Diffusion of macromolecules and virus-like particles in human cervical mucus.

To determine whether or not large macromolecules and viruses can diffuse through mucus, we observed the motion of proteins, microspheres, and viruses in fresh samples of human cervical mucus using fluorescent recovery after photobleaching and multiple image photography. Two capsid virus-like particles, human papilloma virus (55 nm, approximately 20,000 kDa) and Norwalk virus (38 nm, approximately 10,000 kDa), as well as most of the globular proteins tested (15-650 kDa) diffused as rapidly in mucus as in saline. Electron microscopy of cervical mucus confirmed that the mesh spacing between mucin fibers is large enough (20-200 nm) for small viruses to diffuse essentially unhindered through mucus. In contrast, herpes simplex virus (180 nm) colocalized with strands of thick mucus, suggesting that herpes simplex virus, unlike the capsid virus particles, makes low-affinity bonds with mucins. Polystyrene microspheres (59-1000 nm) bound more tightly to mucins, bundling them into thick cables. Although immunoglobulins are too small to be slowed by the mesh spacing between mucins, diffusion by IgM was slowed by mucus. Diffusion by IgM-Fc(5 mu), the Fc pentamer core of an IgM with all 10 Fab moieties removed, was comparably slowed by mucus. This suggests that the Fc moieties of antibodies make low-affinity bonds with mucins.

Origins of vaginal acidity: high D/L lactate ratio is consistent with bacteria being the primary source.

BACKGROUND: The origin of the lactic acid that acidifies the vagina is not well established. It is widely accepted that during times of high oestrogen (during the neonatal period and again during a woman's reproductive years) large amounts of glycogen are deposited in the vaginal epithelium and that the glycogen is anaerobically metabolized to lactic acid. What is not established is whether lactic acid is primarily produced by vaginal bacteria or by vaginal epithelial cells. Human cells can make only L-lactate, while bacteria can produce both D- and L-, thus the D- to L-lactate ratio can indicate the relative contribution of bacterially derived lactic acid. METHODS: In this study, we used chiral HPLC to examine the percentages of D- and L-lactate in vaginal secretions, in primary cultures of bacteria from these vaginal secretions, and in cultures of lactobacillus isolates of vaginal origin. RESULTS: We found that in most vaginal secretion samples, >50% of the lactic acid was the D-isoform (mean 55%, range 6-75%, n = 14). CONCLUSIONS: Our results thus support the hypothesis that vaginal bacteria, not epithelial cells, are the primary source of lactic acid in the vagina.

Tests of Buffergel for contraception and prevention of sexually transmitted diseases in animal models.

BACKGROUND: BufferGel is a novel spermicidal and microbicidal gel formulated to maintain the natural protective acidity of the vagina by acidifying semen, which otherwise alkalinizes the vagina. GOAL: To test the efficacy of BufferGel for preventing sexually transmitted infections and pregnancy in animal models. STUDY DESIGN: Animals were challenged with pathogens or sperm after pretreatment with both test and control agents, or after no pretreatment, then evaluated for infection or pregnancy using standard methods. RESULTS: BufferGel provided significant contraceptive efficacy in the rabbit, and significant protection against vaginal and rectal transmission of herpes simplex virus type 2 (HSV-2) in the mouse, vaginal transmission of Chlamydia trachomatis in the mouse, and skin transmission of cottontail rabbit papillomavirus in the rabbit. It did not protect against vaginal transmission of Neisseria gonorrhoeae in the mouse. CONCLUSIONS: The protective efficacy of BufferGel in five of the six animal models suggests that this microbicide warrants clinical evaluation for both contraception and disease prevention.

Preventing infectious disease with passive immunization.

Antibodies can prevent infectious diseases by providing passive immune protection. Here we review successful clinical trials of passive immunization and consider some of the unique qualities monoclonal antibodies are now beginning to offer for developing methods for passive immunization against a wide range of infectious diseases.

The rate at which human sperm are immobilized and killed by mild acidity.

