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11: Evaluating Recombinant DNA - Biology

11: Evaluating Recombinant DNA - Biology



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  • 11.1: Cloning DNA - Plasmid Vectors
    Many bacteria contain extra-chromosomal DNA elements called plasmids. These are usually small (a few 1000 bp), circular, double stranded molecules that replicate independently of the chromosome and can be present in high copy numbers within a cell. In the wild, plasmids can be transferred between individuals during bacterial mating and are sometimes even transferred between different species. Plasmids often carry genes for pathogenicity and drug-resistance.
  • 11.2: DNA Analysis - Gel Electrophoresis
    A solution of DNA is colorless, and except for being viscous at high concentrations, is visually indistinguishable from water. Therefore, techniques such as gel electrophoresis have been developed to detect and analyze DNA.

Purpose

The purpose of this prospective study was to evaluate the safety and effectiveness of recombinant human morphogenetic protein-2 (rhBMP-2) on an absorbable collagen sponge (ACS) compared with an autogenous bone graft when used for 2-stage maxillary sinus floor augmentation. The study assessed new bone formation, placement integration, and functional loading after 6 months and long term for 2 years.

Materials and Methods

A total of 160 subjects were randomized, enrolled, and followed from January 1999 to February 2004 at 21 centers in the United States. The subjects with less than 6 mm of native bone height were treated with 1.50 mg/mL rhBMP-2/ACS or with an autograft. The height and density measurements were quantified by computed tomography scans. Core biopsies were obtained at dental implant placement and used for histological analysis. Safety was evaluated by oral examinations, radiographs, serum chemistries, and hematology.

Results

A significant amount of new bone was formed by 6 months postoperatively in each group. The mean change in bone height in the rhBMP-2/ACS subjects was 7.83 ± 3.52 mm versus 9.46 ± 4.11 mm for the bone graft subjects. At 6 months after dental restoration, the induced bone in the rhBMP-2/ACS group was significantly denser than that in the bone graft group. No marked differences were found in the histologic parameters evaluated between the 2 groups. The new bone was comparable to the native bone in density and structure in both groups. The success rate for the rhBMP-2/ACS group was 79% (64 of 81 subjects), and 201 of 251 implants placed in the bone graft group and 199 of 241 implants placed in the rhBMP-2/ACS group were integrated, retained, and functional at 6 months after loading. No adverse events were deemed related to the rhBMP-2/ACS treatment. The autograft group was noted to have a 17% rate of long-term parasthesia, pain, or gait disturbance related to the bone graft harvest.

Conclusions

The results of our multicenter, randomized, prospective, clinical trial have shown the effectiveness and safety of rhBMP-2/ACS compared with bone graft for sinus floor augmentation. The study's primary endpoint was exceeded, and the implants placed in rhBMP-2/ACS and bone graft groups performed similarly after functional loading.


Introduction

The immune response against viral pathogens includes specific and non specific mechanisms. Cytokines are peptides which can play a role in the non specific immunity [1]. Interferon (IFN) is a kind of highly active multifunctional glycoprotein, and it is an important cytokine with a broad range of biological activities [2]. Interferon is a secretory glycoprotein produced by the biological cells when it is subjected to the influence of the virus or other inducing agent [3]. Interferon has many kinds of bioactivity, such as antiviral activity, immune regulation and so on [4]. Interferon is an important part of the body's defense system. Interferon has broad-spectrum resistance [5]. When interferon acts on the body's organic tissue cells, it can make it obtain the ability to resist a variety of viruses and microbes [6]. Interferon has strict selectivity for a somatic cell, and has a relative species specificity. But the specificity is relative, not absolute [7]. Interferon can be divided into type I and type II [8]. Interferon of type I is a product of many gene families, including 14-20 interferon α genes, 1 kind of interferon β gene interferon of type α contains only one family member, namely the interferon g [9]. Type I interferons are the most effective antiviral cytokines. Type I interferon genes are located on chromosome 9, and are segregated in a “modern” and an 𠇊ncestral” group with distinctive effects on the cells. Interferons α are represented by a large family of structurally related genes while the IFN-β is encoded by a single gene [1, 10, 11].

