Immunoglobulin in seminal fluid of fertile, infertile, vasectomy and vasectomy reversal patients

Sperm concentration remains stable among fertile American men: a systematic review and meta-analysis

IMPORTANCE

Findings from several high profile meta-analyses have raised concerns about an ongoing global decline in sperm concentration and male fertility. However, these studies exhibit considerable heterogeneity in key variables including study population, methodology, fertility status, and geographic region.

OBJECTIVE

To perform a systematic review and meta-analysis exploring temporal trends in sperm concentration among fertile men and men unselected for fertility status in the United States.

DATA SOURCES

A literature search performed in Scopus and PubMed databases for studies published between 1970 and 2023. Additional studies were included from citations of prior global meta-analyses and reviews evaluating temporal trends in sperm count.

STUDY SELECTION AND SYNTHESIS

Studies were included if they presented original data on sperm concentration in US men without known infertility from 1970 to 2023. Aggregate data were assessed across all study populations, with additional subgroup analyses stratified by fertility status and US region.

MAIN OUTCOMES

Weighted generalized linear models were generated to evaluate the association between mean sperm concentration and sample collection year.

RESULTS

A total of 874 articles were screened, with 58 meeting the inclusion criteria. These represented 75 unique study populations totaling 11,787 men in the United States. Across all study populations, no change in sperm concentration was observed between 1970 and 2018 in unadjusted models (β = 0.14 million/mL per year). When adjusting for US region, no statistically significant decline in sperm concentration was seen. When adjusting for both region and fertility status, a modest annual decline was observed to meet statistical significance (β = -0.35 million/mL per year). Of the 49 study populations reporting adequate data to determine mean total sperm count, there was a significant increase in total sperm count of 2.9 million per year between 1970 and 2018. Subgroup analysis found no statistically significant change in mean sperm concentration among any US census region or fertility status cohort.

CONCLUSION AND RELEVANCE

In contrast to prior global studies, this analysis suggests no clinically significant decline in sperm concentration among confirmed fertile men and the general male US population without known infertility. Although these findings provide some reassurance against a widespread rapid decline, further studies are necessary to better understand this important topic.

Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries

BACKGROUND

Numerous studies have reported declines in semen quality and other markers of male reproductive health. Our previous meta-analysis reported a significant decrease in sperm concentration (SC) and total sperm count (TSC) among men from North America-Europe-Australia (NEA) based on studies published during 1981-2013. At that time, there were too few studies with data from South/Central America-Asia-Africa (SAA) to reliably estimate trends among men from these continents.

OBJECTIVE AND RATIONALE

The aim of this study was to examine trends in sperm count among men from all continents. The broader implications of a global decline in sperm count, the knowledge gaps left unfilled by our prior analysis and the controversies surrounding this issue warranted an up-to-date meta-analysis.

SEARCH METHODS

We searched PubMed/MEDLINE and EMBASE to identify studies of human SC and TSC published during 2014-2019. After review of 2936 abstracts and 868 full articles, 44 estimates of SC and TSC from 38 studies met the protocol criteria. Data were extracted on semen parameters (SC, TSC, semen volume), collection year and covariates. Combining these new data with data from our previous meta-analysis, the current meta-analysis includes results from 223 studies, yielding 288 estimates based on semen samples collected 1973-2018. Slopes of SC and TSC were estimated as functions of sample collection year using simple linear regression as well as weighted meta-regression. The latter models were adjusted for predetermined covariates and examined for modification by fertility status (unselected by fertility versus fertile), and by two groups of continents: NEA and SAA. These analyses were repeated for data collected post-2000. Multiple sensitivity analyses were conducted to examine assumptions, including linearity.

OUTCOMES

Overall, SC declined appreciably between 1973 and 2018 (slope in the simple linear model: -0.87 million/ml/year, 95% CI: -0.89 to -0.86; P < 0.001). In an adjusted meta-regression model, which included two interaction terms [time × fertility group (P = 0.012) and time × continents (P = 0.058)], declines were seen among unselected men from NEA (-1.27; -1.78 to -0.77; P < 0.001) and unselected men from SAA (-0.65; -1.29 to -0.01; P = 0.045) and fertile men from NEA (-0.50; -1.00 to -0.01; P = 0.046). Among unselected men from all continents, the mean SC declined by 51.6% between 1973 and 2018 (-1.17: -1.66 to -0.68; P < 0.001). The slope for SC among unselected men was steeper in a model restricted to post-2000 data (-1.73: -3.23 to -0.24; P = 0.024) and the percent decline per year doubled, increasing from 1.16% post-1972 to 2.64% post-2000. Results were similar for TSC, with a 62.3% overall decline among unselected men (-4.70 million/year; -6.56 to -2.83; P < 0.001) in the adjusted meta-regression model. All results changed only minimally in multiple sensitivity analyses.

