha and IL-2 have a different costimulatory signal dependence in vivo, 2) that the TSS resistance conferred by CTLA4Ig was superantigen specific, and 3) that the delayed and transferable resistance to TSST-1 was due, at least in part, to CD8+ T cells with suppressor function.

Electron microscopic characteristics of actinomycetic agents having aetiological association with human leprosy and epizootic ulcerative syndrome of fish

The transmission electron microscopic (TEM) studies of the human leprosy derived chemoautotrophic nocardio-form (CAN) bacteria and EUS derived CAN bacteria showed presence of double contoured cell-walls consisting of an electron transparent and a dense layer. The fibrillar structures on the surface of these CAN bacterial cells also suggested their similarity to the human tissue derived Mycobacterium leprae cells. These EM studies further revealed mycelial and coccoid bodies in all these bacteria as was observed originally.

Protection against lethal toxic shock by targeted disruption of the CD28 gene

Toxic shock syndrome (TSS) is a multi system disorder resulting from superantigen-mediated cytokine production. Nearly 90% of the clinical cases of TSS arise due to an exotoxin, toxic shock syndrome toxin-1 (TSST-1), elaborated by toxigenic strains of Staphylococcus aureus. It is clearly established that besides antigen-specific signals a variety of costimulatory signals are required for full T cell activation. However, the nature and potential redundancy of costimulatory signals are incompletely understood, particularly with regards to superantigen-mediated T cell activation in vivo. Here we report that CD28-deficient mice (CD28-/-) are completely resistant to TSST-1-induced lethal TSS while CD28 (+/-) littermate mice were partially resistant to TSST-1. The mechanism for the resistance of the CD28 (-/-) mice was a complete abrogation of TNF-alpha accumulation in the serum and a nearly complete (90%) impairment of IFN-gamma secretion in response to TSST-1 injection. In contrast, the serum level of IL-2 was only moderately influenced by the variation of CD28 expression. CD28 (-/-) mice retained sensitivity to TNF-alpha as demonstrated by equivalent lethality after cytokine injection. These findings establish an essential requirement for CD28 costimulatory signals in TSST-1-induced TSS. The hierarchy of TSST-1 resistance among CD28 wild-type (CD28+/+), CD28 heterozygous (CD28+/-), and CD28-/- mice suggests a gene-dose effect, implying that the levels of T cell surface CD28 expression critically regulate superantigen-mediated costimulation. Finally, as these results demonstrate the primary and non-redundant role of CD28 receptors in the initiation of the in vivo cytokine cascade, they suggest therapeutic approaches for superantigen-mediated immunopathology.

The role of CD28 costimulation in immune-mediated responses against mouse mammary tumor viruses

Infectious mouse mammary tumor viruses (MMTV) encode superantigens (SAg) which, when presented in association with permissive class II MHC molecules, are recognized by those T cells that express appropriate TCRs. Recent findings have indicated that expression of a permissive MHC class II product and of a specific TCR are also critical to susceptibility of newborn mice to infection with milk-borne MMTV, suggesting that SAg-mediated T cell activation may play a facilitating role in viral infection. Because effective Ag-specific T cell activation can require costimulatory signals in addition to TCR-mediated recognition, the role of the CD28 costimulatory receptor was analyzed in responses of neonatal and adult mice to MMTV challenge. Mice that were deficient in CD28 expression as a result of gene targeting were compared with CD28-intact littermates. In response to parenteral challenge with MMTV, CD28-deficient adult mice exhibited reduced expansion of MMTV SAg-reactive T cells in draining LNs, decreased cytokine production, and decreased B cell activation and Ig secretion. These results indicate that optimal T and B cell responses to MMTV challenge, as reflected in the parameters measured, are CD28 dependent. In contrast, CD28 absence did not impair TCR-V beta-specific clonal deletion induced by neonatal exposure to MMTV. Further, analysis of susceptibility to viral infection in neonatally exposed mice revealed that CD28 deficiency did not interfere with SAg-dependent MMTV infection. Failure to identify CD28 dependence of MMTV infection suggests either the absence of a costimulatory requirement in the events that lead to viral infection or a redundancy in costimulatory signals that support infection.

