Dendritic cells are susceptible to infection with wild-type adenovirus, inducing a differentiation arrest in precursor cells and inducing a strong T-cell stimulation

Bovine Adenovirus-3 Tropism for Bovine Leukocyte Sub-Populations

A number of characteristics including lack of virulence and the ability to grow to high titers, have made bovine adenovirus-3 (BAdV-3) a vector of choice for further development as a vaccine-delivery vehicle for cattle. Despite the importance of blood leukocytes, including dendritic cells (DC), in the induction of protective immune responses, little is known about the interaction between BAdV-3 and bovine blood leukocytes. Here, we demonstrate that compared to other leukocytes, bovine blood monocytes and neutrophils are significantly transduced by BAdV404a (BAdV-3, expressing enhanced yellow green fluorescent protein [EYFP]) at a MOI of 1-5 without a significant difference in the mean fluorescence of EYFP expression. Moreover, though expression of some BAdV-3-specific proteins was observed, no progeny virions were detected in the transduced monocytes or neutrophils. Interestingly, addition of the "RGD" motif at the C-terminus of BAdV-3 minor capsid protein pIX (BAV888) enhanced the ability of the virus to enter the monocytes without altering the tropism of BAdV-3. The increased uptake of BAV888 by monocytes was associated with a significant increase in viral genome copies and the abundance of EYFP and BAdV-3 19K transcripts compared to BAdV404a-transduced monocytes. Our results suggest that BAdV-3 efficiently transduces monocytes and neutrophils in the absence of viral replication. Moreover, RGD-modified capsid significantly increases vector uptake without affecting the initial interaction with monocytes.

Human adenovirus replication and persistence in hypertrophic adenoids and palatine tonsils in children

The role of human adenovirus (HAdV) infection in different acute diseases, such as febrile exudative tonsillitis, conjunctivitis, and pharyngoconjunctival fever is well established. However, the relationships, if any, of HAdV persistence and reactivation in the development of the chronic adenotonsillar disease is not fully understood. The present paper reports a 3-year cross-sectional hospital-based study aimed at detecting and quantifying HAdV DNA and mRNA of the HAdV hexon gene in adenoid and palatine tonsil tissues and nasopharyngeal secretions (NPS) from patients with adenotonsillar hypertrophy or recurrent adenotonsillitis. HAdV C, B, and E were detectable in nearly 50% of the patients, with no association with the severity of airway obstruction, nor with the presence of recurrent tonsillitis, sleep apnea or otitis media with effusion (OME). Despite the higher rates of respiratory viral coinfections in patients with HAdV, the presence of other viruses, including DNA and RNA viruses, had no association with HAdV replication or shedding in secretions. Higher HAdV loads in adenoids showed a significant positive correlation with the presence of sleep apnea and the absence of OME. Although this study indicates that a significant proportion (~85%) of individuals with chronic adenotonsillar diseases have persistent nonproductive HAdV infection, including those by HAdV C, B, and E, epithelial and subepithelial cells in tonsils seem to be critical for HAdV C production and shedding in NPS in some patients, since viral antigen was detected in these regions by immunohistochemistry in four patients, all of which were also positive for HAdV mRNA detection.

Infection with host-range mutant adenovirus 5 suppresses innate immunity and induces systemic CD4+ T cell activation in rhesus macaques

