Seronegative Children Research Articles

Comparison of Live Attenuated Cold-Adapted and Avian-Human Influenza A/Bethesda/85 (H3N2) Reassortant Virus Vaccines in Infants and Children

Randomized, placebo-controlled studies with 10(3)-10(7) 50% tissue-culture infectious dose (TCID50) of avian-human (ah) and cold-adapted (ca) influenza A/Bethesda/85 (H3N2) reassortant viruses were completed in 106 seronegative young children 6-48 months of age. Although the reassortants differed in six of eight RNA segments, they exhibited similar properties in level of attenuation, infectivity, immunogenicity, and efficacy. The 50% human infectious dose was 10(4.6) TCID50 for ah and 10(4.4) for ca vaccines. Both reassortants were satisfactorily attenuated with restricted replication and were no more reactogenic than placebo. The mean peak titer of virus shed was 10(1.5) (ah) to 10(2.0) (ca) TCID50/ml, and each of 37 isolates tested retained their characteristic vaccine phenotypes. Infection with ah or ca virus conferred immunity to experimental challenge with homologous virus. These findings indicate that both ah and ca influenza A/Bethesda/85 (H3N2) reassortants should be suitable vaccine candidates for use in healthy infants and young children.

A New Combined Trivalent Live Measles (AIK-C Strain), Mumps (Hoshino Strain), and Rubella (Takahashi Strain) Vaccine

Trivalent virus vaccine, containing measles AIK-C strain, mumps Hoshino strain, and rubella Takahashi strain, was administered to a total of 1369 healthy children, 8 months to 18 years of age. For comparative study, monovalent vaccines of AIK-C strain and Hoshino strain were administered to 147 and 122 initially seronegative children, respectively. The clinical and serological responses following vaccination were analyzed. Among the recipients of the trivalent vaccine, 893 were initially seronegative to all three viruses. Inoculation induced sufficient serological responses: 99.7% for measles and rubella viruses and 96.3% for mumps virus. The incidence of febrile reaction (greater than or equal to 37.5 degrees C axillary temperature) was low, 15.9%, and a temperature of 39.0 degrees C or higher occurred in only 1.3% of the subjects. The seroconversion rate, magnitude of antibody titers, and incidence of clinical reactions following the trivalent vaccination were similar to those occurring after the monovalent measles vaccination.

DNA amplification of HIV-1 in seropositive individuals and in seronegative at-risk individuals

We assessed the HIV-1 status of seropositive and seronegative at-risk individuals by the polymerase chain reaction. Fifty-four out of 55 HIV-1-seropositive samples scored positive. However, HIV-1 proviral DNA was not detected in 16 seronegative homosexuals, 20 seronegative polytransfused haemophiliacs and 20 seronegative thalassaemic children, 20 individuals with isolated and persistent anti-core antibodies and 74 seronegative blood donors. These data indicate that positive HIV-1 DNA is likely to be an exceptional phenomenon in HIV-seronegative people.

Lymphocyte Proliferative Responses to HIV-1 Envelope and Core Antigens by Infected and Uninfected Adults and Children

Lymphocytes derived from children and adults infected with the human immunodeficiency virus (HIV-1), as well as from seronegative children and adults, were tested for their ability to proliferate in response to recombinant HIV envelope (env) and core (cor) peptides. Proliferative responses to env were seen in 9% of control children compared with 27% of infected children (p less than 0.02). There was no difference in the response rates of seropositive and seronegative adults (17% and 16%, respectively). Proliferative responses to cor were seen more frequently in children and adults (22% and 28%, respectively) than their seronegative cohorts (11% and 12%, respectively). Also, the proliferative response to env and cor was seen in 27% and 37%, respectively, of seronegative children who were born to seropositive mothers and then subsequently seroreverted. These results suggest that sensitization to HIV recombinant antigens has resulted in a cell-mediated immune response in some HIV-infected individuals. Furthermore, the significant cell-mediated immune response to these antigens in seroreverting children raises the possibility that they may have been sensitized to this antigen by previous HIV infection.

