Ali Fattom

A nicotine conjugate vaccine reduces nicotine distribution to brain and attenuates its behavioral and cardiovascular effects in rats.

Vaccination of animals to elicit drug-specific antibodies, or the passive transfer of such antibodies from other animals, can reduce the behavioral effects of drugs such as cocaine and heroin. To study the potential application of this approach to treating nicotine dependence, IgG was isolated from rabbits immunized with a nicotine-protein conjugate vaccine. Anesthetized rats received immune IgG containing nicotine-specific antibodies (Nic-IgG) or control-IgG i.v.. Thirty minutes later, rats received nicotine at 0.03 mg/kg i.v., equivalent on an mg/kg basis to the nicotine intake from two cigarettes by a smoker. Compared to control-IgG, Nic-IgG reduced the brain nicotine concentration in a dose-related manner (65% reduction at the highest IgG dose). Pretreatment with Nic-IgG also reduced the distribution to brain of five repeated doses of nicotine (equivalent to the nicotine intake from 10 cigarettes) administered over 80 min. To study blood pressure effects, rats received control-IgG or Nic-IgG 1 day prior to administering nicotine. Nicotine-induced systolic blood pressure increases were attenuated by Nic-IgG in a dose-related manner, and were almost completely blocked by the highest Nic-IgG dose. Pretreatment with Nic-IgG also completely prevented the nicotine-induced stimulation of locomotor activity observed in rats receiving control-IgG. Nic-IgG did not prevent locomotor activation from cocaine, demonstrating its specificity for nicotine. These data demonstrate that the administration of nicotine-specific antibodies can reduce or prevent some of the pharmacokinetic, cardiovascular, and behavioral consequences of nicotine in rats. Effects were observed at nicotine doses and nicotine serum concentrations equal to or exceeding those typically associated with nicotine exposure in cigarette smokers. A potential role for immunization in the treatment of nicotine dependence is suggested.

Epitopic overload at the site of injection may result in suppression of the immune response to combined capsular polysaccharide conjugate vaccines.

Capsular polysaccharide (CP) conjugate vaccines targeting a variety of bacterial infections are currently under development and clinical evaluation. The inclusion of multiple CP serotypes combined in a single injection is an important maneuver being evaluated. The combination of CP conjugate vaccines into a single multivalent injection may result in competition among the different components and adversely affect the immunogenicity of any individual conjugate. We observed a reduction of 30-90% in antibody responses to several serotypes in mice when immunogenicity of a 12-valent Escherichia coli (E. coli) lipopolysaccharide (LPS) conjugate vaccine was compared to the immunogenicity of each monovalent vaccine evaluated separately. A reduction of 30% was observed in the Staphylococcus aureus (S. aureus) type 8 CP antibodies when a type 8-rEPA conjugate was combined with a type 5-rEPA conjugate. S. aureus types 5 and 8-rEPA conjugates were combined with 100 micrograms of either rEPA (homologous) or diphtheria toxoid (DT) (heterologous) carrier proteins, and evaluated in rEPA or DT primed mice. The addition of the homologous protein resulted in a 64% reduction in type 5 CP antibodies. The heterologous protein did not affect the immunogenicity of the type 5. We postulate that the free protein competed with the conjugate and recruited most of the rEPA primed T cells. In the case of the DT conjugates, the DT targeted different populations of the T cells, thus interference was not observed. These data suggested that the epitopic load rather than the antigenic load at the site of injection caused reduced immunogenicity of the conjugates. We theorize that individual components of multivalent CP vaccines conjugated to the same carrier proteins would compete for a limited number of specific carrier protein primed T cells. This would result in one or more components being unavailable in eliciting a sufficient immune response. The use of multiple carrier proteins should be considered as an approach to reduce interference when multivalent conjugate vaccines are to be formulated into a single injection.

