Neutralizing antibodies to heterologous animal rotavirus serotypes 5, 6, 7, and 10 in sera from Ecuadorian children

Prevalence of neutralizing antibodies against different rotavirus serotypes in children with severe rotavirus-induced diarrhea and their mothers

Neutralizing antibody (NAb) responses to different rotavirus serotypes were compared in 64 convalescent-phase serum samples from hospitalized rotavirus-positive children less than 2 years of age and their mothers. Compared to the child patients, the mothers showed significantly higher NAb positivity to animal rotavirus serotypes G3 simian (96.88%), G6 bovine (85.94%), and G10 bovine (25.0%) and to human rotavirus serotypes G8 (79.69%) and G3 (57.81%) (P < 0.01 for each) but not to human serotypes G1, G2, G4, and G9 (P > 0.05). The overall prevalence of NAb among the child patients was low for human rotavirus serotypes G1 (20.31%) and G3 (21.8%). The comparative NAb response in individual mother-child paired serum samples was analyzed against each rotavirus serotype. A substantial number of child patients showed higher NAb titers than their mothers to serotypes G1, G2, G4, and G9, indicating that these serotypes are the major serotypes causing rotavirus diarrhea among the children of Pune, India. In these cases, the mothers were either negative or had lower titers of NAbs than their children. Correlation was observed between the infecting serotype and child patient serum that showed a homologous NAb response at a higher level than that of the mother. It appears that when the level of NAb to a particular serotype is higher among child patients than among their mothers, that serotype is the infecting serotype, and that low titers of NAb among the mothers predispose the children to infection with that serotype, if the serotype is in circulation.

Glycosphingolipid binding specificities of rotavirus: identification of a sialic acid-binding epitope

The glycosphingolipid binding specificities of neuraminidase-sensitive (simian SA11 and bovine NCDV) and neuraminidase-insensitive (bovine UK) rotavirus strains were investigated using the thin-layer chromatogram binding assay. Both triple-layered and double-layered viral particles of SA11, NCDV, and UK bound to nonacid glycosphingolipids, including gangliotetraosylceramide (GA1; also called asialo-GM1) and gangliotriaosylceramide (GA2; also called asialo-GM2). Binding to gangliosides was observed with triple-layered particles but not with double-layered particles. The neuraminidase-sensitive and neuraminidase-insensitive rotavirus strains showed distinct ganglioside binding specificities. All three strains bound to sialylneolactotetraosylceramide and GM2 and GD1a gangliosides. However, NeuAc-GM3 and the GM1 ganglioside were recognized by rotavirus strain UK but not by strains SA11 and NCDV. Conversely, NeuGc-GM3 was bound by rotaviruses SA11 and NCDV but not by rotavirus UK. Thus, neuraminidase-sensitive strains bind to external sialic acid residues in gangliosides, while neuraminidase-insensitive strains recognize gangliosides with internal sialic acids, which are resistant to neuraminidase treatment. By testing a panel of gangliosides with triple-layered particles of SA11 and NCDV, the terminal sequence sialyl-galactose (NeuGc/NeuAcalpha3-Galbeta) was identified as the minimal structural element required for the binding of these strains. The binding of triple-layered particles of SA11 and NCDV to NeuGc-GM3, but not to NeuAc-GM3, suggested that the sequence NeuGcalpha3Galbeta is preferred to NeuAcalpha3Galbeta. Further dissection of this binding epitope showed that the carboxyl group and glycerol side chain of sialic acid played an important role in the binding of such triple-layered particles.

Detection of rotavirus types G8 and G10 among Brazilian children with diarrhea

Characterization of 49 rotavirus-positive stool specimens from children with diarrhea in the state of Rio de Janeiro, Brazil, in 1996 and 1997 revealed a great diversity of rotavirus G types. Conventional types G1 and G3 accounted for 27 and 12% of the infections, respectively, whereas 60% of the infections were caused by unconventional types G5 (25%), G10 (16%), and G8 (4%) and mixed G types (16%).

Bovine rotavirus 993/83 shows a third subtype of avian VP7 protein

VP7 genes of rotavirus (RV) 993/83 isolated from a German calf with diarrhea and of RV PO-13 isolated from a Japanese pigeon were sequenced. Alignment of the deduced VP7 amino acid sequence showed 98.8% sequence identity, while only 70% and 84% identity was seen with VP7 from chicken RV Ch-2 and turkey RV Ty-1, respectively. Over the antigenic regions A, B, and C mammalian RV 993/83 showed more aa identity with mammalian G3 RVs than with chicken RV Ch-2, which could explain the strong one-way cross-neutralization observed between RV 993/83 and G3 RVs. Despite marked VP7 sequence diversity avian RVs could not be differentiated into distinct G types.