WIDER IMPLICATIONS

This analysis is the first to report a decline in sperm count among unselected men from South/Central America-Asia-Africa, in contrast to our previous meta-analysis that was underpowered to examine those continents. Furthermore, data suggest that this world-wide decline is continuing in the 21st century at an accelerated pace. Research on the causes of this continuing decline and actions to prevent further disruption of male reproductive health are urgently needed.

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.

Temporal trends in sperm count: a systematic review and meta-regression analysis

BACKGROUND

Reported declines in sperm counts remain controversial today and recent trends are unknown. A definitive meta-analysis is critical given the predictive value of sperm count for fertility, morbidity and mortality.

OBJECTIVE AND RATIONALE

To provide a systematic review and meta-regression analysis of recent trends in sperm counts as measured by sperm concentration (SC) and total sperm count (TSC), and their modification by fertility and geographic group.

SEARCH METHODS

PubMed/MEDLINE and EMBASE were searched for English language studies of human SC published in 1981-2013. Following a predefined protocol 7518 abstracts were screened and 2510 full articles reporting primary data on SC were reviewed. A total of 244 estimates of SC and TSC from 185 studies of 42 935 men who provided semen samples in 1973-2011 were extracted for meta-regression analysis, as well as information on years of sample collection and covariates [fertility group ('Unselected by fertility' versus 'Fertile'), geographic group ('Western', including North America, Europe Australia and New Zealand versus 'Other', including South America, Asia and Africa), age, ejaculation abstinence time, semen collection method, method of measuring SC and semen volume, exclusion criteria and indicators of completeness of covariate data]. The slopes of SC and TSC were estimated as functions of sample collection year using both simple linear regression and weighted meta-regression models and the latter were adjusted for pre-determined covariates and modification by fertility and geographic group. Assumptions were examined using multiple sensitivity analyses and nonlinear models.

OUTCOMES

SC declined significantly between 1973 and 2011 (slope in unadjusted simple regression models -0.70 million/ml/year; 95% CI: -0.72 to -0.69; P < 0.001; slope in adjusted meta-regression models = -0.64; -1.06 to -0.22; P = 0.003). The slopes in the meta-regression model were modified by fertility (P for interaction = 0.064) and geographic group (P for interaction = 0.027). There was a significant decline in SC between 1973 and 2011 among Unselected Western (-1.38; -2.02 to -0.74; P < 0.001) and among Fertile Western (-0.68; -1.31 to -0.05; P = 0.033), while no significant trends were seen among Unselected Other and Fertile Other. Among Unselected Western studies, the mean SC declined, on average, 1.4% per year with an overall decline of 52.4% between 1973 and 2011. Trends for TSC and SC were similar, with a steep decline among Unselected Western (-5.33 million/year, -7.56 to -3.11; P < 0.001), corresponding to an average decline in mean TSC of 1.6% per year and overall decline of 59.3%. Results changed minimally in multiple sensitivity analyses, and there was no statistical support for the use of a nonlinear model. In a model restricted to data post-1995, the slope both for SC and TSC among Unselected Western was similar to that for the entire period (-2.06 million/ml, -3.38 to -0.74; P = 0.004 and -8.12 million, -13.73 to -2.51, P = 0.006, respectively).

WIDER IMPLICATIONS

This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50-60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand. Because of the significant public health implications of these results, research on the causes of this continuing decline is urgently needed.

