Re-establishment of macrophage homeostasis by titanium surface modification in type II diabetes promotes osseous healing.

Titanium surface mediated immunomodulation may address compromised post-implantation bone healing in diabetes mellitus. To assess in vitro phenotypic changes, M1 and M2 polarised Type 2 diabetic rat (Goto Kakizaki, GK) macrophages were cultured on micro-rough (SLA) or hydrophilic nanostructured SLA (modSLA) titanium. The in vivo effects of the SLA and modSLA surfaces on macrophage phenotype, wound-associated protein expression and bone formation were investigated using a critical-sized calvarial defect model. Compared to healthy macrophages, GK M2 macrophage function was compromised, secreting significantly lower levels of the anti-inflammatory cytokine IL-10. The modSLA surface attenuated the pro-inflammatory cellular environment, reducing pro-inflammatory cytokine production and promoting M2 macrophage phenotype differentiation. ModSLA also suppressed gene expression associated with macrophage multinucleation and giant cell formation and stimulated pro-osteogenic genes in co-cultured osteoblasts. In vivo, modSLA enhanced osteogenesis compared to SLA in GK rats. During early healing, proteomic analysis of both surface adherent and wound exudate material showed that modSLA promoted an immunomodulatory pro-reparative environment. The modSLA surface therefore successfully compensated for the compromised M2 macrophage function in Type 2 diabetes by attenuating the pro-inflammatory response and promoting M2 macrophage activity, thus restoring macrophage homeostasis and resulting in a cellular environment favourable for enhanced osseous healing.

Silver Nanoparticles at Biocompatible Dosage Synergistically Increases Bacterial Susceptibility to Antibiotics.

Antibiotics used to treat bacterial infections can become ineffective over time or result in the emergence of antibiotic resistant pathogens. With the advent of nanotechnology, silver nanoparticles (AgNPs) have gained significant attention as a therapeutic agent due to the well-known antimicrobial properties of silver. However, there are concerns and limited literature on the potential cytotoxicity of nanoparticles at effective antimicrobial concentrations. AgNPs prepared from silver nitrate with glucose reduction were characterized by surface plasmon resonance, dynamic light scattering, zeta potential analysis and transmission electron microscopy. The cytotoxicity of AgNPs towards human gingival fibroblasts over 7 days was determined using cell proliferation assays and confocal microscopy. AgNP MIC and antibacterial effects alone and in combination with 11 antibiotics were determined against a panel of nine microbial species including gram-positive and gram-negative bacterial species. AgNPs concentrations ≤ 1 µg/mL were non-cytotoxic but also showed no antibacterial effects. However, when combined with each of eleven antibiotics, the biocompatible concentration of AgNPs (1 µg/mL) resulted in significant inhibition of bacterial growth for multiple bacterial species that were resistant to either the antibiotics or AgNPs alone. This study presents a promising strategy with further testing in vivo, to develop novel antimicrobial agents and strategies to confront emerging antimicrobial resistance.

Hydrophilic titanium surface-induced macrophage modulation promotes pro-osteogenic signalling.

OBJECTIVES: As biomaterial-induced modulation of mediators of the immune response may be a potential therapeutic approach to enhance wound healing events, the aim of this study was to delineate the effects of titanium surface modification on macrophage phenotype and function. MATERIAL AND METHODS: Rodent bone marrow-derived macrophages were polarized into M1 and M2 phenotypes and cultured on micro-rough (SLA) and hydrophilic modified SLA (modSLA) titanium discs. Macrophage phenotype and cytokine secretion were subsequently assessed by immunostaining and ELISA, respectively. Osteoblast gene expression in response to culture in the M1 and M2 macrophage conditioned media was also evaluated over 7 days by RT-PCR. RESULTS: M1 macrophage culture on the modSLA surface promoted an M2-like phenotype as demonstrated by marked CD163 protein expression, Arg1 gene expression and the secretion of cytokines that significantly upregulated in osteoblasts the expression of genes associated with the TGF-ß/BMP signalling pathway and osteogenesis. In comparison, M2 macrophage culture on SLA surface promoted an inflammatory phenotype and cytokine profile that was not conducive for osteogenic gene expression. CONCLUSIONS: Macrophages are able to alter or switch their phenotype according to the signals received from the biomaterial surface. A hydrophilic micro-rough titanium surface topography elicits a macrophage phenotype associated with reduced inflammation and enhanced pro-osteogenic signalling.

