Widespread and structured distributions of blood parasite haplotypes across a migratory divide of the Swainson's thrush (Catharus ustulatus).

We examined the phylogenetic distribution of cytochrome b haplotypes of the avian blood parasite genera Haemoproteus and Plasmodium across the migratory divide of the Swainson's thrush (Catharus ustulatus) in British Columbia, Canada. From 87 host individuals, we identified 8 parasite haplotypes; 4 of Plasmodium and 4 of Haemoproteus. Six haplotypes were novel; 1 Haemoproteus haplotype was identical to H. majoris found in the blue tit (Parus caeruleus) in Sweden, and another halotype was identical to a Plasmodium haplotype found in the white-crowned sparrow (Zonotrichia leucophrys) in Oregon. The 2 most abundant parasite haplotypes were widely distributed across the contact zone, whereas 2 other parasite haplotypes seem to have structured distributions. Compared with 74 Plasmodium and Haemoproteus haplotypes published in GenBank, haplotypes recovered from Swainson's thrushes do not form monophyletic groups, and they are closely related to haplotypes from a variety of other hosts and localities. In addition, we recovered 2 Swainson's thrush Plasmodium haplotypes from the nonmigratory orange-billed nightingale thrush (Catharus aurantiirostris) in Costa Rica. This study is the first to elucidate avian blood parasite transmission, distribution, and phylogenetic relationships in an avian contact zone in North America.

Intravenous synthetic alphaGal saccharides delay hyperacute rejection following pig-to-baboon heart transplantation.

Several oligosaccharides containing the terminal structure Gal(alpha)1-3Gal (alphaGal) and different side chains were tested in vitro for their ability to block natural anti(alpha)Gal antibodies. A di-and a trisaccharide (di(alpha)Gal and tri(alpha)Gal) were selected. A blood group B baboon, having IgG and IgM natural antipig titers of 1:256 and 1:1024 and a hemolytic titer (to pig red blood cells, RBCs) of 1:8, was chosen to measure pharmacokinetic parameters of the saccharides and to assess the extent of in vivo neutralization of the antibodies. Three grams each of the di(alpha)Gal and the tri(alpha)Gal dissolved in saline were administered by bolus intravenous (i.v.) injection. Blood samples were collected at various times and urine was collected at 8 and 24 h. Plasma and urine concentrations of the alphaGal saccharides were estimated by an ELISA specially developed for this study. A fast distribution phase followed by equilibrium and excretion phases were observed, indicating a T1/2 in the order of 1 h. Fifty-eight per cent of the saccharides were recovered in the urine within 24 h. Determination of antipig antibody binding by FACS analysis and of serum cytotoxicity titers for pig endothelial cells demonstrated that a 70% reduction in binding and cytotoxicity could be achieved with plasma saccharide levels of 300-400 microg/ml. Six months later, a pig heart was transplanted heterotopically into the baboon. A 3-g bolus of the saccharide mixture (1.5 g of each saccharide) was given i.v. before allowing blood reperfusion of the transplanted heart, followed by an i.v. infusion of 1 g/hr for 1 hr and 0.5 g/hr for the 3 succeeding hours. Blood concentrations of the saccharides, CH50, hematology and cytotoxicity for PK15 cells were estimated in blood samples taken at various times. Heart function was observed to be satisfactory for 8 h, but was found to have ceased at 18 h. Myocardial biopsies taken at 3 and 5 h showed congestion only, suggestive of minimal vascular rejection, but by 18 h demonstrated severe vascular rejection. In conclusion, alphaGal saccharide therapy given for a period of 4 h delayed, but did not totally prevent, the development of vascular rejection in the pig-to-baboon heart transplant model. alphaGal saccharide therapy may be one of several useful approaches for the prevention of hyperacute rejection in pig-to-primate organ transplantation.

Humoral and cell-mediated immune responses in humans to the NSP4 enterotoxin of rotavirus.

Rotavirus nonstructural protein NSP4 has recently been suggested to function as a viral enterotoxin and play a role in the pathophysiological mechanism whereby rotaviruses induce diarrhea. The ability of rotavirus NSP4 to stimulate a humoral immune response was examined in naturally infected children and adults, rotavirus vaccinated children, as well as a cellular immune response in adults. In this study, 10 of 10 naturally infected children and 9 of 10 rotavirus-vaccinated children showed a weak humoral IgG immune response to recombinant NSP4 (rNSP4) and/or a synthetic peptide corresponding to residues 114-134 of NSP4. Modest serum IgG antibody responses were detected in 20 of 20 adults. A cellular immune response to rNSP4 and/or NSP4(114-134) were detected in 8 of 10 adults measured either as a T-cell proliferative response (7 of 10), an increased production of IL-2 (6 of 10), or increased production of interferon-gamma (8 of 10). These results indicate that NSP4 induces a humoral immune response in humans and show for the first time that NSP4 stimulates a cellular immune response, possibly including cytolytic T-cells.

Rotavirus infections in young Nicaraguan children.

BACKGROUND: Rotavirus is an important cause of dehydrating diarrhea in young children throughout the world. Knowledge about frequency of reinfections, development of immunity to the virus and the possible protective effect of breast milk is important, in particular in relation to possible strategies for immunization. METHODS: A prospective study of rotavirus infections in a cohort of 235 infants followed from birth until 2 years of age was performed in León, Nicaragua. Fecal and serum specimens were collected at specified times, and stools were also obtained during episodes of diarrhea. Fecal specimens were screened by rotavirus antigen detection and serum and colostral specimens were analyzed by isotype-specific rotavirus antibody enzyme-linked immunosorbent assay. RESULTS: As judged by anti-rotavirus IgA antibody seroconversion and/or demonstration of rotavirus antigen in fecal specimens, > 50% of the babies had evidence of past rotavirus infection by the age of 2 months. The total incidence of rotavirus infections, including many reinfections, was 0.7 infection/child-year, of which only 17% were associated with diarrhea. The time from birth to the first demonstration of rotavirus in stool samples correlated significantly with the concentration of anti-rotavirus IgA antibodies in colostrum. There was also a tendency toward a relationship between long duration of breast-feeding and asymptomatic infection. CONCLUSIONS: Rotavirus infections are acquired very early in infants in León, Nicaragua, and reinfections are common. Most infections are asymptomatic. Breast milk appears to confer partial protection against rotavirus infection, probably mediated by specific IgA antibodies. To be effective rotavirus vaccination would probably have to be given at a very early age to infants in developing countries.

Prevalence and characteristics of severe rotavirus infections in Nicaraguan children.

We analyzed the prevalence of rotavirus in 296 children age between 3 and 36 months who were hospitalized in 1994 with severe gastro-enteritis at two health centres for diarrhoea treatment in León, Nicaragua. Enteric viruses were detected in 96 (32.4%) of the children and rotaviruses were the most common pathogens detected in 84 (28%). The majority of rotavirus infections occurred in children less than 1 year old and all strains isolated belonged to subgroup II and had 'long' RNA patterns. Molecular epidemiology of 55 rotavirus strains revealed that all had the same RNA migration pattern and serotyping of 37 strains by PCR technology revealed that all isolates belonged to serotype 3. A significant observation was that only one electropherotype of rotavirus circulated. No non-group A rotaviruses were found by RNA gel electrophoresis. Adenoviruses were found by ELISA in 14 of 265 (5%) children and were most frequently detected during the 1st year of life. Of 103 faecal samples analyzed by electron microscopy, four contained small round structured viruses.