RESUMO
The emergence of escape variants of SARS-CoV-2 carrying mutations in the spike protein poses a challenge for therapeutic antibodies. Here, we show that through the comprehensive engineering of the variable region of the neutralizing monoclonal antibody 5A6, the engineered antibody, 5A6CCS1, is able to neutralize SARS-CoV-2 variants that escaped neutralization by the original 5A6 antibody. In addition to the improved affinity against variants, 5A6CCS1 was also optimized to achieve high solubility and low viscosity, enabling a high concentration formulation for subcutaneous injection. In cynomolgus monkeys, 5A6CCS1 showed a long plasma half-life and good subcutaneous bioavailability through engineering of the variable and constant region. These data demonstrate that 5A6CCS1 is a promising antibody for development against SARS-CoV-2 and highlight the importance of antibody engineering as a potential method to counteract escape variants.
Assuntos
COVID-19 , Glicoproteína da Espícula de Coronavírus , Anticorpos Neutralizantes , Anticorpos Antivirais , COVID-19/terapia , Humanos , Glicoproteínas de Membrana , Testes de Neutralização , SARS-CoV-2/genética , Glicoproteína da Espícula de Coronavírus/genética , Proteínas do Envelope ViralRESUMO
NLRP10 is a nucleotide-binding oligomerization domain-like receptor that functions as an intracellular pattern recognition receptor for microbial products. Here, we generated a Nlrp10-/- mouse to delineate the role of NLRP10 in the host immune response and found that Nlrp10-/- dendritic cells (DCs) elicited sub-optimal IFNγ production by antigen-specific CD4+ T cells compared to wild-type (WT) DCs. In response to T-cell encounter, CD40 ligation or Toll-like receptor 9 stimulation, Nlrp10-/- DCs produced low levels of IL-12, due to a substantial decrease in NF-κB activation. Defective IL-12 production was also evident in vivo and affected IFNγ production by CD4+ T cells. Upon Mycobacterium tuberculosis (Mtb) infection, Nlrp10-/- mice displayed diminished T helper 1-cell responses and increased bacterial growth compared to WT mice. These data indicate that NLRP10-mediated IL-12 production by DCs is critical for IFNγ induction in T cells and contributes to promote the host defense against Mtb.
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Gouty arthritis results from the generation of monosodium urate (MSU) crystals within joints. These MSU crystals elicit acute inflammation characterized by massive infiltration of neutrophils and monocytes that are mobilized by the pro-inflammatory cytokine IL-1ß. MSU crystals also activate the complement system, which regulates the inflammatory response; however, it is unclear whether or how MSU-mediated complement activation is linked to IL-1ß release in vivo, and the various roles that might be played by individual components of the complement cascade. Here we show that exposure to MSU crystals in vivo triggers the complement cascade, leading to the generation of the biologically active complement proteins C3a and C5a. C5a, but not C3a, potentiated IL-1ß and IL-1α release from LPS-primed MSU-exposed peritoneal macrophages and human monocytic cells in vitro; while in vivo MSU-induced C5a mediated murine neutrophil recruitment as well as IL-1ß production at the site of inflammation. These effects were significantly ameliorated by treatment of mice with a C5a receptor antagonist. Mechanistic studies revealed that C5a most likely increased NLRP3 inflammasome activation via production of reactive oxygen species (ROS), and not through increased transcription of inflammasome components. Therefore we conclude that C5a generated upon MSU-induced complement activation increases neutrophil recruitment in vivo by promoting IL-1 production via the generation of ROS, which activate the NLRP3 inflammasome. Identification of the C5a receptor as a key determinant of IL-1-mediated recruitment of inflammatory cells provides a novel potential target for therapeutic intervention to mitigate gouty arthritis.
