**2. Assessment of specific antibodies**

The assessment of specific antibodies always needs to take into account:


All this information is essential to determine if the antibody response is normal or abnormal and also to determine if further immunization is likely to increase antibody titers and protection.

Pneumococcal vaccines are an ideal tool to evaluate the ability to produce specific antibodies in response to a known stimulus. All pneumococcal vaccines contain antigens from several serotypes so the immunologic evaluation is not based on a single antibody response. More recently, research has also revealed that these serotypes allow for clear differentiation between antibody responses to conjugate and pure polysaccharide vaccines, a difference that is clinically relevant.

Current recommendations for the use of pneumococcal vaccines are based on the age at which immunization began. Pneumococcal conjugate vaccines (PCV) are recommended for all infants at 2, 4, 6 and 12 months of age. PCV has also been used in children 24 to 59 months of age who are unimmunized, had incomplete vaccination prior to age 24 months, or are at high risk of acquired invasive pneumococcal disease [2].

The pneumococcal polysaccharide vaccine (PPV23) is not recommended for children under 24 months since the responses to polysaccharide antigens is considered absent or ineffective in the first 2 years of life. Pneumococcal polysaccharide vaccines (PPV23) are recommended for in high risk patients over age 5 and for individuals over age 65. [1]

192 Immunodeficiency

infection.

mechanisms.

tested ;

protection.

**2. Assessment of specific antibodies** 

exact record of immunizations;

a difference that is clinically relevant.

The assessment of specific antibodies always needs to take into account:

obtained with the same method used to test the patient sample.

or are at high risk of acquired invasive pneumococcal disease [2].

Other primary immunodeficiency disorders with an immunologic phenotype associated with specific antibody deficiency include Wiskott-Aldrich syndrome, partial DiGeorge syndrome, asplenia, hyper-IgE syndrome, and selective IgA deficiency (without IgG subclass deficiency). [30] In addition, specific antibody deficiency can be identified in some patients with congenital dysmorphic syndromes or chromosomal abnormalities associated with recurrent sinopulmonary infections. Acquired or secondary immunodeficiencies associated with specific antibody deficiency include splenectomy, immunosuppression, chronic lung disease, protein-calorie malnutrition, and human immunodeficiency virus

There is not a single pathogenic mechanism for specific anti-polysaccharide antibody deficiencies. The variable conditions in which an inability to respond to polysaccharides is found suggest that many different immunologic phenotypes may lead to the same clinical phenotypic antibody deficiency. Further defining different SAD phenotypes and relating these phenotypes to associated conditions may shed further insight into possible pathogenic

1. Evidence of exposure to vaccines or infections. In the case of vaccines, this includes an

2. Time since last exposure or vaccination to the time of obtaining the blood sample to be

3. Method of antibody measurement, including the method, the antigen used, the standards used to normalize values and normal values for different age groups

All this information is essential to determine if the antibody response is normal or abnormal and also to determine if further immunization is likely to increase antibody titers and

Pneumococcal vaccines are an ideal tool to evaluate the ability to produce specific antibodies in response to a known stimulus. All pneumococcal vaccines contain antigens from several serotypes so the immunologic evaluation is not based on a single antibody response. More recently, research has also revealed that these serotypes allow for clear differentiation between antibody responses to conjugate and pure polysaccharide vaccines,

Current recommendations for the use of pneumococcal vaccines are based on the age at which immunization began. Pneumococcal conjugate vaccines (PCV) are recommended for all infants at 2, 4, 6 and 12 months of age. PCV has also been used in children 24 to 59 months of age who are unimmunized, had incomplete vaccination prior to age 24 months,


23-PPV: 23-valent polysaccharide vaccine; 7-PCV: heptavalent conjugate vaccine; 13-PCV: 13-valent conjugate vaccine PCV: 13-valent conjugate vaccine. *Courtesy of RU Sorensen, MD.*