Detection of HIV RNA by in situ hybridization in peripheral blood mononuclear cells of seronegative children born to HIV-infected mothers

Of 44 children born to human immunodeficiency virus (type 1) (HIV)-infected mothers, 11 have become seronegative. After the loss of maternal antibodies all children were analysed for several immunological functions and virological parameters in order to determine their HIV status. All children to date are clinically healthy and have normal immune functions. HIV-1 was detected by p24 antigen in one child, by in situ hybridization in nine children while viral cultures were all negative. These data suggest that the rate of vertical transmission of HIV-1 may be underestimated if seronegative children are considered to be not infected. They also suggest that molecular biological techniques are more sensitive than HIV antigen assay or viral cultures.

Evaluation in children of cold-adapted influenza B live attenuated intranasal vaccine prepared by reassortment between wild-type B/Ann Arbor/1/86 and cold-adapted B/Leningrad/14/55 viruses

A reassortant cold-adapted (ca) influenza B experimental live attenuated intranasal vaccine was evaluated for safety and immunogenicity in children by means of a blind, placebo controlled study. The vaccine contained the haemagglutinin and neuraminidase genes, and the gene for its non-structural proteins from wild-type (wt) B/Ann Arbor/1/86 virus, the contemporary strain at the time of the study. Other genes were derived from ca B/Leningrad/14/55 virus. No increase in illness rates was seen in the children from ages 3–15 years given vaccine at maximum potency (a one in two dilution of infectious allantoic fluid, having a titre of 10 7.0 EID 50) compared to children given placebo. About 60% of seronegative children, ages 3–7 years, exhibited a detectible antibody response following one dose of intranasal vaccine, with the seroresponse rate rising to > 70% after two doses of vaccine. Immunogenicity was lowest in seropositive children age 8–15 years, reaching a maximum of 36% after two doses. Results indicated that the vaccine was highly attenuated, and probably of adequate immunogenicity for kindergarten age children. The lower immunogenicity in older children suggests the vaccine might be overly attenuated for use in school-age children who are more likely to have a history of prior natural infection with influenza B virus. Further clinical and epidemiological studies of protection are needed to fully assess this.

Evaluation of a reassortant rhesus rotavirus vaccine in young children

A candidate live attenuated rotavirus vaccine representative of serotype 1 was administered orally to 26 children, 14 of whom were undergoing primary exposure to rotavirus. The vaccine was derived by reassortment between rhesus rotavirus strain, MMU 18006, and the human serotype 1 strain Wa. The resultant virus has the gene coding for the major surface glycoprotein VP-7 from the human strain and all other genes from the attenuated rhesus parent which is a serotype 3 strain. Prior natural exposure to rotavirus determined the infectivity and immunogenicity of the vaccine. Only two of 12 seropositive children had evidence of reinfection while all 14 seronegative children were infected. Mild febrile illness was seen in vaccinees, however there was no evidence of gastrointestinal disease. As determined by neutralization of the human strains, the resultant serum antibody was entirely strain specific. However, heterotypic neutralization was seen when the rhesus strains were used, suggesting that neutralizing antibody can be directed to shared components of the donor and reassortant strain presumably VP-4, the other major surface protein.

Rotavirus studies in Indian (Asian) South African infants with acute gastro-enteritis: I. Microbiological and epidemiological aspects

This study, which is the first one documenting rotavirus (RV) diarrhoea in Asian infants in South Africa, describes the virological and epidemiological aspects of this disease in this population. Fifty-five per cent of 1142 hospitalized cases investigated over a 31-month period showed a positive stool ELISA for RV. Most of these children stopped shedding RV by days 4-6 of hospital admission, though prolonged excretion was recorded in some acute cases for up to 13 days. Mixed RV-bacterial infections occurred in 7% of the total gastro-enteritis (GE) patients, while 8.6% had pure bacterial gastro-enteritis. Sixteen per cent of 188 GE patients had serum anti-RV complement-fixing (CF) antibodies on admission. Rotavirus diarrhoea occurred in half of the seropositive infants. Seroconversion occurred in only two-thirds of the initially seronegative children who had RV diarrhoea. In 5.6% of the RV diarrhoea patients the infection was acquired nosocomially whilst in the hospital for other illnesses. The age-groups mainly affected were between 3 and 14 months, with a peak at 9-11 months; 3% of the RVGE patients were neonates. Both the RVGE and the total GE admissions showed well-marked winter peaks, with an inverse relationship between RV prevalence and both temperature and humidity. It is concluded that RV is the most important cause of infantile GE in this population, whereas pure bacterial infections play a relatively minor role. Circulating anti-RV antibodies do not necessarily afford protection against RV diarrhoea, probably owing to serotypic differences.