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Despite a long history and extensive usage of insoluble aluminum salts (alum) as vaccine adjuvants, the molecular mechanisms underpinning Ag-specific immunity upon vaccination remain unclear. Dendritic cells (DCs) are crucial initiators of immune responses, but little is known about the molecular pathways used by DCs to sense alum and, in turn, activate T and B cells. In this article, we show that alum adjuvanticity requires IL-2 specifically released by DCs, even when T cell secretion of IL-2 is intact. We demonstrate that alum, as well as other sterile particulates, such as uric acid crystals, induces DCs to produce IL-2 following initiation of actin-mediated phagocytosis that leads to Src and Syk kinase activation, Ca2+ mobilization, and calcineurin-dependent activation of NFAT, the master transcription factor regulating IL-2 expression. Using chimeric mice, we show that DC-derived IL-2 is required for maximal Ag-specific proliferation of CD4+ T cells and optimal humoral responses following alum-adjuvanted immunization. These data identify DC-derived IL-2 as a key mediator of alum adjuvanticity in vivo and the Src-Syk pathway as a potential leverage point in the rational design of novel adjuvants.
Assuntos
Adjuvantes Imunológicos/farmacologia , Compostos de Alúmen/farmacologia , Células Dendríticas/imunologia , Transdução de Sinais/imunologia , Animais , Linfócitos T CD4-Positivos/imunologia , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Interleucina-2/imunologia , Ativação Linfocitária/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Modelos Animais , Fatores de Transcrição NFATC/imunologia , Transdução de Sinais/efeitos dos fármacos , Quinase Syk/imunologiaRESUMO
The Blomia tropicalis dust mite is prevalent in tropical and subtropical regions of the world. Although it is a leading cause of asthma, little is known how it induces allergy. Using a novel murine asthma model induced by intranasal exposure to B. tropicalis, we observed that a single intranasal sensitization to B. tropicalis extract induces strong Th2 priming in the lung draining lymph node. Resident CD11b(+) dendritic cells (DCs) preferentially transport Ag from the lung to the draining lymph node and are crucial for the initiation of Th2 CD4(+) T cell responses. As a consequence, mice selectively deficient in CD11b(+) DCs exhibited attenuated Th2 responses and more importantly did not develop any allergic inflammation. Conversely, mice deficient in CD103(+) DCs and CCR2-dependent monocyte-derived DCs exhibited similar allergic inflammation compared with their wild-type counterparts. We also show that CD11b(+) DCs constitutively express higher levels of GM-CSF receptor compared with CD103(+) DCs and are thus selectively licensed by lung epithelial-derived GM-CSF to induce Th2 immunity. Taken together, our study identifies GM-CSF-licensed CD11b(+) lung DCs as a key component for induction of Th2 responses and represents a potential target for therapeutic intervention in allergy.
Assuntos
Células Dendríticas/imunologia , Fator Estimulador de Colônias de Granulócitos e Macrófagos/imunologia , Pulmão/imunologia , Ácaros/imunologia , Células Th2/imunologia , Administração Intranasal , Transferência Adotiva , Animais , Asma/imunologia , Asma/metabolismo , Antígeno CD11b/imunologia , Antígeno CD11b/metabolismo , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD4-Positivos/transplante , Células Dendríticas/metabolismo , Células Dendríticas/transplante , Feminino , Citometria de Fluxo , Fator Estimulador de Colônias de Granulócitos e Macrófagos/metabolismo , Imunização/métodos , Interleucina-4/imunologia , Interleucina-4/metabolismo , Pulmão/metabolismo , Pulmão/patologia , Masculino , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Ácaros/metabolismo , Ovalbumina/imunologia , Células Th2/metabolismo , Extratos de Tecidos/administração & dosagem , Extratos de Tecidos/imunologiaRESUMO
The pro-inflammatory cytokine interleukin (IL)-1ß is a clinical target in many conditions involving dysregulation of the immune system; therapeutics that block IL-1ß have been approved to treat diseases such as rheumatoid arthritis (RA), neonatal onset multisystem inflammatory diseases, cryopyrin-associated periodic syndromes, active systemic juvenile idiopathic arthritis. Here, we report the generation and engineering of a new fully human antibody that binds tightly to IL-1ß with a neutralization potency more than 10 times higher than that of the marketed antibody canakinumab. After affinity maturation, the derived antibody shows a>30-fold increased affinity to human IL-1ß compared with its parent antibody. This anti-human IL-1ß IgG also cross-reacts with mouse and monkey IL-1ß, hence facilitating preclinical development. In a number of mouse models, this antibody efficiently reduced or abolished signs of disease associated with IL-1ß pathology. Due to its high affinity for the cytokine and its potency both in vitro and in vivo, we propose that this novel fully human anti-IL-1ß monoclonal antibody is a promising therapeutic candidate and a potential alternative to the current therapeutic arsenal.
