Humoral responses to Pneumocystis carinii in patients with acquired immunodeficiency syndrome and in immunocompromised homosexual men

Serologic responses to recombinant Pneumocystis jirovecii major surface glycoprotein among Ugandan patients with respiratory symptoms

BACKGROUND

Little is known about the serologic responses to Pneumocystis jirovecii major surface glycoprotein (Msg) antigen in African cohorts, or the IgM responses to Msg in HIV-positive and HIV-negative persons with respiratory symptoms.

METHODS

We conducted a prospective study of 550 patients, both HIV-positive (n = 467) and HIV-negative (n = 83), hospitalized with cough ≥2 weeks in Kampala, Uganda, to evaluate the association between HIV status, CD4 cell count, and other clinical predictors and antibody responses to P. jirovecii. We utilized ELISA to measure the IgM and IgG serologic responses to three overlapping recombinant fragments that span the P. jirovecii major surface glycoprotein: MsgA (amino terminus), MsgB (middle portion) and MsgC1 (carboxyl terminus), and to three variations of MsgC1 (MsgC3, MsgC8 and MsgC9).

RESULTS

HIV-positive patients demonstrated significantly lower IgM antibody responses to MsgC1, MsgC3, MsgC8 and MsgC9 compared to HIV-negative patients. We found the same pattern of low IgM antibody responses to MsgC1, MsgC3, MsgC8 and MsgC9 among HIV-positive patients with a CD4 cell count <200 cells/µl compared to those with a CD4 cell count ≥200 cells/µl. HIV-positive patients on PCP prophylaxis had significantly lower IgM responses to MsgC3 and MsgC9, and lower IgG responses to MsgA, MsgC1, MsgC3, and MsgC8. In contrast, cigarette smoking was associated with increased IgM antibody responses to MsgC1 and MsgC3 but was not associated with IgG responses. We evaluated IgM and IgG as predictors of mortality. Lower IgM responses to MsgC3 and MsgC8 were both associated with increased in-hospital mortality.

CONCLUSIONS

HIV infection and degree of immunosuppression are associated with reduced IgM responses to Msg. In addition, low IgM responses to MsgC3 and MsgC8 are associated with increased mortality.

Serum antibody levels to the Pneumocystis jirovecii major surface glycoprotein in the diagnosis of P. jirovecii pneumonia in HIV+ patients

Background

Pneumocystis jirovecii remains an important cause of fatal pneumonia (Pneumocystis pneumonia or PcP) in HIV+ patients and other immunocompromised hosts. Despite many previous attempts, a clinically useful serologic test for P. jirovecii infection has never been developed.

Methods/Principal Findings

We analyzed serum antibody responses to the P. jirovecii major surface glycoprotein recombinant fragment C1 (MsgC1) in 110 HIV+ patients with active PcP (cases) and 63 HIV+ patients with pneumonia due to other causes (controls) by an enzyme-linked immunosorbent assay (ELISA). The cases had significantly higher IgG and IgM antibody levels to MsgC1 than the controls at hospital admission (week 0) and intervals up to at least 1 month thereafter. The sensitivity, specificity and positive predictive value (PPV) of IgG antibody levels increased from 57.2%, 61.7% and 71.5% at week 0 to 63.4%, 100%, and 100%, respectively, at weeks 3–4. The sensitivity, specificity and PPV of IgM antibody levels rose from 59.7%, 61.3%, and 79.3% at week 0 to 74.6%, 73.7%, and 89.8%, respectively, at weeks 3–4. Multivariate analysis revealed that a diagnosis of PcP was the only independent predictor of high IgG and IgM antibody levels to MsgC1. A high LDH level, a nonspecific marker of lung damage, was an independent predictor of low IgG antibody levels to MsgC1.

Conclusions/Significance

The results suggest that the ELISA shows promise as an aid to the diagnosis of PCP in situations where diagnostic procedures cannot be performed. Further studies in other patient populations are needed to better define the usefulness of this serologic test.