OBJECTIVE: To determine the rate at which mild acidity immobilizes and kills human sperm and to evaluate an acidic microbicide, BufferGel, for sperm immobilization. DESIGN: Controlled in vitro study. SETTING: An academic research university and hospital andrology lab. PATIENT(S): Eight volunteer male sperm donors. INTERVENTION(S): Semen samples were treated with hydrochloric acid (HCl) or BufferGel. MAIN OUTCOME MEASURE(S): Sperm motility was measured by using a computerized automated semen analyzer and video microscopy. Sperm membrane permeability and intracellular pH were measured by using fluorescent techniques. RESULT(S): In semen acidified with HCl to pH 4.0, sperm were rapidly immobilized (within 1 min) and were irreversibly immobilized (killed) within 10 minutes. The speed of immobilization and of killing were both linearly proportional to hydrogen ion activity over a pH range of 7.5-4.0. Across the same range, the intracellular pH of human sperm equilibrated to within 0.5 pH units of extracellular pH within 1-2 minutes. BufferGel immobilized sperm significantly faster than HCl from pH 4.0-6.0. CONCLUSION(S): Exposure to mild acidity rapidly acidifies the intracellular pH of human sperm and is rapidly spermicidal. BufferGel accelerates acid immobilization of sperm.

Acid production by vaginal flora in vitro is consistent with the rate and extent of vaginal acidification.

Perinatally, and between menarche and menopause, increased levels of estrogen cause large amounts of glycogen to be deposited in the vaginal epithelium. During these times, the anaerobic metabolism of the glycogen, by the epithelial cells themselves and/or by vaginal flora, causes the vagina to become acidic (pH approximately 4). This study was designed to test whether the characteristics of acid production by vaginal flora in vitro can account for vaginal acidity. Eight vaginal Lactobacillus isolates from four species-L. gasseri, L. vaginalis, L. crispatus, and L. jensenii-acidified their growth medium to an asymptotic pH (3.2 to 4.8) that matches the range seen in the Lactobacillus-dominated human vagina (pH 3.6 to 4.5 in most women) (B. Andersch, L. Forssman, K. Lincoln, and P. Torstensson, Gynecol. Obstet. Investig. 21:19-25, 1986; L. Cohen, Br. J. Vener. Dis. 45:241-246, 1969; J. Paavonen, Scand. J. Infect. Dis. Suppl. 40:31-35, 1983; C. Tevi-Bénissan, L. Bélec, M. Lévy, V. Schneider-Fauveau, A. Si Mohamed, M.-C. Hallouin, M. Matta, and G. Grésenguet, Clin. Diagn. Lab. Immunol. 4:367-374, 1997). During exponential growth, all of these Lactobacillus species acidified their growth medium at rates on the order of 10(6) protons/bacterium/s. Such rates, combined with an estimate of the total number of lactobacilli in the vagina, suggest that vaginal lactobacilli could reacidify the vagina at the rate observed postcoitally following neutralization by the male ejaculate (W. H. Masters and V. E. Johnson, Human sexual response, p. 93, 1966). During bacterial vaginosis (BV), there is a loss of vaginal acidity, and the vaginal pH rises to >4.5. This correlates with a loss of lactobacilli and an overgrowth of diverse bacteria. Three BV-associated bacteria, Gardnerella vaginalis, Prevotella bivia, and Peptostreptococcus anaerobius, acidified their growth medium to an asymptotic pH (4.7 to 6.0) consistent with the characteristic elevated vaginal pH associated with BV. Together, these observations are consistent with vaginal flora, rather than epithelial cells, playing a primary role in creating the acidity of the vagina.

A humanized monoclonal antibody produced in transgenic plants for immunoprotection of the vagina against genital herpes.

The ability to produce monoclonal antibodies (Mabs) in plants offers the opportunity for the development of an inexpensive method of mucosal immunoprotection against sexually transmitted diseases. To investigate the suitability of plant-expressed Mabs for vaginal preventive applications, we compared a humanized anti-herpes simplex virus 2 (HSV-2) Mab expressed in mammalian cell culture with the same antibody expressed in soybean. We found these Mabs to be similar in their stability in human semen and cervical mucus over 24 h, their ability to diffuse in human cervical mucus, and their efficacy for prevention of vaginal HSV-2 infection in the mouse.