The influence of high-dose systemic zoledronate administration on osseointegration of implants with different surface topography.

AIM: To evaluate the influence of systemic zoledronate administration on the osseointegration of titanium implants with different surface topography in rat maxillae. METHODS: Twenty Sprague-Dawley rats were divided into two groups-test (bisphosphonate) and control (healthy). Bisphosphonate administration began three weeks prior to implant placement, and the animals received zoledronate (66 µg/kg) three times per week. Forty endosseous implants with a moderately rough (20 implants) or a turned surface (20 implants) were immediately placed bilaterally into extraction sockets of maxillary first molars. Animals were sacrificed after 14 and 28 days of healing, and en bloc specimens were harvested for histological and histomorphometric analysis. Osseointegration was quantified by measuring the percentage of bone-to-implant contact. RESULTS: Bone-to-implant contact (BIC) (mean ± SD) values of moderately rough and turned implants at day 14 in test group were 17.62 ± 6.68 and 10.69 ± 1.48, respectively, while in the control group, they were 46.36 ± 5.08 and 33.29 ± 8.89, respectively. At day 28, BIC values of moderately rough and turned implants in the test group were 25.94 ± 7.87 and 7.83 ± 4.30, respectively, while in the control group, they were 72.99 ± 6.60 and 47.62 ± 18.19, respectively. Statistically significant higher BIC values were measured on moderately rough implants compared to turned implants at 28 days, and the control group compared to the test group for both implant surfaces. Histological observations for the control and the test groups demonstrated initial bone formation around moderately rough implants not only on the surface of the parent bone, as was the case with the turned surfaced implants, but also along the implant surface itself. CONCLUSIONS: Systemic zoledronate administration negatively influences osseointegration. Osseointegration was enhanced adjacent to moderately rough compared to turned implants in both the presence and absence of systemic zoledronate administration. Therefore, topographical surface modification may partially offset the negative impact of zoledronate administration.

Tailoring the immuno-responsiveness of anodized nano-engineered titanium implants.

Owing to its biocompatibility and corrosion resistance, titanium is one of the most commonly used implantable biomaterials. Numerous in vitro and in vivo investigations have established that titanium surfaces with a nanoscale topography outperform conventional smooth or micro-rough surfaces in terms of achieving desirable bonding with bone (i.e. enhanced bioactivity). Among these nanoscale topographical modifications, ordered nanostructures fabricated via electrochemical anodization, especially titania nanotubes (TNTs), are particularly attractive. This is due to their ability to augment bioactivity, deliver drugs and the potential for easy/cost-effective translation into the current implant market. However, the potential of TNT-modified implants to modulate the host immune-inflammatory response, which is critical for achieving timely osseointegration, remains relatively unexplored. Such immunomodulatory effects may be achieved by modifying the physical and chemical properties of the TNTs. Furthermore, therapeutic/bioactive enhancements performed on these nano-engineered implants (such as antibacterial or osteogenic functions) are likely to illicit an immune response which needs to be appropriately controlled. The lack of sufficient in-depth studies with respect to immune cell responses to TNTs has created research gaps that must be addressed in order to facilitate the design of the next generation of immuno-modulatory titanium implants. This review article focuses on the chemical, topographical and mechanical features of TNT-modified implants that can be manipulated in order to achieve immuno-modulation, as well as providing an insight into how modulating the immune response can augment implant performance.

