Publications

HIV has evolved sophisticated mechanisms to avoid restriction by intracellular innate immune defenses that otherwise serve to control acute viral infection and virus dissemination. Innate defenses are triggered when pattern recognition receptor (PRR) proteins of the host cell engage pathogen-associated molecule patterns (PAMPs) present in viral products. Interferon regulatory factor 3 (IRF3) plays a central role in PRR signaling of innate immunity to drive the expression of type I interferon (IFN) and interferon-stimulated genes (ISGs), including a variety of HIV restriction factors, that serve to limit viral replication directly and/or program adaptive immunity. Productive infection of T cells by HIV is dependent upon the targeted proteolysis of IRF3 that occurs through a virus-directed mechanism that results in suppression of innate immune defenses. However, the mechanisms by which HIV controls innate immune signaling and IRF3 function are not defined. Here, we examined the innate immune response induced by HIV strains identified through their differential control of PRR signaling. We identified viruses that, unlike typical circulating HIV strains, lack the ability to degrade IRF3. Our studies show that IRF3 regulation maps specifically to the HIV accessory protein Vpu. We define a molecular interaction between Vpu and IRF3 that redirects IRF3 to the endolysosome for proteolytic degradation, thus allowing HIV to avoid the innate antiviral immune response. Our studies reveal that Vpu is an important IRF3 regulator that supports acute HIV infection through innate immune suppression. These observations define the Vpu-IRF3 interface as a novel target for therapeutic strategies aimed at enhancing the immune response to HIV.

PURPOSE

Severe hemorrhagic cystitis is a major complication in the pediatric population undergoing hematopoietic stem cell transplantation. Percutaneous nephrostomy tube drainage as a treatment for severe hemorrhagic cystitis has rarely been investigated. We examined children undergoing hematopoietic stem cell transplantation for risk factors associated with severe hemorrhagic cystitis, as well as our experience with percutaneous nephrostomy tube placement as an adjunctive management strategy.

MATERIALS AND METHODS

Using prospectively collected data from the Blood and Marrow Transplant Database at the University of Minnesota, we reviewed 40 pediatric patients with severe hemorrhagic cystitis from 1996 to 2010. Specific treatment for each patient was administered at the discretion of the attending physician and generally included bladder irrigation before bladder fulguration or percutaneous nephrostomy tube placement. A percutaneous nephrostomy tube was placed in 11 patients due to the intractable nature of the hemorrhagic cystitis.

RESULTS

Of the 11 patients who underwent percutaneous nephrostomy tube drainage 5 (45%) had improvement of the hemorrhagic cystitis within 30 days and the same number had long-term resolution. Among the patients with long-term resolution hemorrhagic cystitis resolved an average of 12.4 days after percutaneous nephrostomy tube placement, and the tubes were removed an average of 8.8 weeks after placement. Through September 2011 mortality among patients with percutaneous nephrostomy tubes was 55% (6 of 11 patients), which was identical to the overall mortality in the severe hemorrhagic cystitis group (22 of 40). No death could be directly attributed to hemorrhagic cystitis or percutaneous nephrostomy tube placement.

CONCLUSIONS

Placement of percutaneous nephrostomy tubes for treatment of severe hemorrhagic cystitis results in long-term improvement in intractable hemorrhagic cystitis, and is a safe and viable option for the majority of patients.