Changes in fucosylation of human seminal IgG and secretory component of IgA in leukocytospermic patients

Our study compares the status of human seminal plasma immunoglobulin G (IgG) and IgA secretory component (SC) fucosylation between infertile leukocytospermic and normal, fertile normozoospermic patients. The seminal IgG and SC are decorated with AAL-reactive core fucose, and antennary UEA- and LTA-reactive fucose of Lewis^y and Lewis^x structures, respectively. However, a correlation between IgG core fucosylation and IgG concentration (r = −0.52; p < 0.0003) was observed. The IgG present in leukocytospermic samples is characterized by lower expression of core fucose than in the normal group (0.82 ± 0.3 AU and 1.2 ± 0.3 AU, respectively; p < 0.002). In seminal plasma the SC is present in two forms: 78-kDa and 63-kDa. The present study has also shown a higher AAL and LTA specific reactivity of glycans expressed in 63-kDa SC, in comparison to 78-kDa SC, in the normal group. In leukocytospermia, the values of specific lectin reactivity for core fucose, fucose α(1-2)- and α(1-3)- linked, were similar for both SC bands. Moreover, the present study has shown that in leukocytospermic samples the mean concentrations of IgG and S-IgA are twice as high (131.68 ± 102.6 mg/l and 36 ± 27 mg/l, respectively) as in the normal group (67.68 ± 29.2 mg/l; p < 0.02, and 19 ± 18 mg/l, p < 0.019, respectively). The analysis of IgG and SC fucosylation status and the determination of IgG and S-IgA concentrations in seminal plasma might constitute a valuable diagnosis tools for the evaluation of male infertility associated with leukocytospermia with accompanying inflammation.

Human Male Genital Tract Secretions: Both Mucosal and Systemic Immune Compartments Contribute to the Humoral Immunity

In contrast to numerous studies of female genital tract secretions, the molecular properties of Abs and the magnitude of humoral responses in human male genital tract secretions to naturally occurring Ags and to mucosal and systemic immunizations have not been extensively investigated. Therefore, seminal plasma (SP) collected from healthy individuals was analyzed with respect to Ig levels, their isotypes, molecular forms of IgA, and for the presence of Abs to naturally occurring Ags, or induced by systemic or mucosal immunizations with viral and bacterial vaccines. The results indicated that in SP, IgG and not IgA, is the dominant Ig isotype, and that IgM is present at low levels. IgA is represented by secretory IgA, polymeric IgA, and monomeric IgA. In contrast to the female genital tract secretions in which IgA2 occurs in slight excess, the distribution of IgA subclasses in SP resembles that in plasma with a pronounced preponderance of IgA1. The IgG subclass profiles in SP are also similar to those in serum. Thus, SP is an external secretion that shares common features with both typical external secretions and plasma. Specifically, SP contains naturally occurring secretory IgA Abs to environmental Ags of microbial origin and to an orally administered bacterial vaccine, and plasma-derived IgG Abs to systemically injected vaccines. Therefore, both mucosal and systemic immunization with various types of Ags can induce humoral responses in SP. These findings should be considered in immunization strategies to induce humoral responses against sexually transmitted infections, including HIV-1.

Measurement of immunoglobulin G, A and M concentrations in boar seminal plasma

How the immune system relates to the boar reproductive tract is not well defined. This is an important area of study because disease-causing agents may be transmitted through boar semen. We have previously identified porcine reproductive and respiratory syndrome virus (PRRSV) in boar semen and wanted to identify PRRSV-specific antibodies within seminal plasma. However, literature documenting total immunoglobulin concentration or the predominant immunoglobulin isotype in boar semen was not available. Therefore, we developed a sandwich enzyme-linked immunoassay (ELISA) to quantitate total IgG, IgA and IgM in seminal plasma from 16 healthy, nonvaccinated, adult boars (n = 102 semen samples). In seminal plasma, IgG was the predominant isotype followed by IgA and IgM. Mean levels +/- the standard deviation followed by the 95% confidence interval of IgG, IgA and IgM were 23.2 +/- 14 microg/mL (15.5 to 31.0), 4.8 +/- 2.5 microg/mL (3.5 to 6.2) and 3.7 +/- 1.7 microg/mL (2.7 to 4.7), respectively. These concentrations of immunoglobulins in seminal plasma were considerably lower than in other swine secretions, which might allow for the survival of infectious agents in boar semen.

Mucosal immune system of the human genital tract

In contrast to the pronounced dominance of secretory IgA over other immunoglobulin isotypes in human saliva, tears, milk, and gastrointestinal fluids, secretions of both female and male genital tracts contain more IgG than secretory IgA. Both IgG and IgA are derived, to a variable degree, from the systemic immunoglobulin pool as well as from local synthesis. The origin of IgG- and IgA-plasma cell precursors destined for the genital tract is unknown, but indirect evidence suggests that mucosal inductive sites localized in the rectum, small intestine, and especially in the nasal cavity contribute such precursors to the female genital tract. Several studies indicated that intranasal immunization of various species, including humans, was efficient at inducing antigen-specific antibody responses in the female genital tract; however, whether this route is also effective in males has not been explored.

