Poor reduction of HIV-1 RNA titres in nucleoside reverse transcriptase inhibitor experienced patients treated with indinavir combination therapy.

OBJECTIVES: The long term effectiveness of combination therapy at reducing viral loads in seminal fluid and blood plasma obtained from HIV-1 infected men who had undergone previous antiretroviral therapy was assessed. METHODS: Samples of semen and blood were obtained from a cohort of 12 nucleoside reverse transcriptase inhibitor experienced men before and during 25-68 weeks of combination therapy, which included the protease inhibitor indinavir. HIV-1 RNA titres present in the cell free blood and seminal plasma samples were determined using the nucleic acid sequence based amplification (NASBA)/Nuclisens assay system. RESULTS: Viral RNA was detected in 9/12 and 7/12 baseline blood plasma and seminal plasma samples, with median viral titres of 10(4.81) and 10(4.56) per ml, respectively. By the end of the study period the detection rates of HIV RNA in the blood and seminal plasma samples were 5/12 and 2/12, respectively, with the median viral titres below the assay cut off level for both sample types. Of the nine patients who had detectable viral RNA in the baseline sample, only three cleared virus from both compartments by the end of the study. CONCLUSIONS: These data show that stable reduction of blood and seminal fluid viral titres is not achievable in a significant proportion of nucleoside reverse transcriptase inhibitor experienced men.

Seroepidemiology of group A rotavirus in suburban São Paulo, Brazil.

Age-specific patterns of rotavirus infection were investigated using a randomly selected and representative sample of sera from a suburban community of São Paulo, Brazil screened for class-specific antibodies to group A rotavirus. Age-serology of anti-rotavirus IgG showed primary infection predominant in young infants with a median age of around 18 months consistent with IgM serology suggesting highest rates of recent infection between ages 4 and 48 months. Anti-rotavirus serum IgA prevalence increased gradually with age. Paired samples from infants, collected 1 month apart, indicated high exposure rates with seroconversion occurring in several infants during the reported low transmission season. Between 5 and 10% of adults had elevated IgM levels indicative of recent infection and, potentially, of an important contribution adults may play to rotavirus transmission. Further understanding of the dynamics of rotavirus transmission within populations, at group and serotype level, would benefit the design and monitoring of future immunization programmes.

Homotypic and heterotypic immune responses to group A rotaviruses in parenterally immunized sheep.

Immune responses to human rotaviruses were investigated in sheep with a view to obtaining antibodies for passive immunotherapy of humans. Eighteen adult sheep with previous natural exposure to rotavirus serotypes G3 and G6 were immunized parenterally with purified preparations of either individual rotavirus serotypes G1, G2, G3, G4 and G8, or a mixture thereof. Two additional sheep were kept as control animals with the flock. The antibody responses were measured on serial serum samples by neutralization tests. The homotypic antibody response ranged from 100-fold (rarely) up to 100,000-fold increases in titre. Heterotypic responses against serotypes G3 and G6 were demonstrated in 7/12 and 15/18 sheep, respectively, but the increases in titre were lower than the homotypic responses, ranging from 10- to 100-fold in most cases and were 1000-fold in two sheep. Interestingly, no heterotypic response against the human rotavirus serotypes was raised after 3 months; moderate titres of cross-neutralizing antibodies for the human serotypes were only observed after a third inoculation.

The pathogenicity of two porcine rotaviruses differing in their in vitro growth characteristics and genes 4.

The pathogenicity of two rotavirus variants, 4F and 4S, obtained following adaptation to cell culture of rotavirus from a diarrhoeic pig in China, was compared by serial passage in 24 gnotobiotic piglets. The rotavirus variants have markedly different growth characteristics in vitro, and their genome profiles differ only in the relative migration of genes 4. Both cell culture-grown variants replicated to an equal extent in gnotobiotic piglets and neither caused disease, although weight gain was slightly affected in piglets inoculated with the 4F variant. During five serial pig-to-pig passages, variant 4F became highly pathogenic at the fourth and fifth passages, causing severe diarrhoea and weight loss, and premature death in two animals. Piglets inoculated with rotavirus variant 4S remained healthy during all passages although weight gain was slightly affected. Mean duration and peak infectivity titres of virus shedding were similar for both variants. Thus, variant 4F, which grew slowly and produced small plaques in vitro and had the faster migrating gene 4, was pathogenic in pigs, whereas variant 4S was apathogenic.

