Efficacy Of Active Immunization Research Articles

Efficacy of Active Immunization With Attenuated α-Hemolysin and Panton-Valentine Leukocidin in a Rabbit Model of Staphylococcus aureus Necrotizing Pneumonia

Staphylococcus aureus is a common pathogen causing infections in humans with various degrees of severity, with pneumonia being one of the most severe infections. In as much as staphylococcal pneumonia is a disease driven in large part by α-hemolysin (Hla) and Panton-Valentine leukocidin (PVL), we evaluated whether active immunization with attenuated forms of Hla (HlaH35L/H48L) alone, PVL components (LukS-PVT28F/K97A/S209A and LukF-PVK102A) alone, or combination of all 3 toxoids could prevent lethal challenge in a rabbit model of necrotizing pneumonia caused by the USA300 community-associated methicillin-resistant S. aureus (MRSA). Rabbits vaccinated with Hla toxoid alone or PVL components alone were only partially protected against lethal pneumonia, whereas those vaccinated with all 3 toxoids had 100% protection against lethality. Vaccine-mediated protection correlated with induction of polyclonal antibody response that neutralized not only α-hemolysin and PVL, but also other related toxins, produced by USA300 and other epidemic MRSA clones.

Response Is Seen to Conjugate Vaccine but Not to Polysaccharide Vaccine Twelve Months After Rituximab.

Abstract 2728Poster Board II-704 Background:After therapy with the monoclonal antibody anti-CD20 rituximab ® (R), normal B-cells are depleted and their recovery in blood is delayed until six-twelve months in patients with relapsed low-grade lymphoma treated with four infusions of R. In patients treated with R-chemotherapy or high-dose therapy after R-purged autologous graft, the B-cell recovery is postponed further. The efficacy of active immunization against various bacterial and viral infections of R- treated patients has been debated as total level of immunoglobulin (Ig) M has been shown to decrease during prolonged treatment with R and humoral T cell-independent response might be defect due to lack of B-cells. Aim:To evaluate antibody-response to two vaccines after two timepoints of vaccination. Methods:An open randomized study of patients with B-cells lymphoma vaccinated six or twelve month after last treatment with R (Mabthera® Hoffman-LaRoche, Basel, Switzerland) with or without chemotherapy. Pneumococcal polysaccharide vaccine, Pneumo23® (Sanofi Pasteur MSD), assessed T-cell–independent antibody response and conjugated H. influenza type b-vaccine, Act-Hib® (Sanofi Pasteur MSD), evaluated combined B-cell/T-cell pathway. The patients randomized to vaccination at six months and without response, were revaccinated after further six months. Blood samples were collected immediately before vaccination and four weeks after. Serum was separated, frozen to −20 degrees C, sent to the Division of Microbiology, Statens Seruminstitut, Copenhagen, Denmark for analyses. A modified enzyme-linked assay for measuring type-specific anti-pneumococcal capsular polysaccharide antibodies for 6 pneumococcal serotypes (1, 4, 7F, 14, 18C, 19F) was used and a geometrical mean value for the total titer of antibody was calculated. The definition of protective response was determined to >39 arbitrary units/ml. Total Ig antibodies to the capsular polysaccharide of Haemophilus influenzae type b (HbPs) was measured by ELISA. An anti-HbPs antibody titer of >1 μg/ml was recorded as a protective response after immunization. Blood samples for flow cytometry analysis, including CD19+ and CD20+ B-cell counts, were drawn at the time of vaccination and four weeks after. Results:Nine patients, age 56–73 years, six females and three males, were randomized to vaccination; four at six months and five at twelve months after last rituximab treatment. Five patients with follicular lymphoma (FL) grade 2 and one with marginalzone lymphoma (MZL) had received single R, one of these in combination with alfa-interferon in a clinical phase II trial. One patient with mantle cell lymphoma (MCL) and one with follicular centroblastic lymphoma were treated with R-CHOP-21 × 8 prior to vaccination. One female patient with MZL randomized to vaccination at twelve months, dropped out because of progression of disease. Vaccination with Pneumo23® resulted in a protective response of pneumococcal antibodies in only one out of eight (12,5 %) patients. This responding patient had MZL treated with R 375 mg weekly x4 during 2 courses, and was randomized to vaccination 6 months after last R and also showed a response to Act-Hib vaccine. Further four patients had an immunization response to act Hib vaccine, one with FL randomized to vaccination six months after R and three after twelve months, two with FL and one with MCL. One patient was revaccinated after twelve months and had no response neither with Pneumo23® or Act-Hib® vaccine. The percentage CD19+ and CD20 + B-cells in the lymphocyte gate (by flow cytometry) was low in all patients at the time of vaccination and four weeks after, but showed a slight increase with time (0,04, 0,26, 0,42, 0,54 % and 0,24, 0,6, 0,6, 1,26, 1,0 % at six and twelve months after R, respectively). Conclusion:Conjugate vaccine is more potent to give immune response than polysaccharide vaccine after R-therapy in patients with B cell lymphoma. Despite deficient recovery of B-cells cells, five of eight (62,5 %) patients responded to the conjugate vaccine Act-Hib®. The longstanding effect on the immune system of antibody therapy has to be further studied. Disclosures:No relevant conflicts of interest to declare.

