Male and Couple Fertility Impairment due to HPV-DNA Sperm Infection: Update on Molecular Mechanism and Clinical Impact—Systematic Review

Table 4

Data about studies analyzing exogenous sperm HPV-DNA vehicle and its impact on product of conception.

Authors (year)	Number of samples	Aim of the study	Study setting	Main outcomes	Conclusions
Chan et al. (1994) [35]	42	Detect presence of HPV-DNA 16/18 in sperm cells	HPV-DNA detection trough PCR	HPV-DNA detection (PCR): HPV 16: 64.3%; HPV 18: 38.1%; HPV L1: 35.7%	(i) The study demonstrated the presence of HPV-DNA in sperm cells; (ii) The result suggest a possible role of sperm as a vector for HPV
Lai et al. (1997) [36]	24	Detect presence of HPV-DNA 16/18 in both seminal plasma and sperm cells	HPV-DNA detection trough PCR	HPV-DNA detection (PCR): HPV 16: 33.3% (8.3% seminal plasma; 25% sperm cells); HPV 18: 79.1% (33.3% seminal plasma, 45.8% sperm cells)	(i) HPV can infect both sperm cell and seminal plasma; (ii) HPV-DNA 16 and 18 are expressed actively in infected sperm cells; (iii) The HPV infected sperm cells can behave as vectors for the transmission of HPV to fetuses through fertilized eggs
Chan et al. (1996) [37]	—	Demonstrate that sperm cells transfected with HPV-DNA 16/18 can vehicle viral genome to cells of uterus and embryo	(i) Non-human (mouse) experimental study; (ii) HPV-DNA detection trough PCR	(i) Blastocyst took-up HPV-DNA fragments from both HPV-DNA 16 and HPV-DNA 18 of carrier sperm; (ii) The sperm cells transferred HPV-DNA18 but not 16 fragments to the uterine cells at both the cervical-uterine end and the uterine-tubal end	(i) It is possible to apply the transmission of HPV DNA from the sperm to the embryos and cells of the reproductive tract; (ii) The study suggests sperm as a vector for the transmission of DNA to the developing embryo
Cabrera et al. (1997)	—	Demonstrate that exogenous HPV-DNA taken into blastocysts is localized to both the inner cell mass and trophoblast cells	(i) Non-human (mouse) experimental study; (ii) Mouse blastocysts exposed to migrating human sperm cells carrying exogenous DNA fragments from HPV 16 and 18; (iii) HPV-DNA detection trough PCR	Mouse blastocysts transfected by carrier sperm with HPV-DNA 16 and 18 showed localization of the HPV- DNA to both the inner cell mass and trophoblast cells	(i) Exogenous DNA taken into blastocysts is localized to both the inner cell mass and trophoblast cells; (ii) Only live sperm exhibited the capacity to carry various sizes of exogenous DNA, suggesting the involvement of active cell membrane mechanism in the transference process
Lee et al. (2001)	8	Demonstrate that HPV-DNA can induce sperm cell apoptosis through the determination of p53 exons 5 and 8 integrity	Sperm apoptosis was detected trough Comet assay	Sperm apoptosis; (Integrity of exons 5 and 8 of the p53 gene); Exon 5 ratio      Exon 8 ratio; HPV 16 1.35±0.38     0.76±0.03; HPV 18 0.86±0.05      1.14±0.26; HPV 6b/11 1.26±0.21      1.06±0.15; HPV 31 0.91±0.20      0.91±0.01; HPV 33 0.98±0.06      1.19±0.18	The data suggest that different HPV types preferentially degrade different exons of important genes
Connelly et al. (2001) [21]	6	Demonstrate that HPV-DNA can induce sperm cell apoptosis	Sperm apoptosis was detected trough DNA disc chip assay	Percentage of sperm apoptosis *(Sperm head density: pixels, mean ± SEM): Control (DQA1) 167.3±2.4; HPV 16 125.9±3.8; HPV 18 163.2±3.3; HPV 31 154.0±3.5; HPV 33 166.7±3.7; HPV 6/11 168.0±2.8	(i) HPV types 16 and 31 might lead to failed embryonic development through sperm apoptosis
