Guillermo M. Ruiz-Palacios

Rotavirus Infection in Infants as Protection against Subsequent Infections

BACKGROUND Rotavirus is the leading cause of severe diarrhea in infants. To provide a base line for assessing the efficacy of rotavirus vaccines, we evaluated the protection that is conferred by natural rotavirus infection. METHODS We monitored 200 Mexican infants from birth to two years of age by weekly home visits and stool collections. A physician assessed the severity of any episodes of diarrhea and collected additional stool specimens for testing by enzyme immunoassay and typing of strains. Serum collected during the first week of life and every four months thereafter was tested for antirotavirus IgA and IgG. RESULTS A total of 316 rotavirus infections were detected on the basis of the fecal excretion of virus (56 percent) or a serologic response (77 percent), of which 52 percent were first and 48 percent repeated infections. Children with one, two, or three previous infections had progressively lower risks of both subsequent rotavirus infection (adjusted relative risk, 0.62, 0.40, and 0.34, respectively) and diarrhea (adjusted relative risk, 0.23, 0.17, and 0.08) than children who had no previous infections. No child had moderate-to-severe diarrhea after two infections, whether symptomatic or asymptomatic. Subsequent infections were significantly less severe than first infections (P=0.024), and second infections were more likely to be caused by another G type (P=0.054). CONCLUSION In infants, natural rotavirus infection confers protection against subsequent infection. This protection increases with each new infection and reduces the severity of the diarrhea.

Efficacy of home-based peer counselling to promote exclusive breastfeeding: a randomised controlled trial.

BACKGROUND Exclusive breastfeeding is recommended worldwide but not commonly practised. We undertook a randomised controlled study of the efficacy of home-based peer counselling to increase the proportion of exclusive breastfeeding among mothers and infants residing in periurban Mexico City. METHODS Two intervention groups with different counselling frequencies, six visits (44) and three visits (52), were compared with a control group (34) that had no intervention. From March, 1995, to September, 1996, 170 pregnant women were identified by census and invited to participate in the study. Home visits were made during pregnancy and early post partum by peer counsellors recruited from the same community and trained by La Leche League. Data were collected by independent interview. Exclusive breastfeeding was defined by WHO criteria. FINDINGS 130 women participated in the study. Only 12 women refused participation. Study groups did not differ in baseline factors. At 3 months post partum, exclusive breastfeeding was practised by 67% of six-visit, 50% of three-visit, and 12% of control mothers (intervention groups vs controls, p<0.001; six-visit vs three-visit, p=0.02). Duration of breastfeeding was significantly (p=0.02) longer in intervention groups than in controls, and fewer intervention than control infants had an episode of diarrhoea (12% vs 26%, p=0.03). INTERPRETATION This is the first reported community-based randomised trial of breastfeeding promotion. Early and repeated contact with peer counsellors was associated with a significant increase in breastfeeding exclusivity and duration. The two-fold decrease in diarrhoea demonstrates the importance of breastfeeding promotion to infant health.

Efficacy and safety of an oral live attenuated human rotavirus vaccine against rotavirus gastroenteritis during the first 2 years of life in Latin American infants: a randomised, double-blind, placebo-controlled phase III study

