Monoclonal antibody therapeutics and risk for infection

A framework for the use of biological medicines in the free state province, South Africa

PURPOSE

The use of biological medicines (BM) has increased worldwide owing to their effectiveness in the treatment of many chronic diseases. However, in South Africa, access to BM remains limited, hence, there is a need to develop strategies that will enable timely access to BM by all patients who need them.

OBJECTIVE

To develop a framework for the use of BM in South Africa.

METHODS

Using a Delphi questionnaire that was developed by integration of the opinions of newly qualified doctors (<2 years practice), prescribing specialists, and patients using BM, a Delphi method was used to guide an experts' panel into consensus on the different opinions in the questionnaire, and from this, a framework for the use of BM was constructed.

RESULTS

From the surveys, 76.2% of the newly qualified doctors and 91.7% of the prescribing specialists indicated that they had limited knowledge on the pharmacology of BM, and, respectively, 64.5% and 77.8% admitted that their knowledge on BM was not adequate for prescribing and taking care of patients on BM. Also, 58.3% and 75% of the prescribers indicated that the high cost and the tedious procurement process, respectively, were barriers of access to BM. The Delphi panel reached consensus after two rounds, and the resultant framework recommends that, appropriate use of BM requires establishing guidelines for the use of BM, increasing BM content in the medical training programs and information resources used by healthcare professionals, enacting drug regulations and drug policies that will increase availability of BM, offering appropriate patient information and public engagement.

CONCLUSION

The lack of knowledge on BM by health professionals, together with the high cost and a complex procurement processes are the major impediment to access to BM. A framework for the use of BM in South Africa was successfully developed to address these and other challenges.

Infections in the Non-Transplanted Immunocompromised Host

BACKGROUND

Discoveries regarding the basic mechanisms underlying malignant disease, rheumatologic disorders, and autoimmune diseases have led to the development of many new therapeutic modalities that target components of the immune system. Most of these are antibodies or fusion proteins that interfere with components of the immune response that are playing both pathological and protective roles, resulting in variable degrees of immune suppression and a higher risk of infectious complications.

METHODS

Review of the English-language literature.

RESULTS

As these modalities are often used in combination with more traditional methods of immune suppression (e.g., corticosteroids), an increasing spectrum of infection is being encountered by clinicians. Febrile neutropenia requires rapid assessment and initiation of empiric broad-spectrum antimicrobial therapy. Persistence despite this therapy should prompt further investigation for drug-resistant bacteria and invasive fungal disease. Important pathogens to consider in patients with neutropenia, chronic steroid exposure, or underlying gastrointestinal malignant diseases include fungi (Candida, Aspergillus) and atypical bacteria (Nocardia, Clostridium septicum).

CONCLUSIONS

This review focuses on observations regarding the greater risk of infections associated with many of these new biological modalities, as well as some specific infectious complications that may be encountered more commonly by the surgical consultant.

Antigen presentation by B cells guides programing of memory CD4+ T-cell responses to a TLR4-agonist containing vaccine in mice

The contribution of B cells to immunity against many infectious diseases is unquestionably important and well characterized. Here, we sought to determine the role of B cells in the induction of T-helper 1 (T_H 1) CD4⁺ T cells upon vaccination with a tuberculosis (TB) antigen combined with a TLR4 agonist. We used B-cell deficient mice (μMT^-/- ), tetramer-positive CD4⁺ T cells, markers of memory "precursor" effector cells (MPECs), and T-cell adoptive transfers and demonstrated that the early antigen-specific cytokine-producing T_H 1 responses are unaffected in the absence of B cells, however MPEC induction is strongly impaired resulting in a deficiency of the memory T_H 1 response in μMT^-/- mice. We further show that antigen-presentation by B cells is necessary for their role in MPEC generation using B-cell adoptive transfers from wt or MHC class II knock-out mice into μMT^-/- mice. Our study challenges the view that B-cell deficiency exclusively alters the T_H 1 response at memory time-points. Collectively, our results provide new insights on the multifaceted roles of B cells that will have a high impact on vaccine development against several pathogens including those requiring T_H 1 cell-mediated immunity.

