Rapid increase of mucosal CD4 T cells followed by clearance of intestinal cryptosporidiosis in an AIDS patient receiving highly active antiretroviral therapy.

Highly active antiretroviral therapy (HAART) suppresses the replication of human immunodeficiency virus (HIV) and leads to an increase in circulating CD4 T lymphocytes, but its effects on other immune compartments such as the intestinal mucosa are not well understood. We describe a severely immunodeficient HIV-infected patient with intractable watery diarrhea and weight loss caused by infection with Cryptosporidium parvum in whom we studied virologic and immunologic changes in both peripheral blood and the intestinal mucosa after initiating HAART. Mucosal biopsies were performed by rectoscopy before and at several time points after HAART was begun. Nucleic acids were extracted from rectal biopsy specimens and blood samples, and HIV RNA was measured by reverse-transcription polymerase chain reaction. Lymphocytes were isolated from rectal biopsy specimens after mechanical disaggregation, and circulating and mucosal CD4 T cells were determined by flow cytometry. HAART led to clinical recovery and eradication of cryptosporidiosis. In both blood and mucosa, HIV RNA decreased below the limit of detection and CD4 T cells increased. Mucosal CD4 T cells increased much faster and to much higher levels than circulating CD4 T cells. Our findings show a rapid repopulation of the intestinal mucosa with CD4 T cells after initiation of HAART that can effectively restore mucosal immunity, leading to eradication of opportunistic pathogens.

Secretory immunity in HIV infection.

Secretory IgA plays a crucial role in the defense of pathogens at mucosal surfaces. As CD4+ T cells are lost early in the mucosa of human immunodeficiency virus (HIV)-infected patients and as CD4+ T cells play an essential role in the regulation of specific IgA responses to pathogenic agents at mucosal sides, it could be expected that this first line of defense is impaired in HIV-infected patients. Therefore, several studies were undertaken to characterize the humoral immune response at mucosal surfaces. However, the results obtained so far are in part contradictory. For intestinal IgA, reduced, increased and no changes compared to controls were described. The different results may be due to different methods applied. In most studies an abnormal predominance of HIV-specific IgG over IgA response was found in the intestine of HIV-infected patients. Studies on cytomegalovirus-specific intestinal antibodies indicate a complete lack of a specific intestinal IgA response. However, in cryptosporidiosis of HIV-infected patients, diarrhea persists despite a secretory IgA response indicating that other factors are also important for the clearance of this pathogen.

Mucosal HIV infection.

The gastrointestinal tract is not only a major site of clinical manifestations of the acquired immune deficiency syndrome but also an important compartment for HIV infection at all stages of the disease. In intestinal biopsies HIV has been detected so far mainly in mononuclear cells of the lamina propria but also in epithelial cells. Primary and permanent epithelial cell lines can be productively infected by HIV in vitro and epithelial cell monolayers can rapidly transport HIV by transcytosis. Both phenomena are most effective for cell-associated virus and do not require CD4 expression but seem to involve the interaction of gp120 with galactosyl ceramide. In vivo, productive HIV infection of epithelial cells appears to be rare if it occurs at all. Mucosal HIV infection is highly active at all stages of HIV infection and the gastrointestinal tract is probably a major source of HIV in the body. Highest mucosal HIV production is found rather early in HIV disease and is associated with histological abnormalities and gastrointestinal symptoms. The excessive production of HIV in the intestine appears to be due to transcriptional or translational upregulation and local variations in HIV production correlate with local cytokine levels.

Increased immunoglobulin G production by short term cultured duodenal biopsy samples from HIV infected patients.

