Reduction of CFU-GM and circulating hematopoietic progenitors in a subgroup of children with chronic neutropenia associated with severe infections and delayed recovery.

Myelopoiesis was evaluated in 66 pediatric patients with chronic neutropenia who were positive for anti-neutrophil antibodies (median age at diagnosis: 11 months, median neutrophil count at diagnosis: 419/µl). Other causes of neutropenia were excluded. Bone marrow morphology, clonogenic tests and/or the peripheral blood CD 34+ cell count, and apoptotic rate were evaluated in 61 patients with neutropenia lasting > 12 months or severe infections. The peripheral blood CD 34+ cell count and apoptotic rate were evaluated in five patients with shorter neutropenia. The median follow-up time was 29 months (range 7-180 months). Forty-seven patients (71.2%) had a spontaneous recovery after 7-180 months (median 29 months). The group of patients younger than 24 months at diagnosis (n = 50) had a higher probability of recovery (40/50 vs. 7/16 χ2 p<0.01) with a shorter period of neutropenia (median 26 versus 47 months, Kaplan-Meier analysis p = 0.001). The colony-forming units-granulocyte-macrophage (CFU-GM) were significantly decreased in 26/35 patients (74%) evaluated for clonogenic tests. All patients with normal CFU-GM recovered (9/9 patients); whereas, neutropenia persisted in 12/26 patients with reduced CFU-GM (46%, Pearson χ2 p = 0.02). In 36/55 (65%) patients evaluated by flow cytometry we observed reduced circulating CD34+ cells compared with controls of the same age. An increase in the circulating CD34+ cell apoptotic rate was observed in 28/55 patients (51%). Infections requiring hospitalization were observed in 9/18 (50%; Pearson χ2, p = 0.03) patients with both decreased circulating CD34+ cells and increased CD34+ apoptotic rates. In the group aged < 24 months, we observed a significant correlation between the persistence of neutropenia and decreased circulating CD34+ cells (Pearson χ2 p = 0.008). In conclusion, reduced CFU-GM and circulating hematopoietic progenitors were observed in a subgroup of children with chronic neutropenia who were positive for anti-neutrophil antibodies and had a higher incidence of severe infections and delayed spontaneous remission.

Exploring mucosal immunization with a recombinant influenza virus carrying an HIV-polyepitope in mice with pre-existing immunity to influenza.

HIV-1 vaccines based on recombinant vectors have been developed to elicit immune responses; however, the failure of the STEP HIV-1 vaccine trial has caused concern regarding the impact on vaccine efficacy of pre-existing vector seropositivity in humans. By using a mouse model of infection, we evaluated the immune responses elicited by intranasal and vaginal immunization with the recombinant influenza virus WSN/CKG carrying the PCLUS3-P18 peptide and a Gag epitope in its hemagglutinin, and the impact of pre-existing vector immunity on protection against recombinant vaccinia virus challenge. We found that despite the protective immunity induced in naïve mice by the WSN/CKG virus via either route, the vaginal immunization of mice with pre-existing influenza immunity restricted vPE16 replication more significantly in the ovaries than intranasal immunization. Thus, successful vaccination strategies under limiting conditions, such as pre-existing vector immunity, require the local induction of mucosal immunity at the site of virus infection.

Efficient vagina-to-lower respiratory tract immune trafficking in a murine model of influenza A virus infection.

Effective vaccination strategies for infectious diseases take into account the induction, long-term maintenance and recall of memory T-cell populations. To understand the immunological cross-talk within the mucosal compartments, we compared intranasal to vaginal immunization and demonstrated that vaginal infection of BALB/c mice with influenza A virus provides protective mucosal immunity against both homosubtypic and heterosubtypic virus challenge in the respiratory tract. We found that, prior to the viral challenge, in vaginally primed mice, antigen-specific CD8+ T cells were not detected in the lung airways and levels of serum antibodies were lower than those observed in intranasally immunized mice. However, following pulmonary challenge, NP147-specific CD8+ T cells were recruited and amplified in vaginally primed mice to the same extent as those in intranasally primed mice. Thus, the long-term memory immune response elicited by vaginal immunization with influenza virus is efficiently recalled and offers reasonable protection against infection in the respiratory tract.

Increased sensitivity of SARS-coronavirus to a combination of human type I and type II interferons.

There is currently an urgent need to identify effective antiviral agents that will prevent and treat severe acute respiratory syndrome coronavirus (SARS-CoV) infection. In this study, we have investigated and compared the antiviral effect of different interferons (IFNs) on SARS-CoV replication in the epithelial kidney monkey Vero cell line. The results showed that SARS-CoV grown in Vero cells is moderately sensitive to IFN-beta and only weakly sensitive to IFN-alpha and IFN-gamma, in comparison to other IFN-sensitive viruses, such as those for encephalomyocarditis, vesicular stomatitis and Newcastle disease. Simultaneous incubation of Vero cells with IFN-beta and IFN-gamma indicated that they may act synergistically against SARS-CoV replication. The IFN-induced MxA protein was detected in the IFN-treated Vero cells. The data, however, suggest that the antiviral activity of IFN against SARS-CoV virus is independent of MxA expression.