Comparison of an anti-HSV-2 monoclonal IgG and its IgA switch variant for topical immunoprotection of the mouse vagina.

An IgG2a monoclonal antibody (Mab) directed against glycoprotein D of herpes simplex virus 2 (HSV-2) was compared with an IgA heavy chain Mab switch variant to investigate the effect of isotype for topical immunoprotection of the murine vagina. The IgA Mab, a mixture of monomeric and polymeric IgA, was indistinguishable from its IgG parent in an in vitro HSV-2 neutralization assay. When these class switched Mabs were delivered to the mouse vagina, we also found no significant difference between the IgG and IgA for preventing vaginal transmission of HSV-2 infection. The implications of these results for active and passive immunization strategies against vaginal transmission of genital herpes infections are discussed.

Contraceptive effect of sperm-agglutinating monoclonal antibodies in rabbits.

Immune infertility in humans correlates clinically with the presence of anti-sperm antibodies that trap (agglutinate) sperm in semen and cervical mucus. To test whether sperm-agglutinating antibodies can be effective contraceptive agents, several mouse anti-rabbit sperm (MARS) sperm-agglutinating monoclonal antibodies (mAbs) were developed that rapidly and completely agglutinate sperm: MARS-M3 (IgM), MARS-G16 (IgG3), and MARS-G17 (IgG3). Contraceptive efficacy of these mAbs was tested by mixing the mAb with 0.1 ml semen (approximately 1/5 of a whole ejaculate) immediately before artificially inseminating rabbits paracervically. This paracervical dose of semen provided a rigorous test since it delivered several thousand times more fertilizing doses than does a human ejaculate. All of the mAbs were contraceptively effective, and MARS-G16 reduced the number of fetuses per animal by 88% and 95% with doses of 150 microg and 2 mg, respectively. The contraceptive efficacy of the MARS mAbs in the rabbit suggests that human sperm-agglutinating mAbs may be effective agents for vaginal contraception in humans.

Tests of vaginal microbicides in the mouse genital herpes model.

Microbicide candidates were selected that have demonstrated activity against sperm or sexually transmitted disease pathogens in vitro, and the efficacy of these agents for preventing vaginal transmission of genital herpes infection was evaluated in the progestin-treated mouse. Each agent was delivered to the vaginas of mice approximately 20 sec prior to delivering a highly infectious herpes simplex virus-2 inoculum. The following agents provided significant protection: anti-HSV monoclonal antibodies III-174 and HSV8, modified bovine beta-lactoglobulin (beta-69), carrageenan, concanavalin A, chlorhexidine, dextran sulfate (average molecular weight 8,000 and 500,000), fucoidan, neem, nonoxynol-9, polystyrene sulfonate, and povidone-iodine. Two agents, gramicidin and heparan sulfate, though highly effective in vitro, were not protective in vivo at the doses tested.

Genes for chemokines MuMig and Crg-2 are induced in protozoan and viral infections in response to IFN-gamma with patterns of tissue expression that suggest nonredundant roles in vivo.

MuMig and Crg-2 are IFN-inducible murine chemokines whose human homologues, HuMig and IP-10, respectively, share activity in vitro as T cell chemoattractants. We analyzed the expression of the genes Mumig, crg-2, and IFN-gamma during experimental infections with Plasmodium yoelii, Toxoplasma gondii, and vaccinia virus. Mumig, crg-2, and IFN-gamma were induced in multiple organs. During the acute phase of each infection as well as after i.p. injection of rIFN-gamma, levels of Mumig mRNA in the liver were as high or higher than levels in any of the other organs. In contrast, the organs showing the highest expression of crg-2 and IFN-gamma varied among the experimental models, with induction of these latter two genes colocalizing. Differences in relative levels of expression of Mumig and crg-2 in liver and spleen were not demonstrably due to expression of the genes in different cell types within these organs. We showed that both Mumig and crg-2 are induced in the liver in hepatocytes and in the spleen in CD11b+ cells. IFN-gamma was necessary for induction of Mumig during infections with T. gondii or vaccinia virus. In contrast, induction of crg-2 was not completely dependent on IFN-gamma. These data demonstrate that despite the overlap in activities within chemokine subsets, chemokine genes show differences in their patterns of expression and in their responses to inducers that suggest nonredundant roles in vivo. Moreover, the pattern of induction of crg-2 is consistent with Crg-2 acting primarily locally, while the pattern for Mumig induction suggests that MuMig may have a systemic role during infection.

