Maternal influenza infection causes marked behavioral and pharmacological changes in the offspring

Abstract

Maternal viral infection is known to increase the risk for schizophrenia and autism in the offspring. Using this observation in an animal model, we find that respiratory infection of pregnant mice (both BALB/c and C57BL/6 strains) with the human influenza virus yields offspring that display highly abnormal behavioral responses as adults. As in schizophrenia and autism, these offspring display deficits in prepulse inhibition (PPI) in the acoustic startle response. Compared with control mice, the infected mice also display striking responses to the acute administration of antipsychotic (clozapine and chlorpromazine) and psychomimetic (ketamine) drugs. Moreover, these mice are deficient in exploratory behavior in both open-field and novel-object tests, and they are deficient in social interaction. At least some of these behavioral changes likely are attributable to the maternal immune response itself. That is, maternal injection of the synthetic double-stranded RNA polyinosinic-polycytidylic acid causes a PPI deficit in the offspring in the absence of virus. Therefore, maternal viral infection has a profound effect on the behavior of adult offspring, probably via an effect of the maternal immune response on the fetus.

Fig. 1.

The exploratory behavior of mice born to infected mothers is very different from that of mice born to sham-infected mothers. The movements of a typical mouse from each group were traced from a videotape of a 10 min session in an open field subdivided into 25 squares by lines on the bottom of the box. Sites of rearing on hindpaws are illustrated by circles. Although these are not the most extreme examples of the behavior of mice from each group, it is clear that the mouse born to a sham-infected mother (top) responds very differently to the stress of this situation than the mouse born to a virus-infected mother (bottom).

Fig. 2.

Spontaneous activity assayed by photobeam crossing. Individual mice were removed from their home cage and placed in the photobeam apparatus for 40 hr. The number of successive beam crossings (ambulation) was recorded and is expressed per hour. Control mice (n = 8; 4 males) explored this new environment extensively for the first 24 hr period and then settled into a regular activity pattern on the second day. The mice born to infected mothers (n = 10; 5 males) failed to display the early, active exploration pattern seen in the controls, but beginning on the second night, their baseline activity level was not different from the controls. *p < 0.05; **p < 0.01.

Fig. 3.

Exposed and control mice display no differences in the rota-rod test. Mice were tested three times daily for 3 d on a rota-rod in the accelerating mode. The results are expressed as the means of each of the daily test sessions, and we recorded the longest duration that each mouse stayed on the rota-rod. There was no significant difference between control (n = 10) and exposed (n = 10) groups for any of the three sessions.

Fig. 4.

Responses of BALB/c mice in the prepulse inhibition (PPI) assay. Compared with mice born to sham-infected mothers (Control) (n = 14; 8 females), the mice born to infected mothers (Exposed) (n = 29; 15 females) display reduced PPI. These deficits are most significant at 75 dB, which is 10 dB higher than background (p< 0.05), and at 80 dB, which is 15 dB higher than background (p < 0.01).

Fig. 5.

The effect of ketamine on PPI. The psychomimetic drug ketamine was administered 5 min before testing the acoustic startle response. As expected, ketamine diminished the PPI response (with an 80 dB prepulse) in the BALB/c mice born to sham-infected mothers (Control) (n = 14; 8 females), but it increased PPI in mice born to virus-infected mothers (Exposed) (n = 29; 15 females). The difference in the drug-induced increases between control groups and experimental groups is significant (p < 0.02). Similar results were observed for C57BL/6 mice (n = 10 and 48 for control groups and experimental groups, respectively; p < 0.04).

Fig. 6.

The effect of antipsychotic drugs on PPI. The typical antipsychotic drug chlorpromazine and the atypical antipsychotic drug clozapine were acutely administered to BALB/c mice, and PPI responses (with an 80 dB prepulse) were assayed. As expected from previous studies with rats, the sham-infected mice (Control) (n = 10; 5 females) displayed a modest increase in PPI when tested after drug injection. In contrast, the mice born to virus-infected mothers (Exposed) (n = 21; 12 females) displayed an extremely large increase in PPI after drug administration. The difference in the drug-induced increases between the control group and the experimental groups is significant (*p < 0.03). Note that the data are expressed as the percentage of PPI increase.

Fig. 7.

The effect of maternal immune response in the absence of virus. Pregnant BALB/c mice were injected intraperitoneally on day 9.5 of pregnancy with one of three doses of poly(I:C) to evoke an antiviral-like immune response. The offspring were tested for PPI at 4 dB prepulse levels at 6–8 weeks of age. At the highest dose of poly(I:C), the offspring displayed a significant deficit in PPI (*p < 0.05; **p < 0.01) (n = 10 for each group; 5 females each).