The meat and eggs of Coturnix were delicious in China and known as 𠇊nimal's ginseng”. Currently, the number of Coturnix raised is about 200 million in China, which is 1/5 of the world production. Coturnix is an important part of the economic animal production in China. But the occurrence of avian influenza and New-castle diseases posed a serious threat to the production of Coturnix. Establishing the Coturnix immune mechanism, looking for a new and efficient security immune route makes it necessary to breed Coturnix. By contrast, the research on animal interferon lags behind. There/This is still the main stay/subject? in basic research and clinical trials, and most concentrating on a few animals such as pigs, chicken, fish. But a big progress has been made in recent years. There are commercial interferon of pigs, dogs, chicken and recombinant interferon product coming to the market. However, there are very few research reports about the Coturnix interferon.


Clinical trials for improving TACE

The TACE procedure varies greatly among different physicians and clinical centers, and the technique and number of administrations for achieving maximum tumor regression and optimal outcome remains unclear. As such, many of the current clinical trials evaluating TACE aim to examine the use of various chemotherapeutic and embolizing agents to optimize the procedure, and there has also been considerable interest in combining targeted therapies with the TACE procedure [13]. For example, sorafenib, a multikinase inhibitor that is currently the sole systemic chemotherapeutic that is US FDA approved for HCC treatment, has also been of interest for use in combination with TACE. Sorafenib is known to inhibit VEGFR, which promotes angiogenesis and tumor cell survival and growth, and is activated by hypoxia. Since the TACE procedure itself relies on a combination of chemotherapy with the induction of a hypoxic tumor microenvironment to initiate tumor necrosis, there has been great interest in using sorafenib in combination with the TACE procedure to inhibit the activation of angiogenesis by TACE-induced hypoxia. However, a Phase II clinical trial, the SPACE study, examined the use of sorafenib plus TACE with doxorubicin drug-eluting beads and found no significant difference in time to progression in HCC patients compared with TACE alone [14]. A Phase III study investigating the use of sorafenib in combination with TACE found similar results [15].

A number of clinical trials have evaluated the use of TACE in combination with other targeted antiangiogenic agents, but most have been met with negative outcomes. For example, Phase III trials evaluating brivanib, a dual inhibitor of VEGFR and FGFR [16], and orantinib, an inhibitor of VEGFR and PDGFR [17], both failed to demonstrate improved overall survival with combination therapy. Two Phase II trials evaluated bevacizumab, an anti-VEGF monoclonal antibody, in combination with TACE, which demonstrated the use of bevacizumab to exhibit antitumor activity, thus warranting further studies [18,19], although no Phase III trials are currently underway.

There is also interest in evaluating the feasibility of gene-based therapy in combination with TACE, which has the advantage of localized delivery while reducing systemic toxicities, and has the potential to advance personalized medicine initiatives, by targeting individual tumor characteristics. Several previous clinical trials evaluating combined gene therapy and TACE approaches have shown mixed results, but a Phase II clinical trial evaluating recombinant adenovirus expressing human p53 tumor suppressor gene in combination with TACE ( <"type":"clinical-trial","attrs":<"text":"NCT02418988","term_id":"NCT02418988">> NCT02418988) and a Phase III clinical trial evaluating the antitumor recombinant human adenovirus type 5 in combination with TACE ( <"type":"clinical-trial","attrs":<"text":"NCT01869088","term_id":"NCT01869088">> NCT01869088) are currently ongoing [20]. Clinical trials evaluating pharmacological agents or gene therapy in combination with TACE are summarized in Table 1 .


2 Types of viral vaccines

There is a broad diversity of viral vaccines. Commercially available vaccines against viral pathogens can be classified into three general types: live attenuated vaccines inactivated vaccines and subunit vaccines (Fig. 1) [ 15 ]. Within this generally accepted classification, different technological approaches can be applied, giving rise to the design of several sub-types of vaccines.

