Arthur L. Frank

Risk of respiratory syncytial virus infection for infants from low-income families in relationship to age, sex, ethnic group, and maternal antibody level

The risk for hospitalization with respiratory syncytial virus infection during the first year of life was about five per 1,000 live births per year for infants born to low-income families in Houston from 1975 to 1979. The risk varied depending upon the intensity of the epidemic for a given season, the month of birth of the infant, and the level of passively acquired maternal antibody at the time of birth. Over 80% of the children hospitalized were less than 6 months of age; thus, most were born during the six months preceding the peak of RS virus activity. The neutralizing antibody titers in cord sera of 68 infants with culture-proven infections before 6 months of age were significantly lower than those of 575 randomly selected cord samples of infants born during the same period. The level of antibody at the time of birth was directly correlated with age at the time of infection. In addition, infants with more severe illnesses had lower levels of antibody in serum collected near onset of illness than did infants with milder illnesses. These observations demonstrate protection against RS infection in early infancy that is correlated with the level of maternal antibody, but it is not known if this protection is mediated directly by the passively acquired antibody or by some other mechanism.

Acquisition of cytomegalovirus infection from birth to 10 years: A longitudinal serologic study

We performed serial serologic tests for cytomegalovirus (CMV) antibody in 177 children born to low- and middle-income families in Houston from 1975 to 1983. Mean duration of participation in the study was 4.8 years (range 1 to 9.6 years). Most rapid acquisition of antibody occurred during the first and second years of life, 13.6% and 12%, respectively; thereafter, annual acquisition varied from 1.5% to 4.6%, up to 10 years. Overall, 59 (33%) of the group were known to seroconvert by age 10 years. This was a minimal figure because of loss to follow-up. Analysis by the Kaplan-Meier method indicated that the probability of remaining seronegative was 65% at age 6 years, and 58% at age 8 years. Variables positively related to seroconversion by multivariate analysis were order of birth, seroconversion in a family member, and breast-feeding. During the first year of life, acquisition of CMV antibody was related to the seroimmune status of the mother. The variables of socioeconomic status, race, age of the mother, and attendance in a day care center did not appear to be related to seroconversion in these children.

Nasopharyngeal viral isolates in children with Haemophilusinfluenzae type B meningitis

V1Rt;SES have been implicated in the pathogenesis of certain bacterial infections? -3 Influenza and parainfluenza viruses potentiate the action of Haernophilus influenzae type b in experimental animals? In the infant rat model, prior inoculation with influenza virus decreased by 100fold the dose of H. influenzae type b required to produce meningitis in rats without prior viral inoculation? Symptoms and signs consistent with preceding upper respiratory tract infectio n frequently are present in children with bacterial meningitis. We report the results of nasal wash viral cultures in a group of children with meningitis caused by H. influenzae type b.

1011 RISK OF RESPIRATORY SYNCYTIAL (RS) AND PARAINFLUENZA TYPE 3 (PARA3) INFECTION IN YOUNG CHILDREN

Children in the Houston Family Study were followed from birth to determine the occurrence, consequences and immune correlates of infection and reinfection with RS and Para3 viruses. This was a unique study of children living at home; 119 were followed 1 to 5 years-a total of 339 child-years. The RS infection rate was 63 per 100 child-years ranging from about 75/100 during each of the first 2 years of life to about 40/100 for ages 3-5. One-third of infections were clinically apparent. The illness rate was highest during year 2 at 27/100 children, but lower respiratory disease (LRD) was more frequent and severe in the 1st year of life. The LRD rate was 11/100 during the 1st year-2 infants were hospitalized. With primary infection the risk of LRD was 8.6/100 child-years. The overall risk of reinfection LRD was 6.4/100 child-years; however, the rate of reinfection LRD, clinically less severe, was 13/100 during the 2nd year and then dropped sharply for older children. No child had LRD more than 1 time.Infection and illness rates were similar for Para3 but LRD was less frequent. LRD rate was 6.9/100 with primary infection vs. 1.1/100 with reinfection.Risk for both viruses dropped after 2 infections. Thus, multiple live virus immunizations of children > 1 year could provide substantial protection to older children and protect infants by limiting exposure. Boosting maternal immunity may aid protection for early months of life.

1006 INFLUENZA B IN FAMILIES

Characteristics of influenza B were studied in 37 families with 163 members through two outbreaks. By microneutralization, ≥90% of virus positive persons seroconverted if late followup sera were included. Infection rates for B/HK virus in 1977 and B/Singapore in 1980 were highest in school age children (50%, 38%), substantial in 0-4 yr olds (24%, 26%) and lowest in adults (13%, 13%). The rates were about double in each age group in the 14 families infected in 1977 and the 13 infected in 1980.Of 14 families with 1977 infection, only 3(21%) were infected in 1980 compared to 10(43%) of 23 families not infected in 1977. Infection rates for individuals, by age group, were also about double for those not infected in 1977. No infections were observed either year in the 25 persons with preexisting titers >16; the highest infection rate was 36% in those with titers ≤2.Most people with isolates had febrile URI/flu-like illness (69%), 15% had other significant illnesses, and 15% afebrile URI. Most seroconverters had afebrile URI (27%) or were well (39%). Only 1 reinfected child (age 12) shed virus and she had a febrile URI. Up to 4 others (ages 4-8 in 1980) had serological indications of reinfection, without culture verification, and no illness beyond afebrile URI was reported during the 1980 season.Thus, two variants of influenza B gave similar outbreaks in 1977 and 1980 but largely in different families and individuals. This suggests that B/HK infection in 1977 protected against B/Singapore in 1980.

1094 CELLULAR IMMUNE RESPONSES IN FAMILIES WITH INFLUENZA

Cellular and humoral immunologic responses were measured in 39 families, 109 members (72 children) following the 1980 influenza B epidemic. Virologic and/or serologic evidence of recent infection was detected in 19 families (36 children and 17 adults) with information on infection in 1977 available for most. Ficollhypaque separated peripheral blood lymphocytes were obtained on all 109 family members 2-12 weeks post-infection and lymphocyte transformation (LT) studies performed with influenza B antigen. LT responses were seen in 28/36 children and 11/17 adults with recent infection; 9/21 children and 6/22 adults with evidence of remote infection. Thirty-six children (1-5 y.o) have been followed since birth; for 22, this marked their primary infection with influenza B. Significant LT response was seen in 16/22 (3 non-transformers also lacked an antibody response). In 3/16, LT responses were present 4-8 weeks post-infection in the absence of neutralizing antibody (NT). LT was not seen in 15/16 uninfected children. There was a tendency for a linear correlation between LT response and post-influenza NT antibody titer in adults, but no such correlation in children to either pre- or post-infection NT antibody titer.This study demonstrates that primary influenza B infection in young children elicits cellular immune responses equivalent to that of adults. LT responses is higher in recent (73%) as compared to remote (35%) infections and there was no correlation with the NT antibody titer achieved.