3-Dimensional functionalized polycaprolactone-hyaluronic acid hydrogel constructs for bone tissue engineering.

AIM: Alveolar bone regeneration remains a significant clinical challenge in periodontology and dental implantology. This study assessed the mineralized tissue forming potential of 3-D printed medical grade polycaprolactone (mPCL) constructs containing osteoblasts (OB) encapsulated in a hyaluronic acid (HA)-hydrogel incorporating bone morphogenetic protein-7 (BMP-7). MATERIALS AND METHODS: HA-hydrogels containing human OB ± BMP-7 were prepared. Cell viability, osteogenic gene expression, mineralized tissue formation and BMP-7 release in vitro, were assessed by fluorescence staining, RT-PCR, histological/µ-CT examination and ELISA respectively. In an athymic rat model, subcutaneous ectopic mineralized tissue formation in mPCL-hydrogel constructs was assessed by µ-CT and histology. RESULTS: Osteoblast encapsulation in HA-hydrogels did not detrimentally effect cell viability, and 3-D culture in osteogenic media showed mineralized collagenous matrix formation after 6 weeks. BMP-7 release from the hydrogel was biphasic, sustained and increased osteogenic gene expression in vitro. After 4 weeks in vivo, mPCL-hydrogel constructs containing BMP-7 formed significantly more volume (mm3 ) of vascularized bone-like tissue. CONCLUSIONS: Functionalized mPCL-HA hydrogel constructs provide a favourable environment for bone tissue engineering. Although encapsulated cells contributed to mineralized tissue formation within the hydrogel in vitro and in vivo, their addition did not result in an improved outcome compared to BMP-7 alone.

The influence of titanium surface characteristics on macrophage phenotype polarization during osseous healing in type I diabetic rats: a pilot study.

OBJECTIVES: This study assessed the effect of titanium surface modification on macrophage phenotype polarization and osseous healing under diabetic conditions. MATERIALS AND METHODS: Critical-sized calvarial defects were created in healthy and streptozotocin-induced type I diabetic Sprague-Dawley rats. Titanium (Ti) discs with either large-grit sandblasted and acid-etched micro-rough (SLA) or hydrophilic-modified SLA (modSLA) surfaces were used to cover the healing defect for a period of up to 28 days. Samples of the exudate within the calvarial defect and beneath the titanium discs were collected 1, 4 and 7 days post-surgery for inflammatory cytokine analysis using an ELISA. The macrophage phenotype(s) on the Ti disc surfaces were determined by CD11c+ (M1) and CD163+ (M2) immunofluorescent staining. Samples of the healing defects at days 14 and 28 were also prepared for histomorphometric analysis. RESULTS: Cytokine levels in the diabetic animals were higher than those of the healthy group throughout the observation period. The modSLA surface significantly reduced MIP-2 levels at day 1 in both diabetic and healthy animals, and MCP-1 levels at day 4 in the diabetic animals. Immuno-fluorescent staining showed that an M2-like macrophage phenotype was more frequently found on the modSLA surface at day 1 in healthy and day 4 in both healthy and diabetic animals. Histomorphometric analysis showed more new bone formation on the modSLA surface at days 14 and 28 in both groups, although statistically significant differences were only found in the healthy group. CONCLUSION: Diabetic conditions greatly increased the expression of proinflammatory cytokines during osseous healing. The modSLA surface was shown to promote an M2-like macrophage phenotypic response in titanium adherent macrophages despite the significantly elevated inflammatory environment induced by uncontrolled type I diabetes. Modulation of the macrophage phenotype by the modSLA surface in the early healing period was associated with osseous healing under both healthy and uncontrolled diabetic conditions.

The effects of implant topography on osseointegration under estrogen deficiency induced osteoporotic conditions: Histomorphometric, transcriptional and ultrastructural analysis.