Zambia has a population of approximately 12 million. According to estimates from the 2001-2002 Zambia Demographic and Health Survey1 between 1997 and 2001 the rate of neonatal mortality was 37/1000 births the infant mortality rate was 95/1000 births and the maternal mortality ratio was 729/100 000 live births. In order to protect mothers and their newborn babies against tetanus WHO recommends that tetanus toxoid (TT) vaccine be given to all pregnant women; Zambia follows WHOs recommendations. In 2006 79% of all pregnant women received a protective dose of TT vaccine. A total of 60% of all deliveries took place in hygienic conditions (administrative data). WHO and UNICEF estimate that in 2006 90% of births were protected against tetanus. (excerpt)BACKGROUND Peak incidence of rotavirus gastroenteritis is seen in infants between 6 and 24 months of age. We therefore aimed to assess the 2-year efficacy and safety of an oral live attenuated human rotavirus vaccine for prevention of severe gastroenteritis in infants. METHODS 15 183 healthy infants aged 6-13 weeks from ten Latin American countries randomly assigned in a 1 to 1 ratio to receive two oral doses of RIX4414 or placebo at about 2 and 4 months of age in a double-blind, placebo-controlled phase III study were followed up until about 2 years of age. Primary endpoint was vaccine efficacy from 2 weeks after dose two until 1 year of age. Treatment allocation was concealed from investigators and parents of participating infants. Efficacy follow-up for gastroenteritis episodes was undertaken from 2 weeks after dose two until about 2 years of age. Analysis was according to protocol. This study is registered with ClinicalTrials.gov, number NCT00140673 (eTrack444563-023). FINDINGS 897 infants were excluded from the according-to-protocol analysis. Fewer cases (p<0.0001) of severe rotavirus gastroenteritis were recorded for the combined 2-year period in the RIX4414 group (32 [0.4%] of 7205; 95% CI 0.3-0.6) than in the placebo group (161 [2.3%] of 7081; 1.9-2.6), resulting in a vaccine efficacy of 80.5% (71.3-87.1) to 82.1% (64.6-91.9) against wild-type G1, 77.5% (64.7-86.2) against pooled non-G1 strains, and 80.5% (67.9-88.8) against pooled non-G1 P[8] strains. Vaccine efficacy for hospital admission for rotavirus gastroenteritis was 83.0% (73.1-89.7) and for admission for diarrhoea of any cause was 39.3% (29.1-48.1). No cases of intussusception were reported during the second year of follow-up. INTERPRETATION Two doses of RIX4414 were effective against severe rotavirus gastroenteritis during the first 2 years of life in a Latin American setting. Inclusion of RIX4414 in routine paediatric immunisations should reduce the burden of rotavirus gastroenteritis worldwide.

Role of human-milk lactadherin in protectoin against symptomatic rotavirus infection

BACKGROUND Human milk contains a 46 kDa mucin-associated glycoprotein, lactadherin, which binds specifically to rotavirus and inhibits its replication. This study tested the hypothesis that lactadherin protects against symptoms of rotavirus infection. METHODS 200 infants in Mexico City were recruited at birth and monitored by regular stool EIA for rotavirus, serology, and recording of feeding and stool patterns. Milk samples were obtained from the mothers weekly until 4 weeks post partum then monthly. The sample taken immediately before an infants episode of rotavirus infection was assayed for lactadherin, butyrophilin, mucin, and secretory IgA. An infection was defined as symptomatic if diarrhoea occurred in the 5 days before or after detection of the virus. FINDINGS 31 infants developed rotavirus infection; 15 were symptomatic and 16 had no symptoms. The median concentration of lactadherin in the milk samples (obtained 4-41 days [median 13] before the infection) was 48.4 (range 5.6-180) microg/mL in the asymptomatic group and 29-2 (6.2-103-4) microg/mL in the symptomatic group. Although these medians did not differ significantly, in logistic regression analysis adjusted for age at infection and secretory IgA concentration there was a significant difference between the groups (p=0O01). No association between symptom status and concentrations of butyrophilin, mucin, or secretory IgA was found. INTERPRETATION Protection against rotavirus by human milk is associated with the glycoprotein lactadherin. This association is independent of products of the secretory immune system.

Genetic diversity among sapoviruses

Summary.Norovirus and Sapovirus are two genera of the family Caliciviridae that contain viruses that can cause acute gastroenteritis in humans. Noroviruses (NOR) are genetically highly diverse but limited studies of the genetic diversity of sapoviruses (SAP) have been reported. In this study we characterized twenty-five SAP detected in our laboratory from outbreaks or sporadic cases of acute gastroenteritis in children from different geographical locations and in adults involved in a cruise ship outbreak investigation and a nursing home outbreak. Based on significant differences of partial RNA polymerase sequences (278–286 nt), the 25 strains were grouped into 12 genetic clusters, including 9 potential new clusters. Extended sequence analysis of the capsid gene of selected strains representing five potential new clusters supported this grouping. Four strains (Hou7-1181/90, Mex340/90, Cruise ship/00 and Argentina39) had <84% amino acid (aa) identity to each other and to the published sequences in the GenBank. Mex14917/00 was almost identical to Stockholm/97/SE whose RNA polymerase sequence was unknown. Phylogenetic and distance analyses of the capsid region of the four new strains showed that Hou7-1181/90 and Argentina39 represent two new genogroups and Mex340/90 and Cruise ship/00 belong to two new clusters within the London/92 genogroup. Thus, based on the capsid sequences we propose to classify the currently known SAP into nine genetic clusters within five genogroups, including one genogroup that is represented by an animal calicivirus, the porcine enteric calicivirus (PEC).