Assuntos
Anticorpos Monoclonais/imunologia , Anticorpos Neutralizantes/imunologia , Interleucina-1beta/antagonistas & inibidores , Interleucina-1beta/imunologia , Animais , Anticorpos Monoclonais/genética , Anticorpos Monoclonais/uso terapêutico , Anticorpos Monoclonais Humanizados , Anticorpos Neutralizantes/genética , Anticorpos Neutralizantes/uso terapêutico , Afinidade de Anticorpos , Artrite Experimental/imunologia , Artrite Experimental/terapia , Reações Cruzadas , Modelos Animais de Doenças , Epitopos/imunologia , Feminino , Humanos , Imunoglobulina G/genética , Imunoglobulina G/imunologia , Imunoglobulina G/uso terapêutico , Inflamação/imunologia , Inflamação/terapia , Macaca mulatta , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos NOD , Camundongos SCID , Mieloma Múltiplo/imunologia , Mieloma Múltiplo/terapia , Biblioteca de Peptídeos , Peritonite/imunologia , Peritonite/terapia , Engenharia de ProteínasRESUMO
The factors that regulate the contraction of the CD8 T cell response and the magnitude of the memory cell population against localized mucosal infections such as influenza are important for generation of efficient vaccines but are currently undefined. In this study, we used a mouse model of influenza to demonstrate that the absence of gamma interferon (IFN-γ) or IFN-γ receptor 1 (IFN-γR1) leads to aberrant contraction of antigen-specific CD8 T cell responses. The increased accumulation of the effector CD8 T cell population was independent of viral load. Reduced contraction was associated with an increased fraction of CD8 T cells expressing the interleukin-7 receptor (IL-7R) at the peak of the response, resulting in enhanced numbers of memory/memory precursor cells in IFN-γ(-/-) and IFN-γR(-/-) compared to wild-type (WT) mice. Blockade of IL-7 within the lungs of IFN-γ(-/-) mice restored the contraction of influenza virus-specific CD8 T cells, indicating that IL-7R is important for survival and is not simply a consequence of the lack of IFN-γ signaling. Finally, enhanced CD8 T cell recall responses and accelerated viral clearance were observed in the IFN-γ(-/-) and IFN-γR(-/-) mice after rechallenge with a heterologous strain of influenza virus, confirming that higher frequencies of memory precursors are formed in the absence of IFN-γ signaling. In summary, we have identified IFN-γ as an important regulator of localized viral immunity that promotes the contraction of antigen-specific CD8 T cells and inhibits memory precursor formation, thereby limiting the size of the memory cell population after an influenza virus infection.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Memória Imunológica , Vírus da Influenza A/imunologia , Influenza Humana/imunologia , Interferon gama/imunologia , Animais , Linfócitos T CD8-Positivos/citologia , Feminino , Humanos , Vírus da Influenza A/genética , Influenza Humana/genética , Influenza Humana/virologia , Interferon gama/deficiência , Interferon gama/genética , Contagem de Linfócitos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores de Interferon/deficiência , Receptores de Interferon/genética , Receptores de Interferon/imunologia , Receptores de Interleucina-7/genética , Receptores de Interleucina-7/imunologia , Especificidade da Espécie , Receptor de Interferon gamaRESUMO
Mouse and human dendritic cells (DCs) are composed of functionally specialized subsets, but precise interspecies correlation is currently incomplete. Here, we showed that murine lung and gut lamina propria CD11b+ DC populations were comprised of two subsets: FLT3- and IRF4-dependent CD24(+)CD64(-) DCs and contaminating CSF-1R-dependent CD24(-)CD64(+) macrophages. Functionally, loss of CD24(+)CD11b(+) DCs abrogated CD4+ T cell-mediated interleukin-17 (IL-17) production in steady state and after Aspergillus fumigatus challenge. Human CD1c+ DCs, the equivalent of murine CD24(+)CD11b(+) DCs, also expressed IRF4, secreted IL-23, and promoted T helper 17 cell responses. Our data revealed heterogeneity in the mouse CD11b+ DC compartment and identifed mucosal tissues IRF4-expressing DCs specialized in instructing IL-17 responses in both mouse and human. The demonstration of mouse and human DC subsets specialized in driving IL-17 responses highlights the conservation of key immune functions across species and will facilitate the translation of mouse in vivo findings to advance DC-based clinical therapies.