UNLABELLED: Compromised bone quality and/or healing in osteoporosis are recognised risk factors for impaired dental implant osseointegration. This study examined the effects of (1) experimentally induced osteoporosis on titanium implant osseointegration and (2) the effect of modified implant surface topography on osseointegration under osteoporosis-like conditions. Machined and micro-roughened surface implants were placed into the maxillary first molar root socket of 64 ovariectomised and sham-operated Sprague-Dawley rats. Subsequent histological and SEM observations showed tissue maturation on the micro-rough surfaced implants in ovariectomised animals as early as 3days post-implantation. The degree of osseointegration was also significantly higher around the micro-rough implants in ovariectomised animals after 14days of healing although by day 28, similar levels of osseointegration were found for all test groups. The micro-rough implants significantly increased the early (day 3) gene expression of alkaline phosphatase, osteocalcin, receptor activator of nuclear factor kappa-B ligand and dentin matrix protein 1 in implant adherent cells. By day 7, the expression of inflammatory genes decreased while the expression of the osteogenic markers increased further although there were few statistically significant differences between the micro-rough and machined surfaces. Osteocyte morphology was also affected by estrogen deficiency with the size of the cells being reduced in trabecular bone. In conclusion, estrogen deficiency induced osteoporotic conditions negatively influenced the early osseointegration of machined implants while micro-rough implants compensated for these deleterious effects by enhancing osteogenic cell differentiation on the implant surface. STATEMENT OF SIGNIFICANCE: Lower bone density, poor bone quality and osseous microstructural changes are all features characteristic of osteoporosis that may impair the osseointegration of dental implants. Using a clinically relevant trabecular bone model in the rat maxilla, we demonstrated histologically that the negative effects of surgically-induced osteoporosis on osseointegration could be ameliorated by the biomaterial's surface topography. Furthermore, gene expression analysis suggests this may be a result of enhanced osteogenic cell differentiation on the implant surface.

The Ultrastructural Relationship Between Osteocytes and Dental Implants Following Osseointegration.

BACKGROUND: Osteocytes, the most abundant cells in bone, have multiple functions, including acting as mechanosensors and regulating mineralization. It is clear that osteocytes influence bone remodeling by controlling the differentiation and activity of osteoblasts and osteoclasts. Determining the relationship between titanium implants and osteocytes may therefore benefit our understanding of the process of osseointegration. PURPOSE: The aim of this study was to visualize the ultrastructural relationship between osteocytes and the titanium implant surface following osseointegration in vivo. MATERIALS AND METHODS: Titanium implants were placed in the maxillary molar regions of eight female Sprague Dawley rats, 3 months old. The animals were sacrificed 8 weeks after implantation, and undecalcified tissue sections were prepared. Resin-cast samples were subsequently acid-etched with 37% phosphoric acid prior to examination using scanning electron microscopy. RESULTS: Compared with mature bone, where the osteocytes were arranged in an ordered fashion, the osteocytes appeared less organized in the newly formed bone around the titanium implant. Further, a layer of mineralization with few organic components was observed on the implant surface. This study shows for the first time that osteocytes and their dendrites are directly connected with the implant surface. CONCLUSIONS: This study shows the direct anchorage of osteocytes via dendritic processes to a titanium implant surface in vivo. This suggests an important regulatory role for osteocytes and their lacunar-canalicular network in maintaining long-term osseointegration.

The Effect of Platelet Proteins Released in Response to Titanium Implant Surfaces on Macrophage Pro-Inflammatory Cytokine Gene Expression.

