Biomedical subjects

Manmohan Singh

Publications and source records attributed to Manmohan Singh.

At least 19 recordsLinked to original sources

PubMed2006

A modified process for preparing cationic polylactide-co-glycolide microparticles with adsorbed DNA.

We have previously shown that cationic polylactide-co-glycolide (PLG) microparticles can be effectively used to adsorb DNA and generate potent immune responses in vivo. We now describe a modified and easier process containing a single lyophilization step to prepare these cationic PLG microparticles with adsorbed DNA. Cationic PLG microparticle formulations with adsorbed DNA were prepared using a modified solvent evaporation technique. Formulations with a fixed CTAB content and DNA load were prepared. The loading efficiency and 24h DNA release was evaluated for each formulation and compared to the earlier method of preparation. Select formulations were tested in vivo. The modified cationic PLG microparticle preparation method with a single lyophilization step, showed comparable physico-chemical behaviour to the two lyophilization steps process and induced comparable immune. The modified process with a single lyophilization step is a more practical process and can be utlized to prepare cationic PLG microparticles with adsorbed DNA on a large scale.

Adsorption↗

PubMed2006

A practical approach to the use of nanoparticles for vaccine delivery.

The objective of this work was to obtain a nanoparticle formulation that could be sterile filtered, lyophilized, and resuspended to the initial size with excipients appropriate for use as a vaccine formulation. Poly(lactide-co-glycolide) (PLG) polymers were used to create nanoparticles ranging in size from 110 to 230 nm. Protein antigens were adsorbed to the particles; the protein-nanoparticles were then lyophilized with the excipients. Vaccine compatible excipient combinations of sugars alone, surfactants alone, and sugars and surfactants were tested to find conditions where initial particle size was recovered. Sterile filtration of smaller nanoparticles led to minimal PLG losses and allowed the particle preparation to be a nonaseptic process. We found that the smaller nanoparticles of size approximately 120 nm required higher surfactant concentration to resuspend postlyophilization than slightly larger ( approximately 220 nm) particles. To resuspend 120 nm nanoparticles formulations of poly(vinyl alcohol) (PVA) with sucrose/mannitol or dioctyl sodium sulfosuccinate (DSS) with trehalose/mannitol were sufficient. The protein-nanoparticles resuspension with the same excipients was dependent on the protein and protein loading level. The nanoparticle formulations in vivo were either similar or had enhanced immunogenicity compared to aluminum hydroxide formulations. A lyophilized nanoparticle formulation with adsorbed protein antigen and minimal excipients is an effective vaccine delivery system.

Animals↗

PubMed2006

Traumatic middle meningeal artery aneurysm causing intracerebral hematoma: a case report and review of literature.

BACKGROUND: Traumatic aneurysms of middle meningeal artery (MMA) are rare. Traumatic MMA aneurysms usually present with extradural hematomas, whereas intradural intraparenchymal hematomas are exceedingly rare. CASE DISCUSSION: We report a 30-year-old man who presented 1 year after head injury with spontaneous right frontal intraparenchymal hematoma. Investigations revealed a MMA pseudoaneurysm, which was successfully treated surgically. CONCLUSION: Traumatic MMA pseudoaneurysm producing intracerebral hematoma (ICH) is rare and can be listed as a cause of spontaneous acute ICH.

Adult↗

PubMed2006

Microparticle-based technologies for vaccines.

Microparticles have been effectively used for many years as delivery systems for drugs and therapeutic proteins. Their application to the delivery of vaccines is not as extensive, but is growing. Utility has been demonstrated for the delivery of various types of vaccines (e.g., recombinant proteins, plasmid DNA, and peptides) and other vaccine components (e.g., immune potentiators). With respect to delivery of immune potentiators, synergistic effects are often observed whereby much more potent immune responses are induced with a combination than with either component alone. Hence, the prospects for broad application of microparticle-based delivery systems for vaccines are excellent.

Adjuvants, Immunologic↗

PubMed2006

Hepatitis C virus polyprotein vaccine formulations capable of inducing broad antibody and cellular immune responses.

