THE JOURNAL OF INFECTIOUS DISEASES. VOL. 140, NO.1. JULY 1979 © 1979 by The University of Chicago. 0022-1899179/4001-0013$00.75
NOTES Pulmonary and Systemic Defenses against Challenge with Staphylococcus aureus in Mice with Pneumonia Due to Influenza A Virus From the Department of Environmental Health Sciences, The Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland
George J. Jakab, Glenn A. Warr, and Marde1 E. Knight
Clinical, epidemiologic, and experimental studies have demonstrated that viral infections, particularly influenza virus infections, predispose the lung to bacterial pneumonia [1, 2]. Investigations with animal models of viral-bacterial interactions in the lung have focused on pulmonary defense mechanisms during viral pneumonitis against airborne bacterial infections [2-4]. Although it has been well documented that viral infections suppress the phagocytic defenses of the lung against airborne bacterial challenges, it is not yet known whether viral pneumonitis also predisposes individuals to pulmonary and systemic bacterial infection from blood-borne organisms. That influenza virus infection may alter systemic host defenses has been suggested by studies showing that motility of peripheral mon-
ocytes and neutrophils was depressed during influenza virus infection [5-9]. In the studies presented here, we have measured microbicidal activity in the lung and the major reticuloendothelial organs (the spleen and the liver) of mice after hematogenous challenge with Staphylococcus aureus during pneumonitis due to influenza A virus. Materials and Methods
Animals. Swiss white mice (Microbiologic Associates, Walkersville, Md.) weighing 20-23 g were used throughout these studies. Viral infection. The PR-8 strain of influenza A virus, adapted in mice, was harvested from the allantoic fluid of 13-day-old chick embryos after incubation at 37 C for two days, titrated in cultures of rhesus monkey tissue, and stored in small portions at -70 C. The titer of the stock culture of virus was 108 TClD50 / m l. Mice were exposed to a I :50 dilution of this stock-culture virus for 30 min in an infectious exposure chamber descri bed previously [10]. Bacterial challenge. S. aureus organisms (coagulase-positive strain 209P, phage type 42D) were labeled with 32p by methods described previously [11]. Animals were challenged with the bacteria either by injection into the lateral tail
Received for publication October 19, 1978, and in revised form December 26,1978. This work was supported by research grant no. HL 22029 from the National Heart, Lung, and Blood Institute. Drs. Jakab and Warr are the recipients, respectively, of Research Career Development Award no. HL 00415 and Young Investigator Award no. HL 22823 from the National Heart, Lung, and Blood Institute. Please address requests for reprints to Dr. George J. Jakab, Department of Environmental Health Sciences, The Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205.
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Pulmonary and systemic defenses against hematogenous challenge with 32P-Iabeled Staphylococcus aureus were measured 10 min, 8 hr, and 24 hr after intravenous injection of the bacteria in a mouse model of influenza virus pneumonia. Infection with influenza A virus did not alter bactericidal defenses in the liver and spleen, but pulmonary bactericidal activity measured 24 hr after infection was suppressed in virus-infected animals; 20% ± 3% of the initially injected, viable bacteria were recovered from lungs of pneumonitic mice after 24 hr as compared with 9% ± I % from lungs of the un infected mice. These data demonstrate that pulmonary infection with influenza virus does not alter antibacterial defenses of the liver and spleen but does suppress bactericidal activity in the lung.
Jakab, Warr, and Knight
106
=
bacteria at 10 min /cpm at 10 min)] [(ratio at 8hror24hr/ratioat 10min) X 100]. The percentages of bacteria remaining in the lungs of mice challenged with an aerosol of S. aureus were calculated in a similar manner. Results
The lungs of all mice infected with influenza A virus had lesions indicative of severe viral pneumonitis seven days after infection. In general, surface consolidation involved 25% of the entire lung. The defenses of the lung against subsequent challenge with airborne S. aureus were clearly suppressed. At 8 hr and 24 hr, the mean (± SE) percentages of the initially viable bacteria remaining in the lungs of pneumonitic mice were 77% ± 6% and 82CJ'o ± 17%, respectively, in contrast to the rapid decline in the lungs of uninfected animals to 5CJ'o ± 3% and 0.45% ± 0.01 %' respectively. The distribution of 32P-labeled S. aureus recovered from the lungs, spleens, and livers of virus-infected and uninfected mice 10 min, 8 hr, and 24 hr after iv challenge is shown in table 1. At the later times, most of the hematogenously Table 1. Percentage distribution of radioactivity in the lungs, spleens, and livers of influenza A virus-infected and uninfected mice after iv injection of 32P-Iabeled Staphylococcus aureus.
