Respiratory syncytial virus infection and G and/or SH protein expression contribute to substance P, which mediates inflammation and enhanced pulmonary disease in BALB/c mice

Abstract

A distinct clinical presentation of respiratory syncytial virus (RSV) infection of humans is bronchiolitis, which has clinical features similar to those of asthma. Substance P (SP), a tachykinin neuropeptide, has been associated with neurogenic inflammation and asthma; therefore, we chose to examine SP-induced inflammation with RSV infection. In this study, we examined the production of pulmonary SP associated with RSV infection of BALB/c mice and the effect of anti-SP F(ab)(2) antibodies on the pulmonary inflammatory response. The peak production of pulmonary SP occurred between days 3 and 5 following primary RSV infection and day 1 after secondary infection. Treatment of RSV-infected mice with anti-SP F(ab)(2) antibodies suggested that SP may alter the natural killer cell response to primary and secondary infection. In mice challenged after formalin-inactivated RSV vaccination, SP appears to markedly enhance pulmonary eosinophilia as well as increase polymorphonuclear cell trafficking to the lung. Based on studies with a strain of RSV that lacks the G and SH genes, the SP response to RSV infection appears to be associated with G and/or SH protein expression. These data suggest that SP may be an important contributor to the inflammatory response to RSV infection and that anti-SP F(ab)(2) antibodies might be used to ameliorate RSV-associated disease.

FIG. 1

SP-induced cell proliferation or inhibition of SP-induced cell proliferation by in vitro addition of anti-SP F(ab)₂ Ab. (A) Intact spleen cells and CD4⁺- or CD8⁺-enriched RSV-immune T cells were cocultured with TCM, CA, or various doses of SP. The proliferation values are given as a stimulation index determined by dividing the mean experimental proliferation value by the mean of the TCM control proliferation value. (B) Intact spleen cells and CD4⁺- or CD8⁺-enriched RSV-immune T cells were cocultured with TCM, CA, or various doses of SP and anti-SP F(ab)₂ Ab. The proliferation values are given as a stimulation index determined by dividing the mean experimental proliferation value by the mean of the TCM control proliferation value. The addition of either a 1:10 dilution of anti-SP F(ab)₂ or nIg F(ab)₂ Ab to CA-stimulated cultures did not affect the stimulation index (data not shown).

FIG. 2

Effect of PBS, nIg F(ab)₂ Ab, or various doses of anti-SP F(ab)₂ Ab on the total cell number in the lungs of mice following acute RSV B1 infection.

FIG. 3

In vivo anti-SP Ab treatment suppresses IC cytokine expression by CD3⁺ T lymphocytes. (A) Mice were treated day 5 after RSV infection with doses of anti-SP F(ab)₂ Ab or nIg F(ab)₂ Ab; the BAL cells were recovered 18 h posttreatment and analyzed for IC cytokine expression. (B) Mice were treated day 5 after RSV infection with doses of anti-SP F(ab)₂ Ab or nIg F(ab)₂ Ab; the BAL cells were recovered 36 h posttreatment and analyzed for IC cytokine expression.