Although approximately 3 % of the world's population is infected with Hepatitis C virus (HCV), there is no prophylactic vaccine available. This study reports the design, cloning and purification of a single polyprotein comprising the HCV core protein and non-structural proteins NS3, NS4a, NS4b, NS5a and NS5b. The immunogenicity of this polyprotein, which was formulated in alum, oil-in-water emulsion MF59 or poly(dl-lactide co-glycolide) in the presence or absence of CpG adjuvant, was then determined in a murine model for induction of B- and T-cell responses. The addition of adjuvants or a delivery system to the HCV polyprotein enhanced serum antibody and T-cell proliferative responses, as well as IFN-gamma responses, by CD4+ T cells. The antibody responses were mainly against the NS3 and NS5 components of the polyprotein and relatively poor responses were elicited against NS4 and the core components. IFN-gamma responses, however, were induced against all of the individual components of the polyprotein. These data suggest that the HCV polyprotein delivered with adjuvants induces broad B- and T-cell responses and could be a vaccine candidate against HCV.

Adjuvants, Immunologic↗

PubMed2006

Intranasal delivery of vaccines against HIV.

HIV poses a serious health threat in the world. Mucosal transmission of HIV through the genitourinary tract may be the most important route of transmission. Intranasal immunisations induce vaginal and systemic immune responses. Various protein-, DNA- and RNA-based immunopotentiating adjuvants/delivery systems and live bacterial and viral vectors are available for intranasal immunisations, and these systems may differ in their ability to induce a specific type of immune response (e.g., a cytotoxic T cell versus an antibody response). As the protection against HIV may require both cytotoxic T cell and antibodies, a combination of adjuvants/delivery systems for combinations of mucosal and parenteral immunisations may be required in order to develop a protective anti-HIV vaccine.

AIDS Vaccines↗

PubMed2006

Polylactide-co-glycolide microparticles with surface adsorbed antigens as vaccine delivery systems.

Several groups have shown that vaccine antigens can be encapsulated within polymeric microparticles and can serve as potent antigen delivery systems. We have recently shown that an alternative approach involving charged polylactide co-glycolide (PLG) microparticles with surface adsorbed antigen(s) can also be used to deliver antigen into antigen presenting cell (APC). We have described the preparation of cationic and anionic PLG microparticles which have been used to adsorb a variety of agents, which include plasmid DNA, recombinant proteins and adjuvant active oligonucleotides. These PLG microparticles were prepared using a w/o/w solvent evaporation process in the presence of the anionic surfactants, including DSS (dioctyl sodium sulfosuccinate) or cationic surfactants, including CTAB (hexadecyl trimethyl ammonium bromide). Antigen binding to the charged PLG microparticles was influenced by several factors including electrostatic and hydrophobic interactions. These microparticle based formulations resulted in the induction of significantly enhanced immune responses in comparison to alum. The surface adsorbed microparticle formulation offers an alternative and novel way of delivering antigens in a vaccine formulation.

Adjuvants, Immunologic↗

PubMed2006

Economics of head injuries.

Head injuries account for significant proportion of neurosurgical admissions and bed occupancy. Patients with head injuries also consume significant proportions of neurosurgical resources. A prospective 6-month study has been carried out to evaluate the expenditure incurred on head injury patients in a modern neurosurgical center equipped with state of the art infrastructure. Costing areas included wages / salaries of health care personnel, cost of medicines / surgical items / crystalloids, general store items, stationary, all investigation charges, equipment cost, overhead building cost, maintenance cost, electricity and water charges and cost of medical gases, air conditioning and operation theatre expenses. Expenditure in each area was calculated and apportioned to each bed. The statistical analysis was done using X2 test. The cost of stay in ward was found to be Rs. 1062 / bed / day and in neurosurgical ICU Rs. 3082 / bed / day. The operation theatre cost for each surgery was Rs. 11948. The cost of hospital stay per day for minor, moderate and severe head injury group was found to be Rs. 1921, Rs. 2569 and Rs. 2713 respectively. The patients who developed complications, the cost of stay per day in the hospital were Rs. 2867. In the operative group, the cost of hospital stay per day was Rs. 3804. The total expenditure in minor head injury was Rs. 7800 per patient, in moderate head injury was Rs. 22172 per patient, whereas in severe head injury, it was found to be Rs. 32852 per patient. Patients who underwent surgery, the total cost incurred was Rs. 33100 per operated patient.

Cost of Illness↗

PubMed2006

Comparative analysis of diagnostic accuracy of different brain biopsy procedures.