B cell depletion curtails CD4+ T cell memory and reduces protection against disseminating virus infection

Dynamic interactions between CD4(+) T cells and B cells are needed for humoral immunity and CD4(+) T cell memory. It is not known whether B cells are needed early on to induce the formation of memory precursor cells or are needed later to sustain memory cells. In this study, primary and memory CD4(+) T cells responses were followed in wild-type mice that were depleted of mature B cells by anti-CD20 before or different times after acute lymphocytic choriomeningitis virus infection. The Ab treatment led to a 1000-fold reduction in B cell number that lasted 6 wk. Primary virus-specific CD4(+) Th1 cells were generated in B cell-depleted mice; however, there was a decrease in the CD4(+)Ly6C(lo)Tbet(+) memory precursor population and a corresponding 4-fold reduction in CD4(+) memory cell number. Memory T cells showed impaired cytokine production when they formed without B cells. B cell depletion had no effect on established memory populations. During disseminating virus infection, B cell depletion led to sustained weight loss and functional exhaustion of CD4(+) and CD8(+) T cells, and prevented mice from resolving the infection. Thus, B cells contribute to the establishment and survival of memory CD4(+) T cells post-acute infection and play an essential role in immune protection against disseminating virus infection.

Diagnosis and management of infectious complications of childhood rheumatic diseases

Progress in the diagnosis and management of pediatric rheumatic disease has improved complications from underlying disease and the survival of children. However, as a consequence, infection has now become one of the leading causes of morbidity and mortality. Differentiating between infections and disease flares in children with rheumatic conditions can often pose diagnostic quandaries. Children with rheumatic diseases are at risk of infection, not only because of the use of immune-modulating medications but also because of underlying immune dysfunction associated with their disease. Although bacterial infections are the most common, any organism can potentially be a causative agent and, at times, more invasive measures of diagnosis, for example bronchoscopy and tissue biopsies may be necessary. Maintaining a high index of suspicion of infection with prompt diagnosis and treatment are important to further improve patient outcomes.

Fibroblast Growth Factor-2 Enhances Expansion of Human Bone Marrow-Derived Mesenchymal Stromal Cells without Diminishing Their Immunosuppressive Potential

Allogeneic hematopoietic stem cell transplantation is the main curative therapy for many hematologic malignancies. Its potential relies on graft-versus-tumor effects which associate with graft-versus-host disease. Mesenchymal stromal cells (MSCs) possess immunomodulatory properties that make them attractive therapeutic alternatives. We evaluated the in vitro immunosuppressive activity of medium conditioned by human MSCs from 5 donors expanded 13 passages with or without FGF-2. FGF-2 supplementation increased expansion 3,500- and 240,000-fold by passages 7 and 13, respectively. There were no differences in immunosuppressive activity between media conditioned by passage-matched cells expanded under different conditions, but media conditioned by FGF-treated MSCs were superior to population doubling-matched controls. The immunosuppressive activity was maintained in three of the preparations but decreased with expansion in two. The proliferation induced by FGF-2 did not result in loss of immunosuppressive activity. However, because the immunosuppressive activity was not consistently preserved, caution must be exercised to ensure that the activity of the cells is sufficient after extensive expansion.

Adverse effects of biologics used for treating IBD

In the last decade, biologic agents, in particular anti-TNF agents such as infliximab, adalimumab, and certolizumab have substantially extended the therapeutic armamentarium of inflammatory bowel disease (IBD). Additional approaches include biologicals, such as natalizumab, that block leucocyte adhesion; those that target cytokines, such as interleukin-12/23 antibodies; or those that inhibit T-cell signaling, such as interleukin-6 receptor antibodies. However, these drugs have a number of contraindications and side effects, especially when used in combination with classical immunosuppressive agents or corticosteroids. Areas of concern include opportunistic infections, malignancies, and miscellaneous complications such as injection/infusion reactions and autoimmunity and contraindications, such as heart failure and acute infectious diseases. In this review, the indications of biologicals in IBD treatment are briefly reported, and the potential disadvantages of a more active therapeutic approach in IBD are discussed. We have learned in the last decade that anti-TNF-alpha therapy is an effective and relatively safe treatment option for selected patients that changes the natural course of severe IBD. However, despite these changed therapeutic paradigms and goals in IBD, clinicians should be aware that the powerful immunosuppressive capacity of biologicals necessitates a rigorous long-term safety follow-up.