Effect of malnutrition on serum and milk antibodies in Zairian women

Serum and human milk antimicrobial antibody titers were measured longitudinally in 17 malnourished and 14 control Zairian women during 6 to 18 months of lactation to test whether malnutrition is specifically associated with an impaired secretory antibody response. No decreases in total serum and human milk immunoglobulin concentrations, neutralizing antibody titers against rotavirus, or specific enzyme-linked immunosorbent assay antibody titers against rotavirus, respiratory syncytial virus, Escherichia coli, Streptococcus pneumoniae, and Haemophilus influenzae were detected when malnourished women were compared with control women. Malnutrition had no effect on circulating and secretory antibody concentrations in Zairian women. Daily human milk outputs, however, were about 30% lower in malnourished than in control women, resulting in a correspondingly lower ingestion of immunoglobulins by the children of malnourished women.

Prevalence of neutralizing antibodies to 9 rotavirus strains representing 7 G-serotypes in sheep sera

Neutralizing antibodies to 9 rotavirus strains representing serotypes G1, G3, G5, G6, G8, G9, and G10 were investigated in 212 ovine serum samples from 3 age groups, 1-week-old lambs, 2- to 3-months-old lambs and adult sheep. All sera from 1-week-old lambs had neutralizing antibodies to all 9 rotavirus strains. Both neutralizing antibody titers and prevalences to all 9 strains markedly decreased in the 2- to 3-months-old lamb group and increased again in the adult sheep group. Also, adult sheep sera neutralized a larger number of rotavirus strains than 2- to 3-months-old lamb sera. The highest neutralizing antibody titers and prevalences were found to strains B223 and K923, representing serotype G10, to strain RRV, representing serotype G3, and to strain NCDV, representing serotype G6, indicating that these could be the predominant 3 rotavirus serotypes in Spanish sheep. The rotavirus serotypes infecting sheep observed by us differ from those described for cattle, where G6 is the most prevalent serotype followed by G10, and G3 has been seldom found. Very low prevalences were observed for strains WA and OSU representing serotypes G1 and G5 respectively, suggesting that they probably do not infect sheep and neutralizing antibodies found are derived from heterotypic responses to other serotypes. Intermediate prevalences and titers were found to strains UK (serotype G6), 69M (serotype G8) and WI61 (serotype G9). Neutralizing antibodies distinguished between different strains sharing their VP7 specificity: B223 and K923, a bovine and an ovine serotype G10 strains, and NCDV and UK, two serotype G6 bovine rotavirus strains with different VP4 antigen.

Rotavirus serotype G5 associated with diarrhea in Brazilian children

Rotavirus serotype G5 in fecal specimens of 38 Brazilian children with diarrhea was identified by PCR and enzyme immunoassays. The strains exhibited long RNA electropherotypes and either subgroup II or nonsubgroup I-nonsubgroup II specificities. Serotype G5 has been found in piglets and horses but not yet in humans.

Detection of rotavirus serotypes G1, G2, G3, and G11 in feces of diarrheic calves by using polymerase chain reaction-derived cDNA probes

On the basis of antigenic variability in the VP7 outer capsid glycoprotein, at least 14 G serotypes exist for group A rotaviruses. Serotypic diversity exists among bovine rotaviruses (BRV), with serotypes G1, G6, G8, and G10 reported for cattle. Although G1 and G8 rotaviruses were originally described for humans, the recent isolation of G6 and G10 rotaviruses from humans further emphasizes the serotypic similarity between human and bovine rotaviruses and the possible zoonotic potential of rotaviruses. Results of our previous studies have indicated that more than 24% of BRV-positive field samples from diarrheic calves were nonreactive with cDNA probes or monoclonal antibodies to serotypes G6, G8, and G10. In this study, cDNA probes were prepared by polymerase chain reaction amplification of the hyperdivergent regions of the VP7 genes (nucleotides 51 to 392) from human (G1, G2, and G3) and porcine (G4, G5, and G11) rotaviruses. These probes were used in a dot blot hybridization assay to further characterize the G types of 59 BRV strains (fecal samples from diarrheic calves in Ohio, Nebraska, Washington, and South Dakota) that were nonreactive with cDNA probes to G6, G8, and G10. Rotaviruses belonging to serotypes G1 (n = 7), G2 (n = 1), G3 (n = 2), and G11 (n = 3) were identified among the BRV field samples. The BRV associated with these G types accounted for 22% of the samples tested; the other 78% of these samples remained untypeable with these probes. To our knowledge, this is the first report in the United States of the identification among BRV isolates of rotavirus serotypes G1, G2, G3, and G11.

