Viral infection and immune response in early life and the influences of maternal immunityBlomqvist, Gunilla
Limited capacity in early life to defeat viral infections is initially compensated by the transmission of maternal immunity. Establishing the point in time at which the number of maternal antibodies have decreased to a nonprotective level is critical since the immune system of the progeny only gradually attains its capacity for a functional immune defense. In our search for means to provide immune protection during this period, we have to take into consideration factors such as the maternal influences including antibodies and the immaturity ofthe offspring’s immune system.
In the first part ofthis thesis, the importance ofmaternal immunity was assessed in breeding herds suffering from enzootic viral infections. In one herd infected with mouse hepatitis virus (MHV), the consequences of the lack of maternal antibodies were demonstrated. Mice nursed by immunoglobulin (Ig)-deficient dams showed growth retardation and high mortality, and polymerase chain reaction (PCR) revealed MHV nucleic acid in lung cells. No signs of a viral infection were seen in Ig-deficient mice nursed by immune dams. In the second breeding herd, the transmission pattern and kinetics of a parainfluenza type 3 virus (PIV 3) infection were mapped in guinea pig offspring. The knowledge gained in this study provides essential information for the design of an eradication model based on controlled breeding.
Immunization by infection or vaccination during the neonatal period is generally dominated by a T helper 2 (Th2) response and a T helper 1 (Thl) deficiency, with an impaired capacity to defeat viral infections as a consequence. In the second part of this thesis, the conditions for a functionally balanced immune response were explored in an experimental BALB/c mouse model. Sendai virus (SV) envelope proteins in three formulas differing in terms of their adjuvant activity were used. It was shown that the Thl-adjuvanted SV immunostimulating complex (ISCOM) has the ability to prime neonatal mice for a Thl memory effector function and that neonatal immunization to a large extent influences postnatal immunity. Importantly, later immunizations with antigen supplemented with a potent adjuvant can modify a neonatally polarized immune response. It was also shown that it is possible to prime for a Thl type ofimmunity in early life despite the presence of maternal antibodies. It is noteworthy that the Thl/Th2 balance in the dams influenced the postnatal development ofimmune response in their offspring.
Keywordsmouse hepatitis virus (MHV); parainfluenza type 3 virus (PIV 3); Sendai virus maternal immunity; neonatal immunization; immunomodulation, Thl/Th2; adjuvants
Published inActa Universitatis Agriculturae Sueciae. Veterinaria
2002, number: 124
Publisher: Swedish University of Agricultural Sciences
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