Topically applied human recombinant monoclonal IgG1 antibody and its Fab and F(ab')2 fragments protect mice from vaginal transmission of HSV-2.

A recombinant human anti-herpes simplex virus monoclonal IgG1, antibody and the corresponding Fab and F(ab')2 fragments were tested for efficacy in preventing vaginal transmission of HSV-2 infection in a well-established mouse model for genital herpes. IgG1, Fab, and F(ab')2 were approximately equally protective; vaginal delivery of 1-5 ng provided approximately 50% protection, and vaginal delivery of 400 ng completely protected mice from genital herpes infection (P < 0.001). These results suggest that topical applications of human monoclonal antibodies may be useful in developing new methods for preventing sexually transmitted disease.

Brain endothelial cell infection in children with acute fatal measles.

Neurologic diseases are important complications of measles. The role of virus infection of the central nervous system as well as the route of virus entry has been unclear. Five autopsied cases of individuals who died with severe acute measles 3-10 d after the onset of the rash were studied for evidence of viral involvement of the central nervous system. In all cases, in situ hybridization and RT-PCR in situ hybridization techniques showed endothelial cell infection. Immunoperoxidase staining with an anti-ferritin antibody revealed a reactive microgliosis. These data suggest that endothelial cells in the brain are frequently infected during acute fatal measles. This site of infection may provide a portal of entry for virus in individuals who subsequently develop subacute sclerosing panencephalitis or measles inclusion body encephalitis and a target for immunologic reactions in post-measles encephalomyelitis.

Infection of monocytes during measles.

Immune suppression has long been recognized to be a consequence of measles and a likely contributor to the secondary complications of this infection. Since measles virus can be isolated from peripheral blood leukocytes during the early phases of infection, it has been widely assumed that measles virus suppresses the immune system by replicating in and damaging T lymphocytes. A reverse transcriptase-polymerase chain reaction (RT-PCR) assay able to detect wild-type strains of measles virus was applied to the study of peripheral blood mononuclear cells (PBMC) during natural measles virus infection. Measles virus RNA was detected by RT-PCR in monocyte-enriched adherent cells up to 6 days after the appearance of the rash. No viral RNA was detected in the lymphocyte-enriched nonadherent cell fraction. The numbers of virus-infected PBMC detected by in situ hybridization ranged from 1 in 125 to 1 in 2500. Dual staining identified infected cells as monocytes. It is concluded that the primary leukocytes infected during measles are monocytes, not lymphocytes. This cellular tropism has implications for understanding the immune suppression associated with measles.

The cat/feline immunodeficiency virus model for transmucosal transmission of AIDS: nonoxynol-9 contraceptive jelly blocks transmission by an infected cell inoculum.

