Plasma and salivary IgA subclasses and IgM in HIV-1-infected individuals

The Multifaceted Nature of Immunoglobulin A and Its Complex Role in HIV

IgA is the most abundant immunoglobulin in mucosal secretions, and understanding the role of IgA in both protection from HIV acquisition and modulation of HIV disease progression is a field of considerable controversy and renewed research interest. Analysis of the RV144 clinical trial associated plasma HIV envelope-specific monomeric IgA from vaccines with reduced vaccine efficacy. The RV144 trial, however, only assessed for plasma IgA, which was not further subclassed, and the role of mucosal IgA was not addressed as mucosal samples were not collected. On the other hand, several studies have detected envelope-specific IgA in mucosal secretions of highly exposed persistently seronegative cohorts, while recent macaque simian-HIV passive immunization studies have suggested a potentially protective role for mucosal IgA. It is well established that total IgA in serum appears to correlate with HIV disease progression. In contrast, a selective deficit of anti-HIV IgA responses in HIV infection is apparent, with a number of recent studies beginning to elucidate the mechanisms behind these dysfunctional IgA responses. In this review, we highlight the dichotomy that exists in the literature as to whether anti-HIV IgA is protective or harmful to the host. Herein, we emphasize the importance of distinguishing between monomeric, multimeric, and isoforms of IgA and review what is known about the complex and diverse interactions of various molecular forms of IgA with HIV in both the systemic circulation and mucosal compartments.

Saliva as a diagnostic fluid

Salivary diagnostics is a dynamic and emerging field utilizing nanotechnology and molecular diagnostics to aid in the diagnosis of oral and systemic diseases. In this article the author critically reviews the latest advances using oral biomarkers for disease detection. The use of oral fluids is broadening perspectives in clinical diagnosis, disease monitoring, and decision making for patient care. Important elements determining the future possibilities and challenges in this field are also discussed.

Mucosal HIV transmission and vaccination strategies through oral compared with vaginal and rectal routes

IMPORTANCE OF THE FIELD

There are currently over thirty million people infected with HIV and there are no vaccines available to prevent HIV infections or disease. The genitourinary, rectal and oral mucosa are the mucosal HIV transmission routes. An effective vaccine that can induce both systemic and local mucosal immunity is generally accepted as a major means of protection against mucosal HIV transmission and AIDS.

WHAT THE READER WILL GAIN

Structure and cells that comprise the oral, vaginal and rectal mucosa pertaining to HIV transmission and vaccination strategies through each mucosal route to prevent mucosal and systemic infection will be discussed.

AREAS COVERED IN THIS REVIEW

Covering publications from 1980s through 2010, mucosal transmission of HIV and current and previous approaches to vaccinations are discussed.

TAKE HOME MESSAGE

Although oral transmission of HIV is far less common than vaginal and rectal transmissions, infections through this route do occur through oral sex as well as vertically from mother to child. Mucosal vaccination strategies against oral and other mucosal HIV transmissions are under intensive research but the lack of consensus on immune correlates of protection and lack of safe and effective mucosal adjuvants and delivery systems hamper progress towards a licensed vaccine.

HIV-1 exposed uninfected men who have sex with men have increased levels of salivary CC-chemokines associated with sexual behavior

OBJECTIVES

To determine whether soluble molecules with known anti-HIV-1 activity are increased in saliva of HIV-1 exposed uninfected individuals of discordant couples of men who have sex with men (MSM), and whether the levels of these molecules are associated with genetic polymorphisms, sexual behavior and/or HIV-1 neutralizing capacity.

METHODS

Saliva and PBMC were collected from exposed uninfected individuals (n=25), and low-risk controls (n=22). Levels of CCL2, CCL3, CCL4, CCL5 and CCL11 were detected by Luminex, and SLPI, LL-37, alpha-defensins and IgA2 were detected by ELISA. Single nucleotide polymorphisms (SNPs) were investigated using mass spectrometry or PCR-sequencing. HIV-1 neutralizing activity was assessed using PBMCbased neutralization assays. Self-reported questionnaires described sexual behavior.

RESULTS

Exposed uninfected individuals had significantly higher levels of salivary CCL2, CCL4, CCL5 and CCL11 as compared with controls although genetic polymorphisms within the corresponding regions were equally distributed. IgA2 was also increased in exposed uninfected individuals, whereas neither CCL3, SLPI, LL-37 nor alpha-defensins differed between exposed uninfected individuals and controls. The HIV-1 neutralizing capacity of saliva was associated with higher levels of CC-chemokines (but not SLPI, LL-37, alpha-defensins or IgA2) in both exposed uninfected individuals and controls. The increased levels of CC-chemokines were associated with a higher frequency of unprotected oral sex and/or additional casual sex partners.

CONCLUSION

HIV-1 exposed uninfected MSM had higher levels of salivary CC-chemokines compared with controls, this finding associated with sexual behavior rather than with genetic polymorphisms. The increased levels of CC-chemokines associated with HIV-1 neutralizing capacity in saliva.

Envelope-specific antibody response in HIV-2 infection: C2V3C3-specific IgG response is associated with disease progression

OBJECTIVE

To examine the unspecific and envelope-specific IgA and IgG responses in acute and chronic HIV-2 infection.

