Raymond H. Cypess

Immunosuppression and increased susceptibility to Japaneses B encephalitis virus in Trichinella spiralis-infected mice

Summary Infection with T. spiralis larvae greatly increased the susceptibility of mature mice to fatal CNS disease when challenged peripherally with JBE virus 7 days after administration of larvae. By 28 days following T. spiralis infection, susceptibility to JBE virus returned to control levels. It was found that this parasite caused a suppression of the neutralizing and complement-fixing antibody responses to JBE virus, whether challenged at 7 or 28 days. In contrast, infection with N. dubius larvae, or irradiated larvae of either parasite, had no effect on susceptibility or antibody responses to virus. Evidence of T. spiralis larval migration into the brains of infected mice was not observed. Increased corticosteroid hormone levels, suppression of the humoral antibody response, or changes in fixed macrophage phagocytic activity did not appear to constitute potential mechanisms for the increased susceptibility of T. spiralis-infected mice to JBE virus. 1

Heligmosomoides polygyrus (=Nematospiroides dubius): the development of self-cure and/or protection in several strains of mice.

Strains of outbred (ICR/CD1 and S--W) and inbred (BALB/C and C57BL/6) mice vaccinated subcutaneously (SQ) with 500, 1,000, or 2,000 exsheathed Heligmosomoides polygyrus larvae developed varying levels of protection upon subsequent oral challenge with larvae. In contrast, the inbred C3H/HEJ strain failed to develop protection at any dosage level tested. ICR/CD1 mice vaccinated intraperitoneally with exsheathed larvae developed a high level of resistance but exhibited extensive adhesions of the viscera. When ensheathed larvae were used for vaccination, ICR/CD1 mice developed a moderate level of protection; but 1% of the vaccine dose was recovered in the intestine as adult stages. Both the inbred and outbred strains given multiple oral infections developed a protection response similar to that strains response following parenteral vaccination. The specificity of this protection was demonstrated using various complex foreign antigens. In contrast, the self-cure response was observed only in the S--W strain.

Heligmosomoides polygyrus: Temporal, spatial, and morphological population characteristics in LAF1J mice

The course of an initial orally induced infection of Heligmosomoides polygyrus in the LAF1 strain of mice was compared to that observed in AHe mice. In LAF1 mice, the tissue-encysted larval-stage nematode lasts 1 to 2 days longer than in AHe mice. After larval emergence, the worms are not as successful in their anterior migration in LAF1 mice as they are in AHe mice. After Day 14, adult worms are lost from LAF1 mice, but not from AHe mice. Histologie study of the intestine did not reveal any significant difference between the mice, except to reflect the delay in larval emergence. The peripheral blood of the LAF1 mice showed a leukocytosis on Days 4 and 6, while the AHe mice had a leukopenia from Days 4 through 20. There was no change in the differential count. No anatomic explanation for post developmental adult expulsion was found.

Observations on trichinosis in the rhesus monkey.

Monkeys infected with 2.0 larvae/g body weight died 31-41 days post-infection (PI): two of three monkeys infected with 1.0 larva/g body weight became moribund and were sacrificed at 50 days, but six of six monkeys infected with 1.0 larva/g body weight were healthy 225 days PI. Periorbital and facial edema and eosinophilia were observed in all groups during the second week PI, and myalgia and stiffening of joints was observed during the third week. High numbers of encyse, biceps brachii and deltoideus. Adult worms were recovered from the intestine 49 days PI. The morphological changes were essentially similar to those seen in humans and a generalized lymphoid hyperplasia was not observed. Thus, rhesus monkeys develop trichinosis which show similarities clinically, pathologically and morphologically to human disease.