The role of CD28 costimulation in immune-mediated responses against mouse mammary tumor viruses

Infectious mouse mammary tumor viruses (MMTV) encode superantigens (SAg) which, when presented in association with permissive class II MHC molecules, are recognized by those T cells that express appropriate TCRs. Recent findings have indicated that expression of a permissive MHC class II product and of a specific TCR are also critical to susceptibility of newborn mice to infection with milk-borne MMTV, suggesting that SAg-mediated T cell activation may play a facilitating role in viral infection. Because effective Ag-specific T cell activation can require costimulatory signals in addition to TCR-mediated recognition, the role of the CD28 costimulatory receptor was analyzed in responses of neonatal and adult mice to MMTV challenge. Mice that were deficient in CD28 expression as a result of gene targeting were compared with CD28-intact littermates. In response to parenteral challenge with MMTV, CD28-deficient adult mice exhibited reduced expansion of MMTV SAg-reactive T cells in draining LNs, decreased cytokine production, and decreased B cell activation and Ig secretion. These results indicate that optimal T and B cell responses to MMTV challenge, as reflected in the parameters measured, are CD28 dependent. In contrast, CD28 absence did not impair TCR-V beta-specific clonal deletion induced by neonatal exposure to MMTV. Further, analysis of susceptibility to viral infection in neonatally exposed mice revealed that CD28 deficiency did not interfere with SAg-dependent MMTV infection. Failure to identify CD28 dependence of MMTV infection suggests either the absence of a costimulatory requirement in the events that lead to viral infection or a redundancy in costimulatory signals that support infection.

Immunotherapy of far-advanced lepromatous leprosy patients with low-dose convit vaccine along with multidrug therapy (Calcutta trial)

This report describes a promising mode of treatment of lepromin-unresponsive, far-advanced, lepromatous (LL) leprosy patients with antileprosy vaccines as an adjunct to multidrug therapy (MDT). The Trial Groups included 50 highly bacilliferous, lepromin-negative, untreated LL patients. They were given MDT for 2 years. Of them, 30 patients were administered a mixed antileprosy vaccine containing killed Mycobacterium leprae of human origin plus M. bovis BCG. The remaining 20 patients were given M. bovis BCG. Depending on the severity of lepromin unresponsiveness, they were given one to six inoculations at 3-month intervals. Another 20 similar LL patients were taken in the Control Group. They were given only MDT for 2 years. From the start of the study, all patients belonging to the Trial and Control Groups were followed every 3 months for clinical, bacteriological and immunological outcomes. Within 2 years all 50 patients of the Trial Groups and 19 of the 20 patients of the Control Group became clinically inactive and bacteriologically negative. However, the clinical cure and the falls of the bacterial and morphological indexes were much faster in those patients receiving the mixed vaccine therapy than in those patients who were given BCG plus MDT or only MDT. The immunological improvements in the patients of the Trial and Control Groups were assessed by: a) lepromin testing at the beginning of the study and at 3-month intervals and also by b) the in vitro leukocyte migration inhibition (LMI) test at both the beginning and end of the study. As the patients were given more and more vaccinations, the incidence of lepromin conversion increased, more so in the patients receiving the mixed vaccine. Thus, 63%, 15% and 5% of the patients became lepromin positive in those patients receiving the mixed vaccine, BCG, and MDT only, respectively. Lamentably, the vaccine-induced lepromin positivity was temporary and faded away within several months. At the beginning of the study, the LMI test against specific M. leprae antigen was negative in all patients of both the Trial and Control Groups. After the end of the chemo-immunotherapy schedule, the LMI test became positive in 50% and 20% of LL patients receiving the mixed vaccine and BCG, respectively. None of the Control Group could show LMI positivity after completion of the MDT schedule. These results show that treatment of LL patients with the mixed vaccine and MDT could quickly reverse the clinical course of the disease, remove immunologic anergy in some patients, and induce a rapid decrease in the bacterial load in them.

Macrophage-T cell interaction in murine salmonellosis: selective down-regulation of ICAM-1 and B7 molecules in infected macrophages and its probable role in cell-mediated immunity

Vaccine development and understanding of cellular immune modulatory mechanisms in salmonella infections have been impeded due to the paucity of data on antigens capable of eliciting effective immune responses. The present study was done to evaluate the efficacy of five major purified salmonella antigens (porins, pili, flagella, outer membrane proteins and heat shock proteins) in modulating T cell-macrophage interactions which play a central role in resistance to and recovery from infection with several intracellular pathogens, including salmonella. The results showed that the T cells recovered 10 days post-immunization (D10 T cells) from mice immunized with porins and outer membrane proteins showed maximum proliferation in the presence of macrophages incubated with dead bacteria; however, this response was decreased when T cells were co-cultured with live Salmonella typhimurium-infected macrophages. Delayed-type hypersensitivity responses, as measured by increased footpad thickness at 24 h, though induced effectively by porins, pili and flagella, were completely abrogated when D10 T cells were pre-incubated with macrophages infected with live bacteria. The phagocytic and bactericidal ability of normal macrophages, when grown in presence of T cell supernatants, was not influenced by the immunizing agents, but T cell supernatants obtained from mice immunized with porins and heat-shock protein triggered increased bactericidal activity. Further, the expression of the co-stimulatory molecules ICAM-1 and B7 increased with increasing bacteria (dead):macrophage ratio, but this expression was down-regulated upon incubation with live bacteria.