Human anti-pneumococcal polysaccharide antibodies are secreted by the CD5- B cell lineage

Shared and unique antibody and B cell profiles in HIV-positive and HIV-negative individuals with cryptococcal meningoencephalitis

Host non-T cell markers to aid in the diagnosis of cryptococcal meningoencephalitis (CM) have not been identified. In this case-control study, we characterized antibody and B cell profiles in HIV-negative and HIV-positive Vietnamese individuals of the Kinh ethnicity recently diagnosed with CM and controls. The study included 60 HIV-negative with no known immunocompromising condition and 60 HIV-positive individuals, with 30 CM cases and 30 controls in each group. Participants were matched by age, sex, HIV serostatus, and CD4 count in the HIV-positive group. Plasma immunoglobulin (Ig) levels, including IgG1, IgG2, IgM, and IgA, Cryptococcus spp. glucuronoxylomannan (GXM)- and laminarin (branched ${\rm{\beta }}$-[1-3]-glucan)-binding IgG, IgM, IgA levels, and peripheral blood B cell subsets were measured. Logistic regression, principal component, and mediation analyses were conducted to assess associations between antibody, B cell levels, and CM. The results showed that GXM-IgG levels were higher and IgG1 and IgG2 were lower in CM cases than controls, regardless of HIV status. In HIV-negative individuals, IgG2 mediated an inverse association between CD19+CD27+CD43+CD5- (B-1b-like) cells and CM. In HIV-positive individuals, lower levels of IgA, laminarin-IgA, and CD19+CD27+IgM+IgD- (IgM+ memory B) cells were each associated with CM. The shared and distinct antibody and B cell profiles identified in HIV-negative and HIV-positive CM cases may inform the identification of non-T-cell markers of CM risk or unsuspected disease, particularly in HIV-negative individuals.

The effect of pneumococcal immunization on total and antigen-specific B cells in patients with severe chronic kidney disease

Background

While the 23-valent pneumococcal polysaccharide vaccine (PPV23) is routinely used in Canada and some other countries to prevent pneumococcal infection in adults with chronic kidney disease (CKD), patients develop a suboptimal antibody response to PPV23 due to their immune dysfunction. The 13-valent pneumococcal conjugate vaccine (PCV13) has superior immunogenicity in some categories of immunocompromised adults; however, its effect on the immune response in CKD patients has only been addressed by two recent studies with conflicting results. The effect of PPV23 or PCV13 on B cells in these patients has not been previously studied. We studied the absolute numbers and proportions of B cells and subpopulations in two groups of adult patients with severe CKD pre- and 7 days post-immunization with PCV13: pneumococcal vaccine naïve and previously immunized with PPV23 (over one year ago).

Results

PPV23 immunized patients had significantly lower proportions and absolute numbers of class switched memory (CD19 + CD27 + IgM-), as well as lower absolute numbers of IgM memory (CD19 + CD27 + IgM+) and class switched B cells (CD19 + CD27-IgM-) compared to PPV23 naïve patients. Following PCV13 immunization, the differences in absolute numbers of B-cell subpopulations between groups remained significant. The PPV23 immunized group had higher proportions of CD5- B cells along with lower proportions and absolute numbers of CD5+ B cells compared to PPV23 naïve patients both pre- and post-immunization with PCV13. However, previous PPV23 immunization did not have a noticeable effect on the numbers of total IgG or serotype 6B and 14 specific antibody-secreting cells detected 7 days post-immunization with PCV13. Nevertheless, fold increase in anti-serotype 14 IgG concentrations 28 days post-PCV13 was greater in PPV23 naïve than in previously immunized patients.

Conclusions

The results suggest that immunization with PPV23 may result in long-term changes in B-cell subpopulations such as increased prevalence of CD5- B cells and decreased prevalence of class switched memory B cells in the peripheral blood. Because previous immunization with PPV23 in patients with CKD is associated with a significant decrease in the total class switched memory B cells in response to subsequent immunization with PCV13, this may reduce PCV13 immunogenicity in the setting of PPV23 followed by PCV13.

Trial registration

Registered February 24, 2015 at ClinicalTrials.gov (NCT 02370069).