**Table 1.** Pneumococcal vaccines and antibody testing for conjugate and pure pneumococcal polysaccharides


Selective Antibody Deficiency with Normal Immunoglobulins 195

Although infections and immunizations elicit IgM, IgA, and IgG antibody responses, only IgG titers are relevant to the assessment of vaccine responses. IgG antibodies confer longterm protection and are considered indicative of immunity. The specific IgG titer represents the total of all IgG subclass concentrations, since most antibody tests do not

For IgG anti-pneumococcal antibody assessment, the standard method is the third generation WHO ELISA, which incorporates double absorption of samples with capsular polysaccharide (CPS) and serotype 22F and correlates closely with OPA measurements [Concepcion 2001]. Multiplex technologies allow simultaneous quantitation of multiple serotype-specific antibodies. There has been limited validation against the established gold standard ELISA and assay performance in the clinical setting has not been carefully

Measurements of antibodies to all 23 pneumococcal serotypes in a single test, without differentiating specific antibodies to single serotypes, is not useful. The correlation of this test with the standard ELISA test is poor. For instance, the presence of a high concentration antibody to a single serotype may give a falsely high antibody concentration, though the

Ideally, evaluation of antibody-mediated immunity includes the measurement of immunoglobulin and pre-immunization anti-pneumococcal antibody concentrations, with follow-up assessment of post immunization antibodies four to six weeks later. In practice today, most patients needing evaluation for recurrent infections have already received one or more pneumococcal vaccines and pre-immunization antibody concentrations cannot be measured. So, an exact immunization history becomes essential for the adequate

When there is a good initial clinical and serological response to vaccination but clinical infections recur after a period of time, usually 6 to 12 months, the antibody evaluation is repeated to rule out a rapid loss of antibody concentration down to non-protective

In most cases, evaluation of specific antibody deficiency is based on the response to pneumococcal polysaccharides. In some circumstances, it is also important to consider the response to other vaccines or infections. In patients with hypogammaglobulinemia in the first year of life, the response to protein antigens such as tetanus and diphtheria toxoids may help to predict whether the patients has transient hypogammaglobulinemia of infancy, and whether the low IgG concentrations will spontaneously increase into the normal range. The present role of the response to the conjugate *Hemophilus influenzae* type b vaccine has not

The measurement of anti-A and B isoagglutinins is not useful in the diagnosis of specific antibody deficiency. Blood groups A and B are galactosamines on red blood cells that crossreact with galactosamines on the capsule of gut E coli bacteria. The method currently in use

differentiate among Ig subclasses.

antibody response to other serotypes may be deficient.

examined.

interpretation of results [43].

concentrations.

been well defined.

The measurement of pre-immunization immunoglobulin and serotype-specific antibody concentrations, as well as 4 to-6-week post immunization serotype-specific antibody concentrations are recommended.

\* Recommendations for the use of CV are based upon the recommendations of the CDC Advisory Committee (press release 10/22/99), FDA (HHS News release 2/17/00) and of the American Council on Immunization Practices [4].

• Intervals between doses of any vaccine combination should be ≥ 2 months.

∆ One study showed excellent serological responses to 22 of the 23 serotypes in the PV vaccine in 56 12-month old children. [7] These results support personal observations (Sorensen RU) of good responses to PV in younger children. The use of PV in patients 12-24 months of age could be considered when CVs are not available.

◊ Patients with IgG2 deficiency may require 2 doses at any age [62].

§ If there is no antibody response to PV, give CV; repeating PV is not effective [55].

*Adapted from: Sorensen RU, Moore C. Peds Clin N A 2000;42:1225.* 

**Table 2.** Pneumococcal immunization in patients with recurrent infections


A protective antibody concentration is defined as ≥1.3 micrograms/mL, based on response to polysaccharide vaccine serotypes in patients >2 years of age.

If a patient previously received the conjugate pneumococcal vaccine and had protective titers to those serotypes, then an adequate response would be expected to the age-appropriate percentage (50% or 70%) of those serotypes exclusive to the polysaccharide vaccine.

%: percent of polysaccharide vaccine serotypes administered and tested.

