Abstract
Previous work by Michaels, Myerowitz and Klaw (J.Infect. Dis. in press) showed that the intranasal dose of H. influenzae type b (HIB) required to produce bacteremia and meningitis in about 50% of infant rats was reduced 100-fold when animals were first given influenza A virus (Port Chalmers strain). Similar results have recently been obtained with A/England and A/Victoria viruses.
As a part of a study of virus attenuation, 2 day old rats were given 105-107 egg infective doses (EID) of either A/Victoria (A/V) or B/Hong Kong (B/HK) viruses intranasally. At 5 days of age all rats were given 105-106 colony forming units (cfu) of HIB intranasally. HIB bacteremia was found at 7 days of age in 52/97 rats given A/V virus, but in only 3/49 rats given B/HK virus. Bacteremia was detected in none of 38 control rats.
In a single experiment, 2 day old rats were given almost identical doses of virus (105.6 EID of A/V or 105.7 EID of B/HK), but the virus titer in nasal turbinates 48 hours later was over 100 times higher for A/V than for B/HK virus. At 5 days of age rats were given 106 cfu of HIB. Subsequent bacteremia was detected in 4/9 rats given A/V and in none of 11 rats given B/HK.
The lower turbinate virus titers and lack of potentiation of HIB infection in rats with influenza B as compared to influenza A virus is consistent with epidemiologic observations suggesting that influenza B is often a mild disease in humans.
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Michaels, R., Myerowitz, R. & Ruben, F. DIFFERENCE IN BEHAVIOR OF INFLUENZA A AND B VIRUSES IN INFANT RATS: VIRAL MULTIPLICATION IN NASAL TURBINATES AND POTENTIATION OF BACTEREMIC INFECTION WITH H. INFLU-ENZAE TYPE B. Pediatr Res 11, 503 (1977). https://doi.org/10.1203/00006450-197704000-00799
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DOI: https://doi.org/10.1203/00006450-197704000-00799