Distribution of rotavirus genotypes causing nosocomial and community-acquired acute gastroenteritis at the Children's Hospital of Philadelphia in the new rotavirus vaccine era.

BACKGROUND: Introduction of rotavirus vaccines in the United States beginning in 2006 led to a rapid decline in the frequency of acute rotavirus gastroenteritis necessitating medical attention. We examined whether serotype replacement was occurring as a result of vaccine use. METHODS: Children with gastroenteritis presenting to CHOP have been tested for rotavirus antigen in the stool. Commencing with the 1999-2000 season, positive specimens were genotyped to establish the G (VP7) and P (VP4) type. RESULTS: In 2009-2010, 4 hospital-acquired and 18 community-acquired cases of rotavirus gastroenteritis were identified at CHOP. For the third consecutive full season since the introduction of rotavirus vaccines, the proportion of annual G3 cases was higher than in the prevaccine era. Although G3 strains caused 50% of the community cases in 2009-10, the absolute number of G3 cases actually dropped from 15 in 2007-08 to 8 and 9 in the 2008-09 and 2009-10 seasons, respectively. P[8] accounted for > 90% of cases seen at CHOP in each of the last 3 seasons, including 20/22 (91%) cases during the 2009-10 season. CONCLUSIONS: Findings to date provide suggestive but still inconclusive evidence for vaccine-driven serotype replacement. Given the increased proportion of G3 cases in the new vaccine era despite the overall marked reduction in rotavirus gastroenteritis, continued surveillance is prudent.

Influence of potential protective mechanisms on the development of live rotavirus vaccines.

Rotaviruses cause extensive morbidity and mortality worldwide, thus corroborating the need for a vaccine that is effective in all socioeconomic environments. Vaccines evaluated in clinical trials have all been live attenuated rotaviruses that are delivered orally to mimic the excellent protection observed after natural infection. The mechanisms by which these vaccine candidates or wild-type rotaviruses elicit protection are not fully understood. During the 1980s, several candidate vaccines provided little protection, particularly in developing countries, and were discontinued. Two, however, are in the process of being licensed worldwide, and several others are undergoing clinical trials. Development of live rotavirus vaccines has been highly influenced by views regarding the importance of serotype-specific neutralizing antibody. Development of several candidate vaccines is based on the concept that neutralizing antibody is the primary determinant of protection. These candidates, including 1 of the 2 being licensed worldwide (RotaTeq), are composed of multiple rotavirus strains representative of the major human rotavirus serotypes. The other group of candidates has been developed based on the theory that protection is not solely dependent on neutralizing antibody. These candidates are composed of single rotavirus strains and include the other vaccine being licensed worldwide (Rotarix). Studies that provide the basis for each approach will be presented and discussed.

Unexpectedly high burden of rotavirus gastroenteritis in very young infants.

BACKGROUND: The highest incidence of rotavirus gastroenteritis has generally been reported in children 6-24 months of age. Young infants are thought to be partially protected by maternal antibodies acquired transplacentally or via breast milk. The purpose of our study was to assess the age distribution of children with confirmed community-acquired rotavirus gastroenteritis presenting to an urban referral hospital. METHODS: Children presenting to The Children's Hospital of Philadelphia with acute gastroenteritis have been monitored for the presence of rotavirus antigen in the stool by ELISA (followed by genotyping if ELISA-positive) since the 1994-95 epidemic season. RESULTS: Over the last 12 rotavirus seasons prior to the introduction of the pentavalent rotavirus vaccine in 2006, stool specimens from 1646 patients tested positive for community-acquired rotavirus infection. Gender or age was not recorded in 6 and 5 cases, respectively. Overall, 58% of the cases occurred in boys. G1 was the predominant VP7 serotype, accounting for 72% of cases. The median (IQR) age was 11 (5-21) months. A total of 790 (48%) cases occurred in children outside the commonly quoted peak age range, with 27% in infants <6 months of age and 21% in children >24 months of age. A total of 220 (13%) cases occurred during the first 3 months of life, and the highest number of episodes per month of age [97 (6%)] was observed during the second month of life. CONCLUSIONS: The incidence of community-acquired rotavirus gastroenteritis monitored over 12 seasons in the prevaccine era at a major university hospital was nearly constant for each month of age during the first year of life, revealing an unexpectedly high incidence of symptomatic rotavirus disease in infants <3 months old. A sizeable fraction of cases occurred in children too young to have been vaccinated according to current recommendations.