*Adapted from Sorensen, RU, Moore, C. Peds Clin N A 2000;43:1225.*

**Table 3.** Classification of deficient response to pneumococcal vaccination

#### **3. Measurement of specific antibody responses**

Various methods for the measurement of antigen-specific antibodies include nephelometry, turbidimetry, chemiluminescence and enzyme-linked assay (ELISA) . Although infections and immunizations elicit IgM, IgA, and IgG antibody responses, only IgG titers are relevant to the assessment of vaccine responses. IgG antibodies confer longterm protection and are considered indicative of immunity. The specific IgG titer represents the total of all IgG subclass concentrations, since most antibody tests do not differentiate among Ig subclasses.

194 Immunodeficiency

Vaccine

Normal infants 2, 4, 6, 12-15 months Not given to patients this age 7 to 11 months 3 doses• Not given to patients this age

12 to 23 months 2 doses Not given to patients this age

The measurement of pre-immunization immunoglobulin and serotype-specific antibody concentrations, as well as 4 -

\* Recommendations for the use of CV are based upon the recommendations of the CDC Advisory Committee (press release 10/22/99), FDA (HHS News release 2/17/00) and of the American Council on Immunization Practices [4].

∆ One study showed excellent serological responses to 22 of the 23 serotypes in the PV vaccine in 56 12-month old children. [7] These results support personal observations (Sorensen RU) of good responses to PV in younger children.

> IgG anti-pneumococcal antibodies Post-immunization

> > any serotype

of serotypes administered

A protective antibody concentration is defined as ≥1.3 micrograms/mL, based on response to polysaccharide vaccine

If a patient previously received the conjugate pneumococcal vaccine and had protective titers to those serotypes, then an adequate response would be expected to the age-appropriate percentage (50% or 70%) of those serotypes exclusive

Various methods for the measurement of antigen-specific antibodies include nephelometry, turbidimetry, chemiluminescence and enzyme-linked assay (ELISA) .

2 to 5 years 1 dose◊ 1 dose >5 years 1 dose §

to-6-week post immunization serotype-specific antibody concentrations are recommended.

The use of PV in patients 12-24 months of age could be considered when CVs are not available.

• Intervals between doses of any vaccine combination should be ≥ 2 months.

§ If there is no antibody response to PV, give CV; repeating PV is not effective [55].

**Table 2.** Pneumococcal immunization in patients with recurrent infections

Severe No protective antibody levels for

Moderate Protective antibody levels for <50%

%: percent of polysaccharide vaccine serotypes administered and tested. *Adapted from Sorensen, RU, Moore, C. Peds Clin N A 2000;43:1225.*

**3. Measurement of specific antibody responses** 

**Table 3.** Classification of deficient response to pneumococcal vaccination

◊ Patients with IgG2 deficiency may require 2 doses at any age [62].

*Adapted from: Sorensen RU, Moore C. Peds Clin N A 2000;42:1225.* 

Severity of deficiency

serotypes in patients >2 years of age.

to the polysaccharide vaccine.

Conjugate (CV)\* Polysaccharide (PV)

∆

2-5 years of age ≥6 years of age

No protective antibody levels for any serotype

Protective antibody levels for <70% of serotypes administered

For IgG anti-pneumococcal antibody assessment, the standard method is the third generation WHO ELISA, which incorporates double absorption of samples with capsular polysaccharide (CPS) and serotype 22F and correlates closely with OPA measurements [Concepcion 2001]. Multiplex technologies allow simultaneous quantitation of multiple serotype-specific antibodies. There has been limited validation against the established gold standard ELISA and assay performance in the clinical setting has not been carefully examined.

Measurements of antibodies to all 23 pneumococcal serotypes in a single test, without differentiating specific antibodies to single serotypes, is not useful. The correlation of this test with the standard ELISA test is poor. For instance, the presence of a high concentration antibody to a single serotype may give a falsely high antibody concentration, though the antibody response to other serotypes may be deficient.