BACKGROUND: Image-guided procedures such as computed tomography (CT) guided, neuronavigator-guided and ultrasound-guided methods can assist neurosurgeons in localizing the intraparenchymal lesion of the brain. However, despite improvements in the imaging techniques, an accurate diagnosis of intrinsic lesion requires tissue sampling and histological verification. AIMS: The present study was carried out to examine the reliability of the diagnoses made on tumor sample obtained via different stereotactic and ultrasound-guided brain biopsy procedures. MATERIALS AND METHODS: A retrospective analysis was conducted of all brain biopsies (frame-based and frameless stereotactic and ultrasound-guided) performed in a single tertiary care neurosciences center between 1995 and 2005. The overall diagnostic accuracy achieved on histopathology and correlation with type of biopsy technique was evaluated. RESULTS: A total of 130 cases were included, which consisted of 82 males and 48 females. Age ranged from 4 to 75 years (mean age 39.5 years). Twenty per cent (27 patients) were in the pediatric age group, while 12% (16 patients) were >or= 60-years of age. A definitive histological diagnosis was established in 109 cases (diagnostic yield 80.2%), which encompassed 101 neoplastic and eight nonneoplastic lesions. Frame-based, frameless stereotactic and ultrasound-guided biopsies were done in 95, 15 and 20 patients respectively. Although the numbers of cases were small there was trend for better yield with frameless image-guided stereotactic biopsy and maximum diagnostic yield was obtained i.e, 87% (13/15) in comparison to conventional frame-based CT-guided stereotactic biopsy and ultrasound-guided biopsy. CONCLUSIONS: Overall, a trend of higher diagnostic yield was seen in cases with frameless image-guided stereotactic biopsy. Thus, this small series confirms that frameless neuronavigator-guided stereotactic procedures represent the lesion sufficiently in order to make histopathologic diagnosis.

Adolescent↗

PubMed2005

Encapsulation of the immune potentiators MPL and RC529 in PLG microparticles enhances their potency.

PURPOSE: Monophosphoryl lipid A (MPL) and the synthetic LPS mimetic RC529, encapsulated in poly(lactide-co-glycolide) (PLG) microparticles, were evaluated as immune potentiators in the presence of either HIV-1 gp120 protein or antigen from Neisseria meningitidis serotype B (Men B). The immunogenicity of these formulations was evaluated in mice and compared to CpG containing oligonucleotide. This work was done as part of an ongoing effort to enhance the potency of vaccine candidates against HIV and Men B. METHODS: Microparticles were made by a solvent evaporation method. Blank microparticles as well as microparticles with encapsulated MPL or RC529 were made using the PLG polymer RG503 and the ionic surfactant Dioctylsulfosuccinate by the water-in-oil-in-water emulsion technique. Antigens from HIV-1 and Men B were adsorbed on the surface of these anionic microparticles and the final formulations characterized for protein loading, release, and integrity. The formulations were then tested in mice for their ability to elicit antibodies and bactericidal activity in comparison with CpG containing oligonucleotide. RESULTS: We have found that adding soluble immune potentiators to Men B antigen formulated on PLG microparticles significantly enhanced the immune response to a level comparable to that obtained using CpG. In a separate study, we found that encapsulating MPL or RC529 in PLG microparticles further enhanced the response in comparison to soluble CpG, which is our control group. Similarly, adding soluble immune potentiators to gp120 antigen formulated on PLG microparticles resulted in a significant enhancement of the immune response. Moreover, delivering MPL or RC529 encapsulated in PLG microparticles with gp120 adsorbed on PLG microparticles, resulted in even further enhancement of serum titers over those obtained with soluble immune potentiators. These titers were comparable to or greater than those obtained with soluble CpG, the control group. This effect was observed for both antigens regardless of whether or not the immune potentiator and the antigen were used with the same or with separate particles. In conclusion, the advantages of encapsulating MPL and RC529 lie not only in the enhanced immune response they elicit, but also in the convenience of handling these relatively insoluble compounds, and flexibility in vaccine design. The fact that MPL and RC529 are readily soluble in methylene chloride used for the manufacturing of PLG microparticles makes it easy to avoid solubility issues. Moreover, formulating antigen and immune potentiator with the same particle offers an attractive approach to vaccine delivery.

Adjuvants, Immunologic↗

PubMed2005

A preliminary evaluation of alternative adjuvants to alum using a range of established and new generation vaccine antigens.