Human immunodeficiency virus-infected patients with prior Pneumocystis pneumonia exhibit increased serologic reactivity to several major surface glycoprotein clones

Recombinant clones of the carboxyl terminus of the major surface glycoprotein (MsgC) of Pneumocystis jirovecii are useful for analyzing serologic responses in humans. However, there is no standardized set of antigens in general use, which could lead to conflicting results. We have previously shown that human immunodeficiency virus type 1 (HIV-1)-infected patients with prior Pneumocystis pneumonia (PcP+) responded more frequently and more strongly to a clone of MsgC than did HIV-1-infected patients without PcP (PcP-). Here we test three new clones of MsgC to determine the effect of antigenic sequence variation on immune reactivity in blood donors and HIV-infected patients previously analyzed for reactivity to our original MsgC clone. In Western blot analyses, PcP+ patients exhibited the highest frequency of reactivity to each MsgC clone, and the frequency of reactivity with all four MsgC clones together was significantly higher in sera from PcP+ patients than in sera from the other patient groups. Furthermore, in an enzyme-linked immunosorbent assay we found that the PcP+ population had the highest level of reactivity to two of the four clones tested. One of the new clones could distinguish between PcP+ and PcP- populations, and two MsgC clones could distinguish blood donors from the other patient populations. The results show that inherent differences in MsgC amino acid sequence can affect recognition by antibodies independently of variations in protein length or patient population, and the utility of a clone depends on its sequence and on the populations tested.

Enzyme-linked immunosorbent assay and serologic responses to Pneumocystis jiroveci

Seroepidemiologic studies of Pneumocystis pneumonia (PCP) in humans have been limited by inadequate reagents. We have developed an enzyme-linked immunosorbent assay (ELISA) using three overlapping recombinant fragments of the human Pneumocystis major surface glycoprotein (MsgA, MsgB, and MsgC) for analysis of antibody responses in HIV-positive patients and healthy blood donors. HIV-positive patients had significantly higher antibody levels to all Msg fragments. Furthermore, HIV-positive patients who experienced a previous episode of PCP (PCP-positive) had higher levels of antibodies to MsgC than patients who never had PCP. A significant association was found between ELISA antibody level and reactivity by Western blot in HIV-positive patients, especially those who were PCP-positive. Thus, this ELISA will be useful in studying serum antibody responses to Pneumocystis in different human populations.

Decreased production of local immunoglobulin A to Pneumocystis carinii in bronchoalveolar lavage fluid from human immunodeficiency virus-positive patients

An enzyme-linked immunosorbent assay and a Western blot analysis were developed to study the antibody response to Pneumocystis carinii in serum and bronchoalveolar lavage fluid from 27 human immunodeficiency virus 27 (HIV)-infected patients with P. carinii pneumonia (Pcp), 32 patients without Pcp, and 51 HIV-negative controls. Urea was used for the correct dilution of epithelial lining fluid, and albumin was used to evaluate transudation from plasma for the assessment of local production of antibodies to P. carinii. By contrast with those of immunoglobulin G (IgG), IgA responses to P. carinii were increased in serum from HIV-positive patients compared to negative controls. Local production of antibodies to P. carinii, especially IgA, was decreased in patients with Pcp. In a study of 10 patients of each group, IgG and IgA responses to gp116 from P. carinii were lower in patients with Pcp than in other groups. These results suggest that, in addition to alveolar macrophages, local antibodies may play a role in host defense against P. carinii.

Characterization of major surface glycoprotein genes of human Pneumocystis carinii and high-level expression of a conserved region

To facilitate studies of Pneumocystis carinii infection in humans, we undertook to better characterize and to express the major surface glycoprotein (MSG) of human P. carinii, an important protein in host-pathogen interactions. Seven MSG genes were cloned from a single isolate by PCR or genomic library screening and were sequenced. The predicted proteins, like rat MSGs, were closely related but unique variants, with a high level of conservation among cysteine residues. A conserved immunodominant region (of approximately 100 amino acids) near the carboxy terminus was expressed at high levels in Escherichia coli and used in Western blot studies. All 49 of the serum samples, which were taken from healthy controls as well as from patients with and without P. carinii pneumonia, were reactive with this peptide by Western blotting, supporting the hypothesis that most adult humans have been infected with P. carinii at some point. This recombinant MSG fragment, which is the first human P. carinii antigen available in large quantities, may be a useful reagent for investigating the epidemiology of P. carinii infection in humans.