BACKGROUND: Secretory immunity is a major defence mechanism against infections at mucosal surfaces which are common in HIV infected patients. AIMS: To analyse intestinal immunoglobulin production in HIV infection in comparison with that in saliva and serum. PATIENTS AND METHODS: Immunoglobulin G (IgG), A (IgA), and M (IgM) concentrations were determined in supernatants of short term cultured duodenal biopsy samples, serum, and saliva from HIV infected patients (n = 28) and controls (n = 14) by radial immunodiffusion. RESULTS: IgG was increased in the supernatants of short term cultured biopsy samples and saliva from HIV infected patients compared with controls (p < 0.01), but IgA and IgM levels were normal. In contrast, both IgG and IgA concentrations in serum were higher in HIV infected patients than in controls (p < 0.002). No correlation was found between IgA produced by duodenal biopsy specimens and serum IgA. CONCLUSION: Abnormalities in mucosal immunoglobulin production in HIV infection were surprisingly small, indicating that specific secretory immunity rather than quantitative immunoglobulin production may be impaired. However, increased production of IgG could contribute to mucosal inflammation by complement activation. Our findings of normal mucosal IgA production and the lack of correlation between serum and mucosal IgA argues against an intestinal origin for the increased serum IgA levels in HIV infected patients.

HIV-1 p24 but not proviral load is increased in the intestinal mucosa compared with the peripheral blood in HIV-infected patients.

OBJECTIVE: To investigate differences in viral and proviral load between the peripheral blood and the intestinal mucosal immune system in HIV-infected patients. DESIGN: HIV-1 p24 and HIV DNA content were compared in blood samples and intestinal biopsies from HIV-infected patients. METHODS: Intestinal biopsies and peripheral blood were simultaneously obtained from 27 HIV-infected patients undergoing diagnostic endoscopy. The p24 concentrations were measured in serum and homogenized intestinal biopsies by enzyme-linked immunosorbent assay after acid-dissociation of immune complexes. Proviral load was determined in blood and intestinal biopsies by a quantitative competitive polymerase chain reaction amplifying the HIV-1 nef gene from genomic DNA. RESULTS: No significant differences were found in proviral load comparing HIV copies per 1.5 x 10(5) cell equivalents in blood [2650 (600-44000)] and intestinal biopsies [4200 (1325-19 625)]. Paired analysis revealed a strong positive correlation between serum and mucosal proviral load. In contrast, HIV core protein p24 was detected in intestinal biopsies from 18 patients in much higher concentrations than in serum [858 (262-4111) pg/g versus 34 (9-242) pg/g; P < 0.005]. The p24 concentrations in serum and intestinal biopsies did not correlate and no significant correlation was observed in serum or intestinal biopsies between proviral load and p24 concentrations. No clear correlations were observed between clinical parameters and HIV DNA or HIV p24 levels in blood or biopsies. CONCLUSIONS: Our findings demonstrate a homogenous distribution of HIV proviral load in the peripheral blood and the intestinal mucosal immune system. The high viral antigen load in the intestine therefore indicates that mucosal HIV production is upregulated at the transcriptional and/or translational level. The intestinal mucosa is a major reservoir for HIV in HIV-infected patients.

Abnormal predominance of IgG in HIV-specific antibodies produced by short-term cultured duodenal biopsy specimens from HIV-infected patients.

The aim of our study was to analyze HIV-specific humoral immunity in the intestinal mucosa at different stages of HIV infection in comparison with serum and saliva. Duodenal biopsy specimens from 30 AIDS patients and 9 HIV-infected patients without AIDS were cultured for 48 hours. Culture supernatants, as well as simultaneously obtained serum and saliva samples, were adjusted to the same immunoglobulin concentrations and tested for HIV-specific IgG and IgA by Western blot. The HIV antigen pattern differed clearly between IgA and IgG but was similar for each isotype independent of its origin (i.e., serum, saliva, or biopsy specimen supernatants). Short-term cultured duodenal biopsy specimens from HIV-infected patients at all stages produced predominantly IgG, which was broadly reactive with HIV antigens. Lower titers of HIV-specific IgA, which recognized few antigens, were found, mostly the glycoprotein gp160. At later stages of the disease compared with earlier stages, the reaction pattern of mucosal IgA from saliva and biopsy supernatants was even more restricted; secretory component was frequently absent. The abnormal predominance of HIV-specific IgG over IgA in mucosal secretions may result from abnormal antibody production in the mucosa rather than from serum leakage. Mucosal inflammation induced by HIV-IgG immune complexes and insufficient immune exclusion by secretory IgA may not only lead to increased mucosal HIV replication but may also contribute to gastrointestinal disease in HIV-infected patients.