Safety and efficacy of a pentavalent human-bovine (WC3) reassortant rotavirus vaccine.

BACKGROUND: Rotavirus is a leading cause of childhood gastroenteritis and death worldwide. METHODS: We studied healthy infants approximately 6 to 12 weeks old who were randomly assigned to receive three oral doses of live pentavalent human-bovine (WC3 strain) reassortant rotavirus vaccine containing human serotypes G1, G2, G3, G4, and P[8] or placebo at 4-to-10-week intervals in a blinded fashion. Active surveillance was used to identify subjects with serious adverse and other events. RESULTS: The 34,035 infants in the vaccine group and 34,003 in the placebo group were monitored for serious adverse events. Intussusception occurred in 12 vaccine recipients and 15 placebo recipients within one year after the first dose including six vaccine recipients and five placebo recipients within 42 days after any dose (relative risk, 1.6; 95 percent confidence interval, 0.4 to 6.4). The vaccine reduced hospitalizations and emergency department visits related to G1-G4 rotavirus gastroenteritis occurring 14 or more days after the third dose by 94.5 percent (95 percent confidence interval, 91.2 to 96.6 percent). In a nested substudy, efficacy against any G1-G4 rotavirus gastroenteritis through the first full rotavirus season after vaccination was 74.0 percent (95 percent confidence interval, 66.8 to 79.9 percent); efficacy against severe gastroenteritis was 98.0 percent (95 percent confidence interval, 88.3 to 100 percent). The vaccine reduced clinic visits for G1-G4 rotavirus gastroenteritis by 86.0 percent (95 percent confidence interval, 73.9 to 92.5 percent). CONCLUSIONS: This vaccine was efficacious in preventing rotavirus gastroenteritis, decreasing severe disease and health care contacts. The risk of intussusception was similar in vaccine and placebo recipients. (ClinicalTrials.gov number, NCT00090233.)

The clinical and molecular epidemiology of community- and healthcare-acquired rotavirus gastroenteritis.

BACKGROUND: Rotavirus is the most common etiologic agent of healthcare-acquired diarrhea in pediatric patients. There has been little published information on healthcare-acquired rotavirus infection. METHODS: This was a retrospective cohort study of children hospitalized with rotavirus gastroenteritis at our institution between December 1999 and May 2004. Patients with community- and healthcare-acquired rotavirus gastroenteritis were compared with regards to age, time of infection, patient unit, and viral subtype as determined by reverse transcription polymerase chain reaction sequencing. RESULTS: Five hundred seventy-seven children were hospitalized with rotavirus gastroenteritis during the study period. One hundred twenty-one (21%) of these infections were healthcare-acquired. The incidence of healthcare-acquired infection was 4.2 cases per 10,000 patient-days. With the exception of 1 outbreak on an isolated patient unit, community- and healthcare-acquired disease affected similar patient populations, had the same temporal distribution, and were caused by viruses with similar subtypes. However, there was a significant difference between the geographic distribution of community- and healthcare-acquired disease within the hospital (P < 0.001). The majority (83%) of community-acquired cases were admitted to general medicine-surgery units, but only 53% of the healthcare-acquired cases occurred on these units (P = 0.005). The remaining healthcare-acquired infections occurred on units that rarely admitted patients with community-acquired disease. CONCLUSIONS: Healthcare-acquired rotavirus gastroenteritis seems to be caused by repeated introduction of community strains into the hospital setting. Heightened attention to infection control practices and rapid rotavirus identification is necessary on all units, especially those that infrequently admit children with rotavirus gastroenteritis, to prevent the spread of healthcare-acquired disease.

The new pentavalent rotavirus vaccine composed of bovine (strain WC3) -human rotavirus reassortants.