Viral agents associated with infantile gastroenteritis in Nigeria: relative prevalence of adenovirus serotypes 40 and 41, astrovirus, and rotavirus serotypes 1 to 4.

Sixty-six stool specimens from infants with diarrhoea in Nigeria were examined for the presence of viral pathogens. Rotaviruses were found in 25.8% of specimens and astroviruses in 1.5%. Serotypes were determined for 47.1% of the rotavirus positive specimens, all of which were serotype 1. RNA analysis revealed no unusual electrophoretic profiles. No enteric adenoviruses were detected. In contrast, in a parallel study conducted in the UK, rotaviruses (including serotypes 1, 2 and 4) accounted for 21.9% of infections, adenovirus serotypes 40 and 41 13.6%, and astroviruses 4.5%.

Investigation of an outbreak of rotavirus infection in geriatric patients by serotyping and polyacrylamide gel electrophoresis (PAGE).

An outbreak of rotavirus diarrhoea amongst patients on two wards in a geriatric unit was investigated using polyacrylamide gel electrophoresis (PAGE) and serotyping. There had been no contact between the patients on different wards but some interchange of staff had occurred so it was important to exclude the possibility that the rotavirus had been spread by staff. Two strains of rotavirus were shown to be present, one on each ward. Differences in the electropherotypes and serotypes were demonstrated, showing conclusively that transfer of virus between the wards had not occurred. Thus, serotyping and PAGE are of value in the investigation of rotavirus outbreaks in the hospital setting where cross-infection between wards is suspected.

A modified alkaline phosphatase enzyme amplification system and its application in an HIV antigen ELISA.

Alkaline phosphatase amplification systems increase the sensitivity of enzyme-linked immunoassays (ELISAs). Here we describe a modified method by which levamisole is a component of the substrate buffer. This increases sensitivity by reducing the signal from non-specific alkaline phosphatases. The modified procedure was applied to an 'in house' HIV-1 p24 antigen capture assay and was shown to increase the sensitivity 4-fold as compared to the unmodified system. The performance of the modified amplification system is comparable to that of commercially available systems.

Epidemiological survey of human rotavirus serotypes and electropherotypes in young children admitted to two children's hospitals in northeast London from 1984 to 1990.

A retrospective and prospective survey was carried out to determine the relative frequency of rotavirus serotypes infecting children with diarrhea or vomiting or both who were admitted to the Hospitals for Sick Children in London during a 6-year period from 1984 to 1990. The results were compared with data for the same period from a study in Birmingham, United Kingdom. The serotype of rotaviruses infecting 1,019 children was ascertained by enzyme immunoassay with VP7-specific monoclonal antibodies. In London, serotype G1 accounted for 60% of the cases, serotype G4 accounted for 24%, serotype G2 accounted for 11%, G3 accounted for 3%, and coinfections accounted for 2%. Considerable differences in the relative prevalence of serotypes were seen when data from London and Birmingham were compared. A major shift from serotype G1 to G4 was observed in London in the 1989 to 1990 season, and a lesser shift was seen in Birmingham. Examination of the electrophoretic profiles of 611 rotaviruses from London showed that there were at least 108 different profiles. Continuous variation occurred throughout the 6-year period, and the same electropherotype never recurred once it had disappeared from the population. None of the electrophoretic profiles were characteristic of group B or group C rotaviruses. There was no evidence that any strain of rotavirus had become endemic in either of the children's hospitals in London.

Efficacy of two doses of RIT 4237 bovine rotavirus vaccine for prevention of rotavirus diarrhoea.