Seroreactivity to Pneumocystis carinii in patients with AIDS versus other immunosuppressed patients

The aim was to study the humoral response to Pneumocystis carinii and its diagnostic use in patients with P. carinii pneumonia (PCP). The antibody response was measured by indirect immunofluorescence in AIDS patients versus other immunosuppressed patients with 122 episodes of confirmed PCP. During the early acute stage of the pneumonia, anti-P. carinii antibodies were found in 17% of AIDS and 24% of other immunosuppressed patients. In the second serum sample, antibodies were still found in 17% of the AIDS patients but in as many as 56% of the otherwise immunosuppressed patients. Antibodies were also found in 17% of HIV-positive and 15% of other immunosuppressed control patients, but only in 3% of immunocompetent controls (p < 0.001). Paired sera were available from 55 patients during 58 PCP episodes. Seroconversion or a fourfold rise in titre was detected in only 1/36 (3%) AIDS patients but in 10/22 (45%), (95% c.i.: 24-66%) other immunosuppressed patients (p < 0.001). We conclude that AIDS patients seem to have lost their ability to develop a humoral response to P. carinii during pneumonia, whereas many other immunosuppressed patients do respond. In these patients the serological test against P. carinii was of no diagnostic value in the acute phase of the infection, whereas when analysing paired sera it was a useful complement to the clinical diagnosis.

Antibody response to a major human Pneumocystis carinii surface antigen in patients without evidence of immunosuppression and in patients with suspected atypical pneumonia

IgG and IgM antibodies to a purified human Pneumocystis carinii surface antigen (gp95) were measured in 694 serum specimens from two different population groups using an EIA technique. In a population of 441 patients with no evidence of immunosuppression, the percentage of persons positive for IgG antibodies to gp95 was significantly lower in the age group 1 to 9 years (30%, 23/77) compared to persons 10 to 19 years old (56%, 49/88). In the age group 1 to 14 years there was a significant correlation between the percentage of persons with IgG antibodies to gp95 and age. In 106 consecutive patients under evaluation due to atypical pneumonia, 76 patients showed no change in the titre of antibodies to Legionella spp. or Mycoplasma pneumoniae in two consecutive serum samples. Three of these 76 patients (4%) demonstrated an increase in the level of IgG antibodies to gp95 in the paired samples. One of these patients had a verified Pneumocystis carinii pneumonia, and the two others were elderly men in whom no microbiological diagnosis of the pneumonia was established. Thus, it is concluded that IgG antibodies to gp95 develop in the majority of nonimmunosuppressed persons before the age of 13. Furthermore, Pneumocystis carinii pneumonia should be considered in the differential diagnosis in patients suspected of having atypical pneumonia.

IgM response to a human Pneumocystis carinii surface antigen in HIV-infected patients with pulmonary symptoms

We have developed an ELISA to detect IgM antibodies to a major human Pneumocystis carinii surface antigen (gp95), and investigated the IgM response in 128 HIV-infected patients who underwent bronchoscopy for evaluation of pulmonary symptoms. Only 5 (4%) patients had IgM antibodies to P. carinii gp95. Four of the 5 patients with IgM antibodies also had IgG antibodies to gp95 and microbiologically proven P. carinii pneumonia (PCP). In 76/128 patients for whom serial samples were available, changes in antibody response were determined. In 3 patients we demonstrated an increase in IgM antibody response to gp95. These patients also showed an increase in IgG antibodies to gp95 and had microbiologically proven PCP. Prior to the development of the IgM response, IgG antibodies to gp95 were detectable in all 3 patients. Thus, HIV-infected patients with PCP seldom produce IgM antibodies to the major human P. carinii surface antigen. The increase in IgM response during the course of PCP observed in 3 patients suggests either reinfection with a new strain, or antigenic drift of an already acquired strain of P. carinii.