Fertility of brushtail possums (Trichosurus vulpecula) immunised against sperm

The brushtail possum (Trichosurus vulpecula) is a major pest species in New Zealand. Research to develop a possum-specific method of immunologically-based fertility control (immunocontraception) has begun. This study examined the effect of immunization against sperm on the fertility of possums. Possums were assigned to 16 mating groups (two females and one male per group) before the start of the breeding season. One female in each group and eight males were injected subcutaneously with 5 x 10(7) sperm in complete Freund's adjuvant. Animals were given booster injections containing 5 x 10(7) sperm in incomplete Freund's adjuvant 4 and 12 weeks later. Control animals received adjuvants emulsified with phosphate buffered saline. Serum and sperm samples were collected monthly and the number of offspring recorded. Reproductive tract samples were collected from eight immunized and eight control possums of each sex at the end of the breeding season. Samples were screened for sperm antibody binding by an indirect possum sperm ELISA. Increased sperm antibody binding was detected in sera of 22 (15 females and seven males) of the 24 animals immunized against sperm. Immunization significantly reduced the proportion of females producing offspring (2/16 immunized versus 12/16 control) but had no effect on the fertility of males. Immunization increased sperm antibody binding activity in vaginal secretions of female and in prostatic tissue of male possums. Results indicate that there are antigens in possum sperm with immunocontraceptive potential for possum control.

The importance of mucosal immunology to problems in human reproduction

The field of mucosal immunology is making rapid advances towards establishing the molecular basis of mucosal defense mechanisms and the development of mucosal vaccines. Research on the mucosal immunology of male and female reproductive tract tissues is benefiting from these advances, as well as from current investigations on specialized immunologic features of the reproductive tract. This knowledge may soon be applicable to solutions for many important problems concerning human reproduction, such as fertility regulation and the current epidemic of sexually transmitted diseases, including AIDS.

The natural anti-alpha-galactosyl IgG in seminal fluid. A simple means to determine damage to the blood-genital tract barrier in infertile males

A simple method for detecting damage to the blood genital tract barrier (BGTB) is presented. The method is based on the ubiquitous presence of the natural anti-alpha-galactosyl (anti-Gal) IgG antibodies in high titers in the serum of every normal individual, and the interaction between this antibody and alpha-galactosyl residues on rabbit red blood cells (RabRBC). The binding of the anti-Gal antibodies to RabRBC could be demonstrated by the rosetting antiglobulin test. The seminal fluid (SF), normally compartmentalized from the blood, is devoid of anti-Gal reactivity. The SF of a large proportion of infertile males contained significant anti-Gal reactivity, implying transudation of serum IgG molecules probably due to damage in the selective permeability of the BGTB. The diagnostic potential of this assay is discussed.

Injury to the pre-pubertal vas deferens. II. Experimental repair

We have previously shown that the human vas deferens does not change in cross-sectional size between birth and the middle of puberty. This suggests that if the human vas is injured prior to mid-puberty, repair by a traditional microsurgical vasovasostomy may be technically difficult. We propose that a chromic stent can be used to assist in the repair of vas injured before mid-puberty. This hypothesis was tested in Sprague-Dawley rats. At three weeks of age, male offspring were divided into three groups (eight to nine rats/group): 1) Sham group--a sham operation at three weeks, 2) VV group--bilateral transection of vasa at three weeks followed by a delayed repair at eight weeks by microsurgical vasovasostomy without a stent, 3) Stent group--bilateral transection of vasa at three weeks followed by immediate repair by aligning the lumens with a 6-0 chromic intravasal stent (suture) and holding the transected ends together with several seromuscular sutures. At four months all rats were fertility tested and a score was given to each rat (mean number of concepti among three females for each male rat). Analysis of anastomotic patency by flow rates and histology was performed. There was no statistical difference in the mean fertility score of 6.85 in the Stent group compared to 7.83 in the Sham group. However, a fertility score of 0.71 in the VV group was significantly decreased compared to the Stent and Sham group (p = .0003), despite no statistical difference between the groups in patency. This suggests that a recognized injury to the pre-pubertal human vas should be immediately repaired and the repair can be done using 6-0 chromic suture as an intravasal stent to help align the lumina of the smaller pre-pubertal vas.

