Diphtheria: incidence trends and age-wise changes of immunity

Oral vaccination against diphtheria using polyacryl starch microparticles as adjuvant

Oral vaccination offers the advantage of eliciting both a mucosal and a systemic immune response. This study investigated the use of polyacryl starch microparticles as adjuvant for oral vaccination against diphtheria. Diphtheria toxin or cross-reacting material (CRM197) were covalently conjugated to the microparticles and fed to mice by oral gavage. Investigation of formaldehyde treatment as a means of either detoxifying (diphtheria toxin) or stabilising (CRM197) these formulations were also made. We show that all our formulations given orally or parenterally to mice induced a strong systemic immune response. Only formulations given orally induced a mucosal IgA-response. Furthermore, our formulations given parenterally or orally induced a strong diphtheria toxin-neutralising antibody response.

Levels of antibodies specific to tetanus toxoid, Haemophilus influenzae type b, and pneumococcal capsular polysaccharide in healthy children and adults

Antibody levels specific for capsular polysaccharides of Streptococcus pneumoniae and Haemophilus influenzae type b (Hib) and for tetanus toxoid were measured in serum samples of 386 age-stratified subjects. The study group consists of healthy adult blood donors and hospitalized children undergoing elective surgery, excluding individuals with a history of infection. In children, anti-tetanus toxoid antibody levels displayed two peaks of 1.20 IU/ml (20.4 mg/liter) and 1.65 IU/ml (28.1 mg/liter) related to the schedule of routine childhood immunization in the first year and at 8 years of age. Eighty percent of the antibodies are of the immunoglobulin G1 (IgG1) isotype. For pneumococcal capsular polysaccharide (PCP), the specific antibody levels represent the acquisition of natural immunity. The initial concentration of 9.2 mg/liter was low in infancy (0.5 to 1 years of age) and remained low until 3 to 4 years of age (14.6 mg/liter). During this period PCP antibodies were almost 100% of the IgG2 subclass. Thereafter, IgG anti-PCP antibody titers increased steadily to adult levels (59.5 mg/liter). The data are intended to provide reference ranges to aid in the interpretation of specific antibody determinations in the clinical setting.

The immunogenicity and safety of a new combined diphtheria, tetanus and poliomyelitis booster vaccine (Td-eIPV)

In view of the continuing risk of contracting tetanus, diphtheria and poliomyelitis, and the well-documented decline in immunity with time, the need for booster vaccinations is substantial. The immunogenicity and safety of a new combined booster vaccine against tetanus, diphtheria and poliomyelitis (REVAXIS) developed by Pasteur Mérieux Connaught (Lyon, France) were evaluated in four clinical studies. This vaccine (Td-eIPV) combines an adsorbed tetanus toxoid and low-dose diphtheria toxoid vaccine (Td) with an enhanced, inactivated polio vaccine against poliovirus types 1, 2 and 3 (eIPV). In 256 healthy young adults, a single dose of Td-eIPV was shown to be immunogenic, eliciting antibody levels considered protective against disease for each vaccine component in > or = 99.6% of the subjects. In 112 healthy older subjects (> 40 years of age), two doses of Td-eIPV elicited seroprotective levels of antibodies in 94% of the subjects for diphtheria, and in all subjects for tetanus and poliovirus types 1, 2 and 3. Safety data from all 368 subjects, as well as 31 phase I volunteers and 1,742 subjects included in a safety study, reveal that the vaccine is safe. Most reactions were predictable, temporary and mild. There was no evidence that the vaccine was associated with any clinically serious event or modification of clinical laboratory parameters. The data reviewed here show that Td-eIPV is immunogenic and safe when administered as a booster vaccination in healthy adults of all ages.

Specific antibody responses to diphtheria/tetanus revaccination in children evaluated for immunodeficiency

BACKGROUND

Assaying specific antibody levels against well-defined antigens such as diphtheria (D), tetanus (T), and more recently Haemophilus is used as one indicator of humoral immune reactivity when evaluating patients for immunodeficiency. The nature of the response to booster vaccine in this group of patients is not well defined.

OBJECTIVE

To define the response to D/T booster vaccination in patients with nonprotective antibody levels in order to distinguish immunocompetent from immunodeficient children.