Use of intravenous immunoglobulin in acquired immune deficiency syndrome

Patients infected with the human immunodeficiency virus (HIV) may have an antibody deficiency and a deficiency of cellular immunity. Intravenous immunoglobulin (IVIG) preparations may benefit HIV-infected children and adults with recurrent bacterial infections at doses of 200 to 400 mg/kg every 2 to 4 weeks. In addition, IVIG (1 to 2 g/kg) is effective at raising platelet counts to hemostatic levels in HIV-infected patients with idiopathic thrombocytopenic purpura and life-threatening bleeding. Indirect evidence also suggests that IVIG may be effective in preventing Pneumocystis carinii pneumonia. Finally, recent studies suggest that specific anti-HIV antibody preparations may have a therapeutic role, either as immunoglobulin concentrates or as immunoadhesions and immunotoxins. However, further investigations are needed to exclude antibody enhancement of HIV infection by the Fc receptor or the complement receptor.

Pneumocystis carinii, an opportunist in immunocompromised patients

Pneumocystis carinii has been recognized as a cause of pneumonia in immunocompromised patients for over 40 years. Until the 1980s, Pneumocystis pneumonia (pneumocystosis) was most often seen in patients undergoing chemotherapy for malignancy or transplantation. Infection could be prevented by trimethoprim-sulfamethoxazole prophylaxis; thus, it was an uncommon clinical problem. With the onset of the AIDS epidemic, Pneumocystis pneumonia has become a major problem in the United States because it develops in approximately 80% of patients with AIDS and because almost two-thirds of patients have adverse reactions to anti-Pneumocystis drugs. Thus, physicians and laboratories in any community may be called upon to diagnose and provide care for patients with Pneumocystis pneumonia. The classification of the organism is currently controversial, but it is either a protozoan or a fungus. P. carinii appears to be acquired during childhood by inhalation and does not cause clinical disease in healthy persons but remains latent. If the person becomes immunosuppressed, the latent infection may become activated and lead to clinical disease. Damage of type I pneumocytes by Pneumocystis organisms leads to the foamy alveolar exudate which is characteristic of the disease. Diagnosis is established by morphologic demonstration of Pneumocystis organisms in material from the lungs. Current efforts to find better anti-Pneumocystis drugs should provide more effective therapy and prophylaxis.

Pulmonary pathogens in HIV-infected patients

On well defined criteria a total of 102 fiberoptic bronchoscopies (FB) were done on HIV-infected patients with pulmonary symptoms. A microbiological agent was identified in 85 patients (83%). Pneumocystis carinii (PC) was histologically verified in 61 patients, bacteria cultured in 22 patients, and cytomegalovirus (CMV) cultured in 17 patients. A histological diagnosis of CMV was only established in 2/17 patients. In the present study, a CMV positive culture from bronchial lavage fluid did not appear related to the clinical picture. Patients with P. carinii pneumonia (PCP) had significantly higher IgA, lower CD4-count, more commonly dyspnea and an X-ray showing diffuse interstitial infiltration than patients without PCP. Patients with bacterial pneumonia had significantly higher CD4-count, lower IgA, more commonly productive cough and an X-ray showing focal infiltration. In more than 75% of the patients, microorganisms identified were responsible for the pulmonary symptoms leading to bronchoscopy. Mainly PC and bacterial pathogens, both of which are treatable, were responsible for these infections. Pulmonary infections of clinical relevance besides PCP and bacterial infections were rare (3%, 95% confidence limit 1-8%).