Anti-Pneumococcal Capsular Polysaccharide Antibody Response and CD5 B Lymphocyte Subsets

The role of CD19(+) CD5(+) and CD19(+) CD5(-) B cell subpopulations in the antibody response to pneumococcal capsular polysaccharides (caps-PSs) is controversial. In the present study, we evaluated the role of human CD19(+) CD5(+) and CD19(+) CD5(-) cell populations in the serotype-specific antibody response to caps-PS. After vaccination of 5 healthy human adults with Pneumovax (23-valent pneumococcal polysaccharide vaccine [PPV23]), IgG anti-caps-PS serotype 4 antibody-producing cells resided mainly in the CD19(+) CD5(-) B cell subset, as assessed by enzyme-linked immunosorbent spot (ELISpot) analysis. Moreover, in a humanized SCID mouse model, CD19(+) CD5(-) B cells were more effective than CD19(+) CD5(+) cells in producing IgG anti-cap-PS antibodies. Finally, an association was found between the level of IgG anti-caps-PS antibodies and the number of CD19(+) CD5(-) B cells in 33 humans vaccinated with PPV23. Taken together, our data suggest that CD5 defines a functionally distinct population of B cells in humans in the anti-caps-PS immune response.

The effect of combination antiretroviral therapy on CD5 B- cells, B-cell activation and hypergammaglobulinaemia in HIV-1-infected patients

OBJECTIVES

This study assessed B-cell activation, CD5 B-cells and circulating immunoglobulin levels in HIV-infected patients treated with combination antiretroviral therapy (CART).

METHODS

Measurement of plasma immunoglobulin levels and electrophoresis of plasma proteins, and analyses of total numbers of B-cells and B-cells expressing CD 38 and CD5 in whole blood, were undertaken in 47 consecutive HIV-1-infected patients attending an out-patient clinic.

RESULTS

All HIV-infected patients had similar percentages and numbers of B-cells. Proportions of CD5 B-cells in all HIV-infected patients were significantly lower than those in HIV-negative controls. Aviraemic HIV-infected patients on CART had lower percentages of CD5, CD 38 and CD5 CD 38 B-cell subsets and lower plasma levels of immunoglobulin G (IgG) and immunoglobulin A (IgA) than viraemic HIV-infected patients (untreated or on CART). However, 33-37% of aviraemic HIV-infected patients had IgG and IgA levels above the 95th percentile of the normal range defined in HIV-seronegative donors. In aviraemic HIV-infected patients, plasma IgA levels correlated only with proportions of activated (CD 38) B-cells. IgG levels did not correlate with the proportions of B-cell subsets or any marker of HIV disease activity. Monoclonal immunoglobulins were not detected in any plasma sample.

CONCLUSIONS

Aviraemic HIV-infected patients on CART have lower plasma levels of IgG and IgA than viraemic HIV-infected patients, but levels are often above the normal range. CD5 B-cell numbers are depressed, so these cells are unlikely to contribute to hypergammaglobulinaemia in HIV-infected patients.

Pneumococcal vaccination and revaccination of older adults

As individuals advance in age, the risk of infection, bacteremia, and mortality caused by Streptococcus pneumoniae rises. Retrospective data demonstrate that the licensed penumococcal polysaccharide vaccine (PPV) is effective in older persons in reducing serotype-specific invasive disease. PPV demonstrates good immunogenicity in older adults, generally comparable to that in younger subjects, although certain cohorts respond less well. The response to PPV is T cell independent, however, and does not elicit immunologic memory. The duration of the anti-capsular polysaccharide antibody response appears to wane as early as 3 years after vaccination. In older persons, revaccination induces an antibody response, although it may not be as strong as that from the initial vaccine. While revaccination of older adults has been recommended, clinical efficacy has not yet been proven. Measures of antibody function may be at least as important in determining protection as are quantitative antibody levels. Additional studies of immunogenicity, particularly regarding revaccination, will facilitate the design of an optimal pneumococcal vaccination policy. Research into conjugate- and protein-based pneumococcal vaccines, which elicit T-cell-dependent responses and induce immunologic memory, is needed in older persons. In the meantime, administering to PPV to recommended groups should be a public health priority.

