Stimulation of active immunity to Langat virus in the presence of maternal antibody
Seamer, J.; Snape, T.
Veterinary Record 91(16): 383-385
1972
ISSN/ISBN: 0042-4900 PMID: 4635160 Document Number: 46063
Passive immunity to many viruses has been reported in baby mice suckled by immune dams. A small colony of mice was immunized by foot pad (fp) and subsequent intracerebral (i/c) injection of Langat virus. The following three litters from each immune pair were inoculated fp or i/c at about 13, 25 or 42 days of age. Survivors were challenged i/c about 60 days after inoculation. Results are tabulated. Mortality of control mice inoculated at 12, 25, 42 or 99 days of age was 97, 35, 5 or 0% (fp inoculation), or 100, 100, 96 or 97% (i/c inoculation). Almost all survivors were immune to subsequent challenge. Mortality rates of mice from the immune colony inoculated at 13 or 25 days were 2% and 0% (fp inoculation) or 13% and 8% (i/c inoculation). The survival rate at subsequent challenge was greater when initial inoculation was i/c rather than fp, i.e. about 70% and 20%, respectively. Although only 30% survived i/c inoculation at 42 days of age, these were all immune to subsequent challenge. Passive immunity protected against fp inoculation at 13 and 25 days of age, but generally prevented development of active immunity. Passive immunity gave less protection against i/c inoculation (particularly at 42 days of age), but interfered less in development of active immunity. Probably, fp inoculations in passively immune mice are rapidly neutralized, while i/c inoculations are dispersed and are able to set up local reactions in brain as well as in immunocompetent tissues. Passive immunity might be used in domestic stock to provide initial resistance, while active immunity would be induced by appropriately large doses of inoculum.