ABSTRACT
Pandemic 2009 H1N1 (pH1N1) influenza viruses caused mild symptoms in most infected patients. However, a greater rate of severe disease was observed in healthy young adults and children without co-morbid conditions. Here we tested whether influenza strains displaying differential virulence could be present among circulating pH1N1 viruses. The biological properties and the genotype of viruses isolated from a patient showing mild disease (M) or from a fatal case (F), both without known co-morbid conditions were compared in vitro and in vivo. The F virus presented faster growth kinetics and stronger induction of cytokines than M virus in human alveolar lung epithelial cells. In the murine model in vivo, the F virus showed a stronger morbidity and mortality than M virus. Remarkably, a higher proportion of mice presenting infectious virus in the hearts, was found in F virus-infected animals. Altogether, the data indicate that strains of pH1N1 virus with enhanced pathogenicity circulated during the 2009 pandemic. In addition, examination of chemokine receptor 5 (CCR5) genotype, recently reported as involved in severe influenza virus disease, revealed that the F virus-infected patient was homozygous for the deleted form of CCR5 receptor (CCR5Δ32).
Subject(s)
Influenza A Virus, H1N1 Subtype/physiology , Influenza, Human/epidemiology , Influenza, Human/virology , Pandemics , Adult , Alleles , Amino Acids/genetics , Animals , Cell Line , Cells, Cultured , Cytokines/metabolism , Epithelial Cells/pathology , Epithelial Cells/virology , Female , Humans , Immunohistochemistry , Influenza A Virus, H1N1 Subtype/genetics , Influenza, Human/pathology , Mice , Mice, Inbred BALB C , Orthomyxoviridae Infections/pathology , Orthomyxoviridae Infections/virology , Pulmonary Alveoli/pathology , Pulmonary Alveoli/virology , Receptors, CCR5/genetics , Viral Load , Virus ReplicationABSTRACT
A human respiratory syncytial virus (HRSV) neutralization escape mutant was obtained after 56 serial passages in the presence of a polyclonal antiserum raised against the F protein. Nucleotide sequence analysis of this escape mutant virus revealed two amino acid substitutions: Asn268Ile and Val533Met. When this virus was allowed to grow in the absence of the anti-F polyclonal serum, only the mutation Asn268Ile was stably maintained. Both the double and single escape mutant viruses lost reactivity with mAbs belonging to antigenic site II of the fusion protein of RSV. Mutation Asn268Ile has already been reported in RS viruses that are resistant to mAbs 47F and 11 and palivizumab (PZ). We have thus identified a novel mutation (Val533Met) in the transmembrane domain of the F protein that was selected under immune pressure.
Subject(s)
Antibodies, Viral/immunology , Immune Evasion , Mutation, Missense , Respiratory Syncytial Virus Infections/virology , Respiratory Syncytial Virus, Human/genetics , Viral Fusion Proteins/genetics , Viral Fusion Proteins/immunology , Amino Acid Motifs , Hep G2 Cells , Humans , Neutralization Tests , Respiratory Syncytial Virus Infections/immunology , Respiratory Syncytial Virus, Human/immunology , Respiratory Syncytial Virus, Human/isolation & purification , Viral Fusion Proteins/chemistryABSTRACT
Human respiratory syncytial virus (HRSV) is the most common cause of severe respiratory infections in infants and young children, often leading to hospitalization. In addition, HRSV poses a serious health risk in immunocompromised individuals and the elderly. It has been reported that this virus can infect mouse antigen-presenting cells, including B lymphocytes. In these B cells, HRSV infection upregulates the expression of activation markers, including MHC class II and CD86, but not MHC class I molecules. Here, we report that HRSV infection of spleen B lymphocytes downregulated TLR4. Either blocking with anti-TLR4 antibody or genetic deletion, but not functional deficiency of TLR4, moderately reduced the infectivity of HRSV in B lymphocytes. HRSV-infected B lymphocytes with deleted TLR4 upregulated MHC class II and CD86 molecules to the same levels as TLR4(+) wild type B cells. Since the activation of monocytes and macrophages by HRSV was previously reported to depend on TLR4, the current study indicates that these cells and B lymphocytes respond to HRSV infection with different activation pathways.
Subject(s)
B-Lymphocytes/immunology , Lymphocyte Activation/immunology , Respiratory Syncytial Virus, Human/immunology , Toll-Like Receptor 4/immunology , Animals , B-Lymphocytes/metabolism , B-Lymphocytes/virology , B7-2 Antigen/immunology , B7-2 Antigen/metabolism , Cell Separation , Cells, Cultured , Female , Flow Cytometry , Histocompatibility Antigens Class II/immunology , Histocompatibility Antigens Class II/metabolism , Host-Pathogen Interactions , Humans , Mice , Mice, Knockout , Respiratory Syncytial Virus, Human/physiology , Toll-Like Receptor 4/genetics , Toll-Like Receptor 4/metabolism , Up-RegulationABSTRACT
Human respiratory syncytial virus (HRSV) is the most common cause of severe respiratory infections in infants and young children, often leading to hospitalization. Although human airway epithelial cells are the main target of HRSV, it has been reported that this virus can also infect professional antigen-presenting cells such as macrophages and dendritic cells, promoting upregulation of maturation markers. Here, we report that mouse spleen B220(+) B lymphocytes were susceptible to HRSV infection in vitro, probably involving a glycosaminoglycan-dependent mechanism. In contrast, neither CD4(+) nor CD8(+) T lymphocytes were infected. In B lymphocytes, HRSV infection upregulated major histocompatibility complex (MHC) class II but not MHC class I molecules and induced the expression of the activation marker CD86.