Effects of zinc deficiency and pneumococcal surface protein a immunization on zinc status and the risk of severe infection in mice

Streptococcus pneumoniae is a major cause of illness and death in children in developing countries. In these children, zinc deficiency is associated with an increased risk of acute respiratory tract infections, which can be reduced by daily zinc administration. Severe infections decrease zinc levels in plasma and may thereby move individuals with preexisting low zinc stores into a vicious cycle of infection and unavailable zinc. Pneumococcal surface protein A (PspA) has emerged as a promising vaccine candidate, and immunization with this antigen protects animals from pneumococcal infection. In an animal experiment, we measured the effect of zinc depletion on the immune response to parenterally administrated PspA and assessed the effect of this PspA vaccination and zinc depletion on the severity of pneumococcal infection and on zinc status. Mice were kept on different diets for 5 weeks, immunized twice 14 days apart, and challenged intranasally with S. pneumoniae. Mice on the zinc-deficient diet showed substantially reduced immune responses to PspA, more extensive pneumococcal colonization in the nasal mucosa, more severe infections, and an increased risk of death. PspA immunization reduced the risk of severe disease, and the reduction in severity was reflected in substantially reduced zinc depletion from bones.

Evolution of conjugate vaccines

Conjugate vaccines--bacterial polysaccharides conjugated to proteins to improve their immunizing properties--have been a success story since their introduction less than 20 years ago. The Haemophilus influenzae type b conjugate vaccine has nearly eliminated invasive Haemophilus influenzae type b disease in large parts of the world. The key reasons for its success are its ability to induce immunologic memory and reduce asymptomatic carriage, hence the spread of infection. The first pneumococcal conjugate vaccine was licensed in 2000 and is already in wide demand in the USA. The first meningococcal conjugate vaccine was introduced in a nationwide program in the UK in 1999. Current discussion focuses on the efficacy of the conjugate vaccines for different end-points and the cost-effectiveness of their use globally.

Selective antipolysaccharide antibody deficiency associated with peripheral blood CD5+ B-cell predominance

BACKGROUND

Primary humoral deficiencies vary from complete absence of B cells and/or serum immunoglobulin to lacunar deficits involving specific antibody responses to polysaccharides.

OBJECTIVES

We compared the B-cell CD5 expression in patients with selective antipolysaccharide antibody deficiencies (SPADs), common variable immunodeficiency (CVID), and IgG subclass deficiency and in normal control subjects.

METHODS

Five patient populations were evaluated: (1) patients with severe SPAD (no protective serologic postvaccine response to any of 12 polysaccharide antigens tested); (2) patients with intermediate SPAD (diminished response to polysaccharide antigens and adequate response to 1 to 3 of 12 serotypes tested); (3) patients with IgG subclass deficiency; (4) patients with CVID; and (5) age-matched control subjects. Blood was collected from all patients and evaluated by using flow cytometry. Results were compared by using the Student t test.

RESULTS

Patients with severe SPAD deficiencies had a marked predominance of CD5+ B cells in the peripheral blood (93% to 97% of total B cells, n = 2). The intermediate SPAD group had a mean CD5+ B-cell percentage that was significantly higher than that of the age-matched control group (87. 4%, n = 7, vs 52.5%, n = 20; P =.007). Patients with CVID and IgG subclass deficiency had mean CD5+ B-cell percentages that were similar to those of the age-matched control subjects.

CONCLUSIONS

Our studies demonstrate that patients with SPAD had a markedly increased percentage of CD5+ B cells in the peripheral blood as compared with age-matched control subjects and patients with other humoral deficiencies. This observation suggests that an association may be present between CD5+ B-cell predominance and SPAD.

Suppression of T-independent IgM xenoantibody formation by leflunomide during xenografting of hamster hearts in rats

BACKGROUND

It was recently shown that leflunomide (LF) delayed xenoantibody (XAb) formation and xenograft (Xg) rejection in a hamster-to-rat heart transplantation model. Our aim in this study was further investigation of the mechanism of LF-mediated suppression of XAb formation.

METHODS

Hamster hearts were heterotopically transplanted to euthymic or nude rats receiving LF and/or cyclosporine (CsA). Second hamster hearts were transplanted at the time of first Xg rejection. Serum from rejecting rats was transferred to naive rats receiving a hamster heart Xg. The isotype of XAbs was examined by fluorescence-activated cell sorting. Tissue deposition of XAbs and complement was determined by immunofluorescence. XAb formation and its response to LF were also investigated in severe combined immunodeficient mice reconstituted with purified CD5+ or CD5- rat B cells.