Reduced concentrations of IgG antibodies to Pneumocystis carinii in HIV-infected patients during active Pneumocystis carinii infection and the possibility of passive immunisation

The relationship between Pneumocystis carinii antibody concentrations and acute Pneumocystis infection was investigated by testing sequential samples of serum from HIV antibody-positive patients with respiratory symptoms and HIV-negative immunocompromised patients by means of an indirect immunofluorescence assay for specific IgG antibodies to P. carinii. Loss of circulating antibody at the time of active Pneumocystis infection was observed in five patients with proven infection. Three others showed recovery of antibody coinciding with treatment and clinical recovery from infection. Concentrations of specific IgG antibody against P. carinii were measured in 40 blood donors and in six different batches of an intravenous immunoglobulin (IV Ig) preparation. Titres greater than 128 were found in the IV Ig batches examined. The use of IV Ig, either alone or in conjunction with other therapeutic agents, should therefore be considered in patients suffering from acute infection with P. carinii.

Parasite infections in AIDS

'Illnesses no one's got' was the epidemiological clue that led to the identification of AIDS as a new disease in 1981 when a rare infectious organism Pneumocystis carinii was seen in previously healthy homosexuals. Since then a wide range of parasite infections has been recognized in AIDS patients. However, these patients are not susceptible to just any passing parasite. The human immunodeficiency virus (HIV) produces a specific immune defect and only parasites that can exploit that defect will be able to flourish. In this review Diana Lockwood and Jonathan Weber explore the spectrum of parasite diseases recognized in AIDS and also consider those parasites that occur infrequently in AIDS. Analysis of parasitic infections that AIDS patients do not suffer from will yield valuable information about immune recognition and handling of these parasites.

The relationship of serum IgA concentration to human immunodeficiency virus (HIV) infection: a cross-sectional study of HIV-seropositive individuals detected by screening in the United States Air Force

Serum immunoglobulins were measured in 107 patients with human immunodeficiency virus seropositivity. Each patient was categorized by the Walter Reed staging classification and serum concentrations of immunoglobulins were compared with patient staging. Serum IgM concentrations were normal in all but nine patients. Serum IgG concentrations were elevated in 74 of 107 patients, with no significant differences noted between different stages of disease severity. Serum IgA concentrations were elevated in 38 of 107 patients, with a significant relationship noted between increasing staging category and increasing serum IgA concentration (p = 0.0001). Serum IgA concentrations in patients with human immunodeficiency virus seropositivity may be a useful marker of immunologic progression of disease.

Enzyme-linked immunosorbent assay compared with indirect immunofluorescence test for detection of Pneumocystis carinii specific immunoglobulins G, M, and A

An ELISA to measure Pneumocystis carinii-specific IgG, IgM, and IgA has been developed. The antigen was prepared from purified cysts by sonication and ultracentrifugation. Antigen particles with sedimentation coefficients less than 165 S were used. The technique has been compared with indirect immunofluorescence, using whole cysts as antigen. Ninety human sera were assayed. The results were significantly correlated. The ELISA-technique was more sensitive, and owing to the soluble antigen the daily variation was less than 1 per cent. The technique is useful for quick and reliable detection of Pneumocystis carinii antibodies in a routine laboratory.

Unusual manifestations of secondary syphilis and abnormal humoral immune response to Treponema pallidum antigens in a homosexual man with asymptomatic human immunodeficiency virus infection

The case presented here involves a 32-year-old homosexual man with human immunodeficiency virus (HIV) seropositivity and unusual manifestations of secondary syphilis. The patient presented with syphilitic keratoderma and chorioretinitis, and his appearance superficially resembled that of a patient with Reiter's syndrome. Although nontreponemal and treponemal tests for syphilis showed reactivity, the patient's humoral immune response to individual polypeptides of Treponema pallidum, measured by Western blot analysis, was markedly abnormal. The possible relationship between asymptomatic HIV infection and an abnormal humoral immune response to a second pathogen, in this case T. pallidum, is discussed. Our case is one of several recent cases of active syphilis reported in individuals with HIV seropositivity.