OBJECTIVES: To develop an animal model to study transmucosal lentivirus transmission, and to determine whether topical application of contraceptive jelly can block transmission by an infected cell incoulum. DESIGN: Feline immunodeficiency virus (FIV), a lentivirus similar to HIV, causes an AIDS-like disease in domestic cats. HIV is transmitted primarily across mucosal surfaces, and infected cells may be important in this transmission. We tested the ability of FIV-infected cells to transmit infection across the vaginal, rectal and oral mucosa of the cat, and whether a vaginal contraceptive jelly could prevent such transmission. METHODS: An inoculum consisting of 2 million FIV-infected primary cat T cells was administered vaginally, rectally or orally to female cats that had received either no pretreatment or pretreatment with a contraceptive jelly containing the detergent nonoxynol-9 as spermicide. Transmission was detected by monitoring recipient animals for viral antibodies and by viral cultures of blood leukocytes. RESULTS: A single dose of the infected cell inoculum efficiently transmitted FIV infection when delivered into the vagina or rectum (10 out of 11 animals became infected). Pretreatment of the vagina (five animals) or rectum (four animals) with contraceptive jelly protected all animals from transmission by the highly infectious inoculum. CONCLUSIONS: The cat/FIV model provides an efficient means to study transmucosal transmission of lentivirus infections, and for assessing vaginal barrier methods that could block transmission. One such method, nonoxynol-9 contraceptive jelly, effectively prevents transmucosal transmission by an FIV-infected cell inoculum.

Borna disease virus replicates in astrocytes, Schwann cells and ependymal cells in persistently infected rats: location of viral genomic and messenger RNAs by in situ hybridization.

Borna disease (BD) is an immune-mediated neurological disease caused by infection of the nervous system with a negative strand RNA virus, Borna disease virus (BDV). The host range for BDV is broad and extends from birds to primates. A BDV-like agent may cause disease in humans. Until recently, BDV-infected neural cells could only be identified immunocytochemically using serum from BDV-infected animals. The advent of BDV cDNA clones allowed definition of the relationship between viral nucleic acids and viral proteins in vivo. In situ hybridization with strand-specific RNA probes from a BDV cDNA clone, pAF4, identified BDV genomic RNA and BDV mRNAs in neurons, astrocytes, Schwann cells and ependymal cells in an anatomic distribution consistent with that of BDV proteins. Genomic RNA was contained primarily within the nucleus, whereas mRNAs were found in both the nuclear and cytoplasmic compartments. Viral RNAs were demonstrated in neurons expressing BDV proteins and in glial cells by combined techniques of immunocytochemistry and in situ hybridization.

Characterization of the local and systemic B cell response of normal and athymic nude mice with Sindbis virus encephalitis.

During Sindbis virus (SV) encephalitis in mice B cells are an important component of the mononuclear inflammatory response and recovery depends primarily on the development of antiviral antibody. To begin to characterize various parameters of the local B cell response during SV encephalitis we have defined B cell isotype expression in brain sections, splenocytes and peripheral blood mononuclear cells (PBMC) in normal and athymic nude mice using an immunoperoxidase technique. Early (days 3-5) in SV encephalitis brain perivascular B cells are IgM or IgM/IgD-bearing lymphocytes, later (days 10-14) most B cells express one of the IgG isotypes or IgA. The pattern of isotype expression seen in the brain during the course of the encephalitis is reflected in the spleen and blood. The data suggest that progressive isotype switching results in an increasingly higher percentage of certain isotypes, especially IgG2a. Isotype switching of most B cells may occur outside of the brain, or may arise in situ from the IgM/IgD-bearing B cells found in the brain throughout the course of encephalitis. In athymic nude mice numbers of B cells in brain were markedly decreased and the cells present were primarily IgM-bearing, although IgG isotypes and IgA did appear late (day 14). The data suggest that T cells are required for recruitment of B cells into the inflammatory response as well as for normal isotype switching and peripheral B cell maturation during SV encephalitis.

Epidemiologic observations on feline immunodeficiency virus and Toxoplasma gondii coinfection in cats in Baltimore, Md.

Five hundred eighty-five serum samples obtained between 1980 and 1981 from a diverse population of cats were tested by use of an indirect immunoperoxidase assay for antibodies to feline immunodeficiency virus (FIV). Results of 14 of the samples were positive (prevalence, 2.4%). The FIV-positive cats were markedly older than the overall population and frequently were coinfected (57%) with Toxoplasma gondii. The Toxoplasma titers of the FIV-positive cats were significantly (P less than 0.03) higher than those of the FIV-negative cats. The FIV-positive cats were not coinfected with FeLV. Our findings suggested that FIV-associated immunosuppression may be a factor in active Toxoplasma infection in adult cats.