RESULTS

After xenografting, untreated PVG rats developed high titers of anti-hamster IgM XAbs that appeared T-independent (T-I) as they could not be suppressed by CsA and also occurred in athymic nude rats. A second Xg transplanted in control or CsA-treated rats rejecting a first Xg was subject to hyperacute rejection. Hyperacute rejection also occurred in naive rats after adoptive transfer of serum from rejecting rats. Monotherapy with LF resulted in a suppression of early IgM XAb formation and in a delay of Xg rejection, which was associated with predominantly IgG anti-hamster XAbs. These XAbs were T-dependent, as they did not occur in nude rats and were suppressed by CsA. CD5+ B lymphocytes appeared to contribute to T-I IgM XAb formation, as LF reduced the percentage of peripheral blood CD5+ B lymphocytes and severe combined immunodeficient mice reconstituted with purified CD5+ B cells, but not with CD5- B cells, produced anti-hamster IgM which were suppressed by LF but not CsA.

CONCLUSIONS

In rats, T-I XAb formation is a first step leading to hamster Xg rejection and is suppressed by LF leading to prolonged Xg survival.

How adaptive antibodies facilitate the evolution of natural antibodies

It is shown how Ig specificities, randomly generated in conventional B cells, come to be expressed in the genetically-determinate B1 population. Thus the adaptive antibody population facilitates the evolution of the natural antibody repertoire, in accordance with the Baldwin effect in the evolution of instinct. The evolution of these two populations is discussed under both the 'proximal usage' and 'preferential expression' hypotheses of biased Ig gene segment usage. This process is independent of theories of B1 function.

Cytokines as adjuvants for vaccines: antigen-specific responses differ from polyclonal responses

The use of cytokines in the administration of vaccines has a unique value in obtaining the appropriate immune response and in ensuring a protective outcome. Earlier studies indicating that cytokines can influence the generation of a particular antibody isotype may represent an oversimplification of a more complex problem. Several studies discussed in this review show that the effect of a given cytokine on the immune response depends on whether one examines the antigen-specific response or the polyclonal response (i.e., total serum immunoglobulins). Further, a balanced regulation of immune responsiveness is important in maintaining homeostasis of the immune system. Consequently, for any vaccine that uses cytokines to boost the response, due consideration must be given to these important variables.

Recurrent pneumococcal meningitis in a patient with transient IgG subclass deficiency

We report the case of a 3 year old boy who exhibited recurrent serious infections with a transient imbalance of IgG subclass in the second year of life. He suffered from pneumococcal meningitis at 3 months, hepatitis at 9 months, and purulent arthritis at 11 months of age. The second episode of pneumococcal meningitis occurred at 14 months. Serum IgG level was normal for age. Low level of IgG2, undetectable level of IgG4 and negligible level of pneumococcus-specific IgG1-G2 antibodies were found. No other primary immunodeficiency was apparent. Serum IgG2-G4 levels but not pneumococcus-specific IgG1-G2 titers increased by the age of 30 months. At that time, he was inoculated with a polyvalent pneumococcal vaccine along with acellular diphtheria-pertussis-tetanus vaccine. He acquired the immunity against these agents, and had no episodic infections in the following 2 years. This observation stresses the existence of transient IgG subclass deficiency associated with delayed development of the anti-polysaccharide antibody response.

Effects of IL-4 depletion on the antibody response to Pseudomonas aeruginosa lipopolysaccharide in mice

These studies were done to examine the role of interleukin-4 (IL-4) in the generation of isotype specific antibody responses of mice to Pseudomonas aeruginosa lipopolysaccharide (PALPS) by neutralization of IL-4 in vivo using anti-IL-4 antibody (11B11). We found that the administration of anti-IL-4 antibody (11B11) 24 h before immunization with PALPS resulted in a decreased PALPS-specific antibody response for all isotypes examined (IgM, IgG1, IgG2a, IgG2b, IgG3). By contrast, we observed that the non-antigen-specific (polyclonal) IgM response of mice following treatment with 11B11 antibody and PALPS was increased while the polyclonal responses for the other isotypes were unaffected. When mice were given recombinant IL-10 at the time of immunization with PALPS there was a decrease in the PALPS-specific antibody response but an increase in the polyclonal IgM, IgG2a, IgG2b, IgG3 response whereas the polyclonal IgG1 response was decreased by a five-fold margin. The results of these studies suggest that both the antigen-specific and the polyclonal response can be influenced in a different manner by IL-4 or by IL-10.