Humoral and cellular responses to Pneumocystis carinii, CMV, and herpes simplex in patients with AIDS and in controls

The titers of IgG and IgA to Pneumocystis carinii in 36 AIDS patients did not differ significantly from those in 31 controls. Only 2/15 patients (13%) with P. carinii pneumonia (PCP) had titers of IgM antibodies greater than or equal to 5, which is significantly less frequent than in 32 controls (62%) and in 21 AIDS patients without PCP (43%). The risk of PCP was 5 times higher in patients without IgM antibodies to P. carinii than in patients who had these antibodies. A significantly higher percentage of those without PCP (57%) showed increasing titers of IgM antibodies to P. carinii in the second of paired samples taken about 6 months apart, compared with whose with PCP (9%; p = 0.05). All patients had high titers of antibodies to CMV and HSV and normal total concentrations of immunoglobulins. None of the patients responded in lymphocyte transformation to P. carinii, CMV, or HSV antigens. There is no obvious explanation to the selective lack of IgM antibodies to P. carinii in patients with PCP. Lack of IgM antibodies may be a marker for an immunodeficiency to P. carinii.

The immunodeficiency of bone marrow-transplanted patients. II. CD8-related suppression by patient lymphocytes of the response of donor lymphocytes to mitogens, antigens, and allogeneic cells

Lymphocytes from 21 patients sampled 1-6 months after bone marrow transplantation (BMT) were tested for functional suppressor activity against marrow-donor lymphocytes in the lymphocyte transformation test. Suppression of donor responses to allogeneic (i.e. mixed lymphocyte reaction, MLR) and antigenic stimulation by irradiated (7600 rad) post-BMT cells was observed in about two-thirds of the combinations tested (N = 20 and N = 9). The suppression of donor MLR and antigen responses ranged between 5-52% and 10-46%, respectively. Irradiated post-BMT cells significantly suppressed donor responses to suboptimal concentrations of phytohaemagglutinin (PHA) (median suppression: 28%; P less than 0.05; N = 7) and concanavalin A (Con A) (median suppression: 31%; P less than 0.05; N = 6). A clearly suppressive effect of post-BMT cells was observed when the ratios of CD4+/CD8+ post-BMT cells were lower than 0.5 (P less than 0.01). In three experiments, the depletion of the CD8- but not of the CD4-positive subset abrogated the suppression of the donor MLR by post-BMT cells. The suppression by post-BMT cells (irradiated) of MLR and mitogen responses was comparable whether the responding cells were derived from the donor or from HLA-DR-incompatible, unrelated individuals. The proliferative capacity of post-BMT cells compared to that of donor cells was assayed in the MLR with unrelated, HLA-DR-incompatible stimulator cells. A significantly decreased proliferative capacity (median 20% of that of donor cells) was found (P less than 0.01; N = 16). A weak inverse correlation (P less than 0.05; N = 16) between the proliferative and the suppressive capacity of post-BMT cells in the MLR was observed. These findings indicate that the decreased proliferative capacity upon mitogen, antigen, and alloantigen stimulation observed in most patients within 1-6 months after BMT may be partly due to non-specific suppression by CD8+ cells.

Lymphocyte transformation response to pokeweed mitogen as a predictive marker for development of AIDS and AIDS related symptoms in homosexual men with HIV antibodies

To identify factors that may predict the development of the acquired immune deficiency syndrome (AIDS) or AIDS related symptoms various immunological measurements were studied in a group of homosexual men attending screening clinics for AIDS in Copenhagen. Fifty seven men whose ratio of T helper lymphocytes to T suppressor lymphocytes (CD4:CD8 ratio) was less than 1.0 before the study began were included. Forty two were positive for antibody to the human immunodeficiency virus (HIV), of whom 38 were reinvestigated after a median observation period of 10 months. Among the seropositive men the transformation responses to pokeweed mitogen and cytomegalovirus and the absolute count of CD4 positive lymphocytes were the most common abnormal values. In particular, a low relative response to pokeweed mitogen on initial investigation correlated with a worsened clinical condition on reinvestigation. The risk of a worsened clinical condition was 55 times higher in seropositive men whose responses to pokeweed mitogen were low than in other seropositive men. The corresponding relative risks for low transformation responses to cytomegalovirus and for a decreased absolute count of CD4 positive lymphocytes were 18 and six. The relative response to pokeweed mitogen is therefore a very sensitive short term predictive marker of the clinical condition of seropositive patients who have a CD4:CD8 ratio of less than 1.0.