BACKGROUND: Infantile gastroenteritis caused by human rotaviruses is a prevalent disease throughout the world, causing dehydration and hospitalization in all countries. In developing countries, it is associated with a high mortality. A licensed vaccine against rotavirus was withdrawn because of a causal association with intussusception. A new vaccine has been developed and is a candidate for licensure. METHODS: To recount the early development and recent demonstration of the safety and efficacy of the new vaccine. A bovine rotavirus attenuated for humans was isolated and reassorted with human rotaviruses of serotypes G1-4 and P1 to create a pentavalent vaccine. Multiple placebo-controlled clinical trials, including one involving approximately 70,000 infants, were conducted in multiple developed countries. RESULTS: The pentavalent vaccine was well tolerated by infants less than 8 months of age, and the incidence of intussusception was similar among vaccine and placebo recipients. More than 90% of infants had a significant rise in serum antirotavirus IgA titer after 3 doses. Efficacy of 95% against severe disease causing hospitalization or emergency care was demonstrated, and pentavalent vaccine prevented 74% of all rotavirus disease. CONCLUSIONS: If widely used, pentavalent vaccine would control rotavirus disease in the United States and other developed countries and could also have a major effect in developing countries.

Infant immune response to human rotavirus serotype G1 vaccine candidate reassortant WI79-9: different dose response patterns to virus surface proteins VP7 and VP4.

BACKGROUND: Rotavirus is the leading cause of morbidity from gastroenteritis in the developed world and the leading cause of mortality from viral gastroenteritis (estimated 600000 deaths) worldwide. G1 is the most prevalent human serotype. Reassortant rotavirus between simian rotavirus RRV or bovine rotavirus WC3 and human strain rotaviruses have been extensively tested as candidate vaccines. Rotavirus (RV) reassortant strain WI79-9 consists of a human (strain WI79) G1 serotype VP7 surface protein on a bovine (strain WC3) background. It is a key component of a pentavalent (G1, G2, G3, G4 and P1) WC3 reassortant vaccine candidate, RotaTeq, now being tested in Phase III clinical trials. METHODS: We studied 84 infants between the ages of 2 and 8 months who received 3 oral doses of WI79-9. Serum neutralizing antibody was measured to the human (WI79 serotype P1 G1) and bovine (WC3 serotype P7 G6) parent RV after each dose. A significant response was defined as a > or =3-fold rise in antibody titer between the predose and postdose sera. RESULTS: In two separate cohorts of vaccinees given three doses of WI79-9 reassortant rotavirus, 68 to 75% of infants demonstrated a significant response to WC3 (VP4, P7) after Dose 1, fewer (24 to 39%) responses were detected after Dose 2 and rare (0 to 4%) additional responses occurred after Dose 3. The cumulative response rate to WC3 after three doses was 95% in both trials. In contrast 23 to 37% had a significant response to WI79 (VP7, G1) after Dose 1, and 57 to 61% had a significant response after Dose 2. Additional significant responses after Dose 3 led to a cumulative response of 70 to 84%. CONCLUSION: Two doses of G1 reassortant WI79 were necessary to induce significant antibody responses to human G1 (VP7) antigen in >50% of infants. Three doses were required to achieve significant antibody responses to VP7 in >70% of infants.

Safety, immunogenicity and efficacy in healthy infants of G1 and G2 human reassortant rotavirus vaccine in a new stabilizer/buffer liquid formulation.

BACKGROUND: A refrigerator-stable rotavirus (RV) vaccine that withstands gastric acid is anticipated to permit more widespread use of RV vaccine. OBJECTIVE: We investigated for the first time in infants an oral, liquid formulation of G1 and G2 human bovine reassortant rotavirus vaccine (HRRV) with a new stabilizer/buffer (S/B) containing sucrose, sodium phosphate and sodium citrate. METHODS: During 1997 through 1998, 731 healthy infants approximately 2 to 4 months of age were enrolled at 19 US sites to receive 3 HRRV or placebo doses approximately 6 to 8 weeks apart in a partially double blinded study. Infants were randomized to: (1) HRRV with no S/B but with prefeeding; (2) HRRV plus 1 of 3 different concentrations/volumes of S/B; or (3) placebo. RESULTS: No serious vaccine-related adverse experiences or intussusception cases were reported. No statistically significant differences were observed between vaccine and placebo recipients for fever (> or =38.1 degrees C) 0 to 7 days after any dose, irritability, vomiting or diarrhea incidence 0 to 42 days after any dose. Vaccine virus shedding among vaccine recipients was uncommon. Among S/B vaccine groups, proportions of infants with a > or =3-fold titer rise from baseline to Postdose 3 for G1 serum-neutralizing antibody (SNA), G2 SNA, WC3 SNA, serum anti-RV IgA, serum anti-RV IgG and stool anti-RV IgA were generally similar to those of the prefed non-S/B group. CONCLUSIONS: HRRV with a new S/B was generally well-tolerated; immunogenicity was generally similar to the prefed non-S/B group. No intussusception cases were reported, but the small sample size precluded a definitive conclusion. A large international clinical study is under way to address safety and efficacy of an S/B formulation of a pentavalent version of HRRV.

