Robert L. Atmar

Immune reconstitution inflammatory syndrome. Emergence of a unique syndrome during highly active antiretroviral therapy

The discovery of effective therapy for human immunodeficiency virus (HIV) infection has improved the outlook for patients with the acquired immunodeficiency syndrome (AIDS) (75, 88, 115, 121, 134). Since the introduction of highly active antiretroviral therapy (HAART), there has been a decrease in the incidence of opportunistic infections among HIVinfected patients along with a corresponding reduction in the mortality rate (7, 30, 45, 102, 117). The basis for these improvements appears to be a result of partial recovery of the host’s immune system. Suppression of viral replication by antiretroviral therapy allows for the reappearance of immune effector cells, that in turn, provide vital protection against opportunistic pathogens (15, 32, 92, 95, 132). However beneficial HAART has been, experience during the past several years has disclosed the emergence, in a small proportion of cases, of a unique set of complications. Soon after treatment is begun, some patients experience clinical deterioration due to restoration of their capacity to mount an inflammatory immune response against both infectious and noninfectious antigens. This phenomenon which carries such labels as the immune reconstitution syndrome (IRS) and immune restoration disease (IRD), has been described for a wide variety of infectious pathogens (26, 36, 46). The manifestations of this syndrome are diverse and depend on the particular infectious agent involved. Given that an increased inflammatory response underlies its presentation, we propose the name immune reconstitution inflammatory syndrome (IRIS). Autoimmune diseases that occur following institution of HAART may also be considered as part of the same process. For the purpose of this review, IRIS is defined as a paradoxical deterioration in clinical status attributable to the recovery of the immune system during HAART. Recognition of this entity is crucial, for successful treatment relies on alleviation of the patient’s symptoms without compromising antiretroviral or antimicrobial therapy. In this article, we review the present understanding of the basic science underlying IRIS, with illustrative examples from our case series, and review the existing clinical literature.

Norwalk virus shedding after experimental human infection.

Noroviruses are shed in feces up to 8 weeks after infection.

Use of the selective oral neuraminidase inhibitor oseltamivir to prevent influenza

BACKGROUND Safe and effective antiviral agents are needed to prevent infection with influenza A and B virus. Oseltamivir (GS4104), which can be administered orally, is the prodrug of GS4071, a potent and selective inhibitor of influenzavirus neuraminidases. We studied the use of oseltamivir for long-term prophylaxis against influenza in two placebo-controlled, double-blind trials at different U.S. sites during the winter of 1997-1998. METHODS We randomly assigned 1559 healthy, nonimmunized adults 18 to 65 years old to receive either oral oseltamivir (75 mg given once or twice daily, for a total daily dose of 75 or 150 mg) or placebo for six weeks during a peak period of local influenzavirus activity. The primary end point with respect to efficacy was laboratory-confirmed influenza-like illness (defined as a temperature of at least 37.2 degrees C accompanied by at least one respiratory and at least one systemic symptom). RESULTS In the two studies combined, the risk of influenza among subjects assigned to either once-daily or twice-daily oseltamivir (1.2 percent and 1.3 percent, respectively) was lower than that among subjects assigned to placebo (4.8 percent; P<0.001 and P=0.001 for the comparison with once-daily and twice-daily oseltamivir, respectively). The protective efficacy of oseltamivir in the two active-treatment groups combined was 74 percent (95 percent confidence interval, 53 to 88 percent) at all the sites combined and 82 percent (95 percent confidence interval, 60 to 93 percent) at sites in Virginia, where the rate of influenza infection was higher than the overall rate. For culture-proved influenza, the rate of protective efficacy in the two oseltamivir groups combined was 87 percent (95 percent confidence interval, 65 to 96 percent). The rate of laboratory-confirmed influenza infection was lower with oseltamivir than with placebo (5.3 percent vs. 10.6 percent, P<0.001). Oseltamivir was well tolerated but was associated with a greater frequency of nausea (12.1 percent and 14.6 percent in the once-daily and twice-daily groups, respectively) and vomiting (2.5 percent and 2.7 percent, respectively) than was placebo (nausea, 7.1 percent; vomiting, 0.8 percent). However, the frequency of premature discontinuation of drug or placebo was similar among the three groups (3.1 to 4.0 percent). CONCLUSIONS Oseltamivir administered daily for six weeks by the oral route is safe and effective for the prevention of influenza.