You et al. (2002) [38]	—	(i) Determine if the DNA of trophoblast were disrupted by the presence of HPV DNA	(i) Use of recombinant adeno-associated viruses (rAAV) to introduce the HPV-16 E6 and E7 oncogenes into trophoblasts	HPV-16 oncogene expression may lead to outright trophoblast death	(i) These changes to trophoblast might be responsible of trophoblast and placental alteration and could contribute to spontaneous abortions
Calinisan et al. (2002) [39]	—	(i) Determine if the DNA of blastocysts was disrupted by the presence of HPV DNA; (ii) Determine if the intensity of DNA damage was associated with the type of HPV	(i) Non-human (mouse) experimental study; (ii) Blastocysts infected with HPV-DNA 16, 18, 31, or 33; (iii) Blastocyst apoptosis was detected trough Comet assay	Mouse blastocysts apoptosis (DNA fragmentation); (mean pixel intensity ± 1 SD)§; HPV 16: 190.1±24.4^+; HPV 18: 180.1±21.7^+; HPV 31: 171.9±33.2^+; HPV 33: 179.5±12.0^+	(i) Only HPV-DNA 16 was associated with significant DNA fragmentation; (ii) The intensity of DNA damage was not linked to the specific type of HPV
Henneberg et al. (2006) [40]	—	(i) Assess the development of early embryos exposed to HPV DNA; (ii) Analyze the blastocyst hatching process after HPV exposure.	(i) Non-human (mouse) experimental study; (ii) Two-cell and 4–8-cell mouse embryos exposure to HPV-DNA 16 and 18	(i) HPV 16 and 18 inhibited two-cell embryo development but not 4–8-cell stage; (ii) 25.9% less blastocyst formed with HPV 16 exposure; (iii) 25.9–31.8% more degenerated embryos with HPV 16 exposure	(i) Demonstration of HPV embryo stage-specific effects on early development; (ii) HPV 16 was shown to decrease blastocyst formation; (iii) HPV 18 inhibited the blastocyst hatching process
Gomez et al. (2008) [41]	—	(i) Determine if HPV infection of extravillous trophoblast cells reduces cell invasion and induce apoptosis; (ii) Determine if placental infection is associated with adverse reproductive outcomes attributed to placental dysfunction	(i) Extravillous trophoblast cells transfected with the HPV-16 genome were detected; (ii) Apoptosis assay (Cell Death Detection ELISA); (iii) Invasion assays (Cell Invasion Assay Kit)	(i) Rates of apoptosis were 3- to 6- fold greater in transfected cells than in non-transfected cells†; (ii) Invasion of transfected cells through extracellular matrices was 25–58% lower than that of the controls^#	(i) HPV extravillous trophoblast infection induces cell death and may reduce placental invasion into the uterine wall; (ii) HPV infection may cause placental dysfunction and could be associated with adverse pregnancy outcomes, (such as preterm delivery
Foresta et al. (2011a) [25]	—	(i) HPV localization in sperm cell; (ii) Demonstrate that HPV-DNA transfected sperm cells can transfer viral genome into oocytes	(i) Fluorescence in situ hybridization for HPV (FISH); (ii) Hamster Egg Penetration Test (HEPT) with human sperm transfected with HPV E6/E7 plasmid	(i) HPV is localized at the equatorial region of sperm head through interaction between the HPV capsid protein L1 and syndecan-1; (ii) HPV transfected sperms are able to penetrate the oocyte; (iii) Viral genes are then activated and transcribed into the oocyte	(i) Sperm might function as vectors for HPV transfer into the oocytes

∗Lower head intensity (in pixels) represented greater DNA fragmentation. (The data were expressed as mean ± SEM) §Lower pixel intensity is associated with more DNA fragmentation.
⁺𝑃<0.05; ^†𝑃<0.01; ^#𝑃<0.001.