Active immunization against murine TNFα peptides in mice: generation of endogenous antibodies cross-reacting with the native cytokine and in vivo protection

New lines of treatment targeting cytokines have been successfully developed recently and are now widely used in therapy. They are based on passive administration of cytokine inhibitors either soluble receptors or mAbs and the major example is TNFα in rheumatoid arthritis (RA). Since a few years, our group has developed a novel alternative approach targeting cytokines by using active immunization against biologically inactive but immunogenic cytokine derivatives. In the present work, we present a new aspect of this research, based on immunization against specific cytokine peptides chosen by molecular modelling. We could elicit a significant humoral response against four TNFα peptides by active immunization, and show that the Abs generated cross-reacted with the native cytokine with good titers as determined by ELISA. Interestingly, during coimmunization experiments with couples of peptides, one showed a clear immunodominant effect over the other. Overall, we could not show the neutralization of TNFα biological activity in vitro by the immunized sera, but it seems that it is not a prerequisite to observe clinical efficacy. Indeed, using the LPS/galactosamine-induced shock, we could demonstrate that one of the four peptides tested conferred a clinical protection. These results validate the feasibility and efficacy of active immunization against cytokine peptides, and confirm that active immunization against cytokines could represent in the future an alternative to passive immunization in many diseases.

Cocaine vaccines: antibody protection against relapse in a rat model.

The efficacy of active immunization with the cocaine immunogen GNC-keyhole limpet hemocyanin (KLH) in preventing cocaine self-administration reinstatement was assessed in rats. An animal model of relapse was used where rats were trained to self-administer cocaine, subjected to a period of extinction by substituting the drug for saline, vaccinated, and re-exposed to cocaine. Compared with controls, animals immunized with GNC-KLH did not reinstate cocaine self-administration behavior when given a noncontingent cocaine infusion on two consecutive days. Upon double and triple infusions, 38-62% of vaccinated animals failed to reinstate as compared with full reinstatement in all control animals. Exposure to ad libitum cocaine reinstated baseline values in control animals and resulted in double to triple the baseline values of self-infusions in vaccinated animals, suggesting a partial antibody-mediated blockade of cocaine access to the central nervous system. This compensating effect was blocked by passive immunization pretreatment with the monoclonal IgG GNC92H2 in both vaccinated and control groups. To further assess the surmountability potential of GNC-KLH-induced antibody titers by cocaine self-administration, and the capacity of these titers to block the reinforcing effects of the drug, rats were tested at various doses of cocaine (0.015-0.5 mg/infusion). Active immunization with GNC-KLH produced approximately an 8-fold rightward shift of the dose-effect function for cocaine. The results reported suggest that immunopharmacotherapy may offer a promising means to treat cocaine abuse by aiding in the prevention of relapse.

Active and passive immunization strategies for Pseudomonas aeruginosa pneumonia.

The unusually high mortality associated with Pseudomonas aeruginosa pneumonia has provided an incentive for the development of immunologic strategies for preventing or treating this infection. A guinea pig model of experimental P. aeruginosa pneumonia was employed to determine prophylactic efficacy of active immunization with a detoxified lipopolysaccharide vaccine; efficacy of passive immune therapy utilizing a new hyperimmune immunoglobulin G preparation enriched for antibodies to P. aeruginosa immunotypes 1, 2, 4, and 6; and efficacy of active and passive immunization against the mucoid exopolysaccharide antigen associated with mucoid strains of P. aeruginosa. Each of these immunologic methods provided an element of protection against P. aeruginosa pneumonia.