Although alum is the most commonly used vaccine adjuvant, it has some limitations for use with the next generation recombinant antigens. We explored the use of alternative adjuvant formulations (poly lactide co-glycolide (PLG) microparticles, MF59 emulsion, CAP and l-tyrosine suspension) in comparison with five different vaccine antigens--namely, diphtheria toxoid (DT), tetanus toxoid (TT), HBsAg, Men C conjugate and MB1. The results indicated that although alum was optimal for bacterial toxoid based vaccines, it was not highly potent for MB1, Men C or HBsAg antigens. MF59 emulsion stood out as a good alternative to alum for TT, HBsAg, MB1 and Men C vaccines. On the other hand l-tyrosine suspension and CAP did not enhance immune responses over alum with most antigens. PLG microparticles were comparable or better than alum with both MB1 and Men C conjugate vaccine. The study indicates that it is possible to replace alum with other adjuvant formulations like MF59 and PLG and maintain and/or improve immune responses with some vaccine antigens.

Adjuvants, Immunologic↗

PubMed2005

An investigation of the factors controlling the adsorption of protein antigens to anionic PLG microparticles.

This work examines physico-chemical properties influencing protein adsorption to anionic PLG microparticles and demonstrates the ability to bind and release vaccine antigens over a range of loads, pH values, and ionic strengths. Poly(lactide-co-glycolide) microparticles were synthesized by a w/o/w emulsification method in the presence of the anionic surfactant DSS (dioctyl sodium sulfosuccinate). Ovalbumin (OVA), carbonic anhydrase (CAN), lysozyme (LYZ), lactic acid dehydrogenase, bovine serum albumin (BSA), an HIV envelope glyocoprotein, and a Neisseria meningitidis B protein were adsorbed to the PLG microparticles, with binding efficiency, initial release and zeta potentials measured. Protein (antigen) binding to PLG microparticles was influenced by both electrostatic interaction and other mechanisms such as van der Waals forces. The protein binding capacity was directly proportional to the available surface area and may have a practical upper limit imposed by the formation of a complete protein monolayer as suggested by AFM images. The protein affinity for the PLG surface depended strongly on the isoelectric point (pI) and electrostatic forces, but also showed contributions from nonCoulombic interactions. Protein antigens were adsorbed on anionic PLG microparticles with varying degrees of efficiency under different conditions such as pH and ionic strength. Observable changes in zeta potentials and morphology suggest the formation of a surface monolayer. Antigen binding and release occur through a combination of electrostatic and van der Waals interactions occurring at the polymer-solution interface.

Adsorption↗

PubMed2005

CpG oligodeoxynucleotides adsorbed onto polylactide-co-glycolide microparticles improve the immunogenicity and protective activity of the licensed anthrax vaccine.

To reduce the biothreat posed by anthrax, efforts are under way to improve the protection afforded by vaccination. This work examines the ability of immunostimulatory CpG oligodeoxynucleotides (ODN) adsorbed onto cationic polylactide-co-glycolide (PLG) microparticles (CpG ODN-PLG) to accelerate and boost the protective immunity elicited by Anthrax Vaccine Adsorbed (AVA, the licensed human anthrax vaccine). The results indicate that coadministering CpG ODN-PLG with AVA induces a stronger and faster immunoglobulin G response against the protective antigen of anthrax than AVA alone. Immunized mice were protected from lethal anthrax challenge within 1 week of vaccination with CpG ODN-PLG plus AVA, with the level of protection correlating with serum immunoglobulin G anti-protective antigen titers.

Animals↗

PubMed2005

Enhanced potency of plasmid DNA microparticle human immunodeficiency virus vaccines in rhesus macaques by using a priming-boosting regimen with recombinant proteins.

DNA vaccines have been used widely in experimental primate models of human immunodeficiency virus (HIV), but their effectiveness has been limited. In this study, we evaluated three technologies for increasing the potency of DNA vaccines in rhesus macaques. These included DNA encoding Sindbis virus RNA replicons (pSINCP), cationic poly(lactide-co-glycolide) (PLG) microparticles for DNA delivery, and recombinant protein boosting. The DNA-based pSINCP replicon vaccines encoding HIV Gag and Env were approximately equal in potency to human cytomegalovirus (CMV) promoter-driven conventional DNA vaccines (pCMV). The PLG microparticle DNA delivery system was particularly effective at enhancing antibody responses induced by both pCMV and pSINCP vaccines and had less effect on T cells. Recombinant Gag and Env protein boosting elicited rapid and strong recall responses, in some cases to levels exceeding those seen after DNA or DNA/PLG priming. Of note, Env protein boosting induced serum-neutralizing antibodies and increased frequencies of gamma interferon-producing CD4 T cells severalfold. Thus, PLG microparticles are an effective means of delivering DNA vaccines in nonhuman primates, as demonstrated for two different types of DNA vaccines encoding two different antigens, and are compatible for use with DNA prime-protein boost regimens.