Ad5 is a common cause of respiratory disease and an occasional cause of gastroenteritis and conjunctivitis, and seroconversion before adolescence is common in humans. To gain some insight into how Ad5 infection affects the immune system of rhesus macaques (RM) 18 RM were infected with a host-range mutant Ad5 (Ad5hr) by 3 mucosal inoculations. There was a delay of 2 to 6 weeks after the first inoculation before plasmacytoid dendritic cell (pDC) frequency and function increased in peripheral blood. Primary Ad5hr infection suppressed IFN-γ mRNA expression, but the second Ad5hr exposure induced a rapid increase in IFN-gamma mRNA in peripheral blood mononuclear cells (PBMC). Primary Ad5hr infection suppressed CCL20, TNF and IL-1 mRNA expression in PBMC, and subsequent virus exposures further dampened expression of these pro-inflammatory cytokines. Primary, but not secondary, Ad5hr inoculation increased the frequency of CXCR3+ CD4+ T cells in blood, while secondary, but not primary, Ad5hr infection transiently increased the frequencies of Ki67+, HLADR+ and CD95+/CCR5+ CD4+ T cells in blood. Ad5hr infection induced polyfunctional CD4 and CD8+ T cells specific for the Ad5 hexon protein in all of the animals. Thus, infection with Ad5hr induced a complex pattern of innate and adaptive immunity in RM that included transient systemic CD4+ T cell activation and suppressed innate immunity on re-exposure to the virus. The complex effects of adenovirus infection on the immune system may help to explain the unexpected results of testing Ad5 vector expressing HIV antigens in Ad5 seropositive people.

Heat shock protein 27 mediated signaling in viral infection

Heat shock proteins (HSPs) play a critical role in many intracellular processes, including apoptosis and delivery of other proteins to intracellular compartments. Small HSPs have been shown previously to participate in many cellular functions, including IL-8 induction. Human adenovirus infection activates intracellular signaling, involving particularly the c-Src and mitogen-activated protein kinases [Natarajan, K., et al. (2003) J. Immunol. 170, 6234-6243]. HSP27 and MK2 are also phosphorylated, and c-Src, and its downstream targets, p38, ERK1/2, and c-Jun-terminal kinase (JNK), differentially mediate IL-8 and MCP-1 expression. Specifically, activation and translocation of transcription factor NFκB-p65 occurs in a p38-dependent fashion [Rajaiya, J., et al. (2009) Mol. Vision 15, 2879-2889]. Herein, we report a novel role for HSP27 in an association of p38 with NFκB-p65. Immunoprecipitation assays of virus-infected but not mock-infected cells revealed a signaling complex including p38 and NFκB-p65. Transfection with HSP27 short interfering RNA (siRNA) but not scrambled RNA disrupted this association and reduced the level of IL-8 expression. Transfection with HSP27 siRNA also reduced the level of nuclear localization of NFκB-p65 and p38. By use of tagged p38 mutants, we found that amino acids 279-347 of p38 are necessary for the association of p38 with NFκB-p65. These studies strongly suggest that HSP27, p38, and NFκB-p65 form a signalosome in virus-infected cells and influence downstream expression of pro-inflammatory mediators.

The tug-of-war between dendritic cells and human chronic viruses

The human immune system is under constant challenge from many viruses, some of which the body is successfully able to clear. Other viruses have evolved to escape the host immune responses and thus persist, leading to the development of chronic diseases. Dendritic cells are professional antigen-presenting cells that play a major role in both innate and adaptive immunity against different pathogens. This review focuses on the interaction of different chronic viruses with dendritic cells and the viruses' ability to exploit this critical cell type to their advantage so as to establish persistence within the host.

CD209/DC-SIGN mediates efficient infection of monocyte-derived dendritic cells by clinical adenovirus 2C isolates in the presence of bovine lactoferrin

Adenovirus often causes respiratory infection in immunocompromised patients, but relevant attachment receptors have largely not been defined. We show that the antiviral protein bovine lactoferrin enhances infection of monocyte-derived dendritic cells (MDDC) by adenovirus species C serotype 2 (2C) isolates. Under the same conditions infection of MDDC by human( )cytomegalovirus was reduced. Adenoviral infection was prominently enhanced by bovine but not human lactoferrin, and was not prominently enhanced using blood monocyte-derived macrophages, suggesting that the relevant receptor is expressed on MDDC. Infection of MDDC in the presence of bovine lactoferrin was blocked by mannan, and an antibody to CD209/DC-SIGN but not isotype control or CD46 antibodies. Lastly, U937 macrophages ectopically expressing CD209/DC-SIGN, but not parental U937 cells, were efficiently infected by adenovirus 2C in the presence of bovine lactoferrin. These results may provide a tool, given the high efficiency of infection, to dissect responses by myeloid cells to clinical adenovirus isolates.