2.1 Live attenuated vaccines

Live attenuated viral vaccines use live viruses and were the first type of vaccines to be used. Historically, live viruses were initially used through inoculation. Although inoculation procedures are still used in veterinary vaccination, for human use this is no longer the case. The only type of live viruses used for human vaccination are live attenuated (licensed) or vectored vaccines (under clinical development). There are several approaches to attenuate viruses. One of the most used procedures involves growing the viruses in foreign hosts, as animal cell cultures, where they replicate poorly. Several vaccines have been developed using this procedure including poliovirus, measles or rubella vaccines [ 8 ]. Today, live attenuated vaccines can be obtained through additional molecular strategies such as: reassortment (e.g. influenza and rotavirus) [ 16 ], mutation or deletion of viral genes (e.g. dengue virus) [ 17 ], or codon deoptimization (e.g. poliovirus) [ 18 ]. One concern related with live attenuated vaccines is the possibility of reversion into a virulent form, as seen for the first polio oral vaccine. In this context, inactivated vaccines provide safer alternatives to attenuated vaccines.

2.2 Inactivated vaccines

Inactivated vaccines are generated by killing or destroying the pathogen. This can be achieved by chemical means, using for example formalin or formaldehyde, or physically by heat or irradiation. Several inactivated viral vaccines are commercially available against, for example, influenza, rabies or poliovirus (Table 1). In addition to presenting a safer profile comparatively to attenuated viral vaccines, inactivated vaccines are also more stable. Although inactivated vaccines are quite effective for some pathogens, for others, they do not induce an effective and/or long-lasting immunity since they do not give rise to cytotoxic T cells immune response, which is important to efficiently fight intracellular pathogens as viruses. Because of that, multiple doses and adjuvants are often used [ 19 ].

Vaccine type Description Cells Status Ref.
Live/Attenuated Oral polio vaccine (OPV) – Attenuated vaccine produced by the passage of the virus through non-human cells Vero Licensed [ 119 ]
RotaTeq® – Pentavalent vaccine containing (five) live attenuated reassortant rotaviruses Vero Licensed [ 120 ]
Varilix® – Lyophilized preparation of attenuated virus derived from the Oka strain, vaccine against varicella MRC5 Licensed [ 121 ]
smallpox vaccine ACAM2000 – Attenuated vaccinia-based smallpox vaccine Vero Licensed [ 122 ]
Inactivated Imovax® – Monovalent vaccine containing inactivated rabies MRC5 Licensed [ 123 ]
Havrix® – Inactivated hepatitis A vaccine with formaldehyde MRC5 Licensed [ 124 ]
Inactivated polio vaccine (IPV) – Trivalent inactivated poliovirus Vero Licensed [ 125 ]
Optaflu® –Trivalent cell culture-derived influenza vaccine MDCK Licensed [ 90 ]
Subunit Protein Flublok® –Recombinant trivalent hemagglutinin (rHA) vaccine produced in insect cell culture using BEVs expresSF+ Licensed [ 22 ]
Glycoprotein B – recombinant truncated secreted form of gB CHO Phase II [ 126 ]
DEN1-80E – Adjuvanted recombinant envelope protein vaccine to protect against dengue virus Drosophila S2 Phase I [ 127 ]
Subunit VLP GenHevacB® – Vaccine agents hepatitis B composed of PreS1 and preS2 of HBV S-antigen assembled into HBV-like particles CHO Licensed [ 9 ]
Cervarix® – Vaccine against HPV infection composed of HPV L1 capsid protein from HPV16 and HPV18 assembled into a HPV-like particle High5 Licensed [ 11 ]
NCT01596725 – Influenza backbone (M1 structural protein) displaying HA and NA of influenza H1N1 Sf9 Phase I [ 128 ]
Subunit Vectored Vaccine Ad26.ENVA.01 – Ad26 vector for the expression of a modified HIV env glycoprotein (gp140HIV-1Clade A) HER.96 Phase II [ 129 ]
ChimeriVAX® – Chimeric YF17D/DEN vaccine against dengue using an attenuated yellow fever virus as a vector coding for PrM and E genes from dengue Vero Phase III [ 130 ]
AVX601 – Vaccine against HCMV it uses alphavirus as vector for the expression of HCMV gB/pp65/IE1 Vero Phase I [ 131 ]