AIDS Vaccines↗

PubMed2005

The role of adjuvants in the development of mucosal vaccines.

It is well-established that most pathogens that cause infectious diseases enter the host via mucosal membranes of the respiratory, digestive and genital tracts. Some parenterally administered vaccines induce protection against mucosal pathogens. However, there is increasing evidence that mucosal protection is better afforded by mucosal vaccination, particularly for the induction of memory responses. Mucosal vaccines must pass several difficult hurdles before entering the host and inducing an effective and protective immune response. This review deals with present and past efforts in devising effective mucosal vaccines using delivery systems and immunopotentiating adjuvants for protein-based vaccines. The paper will conclude with the authors' opinion on how the field will or should progress in the future and what will be the required components of ideal future mucosal vaccines that can induce immunological memory.

Adjuvants, Immunologic↗

PubMed2004

Cationic microparticles are a potent delivery system for a HCV DNA vaccine.

We initially evaluated in mice the ability of naked DNA encoding intracellular forms of the E1E2 envelope proteins from HCV to induce antibody responses and compared the responses induced with the same plasmid adsorbed onto cationic poly (lactide co-glycolide) (PLG) microparticles. Although naked DNA was only able to induce detectable responses at the 100 microg dose level, making this approach impractical for evaluation in larger animals, PLG/DNA induced detectable responses at 10 microg. In addition, the PLG/DNA microparticles induced significantly enhanced responses to naked DNA when compared at the same dose level. Remarkably, PLG/DNA induced comparable responses to recombinant E1E2 protein adjuvanted with the emulsion MF59. Furthermore, PLG/DNA effectively primed for a booster response with protein immunization, while naked DNA did not. Therefore, PLG/DNA was selected for further evaluation in a non-human primate model. In a study in rhesus macaques, PLG/DNA induced seroconversion in 3/3 animals following three immunizations. Although the antibody responses appeared lower than those induced with recombinant protein adjuvanted with MF59, following a fourth dose, PLG/DNA and protein induced comparable responses. However, a single booster dose of recombinant protein administered to the animals previously immunized with PLG/DNA induced much higher responses. In addition, one of three animals immunized with PLG/DNA showed a cytotoxic T lymphocyte response in peripheral blood lymphocytes. In conclusion, cationic PLG microparticles with adsorbed HCV DNA generates potent immune responses.

Adjuvants, Immunologic↗

PubMed2004

Enhanced protective efficacy of a tuberculosis DNA vaccine by adsorption onto cationic PLG microparticles.

Immunization with plasmid DNA vectors represents a promising new approach to vaccination. It has been shown to elicit humoral and cellular immunity and protection in various infection models. Here, we assessed the immunogenicity and protective efficacy of a DNA vaccine vector encoding the antigen 85A (Ag85A) of Mycobacterium tuberculosis. Since intramuscular (i.m.) immunization with naked DNA requires considerable amounts of DNA in order to be effective, we evaluated a strategy to reduce the amount of DNA needed. To this end, we used Ag85A DNA adsorbed onto cationic poly(DL-lactide-co-glycolide) (PLG) microparticles and observed similar levels of protection against aerosol challenge in mice using doses of PLG-DNA two orders of magnitude lower than with naked DNA itself.

Adsorption↗

PubMed2004

Maintenance of long-term immunological memory by low avidity IgM-secreting cells in bone marrow after mucosal immunizations with cholera toxin adjuvant.

To understand the mechanisms involved in maintaining long-term immunological memory following mucosal immunizations, we determined the quality of serum hapten-specific immunoglobulins (Ig) and localized Ig-secreting cells (SC) of various isotypes in acute, persistent/resting memory and effector memory phases following oral versus intra-muscular (IM) immunizations. In the acute phase, both oral and IM immunizations induced high avidity Ig. However, in the persistent/resting memory phase, oral immunizations induced low avidity Ig while IM immunizations induced high avidity Ig. Following oral immunizations, in the persistent/resting memory phase, hapten-specific IgM titers in serum and IgM-SC in bone marrow (BM) dominated the immune response, suggesting an important role for IgM in the maintenance of memory.

Adjuvants, Immunologic↗