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H Fred Clark

Publications and source records attributed to H Fred Clark.

14 recordsLinked to original sources
PubMed2006

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.

Animals↗
PubMed2006

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.)

Administration, Oral↗
PubMed2006

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.

Animals↗
PubMed2005

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.

Child, Preschool↗
PubMed2005

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).

Amino Acid Sequence↗
PubMed2005

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.

Adult↗
PubMed2004

Rotavirus immunoglobulin a responses stimulated by each of 3 doses of a quadrivalent human/bovine reassortant rotavirus vaccine.

A quadrivalent precursor to the pentavalent rotavirus vaccine candidate RotaTeq was evaluated in a 3-dose, 439-subject study. To determine immunogenicity, the quantity of rotavirus immunoglobulin A (IgA) in stool specimens obtained, at 1 of 10 study sites, from 37 placebo and 37 vaccine recipients was measured. None of the placebo recipients showed a clinically important (>/=3-fold) increase in stool rotavirus IgA, whereas 31 vaccine recipients showed an increase after at least 1 dose of vaccine. In total, 16, 19, and 15 vaccine recipients had increases after 1, 2, and 3 doses, respectively, indicating that a 3-dose regimen increased the immune response elicited by this vaccine.

Animals↗
PubMed2004

Safety, efficacy, and immunogenicity of a live, quadrivalent human-bovine reassortant rotavirus vaccine in healthy infants.

OBJECTIVES: To investigate safety, efficacy, and immunogenicity of live quadrivalent rotavirus vaccine (QRV) containing human-bovine (WC3) reassortant rotavirus serotypes G1, G2, G3, and P1a. STUDY DESIGN: This was a randomized, double-blinded, placebo-controlled trial. During 1993 to 1994, at 10 US study sites, 439 healthy infants approximately 2 to 6 months of age, were enrolled to receive 3 doses of oral QRV or placebo at approximately 8-week intervals. RESULTS: The vaccine was generally well tolerated; no serious vaccine-related adverse experiences were reported. Risk differences and 95% confidence intervals suggested no differences between vaccine and placebo recipients in the incidences of fever, irritability, vomiting, or diarrhea during the 14 days after any dose. QRV was 74.6% efficacious (95% CI: 49.5%, 88.3%) in preventing rotavirus acute gastroenteritis (AGE), regardless of severity and 100% efficacious (95% CI: 43.5%, 100%) in preventing severe rotavirus AGE through one rotavirus season. Serotype G1 was identified in most infants with rotavirus AGE. A >or=3-fold rise in serum neutralizing antibody to G1 was observed in 57% (45/79) of vaccinees. A >or=3-fold rise in serum anti-rotavirus IgA and fecal anti-rotavirus IgA was observed in 88% (162/185) and 65% (104/159) of vaccinees, respectively. CONCLUSIONS: QRV was generally well tolerated, immungenic, and highly effective against rotavirus gastroenteritis.

Animals↗
PubMed2004

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.

Animals↗
PubMed2004

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.

Administration, Oral↗
PubMed2004

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.

Age Distribution↗
PubMed2004

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.

Child Welfare↗
PubMed2003

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.

Chemistry, Pharmaceutical↗