Inducing systemic and mucosal immune responses to B-T construct of F1 antigen of Yersinia pestis in microsphere delivery.

Plague is a zoonotic disease caused by Yersinia pestis, an etiological agent of pneumonic and bubonic plague. There is a need for an improved plague vaccine that may overcome the limitation of presently available whole cell vaccine. An alternative approach described here, is the use of protective epitopes from immunodominant antigen of Y. pestis. One such antigen is the F1 antigen, a major envelope and virulent protein that possess antiphagocytic and anti-microbial properties. The present study was aimed to develop a peptide-based vaccine, based upon the constructs made between B and T cell epitopes of F1 antigen of Y. pestis. The immunogenicity, IgG subclass pattern, affinity, avidity and in vivo protective efficacy of the antibodies generated for different B-T constructs were studied in murine model using microsphere as the delivery vehicle. The mode of immunization was both intranasal and intramuscular, with single and multiple doses of immunization, respectively. Intranasal immunization generated consistent high titre and long lasting immune response both for IgG and IgA in sera and sIgA in washes while intramuscular route generated peak IgG levels in sera only. The IgG isotypic levels pattern showed higher IgG2a/IgG2b levels in intranasal route while mixed isotypic levels of IgG1, IgG2a/IgG2b were observed in intramuscular route. The affinity and relative avidity of antibodies showed best results with intranasal route as compared to the intramuscular route. The specific activity measurement (IgG/IgA content) in sera and washes were well correlated with the antibody levels. Finally, in vivo protective studies showed that B1T1 and B2T1 conjugates protected the mice till day 15 while rest of the conjugates showed poor protection.

Enhanced mucosal and systemic immune response with intranasal immunization of mice with HIV peptides entrapped in PLG microparticles in combination with Ulex Europaeus-I lectin as M cell target.

The predominant route of HIV infection is through the sexual transmission via M cells. Most of the peptide and protein vaccines show poor transport across the epithelial barrier and are commonly administered by parenteral route. In the present study four HIV peptides from envelope (gp 41-LZ (leucine zipper), gp 41-FD (fusion domain) and gp120-C2) and regulatory (Nef) region in poly lactic-co-glycolide (PLG) micro-particle delivery were evaluated in mice of outbred and with different genetic background to compare immune response versus MHC restriction. Out of the combinational and single routes of immunization attempted, the single route maintained the IgG, IgA and sIgA in sera and washes for longer duration as compared to combinational routes in which the response was declined. The study demonstrated that single intranasal immunization offered significantly higher immune response (p<0.05) over oral and rectal mucosal routes in terms of inducing systemic as well as mucosal response. Also, the specific activity measurement of IgA and IgG in sera and sIgA in washes were correlating to the antibody titers. However, the intramuscular route of immunization generated systemic response only. The entrapment of plant lectin UEA-1 a ligand specific for M cells in micro-particle further enhanced the immune response in all the mucosal routes. The IgG isotypes generated were of IgG1 and IgG2a/2b in sera for all the peptides. The T cell proliferation response study with and without UEA-1 lectin in micro-particles showed significantly high (p<0.05) stimulation index (SI) with intranasal immunization for all the peptides from cells collected from spleen (SP), peyer's patches (PP) and lamina propria (LP) with SI in the order LP cells>PP>or=SP. The cytokine measurement profile of IL-2, IFN-gamma and IL-6 and low levels of IL-4 in the cultural supernatants of SP, PP and LP showed mixed CD4(+) Th1 and Th2 immune response. The p24 assay showed high percent inhibition of HIV-IIIB virus with sera and washes obtained from intranasal route. Thus, overall the study highlighted the combination of UEA-1 lectin with HIV peptides in micro-particles through intranasal immunization generated systemic as well as mucosal immune response.

Expression of costimulatory molecules (CD80, CD86, CD28, CD152), accessory molecules (TCR alphabeta, TCR gammadelta) and T cell lineage molecules (CD4+, CD8+) in PBMC of leprosy patients using Mycobacterium leprae antigen (MLCWA) with murabutide and T cell peptide of Trat protein.

