Long-term asymptomatic human immunodeficiency virus (HIV)-infected individuals (LTA) usually have low viral load and low immune activation. To discern whether viral load or immune activation is dominant in determining progression to AIDS, we studied three exceptional LTA with high viral loads. HIV type 1 isolates from these LTA were as pathogenic as viruses from progressors in organ culture. Despite high viral loads, these LTA had low levels of proliferating and activated T cells compared to progressors, like other LTA. In contrast to those in progressors, HIV-specific CD4؉ T-cell responses in these LTA were maintained. Thus, low immune activation despite a high viral load preserved HIV-specific T-cell responses and resulted in a long-term asymptomatic phenotype.

Natural killer (NK) cell activity is conserved throughout vertebrate development, but characterization of non-mammalian NK-cells has been hampered by the absence of specific mAbs for these cells. Monoclonal antibodies were generated against in vitro IL-2 expanded sorted CD3-CD8alpha+ peripheral blood lymphocytes, previously described to contain chicken NK-cells. Screening of embryonic and adult splenocytes with hybridoma supernatants resulted in five candidate NK markers. Activation of chicken NK-cells with PMA/Ionomycin or with the NK target cell-line LSCC-RP9 resulted in increased expression of CD107 (LAMP-1) and a newly developed flow cytometry based cytotoxicity assay showed that NK-cells were able to kill target cells. Combining NK markers with functional assays indicated that marker positive cells showed NK-cell function. In conclusion, we generated new monoclonal antibodies and developed two functional assays which will enhance our understanding of the role of NK-cells in healthy and diseased chickens.

Highly pathogenic avian influenza (HPAI) H5N1 viruses cause severe infection in chickens at near complete mortality, but corresponding infection in ducks is typically mild or asymptomatic. To understand the underlying molecular differences in host response, primary chicken and duck lung cells, infected with two HPAI H5N1 viruses and a low pathogenicity avian influenza (LPAI) H2N3 virus, were subjected to RNA expression profiling. Chicken cells but not duck cells showed highly elevated immune and pro-inflammatory responses following HPAI virus infection. HPAI H5N1 virus challenge studies in chickens and ducks corroborated the in vitro findings. To try to determine the underlying mechanisms, we investigated the role of signal transducer and activator of transcription-3 (STAT-3) in mediating pro-inflammatory response to HPAIV infection in chicken and duck cells. We found that STAT-3 expression was down-regulated in chickens but was up-regulated or unaffected in ducks in vitro and in vivo following H5N1 virus infection. Low basal STAT-3 expression in chicken cells was completely inhibited by H5N1 virus infection. By contrast, constitutively active STAT-3 detected in duck cells was unaffected by H5N1 virus infection. Transient constitutively-active STAT-3 transfection in chicken cells significantly reduced pro-inflammatory response to H5N1 virus infection; on the other hand, chemical inhibition of STAT-3 activation in duck cells increased pro-inflammatory gene expression following H5N1 virus infection. Collectively, we propose that elevated pro-inflammatory response in chickens is a major pathogenicity factor of HPAI H5N1 virus infection, mediated in part by the inhibition of STAT-3.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-014-0118-3) contains supplementary material, which is available to authorized users.

Our data indicate that insufficient help of CD4(+) T cells may cause loss of IFN- gamma -producing CD8(+) T cells and loss of control of CMV dissemination. Increasing CMV-infected cell counts in the face of high CMV-specific perforin- and granzyme B-expressing CD8(+) T cell counts may explain the immune pathological characteristics of CMV disease.

Major distinctive features of avian lungs are the absence of draining lymph nodes and alveoli and alveolar macrophages (MPhs). However, a large network of MPhs and dendritic cells (DCs) is present in the mucosa of the larger airways and in the linings of the parabronchi. For the modulation of respiratory tract immune responses, for example, by vaccination, a better understanding of Ag uptake in the chicken respiratory tract is needed. In this study, we provide detailed characterization of APCs in chicken lungs, including their functional in vivo activities as measured by the uptake of fluorescently labeled 1-μm beads that are coated with either LPS or inactivated avian influenza A virus (IAV) mimicking the uptake of bacterial or viral Ag. We identified different subsets of MPhs and DCs in chicken lungs, based on the expression of CD11, activation markers, and DEC205. In vivo uptake of LPS- and IAV-beads resulted in an increased percentage MHC class II+ (MHC II+) cells and in the upregulation of CD40. The uptake of LPS-beads resulted in the upregulation of CD80 and MHC II on the cell surface, suggesting either uptake of LPS- and IAV-beads by different subsets of phagocytic cells or LPS-mediated differential activation. Differences in phagosomal acidification indicated that in chicken lungs the MHC II+ and CD80+ bead+ cell population includes DCs and that a large proportion of beads was taken up by MPhs. LPS-bead+ cells were present in BALT, suggesting local induction of immune responses. Collectively, we characterized the uptake of Ags by phagocytes in the respiratory tract of chickens.