Identification of the Capsular Polysaccharides in Staphylococcus aureus Clinical Isolates by PCR and Agglutination Tests

ABSTRACT Staphylococcus aureus is a major cause of nosocomial and community-acquired infections. The predominance of two capsular polysaccharides, types 5 and 8, on the surface of clinical isolates led to the development of a conjugate vaccine (StaphVAX) based on capsular polysaccharides types 5 and 8 conjugated to a carrier protein. We have studied the capsular phenotypes and genotypes of 195 isolates representative of all clinical syndromes that encompassed both hospital and community-acquired infections. These isolates were mainly detected in France between January 2001 and December 2004. In this population, most of clinical isolates (87%) expressed either capsular polysaccharide type 5 (42%) or 8 (45%), whereas 13% were nontypeable by the serotyping method with antibodies specific to capsular polysaccharide type 5 or 8. These 26 nontypeable strains were further serotyped and were demonstrated to express the cell wall surface antigen 336, a polyribitol phosphate N-acetylglucosamine, which resembles cell wall teichoic acid. Among methicillin-resistant Staphylococcus aureus (MRSA) strains, we found a predominance of serotype 5 for 64% of strains, whereas MSSA isolates were predominantly capsular serotype 8 (60%). All S. aureus clinical isolates included in the present study have been investigated by PCR method, demonstrating that all isolates carried either the cap5 or the cap8 locus.

Effect of conjugation methodology, carrier protein, and adjuvants on the immune response to Staphylococcus aureus capsular polysaccharides

Conjugate vaccines were prepared with S. aureus type 8 capsular polysaccharide (CP) using three carrier proteins: Pseudomonas aeruginosa exotoxin A (ETA), a non-toxic recombinant ETA (rEPA), and diphtheria toxoid (DTd). Adipic acid dihydrazide (ADH) or N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) was used as a spacer to link the CP to carrier protein. All conjugates gave a high immune response with a boost after the second immunization. Conjugates prepared with ADH gave higher antibody titers than conjugates prepared with SPDP. IgG1 was the primary subclass elicited by all conjugates regardless of the carrier protein or the conjugation method used to prepare the vaccines. The non-immunogenic CP and the conjugates were formulated with either monophosphoryl lipid A (MPL), QS21, or in Novasomes and evaluated in mice. While the adjuvants failed to improve the immunogenicity of the nonconjugated CP, a more than fivefold increase in the antibody levels was observed when these adjuvants were used with the conjugates. Significant rises in IgG2b and IgG3 were observed with all formulations. The enhancement of the immunogenicity and the IgG subclass shift, as seen with some adjuvants, may prove to be important in immunocompromised patients.

Head-injured patients who are nasal carriers of Staphylococcus aureus are at high risk for Staphylococcus aureus pneumonia.

OBJECTIVE To determine if head-injured patients with premorbid nasal colonization with Staphylococcus aureus are at increased risk for S. aureus infection. DESIGN Patients admitted over a 2-yr period were enrolled if they met the following criteria: Injury Severity Score > or = 9, intensive care unit (ICU) admission, hospitalization in another hospital < 24 hrs, no recent use of antibiotics. SETTING Acute care trauma facility. PATIENTS Any patient sustaining acute, blunt, or penetrating injury and meeting the enrollement criteria were eligible. INTERVENTIONS Swab cultures of both internal nares were performed within 72 hrs of readmission and cultured for S. Aureus. Patients were prospectively monitored for S. Aureus infections until discharge. MEASUREMENTS AND MAIN RESULTS Admission nasal cultures were positive (NC+) for S. aureus in 144 of the 776 patients cultured. Forty of the 144 NC+ patients had isolated head (37) or high cervical spine (3) injury, and 11 of that group (27.5%) developed S. aureus infections. The remaining 104 patients positive for S. aureus on admission had no head injury (74) or head combined with torso and extremity injuries (30). S. aureus infection was diagnosed in 11 of the 104 patients (10.6%). The difference in incidence of infections is significant (p <.01), as is the difference in incidence of pneumonia (20% vs. 3.8%, respectively [p <.01]). Organisms causing pneumonia were often the same organisms isolated from the nares on admission. CONCLUSIONS Nasal colonization with S. aureus at the time of severe head injury increases the risk of S. aureus pneumonia during hospitalization. Prophylactic measures against S. aureus pneumonia may help reduce the length and cost of hospitalization.

Passive immunization against nicotine attenuates nicotine discrimination

Ten rats were trained in a two lever operant chamber to press different levers after a nicotine injection (0.14 mg/kg s.c.) or a saline injection on an FR10 schedule. The rats were then injected i.p. with either 150 mg nicotine-specific IgG or the same amount of control IgG from non-immunized rabbits. On successive days, they were retested with both levers active after a saline injection, a full training dose of nicotine and a half dose of nicotine (0.07 mg/kg s.c.). After saline injection, both groups pressed the saline lever almost exclusively. After each of the nicotine doses, the immunized rats performed a significantly lower percentage of their lever presses on the nicotine lever than did non-immunized rats. The results suggest that passive immunization can interfere with the stimulus properties of nicotine.

