Defense against HSV-1 in a murine model is mediated by iNOS and orchestrated by the activation of TLR2 and TLR9 in trigeminal ganglia.
BACKGROUND
Herpes simplex 1 (HSV-1) causes various human clinical manifestations, ranging from simple cold sores to encephalitis. Innate immune cells recognize pathogens through Toll-like receptors (TLRs), thus initiating the immune response. Previously, we demonstrated that the immune response against HSV-1 is dependent on TLR2 and TLR9 expression and on IFN gamma production in the trigeminal ganglia (TG) of infected mice. In this work, we further investigated the cells, molecules, and mechanisms of HSV-1 infection control, especially those that are TLR-dependent.


METHODS
C57BL/6 wild-type (WT), TLR2-/-, TLR9-/-, and TLR2/9-/- mice were intranasally infected with HSV-1. On the viral peak day, the TG and brains were collected from mice and TLR expression was measured in the TG and brain and inducible nitric oxide synthase (iNOS) expression was measured in the TG by real-time PCR. Immunofluorescence assays were performed in mice TG to detect iNOS production by F4/80+ cells. Intraperitoneal macrophages nitric oxide (NO) production was evaluated by the Griess assay. WT, CD8-/-, RAG-/-, and iNOS-/- mice were intranasally infected in a survival assay, and their cytokine expression was measured in the TG by real-time PCR.


RESULTS
Infected WT mice exhibited significantly increased TLR expression, compared with their respective controls, in the TG but not in the brain. TLR-deficient mice had moderately increased TLR expression in the TG and brain in compare with the non-infected animals. iNOS expression in the WT infected mice TG was higher than in the other groups with increased production by macrophages in the WT infected mice, which did not occur in the TLR2/9-/- mice. Additionally, the intraperitoneal macrophages of the WT mice had a higher production of NO compared with those of the TLR-deficient mice. The CD8-/-, RAG-/-, and iNOS-/- mice had 100% mortality after the HSV-1 infection compared with 10% of the WT mice. Cytokines were overexpressed in the iNOS-/- infected mice, while the RAG-/- mice were nearly unresponsive to the virus.


CONCLUSIONS
TLRs efficiently orchestrate the innate immune cells, eliciting macrophage response (with NO production by the macrophages), thereby controlling the HSV-1 infection through the immune response in the TG of mice.
Guilherme Pimenta
GP
Zolini
Graciela Kunrath
GK
Lima
Natália
N
Lucinda
Mariana Almeida
MA
Silva
Marcela França
MF
Dias
Natália Lima
NL
Pessoa
Bruna Pizziolo
BP
Coura
Christiane Teixeira
CT
Cartelle
Rosa Maria Esteves
RM
Arantes
Erna Geessien
EG
Kroon
Laboratório de Imunopatologia, Imunologia de Doenças Virais, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Fiocruz, Av, Augusto de Lima 1715, Belo Horizonte, Minas Gerais 30190-002, Brazil. marcoasc@cpqrr.fiocruz.br.
Marco Antônio
MA
Campos
D000818:Animals; D001921:Brain / Q000378:metabolism / Q000473:pathology / Q000821:virology; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D006512:Hepatitis B Core Antigens / Q000378:metabolism; D006561:Herpes Simplex / Q000473:pathology*; D018259:Herpesvirus 1, Human / Q000502:physiology*; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000821:virology; D008264:Macrophages / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011971:Receptors, Immunologic / Q000378:metabolism; D013864:Thioglycolates / Q000627:therapeutic use; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism*; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism*; D012668:Trigeminal Ganglion / Q000378:metabolism*; D014758:Viral Core Proteins / Q000378:metabolism
D016207:Cytokines; D006512:Hepatitis B Core Antigens; C105949:Pirb protein, mouse; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D013864:Thioglycolates; C493486:Tlr2 protein, mouse; C495370:Tlr9 protein, mouse; D051195:Toll-Like Receptor 2; D051217:Toll-Like Receptor 9; D014758:Viral Core Proteins; C534392:p22 core protein, hepatitis B virus; D052247:Nitric Oxide Synthase Type II