Diagnosis of noncultivatable gastroenteritis viruses, the human caliciviruses.

SUMMARY Gastroenteritis is one of the most common illnesses of humans, and many different viruses have been causally associated with this disease. Of those enteric viruses that have been established as etiologic agents of gastroenteritis, only the human caliciviruses cannot be cultivated in vitro. The cloning of Norwalk virus and subsequently of other human caliciviruses has led to the development of several new diagnostic assays. Antigen detection enzyme immunoassays (EIAs) using polyclonal hyperimmune animal sera and antibody detection EIAs using recombinant virus-like particles have supplanted the use of human-derived reagents, but the use of these assays has been restricted to research laboratories. Reverse transcription-PCR assays for the detection of human caliciviruses are more widely available, and these assays have been used to identify virus in clinical specimens as well as in food, water, and other environmental samples. The application of these newer assays has significantly increased the recognition of the importance of human caliciviruses as causes of sporadic and outbreak-associated gastroenteritis.

Effects of Requiring Prior Authorization for Selected Antimicrobials: Expenditures, Susceptibilities, and Clinical Outcomes

Antimicrobial control programs are widely used to decrease drug expenditures, but effects on antimicrobial resistance and outcomes for patients are unknown. When a requirement for prior authorization for selected parenteral antimicrobial agents was initiated at our urban, county teaching hospital, total parenteral antimicrobial expenditures decreased by 32%. Susceptibilities to all beta-lactam and quinolone antibiotics increased, with dramatic increased susceptibilities in isolates recovered in intensive care units, increased susceptibilities in isolates recovered in other inpatient sites, and little change in susceptibilities in isolates recovered in outpatient sites despite no change in infection control practices. For patients with bacteremia due to gram-negative organisms, overall survival did not change with restrictions. No differences occurred in the median time from initial positive blood culture to receipt of an appropriate antibiotic or in the median time from positive blood culture to discharge from the hospital. Thus, requiring preapproval for selected parenteral agents can decrease antimicrobial expenditures and improve susceptibilities to antibiotics without compromising patient outcomes or length of hospital stay.

Norovirus Vaccine against Experimental Human Norwalk Virus Illness

BACKGROUND Noroviruses cause epidemic and sporadic acute gastroenteritis. No vaccine is available to prevent norovirus illness or infection. METHODS We conducted a randomized, double-blind, placebo-controlled, multicenter trial to assess the safety, immunogenicity, and efficacy of an investigational, intranasally delivered norovirus viruslike particle (VLP) vaccine (with chitosan and monophosphoryl lipid A as adjuvants) to prevent acute viral gastroenteritis after challenge with a homologous viral strain, Norwalk virus (genotype GI.1). Healthy adults 18 to 50 years of age received two doses of either vaccine or placebo and were subsequently inoculated with Norwalk virus and monitored for infection and gastroenteritis symptoms. RESULTS Ninety-eight persons were enrolled and randomly assigned to receive vaccine (50 participants) or placebo (48 participants), and 90 received both doses (47 participants in the vaccine group and 43 in the placebo group). The most commonly reported symptoms after vaccination were nasal stuffiness, nasal discharge, and sneezing. Adverse events occurred with similar frequency among vaccine and placebo recipients. A Norwalk virus-specific IgA seroresponse (defined as an increase by a factor of 4 in serum antibody levels) was detected in 70% of vaccine recipients. Seventy-seven of 84 participants inoculated with Norwalk virus were included in the per-protocol analysis. Vaccination significantly reduced the frequencies of Norwalk virus gastroenteritis (occurring in 69% of placebo recipients vs. 37% of vaccine recipients, P=0.006) and Norwalk virus infection (82% of placebo recipients vs. 61% of vaccine recipients, P=0.05). CONCLUSIONS This norovirus VLP vaccine provides protection against illness and infection after challenge with a homologous virus. (Funded by LigoCyte Pharmaceuticals and the National Institutes of Health; ClinicalTrials.gov number, NCT00973284.).