2.3 Subunit vaccines

Subunit vaccines contain only parts of the pathogen. These vaccines use immunodominant antigens, specific parts of the virus (full proteins or peptides) known to stimulate the generation of neutralizing antibodies (Nabs). Subunit viral vaccines are a further development of inactivated viral vaccines but instead of generating antibodies against all of the pathogen antigens, only one or just a few antigens are used. The real challenge in the development of subunit vaccines is to identify which antigens induce protective immunity [ 20 ]. Examples of subunit viral vaccines available are the hepatitis B vaccine (e.g. GSK's Engerix® or Merck's RecombivaxHB®) or the recently approved influenza vaccine Flublok® (Protein Sciences). The subunit vaccines for hepatitis B are produced by recombinant technology using either yeast or CHO cells [ 9 , 21 ]. The Flublok® vaccine is a recombinant trivalent hemagglutinin (rHA) vaccine produced in insect cell culture using the baculovirus expression system [ 22 ]. Similarly to inactivated vaccines, subunit vaccines are stable and are considered safer than live attenuated vaccines. Their main disadvantage is the lower immune response elicited, when compared to live attenuated, requiring co-administration of adjuvants and often multiple doses [ 15 ].

Complex vaccine designs such as VLPs, DNA vaccines, vectored vaccines and vectored VLPs vaccines are often classified as subunit vaccines since they only provide a few antigens of the pathogen, either in the form of protein or genetic material. For the purpose of this review we will further describe these types of vaccines.

VLPs are particles that self-assemble from virus-derived structural antigens, mimicking the three dimensional structure of the pathogen. VLPs are non-infectious, replication-defective and are devoid of any genetic material. Because of that, VLPs are considered safer than live attenuated vaccines.

VLPs can be subcategorized in non-enveloped or enveloped VLPs based on their structure. Non-enveloped VLPs are typically composed of one or more proteins of the virus that self-assemble into particles and do not incorporate any host proteins. Enveloped VLPs are more complex structures as they are wrapped in a lipid membrane (an envelope) derived from the producer cell, where target antigens are anchored [ 23 ].

The ordered and repetitive structure that VLPs exhibit has excellent self-adjuvant properties capable of eliciting both innate and adaptive immune responses [ 24 ]. Indeed, VLPs can mount an effective immune protection without the use of co-adjuvants molecules and requiring lower doses than soluble protein antigens (see [ 25 ] for a review). Additionally, the VLPs structure favors its uptake by antigen presenting cells (APCs) essential to elicit long-lasting immune protection [ 11 ]. APCs display the foreign antigens complexed with major histocompatibility complexes (MHCs) on their surfaces. T-cells can recognize these complexes through their T-cell receptors (TCRs) starting an immune response by stimulating B and CD8 + lymphocytes [ 24 ].

The first VLP licensed for human use was the human papillomavirus (HPV) vaccine Gardasil® from Merck, produced in yeast [ 10 ] (Table 1). HPV Cervarix® was approved shortly after and is produced using the Baculovirus Expression System (BEVS) that uses insect cells [ 11 ]. Cervarix® is a bivalent HPV vaccine (L1 proteins of HPV-16 and HPV-18) indicated for the prevention of cervical cancer, was EMA approved in 2007 and FDA approved in 2009.

VLPs structural diversity and functional versatility forecasts the intensification in VLP research and future development of innovative vaccine designs.

DNA vaccines were developed as bacterial plasmids constructed to express an encoded antigen. They are administered in vivo, by transfecting the patient cells, eliciting both cellular and humoral immunity [ 26 ]. DNA vaccines have been approved for veterinary use (e.g. West Nile-Innovator® vaccine for horses [ 27 ] and Apex®-IHN for Salmonid fish [ 28 ]) but not yet for human use. One of the initial bottlenecks associated with DNA vaccines was the low potency which has been improved through the development of more efficient delivery systems in vivo and improved formulations with adjuvants (for a review on DNA vaccines see [ 26 ] ).