Vaccines for rotavirus gastroenteritis universally needed for infants.

Rotavirus causes severe and often lifethreatening illness. Universal application of a safe and protective vaccine is justified in both developed and developing nations. Two vaccine candidates, one monovalent (Rotarix) and one multivalent (Rotateq), appear to meet these requirements and are likely to be licensed in the United States in the next 2 or 3 years. Both vaccines exhibited similar safety characteristics. There is little doubt that Rotateq and Rotarix will be shown to be effective for routine protection of infants. Unfortunately, despite numerous clinical trials, the most common serotype (PlaGa) commonly has been encountered as a natural challenge. Therefore, it is not known whether either vaccine possesses advantages in different epidemiological situations. Continuing the analogy with influenza virus, it may be that optimum protection against different serotypes requires a vaccine that is precisely homologous in antigen composition. If so, Rotateq would provide protection against the most common serotype PlaG1 because in includes both Pla and G1 rotavirus reassortants. Further, it would be expected to provide superior protection against G2, G3, and G4 wild-type virus because it contains reassortants of those specificities. In the case of a natural challenge with a serotype that was not G1, G2, G3, or G4, a Rotateq preparation containing a WC3 reassortant expressing the new G serotype could be formulated readily. The monotypic Rotarix may provide ideal protection against the PlaG1 rotavirus because it is composed solely of the PlaG1 strain. It may also provide cross-protection against other rotavirus serotypes adequate to protect against severe and life-threatening disease. In such a case, its monotypic composition may also provide significant economic savings in manufacturing. The resolution of these questions may have to await extensive post-licensure experience with each vaccine. In the future, possible application of rotavirus vaccine for other situations also should be explored, including use in older children to limit nosocomial infection, use in geriatric populations, use in the immunocompromised host, and possibly use in parents and other adults in contact with infants with rotavirus. Both Rotarix and Rotateq likely are to be launched at prices beyond those affordable in the poorest and neediest less-developed countries. It is essential that there be vigorous pursuit of new technologies to manufacture these products at drastically reduced cost if their true lifesaving potential is to be achieved.

An unusual outbreak of rotavirus genotype G2P[6] during the 2005-2006 epidemic season in Philadelphia.

Most rotavirus gastroenteritis is caused by G1P[8] strains. When G2 infections are encountered, the P type has most often been reported to be P[4]. The purpose of our study was to describe an unusual outbreak of G2P[6] cases. Children presenting to The Children's Hospital of Philadelphia with acute gastroenteritis have been monitored for rotavirus antigen in stool by ELISA (with G-typing if ELISA positive) since 1994-1995. Compared to the last 12 rotavirus seasons before the 2006 introduction of a new rotavirus vaccine, the 2005-2006 season had by far the highest number of evaluable rotavirus infections [n = 275 from September 2005 through June 2006, of which 261 (95%) were G typed] and the greatest number of G2 cases (n = 101, 39% of typed strains). Only 16% of G2 strains were associated with P[4], whereas genotype G2P[6] was responsible for 83% of the G2 infections. Eighty-eight percent of the 84 G2P[6] cases occurred in the 60% of patients who were African-Americans, most of whom were urban residents. Among 157 African-American patients, G2 cases (n = 80; 52%) predominated, including 74 due to G2P[6]. Children <6 months old accounted for 27% of cases overall, but 36% of the G2P[6] cases. G2 rotaviruses caused over a third of the community-acquired rotavirus cases in children presenting to CHOP in 2005-2006, attesting to the potential impact of G2 strains during some epidemics. The large majority of G2 strains had the rare P[6] genotype. Urban African-American children under 6 months of age were disproportionately affected.

Sustained decline in cases of rotavirus gastroenteritis presenting to the Children's Hospital of Philadelphia in the new rotavirus vaccine era.