Assuntos
Aspergillus fumigatus/imunologia , Células Dendríticas/metabolismo , Fatores Reguladores de Interferon/metabolismo , Interleucina-17/metabolismo , Células Th17/metabolismo , Animais , Antígeno CD11b/metabolismo , Antígeno CD24/metabolismo , Diferenciação Celular/imunologia , Células Dendríticas/imunologia , Humanos , Interleucina-17/biossíntese , Interleucina-23/metabolismo , Mucosa Intestinal/citologia , Mucosa Intestinal/imunologia , Macrófagos/metabolismo , Camundongos , Receptores de IgG/metabolismo , Mucosa Respiratória/citologia , Mucosa Respiratória/imunologia , Tirosina Quinase 3 Semelhante a fms/metabolismoRESUMO
Trafficking of lung dendritic cells (DCs) to the draining lymph node (dLN) is a crucial step for the initiation of T cell responses upon pathogen challenge. However, little is known about the factors that regulate lung DC migration to the dLN. In this study, using a model of influenza infection, we demonstrate that complement component C3 is critically required for efficient emigration of DCs from the lung to the dLN. C3 deficiency affect lung DC-mediated viral antigen transport to the dLN, resulting in severely compromised priming of virus-specific T cell responses. Consequently, C3-deficient mice lack effector T cell response in the lungs that affected viral clearance and survival. We further show that direct signaling by C3a and C5a through C3aR and C5aR respectively expressed on lung DCs is required for their efficient trafficking. However, among lung DCs, only CD103(+) DCs make a significant contribution to lung C5a levels and exclusively produce high levels of C3 and C5 during influenza infection. Collectively, our findings show that complement has a profound impact on immune regulation by controlling tissue DC trafficking and highlights a potential utility for complement as an adjuvant in novel vaccine strategies.
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Antígenos CD/metabolismo , Complemento C3/metabolismo , Complemento C5a/metabolismo , Células Dendríticas/metabolismo , Cadeias alfa de Integrinas/metabolismo , Pulmão/metabolismo , Infecções por Orthomyxoviridae/metabolismo , Animais , Antígenos Virais , Movimento Celular , Complemento C3/deficiência , Células Dendríticas/virologia , Pulmão/virologia , Camundongos , Camundongos Knockout , Infecções por Orthomyxoviridae/mortalidade , Infecções por Orthomyxoviridae/virologia , Receptor da Anafilatoxina C5a/metabolismo , Receptores de Complemento/metabolismo , Transdução de Sinais , Taxa de Sobrevida , Linfócitos T/metabolismo , Carga Viral , VírusRESUMO
An effective immune response against influenza A infection depends on the generation of virus-specific T cells. NK cells are one of the first-line defenses against influenza A infection. We set out to delineate the role of NK cells in T cell immunity using a murine model of influenza A infection with A/PR/8/34. We show that early T cell recruitment mainly occurs in the posterior mediastinal lymph node (pMLN). Depletion of NK cells significantly impaired both dendritic cell (DC) and T cell recruitment into the pMLN. A similar reduction of T cell recruitment was observed when migration was blocked by pertussis toxin, suggesting that migration of pulmonary NK cells and DCs regulates cell recruitment to the pMLN. T cell recruitment was dependent on IFN-γ, and transfer of IFN-γ-competent naive NK cells into IFN-γ-/- mice restored T cell recruitment, whereas IFN-γ-deficient NK cells failed to do so. In addition, NK cell depletion reduced the uptake and transport of influenza A virus by DCs, and significantly impaired the virus-specific T cell response. Both IFN-γ-/- and perforin-/- mice showed reduced viral Ag transport by DCs, suggesting that the ability of NK cells to influence virus transport depends on IFN-γ and perforin. In summary, our data suggest that NK cells play a critical role in the initiation and shaping of the T cell response after influenza A infection.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Movimento Celular/imunologia , Células Dendríticas/imunologia , Interferon gama/fisiologia , Células Matadoras Naturais/imunologia , Infecções por Orthomyxoviridae/imunologia , Proteínas Citotóxicas Formadoras de Poros/fisiologia , Animais , Apoptose/imunologia , Linfócitos T CD8-Positivos/virologia , Linhagem Celular , Linhagem Celular Tumoral , Células Dendríticas/patologia , Células Dendríticas/virologia , Humanos , Vírus da Influenza A Subtipo H1N1/imunologia , Células Matadoras Naturais/virologia , Linfonodos/imunologia , Linfonodos/patologia , Linfonodos/virologia , Ativação Linfocitária/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Infecções por Orthomyxoviridae/patologia , Infecções por Orthomyxoviridae/virologiaRESUMO