More complex subunit vaccines have been proposed. The engineering of modern vaccines based on different types of vectored vaccines and VLPs will be further discussed in the next section.


Subunit Vaccines

Instead of the entire pathogen, subunit vaccines include only the components, or antigens, that best stimulate the immune system. Although this design can make vaccines safer and easier to produce, it often requires the incorporation of adjuvants to elicit a strong protective immune response because the antigens alone are not sufficient to induce adequate long-term immunity.

Including only the essential antigens in a vaccine can minimize side effects, as illustrated by the development of a new generation of pertussis (whooping cough) vaccines. The first pertussis vaccines, introduced in the 1940s, comprised inactivated Bordetella pertussis bacteria. Although effective, whole-cell pertussis vaccines frequently caused minor adverse reactions such as fever and swelling at the injection site. This caused many people to avoid the vaccine, and by the 1970s, decreasing vaccination rates had brought about an increase in new infections. Basic research at NIAID and elsewhere, as well as NIAID-supported clinical work, led to the development of acellular (not containing cells) pertussis vaccines that are based on individual, purified B. pertussis components. These vaccines are similarly effective as whole-cell vaccines but much less likely to cause adverse reactions.

Some vaccines to prevent bacterial infections are based on the polysaccharides, or sugars, that form the outer coating of many bacteria. The first licensed vaccine against Haemophilus influenzae type B (Hib), invented at NIH’s National Institute of Child Health and Human Development and further developed by NIAID-supported researchers, was a polysaccharide vaccine. However, its usefulness was limited, as it did not elicit strong immune responses in infants—the age group with the highest incidence of Hib disease. NIH researchers next developed a so-called conjugate vaccine in which the Hib polysaccharide is attached, or “conjugated,” to a protein antigen to offer improved protection. This formulation greatly increased the ability of the immune systems of young children to recognize the polysaccharide and develop immunity. Today, conjugate vaccines are available to protect against Hib, pneumococcal and meningococcal infections.

Other vaccines against bacterial illnesses, such as diphtheria and tetanus vaccines, aim to elicit immune responses against disease-causing proteins, or toxins, secreted by the bacteria. The antigens in these so-called toxoid vaccines are chemically inactivated toxins, known as toxoids.

In the 1970s, advances in laboratory techniques ushered in the era of genetic engineering. A decade later, recombinant DNA technology—which enables DNA from two or more sources to be combined—was harnessed to develop the first recombinant protein vaccine, the hepatitis B vaccine. The vaccine antigen is a hepatitis B virus protein produced by yeast cells into which the genetic code for the viral protein has been inserted.

Vaccines to prevent human papillomavirus (HPV) infection also are based on recombinant protein antigens. In the early 1990s, scientists at NIH’s National Cancer Institute discovered that proteins from the outer shell of HPV can form particles that closely resemble the virus. These virus-like particles (VLPs) prompt an immune response similar to that elicited by the natural virus, but VLPs are non-infectious because they do not contain the genetic material the virus needs to replicate inside cells. NIAID scientists have designed an experimental VLP vaccine to prevent chikungunya that elicited robust immune responses in an early-stage clinical trial.

Scientists at NIAID and other institutions also are developing new strategies to present protein subunit antigens to the immune system. As part of efforts to develop a universal flu vaccine, NIAID scientists designed an experimental vaccine featuring the protein ferritin, which can self-assemble into microscopic pieces called nanoparticles that display a protein antigen. An experimental nanoparticle-based influenza vaccine is being evaluated in an early-stage trial in humans. The nanoparticle-based technology also is being assessed as a platform for development of vaccines against MERS coronavirus, respiratory syncytial virus (RSV) and Epstein Barr virus.