BACKGROUND: A dramatic diminution in the number of rotavirus gastroenteritis cases during the 2007 to 2008 rotavirus season in the United States was likely attributable to the availability of an effective rotavirus vaccine for infants since February 2006. To exclude the possibility that factors other than vaccination accounted for the declining case frequency, we examined the 2008 to 2009 experience at the Children's Hospital of Philadelphia (CHOP). METHODS: Infants with acute gastroenteritis presenting to CHOP have been monitored for the presence of rotavirus antigen in the stool by enzyme-linked immunosorbent assay (followed by serotyping if enzyme-linked immunosorbent assay-positive) since the 1994 to 1995 epidemic season. RESULTS: The number of community-acquired cases during the last full rotavirus season before licensure of a vaccine was 271 in 2005 to 2006, followed by 167 cases in 2006 to 2007 and 36 in 2007 to 2008. Between 2008 and 2009, 73 community-acquired cases were identified. Almost half of the cases were seen among children older than 2 years. Unlike the late-appearing 2007 to 2008 season, the 2008 to 2009 season paralleled the typical time course observed in the prevaccine era. G9P[8] strains caused 64% of the cases. CONCLUSION: The sustained decline in the frequency of community-acquired rotavirus gastroenteritis has likely resulted from the use of the new rotavirus vaccines. The age distribution of children hospitalized for rotavirus gastroenteritis has shifted toward older children with the introduction of effective vaccines. The G9 serotype (not included in either vaccine) emerged as the most common cause of rotavirus gastroenteritis at CHOP during the 2008 to 2009 season.

Decline in cases of rotavirus gastroenteritis presenting to The Children's Hospital of Philadelphia after introduction of a pentavalent rotavirus vaccine.

A pentavalent rotavirus vaccine for infants became available in the United States in February 2006. By 2007, vaccination rates nationwide were estimated to be approximately 50%. We studied the effectiveness of the vaccine in a real-world setting outside of a clinical trial. All children presenting to The Children's Hospital of Philadelphia with acute gastroenteritis have been monitored for the presence of rotavirus antigen in the stool by enzyme-linked immunosorbent assay (ELISA [followed by genotyping if ELISA positive]) since the 1994-1995 epidemic season, presenting a unique opportunity to assess the impact of the recently introduced vaccine. The annual number of community-acquired cases over the preceding 13 years had approached or exceeded 100, with 271 cases in 2005 to 2006 and 167 cases in 2006 to 2007. In the 2007-2008 season, only 36 community-acquired cases were identified, representing an 87% reduction from the same period in 2005 to 2006. G3 was the predominant serotype, accounting for 15 community cases (42%). Our study is limited by its observational design using historical comparisons. Nonetheless, the abrupt decline in rotavirus gastroenteritis cases during the 2007-2008 season likely resulted from vaccination. Because protection rates appeared to have exceeded vaccination rates, herd immunity may have contributed to some degree to the effectiveness of the vaccine.

Effects of the potency and composition of the multivalent human-bovine (WC3) reassortant rotavirus vaccine on efficacy, safety and immunogenicity in healthy infants.

BACKGROUND: Rotavirus gastroenteritis, which causes substantial infant mortality and morbidity worldwide, is a vaccine-preventable disease. The purpose of this study was to evaluate different compositions and potencies (vaccine virus titers) of a live multivalent human-bovine (WC3) reassortant rotavirus vaccine in order to select the potency and composition of the vaccine for further development. METHODS: The efficacy, safety, and immunogenicity of a G1, G2, G3, G4, and P1A pentavalent composition at three different potencies, a G1, G2, G3, G4 quadrivalent composition, and a P1A monovalent composition of an oral human-bovine (WC3) reassortant rotavirus vaccine were compared in a blinded, placebo-controlled trial conducted between 1998 and 2001 enrolling 1,946 healthy Finnish infants 2-8 months of age. RESULTS: All potencies of the pentavalent and quadrivalent vaccines were efficacious (58-74%) against wild-type rotavirus gastroenteritis of any severity and 100% protective against severe rotavirus disease caused by vaccine G-serotypes through the first rotavirus season post-vaccination. The monovalent P1A vaccine was 53% efficacious against moderate-and-severe rotavirus gastroenteritis. Protection against rotavirus gastroenteritis of any severity was demonstrated through two and three rotavirus seasons for all vaccine compositions. After the third dose, the percentage of infants with >or=3-fold rise in baseline serum neutralizing antibody titers against G1 ranged from 62% to 86% for recipients of the pentavalent vaccine, depending on the potency. The incidence of fever, irritability, vomiting, and diarrhea did not significantly differ between vaccine and placebo groups. A 7-month-old male developed intussusception 9 days after the first dose of the low-potency pentavalent vaccine. CONCLUSIONS: Based on the results of this trial, a pentavalent composition (G1, G2, G3, G4, and P1A) of human-bovine (WC3) reassortant rotavirus vaccine with a potency similar to that of the middle-potency pentavalent vaccine ( approximately 8 x 10(6) plaque-forming units/dose) was selected for further development.