Candidate oral bovine rotavirus vaccine RIT 4237 or placebo was given to 252 Finnish infants at birth and at 7 months of age. No vaccine-associated reactions were observed. Primary rotavirus ELISA IgM responses were detected in 36% of the infants after the first vaccination; after the second dose 68% of the vaccinees were seropositive for rotavirus ELISA IgG antibody. The infants remained in clinical follow-up over two rotavirus epidemic seasons (total 28 months). Counted from child years in follow-up the overall vaccine protection rate was 43%. The clinical severity of rotavirus episodes was assessed using a numerical score 0-20. Vaccine protection rate for cases with a score greater than or equal to 7 was 57% and for cases with a score greater than or equal to 11 it was 89%. It is concluded that vaccination with a bovine rotavirus vaccine at birth and at 7 months of age, with the second dose given shortly before rotavirus epidemic season, protects infants against moderately severe and severe rotavirus diarrhoea in the first 2 years of life.

Rhesus Rotavirus candidate vaccine. Clinical trial in children vaccinated between 2 and 5 months of age.

Live attenuated oral rhesus Rotavirus candidate vaccine (strain MMU 18006 [lot RRV-1]) was evaluated for immunogenicity, safety, and clinical protection in a double-blind, placebo-controlled trial involving 200 infants aged 2 to 5 months when vaccinated. Vaccine-induced fourfold or greater rise of Rotavirus antibodies was seen in 62% of the infants. Febrile reactions of short duration on days 3 and/or 4 after vaccination occurred in 26% of the vaccine recipients. The clinical follow-up covered two Rotavirus seasons, in which serotypes 1 and 4 were prevalent. There were 16 cases of confirmed Rotavirus diarrhea in the placebo-treated group and 10 in the vaccine-treated group; from this a vaccine protection rate of 38% was derived. Clinical severity of Rotavirus diarrhea was assessed by a score; 13 cases in the placebo-treated group and 5 in the vaccine-treated group were regarded as severe or moderately severe, giving a vaccine protection rate of 67%. The rhesus Rotavirus vaccine induces partial protection against heterotypic Rotavirus disease, but the level of protection achieved with the present vaccine dose in this age group appears to be insufficient for a general Rotavirus vaccination.

Evaluation of RIT 4237 bovine rotavirus vaccine in newborn infants: correlation of vaccine efficacy to season of birth in relation to rotavirus epidemic period.

A single oral dose of bovine rotavirus vaccine RIT 4237 or placebo was given to 2 groups of 5-day-old infants, born in October 1984 (n = 244) and June 1985 (n = 245), who remained in follow-up for 2.8 and 2.0 years, respectively. The vaccine had no effect on the total number of detectable episodes of rotavirus diarrhoea: there were 22 cases in the vaccinees and 24 in the placebo recipients in the October group and 18 and 16 respectively in the June group. However, vaccination decreased significantly the clinical severity of rotavirus diarrhoea, as assessed by a numerical score 0-20; this vaccine effect was much greater in the infants born in October. The mean severity scores for vaccine and placebo recipients were 4.55 and 10.75 respectively in the October group (p less than 0.0001, t-test) and 8.2 and 11.6 respectively in the June group (p = 0.010, t-test). Vaccine-induced clinical protection against rotavirus diarrhoea did not correlate well with serological response after vaccination, but showed good correlation to the presence of rotavirus antibodies before the rotavirus epidemic season. It is concluded that bovine rotavirus vaccine is more efficacious when given immediately before the rotavirus epidemic season: the vaccine effect may be amplified by exposure to wild rotaviruses during the season.

Temporal and geographical distributions of human rotavirus serotypes, 1983 to 1988.

Between 1983 and 1988, subgroups and serotypes were determined for 907 of 1,084 clinical specimens of rotaviruses collected in various countries of Europe, North and South America, Africa, and Asia. Enhanced enzyme immunoassays based on monoclonal antibodies specific for rotavirus proteins VP6 and VP7 were used. Significant differences in the prevalent serotypes were detected from year to year in the United Kingdom and Brazil and also in different countries during the same year. Throughout the study, rotavirus serotype 1 was detected most often (53.8%), followed in frequency by serotype 2 (17.8%), serotype 3 (12.1%), serotype 4 (11.1%), and serotypes other than 1 to 4 (5.1%). No individual serotype was found to predominate consistently in any one location. In the United Kingdom, rotavirus serotypes varied in prevalence in a regular but not predictable way. We suggest that a similar epidemiology might be found in other settings. Seventeen unusual strains were detected. Of these, five strains did not react with reference monoclonal antibodies specific for subgroup I and subgroup II, but they reacted with rotavirus group A-specific polyclonal and monoclonal antibodies; four strains were of subgroup II, serotype 2, and at least one had a "long" electropherotype; two strains were of subgroup I, serotype 2 with a long electropherotype; and one strain was of subgroup I, serotype 3. Five group C rotaviruses were detected.