The changing epidemiology of astrovirus-associated gastroenteritis: a review

Our understanding of the epidemiology of astrovirus-associated gastroenteritis has changed markedly with each improvement in detection method. In early surveys based on electronmicroscopy (EM), astroviruses appeared to be a rare cause of gastroenteritis, being found in fewer than 1% of children with diarrhea, usually in small outbreaks of disease and primarily during the winter season. The development and use of monoclonal antibodies and enzyme immunoassays (EIA) to detect astroviruses led to reports of a higher prevalence (2.5%-9%) of astrovirus infection among patients hospitalized with diarrhea. Astroviruses appeared second only to rotaviruses as a cause of hospitalization for childhood viral gastroenteritis. Studies based on EIA detection of astroviruses indicate that astroviruses are common causes of diarrhea in children worldwide, and that most children are infected during their first two years of life. The elderly and the immunocompromised represent high-risk groups as well. The observations that newborns monitored prospectively rarely have repeat disease and that the rate of detection decreases with increasing age suggest that immunity to astroviruses, as immunity to rotaviruses, may develop early in life. The cloning and sequencing of astroviruses have led to more sensitive assays to detect the viruses by reverse transcription, polymerase chain reaction (RT-PCR). Application of RT-PCR for detection of astroviruses in children in day-care centers showed a marked increase in the detected prevalence of astrovirus-associated diarrhea, the rate of asymptomatic infection, and the duration of shedding of virus among those infected, when compared with studies that used other methods. As with rotaviruses, neither the mode of transmission nor the reservoir of astrovirus infection has been identified. Both immune and molecular-based assays to detect astrovirus serotypes indicate that serotype 1 is most common worldwide, although the predominant serotypes may vary by region and time. In the absence of obvious strategies to prevent astrovirus-associated diarrhea, vaccines might be considered if further studies establish that the disease burden would render such a vaccine cost-effective.

Serum Antibody as a Marker of Protection against Natural Rotavirus Infection and Disease

To determine whether naturally acquired serum IgA and IgG antibodies were associated with protection against rotavirus infection and illness, a cohort of 200 Mexican infants was monitored weekly for rotavirus excretion and diarrhea from birth to age 2 years. Serum samples collected during the first week after birth and every 4 months were tested for anti-rotavirus IgA and IgG. Children with an IgA titer >1:800 had a lower risk of rotavirus infection (adjusted relative risk [aRR], 0.21; P<.001) and diarrhea (aRR, 0. 16; P=.01) and were protected completely against moderate-to-severe diarrhea. However, children with an IgG titer >1:6400 were protected against rotavirus infection (aRR, 0.51; P<.001) but not against rotavirus diarrhea. Protective antibody titers were achieved after 2 consecutive symptomatic or asymptomatic rotavirus infections. These findings indicate that serum anti-rotavirus antibody, especially IgA, was a marker of protection against rotavirus infection and moderate-to-severe diarrhea.

Protection of breast-fed infants against Campylobacter diarrhea by antibodies in human milk

To investigate the role of breast-feeding in preventing diarrhea caused by Campylobacter jejuni , we followed 98 Mexican children prospectively for 2 years beginning at their birth. Attack rates of diarrhea in children less than 6 months of age who were not fed human milk were 2.3 times greater than those in children of the same age who were fed human milk. Breast-fed children remained free of diarrhea for a longer time than non-breast-fed children ( p C. jejuni for non-breast-fed infants was significantly greater ( p C. jejuni were high in colostrum, decreased during the first month of breast-feeding, and generally persisted throughout lactation. Human milk consumed by children in whom Campylobacter diarrhea developed did not contain secretory IgA antibodies to the glycine acid-extractable common antigen of Campylobacter . This study shows an association between Campylobacter antibodies in human milk and prevention of diarrhea caused by Campylobacter .