Adjuvant activity of QS-21 for experimental E. coli 018 polysaccharide vaccines

Three types of experimental vaccines containing O-side-chain polysaccharide from the enterotoxigenic strain Escherichia coli 018 were evaluated. The immunogenicity of free O-polysaccharide (PS), a polysaccharide-diphtheria toxoid conjugate (PS-conj), and detoxified lipopolysaccharide (dLPS) was tested in female ICR mice, either alone or in combination with QS-21, a purified saponin adjuvant derived from the bark of the tree Quillaja saponaria Molina. Both the number of individual mice responding and the titres of O-polysaccharide specific antibodies in pools of sera were increased by the addition of QS-21. The immune response to both O-specific polysaccharide and carrier was primarily IgM and IgG1. The addition of QS-21 not only increased the level of IgG1, but also had a significant adjuvant effect on antigen-specific IgG2a, IgG2b and IgG3.

Staphylococcal Vaccines: A Realistic Dream

Staphylococcus aureus, especially multidrug resistant strains, continues to be a leading cause of serious nosocomial infections. In spite of the debate among investigators in the field, the discovery of serologically distinct capsular polysaccharides on the surface of clinical isolates has renewed the prospects for development of vaccines and passive protective immunity against S. aureus infections. Capsular polysaccharide conjugate vaccines have now been produced and proven to be safe and immunogenic in both healthy and in a significant percentage of immunocompromised patients. Antibodies generated in humans against these vaccines have been shown to mediate type-specific opsonophagocytosis, and to protect animals against lethal challenge with the appropriate S. aureus isolate.

Capsular polysaccharide-protein conjugate vaccines

The conjugation of polysaccharides to carrier proteins generally enhances polysaccharide immunogenicity and renders the immune response T-cell dependent. Such enhancement of immunogenicity has made the use of conjugate vaccines possible in populations that are otherwise unresponsive to polysaccharide vaccines. Here, the authors discuss the value of capsular polysaccharide vaccines, their ability to elicit protective immunity against infectious bacteria, the selection of appropriate polysaccharides and carrier proteins, and the applications of the resultant conjugate vaccines.

Safety and immunogenicity of a tetravalent group B streptococcal polysaccharide vaccine in healthy adults

Proposed strategies for prevention of neonatal group B streptococcal (GBS) infection have included active immunization of pregnant women and passive immunization of high-risk infants with hyperimmune GBS globulin derived from vaccinated plasma donors. To explore the feasibility of a program for generating hyperimmune GBS globulin, we evaluated the safety and immunogenicity of a candidate multivalent GBS vaccine containing purified polysaccharide from types Ia, Ib, II, and III among subjects most likely to develop an immune response following vaccination, i.e. those with pre-existing antibody to GBS. Thirty volunteers prescreened for serum antibody to type III GBS were immunized with a single subcutaneous injection of vaccine containing either 10, 25, or 50 micrograms of each polysaccharide type (Group 1). An additional ten volunteers prescreened for antibody to type Ia were vaccinated with the 50 micrograms dose (Group 2). Vaccination was generally well tolerated with minor reactions occurring in 27% of subjects. Using a quantitative enzyme-linked immunosorbent assay (ELISA), the seroconversion rates (> or = fourfold rise) and geometric mean antibody concentration (GMC in microgram IgG ml-1) 6 weeks after vaccination in Group 1 to type Ia, II, and III were 33% (GMC 5.2), 17% (GMC 3.6), and 70% (GMC 43.4), respectively. Quantitative titers were not available for type Ib, but a fourfold rise in ELISA units was seen in 13% of subjects. In Group 2, seroconversion rates to type Ia and III were 90% (GMC 73.4) and 40% (GMC 22.2), respectively. No significant dose-response effect was detected. Combined analysis of Groups 1 and 2 demonstrated that subjects with prevaccination antibody concentrations > 2 micrograms IgG ml-1 had significantly higher type-specific antibody concentrations following vaccination compared with subjects possessing lower levels of antibody before immunization. We conclude that our tetravalent GBS polysaccharide vaccine is safe but only modestly immunogenic in healthy seropositive adults. More potent vaccines will be required for public health use.