BACKGROUND AND PURPOSE: Platelets are one of the earliest cell types to interact with surgically inserted titanium implants. This in vitro study investigated the effect of titanium surface-induced platelet releasate on macrophage cytokine gene expression. MATERIALS AND METHODS: To mimic the in vivo temporal sequence of platelet arrival and protein production at the implant surface and the subsequent effect of these proteins on mediators of the immune response, the levels of platelet attachment and activation in response to culture on smooth polished, sandblasted and acid-etched (SLA), and hydrophilic-modified SLA (modSLA) titanium surfaces were first determined by microscopy and protein assay. The subsequent effect of the platelet-released proteins on human THP-1 macrophage cytokine gene expression was determined by polymerase chain reaction array after 1 and 3 days of macrophage culture on the titanium surfaces in platelet-releasate conditioned media. RESULTS: Platelet attachment was surface dependent with decreased attachment observed on the hydrophilic (modSLA) surface. The platelet releasate, when considered independently of the surface effect, elicited an overall pro-inflammatory response in macrophage cytokine gene expression, that is, the expression of typical pro-inflammatory cytokine genes such as TNF, IL1a, IL1b, and CCL1 was significantly up-regulated whereas the expression of anti-inflammatory cytokine genes such as IL10, CxCL12, and CxCL13 was significantly down-regulated. However, following platelet exposure to different surface modifications, the platelet releasate significantly attenuated the macrophage pro-inflammatory response to microrough (SLA) titanium and hastened an anti-inflammatory response to hydrophilic (modSLA) titanium. CONCLUSIONS: Theses results demonstrate that titanium surface topography and chemistry are able to influence the proteomic profile released by platelets, which can subsequently influence macrophage pro-inflammatory cytokine expression. This immunomodulation may be an important mechanism via which titanium surface modification influences osseointegration.

Titanium surface hydrophilicity enhances platelet activation.

Titanium implant surface modification is a key strategy used to enhance osseointegration. Platelets are the first cells that interact with the implant surface whereupon they release a wide array of proteins that influence the subsequent healing process. This study therefore investigated the effect of titanium surface modification on the attachment and activation of human platelets. The surface characteristics of three titanium surfaces: smooth (SMO), micro-rough (SLA) and hydrophilic micro-rough (SLActive) and the subsequent attachment and activation of platelets following exposure to these surfaces were determined. The SLActive surface showed the presence of significant nanoscale topographical features. While attached platelets appeared to be morphologically similar, significantly fewer platelets attached to the SLActive surface compared to both the SMO and SLA surfaces. The SLActive surface however induced the release of the higher levels of chemokines ß-thromboglobulin and platelet factor 4 from platelets. This study shows that titanium surface topography and chemistry have a significant effect on platelet activation and chemokine release.

The influence of cellular source on periodontal regeneration using calcium phosphate coated polycaprolactone scaffold supported cell sheets.

Cell-based therapy is considered a promising approach to achieving predictable periodontal regeneration. In this study, the regenerative potential of cell sheets derived from different parts of the periodontium (gingival connective tissue, alveolar bone and periodontal ligament) were investigated in an athymic rat periodontal defect model. Periodontal ligament (PDLC), alveolar bone (ABC) and gingival margin-derived cells (GMC) were obtained from human donors. The osteogenic potential of the primary cultures was demonstrated in vitro. Cell sheets supported by a calcium phosphate coated melt electrospun polycaprolactone (CaP-PCL) scaffold were transplanted to denuded root surfaces in surgically created periodontal defects, and allowed to heal for 1 and 4 weeks. The CaP-PCL scaffold alone was able to promote alveolar bone formation within the defect after 4 weeks. The addition of ABC and PDLC sheets resulted in significant periodontal attachment formation. The GMC sheets did not promote periodontal regeneration on the root surface and inhibited bone formation within the CaP-PCL scaffold. In conclusion, the combination of either PDLC or ABC sheets with a CaP-PCL scaffold could promote periodontal regeneration, but ABC sheets were not as effective as PDLC sheets in promoting new attachment formation.

Titanium surface hydrophilicity modulates the human macrophage inflammatory cytokine response.