Respiratory Syncytial Virus and Other Respiratory Viral Infections in Older Adults With Moderate to Severe Influenza-like Illness

Abstract Background. Few studies have prospectively assessed viral etiologies of acute respiratory infections in community-based elderly individuals. We assessed viral respiratory pathogens in individuals ≥65 years with influenza-like illness (ILI). Methods. Multiplex reverse-transcriptase polymerase chain reaction identified viral pathogens in nasal/throat swabs from 556 episodes of moderate-to-severe ILI, defined as ILI with pneumonia, hospitalization, or maximum daily influenza symptom severity score (ISS) >2. Cases were selected from a randomized trial of an adjuvanted vs nonadjuvanted influenza vaccine conducted in elderly adults from 15 countries. Results. Respiratory syncytial virus (RSV) was detected in 7.4% (41/556) moderate-to-severe ILI episodes in elderly adults. Most (39/41) were single infections. There was a significant association between country and RSV detection (P = .004). RSV prevalence was 7.1% (2/28) in ILI with pneumonia, 12.5% (8/64) in ILI with hospitalization, and 6.7% (32/480) in ILI with maximum ISS > 2. Any virus was detected in 320/556 (57.6%) ILI episodes: influenza A (104/556, 18.7%), rhinovirus/enterovirus (82/556, 14.7%), coronavirus and human metapneumovirus (each 32/556, 5.6%). Conclusions. This first global study providing data on RSV disease in ≥65 year-olds confirms that RSV is an important respiratory pathogen in the elderly. Preventative measures such as vaccination could decrease severe respiratory illnesses and complications in the elderly.

AS03-adjuvanted versus non-adjuvanted inactivated trivalent influenza vaccine against seasonal influenza in elderly people: a phase 3 randomised trial

BACKGROUND We aimed to compare AS03-adjuvanted inactivated trivalent influenza vaccine (TIV) with non-adjuvanted TIV for seasonal influenza prevention in elderly people. METHODS We did a randomised trial in 15 countries worldwide during the 2008-09 (year 1) and 2009-10 (year 2) influenza seasons. Eligible participants aged at least 65 years who were not in hospital or bedridden and were without acute illness were randomly assigned (1:1) to receive either AS03-adjuvanted TIV or non-adjuvanted TIV. Randomisation was done in an internet-based system, with a blocking scheme and stratification by age (65-74 years and 75 years or older). Participants were scheduled to receive one vaccine in each year, and remained in the same group in years 1 and 2. Unmasked personnel prepared and gave the vaccines, but participants and individuals assessing any study endpoint were masked. The coprimary objectives were to assess the relative efficacy of the vaccines and lot-to-lot consistency of the AS03-adjuvanted TIV (to be reported elsewhere). For the first objective, the primary endpoint was relative efficacy of the vaccines for prevention of influenza A (excluding A H1N1 pdm09) or B, or both, that was confirmed by PCR analysis in year 1 (lower limit of two-sided 95% CI had to be greater than zero to establish superiority). From Nov 15, to April 30, in both years, participants were monitored by telephone or site contact and home visits every week or 2 weeks to identify cases of influenza-like illness. After onset of suspected cases, we obtained nasal and throat swabs to identify influenza RNA with real-time PCR. Efficacy analyses were done per protocol. This trial is registered with ClinicalTrials.gov, number NCT00753272. FINDINGS We enrolled 43 802 participants, of whom 21 893 were assigned to and received the AS03-adjuvanted TIV and 21 802 the non-adjuvanted TIV in year 1. In the year 1 efficacy cohort, fewer participants given AS03-adjuvanted than non-adjuvanted TIV were infected with influenza A or B, or both (274 [1·27%, 95% CI 1·12-1·43] of 21 573 vs 310 [1·44%, 1·29-1·61] of 21 482; relative efficacy 12·11%, 95% CI -3·40 to 25·29; superiority not established). Fewer participants in the year 1 efficacy cohort given AS03-adjuvanted TIV than non-adjuvanted TIV were infected with influenza A (224 [1·04%, 95% CI 0·91-1·18] vs 270 [1·26, 1·11-1·41]; relative efficacy 17·53%, 95% CI 1·55-30·92) and influenza A H3N2 (170 [0·79, 0·67-0·92] vs 205 [0·95, 0·83-1·09]; post-hoc analysis relative efficacy 22·0%, 95% CI 5·68-35·49). INTERPRETATION AS03-adjuvanted TIV has a higher efficacy for prevention of some subtypes of influenza than does a non-adjuvanted TIV. Future influenza vaccine studies in elderly people should be based on subtype or lineage-specific endpoints. FUNDING GlaxoSmithKline Biologicals SA.