BACKGROUND: Previous studies have shown that CD8 T cells can both prevent and cause allergic responses. However, the underlying mechanisms remain to be elucidated. OBJECTIVE: We aim to investigate the potential of CD8 T cells with different IFN-γ expressions to modulate the elicitation of allergic inflammation following ovalbumin (OVA) challenge and investigate the underlying mechanisms. METHODS: To study the role of IFN-γ in the effect of CD8 T cells, effector CD8 T cells from CD8 OVA transgenic (OT-I) mice and IFN-γ(-/-)OT-I mice were transferred to OVA-sensitized mice the day before 3 challenges with OVA. The effect on lung dendritic cells (DCs) exerted by CD8 T cells was studied with ex vivo culture of sorted DCs from treatment mice with CD4 T cells. RESULTS: Effector OT-I, but not IFN-γ(-/-)OT-I CD8 T cells, attenuated eosinophilia and mucus secretion in the lungs of sensitized mice in an antigen-specific manner. Effector IFN-γ(-/-)OT-I CD8 T cells displayed a Tc2-/Tc17-biased phenotype with weaker cytotoxicity and were able to both induce and exacerbate eosinophilia as well as neutrophilia. OT-I CD8 T cells increased the ability of lung CD11b(+)CD103(-) DCs to both prime the differentiation of naive OVA-specific CD4 T cells toward a T(H)1 phenotype and enhance IFN-γ production by antigen-experienced lung CD4 T cells. CONCLUSION: Effector CD8 T cells attenuate pulmonary inflammation and alter the ability of DCs within the allergic lung to polarize T cells to a T(H)1 phenotype during a T(H)2 response. In the absence of IFN-γ, CD8 T cells assume a Tc2-/Tc17-biased phenotype and potentiate inflammation.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Células Dendríticas/imunologia , Hipersensibilidade/imunologia , Interferon gama/metabolismo , Animais , Linfócitos T CD8-Positivos/metabolismo , Diferenciação Celular/imunologia , Feminino , Expressão Gênica , Células Caliciformes/metabolismo , Hipersensibilidade/genética , Hipersensibilidade/patologia , Imunofenotipagem , Interferon gama/genética , Pulmão/imunologia , Pulmão/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Muco , Fenótipo , Células Th1/citologiaRESUMO
Foxp3(+) CD4(+) regulatory T cells (Tregs) represent a highly suppressive T cell subset with well-characterized immunosuppressive effects during immune homeostasis and chronic infections, although the role of these cells in acute viral infections is poorly understood. The present study sought to examine the induction of Foxp3(+) CD4(+) Tregs in a nonlethal murine model of pulmonary viral infection by the use of the prototypical respiratory virus influenza A. We establish that influenza A virus infection results in a robust Foxp3(+) CD4(+) T cell response and that regulatory T cell induction at the site of inflammation precedes the effector T cell response. Induced Foxp3(+) CD4(+) T cells are highly suppressive ex vivo, demonstrating that influenza virus-induced Foxp3(+) CD4(+) T cells are phenotypically regulatory. Influenza A virus-induced regulatory T cells proliferate vigorously in response to influenza virus antigen, are disseminated throughout the site of infection and primary and secondary lymphoid organs, and retain Foxp3 expression in vitro, suggesting that acute viral infection is capable of inducing a foreign-antigen-specific Treg response. The ability of influenza virus-induced regulatory T cells to suppress antigen-specific CD4(+) and CD8(+) T cell proliferation and cytokine production correlates closely to their ability to respond to influenza virus antigens, suggesting that virus-induced Tregs are capable of attenuating effector responses in an antigen-dependent manner. Collectively, these data demonstrate that primary acute viral infection is capable of inducing a robust, antigen-responsive, and suppressive regulatory T cell response.