Rotavirus-inhibitory activity in serial milk samples from Mexican women and rotavirus infections in their children during their first year of life

A total of 75 children born in rural Mexico were followed for diarrheal diseases and rotavirus (RV) excretion during the first year of life. For 18 children, an average of 14 serial breast milk samples were obtained between days 2 and 360 after delivery and were tested for RV-inhibitory activity. Of these samples, 70, 62, and 85% showed inhibitory activity against serotype (ST) 1 human RV, ST4 human RV, and ST3 simian RV, respectively; the median titers were 10, 10, and 20, respectively. Some 89% of the milk samples showed RV-specific antibodies in an enzyme-linked immunosorbent assay (median titer, 20). Surprisingly, 98% of the milk samples inhibited ST6 bovine RV. ST6, but not ST1, RV-inhibitory activity survived heat treatment (10 min at 80 degrees C). Of the 18 children tested, 13 children experienced 23 episodes of diarrhea (enterotoxigenic [n = 8] and enteropathogenic [n = 3] Escherichia coli, Campylobacter jejuni [n = 4], Shigella flexneri [n = 2], RV [n = 1]) and 5 children experienced 6 RV infections. Only one RV infection was associated with diarrhea. The five RV excretors did not differ from the nonexcretors with respect to the RV-inhibitory activity in the breast milk fed to them. The RV-inhibitory titers were too low in the majority of the studied Mexican milk samples to indicate an important effect of breast-feeding on the take rate of oral human, simian, or reassortant RV vaccines. Breast-feeding might, however, inhibit the take rate of a bovine RV vaccine.

A bovine rotavirus serotype 1: serologic characterization of the virus and nucleotide sequence determination of the structural glycoprotein VP7 gene

Bovine rotavirus T449 was isolated from feces of a calf with diarrhea. Serological characterization by serotype-specific monoclonal antibodies showed that the T449 virus belonged to serotype 1. This is the first report of a bovine rotavirus that does not belong to serotype 6, 8, or 10. The serotype 1 designation was confirmed by using an immunoperoxidase focus neutralization assay. The gene encoding the major neutralization antigen (VP7) was cloned and its nucleotide sequence was determined. The sequence obtained was 1062 bp in length and contained an open reading frame corresponding to 326 amino acid residues. Comparative analysis of the deduced amino acid sequence with the corresponding sequence of the human serotype 1 rotavirus strain, Wa, revealed a 90% identity. When compared to the predicted amino acid sequence of VP7 protein of the other serotypes an overall divergence of 20 to 25% was detected. These data show that the serological typing agrees with the result of the genetic analysis.

Neutralizing serum antibodies to serotype 6 human rotaviruses PA151 and PA169 in Ecuadorian and German children

Serum samples from 726 Ecuadorian children who underwent natural rotavirus (RV) exposure were tested for neutralizing serum antibodies against two serotype 6 (ST6) human RV (HRV) isolates from Italy, PA151 and PA169, and two ST6 bovine RV (BRV) isolates, NCDV and UK. Gene 4 was distinct in all four ST6 strains. Ninety-one, 56, 67, and 65 serum samples neutralized HRV PA151 (13%), HRV PA169 (8%), BRV NCDV (9%), and BRV UK (9%), respectively. A total of 44 of the 91 serum samples which neutralized HRV PA151 did not neutralize the other three ST6 RV strains. In addition, we identified three serum samples that neutralized HRV PA151 but none of the six human or four animal RV STs. However, we failed to identify serum samples that neutralized HRV PA169 without neutralizing at least one of the major HRV STs. With a hospital-based serum collection from German children (excluding gastroenteritis patients), we identified 3 out of 197 serum samples tested that neutralized HRV PA151 specifically, whereas none neutralized HRV PA169 exclusively. None of the 71 German infants hospitalized with primary RV gastroenteritis showed a PA151- or a PA169-specific antibody response.

Antibodies to seven rotavirus serotypes in cord sera, maternal sera, and colostrum of German women

Forty percent of colostrum samples from German women showed neutralizing antibody titers of greater than or equal to 50 to rotavirus (RV) serotypes 1, 3, 4, and 6. Antibody to serotypes 2, 8, and 9 was less prevalent. Titers are, however, too low to indicate an important effect of colostrum on the RV vaccine take rate. On the other hand, about 50% of the cord serum samples showed high neutralizing-antibody titers to serotypes 1, 3, and 4, which could interfere with the take rate of RV vaccines based on these serotypes in very young infants.