Pandemic influenza viruses often cause severe disease in middle-aged adults without preexistent co-morbidities. The mechanism of illness associated with severe disease in this age group is not well understood1–10. Here, we demonstrate preexisting serum antibody that cross-reacts with, but does not protect against 2009 H1N1 influenza virus in middle-aged adults. Non-protective antibody is associated with immune complex(IC)-mediated disease after infection. High titers of serum antibody of low avidity for H1-2009 antigen, and low avidity pulmonary ICs against the same protein were detected in severely ill patients. Moreover, C4d deposition - a sensitive marker of complement activation mediated by ICs- was present in lung sections of fatal cases. Archived lung sections from adults with confirmed fatal influenza 1957 H2N2 infection revealed a similar mechanism of illness. These observations provide a novel biological mechanism for the unusual age distribution of severe cases during influenza pandemics.

Background Few community studies have measured the incidence, severity, and etiology of acute respiratory illness (ARI) among children living at high-altitude in remote rural settings. Methods We conducted active, household-based ARI surveillance among children aged <3 years in rural highland communities of San Marcos, Cajamarca, Peru from May 2009 through September 2011 (RESPIRA-PERU study). ARI (defined by fever or cough) were considered lower respiratory tract infections (LRTI) if tachypnea, wheezing, grunting, stridor, or retractions were present. Nasal swabs collected during ARI episodes were tested for respiratory viruses by real-time reverse-transcriptase polymerase chain reaction. ARI incidence was calculated using Poisson regression. Results During 755.1 child-years of observation among 892 children in 58 communities, 4,475 ARI were observed, yielding an adjusted incidence of 6.2 ARI/child-year (95% CI 5.9 – 6.5). Families sought medical care for 24% of ARI, 4% were classified as LRTI, and 1% led to hospitalization. Two of five deaths among cohort children were attributed to ARI. One or more respiratory virus was detected in 67% of 3957 samples collected. Virus-specific incidence rates per 100 child-years were: rhinovirus, 236; adenovirus, 73; parainfluenza virus, 46; influenza, 37; respiratory syncytial virus, 30; and human metapneumovirus, 17. Respiratory syncytial virus, metapneumovirus, and parainfluenza virus 1-3 comprised a disproportionate share of LRTI compared to other etiologies. Conclusions In this high-altitude rural setting with low population density, ARI in young children were common, frequently severe, and associated with a number of different respiratory viruses. Effective strategies for prevention and control of these infections are needed.

Background Human metapneumovirus (HMPV) is a paramyxovirus with multiple genetic lineages that is a leading cause of acute respiratory disease. Several RT-PCR assays have been described based on limited available sequence data. Objectives To develop a broadly reactive real-time RT-PCR assay for HMPV that allows for a rapid, sensitive, and specific detection in a clinical or research setting. Study Design Three published assays for HMPV were modified based on analysis of multiple HMPV sequences obtained from GenBank. Original and modified assays were tested against prototype HMPV strains from each genetic sublineage, multiple isolates of HMPV from different years, a collection of clinical specimens, and commercial validation panels. Results A number of potential sequence mismatches with diverse HMPV strains were identified. Modifications were made to oligonucleotides to improve annealing efficiency. Primers and probes based on newer sequence data offered enhanced detection of all subgroups, especially for low titer specimens. The new primers and probe detected multiple clinical isolates of HMPV collected over a twenty-year period. The modified assay improved detection of HMPV in a panel of clinical specimens, and correctly identified HMPV samples in two commercial validation sets. Conclusions We report a modified real-time RT-PCR assay for HMPV that detects all genetic lineages with high sensitivity.

Sarcoidosis is characterized by noncaseating granulomas containing CD4 1 T cells with a Th1 immunophenotype. Although the causative antigens remain unknown, independent studies noted molecular and immunologic evidence of mycobacterial virulence factors in sarcoidosis specimens. A major limiting factor in discovering new insights into the pathogenesis of sarcoidosis is the lack of an animal model. Using a distinct superoxide dismutase A peptide (sodA) associated with sarcoidosis granulomas, we developed a pulmonary model of sarcoidosis granulomatous inflammation. Mice were sensitized by a subcutaneous injection of sodA, incorporated in incomplete Freund's adjuvant (IFA). Control subjects consisted of mice with no sensitization (ConNS), sensitized with IFA only (ConIFA), or with Schistosoma mansoni eggs. Fourteen days later, sensitized mice were challenged by tail-vein injection of naked beads, covalently coupled to sodA peptides or to schistosome egg antigens (SEA). Histologic analysis revealed hilar lymphadenopathy and noncaseating granulomas in the lungs of sodA-treated or SEA-treated mice. Flow cytometry of bronchoalveolar lavage (BAL) demonstrated CD4 1 T-cell responses against sodA peptide in the sodA-sensitized mice only. Cytometric bead analysis revealed significant differences in IL-2 and IFN-g secretion in the BAL fluid of sodA-treated mice, compared with mice that received SEA or naked beads (P 5 0.008, Wilcoxon rank sum test). ConNS and ConIFA mice demonstrated no significant formation of granuloma, and no Th1 immunophenotype. The use of microbial peptides distinct for sarcoidosis reveals a histologic and immunologic profile in the murine model that correlates well with those profiles noted in human sarcoidosis, providing the framework to investigate the molecular basis for the progression or resolution of sarcoidosis.

BackgroundThe Respiratory Infections in Andean Peruvian Children (RESPIRA-PERU) study enrolled children who participated in a community-cluster randomized trial of improved stoves, solar water disinfection, and kitchen sinks (IHIP trial) and children from additional Andean households. We quantified the burden of influenza-associated acute respiratory illness (ARI) in this household-based cohort.MethodsFrom May 2009 to September 2011, we conducted active weekly ARI surveillance in 892 children age <3 years, of whom 272 (30.5%) had participated in the IHIP trial. We collected nasal swabs during ARI, tested for influenza and other respiratory viruses by RT-PCR, and determined influenza incidence and risk factors using mixed-effects regression models.ResultsThe overall incidence of influenza-associated ARI was 36.6/100 child-years; incidence of influenza A, B, and C was 20.5, 8.7, and 5.2/100 child-years, respectively. Influenza C was associated with fewer days of subjective fever (median 1 vs. 2) and malaise (median 0 vs. 2) compared to influenza A. Non-influenza ARI also resulted in fewer days of fever and malaise, and fewer healthcare visits than influenza A-associated ARI. Influenza incidence varied by calendar year (80% occurred in the 2010 season) and IHIP trial participation. Among households that participated in the IHIP trial, influenza-associated ARI incidence was significantly lower in intervention than in control households (RR 0.40, 95% CI: 0.20–0.82).ConclusionsInfluenza burden is high among Andean children. ARI associated with influenza A and B had longer symptom duration and higher healthcare utilization than influenza C-associated ARI or non-influenza ARI. Environmental community interventions may reduce influenza morbidity.