Norovirus disease: changing epidemiology and host susceptibility factors

Abstract Noroviruses cause the majority of acute viral gastroenteritis cases that occur worldwide. The increased recognition of noroviruses as the cause of outbreaks and sporadic disease is due to the recent availability of improved norovirus-specific diagnostics. Transmission of these viruses is facilitated by their high prevalence in the community, shedding of infectious virus particles from asymptomatic individuals and the high stability of the virus in the environment. Currently, the spectrum of clinical disease and the understanding of host susceptibility factors are changing. Cases of chronic norovirus gastroenteritis have been observed in transplant recipients and unusual clinical presentations have been recognized in otherwise healthy adults that are under physical stress. Recently, noroviruses were found to bind to gut-expressed carbohydrates, leading to a correlation between a persons genetically determined carbohydrate expression and their susceptibility to Norwalk virus infection. Greater community surveillance and further investigation of carbohydrate receptor-binding properties could provide further insights into norovirus transmission, susceptibility and pathogenesis, and should aid in developing vaccines and antiviral therapies for this common viral disease.

The Role of Immune Reconstitution Inflammatory Syndrome in AIDS-Related Cryptococcus neoformans Disease in the Era of Highly Active Antiretroviral Therapy

This study of human immunodeficiency virus (HIV)-infected patients coinfected with Cryptococcus neoformans found that 30% of patients who initiated highly active antiretroviral therapy developed immune reconstitution inflammatory syndrome (IRIS). Patients with C. neoformans-related IRIS had higher cerebrospinal fluid opening pressures, glucose levels, and white blood cell counts, compared with patients with typical HIV-associated C. neoformans meningitis.

Replication of human noroviruses in stem cell–derived human enteroids

The major barrier to research and development of effective interventions for human noroviruses (HuNoVs) has been the lack of a robust and reproducible in vitro cultivation system. HuNoVs are the leading cause of gastroenteritis worldwide. We report the successful cultivation of multiple HuNoV strains in enterocytes in stem cell–derived, nontransformed human intestinal enteroid monolayer cultures. Bile, a critical factor of the intestinal milieu, is required for strain-dependent HuNoV replication. Lack of appropriate histoblood group antigen expression in intestinal cells restricts virus replication, and infectivity is abrogated by inactivation (e.g., irradiation, heating) and serum neutralization. This culture system recapitulates the human intestinal epithelium, permits human host-pathogen studies of previously noncultivatable pathogens, and allows the assessment of methods to prevent and treat HuNoV infections.

Norwalk Virus-Like Particle Hemagglutination by Binding to H Histo-Blood Group Antigens

ABSTRACT Noroviruses are a major cause of epidemic acute nonbacterial gastroenteritis worldwide. Here we report our discovery that recombinant Norwalk virus virus-like particles (rNV VLPs) agglutinate red blood cells (RBCs). Since histo-blood group antigens are expressed on gut mucosa as well as RBCs, we used rNV VLP hemagglutination (HA) as a model system for studying NV attachment to cells in order to help identify a potential NV receptor(s). rNV VLP HA is dependent on low temperature (4°C) and acidic pH. Of the 13 species of RBCs tested, rNV VLPs hemagglutinated only chimpanzee and human RBCs. The rNV VLPs hemagglutinated all human type O (11 of 11), A (9 of 9), and AB (4 of 4) RBCs; however, few human type B RBC samples (4 of 14) were hemagglutinated. HA with periodate- and neuraminidase-treated RBCs indicated that rNV VLP binding was carbohydrate dependent and did not require sialic acid. The rNV VLPs did not hemagglutinate Bombay RBCs (zero of seven) that lack H type 2 antigen, and an anti-H type 2 antibody inhibited rNV VLP HA of human type O RBCs. These data indicated that the H type 2 antigen functions as the rNV VLP HA receptor on human type O RBCs. The rNV VLP HA was also inhibited by rNV VLP-specific monoclonal antibody 8812, an antibody that inhibits VLP binding to Caco-2 cells. Convalescent-phase sera from NV-infected individuals showed increased rNV VLP HA inhibition titers compared to prechallenge sera. In carbohydrate binding assays, the rNV VLPs bound to synthetic Lewis d (Led), Leb, H type 2, and Ley antigens, and these antigens also inhibited rNV VLP HA of human type O RBCs. Overall, our results indicate that carbohydrate antigens in the gut are a previously unrecognized factor in NV pathogenesis.