Determination of rotavirus serotype-specific antibodies in sera by competitive enhanced enzyme immunoassay.

A method is described for the specific detection of antibody to individual rotavirus serotypes in sera. A competitive enzyme immunoassay (EIA) was developed in which rotavirus serotype-specific monoclonal antibodies against VP7 compete with antibodies in test sera for rotavirus serotype-specific antigen bound to a solid phase. There was an excellent correlation between serotype-specific EIA results and serotype-specific neutralization titres (r = 0.915, P = less than 0.001). The value of this method for rotavirus epidemiology and vaccine trials is discussed.

Recent advances in the study of viral gastroenteritis.

Acute infectious gastroenteritis is the commonest cause of death in children under 5 years old who live in developing countries. In developed countries, whilst deaths occur rarely, gastroenteritis remains an important public health problem. Before the early 1970s the cause of the majority of diarrhoeal disease episodes was a mystery. The recognized causes of infectious diarrhoea at the time were bacteria and parasites. During the 1970s a number of previously unknown viruses were discovered and subsequently shown to cause infectious gastroenteritis. Numerous studies which were conducted during the late 1970s and early 1980s confirmed the world-wide significance of these viruses as important pathogens, especially the rotaviruses, which can now be cultivated. Emphasizing recent progress, an overview is given of the virus, its pathogenesis and vaccine strategies for preventing disease. Other viruses, including adenoviruses, caliciviruses and astroviruses, are also described and their significance assessed.

Rotavirus epidemiology in Vellore, south India: group, subgroup, serotype, and electrophoretype.

Rotaviruses were detected in 163 of 916 (17.8%) specimens collected from children under 3 years of age with gastroenteritis in Vellore, South India, between August 1983 and July 1985. Rotaviruses were detected throughout the study period, with a peak prevalence in December to February (winter) and June to August (southwest monsoon season). A total of 117 rotavirus strains were tested for subgroup, serotype, and rotavirus double-stranded RNA electrophoretic migration pattern; 24.8% of the strains were subgroup I, 69.2% were subgroup II, and 6.0% were neither subgroup I nor subgroup II. Subgroup I and II strains were circulating concurrently throughout the study. Of the 117 rotavirus strains, 32 (27.4%) were serotyped; 15 were serotype 1, 3 were serotype 2, 2 were serotype 3, and 12 were serotype 4. Three serotypes were circulating concurrently during the periods of peak rotavirus prevalence. In 100 of the 117 strains (85.4%) an RNA pattern was detected. One unusual subgroup I group A rotavirus with a long migration pattern and four atypical rotaviruses serologically related to group C were also detected.

Subgroups, serotypes, and electrophoretypes of rotavirus isolated from children in Bangui, Central African Republic.

The subgroups and serotypes of 178 strains of rotavirus isolated from diarrheic and healthy children in Bangui, Central African Republic, during a 27-month period were determined by enzyme-linked immunosorbent assay. The subgroup was determined for 152 of the viral strains, 18.4% being subgroup I and 81.6% being subgroup II. Of the 143 strains which could be serotyped, 71.3% were serotype 1, 15.4% were serotype 2, and 13.3% were serotype 3. Serotypes 1 and 3 were detected throughout the study, while serotype 2 was detected only during 8 months. No serotype exhibited any special epidemiological properties. The serotypes were found to consist of three different electrophoretypes, two long ones (A and B) and a short one (C). All subgroup I, serotype 2 strains presented short electrophoretypes. Strains with identical long electrophoretypes A were either serotype 1 or serotype 3.

The antigenic diversity of rotaviruses: significance to epidemiology and vaccine strategies.

Rotaviruses are the major cause of infantile gastroenteritis world-wide. Much antigenic diversity exist amongst them. This has important implications to diagnosis, epidemiology and vaccination strategies. The nature of this diversity is now well understood. This review outlines and discussed our current knowledge of the subject from a historical perspective.