Increased titanium surface hydrophilicity has been shown to accelerate dental implant osseointegration. Macrophages are important in the early inflammatory response to surgical implant placement and influence the subsequent healing response. This study investigated the modulatory effect of a hydrophilic titanium surface on the inflammatory cytokine expression profile in a human macrophage cell line (THP-1). Genes for 84 cytokines, chemokines, and their receptors were analyzed following exposure to (1) polished (SMO), (2) micro-rough sand blasted, acid etched (SLA), and (3) hydrophilic-modified SLA (modSLA) titanium surfaces for 1 and 3 days. By day 3, the SLA surface elicited a pro-inflammatory response compared to the SMO surface with statistically significant up-regulation of 16 genes [Tumor necrosis factor (TNF) Interleukin (IL)-1ß, Chemokine (C-C motif) ligand (CCL)-1, 2, 3, 4, 18, 19, and 20, Chemokine (C-X-C motif) ligand (CXCL)-1, 5, 8 and 12, Chemokine (C-C motif) receptor (CCR)-7, Lymphotoxin-beta (LTB), and Leukotriene B4 receptor (LTB4R)]. This effect was countered by the modSLA surface, which down-regulated the expression of 10 genes (TNF, IL-1α and ß, CCL-1, 3, 19 and 20, CXCL-1 and 8, and IL-1 receptor type 1), while two were up-regulated (osteopontin and CCR5) compared to the SLA surface. These cytokine gene expression changes were confirmed by decreased levels of corresponding protein secretion in response to modSLA compared to SLA. These results show that a hydrophilic titanium surface can modulate human macrophage pro-inflammatory cytokine gene expression and protein secretion. An attenuated pro-inflammatory response may be an important molecular mechanism for faster and/or improved wound healing.

Effect of culture conditions and calcium phosphate coating on ectopic bone formation.

This study investigated the effect of a calcium phosphate (CaP) coating onto a polycaprolactone melt electrospun scaffold and in vitro culture conditions on ectopic bone formation in a subcutaneous rat model. The CaP coating resulted in an increased alkaline phosphatase activity (ALP) in ovine osteoblasts regardless of the culture conditions and this was also translated into higher levels of mineralisation. A subcutaneous implantation was performed and increasing ectopic bone formation was observed over time for the CaP-coated samples previously cultured in osteogenic media whereas the corresponding non-coated samples displayed a lag phase before bone formation occurred from 4 to 8 weeks post-implantation. Histology and immunohistochemistry revealed bone fill through the scaffolds 8 weeks post-implantation for coated and non-coated specimens and that ALP, osteocalcin and collagen 1 were present at the ossification front and in the bone tissues. Vascularisation in the vicinity of the bone tissues was also observed indicating that the newly formed bone was not deprived of oxygen and nutrients. We found that in vitro osteogenic induction was essential for achieving bone formation and CaP coating accelerated the osteogenic process. We conclude that high cell density and preservation of the collagenous and mineralised extracellular matrix secreted in vitro are factors of importance for ectopic bone formation.

Quantitative analysis of periodontal pathogens by ELISA and real-time polymerase chain reaction.

The development of analytical methods enabling the accurate identification and enumeration of bacterial species colonizing the oral cavity has led to the identification of a small number of bacterial pathogens that are major factors in the etiology of periodontal disease. Further, these methods also underpin more recent epidemiological analyses of the impact of periodontal disease on general health. Given the complex milieu of over 700 species of microorganisms known to exist within the complex biofilms found in the oral cavity, the identification and enumeration of oral periodontopathogens has not been an easy task. In recent years however, some of the intrinsic limitations of the more traditional microbiological analyses previously used have been overcome with the advent of immunological and molecular analytical methods. Of the plethora of methodologies reported in the literature, the enzyme-linked immunosorbent assay (ELISA), which combines the specificity of antibody with the sensitivity of simple enzyme assays and the polymerase chain reaction (PCR), has been widely utilized in both laboratory and clinical applications. Although conventional PCR does not allow quantitation of the target organism, real-time PCR (rtPCR) has the ability to detect amplicons as they accumulate in "real time" allowing subsequent quantitation. These methods enable the accurate quantitation of as few as 10(2) (using rtPCR) to 10(4) (using ELISA) periodontopathogens in dental plaque samples.