HIV viral sequences in seronegative people at risk detected by in situ hybridisation and polymerase chain reaction.

A study was conducted to assess the occurrence of latent infection with the human immunodeficiency virus (HIV) among seronegative people at high risk of infection. The presence of HIV genomes was analysed by molecular techniques in two seronegative children born to mothers infected with HIV and in three regular sexual partners of seropositive drug addicts. The adults were selected from a seronegative cohort at high risk of infection because of their sexual contacts and the children selected because of impaired growth. HIV retroviral sequences were detected in four of the five subjects directly at the cellular level by in situ hybridisation in peripheral blood mononuclear cells. HIV genomic sequences were confirmed by in vitro amplification of viral DNA with the polymerase chain reaction technique. The existence of a latent viral infection state in these seronegative subjects indicates the unreliability of standard serological analysis in people who have been in regular contact with infected patients.

Comparison of the immunogenicity of reduced doses of two recombinant dna hepatitis b vaccines in New Zealand children

A group of 201 hepatitis B virus (HBV) sero-negative children 1-12 years of age received either three 2 micrograms doses of Merck Sharp and Dohme (MSD) or Smith Kline and French (SKF) recombinant DNA (rDNA) hepatitis B vaccine I.M. at monthly intervals. Each recipient was tested 4-6 weeks later for antibody to hepatitis B surface antigen (anti-HBs) by enzyme immunoassay (EIA) and radioimmunoassay (RIA). Ninety-six 4-5-year-old children, given 2 micrograms doses of a plasma-derived vaccine (MSD, H-B-Vax) I.M. at 0, 1, 2 months, were tested at the same time with the same assays for comparison. Anti-HBs responses and geometric mean titres (GMT) were significantly higher with the MSDrDNA vaccine (96% and 338.9 IU/liter) than with the SKF/r DNA vaccine (82.3% and 69.4 IU/liter). We conclude that for the protection of young children, 2 micrograms doses of the MSD rDNA hepatitis B vaccine may be used under similar circumstances in which 2 micrograms of the MSD plasma-derived vaccine was used. Further studies are needed before the other rDNA hepatitis B vaccine may be used in lower than the 10 micrograms dose recommended in children.

Clinical features of paediatric AIDS in Uganda

A total of 177 children seen at two hospitals in Kampala are described who were strongly suspected of having acquired immunodeficiency syndrome (AIDS), either on clinical grounds or because they fulfilled the World Health Organization (WHO) case-definition criteria for diagnosis of paediatric AIDS. Blood was taken from the 177 children and 154 of their mothers and tested for antibody to human immunodeficiency virus (HIV) by an enzyme-linked immunoassay (ELISA). Altogether, 119 (67%) children were seropositive, but only 85 (71%) fulfilled the WHO case-definition criteria, and they were significantly older than the 34 who did not fulfil the criteria. A further 58 children were seronegative but fulfilled the WHO criteria. Of the 119 seropositive children, only 3 had a history of previous blood transfusion, but 103 (98%) of 105 mothers were HIV seropositive: consequently, their children were considered to have been infected in utero or perinatally. Thirteen (26%) of 49 mothers of seronegative children were seropositive. Eighty per cent of HIV-infected children were under 2 years of age at diagnosis and 23% died within 3 months of diagnosis. None of the parents was known to be an intravenous drug user, a prostitute or bisexual. The difficulty of accurate diagnosis of AIDS presents a major problem in Africa, as the WHO clinical case-definition criteria alone are clearly not adequate.