Development of a pentavalent rotavirus vaccine against prevalent serotypes of rotavirus gastroenteritis.

The strategy of decreasing the morbidity and mortality associated with rotavirus gastroenteritis through vaccination is supported by studies demonstrating that wild-type rotavirus infection protects against subsequent rotavirus disease. Primary infection with wild-type rotavirus typically induces homotypic immunity. Vaccination of infants with a multivalent vaccine directed against prevalent rotavirus serotypes is the strategy most likely to provide the broadest degree of protection against rotavirus gastroenteritis. The pentavalent human-bovine reassortant rotavirus vaccine (HBRV) is directed against each of the most prevalent rotavirus serotypes, including G1, G2, G3, G4, and P1. The safety, immunogenicity, and efficacy of different reassortant compositions and formulations of the HBRV have been evaluated in clinical trials. An HBRV dose of > or =8 x 10(6) plaque-forming units has demonstrated 68.8%-76.6% efficacy against any rotavirus gastroenteritis, regardless of severity, and approximatel 100% efficacy against severe rotavirus gastroenteritis for the first rotavirus infection season after vaccination. The HBRV has been generally well tolerated, with no increase in the incidence of fever, vomiting, diarrhea, or behavioral changes among vaccine recipients, compared with placebo recipients, during the 14- and 42-day periods after administration of any dose. Shedding of vaccine strains in feces is uncommon. A large-scale trial is under way to evaluate the efficacy and safety of the manufacturing-scale formulation of pentavalent HBRV.

Novel rotavirus VP7 typing assay using a one-step reverse transcriptase PCR protocol and product sequencing and utility of the assay for epidemiological studies and strain characterization, including serotype subgroup analysis.

Rotavirus is the most common cause of severe dehydrating gastroenteritis in infants. To date, 10 different serotypes of rotavirus have been identified in human stools. While four or five serotypes dominate, serotype circulation varies with season and geography. Since our laboratory has been involved in the development of a multivalent rotavirus vaccine, it is important to identify the serotypes of rotavirus encountered during our clinical trials. We have developed methodologies for the molecular identification of rotavirus strains based on VP7 gene segment sequence. A 365-bp reverse transcriptase PCR product was generated from the VP7 gene segment using a pair of novel degenerate primers. All serotypes tested (both animal and human) yielded an identically sized product after amplification. Sequencing of these products is performed using truncated versions of the original primers. The sequence generated is compared against a database of rotavirus VP7 sequences, with the G type determined, based on the sequence homology. Using this assay, we have correctly identified human VP7 strains from a panel of available serotypes, as well as numerous animal strains. The assay was qualified using rotavirus positive stool samples, negative stool samples, and rotavirus-spiked stool samples. In addition, samples from cases of acute gastroenteritis collected at Children's Hospital of Philadelphia have been evaluated and indicate that the assay is able to discriminate subtle differences within serotypes. The assay has been utilized in the testing of >3,000 antigen-positive (enzyme immunoassay) samples collected during clinical trials of a rotavirus vaccine (RotaTeq) and identified a serotype in approximately 92% of samples (3, 17, 19).

Memory T-cell response to rotavirus detected with a gamma interferon enzyme-linked immunospot assay.