Organ, group of mice Lung Uninfected Virus-infected Spleen Uninfected Virus-infected Liver Uninfected Virus-infected
Value at indicated time after injection
10 min
8 hr
24 hr
7.2±1.2 9.4 ± 1.7
1.3 ± 0.2* 3.2 ± 0.3*
0.8 ± 0.1* 2.U ± 0.3*
9.4 ± 0.9 7.8 ± 0.6
9.1 ± 1.2 8.4 ± 0.8
8.8 ± 0.5 9.0 ± 0.5
83.4 ± 1.1 82.8 ± 2.1
89.6 ± 0.9 88.4 ± 1.3
90.4 ± 1.3 89.0 ± 1.0
NOTE. Each value represents the percentag-e of the initial radioactivity recovered from all three org-ans and is the mean ± SE of 10- 12 individual determinations. See Materials and Methods for the viral infection, bacterial challeng-e, and radioassay procedures. "Difference between uninfecred and virus-infected g-roups at this interval was statistically sig-nificant (P
NOTES Pulmonary and Systemic Defenses against Challenge with Staphylococcus aureus in Mice with Pneumonia Due to Influenza A Virus From the Department of Environmental Health Sciences, The Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland
George J. Jakab, Glenn A. Warr, and Marde1 E. Knight
Clinical, epidemiologic, and experimental studies have demonstrated that viral infections, particularly influenza virus infections, predispose the lung to bacterial pneumonia [1, 2]. Investigations with animal models of viral-bacterial interactions in the lung have focused on pulmonary defense mechanisms during viral pneumonitis against airborne bacterial infections [2-4]. Although it has been well documented that viral infections suppress the phagocytic defenses of the lung against airborne bacterial challenges, it is not yet known whether viral pneumonitis also predisposes individuals to pulmonary and systemic bacterial infection from blood-borne organisms. That influenza virus infection may alter systemic host defenses has been suggested by studies showing that motility of peripheral mon-
ocytes and neutrophils was depressed during influenza virus infection [5-9]. In the studies presented here, we have measured microbicidal activity in the lung and the major reticuloendothelial organs (the spleen and the liver) of mice after hematogenous challenge with Staphylococcus aureus during pneumonitis due to influenza A virus. Materials and Methods
Animals. Swiss white mice (Microbiologic Associates, Walkersville, Md.) weighing 20-23 g were used throughout these studies. Viral infection. The PR-8 strain of influenza A virus, adapted in mice, was harvested from the allantoic fluid of 13-day-old chick embryos after incubation at 37 C for two days, titrated in cultures of rhesus monkey tissue, and stored in small portions at -70 C. The titer of the stock culture of virus was 108 TClD50 / m l. Mice were exposed to a I :50 dilution of this stock-culture virus for 30 min in an infectious exposure chamber descri bed previously [10]. Bacterial challenge. S. aureus organisms (coagulase-positive strain 209P, phage type 42D) were labeled with 32p by methods described previously [11]. Animals were challenged with the bacteria either by injection into the lateral tail
Received for publication October 19, 1978, and in revised form December 26,1978. This work was supported by research grant no. HL 22029 from the National Heart, Lung, and Blood Institute. Drs. Jakab and Warr are the recipients, respectively, of Research Career Development Award no. HL 00415 and Young Investigator Award no. HL 22823 from the National Heart, Lung, and Blood Institute. Please address requests for reprints to Dr. George J. Jakab, Department of Environmental Health Sciences, The Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205.
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Downloaded from http://jid.oxfordjournals.org/ at Cambridge University on August 27, 2015
Pulmonary and systemic defenses against hematogenous challenge with 32P-Iabeled Staphylococcus aureus were measured 10 min, 8 hr, and 24 hr after intravenous injection of the bacteria in a mouse model of influenza virus pneumonia. Infection with influenza A virus did not alter bactericidal defenses in the liver and spleen, but pulmonary bactericidal activity measured 24 hr after infection was suppressed in virus-infected animals; 20% ± 3% of the initially injected, viable bacteria were recovered from lungs of pneumonitic mice after 24 hr as compared with 9% ± I % from lungs of the un infected mice. These data demonstrate that pulmonary infection with influenza virus does not alter antibacterial defenses of the liver and spleen but does suppress bactericidal activity in the lung.
Jakab, Warr, and Knight
106
=
bacteria at 10 min /cpm at 10 min)] [(ratio at 8hror24hr/ratioat 10min) X 100]. The percentages of bacteria remaining in the lungs of mice challenged with an aerosol of S. aureus were calculated in a similar manner. Results
The lungs of all mice infected with influenza A virus had lesions indicative of severe viral pneumonitis seven days after infection. In general, surface consolidation involved 25% of the entire lung. The defenses of the lung against subsequent challenge with airborne S. aureus were clearly suppressed. At 8 hr and 24 hr, the mean (± SE) percentages of the initially viable bacteria remaining in the lungs of pneumonitic mice were 77% ± 6% and 82CJ'o ± 17%, respectively, in contrast to the rapid decline in the lungs of uninfected animals to 5CJ'o ± 3% and 0.45% ± 0.01 %' respectively. The distribution of 32P-labeled S. aureus recovered from the lungs, spleens, and livers of virus-infected and uninfected mice 10 min, 8 hr, and 24 hr after iv challenge is shown in table 1. At the later times, most of the hematogenously Table 1. Percentage distribution of radioactivity in the lungs, spleens, and livers of influenza A virus-infected and uninfected mice after iv injection of 32P-Iabeled Staphylococcus aureus.
Organ, group of mice Lung Uninfected Virus-infected Spleen Uninfected Virus-infected Liver Uninfected Virus-infected
Value at indicated time after injection
10 min
8 hr
24 hr
7.2±1.2 9.4 ± 1.7
1.3 ± 0.2* 3.2 ± 0.3*
0.8 ± 0.1* 2.U ± 0.3*
9.4 ± 0.9 7.8 ± 0.6
9.1 ± 1.2 8.4 ± 0.8
8.8 ± 0.5 9.0 ± 0.5
83.4 ± 1.1 82.8 ± 2.1
89.6 ± 0.9 88.4 ± 1.3
90.4 ± 1.3 89.0 ± 1.0
NOTE. Each value represents the percentag-e of the initial radioactivity recovered from all three org-ans and is the mean ± SE of 10- 12 individual determinations. See Materials and Methods for the viral infection, bacterial challeng-e, and radioassay procedures. "Difference between uninfecred and virus-infected g-roups at this interval was statistically sig-nificant (P