Excessive Attenuation of Measles Virus as a Possible Cause of Failure in Measles Immunization

Summary In order to evaluate the effectiveness of 3 further attenuated measles vaccines, i.e. AIK-HDC, heat-treated AIK-HDC andEdmonston-Zagreb-HDC, they were injected into 743 seronegative children aged 7–72 months. Statistically significant reductions in the seroconversion rates were recorded for heat-treated AIK-HDC as well as for Edmonston-Zagreb-HDC vaccine. Seroconversion rates in all 3 groups of vaccinees were lower for children 7–11 months old. The difference in immunogenicity is attributed to the lower antigenicity of measles viruses treated by heat or successive passages.

Sporozoite antibodies and malaria in children in a rural area of The Gambia.

Sporozoite antibody levels were measured in a group of children aged one to nine years resident in a rural area of The Gambia, using an ELISA to the repeat peptide (NANP)40. The prevalence and titre of antibodies varied with age but not with sex or ethnic group. Significant variations in prevalence were recorded within a group of adjacent villages. Children who were seropositive at the beginning of the dry season had higher spleen and parasite rates both at this time and at the end of the subsequent rainy season than did seronegative children, suggesting that they were exposed more frequently to infection. However, seropositive children had fewer episodes of fever accompanied by high levels of parasitaemia than did seronegative children, suggesting that they had a greater degree of clinical immunity. No differences were found in seroprevalence rates or in mean antibody titres between children who slept under conventional or Permethrin treated bed nets and those who did not, even though bed nets significantly reduced the number of bites by vector mosquitoes.

Study of combined vaccination against yellow fever and measles in infants from six to nine months

A study has been carried out in the Ivory Coast to assess the efficacy of a combined vaccine against yellow fever and measles relative to that of each vaccine administered separately. Healthy children aged six to nine months were recruited and divided into two age groups: less than seven months (group I) and more than eight months (group II). In each group, they were randomly assigned to receive either yellow fever vaccine only (A), measles vaccine only (B), or the combined vaccine (C). The serological responses to measles and yellow fever were assessed in 219 initially seronegative children 45 days after immunization. More than 90% of the children developed yellow fever haemagglutination inhibiting antibodies. Neither age nor combination with measles vaccine influenced the responses to yellow fever vaccine. Measles haemagglutinational inhibiting antibodies were found in 97% of the children and the seroconversion rate was influenced neither by age nor by combination with yellow fever vaccine. Younger infants had lower titres of measles antibody. No particular adverse reactions were notified during the follow up. This study shows that combined yellow fever and measles vaccines are immunogenic in infants from the age of six months. Controlling yellow fever in endemic areas and the prevention of measles in young infants may greatly benefit by this combination.

Preventing the Heterosexual Spread of AIDS

To the Editor.— The conclusion reached by Drs Hearst and Hulley 1 that prevention of acquired immunodeficiency syndrome (AIDS) can be accomplished by ensuring that sexual partners are at low risk of human immunodeficiency virus (HIV) infection is consistent with their experience with infected individuals in San Francisco. However, the experience in New York City is very different. One of the first AIDS patients I treated was married to her second husband. After being delivered of three seronegative children during her first marriage, her child from this second marriage was seropositive. On investigation, her second husband was found to be a former intravenous drug abuser who had stopped using drugs before the couple met. Even with the intimacy of marriage and childbirth, the wife had never ascertained that her husband was at high risk of HIV infection. In socioeconomically disadvantaged areas of New York, high-risk partners are virtually indistinguishable from

DETECTION OF HTV1 DNA IN INFANTS AND CHILDREN BY MEANS OF THE POLYMERASE CHAIN REACTION

The polymerase chain reaction (PCR) assay was used to investigate the possibility of HIV1 DNA detection in uncultured peripheral blood mononuclear cells from newborn infants and children of HIV-infected mothers. HIV1 DNA sequences were detected in mononuclear cells of six of fourteen symptom-free newborn infants of seropositive mothers. Only one of these infants had detectable HIV antigenaemia. In addition, HIV1 DNA was identified in the mononuclear cells of five of ten children (2-5 years old) of infected mothers who had become seronegative 12-15 months after birth; among these, four children had only mild clinical features related to HIV infection, while the other had none. HIV1 DNA was shown in all of eight seropositive children with HIV infection and none of fifteen normal seronegative controls. The PCR assay thus provides an early and direct identification of HIV infection in newborn infants and seronegative children born to infected mothers.