Ideally, evaluation of antibody-mediated immunity includes the measurement of immunoglobulin and pre-immunization anti-pneumococcal antibody concentrations, with follow-up assessment of post immunization antibodies four to six weeks later. In practice today, most patients needing evaluation for recurrent infections have already received one or more pneumococcal vaccines and pre-immunization antibody concentrations cannot be measured. So, an exact immunization history becomes essential for the adequate interpretation of results [43].

When there is a good initial clinical and serological response to vaccination but clinical infections recur after a period of time, usually 6 to 12 months, the antibody evaluation is repeated to rule out a rapid loss of antibody concentration down to non-protective concentrations.

In most cases, evaluation of specific antibody deficiency is based on the response to pneumococcal polysaccharides. In some circumstances, it is also important to consider the response to other vaccines or infections. In patients with hypogammaglobulinemia in the first year of life, the response to protein antigens such as tetanus and diphtheria toxoids may help to predict whether the patients has transient hypogammaglobulinemia of infancy, and whether the low IgG concentrations will spontaneously increase into the normal range. The present role of the response to the conjugate *Hemophilus influenzae* type b vaccine has not been well defined.

The measurement of anti-A and B isoagglutinins is not useful in the diagnosis of specific antibody deficiency. Blood groups A and B are galactosamines on red blood cells that crossreact with galactosamines on the capsule of gut E coli bacteria. The method currently in use

does not differentiate between IgM and IgG responses so is not clinical useful except for in rare instances, such as suspected Wiskott-Aldrich syndrome that needs evaluation in the first year of life. A normal child should have detectable isogglutinin titers after age 6 months.

Selective Antibody Deficiency with Normal Immunoglobulins 197

Normal children between two and five years of age are expected to have an adequate response to >50 percent of serotypes evaluated. Older patients are expected to respond to >70 percent of serotypes evaluated. These criteria have not been tested critically; however, they have allowed us to predict a clinical course and decide upon treatment options in over 1000 patients of all ages tested since 1995 (Sorensen et al, unpublished

Other factors that affect pneumococcal antibody concentrations in the evaluation of SAD include treatment with intravenous or subcutaneous gammaglobulin within the previous 6 months and underlying diseases and/or treatments possibly affecting immune response.

In addition to immunization, responses to natural, often subclinical, infection influence the antibody concentrations in patients. In fact, absent protective antibodies in unimmunized patients above 2 years of age are unusual. However, upon vaccination, older patients who never developed protective antibodies to pneumococcal serotypes often have adequate response to most serotypes. Low antibody concentrations in an unimmunized individual do not define an immunodeficiency syndrome unless there is inadequate response to

The clinical manifestations of patients with selective anti-polysaccharide antibody deficiency are similar to those of all antibody deficiency syndromes. The majority of patients have recurrent upper and/or lower respiratory infections such as sinusitis, otitis, bronchitis or pneumonia due to *Streptococcus pneumoniae, Haemophilus influenzae, Branhamella catarrhalis, or* 

The sinopulmonary infections must be more frequent or severe that normally expected for the age group of the patient. Most of these infections require antibiotic treatment for clinical improvement, and an evaluation is warranted when multiple antibiotic treatments are

For a common infection such as otitis media, characteristics frequently found in patients

Very few patients with specific antibody deficiency also present with atopic diseases, including atopic dermatitis and asthma, complicated by recurrent infections

needed, even when antibiotics effectively resolve each infection.

• Early onset of infections, as early as 3-4 months of age • Recurrence of infection after antibiotic treatment • Infectious complications such as mastoiditis

• Association with invasive infections

• Clinical change to sinusitis after ear tubes

• Recurrence after ear tubes • Repeated ear tube placement

Examples include long-term steroid therapy, malignancy, and chemotherapy.

observations).

immunization.

*Staphylococcus aureus.* 

with SAD include:

**5. Clinical manifestations** 

In patients with persistent or recurrent infections with a single pathogen, such as varicella, shingles, or a specific hepatitis, assessing the specific antibody response to a causative pathogen may be clinically relevant. However, such evaluations are usually not part of the evaluation for SAD.