In leprosy, cell-mediated immunity (CMI) is more significant than humoral response to eliminate intracellular pathogen. T cell defect is a common feature in lepromatous leprosy (LL) patients as compared to tuberculoid type (TT) patients. For efficient initiation of CD4+, T cell response requires T cell receptor (TCR) activation and costimulation provided by molecules on antigen-presenting cells (APC) and their counter receptors on T cells. In our previous study, the defective T cell function in LL patients was restored to a proliferating state with the release of TH1 type cytokines using mycobacterial antigen(s) with two immunomodulators (Murabutide (MDP-BE) and T cell epitope of Trat protein of Escherichia coli) by presenting the antigen in particulate form in vitro to PBMC derived from leprosy patients. This observation prompted us to study the expression of the costimulatory molecules (CD80, CD86, CD28, CD152), other accessory molecules (TCR alphabeta/gammadelta) and T cell lineage molecules (CD4+ and CD8+) during constitutive and activated state of peripheral blood mononuclear cells (PBMC) derived from normal and leprosy individuals using different formulations of Mycobacterium leprae total cell wall antigen (MLCWA), Trat and MDP-BE using flow cytometric analysis. An increased surface expression of CD80, CD86 and CD28 but decreased CD152 expression was observed when PBMC of normal, BT/TT (tuberculoid) and BL/LL (lepromatous) patients were stimulated in vitro with MLCWA+MDP-BE+Trat peptide using liposomal mode of antigen delivery, while opposite results were obtained with the antigen alone. Antibody inhibition study using antihuman CD80 or CD86 completely abolished the T cell lymphoproliferation, thereby reconfirming the importance of these costimulatory molecules during T cell activation/differentiation. Though the liposome-entrapped antigen formulation has no effect on expression of alphabeta/gammadelta T cell receptor, the constitutive levels of TCR gammadelta were high in lepromatous patients. Thus, TCR bearing gammadelta appears to have a negligible regulatory role in peripheral blood of leprosy patients. The percentage of cells positive for CD4+ are increased in inducible state in all the three groups, while CD8+-positive cells were decreased in LL patients, thereby reconfirming the fact that priming of CD4+ cells are necessary for producing final effector functions. Lastly, intracellular cytokine staining experiment indicated that CD4+ cells are the major producers of IFN-gamma but not NK cells. The study highlights the reversal of T cell anergy especially in lepromatous patients through the modulation of costimulatory molecule expression under the influence of Th1 cytokines, i.e., IL-2 and IFNgamma.

Blood lead levels and risk factors for lead toxicity in children from schools and an urban slum in Delhi.

This cross-sectional study was conducted to estimate the mean blood lead levels (BLL) and prevalence of lead toxicity in a representative sample of schoolchildren and children residing in an urban slum. In addition, the association of potential environmental risk factors with elevated BLL was studied. Children aged 4-6 years were selected from schools of the South zone of Delhi (n = 125) and from an urban slum (n = 65). Risk factors were recorded using a pre-tested questionnaire and blood lead and zinc protoporphyrin (ZPP) levels were estimated. The mean BLL was 7.8 microg/dl (SD 3.9) and the proportion of children with blood lead > or = 10 microg/dl was 18.4 per cent. Distance of the residence or school from a main road appeared to be associated with higher blood lead concentrations, but these differences were not statistically significant. In our setting, vehicular pollution may be a major contributing factor in lead contamination of the environment.

Comparing modified and plain peptide linked enzyme immunosorbent assay (ELISA) for detection of human immunodeficiency virus type-1 (HIV-1) and type-2 (HIV-2) antibodies.

Serological diagnosis of human immunodeficiency virus (HIV) based on detection of HIV antibodies is one of the easiest, cheapest and simplest assay. Synthetic peptides corresponding to immunodominant regions of envelope glycoprotein (gp41, V3 loop for HIV-1 and gp36 for HIV-2) were used in the present study, to detect the anti-HIV antibodies in sera of Sexually Transmitted Diseases (STD), Tuberculosis (TB), Anti-Natal Care (ANC) patients. About 550 serum samples were tested using Enzyme Linked Immunosorbent Assay (ELISA) technique. The human sera positive for antibody to HIV-1 and HIV-2, reacted to different degrees with these peptides when used as a plain peptide with or without CGG motif/biotin motif at the amino terminus. The selected sequences are of Indian strain with 'C' serotype. The results showed a 100% sensitivity and specificity for V3 loop peptide and 98% sensitivity and specificity for gp41 peptide containing CGG moiety while the plain peptides showed similar sensitivities but low specificity's, i.e. 98% for V3 loop peptide and 42% for gp41 peptide when reacted with HIV-1 positive sera. The presence of biotin at the amino terminus did not provide any beneficial effect in increasing the sensitivity although the specificity was enhanced for both the peptide sequences, i.e. gp41 and V3 loop peptide. Furthermore, the gp36 peptide containing CGG moiety detected the HIV-2 sera with 100% sensitivity and 98% specificity while the sensitivity and specificity of gp36 plain peptide was reduced to 98 and 90%. Thus the study overall highlighted the importance of synthetic peptides containing CGG moiety as a capture antigen in detecting both HIV-1 & 2 sera using an indigenously built ELISA system which is simple, cheap, sensitive and cost effective for rural areas.

Plumbism--a mimicker of common childhood symptoms.

Lead poisoning is a preventable entity that can affect almost every system of the body. Its toxic effects range from subtle common childhood symptoms to even death. In a prospective study forty six children with at least one symptom compatible with plumbism were enrolled after screening patients attending medical services at AIIMS. The work-up included a detailed clinical history and examination including intelligence quotient (IQ) and behaviour. Blood lead levels were estimated in all with due precautions. Their ages ranged from 2.5 to 18 years and M:F ratio was 2:1. The common symptoms included unexplained recurrent colic (39), anorexia (21), sporadic vomiting and constipation (13), pigmented gum lines (11), growth failure (11), history of pica (9) etc. None of the children had acceptable blood lead levels (< 10 micrograms/dl). Ninety three per cent children had levels > 20 micrograms/dl and 47.8% had > 45 micrograms/dl. Statistically significant correlation with blood lead levels was seen with most symptoms. Plumbism can mimic common childhood illnesses and should be investigated in children with a clinically compatible profile. Community awareness with regard to pica reduction may be an important preventive measure. This silent epidemic needs to be aggressively tackled by a multipronged approach.