Antispermatozoal antibodies in three men with infertility due to congenital aplasia of the vasa deferentia

Men presenting with azoospermia due to aplasia of the vas deferens have commonly been considered to be infertile without hope of treatment. With improved methods of artificial insemination however, and more particularly with the advent of in vitro fertilization, it has been suggested that unusable spermatozoa may be able to be drawn from the epididymes of such men so that fertilization is achieved. The clinical situation of such men is analogous to that of long term vasectomised patients, 60% of whom are known to produce antibodies to spermatozoa which would interfere with the fertilization process. It was therefore decided to attempt to draw fluid from the epididymes of three such patients and at the same time conduct immunological studies on their sera, seminal fluid and, where available, epididymal fluid. Unfortunately, the spermatozoa obtained from all three men lacked sufficient progressive motility for use in in vitro fertilization. In addition, all men had antispermatozoal antibodies in their sera. Two of them also had antispermatozoal antibodies in their epididymal fluid and on their sperm, one at the same titer as in his serum. Since it is known that antibodies coating sperm reduce the changes of fertilization it is suggested that their presence should be assessed in all such men being considered for treatment. In addition, these studies demonstrate that antispermatozoal antibodies can enter the male tract at the level of the epididymis or higher and there were strong suggestions of local antibody production at this level in the tract.

Quantitative pathologic changes in the human testis after vasectomy. A controlled study

To determine whether there are any deleterious changes in the human testis after vasectomy, we obtained testicular biopsy specimens from 31 healthy men undergoing vasectomy reversal and from 21 healthy, fertile volunteers. Morphometric analyses of these specimens revealed a 100 per cent increase in the thickness of the seminiferous tubular walls (P less than 0.001), a 50 per cent increase in the mean cross-sectional tubular area (P less than 0.001), and a significant reduction in the mean number of Sertoli cells (P less than 0.01) and spermatids (P less than 0.01) per tubular cross section in the post-vasectomy group, as compared with the control group. Focal interstitial fibrosis was observed in 23 per cent of the specimens from the post-vasectomy group and in none from the control group. There was a significant correlation (P less than 0.01) between interstitial fibrosis and infertility in patients who underwent a surgically successful vasectomy reversal (sperm in the ejaculate). None of the other measured characteristics correlated with infertility after vasectomy reversal. We conclude that significant morphologic changes occur in the human testis after vasectomy. The presence of focal interstitial fibrosis was associated with a high incidence of infertility in this series.

Immunological studies on seminal plasma proteins of the Indian buffalo and cattle

Seminal plasma proteins of the Indian buffalo and cattle were immunologically investigated using rabbit antibuffalo seminal plasma serum, rabbit anticattle seminal plasma serum (unabsorbed and absorbed), gel diffusion, and immunoelectrophoretic analysis. At least 9-12 and 7-10 different proteins, respectively, were present in the seminal plasma of the buffalo and cattle. Albumin and IgG were identified in both the species. At least 4-6 seminal plasma proteins of the buffalo and cattle were antigenically similar to their blood serum proteins. Using absorbed rabbit antibuffalo seminal plasma serum and rabbit anticattle seminal plasma serum, at least 6-7 and 5-6 seminal plasma specific proteins, respectively, were observed in the buffalo and cattle seminal plasma. Antigenically these proteins were different from the blood serum proteins of these two species. The origin and biological significance of seminal plasma proteins are discussed.

Seminal plasma immunoglobulins of the Indian buffalo

Seminal plasma immunoglobulins of normospermic fertile Indian buffalo bulls were investigated using rabbit antibuffalo immunoglobulin (polyvalent) serum, rabbit antibuffalo IgG and IgM serums, gel diffusion, and immunoelectrophoretic analysis. Immunoglobulin G was the predominant immunoglobulin in the seminal plasma of the buffalo. Strong antigenic cross reactions were observed between the seminal plasma IgG molecules of the buffalo and cattle, indicating the structural homology of seminal plasma IgG of these two species. These observations are in accordance with the close taxonomic and phylogenetic relationship between buffalo and cattle in the evolution of ruminant species.