Assuntos
Antígenos Virais/imunologia , Fatores de Transcrição Forkhead/imunologia , Vírus da Influenza A Subtipo H1N1/fisiologia , Influenza Humana/imunologia , Linfócitos T Reguladores/imunologia , Animais , Feminino , Fatores de Transcrição Forkhead/genética , Humanos , Vírus da Influenza A Subtipo H1N1/imunologia , Influenza Humana/genética , Influenza Humana/virologia , Masculino , Camundongos , Camundongos Endogâmicos C57BLRESUMO
The uptake, transport, and presentation of Ags by lung dendritic cells (DCs) are central to the initiation of CD8 T cell responses against respiratory viruses. Although several studies have demonstrated a critical role of CD11b(low/neg)CD103(+) DCs for the initiation of cytotoxic T cell responses against the influenza virus, the underlying mechanisms for its potent ability to prime CD8 T cells remain poorly understood. Using a novel approach of fluorescent lipophilic dye-labeled influenza virus, we demonstrate that CD11b(low/neg)CD103(+) DCs are the dominant lung DC population transporting influenza virus to the posterior mediastinal lymph node as early as 20 h postinfection. By contrast, CD11b(high)CD103(neg) DCs, although more efficient for taking up the virus within the lung, migrate poorly to the lymph node and remain in the lung to produce proinflammatory cytokines instead. CD11b(low/neg)CD103(+) DCs efficiently load viral peptide onto MHC class I complexes and therefore uniquely possess the capacity to potently induce proliferation of naive CD8 T cells. In addition, the peptide transporters TAP1 and TAP2 are constitutively expressed at higher levels in CD11b(low/neg)CD103(+) DCs, providing, to our knowledge, the first evidence of a distinct regulation of the Ag-processing pathway in these cells. Collectively, these results show that CD11b(low/neg)CD103(+) DCs are functionally specialized for the transport of Ag from the lung to the lymph node and also for efficient processing and presentation of viral Ags to CD8 T cells.
Assuntos
Apresentação de Antígeno/imunologia , Linfócitos T CD8-Positivos/imunologia , Células Dendríticas/imunologia , Linfonodos/imunologia , Ativação Linfocitária/imunologia , Infecções por Orthomyxoviridae/imunologia , Animais , Antígenos CD/imunologia , Antígenos Virais/imunologia , Separação Celular , Células Dendríticas/virologia , Citometria de Fluxo , Antígenos de Histocompatibilidade Classe I/imunologia , Cadeias alfa de Integrinas/imunologia , Pulmão/imunologia , Linfonodos/virologia , Camundongos , Camundongos Endogâmicos C57BL , Orthomyxoviridae/imunologia , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Foxp3âºCD4⺠regulatory T cells represent a T cell subset with well-characterized immunosuppressive effects during immune homeostasis and chronic infections, and there is emerging evidence to suggest these cells temper pulmonary inflammation in response to acute viral infection. Recent studies have demonstrated treatment with PC61 CD25-depleting antibody potentiates inflammation in a murine model of RSV infection, while paradoxically delaying recruitment of CD8⺠T cells to the site of inflammation. The present study therefore sought to examine the role of these cells in a murine model of acute influenza A virus infection through the administration of PC61 CD25-depleting antibody. PC61 antibody is able to partially deplete CD25âºFoxp3⺠regulatory T cells to a comparable degree as seen within previous work examining RSV, however this does not alter influenza A-virus induced mortality, weight loss, viral clearance and cellularity within the lung. Collectively, these data demonstrate that partial depletion of CD4âºCD25⺠regulatory T cells with PC61 antibody does not alter the course of influenza A virus infection.