Safety of a live-attenuated Japanese encephalitis virus vaccine (SA14-14-2) for children.

In a study begun in 1985, 1,026 children between the ages of 5 and 12 years, living in an area of low Japanese encephalitis (JE) infection, were vaccinated with live-attenuated JE vaccine, strain SA14-14-2. A group of 47 of the vaccinated children, 5-6 years of age, were examined for fever and other systemic reactions every other day for 2 weeks following vaccination. None of these children had temperatures greater than 37.4 degrees C or other systemic reactions during the observation period. No untoward reactions were reported in the remainder of the vaccinated group. After immunization, seroconversion rates in seronegative children were 100% (GMT 35.3, n = 11), 100% (GMT 31.7, n = 12), and 83.3% (GMT 23, n = 10) in groups receiving vaccine diluted 1:3, 1:5, and 1:50, respectively. These results indicate that the JE SA14-14-2 live-attenuated vaccine is immunogenic and safe for children.

HIV infection in Zimbabwe.

A total of 188 children with positive serology for HIV were identified during an 18 month period. Two seronegative children with clinical features of AIDS had seropositive mothers. Ten children were asymptomatic on initial testing; one has since died with infection. The commonest presenting features were generalised lymphadenopathy, failure to thrive, chronic diarrhoea, and pneumonia. Thirty four children are known to have died.

Live Attenuated Varicella Vaccine in Healthy 12- to 24-Month-Old Children

We studied live attenuated Oka/Merck varicella vaccine in 147 seronegative children 12 to 24 months of age and their 94 seronegative older siblings 2 to 12 years of age. The vaccine side effects were mild, consisting of a papular rash in 15 of 147 (10.2%) children 12 to 24 months and seven of 94 (7.4%) siblings. In a subset of 12- to 24-month-old children, modified fluorescent antibody test for membrane antigen was not detectable at seven days postimmunization but was detectable in 50% by 14 days and in 100% by 21 days. Within 6 weeks, 96.6% of children 12 to 24 months and 94.7% of siblings seroconverted. The geometric mean titer did not vary with age at immunization. One-year blood samples were obtained from 70 children 12 to 24 months of age who seroconverted; 92.9% retained detectable antibody. The geometric mean titer had decreased from 55.7 to 18.6. Of these 70 children, 34% had been exposed to varicella since immunization, and two cases of varicella were observed in seroconverters. Both cases were mild, with less than 50 vesicles. Oka/Merck varicella vaccine appears to be safe, highly immunogenic, and protective against 96% of exposures to natural varicella during the first year after vaccination in infants. Those cases of varicella that develop in immunized children appear substantially reduced in severity.

Molecular epidemiology of cytomegalovirus: Viral transmission among children attending a day care center, their parents, and caretakers

This 26-month prospective study monitored 104 children from one day care center (DCC), and their families, for cytomegalovirus (CMV) infections. Among the children, 14 different strains of CMV were identified by restriction endonuclease analysis of the viral DNA of isolates. Three of these strains infected 44 DCC children and apparently were transmitted within the DCC environment. Only children younger than 3 years of age acquired the DCC-associated CMV strains. Of 75 seronegative children in this age group, 34 acquired DCC-associated CMV strains, and four were infected with unique strains. Among 23 children older than 3 years of age, none acquired the DCC-associated strains, although six were infected with unique strains. Of 18 seronegative mothers, six acquired CMV infections within 3 to 7 months after their children became infected; the strains were identical to those isolated from their children and were DCC associated. Four fathers, three seropositive mothers, and two caretakers also shed DCC-associated strains of CMV. None of the 31 mothers whose children were not infected shed CMV. There was no apparent CMV-associated morbidity. These results prove the frequent transmission of CMV within the DCC environment and from DCC children to their parents. They further suggest that caretakers do acquire CMV from DCC children.