Tannerella forsythensis prtH genotype and association with periodontal status.

BACKGROUND: The prtH gene of Tannerella forsythensis encodes for a cysteine protease possessing virulent properties. Subgingival colonization by T. forsythensis with this genotype has been suggested to be a discriminator between periodontal health and disease. This study examined the prevalence of T. forsythensis prtH genotype in subgingival plaque and its association with periodontal disease progression and current disease status. METHODS: Subjects harboring T. forsythensis in their subgingival plaque were identified using real-time polymerase chain reaction (PCR). The presence or absence of the prtH genotype was assessed by conventional PCR. Probing depths and relative attachment levels were also assessed. RESULTS: The prtH genotype was detected in 13 of 56 (23.2%) subjects harboring T. forsythensis in their subgingival plaque. Periodontal disease progression was defined as two or more sites with > or = 2 mm attachment loss in the previous 2-year period; current disease was defined as four or more sites with probing depths > or = 4 mm. The odds of periodontal disease (progression and/or current disease) were 1.55 times greater in subjects harboring prtH genotype T. forsythensis than in subjects in whom prtH was not detected. The prtH genotype was associated with higher numbers of T. forsythensis. In subjects with high levels of T. forsythensis, prtH genotype was associated with an increased extent of periodontal disease 2 years subsequently. CONCLUSIONS: These results show that T. forsythensis prtH genotype is associated with high levels of T. forsythensis. However, further work is needed to determine whether it also is a useful marker of periodontal disease progression in T. forsythensis-infected subjects.

IgG subclass specific antibody response to periodontopathic organisms in HIV-positive patients.

BACKGROUND: We previously reported an increased rate of progression of periodontal disease over an 18-month period in human immunodeficiency virus (HIV)-positive subjects compared to controls. The mechanism for disease progression and rapid tissue loss was unknown. Data on the microbiological studies failed to show any significant difference in the microbial characteristics of the periodontal lesions in HIV-positive patients compared to HIV-negative controls. Immunological analysis had identified neutrophils as an important component of the host defense against periodontal infection, especially against rapid tissue loss. Serum IgG reactivities to periodontal pathogens in HIV-positive patients with periodontitis were reduced. Other data provided circumstantial evidence to suggest that IgG subclass (IgG2) specific antibody might assist bacterial clearing in periodontal infection. The aim of the current study was to examine the specific IgG subclass antibody response to a panel of periodontopathic organisms: Actinobacillus actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Prevotella Intermedia (Pi), Fusobacterium nucleatum (Fn), Campylobacter rectus (Cr), and Bacteroides forsythus (Bf) in HIV-positive patients compared to HIV-negative controls. METHODS: Sera from 120 HIV-positive patients (40 periodontitis, 69 gingivitis, and 11 no oral diseases) were tested for IgG subclass specific antibody response to the above listed 6 organisms using enzyme-linked immunosorbent assay. Data were compared with those obtained from 40 HIV-negative control subjects (35 periodontitis, 2 gingivitis, and 3 no oral diseases). RESULTS: In the HIV-positive group, a consistently high response rate was found in IgG1 to all the bacteria tested. In addition, high levels of IgG3 and IgG4 to Pg and IgG1 and IgG2 to Pi were also present. However, no significant difference was detected among the periodontitis, gingivitis, and no oral disease subgroups. When the periodontitis patients from the HIV-positive group were compared to the HIV-negative group, no difference in the antibody levels and response rates was noted. CONCLUSION: We conclude that in HIV-positive patients, the specific IgG subclass antibody response to periodontopathic organisms was similar to that of HIV-negative subjects.