Measurements of serum-neutralizing antibody and anti-rotavirus immunoglobulin A (IgA) are the current standard for assessing immune responses following rotavirus vaccination. However, there is ongoing debate as to whether antibody titers correlate with protection against rotavirus gastroenteritis. Children recovering from rotavirus gastroenteritis have increased gamma interferon release from cultured peripheral blood mononuclear cells (PBMCs), suggesting that cell-mediated immunity (CMI) may play a role in viral clearance and protection from subsequent gastroenteritis. We have developed a gamma interferon enzyme-linked immunospot (ELISPOT) assay for evaluation of CMI responses to rotavirus using frozen PBMCs obtained from healthy adults. Responses to three different rotavirus antigen types were analyzed-a peptide pool based on the human VP6 sequence; reassortant human:bovine vaccine strains; and cell culture-adapted (CCA) human G1, G2, G3, G4, and bovine (WC3) G6 strains. The reassortant strains consist of a bovine WC3 genome background expressing the human rotavirus surface proteins VP7 (G1, G2, G3, or G4) or VP4 (P1). Responses to titrations of the peptide pool as well as CCA and reassortant strains were assessed. Gamma interferon ELISPOT responses were similar for CCA and reassortant strains, whether live or UV inactivated, and when tested either individually or pooled. For most subjects, responses to the VP6 peptide pool positively correlated with responses to CCA and reassortant strains. Cell depletion studies indicate the memory responses detected with these frozen adult PBMCs were primarily due to the CD4+ T-cell population. This gamma interferon ELISPOT assay provides a new tool to apply in clinical studies for the characterization of natural or vaccine-induced CMI to rotavirus.

A comparison of the effects of oral inoculation with Rotashield and pentavalent reassortant rotavirus vaccine (WC3-PV) on suckling CB17scid mice.

The effects of oral inoculation into infant CB17(scid) mice of two reassortant rotavirus vaccines were compared. The vaccines were Rotashield and WC3-PV, a mixture of five reassortants (G1, G2, G3, G4 and P1; pentavalent reassortant vaccine). Control mice were inoculated with a placebo. At 6 days post-inoculation (p.i.), 8 of 13 (62 %; P<0.005) Rotashield-inoculated mice developed hepatitis and/or bile-duct obstruction compared with none of 11 mice given WC3-PV and none of 14 given placebo. In the Rotashield-inoculated mice, only serotype G3 rhesus rotavirus (RRV) was isolated from multiple sites, including intestine, liver, pancreas, spleen, blood and mesenteric lymph nodes. Recovery of RRV from Rotashield-inoculated mice followed a biphasic pattern. The two peaks of RRV recovery appeared to coincide firstly with replication in the intestine during days 1-3 p.i., and secondly with virus infection of the liver from days 10 to 15 p.i. WC3 reassortants of four different serotypes were detected only at day 1 p.i. in the intestine, liver, pancreas and blood cells from three WC3-PV-inoculated mouse pups. However, WC3-PV did not produce any hepatopathology. Rotashield and WC3-PV appeared to exhibit different biological activity in infant CB17(scid) mouse pups.

Assessment of the epidemic potential of a new strain of rotavirus associated with the novel G9 serotype which caused an outbreak in the United States for the first time in the 1995-1996 season.

Rotavirus causes severe morbidity in developed countries and frequent deaths (> or = 500,000 per year) in less-developed countries. Historically, four serotypes--G1, G2, G3, and G4-have predominated; they are distinguished by one of two surface neutralization antigens (VP7). However, in 1983 and 1984 we described a new rotavirus serotype, designated G9, in five children hospitalized for diarrhea in Philadelphia, Pa. G9 rotavirus was not identified again in the Western Hemisphere until it caused ca. 50% of the rotavirus disease detected in Philadelphia in the 1995-1996 season. This outbreak allowed us to question whether a rotavirus strain completely new to a well-studied community would target either very young infants or older children, cause especially severe disease, or completely displace previously extant serotypes. We observed a significant excess of G9 infections in younger infants (especially in those < 6 months old) that might be attributed to the lack of G9-specific antibodies in mothers. Of further note, six of the seven oldest patients with rotavirus diarrhea were infected with the G9 strains (not significant). However, the age distribution of children with rotavirus did not differ over a 5-year study period regardless of the infecting serotype. Patients with diarrhea associated with G9 strains did not have disease more severe than that caused by the G1, G2, or G3 serotype. G9 strains did not displace the other serotypes but were virtually completely replaced by G1 or G2 serotypes in the three subsequent rotavirus seasons. We conclude that the abrupt appearance of this novel rotavirus serotype did not present a special threat to public health in the community.