Granulocyte-Macrophage Colony-Stimulating Factor Expressed by Recombinant Respiratory Syncytial Virus Attenuates Viral Replication and Increases the Level of Pulmonary Antigen-Presenting Cells

Abstract

An obstacle to developing a vaccine against human respiratory syncytial virus (RSV) is that natural infection typically does not confer solid immunity to reinfection. To investigate methods to augment the immune response, recombinant RSV (rRSV) was constructed that expresses murine granulocyte-macrophage colonystimulating factor (mGM-CSF) from a transcription cassette inserted into the G-F intergenic region. Replication of rRSV/mGM-CSF in the upper and lower respiratory tracts of BALB/c mice was reduced 23-to 74-and 5-to 588-fold, respectively, compared to that of the parental rRSV. Despite this strong attenuation of replication, the level of RSV-specific serum antibodies induced by rRSV/mGM-CSF was comparable to, or marginally higher than, that of the parental rRSV. The induction of RSV-specific CD8 ؉ cytotoxic T cells was moderately reduced during the initial infection, which might be a consequence of reduced antigen expression. Respiratory syncytial virus (RSV) is the most important viral etiologic agent of serious pediatric respiratory tract disease worldwide. RSV also is receiving increasing recognition as an important cause of respiratory tract disease in the elderly; in immunocompromised patients, such as bone marrow transplant recipients; and in the general population (reviewed in reference 16). Reinfection by RSV is common, although disease is less severe. A licensed RSV vaccine is not available, but passive immunoprophylaxis with RSV-neutralizing antibody is now available for high-risk infants (2).RSV is a nonsegmented negative-strand RNA virus of the family Paramyxoviridae. RSV encodes 11 proteins (reviewed in references 8, 15, and 16), namely, three transmembrane surface proteins (G, F, and SH); the virion matrix protein M; the nucleocapsid and polymerase proteins N, P, M2-1, and L; the putative transcription-replication regulatory factor M2-2; and two nonstructural proteins, NS1 and NS2, that have been implicated as antagonists of the type I interferon antiviral state (31). While many components of the innate and adaptive immune systems contribute to restricting and resolving an RSV infection, the increased resistance to reinfection that is conferred by prior infection appears to be mediated primarily by RSV-specific secretory and serum antibodies (16,17,27). The F and G glycoproteins are the major RSV neutralization antigens (17).In the 1960s, a formalin-inactivated RSV vaccine evaluated in infants and children was not protective and, paradoxically, was associated with increased frequency and severity of disease during subsequent natural RSV infection (26). It is now understood that the initial vaccination primed for an immunemediated pathogenic response that occurred upon reexposure to viral antigen during the subsequent natural infection, although the details of this phenomenon have not been completely elucidated. One element appears to involve the disproportionate induction of the Th2 subset of CD4 ϩ T helper lymphocytes, characterized by increased secretion of interleukin 4 (IL-4) and . Subunit...

A mouse GM-CSF receptor antibody attenuates neutrophilia in mice exposed to cigarette smoke

“…In addition, mice deficient in GM-CSF exposed either to a viral [31] or bacterial [32] pathogen demonstrated a reduction in IL-12 production. Furthermore, overexpression of GM-CSF in the lungs of normal mice stimulates an increase in IL-12 production [33]. Similarly, we showed that IL-12p40 was upregulated in the lungs of CSexposed mice and that these levels were attenuated with either antibody, indicating that IL-12p40 expression is downstream of CS-induced GM-CSF production.…”

Local CD11c+ MHC Class II− Precursors Generate Lung Dendritic Cells during Respiratory Viral Infection, but Are Depleted in the Process

“…We speculate that large increases in numbers of pulmonary DC are required for effective antibacterial immune responses, exceeding the numbers of DC still present in the lung after RSV infection. A role for lung DC in antibacterial responses is supported by the observation that increased numbers of pulmonary DC, induced by infection with a transgenic RSV strain expressing GM-CSF, resulted in increased titers of specific Abs to this virus (29). Specific Abs are of critical importance in antibacterial immune responses, and their production may well be impaired if numbers of lung DC presenting bacterial Ags are inadequate.…”

Modulation of pulmonary DC function by vaccine‐encoded GM‐CSF enhances protective immunity against Mycobacterium tuberculosis infection

“…delivery of a rBCG strain secreting detectable levels of GM-CSF in situ augments local immunogenicity and demonstrates significant protection against M. tuberculosis infection. GM-CSF is critical to the differentiation of myeloid cells such as DC and macrophages from haematopoietic stem cell precursors, yet in the lung it has been shown to possess unique functions in the regulation of inflammation and host defense against infectious pathogens, as well as pulmonary surfactant and alveolar cell homeostasis [23][24][25][26]. The pattern of GM-CSF production within the lung, with GM-CSF concentrations diminishing over time (Fig.…”