Other relatively recent advances in laboratory techniques, such as the ability to solve atomic structures of proteins, also have contributed to advances in subunit vaccine development. For example, by solving the three-dimensional structure of a protein on the RSV surface bound to an antibody, NIAID scientists identified a key area of the protein that is highly sensitive to neutralizing antibodies. They were then able to modify the RSV protein to stabilize the structural form in which it displays the neutralization-sensitive site.

While most subunit vaccines focus on a particular pathogen, scientists also are developing vaccines that could offer broad protection against various diseases. NIAID investigators in 2017 launched an early-phase clinical trial of a vaccine to prevent mosquito-borne diseases such as malaria, Zika, chikungunya and dengue fever. The experimental vaccine, designed to trigger an immune response to mosquito saliva rather than a specific virus or parasite, contains four recombinant proteins from mosquito salivary glands.


Abstract

A bottleneck to product development can be reliable expression of active target protein. A wide array of recombinant proteins in development, including an ever growing number of non-natural proteins, is being expressed in a variety of expression systems. A Pseudomonas fluorescens expression platform has been developed specifically for recombinant protein production. The development of an integrated molecular toolbox of expression elements and host strains, along with automation of strain screening is described. Examples of strain screening and scale-up experiments show rapid development of expression strains producing a wide variety of proteins in a soluble active form.

Highlights

► Bacterial recombinant protein expression systems are discussed. ► We outline important molecular tools for rapid recombinant protein production. ► Examples show that Pseudomonas fluorescens is a robust and effective production system for soluble and active recombinant proteins.


Staphylococcus aureus is a worldwide pathogen that causes mastitis in dairy herds. Shortcomings in control programs have encouraged the development of vaccines against this pathogen. This study evaluated the vaccine candidate VacR, which included recombinant S. aureus protein clumping factor A (rClf), fibronectin binding protein A (rFnBP) and hemolysin beta (rBt), formulated with a novel immune-stimulating complex. Comparisons were made between healthy pregnant heifers that received either VacR (n = 8 VacR group) or phosphate buffered saline (PBS) plus adjuvant (control group) SC in the supramammary lymph node area on days 45 and 15 before the expected calving date. Blood and foremilk samples were collected from 7 to 60 days post-calving.

After calving, heifers in the VacR group produced higher total IgG (IgGtotal) titers against each component, in both serum (rBt, 3.4 × 10 5 rClf, 3.1 × 10 5 rFnBP, 2.3 × 10 5 ) and milk (rBt, 2.6 × 10 4 rClf, 1.3 × 10 4 rFnBP, 1.1 × 10 4 ), than control heifers (P < 0.0001). There were increased concentrations of IgG1 and IgG2 in VacR group (P < 0.05), in both serum and milk. Humoral responses remained high throughout the period most susceptible to intramammary infections (P < 0.01). Antibodies produced against S. aureus rClf and rFnBP reduced bacterial adherence to fibronectin and fibrinogen by 73% and 67%, respectively (P < 0.001). Milk antibodies against these adhesins inhibited S. aureus invasion of a mammary epithelial cell line (MAC-T), resulting in 15.7% of bacteria internalized (P < 0.0001). There was an approximately 6-fold reduction in the hemolysis titer for the native hemolysin in the VacR group compared to the control group (P < 0.0001) and a significantly increase in the proportion of positive neutrophils (VacR, 29.7% PBS, 13.1%) and the mean fluorescent index (VacR, 217.4 PBS, 152.6 P < 0.01) in the VacR group. The results suggest that VacR is a valuable vaccine candidate against S. aureus infections, and merits further field trials and experimental challenges.