Evidence for depressed humoral immunity to Pneumocystis carinii in homosexual males, commercial plasma donors, and patients with acquired immunodeficiency syndrome

Heterosexual controls were found to have significantly higher titers of immunoglobulin G antibody to Pneumocystis carinii than did patients with the acquired immunodeficiency syndrome (AIDS) and P. carinii pneumonitis, human immunodeficiency virus (HIV) antibody-positive or -negative homosexual male "gay bar" patrons, and HIV antibody-positive or -negative commercial plasma donors. The T-helper/T-suppressor lymphocyte ratios of HIV antibody-negative homosexual male gay bar patrons were slightly depressed (mean = 1.31 +/- 0.54) compared with those of heterosexual controls (mean = 1.79 +/- 0.32). In addition to other recognized factors, preexisting humoral as well as cell-mediated immune deficits before infection with HIV may help to explain the prevalence of and morbidity and mortality associated with P. carinii pneumonitis in AIDS patients.

Pneumocystis carinii: immunoblotting and immunofluorescent analyses of serum antibodies during experimental rat infection and recovery

Serum antibodies to Pneumocystis carinii were measured in rats by the indirect fluorescent antibody and immunoblotting techniques. Serum IgG and IgM antibodies developed with environmental exposure to P. carinii, were low or absent during immunosuppression to induce P. carinii pneumonia, and rose when immunosuppression was withdrawn. The IgG and IgM antibodies formed at the same time, but the titers of each antibody varied in individual rats. Serum IgG antibodies by immunoblotting recognized bands of 45, 50, and 116 kDa as the major reactive moieties of P. carinii. The bands were detected with sera from all rat groups in a temporal pattern which closely paralleled antibody formation by indirect immunofluorescence. The pattern of immunoblotting reactivity varied among individual rats, particularly with immunosuppression. Additional bands were detected with prolonged exposure to P. carinii. Thus, the rat makes both IgG and IgM antibodies to P. carinii, and specific P. carinii antigens identified in this immune response might be targeted for future serologic studies.

Immunological studies in the acquired immunodeficiency syndrome. II. Active suppression or intrinsic defect--investigated by mixing AIDS cells with HLA-DR identical normal cells

The lymphocyte transformation responses to mitogens (phytohaemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM)), allogeneic cells, and the antigen-purified protein derivative (PPD) were studied in six acquired immunodeficiency syndrome (AIDS) patients and in six healthy controls, each of whom was HLA-DR- and mixed lymphocyte culture (MLC)-identical with one of the AIDS patients. No evidence of suppression was observed when irradiated or non-irradiated AIDS peripheral blood mononuclear cells (PBMC) were added to cultures of HLA-DR-identical PMBC from healthy controls stimulated with the strong mitogens PHA and Con A or with allogeneic cells, but suppression may be involved in the decreased responses in cultures stimulated with PWM or PPD. Addition of supernatants from macrocultures of AIDS cells did not suppress responses of control PBMC. Thus, suppression by any lymphocyte subset or soluble factor alone cannot explain the generally severely depressed transformation responses in AIDS. Addition of heavily irradiated HLA-DR-identical PBMC from healthy controls or supernatants from these cultures led to increased responses in cultures of mitogen-stimulated AIDS PBMC and in some cultures of antigen or allogeneic cell-stimulated AIDS PBMC, which were of the same magnitude as seen after the addition of commercially obtained T-cell growth factor (TCGF). This indicates that AIDS cells are deficient in producing TCGF. Heavily irradiated AIDS PBMC were capable of restoring the transformation responses to mitogens and antigens of purified HLA-DR-identical normal T cells, indicating that AIDS cells have a normal antigen-presenting capacity and interleukin (IL-1) production. However, AIDS PBMC had a very poor capacity to stimulate normal PBMC in MLC. Together, our experiments suggest that the immune deficiency in AIDS cells may be partially due to a decreased capability of T lymphocytes to produce TCGF and that a decreased number and/or function of dendritic cells may also be involved.