METHODS

Patients between the ages of 16 months and 17 years referred for possible immunodeficiency were assessed for specific antibody levels as part of a standard immunologic evaluation. Twenty-six previously immunized patients had antibody titers less than or equal to 0.2 IU against D and/or T or another abnormal vaccine response. All of these patients received boosters of diphtheria and tetanus vaccine (D2T5). Diphtheria and tetanus antibody levels were assayed 4 weeks following booster vaccination.

RESULTS

Of the twenty-six subjects, a subset of patients (6) failed to show significant elevations in specific-serum antibody titers to diphtheria and/or tetanus and were thus labeled nonresponders. These patients were retrospectively compared with their responder counterparts examining specific antibody titers pre-immunization and post-immunization, serum immunoglobulins, and clinical presentation. The groups showed no significant difference in baseline specific antibody measures but following re-immunization responders showed a 31.34-fold and 22.33-fold increase in D and T antibody levels, respectively. In contrast, nonresponders produced only a 2.62-fold to D and 6.15-fold increase to T (all group comparisons P < .05). Clinical presentation also tended to be more severe in the nonresponder group.

CONCLUSIONS

These data stress the importance of specific antibody titers pre-immunization and post-immunization in the assessment of immunodeficiency states, and emphasize the different characteristics of responses between diphtheria and tetanus toxoids. The ability to achieve the minimum protective antibody level does not necessarily denote immune competence. Serum immunoglobulin levels and baseline antibody titers are insufficient for the functional assessment of the immune response. The ability to generate antibody responses following booster vaccination is a more complete measure of overall immune competence and should be considered when evaluating patients for replacement immunoglobulin therapy.

Current trends in bacterial respiratory pathogens

The relationship of virulence and antimicrobial susceptibility with morbidity due to bacterial respiratory pathogens is complex and evolving. Ultimately, decreasing the incidence of pneumonia due to bacterial pathogens will be dependent on successful preparation and distribution of effective vaccines. Until effective vaccines are widely available, control of a majority of respiratory infections will depend on promotion of rational therapeutic strategies. Though limited to a few specific serotypes and strains, changes in virulence of bacterial respiratory pathogens have been noted. Co-infections due to multiple respiratory pathogens may increase morbidity; however, the epidemiology of co-infections is not clear. Relationships between respiratory viruses and bacteria may exist that increase virulence of both agents, but information regarding these relationships awaits further investigation. Resistance of respiratory pathogens to the more commonly used antimicrobials, such as penicillin, erythromycin, chloramphenicol, and cotrimoxazole, is being documented globally with increasing frequency. The evolution of antimicrobic resistance, especially among strains of Streptococcus pneumoniae, the most common and deadly agent of lower respiratory tract infections, provides impetus to develop and promote effective pneumococcal vaccines and to search for new and effective antimicrobials.

Human antibody response to fragments A and B of diphtheria toxin and a synthetic peptide of amino acid residues 141-157 of fragment A

Examination of a selection of serum samples from adults from two regions of England showed that 50% of men in the 16-24 years and over 55 years age groups had high titres of antibody to diphtheria toxin (DT). In contrast, only 11% of women aged 16 to over 55 years had high titres of antibody to DT. All human antisera with high anti-DT titres reacted with a synthetic peptide (SP) corresponding to the amino acids 141-157 of DT fragment A, with sera from men aged 35 to over 55 years showing the highest titres. High antibody titres to fragment A paralleled those to SP in both sexes. Titres of antibody to DT fragment B were highest in individuals with high titres to DT. In sera from both sexes immunoglobulin G1 was the predominant subclass reactive with all three antigens. However, both IgG1 and IgG4 and to a lesser extent IgG2 and IgG3 were present in immunoglobulin concentrates.

Immunity against diphtheria in adults in Poland

The diphtheria immunity status was determined with the passive haemagglutination technique in 503 sera of 10-90-year-old persons from Warsaw and Olsztyn Provinces. Donors of sera were students, teachers, pregnant women, employees of industry and medical service. The immunity was highest (90% of titers 0.1 IU/ml or higher) in persons below 20 years of age and in persons above 60 years of age (55%). Between these two groups, gaps in immunity exist, the proportion of those immune varying from 36-50% in the 20- 60-year-old groups. Since a large pool of susceptible persons creates an epidemic potential it was suggested that the adult type of tetanus-diphtheria toxoid (Td) should be introduced into the routine immunization schedule for high risk groups. These groups might include professional or age groups who are vulnerable to reintroduction of virulent Corynebacterium diphtheriae such as kindergarten and creches personnel, teachers, students, military service personnel and persons travelling to developing countries.