Invasive fungal infections in the era of biologics

With the advent and widespread use of immunomodulating biologic agents, emerging invasive fungal infections are reported increasingly. To date there is no reliable method to screen patients before starting anti-tumor necrosis factor (TNF) therapy to predict their risk for acquiring fungal infections, partly because most of these infections are de novo infections. Patients should be counseled about avoiding high-risk activities that are associated with the endemic mycosis in their geographic areas. Physicians should keep a high level of suspicion for endemic fungal infections when patients receiving anti-TNF therapy or other biologics present with pulmonary or systemic infections. Rapid diagnosis and initiation of antifungal therapy are of utmost importance.

Infectious complications associated with monoclonal antibodies and related small molecules

Biologics are increasingly becoming part of routine disease management. As more agents are developed, the challenge of keeping track of indications and side effects is growing. While biologics represent a milestone in targeted and specific therapy, they are not without drawbacks, and the judicious use of these "magic bullets" is essential if their full potential is to be realized. Infectious complications in particular are not an uncommon side effect of therapy, whether as a direct consequence of the agent or because of the underlying disease process. With this in mind, we have reviewed and summarized the risks of infection and the infectious disease-related complications for all FDA-approved monoclonal antibodies and some related small molecules, and we discuss the probable mechanisms involved in immunosuppression as well as recommendations for prophylaxis and treatment of specific disease entities.

Requirement of B cells for generating CD4+ T cell memory

B cells can influence T cell responses by directly presenting Ag or by secreting Ab that binds to Ag to form immunogenic complexes. Conflicting evidence suggests that persisting Ag-Ab complexes propagate long-term T cell memory; yet, other data indicate that memory cells can survive without specific Ag or MHC. In this study, the roles of B cells and Ag-Ab complexes in T cell responses to lymphocytic choriomeningitis virus (LCMV) infection were investigated using B cell-deficient or B cell-competent mice. Despite normal lymphocyte expansion after acute infection, B cell-deficient mice rapidly lost CD4(+) T cell memory, but not CD8(+) T cell memory, during the contraction phase. To determine whether Ag-Ab complexes sustain CD4(+) T cell memory, T cell responses were followed in B cell-transgenic (mIg-Tg) mice that have B cells but neither LCMV-specific Ab nor LCMV-immune complex deposition. In contrast to B cell-deficient mice, mIg-Tg mice retained functional Th cell memory, indicating that B cells selectively preserve CD4(+) T cell memory independently of immune complex formation. An in vivo consequence of losing CD4(+) T cell memory was that B cell-deficient mice were unable to resolve chronic virus infection. These data implicate a B cell function other than Ab production that induces long-term protective immunity.

Bone marrow transplantation: new approaches to immunosuppression and management of acute graft-versus-host disease

PURPOSE OF REVIEW

Acute graft-versus-host disease (GVHD) significantly limits the application and the success of allogeneic hematopoietic stem cell transplantation (HSCT). Novel therapies that target the aberrant immune response underlying GVHD are reviewed with particular emphasis on immunomodulatory agents currently incorporated into clinical trials. In addition, regenerative stromal cellular therapy (RSCT) is discussed as an emerging form of novel GVHD therapy.

RECENT FINDINGS

Knowledge for transplant immunology, particularly as it relates to underlying pathophysiology of GVHD, has dramatically increased over the last decade. As a result, new immunomodulatory therapies have been used to treat steroid-refractory GVHD. However, their success has been limited by their lack of clinical experience during HSCT as well as by their associated toxicity profiles. RSCT uniquely offers the potential to enhance donor-derived hematopoiesis and immunity and to ameliorate adverse sequelae associated with GVHD.

SUMMARY

An exciting era incorporating the use of cellular therapeutics during HSCT has arrived. As the experience and understanding for cellular therapies, in general, and RSCT, in particular, increases, so too will their success in benefiting the HSCT recipient beyond limitations of current pharmaceutical agents.