Supportive care

Cotton rat model for testing vaccines and antivirals against respiratory syncytial virus

Respiratory syncytial virus is the leading cause of pneumonia and bronchiolitis in infants and is a serious health risk for elderly and immunocompromised individuals. No vaccine has yet been approved to prevent respiratory syncytial virus infection and the only available treatment is immunoprophylaxis of severe respiratory syncytial virus disease in high-risk infants with Palivizumab (Synagis^®). The development of respiratory syncytial virus vaccine has been hampered by the phenomenon of enhanced respiratory syncytial virus disease observed during trials of a formalin-inactivated respiratory syncytial virus in 1960s. A search for effective respiratory syncytial virus therapeutics has been complicated by the fact that some of the most advanced respiratory syncytial virus antivirals, while highly effective in a prophylactic setting, had not demonstrated clinical efficacy when given after infection. A number of respiratory syncytial virus vaccines and antivirals are currently under development, including several vaccines proposed for maternal immunization. The cotton rat Sigmodon hispidus is an animal model of respiratory syncytial virus infection with demonstrated translational value. Special cohort scenarios, such as infection under conditions of immunosuppression and maternal immunization have been modeled in the cotton rat and are summarized here. In this review, we focus on the recent use of the cotton rat model for testing respiratory syncytial virus vaccine and therapeutic candidates in preclinical setting, including the use of special cohort models. An overview of published studies spanning the period of the last three years is provided. The emphasis, where possible, is made on candidates in the latest stages of preclinical development or currently in clinical trials.

Treatment with novel RSV Ig RI-002 controls viral replication and reduces pulmonary damage in immunocompromised Sigmodon hispidus

Respiratory syncytial virus (RSV) is a significant cause of bronchiolitis and pneumonia in several high health risk populations, including infants, elderly and immunocompromised individuals. Mortality in hematopoietic stem cell transplant recipients with lower respiratory tract RSV infection can exceed 80%. It has been shown that RSV replication in immunosuppressed individuals is significantly prolonged, but the contribution of pulmonary damage, if any, to the pathogenesis of RSV disease in this susceptible population is not known. In this work, we tested RI-002, a novel standardized Ig formulation containing a high level of RSV-neutralizing Ab, for its ability to control RSV infection in immunocompromised cotton rats Sigmodon hispidus. Animals immunosuppressed by repeat cyclophosphamide injections were infected with RSV and treated with RI-002. Prolonged RSV replication, characteristic of immunosuppressed cotton rats, was inhibited by RI-002 administration. Ab treatment reduced detection of systemic dissemination of viral RNA. Importantly, pulmonary interstitial inflammation and epithelial hyperplasia that were significantly elevated in immunosuppressed animals were reduced by RI-002 administration. These results indicate the potential of RI-002 to improve outcome of RSV infection in immunocompromised subjects not only by controlling viral replication, but also by reducing damage to lung parenchyma and epithelial airway lining, but further studies are needed.

Serum Aspergillus galactomannan antigen values strongly correlate with outcome of invasive aspergillosis

BACKGROUND

Determining the outcome of patients with aspergillosis can be particularly difficult because patients with aspergillosis are at risk for other conditions that mimic this infection. Galactomannan is an Aspergillus-specific antigen released during invasive aspergillosis and is detected by the quantitative serum galactomannan index (GMI) test.

METHODS

Using a kappa correlation coefficient test (KCC), the strength of correlation was determined between GMI and survival outcome of aspergillosis among 56 adults with hematologic cancer (90% had myeloma) who underwent serial GMI monitoring until hospital discharge or death.

RESULTS

All 56 patients received antineoplastic therapy (myeloablative followed by stem cell transplantation [autologous in 21 patients and allogeneic in 3 patients] or nonmyeloablative therapy [32 patients]). The overall correlation between survival outcome and GMI was excellent (KCC = 0.8609; 95% confidence interval [95% CI], 0.7093-1.000 [P < .0001]) and was comparable among neutropenic and nonneutropenic patients (KCC = 0.8271; 95% CI, 0.6407-1.000 [P < .0001] and KCC = 1.0; 95% CI, 1-1 [P = .0083], respectively).

CONCLUSIONS

The survival outcome of patients with aspergillosis strongly correlated with serum GMI. These findings have important implications for patient care and clinical trials of mold-active antifungal agents.

Of Yeasts and Hyphae: A Hematologist’s Approach to Antifungal Therapy

Improvements in anticancer treatments, the ability to modify myelosuppression profiles, greater duration and intensity of immunosuppression, and the variety of available antimicrobial therapies have influenced the spectrum of pathogens associated with invasive fungal infection complicating treatment of hematological malignancies and hematopoietic stem cell transplantation. The approaches to the management of these infections encompass strategies of prevention for all those at risk, pre-emptive therapy based upon surrogates of infection before the onset of clinical disease, empirical therapy for patients with clinical evidence of early disease, and directed or targeted therapy for infected patients with established disease. Chemoprophylaxis is effective if applied to the highest risk patients over the duration of the risk. Pre-emptive strategies, while promising, have yet to be validated and linked to reliably predictive nonmicrobiological diagnostic techniques. Empirical antifungal therapy, as it is currently applied, now seems questionable. Patients with probable or proven invasive fungal infection still have suboptimal outcomes despite the availability of promising anti-fungal agents. Strategies examining the concept of dose-intensity and combination regimens require careful study and cannot yet be regarded as an acceptable standard of practice.

Prospective study of the incidence, clinical features, and outcome of symptomatic upper and lower respiratory tract infections by respiratory viruses in adult recipients of hematopoietic stem cell transplants for hematologic malignancies

Respiratory viruses (RVs) are known to be major causes of morbidity and mortality in recipients of hematopoietic stem cell transplants (HSCTs), but prospective long-term studies are lacking. We prospectively screened all adult HSCT recipients (172 allogeneic [alloHSCT] and 240 autologous [autoHSCT]) who underwent transplantation during a 4-year period (1999 to 2003) for the development of a first episode of symptomatic upper respiratory tract infections and/or lower respiratory tract infections (LRTI) by an RV. RVs studied were influenza A and B viruses (n=39), human respiratory syncytial virus (n=19), human adenoviruses (n=11), human parainfluenza viruses 1 to 3 (n=8), human enteroviruses (n=5), human rhinoviruses (n=3), and the recently discovered human metapneumoviruses (n=19). During the study, 51 and 32 cases of RV symptomatic infections were identified of alloHSCT and autoHSCT recipients (2-year incidence, 29% and 14%, respectively). Risk factors for progression of upper respiratory tract infection to LRTI included severe (<0.2x10(9)/L) and moderate (<0.2x10(9)/L) lymphocytopenia in alloHSCT (P=.02) and autoHSCT (P=.03). Death from LRTI was attributed to an RV in 8 alloHSCT recipients. Symptomatic RV had no effect on 2-year outcomes, with the possible exception of influenza A and B virus infections in autoHSCT: these were associated with nonrelapse mortality (P=.02). In conclusion, this prospective trial allows an estimation of the minimum incidence of a first RV infection in adult HSCT recipients and identifies risk factors for acquisition of an RV infection and progression to LRTI; this should aid in the design of future studies. In addition, human metapneumovirus should be added to the potentially serious causes of RV infections in HSCT.