Impact of Using Different Promoters and Matrix Attachment Regions on Recombinant Protein Expression Level and Stability in Stably Transfected CHO Cells

High expression level and long-term expression stability are required for therapeutic protein production in mammalian cells. Three commonly used promoters from the simian virus 40 (SV40), the CHO elongation factor 1α gene (EF1α), and the human cytomegalovirus major immediate early gene (CMV) and two matrix attachment regions from the chicken lysozyme gene (cMAR) and the human interferon β (iMAR) were evaluated for enhancing recombinant gene expression level and stability in stably transfected CHO cells. In the absence of MAR elements, the SV40 promoter gave lower expression level but higher stability than the EF1α promoter and the CMV promoter. The inclusion of MAR elements did not increase the integrated gene copies for all promoters but did enhance expression level for only the SV40 promoter. The enhanced gene expression was due to an increase in mRNA levels. Neither MAR elements enhance gene expression stability during long-term culture. The combinations of SV40 promoter and MAR elements are the best for obtaining both high expression level and stability. The information presented here would be valuable to those developing vectors for generation of CHO cell lines with stable and high productivity.

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Randomized Study Evaluating Recombinant Human Bone Morphogenetic Protein-2 for Extraction Socket Augmentation

Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA.

Correspondence: Dr. Joseph P. Fiorellini, Harvard School of Dental Medicine, Department of Oral Medicine, Infection and Immunity, 188 Longwood Ave., Boston, MA 02115. Fax: 617/432-1897 e-mail: [email protected] .Search for more papers by this author

Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA.

Department of Periodontics, University of Texas Health Science Center at San Antonio, San Antonio, TX.

Private practice, Portland OR.

Wyeth/Genetics Institute, Cambridge, MA.

University Oral and Maxillofacial Surgery, Charlotte, NC.

Section of Dentistry, University of Chicago, Chicago, IL.

Department of Periodontics, University of Texas Health Science Center at San Antonio, San Antonio, TX.

Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA.

Institute for Advanced Dental Studies, Swampscott, MA.

Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA.

Correspondence: Dr. Joseph P. Fiorellini, Harvard School of Dental Medicine, Department of Oral Medicine, Infection and Immunity, 188 Longwood Ave., Boston, MA 02115. Fax: 617/432-1897 e-mail: [email protected] .Search for more papers by this author

Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA.

Department of Periodontics, University of Texas Health Science Center at San Antonio, San Antonio, TX.

Private practice, Portland OR.

Wyeth/Genetics Institute, Cambridge, MA.

University Oral and Maxillofacial Surgery, Charlotte, NC.

Section of Dentistry, University of Chicago, Chicago, IL.

Department of Periodontics, University of Texas Health Science Center at San Antonio, San Antonio, TX.

Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA.

Institute for Advanced Dental Studies, Swampscott, MA.

Abstract

Background: Conventional dentoalveolar osseous reconstruction often involves the use of grafting materials with or without barrier membranes. The purpose of this study was to evaluate the efficacy of bone induction for the placement of dental implants by two concentrations of recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered on a bioabsorbable collagen sponge (ACS) compared to placebo (ACS alone) and no treatment in a human buccal wall defect model following tooth extraction.

Methods: Eighty patients requiring local alveolar ridge augmentation for buccal wall defects (≥50% buccal bone loss of the extraction socket) of the maxillary teeth (bicuspids forward) immediately following tooth extraction were enrolled. Two sequential cohorts of 40 patients each were randomized in a double-masked manner to receive 0.75 mg/ml or 1.50 mg/ml rhBMP-2/ACS, placebo (ACS alone), or no treatment in a 2:1:1 ratio. Efficacy was assessed by evaluating the amount of bone induction, the adequacy of the alveolar bone volume to support an endosseous dental implant, and the need for a secondary augmentation.

Results: Assessment of the alveolar bone indicated that patients treated with 1.50 mg/ml rhBMP-2/ACS had significantly greater bone augmentation compared to controls (P ≤0.05). The adequacy of bone for the placement of a dental implant was approximately twice as great in the rhBMP-2/ACS groups compared to no treatment or placebo. In addition, bone density and histology revealed no differences between newly induced and native bone.

Conclusion: The data from this randomized, masked, placebocontrolled multicenter clinical study demonstrated that the novel combination of rhBMP-2 and a commonly utilized collagen sponge had a striking effect on de novo osseous formation for the placement of dental implants. J Periodontol 200576:605-613.


Watch the video: Mechanism of Recombination (August 2022).