METHODS

Twenty-eight chronically infected adults and two children with perinatal infection were studied. Total plasma concentrations of IgA and IgG were determined by nephelometry. IgA and IgG reactivity against the immunodominant region in gp36 and the C2V3C3 region in gp125 was tested with the enzyme-linked immunosorbent assay (ELISA)-HIV-2 assay. Clonal sequences of the C2V3C3 env region were obtained for most patients.

RESULTS

Total plasma IgG concentration, but not IgA, was significantly higher than normal in HIV-2 patients and correlated inversely with CD4 T-cell counts. Seroconversion to gp36 occurred during the first year of life in both infants. The infant with rapid disease progression did not elicit C2V3C3-specific antibodies. Most chronically infected patients produced plasma IgG1, IgG3 and IgA antibodies against gp36 and C2V3C3. Lack of C2V3C3-specific IgG response in two patients was associated with a major antigenic change in the V3 region. In longitudinal analysis, there was a significant inverse association between the C2V3C3-specific IgG antibody response and the number of CD4 T cells.

CONCLUSION

HIV-2 promotes an early, strong and broad gp36 and C2V3C3-specific IgG and IgA response. Increase in the IgG response against the envelope C2V3C3 region is associated with increased loss of CD4 T cells in chronically infected patients. These results provide further support for the immune protective role of the C2V3C3 envelope region during HIV-2 infection and have direct implications for HIV-2 diagnosis, clinical management and pathogenesis.

The mucosae-associated epithelial chemokine (MEC/CCL28) modulates immunity in HIV infection

BACKGROUND

CCL28 (MEC) binds to CCR3 and CCR10 and recruits IgA-secreting plasma cells (IgA-ASC) in the mucosal lamina propria (MLP). Mucosal HIV-specific IgA are detected in HIV-infection and exposure. The CCL28 circuit was analyzed in HIV-infected and-exposed individuals and in HIV-unexposed controls; the effect of CCL28 administration on gastrointestinal MLP IgA-ASC was verified in a mouse model.

METHODOLOGY/FINDINGS

CCL28 was augmented in breast milk (BM) plasma and saliva of HIV-infected and -exposed individuals; CCR3+ and CCR10+ B lymphocytes were increased in these same individuals. Additionally: 1) CCL28 concentration in BM was associated with longer survival in HIV vertically-infected children; and 2) gastro-intestinal mucosal IgA-ASC were significantly increased in VSV-immunized mice receiving CCL28.

CONCLUSIONS

CCL28 mediates mucosal immunity in HIV exposure and infection. CCL28-including constructs should be considered in mucosal vaccines to prevent HIV infection of the gastro-intestinal MLP via modulation of IgA-ASC.

Paucity of antigen-specific IgA responses in sera and external secretions of HIV-type 1-infected individuals

This study was undertaken to resolve existing controversies with respect to the detection of IgA HIV-1-specific mucosal antibodies in infected individuals. External secretions, including tears, nasal, rectal, and vaginal washes, saliva, semen, urine, and sera were obtained from 50 HIV-1-infected individuals and 20 controls using collection procedures that minimize the irritation of mucosal surfaces. Levels of total and antigen (gp120 and gp160)-specific antibodies of the IgG and IgA isotypes were measured by assays that proved reliable in a large multicenter study: quantitative ELISA and chemiluminescence-enhanced Western blot analyses. Although the levels of total IgG and IgA were increased or remained unchanged in body fluids of HIV-1-infected individuals as compared to the controls, HIV-1-specific IgA antibodies were either absent or present at low levels even in secretions with characteristically high relative contents of total IgA vs. IgG (saliva, tears, and rectal and nasal washes). In these secretions, HIV-1-specific IgG antibodies dominated. In assessing levels and frequency of detection of IgG antibodies, both female and male genital tract secretions, urine, and nasal wash were preferable to parotid saliva and especially to rectal wash. External secretions contained IgG antibodies to gp160> gp120> gp41 and p24; when present, IgA antibodies were predominantly directed at gp160. Analyses of peripheral blood antibody-secreting cells (ASC) isolated from the same individuals paralleled these serological findings: gp160-specific IgG-secreting ASC were dominant. Therefore, in striking contrast to other mucosally encountered microbial infections, HIV-1 does not induce vigorous specific IgA responses in any body fluid examined or in ASC in peripheral blood.

Tropism-restricted neutralization by secretory IgA from parotid saliva of HIV type 1-infected individuals

In this study we examined secretory IgA, isolated from the parotid saliva of 10 HIV-1-infected subjects, for its ability to influence HIV-1 infection of peripheral blood mononuclear cells with two R5 and two X4 primary isolates. Salivary IgA from four subjects was found to inhibit both R5 viruses but not the X4 viruses. In another subject, salivary IgA inhibited both X4 viruses but not the R5 viruses. The specificity of these antibodies seemed to be directed against, but not restricted to, gp160 and gp120. Compared with subjects whose salivary IgA did not inhibit HIV-1 infection, subjects who displayed neutralizing activity were in relatively early stages of disease and had CD4(+) T cell counts greater than 200 cells/microl. Our data indicate the presence of tropism-specific (more frequently R5-specific) neutralizing antibodies in HIV-1-infected subjects. Because mucosal transmission of HIV-1 occurs exclusively in R5 viruses, and X4 viruses often emerge in established infection and account for viral persistence later in disease, our data suggest a potential role for secretory IgA in preventing viral transmission, but a less likely effect on chronic infection.